How did the Earth begin?
- How did the Earth begin? Around 4.6 billion years ago, neither the Earth nor any of the other planets existed. There was just this vast, dark, very hot cloud of gas and dust swirling around the newly formed Sun. Gradually, the......More
HOW BIG IS THE EARTH?
- Satellite measurements show it is 40,075 km around the equator and 12,757 km across. The diameter between the Pole is slightly less, by 43 km. ...More
HOW OLD IS THE EARTH?
- The Earth is about 4.6 billion years old. The oldest rock is about 3.8 billion years old. Scientists have also dated meteorites that have fallen from space, and must have formed at the same time as the Earth. ...More
WHAT IS THE EARTH MADE OF?
- The Earth has a core of iron and nickel, and a rocky crust made mostly of oxygen and silicon. In between is the soft, hot mantle of metal silicates, sulphides and oxides. ...More
WHAT SHAPE IS THE EARTH?
- The Earth is not quite a perfect sphere. Because it spins faster at the equator than at the Poles, Earth bulges at the equator. Scientists describe Earth's shape as "geoid", which simply means Earth-shaped! ...More
EXACTLY HOW LONG IS A YEAR?
- Every year the Earth travels once around the Sun. This epic journey covers a distance of 938,886,400 km and takes exactly 365.24 days, which gives us our calendar year of 365 days. To make up the extra 0.24 days, we add an extra day to our......More
WHAT SO SPECIAL ABOUT THE EARTH?
- The Earth is the only planet with temperatures at which liquid can exist on the surface and is the only planet with an atmosphere containing oxygen. Water and oxygen are both needed for life. ...More
WHY DOES THE EARTH SPIN?
- Earth spins because there is nothing to stop it spinning. The Sun's gravity keeps it in orbit. ...More
HOW LONG IS A DAY?
- A day is the time Earth takes to turn once. The stars move to the same place in the sky every 23 hours, 56 minutes and 4.09 seconds (the sidereal day). Our day (the solar day) is 24 hours, because Earth is moving around the Sun, and must turn an......More
WHO WAS COPERNICUS?
- In the 1500s, most people thought the Earth was fixed in the centre of the universe, with the Sun and the stars revolving around it. Nicolaus Copernicus (1473-1543) was the Polish astronomer who first suggested the Earth was moving around the......More
WHAT ARE THE MOON SEAS?
- The large, dark patches visible on the Moon's surface are called seas, but in fact they are not seas at all. They are huge plains formed by lava flowing from inside the Moon. ...More
WHAT IS MOONLIGHT?
- The Moon is by far the brightest thing in the night sky. But it has no light of its own. Moonlight is simply the Sun's light reflected off the white dust on the Moon's surface. ...More
WHAT IS A LUNAR ECLIPSE ?
- As the Moon goes around the Earth, sometimes it passes right into Earth's shadow, where sunlight is blocked off. This is a lunar eclipse. If you look at the Moon during this time, you can see the dark disc of the Earth's shadow creeping......More
WHO WERE THE FIRST MEN ON THE MOON?
- The first men on the Moon were Neil Armstrong and Buzz Aldrin of the US Apollo 11 mission. They landed on the Moon on July 20, 1969. As Armstrong set foot on the Moon, he said: "that’s one small step for (a) man, one giant leap for......More
WHAT IS THE MOON?
- The Moon is the Earth's natural satellite. It has circled around the Earth for at least four billion years. It is a rocky ball about a quarter of Earth's size and is held in its orbit by mutual gravitational attraction. Most scientists......More
WHAT IS A HARVEST MOON?
- The harvest moon is the full moon nearest the autumnal equinox (when night and day are of equal length).This moon hangs bright above the eastern horizon for several evenings, providing a good light for harvesters. ...More
WHY DOES THE MOON LOOK LIKE CHEESE?
- The moon looks like Swiss cheese because it is full of holes and can appear yellowish. The holes are craters in the surface created when it was bombarded by huge rocks early on in its history. ...More
WHY DOES THE SEA HAVE TIDES?
- The Moon's gravity draws the oceans into an oval around the Earth, creating a bulge of water on each side of the world. These bulges stay beneath the Moon as the Earth spins round and so seem to run around the world, making the tide rise and......More
WHAT IS A NEW MOON?
- The Moon appears to change shape during the month because, as it circles the Earth, we see its bright, sunny side from a different angle. At the new moon, the Moon lies between the Earth and the Sun, and we catch only a crescent-shaped glimpse of......More
WHAT IS THE SUN?
- The Sun is an average star, just like countless others in the universe. It formed from gas left behind after an earlier, much larger star blew up and now, in middle-age, burns yellow and fairly steadily - giving the Earth daylight and remarkably......More
WHAT IS A SOLAR ECLIPSE?
- A solar eclipse is when the Moon moves in between the Sun and the Earth, creating a shadow a few hundred kilometres wide on the Earth. ...More
HOW BIG IS THE SUN?
- The Sun is a small-to-medium-sized star 1,392,000 km in diameter. It weighs just under 2,000 trillion trillion tonnes. ...More
WHAT MAKES THE SUN BURN?
- The Sun gets its heat from nuclear fusion. Huge pressures deep inside the Sun force the nuclei (cores) of hydrogen atoms to fuse together to make helium atoms, releasing huge amounts of nuclear energy. ...More
WHAT IS THE SUN CROWN?
- The Sun's crown is its corona, its glowing white hot atmosphere seen only as a halo when the rest of the Sun's disc is blotted out by the Moon in a solar eclipse. ...More
WHAT IS THE SOLAR WIND?
- The solar wind is the stream of radioactive particles constantly blowing out from the Sun at hundreds of kilometres per second. The Earth is protected from the solar wind by its magnetic field, but at the Poles the solar wind interacts with......More
HOW OLD IS THE SUN?
- The Sun is a middle-aged star. It probably formed about 4.6 billion years ago. It will probably burn for another five billion years and then die in a blaze so bright that the Earth will be scorched right out of existence. ...More
WHAT ARE SUNSPOTS?
- Sunspots are dark blotches seen on the Sun's surface. They are thousands of kilometres across, and usually occur in pairs. They are dark because they are slightly less hot than the rest of the surface. As the Sun rotates, they slowly cross......More
HOW HOT IS THE SUN?
- The surface of the Sun is a phenomenal 5500 degree C, and would melt absolutely anything. But its core is thousands of times hotter at over 15 million degree C!...More
WHAT ARE SOLAR FLARES?
- Flares are eruptions from the Sun's surface that fountain into space with the energy of one million atom bombs for about five minutes. They are similar to solar prominences, the giant flame-like tongues of hot hydrogen that loop 32,000 km......More
WHAT ARE THE INNER PLANETS?
- The inner planets are the four planets in the solar system that are nearest to the Sun. These planets-Mercury-Venus, Earth and Mars- are small planets further out, which are made mostly of gas. Because they are made of rocks, they have a hard......More
WHY IS MARS RED?
- Mars is red because contains a high proportion of iron dust, and this has been oxidized in the carbon dioxide atmosphere. ...More
WHAT FRIGHTENING ABOUT MAR MOONS?
- One night American astronomer Asaph Hall got fed up with studying Mars and decided to go to But his domineering wife bullied him into staying up - and that night he discovered Mars's two moons. Mocking his fear of his wife. he named the moons......More
LIFE ON MARS?
- The Viking lenders of the 1970s found no trace of life. Then, in 1996, microscopic fossils of what might be mini-viruses were found in a rock from Mars. These turned out not to be signs of life after all. ...More
WHAT ARE SATURN RINGS?
- Saturn's rings are the planet's shining halo, first seen by Galileo Galilei (1564-1642), who invented the first simple telescope in 1609. The rings are made of countless billions of tiny chips of ice and dust, few bigger than a......More
HOW HEAVY IS SATURN?
- Saturn may be big, but because it is made largely of liquid hydrogen, it is also remarkably light, with a mass of 600 billion trillion tonnes. If you could find a big enough bath, it would float. ...More
HOW WINDY IS SATURN?
- Saturn's winds are even faster than Jupiter's and roar round the planet at up to 1,800 km/h. But Neptune's are even faster! ...More
WHAT IS THE CASSINI DIVISION?
- Saturn's rings occur in broad bands, referred to by the letters A to G. In 1675. the astronomer Cassini spotted a dark gap between rings A and B. This is now called the Cassini division, after him. ...More
HOW MANY MOONS HAS SATURN?
- Saturn has at least 18 moons, including Lapetus, which is dark on one side and light on the other. ...More
WHAT IS JUPITER RED SPOT?
- The Great Red Spot or GRS is a huge swirling storm in Jupiter's atmosphere. It is 26,000 km from east to west, and 14,000 km from north to south. ...More
HOW BIG IS JUPITER?
- Very big. Even though Jupiter is largely gas, it weighs 320 times as much as the Earth and is 142,984 km in diameter. ...More
COULD YOU LAND ON JUPITER?
- No. Even if your spaceship could withstand the enormous pressures, there is no surface to land on - the atmosphere merges unnoticeably into deep oceans of liquid hydrogen. ...More
WHAT ARE THE GIANT PLANETS MADE OF?
- Jupiter and Saturn are made largely of hydrogen and helium. On Jupiter, internal pressures are so great that most of the hydrogen is turned to metal. ...More
WHY ARE ASTRONOMERS EXCITED ABOUT TITAN?
- Saturn's moon Titan is very special because it is the only moon in the solar system with a dense atmosphere. ...More
HOW LONG DOES IT TAKE JUPITER TO ORBIT THE SUN?
- Jupiter takes 11 years and 3 14 days (by our Earth calendar) to complete its journey around the Sun. ...More
WHAT ARE THE GIANT PLANETS?
- Jupiter and Saturn, the fifth and sixth planets out from the Sun, are the giants of the solar system. Jupiter is twice as heavy as all the planets put together. Saturn is almost as big. Unlike the inner planets, they are both made largely of gas,......More
HOW FAST DOES JUPITER SPIN?
- Jupiter spins faster than any other planet. Despite its huge size, it turns right around in just 9 hours 55 minutes, which means the surface is moving at 45,000 km/h! ...More
WHAT ARE THE OUTER PLANETS?
- The outer planets are Uranus, Neptune and Pluto, and Pluto's companion Charon. Unlike the other planets, these were completely unknown to ancient astronomers. They are so far away, and so faint, that Uranus was discovered only in 1781,......More
WHAT STRANGE ABOUT URANUS?
- Unlike any of the other planets, Uranus does not spin on a slight tilt. Instead it is tilted right over and rolls around the Sun on its side, like a giant bowling ball. ...More
WHAT AN ASTEROID?
- Asteroids are the thousands of rocky lumps that circle round the Sun in a big band between Mars and Jupiter. The biggest, Ceres, is 640 km across. Most are much smaller. Over 5000 asteroids have been identified so far. ...More
WHO FOUND NEPTUNE?
- Two mathematicians, John Couch Adams in England and Urbain Ie Verrier in France, predicted where Neptune should be from the way its gravity disturbed Uranus's orbit. Johann Galle in Berlin spotted it on September 23, 1846. ...More
HOW LONG IS A YEAR ON NEPTUNE?
- Neptune is so far from the Sun - over 4,500 million km - that its orbit takes about I 65 Earth years. So one year on Neptune lasts 165 Earth years. ...More
WHAT IS A COMET?
- Comets are really just dirty iceballs. Normally, they circle the outer reaches of the solar system. But occasionally, one of them is drawn in towards the Sun. As it hurtles towards the Sun, it melts and a vast tail of gas is blown behind it by......More
HOW BIG IS PLUTO?
- Pluto is very small, which is why it was so hard to spot. It is five times smaller than the Earth - just 2,390 km across - and 500 times lighter. ...More
WHY IS NEPTUNE GREEN?
- Neptune appears greeny-blue because of the methane gas (a component of natural gas) in its atmosphere. ...More
WHAT IS A METEORITE?
- Meteorites are lumps of rock from space big enough to penetrate the Earth's atmosphere and reach the ground without burning up. ...More
HOW MANY STARS ARE THERE?
- It is hard to know how many stars there are in the universe - most are much too far away to see. But astronomers guess there are about 200 billion. ...More
WHY DO SOME STARS THROB ?
- The light from variable stars flares up and down. "Cepheid" are big young stars that pulsate over a few days or a few weeks. "RR Lyrae" variables are old yellow stars that vary over a few hours. ...More
HOW ARE STARS BORN?
- Stars are born when clumps of gas in space are drawn together by their own gravity, and the middle of the clump is squeezed so hard that temperatures reach 10 miliion degree C, so a nuclear fusion reaction starts. ...More
WHAT IS A STAR?
- Stars are gigantic glowing balls of gas, scattered throughout space. They burn for anything from a few million to tens of billions of years. The nearest star, apart from the Sun, is over 40 trillion km away. They are all so distant that we can......More
WHAT IS THE BIGGEST STAR?
- The biggest stars are the supergiants. Antares is 700 times as big as the Sun. There may be a star in the Epsilon system in the constellation of Auriga that is 1,860 million (3 miles billion km) across - 4,000 times as big as the Sun! ...More
WHAT ARE CONSTELLATIONS?
- Constellations are small patterns of stars in the sky, each with its own name. They help astronomers locate things in the night sky. ...More
HOW HOT IS A STAR?
- The surface temperature of the coolest stars is below 3,500°C; that of the hottest, brightest stars is over 40,000°c. ...More
WHERE ARE STARS BORN?
- Stretched throughout space are vast clouds of dust and gas called nebulae. These clouds are 99% hydrogen and helium with tiny amounts of other gases and minute quantities of icy, cosmic dust. Stars are born In the biggest of these nebulae, which......More
WHAT MAKES STARS GLOW?
- Stars glow because the enormous pressure deep inside generates nuclear fusion reactions in which hydrogen atoms are fused together, releasing huge quantities of energy. ...More
WHAT COLOUR ARE STARS?
- It depends how hot they are. The colour of medium sized stars varies along a band on a graph called the main sequence - from hot and bright blue-white stars to cool and dim red stars. ...More
WHAT MAKES STARS TWINKLE?
- Stars twinkle because the Earth's atmosphere is never still, and starlight twinkles as the air wavers. Light from the nearby planets is not distorted as much, so they don't twinkle. ...More
WHAT HAPPENS WHEN STARS DIE?
- Stars make energy by converting hydrogen into helium. When the hydrogen is used up they then use any other nuclear energy. Stars die when they exhaust these vast supplies of nuclear energy. They either blow up, shrink go cold, or become a black......More
WHAT IS A SUPERNOVA?
- A supernova is a gigantic explosion. It finishes off a supergiant star. For just a brief moment, the supernova flashes out with the brilliance of billions of suns. Supernovae are usually visible only through a telescope. But in 1987, for the......More
WHAT IS A RED GIANT?
- It is a huge, cool star, formed as surface gas on a medium-sized star near the end of its life swells up. ...More
WHAT IS A WHITE DWARF?
- White dwarfs are the small white stars formed as stars smaller than our Sun lose their surface gas altogether and shrink. ...More
WHAT IS A PULSAR?
- Pulsars are stars that flash out intense radio pulses every ten seconds or less as they spin rapidly. They are thought to be very dense dying stars called neutron stars. ...More
WHAT ARE THE OLDEST STARS?
- The oldest stars we know of are not stars at all, but simply look like them because they are very bright and very far away. These are "quasi-stellar radio objects", or quasars. Some are so far away that the light we see left them 13......More
WHAT ARE NEUTRON STARS?
- Neutron stars are all that remains of a supergiant star after a supernova. They are tiny, unimaginably dense stars that often become pulsars. ...More
HOW OLD ARE THE STARS?
- Stars are dying and being born all the time. Big, bright stars live for only ten million years. Medium-sized stars like our Sun live for ten billion years. ...More
WHAT IS RED SHIFT?
- When a galaxy is moving rapidly away from us, the waves of light become stretched out - that is, they become redder. The greater this red shift, the faster the galaxy is moving away from us....More
WHAT IS A LIGHT-YEAR?
- A light year is 9,460,000,000,000 km. This is the distance light can travel in a year, at its constant rate of 300,000 km per second. ...More
HOW FAR IS IT TO THE NEAREST STAR?
- The nearest star is Proxima Centauri, which is 4.3 light-years away, or 40 trillion km. ...More
HOW FAR AWAY IS THE SUN?
- The distance of the Sun from Earth varies between 91 and 94 million miles. Astronomers can measure the distance very accurately by bouncing radar waves off the planets. ...More
WHAT IS A PARSEC?
- A parsec is 3.26 light-years. Parsecs are parallax distances - distances worked out geometrically from slight shifts of a star's apparent position as the Earth moves around the Sun. ...More
HOW DID ASTRONOMERS FIRST ESTIMATE THE SUN\'S DISTANCE?
- In 1672, two astronomers, Cassini in France and Richer in Guiana, noted the exact position of Mars in the skies. They could work out how far away Mars is from the slight difference between their two measurements. Once they knew this, they could......More
WHAT IS THE FURTHEST OBJECT WE CAN SEE?
- The furthest objects we can see in space are quasars, which may be over 13 billion light-years away. ...More
ARE THE STARS GETTING FURTHER AWAY?
- Analysis of red shifts has shown us that every single galaxy is moving away from us. The further away the galaxy, the faster it is moving away from us. The most distant galaxies are receding at almost the speed of light. ...More
HOW DO ASTRONOMERS MEASURE DISTANCE?
- For nearby stars, they use parallax (see what is a parsed). With middle distance stars, they look for "standard candles", which are stars whose brightness they know. The dimmer it looks, compared to how bright it should look, the......More
HOW FAR AWAY IS THE MOON?
- At its nearest, the Moon is 356,517 km away from Earth; at its furthest, it is 406,711 km away. This is measured accurately by a laser beam bounced off mirrors left on the Moon's surface by Apollo astronauts and Soviet lunar probes. The......More
WHAT IS A BLACK HOLE?
- If a small is very dense, it may begin to shrink under the pull of its own gravity. As it shrinks, it becomes denser and denser and its gravity becomes more and more powerful-until it shrinks to a single tiny point of infinite density called......More
WHAT IS GRAVITY?
- Gravity is the mutual attraction between every single bit of matter in the universe. The more matter there is, and the closer it is, the stronger the attraction. A big, dense planet pulls much more than a small one, or one that is far away. The......More
HOW STRONG IS A PLANET\'S GRAVITY?
- The more massive the planet - that is the more matter it contains - the more powerful its gravity. Astronauts on the Moon could jump up high in heavy spacesuits, because the Moon is much smaller than the Earth and its gravity is weaker. ...More
HOW BIG IS A BLACK HOLE?
- The singularity at the heart of a black hole is infinitely small. The size of the hole around it depends on how much matter went into forming it. The black hole at the heart of our galaxy may be about the size of the solar system. ...More
WHAT ARE ORBITS?
- In space, many objects such as planets and moons continually circle around larger objects. An orbit is the path they take. This is usually elliptical rather than perfectly circular in shape. ...More
WHAT HAPPENS INSIDE A BLACK HOLE?
- Nothing that goes into a black hole comes out, and there is a point of no return called the event horizon. If you went beyond this you would be "spaghettified" - stretched long and thin until you were torn apart by the immense......More
HOW MANY BLACK HOLES ARE THERE?
- No one really knows. Because they trap light, they are hard to see. But there may be as manyas 100 million black holes in the Milky Way....More
WHAT DID NEWTON DISCOVER?
- The discoveries of Sir Isaac Newton (1642-1727) include the three fundamental laws of motion. He also discovered the forcecalled gravity, which holds the Moon in orbit around the Earth, andthe planets in orbit around the Sun....More
WHAT IS THE UNIVERSE MADE OF?
- The stars and clouds in space are made almost 100% of hydrogen and helium, the lightest and simplest elements of all. All the other elements are relatively rare. But some, such as carbon, oxygen, silicon, nitrogen and iron can form important......More
WHAT WAS THE FIRST ELEMENT?
- The first element to form was deuterium a heavy form of hydrogen. It formed within I.S minutes of the dawn of the universe. ...More
HOW WAS IRON MADE?
- Iron was forged in the heart of supergiant stars near the end of their lives, when the immense pressures there forced carbon atoms together. ...More
HOW WERE ATOMS MADE?
- Atoms of hydrogen and helium were made in the early days of the universe when quarks in the matter soup joined together. All other atoms were made as atoms were fused together by the intense heat and pressure inside stars. ...More
WHAT IS ANTI MATTER?
- Anti-matter is the mirror image of ordinary matter. If matter and anti-matter meet, they annihilate each other. Fortunately, there no anti-matter on Earth. ...More
WHAT HOLDS EVERYTHING TOGETHER?
- Everything in the universe is held together by four invisible forces. Two of them - gravity and electromagnetism - are familiar in everyday life. The other two - the strong and weak nuclear forces - are unfamiliar because they operate only inside......More
WHAT ARE PARTICLES?
- Particles are the basic units of matter that make up everyday objects. There are hundreds of kinds of particles, but all apart from the atom and molecule are too small to see, even with the most powerful microscope. ...More
WHAT IS THE SMALLEST KNOWN PARTICLE?
- The smallest particle inside the nucleus is the quark. It is less than 10-20 m across, which means a line of ten billion of them would be less than a metre long. ...More
WHAT IS A GALAXY?
- Our Sun is just one of a massive collection of 200 billion stars arranged in a shape like a fried egg, 100,000 light- years across. This collection is called the Galaxy, because we see it in the band of stars across the night sky called the Milky......More
WHAT ARE STAR CLUSTERS?
- Stars are rarely entirely alone within a galaxy. Most are concentrated in groups called clusters. Globular clusters are big and round. Galactic clusters are small and formless. ...More
HOW MANY GALAXIES ARE THERE?
- There are currently estimated to be about 125 billion galaxies in the universe - there may be many. many more than this. ...More
WHAT IS THE MILKY WAY?
- The Milky Way is a pale, blotchy, white band that stretches right across the night sky. From Earth you only get an edge-on view of the Milky Way. A powerful telescope shows it is made up of millions of stars. ...More
WHAT ARE DOUBLE STARS?
- Our Sun is alone in space. but many stars have one or more nearby companions. Double stars are called binaries. ...More
WHAT IS A SPIRAL GALAXY?
- A spiral galaxy is a galaxy that has spiraling arms of stars like a gigantic Catherine wheel. They trail because the galaxy is rotating. Our Galaxy is a spiral galaxy. ...More
WHAT IS THE BIGGEST THING IN THE UNIVERSE?
- The biggest structure in the universe is the Great Wall - a great sheet of galaxies 500 million light-years long and 16 million light-years thick. ...More
WHERE IS THE EARTH?
- The Earth is just over half way out along one of the spiral arms of the Galaxy. about 30,000 light-years from the centre. ...More
WHAT EXACTLY ARE NEBULAE?
- Nebulae are giant clouds of gas and dust spread throughout the galaxies. Some of them we see through telescopes because they shine faintly as they reflect starlight. With others, called dark nebulae, we see only inky black patches hiding the......More
WHAT WAS THERE BEFORE THE UNIVERSE?
- No one knows. Some people think there was an unimaginable ocean beyond space and time of potential universes continually bursting into life, or falling. Ours succeed ...More
WHAT WAS THE BIG BANG?
- In the beginning, all the universe was squeezed into an unimaginably small, hot, dense ball. The Big Bang was when this suddenly began to swell explosively, allowing first energy and matter, then atoms, gas clouds and galaxies to form. The......More
CAN WE SEE THE BIG BANG?
- Astronomers can see the galaxies hurtling away in all directions. They can also see the afterglow-low level microwave radiation coming at us from all over the sky, called the background radiation. ...More
HOW DO WE KNOW WHAT IT WAS LIKE?
- We know partly by mathematical calculations, and partly by experiments in huge machines called colliders and particle accelerators. These recreate conditions in the early universe by using magnets to accelerate particles to astonishing speeds in......More
WHAT WAS THE UNIVERSE LIKE AT THE BEGINNING?
- The early universe was very small, but it contained all the matter and energy in the universe today. It was a dense and chaotic soup of tiny particles and forces, and instead of the four forces scientists know today, there was just one super......More
What is inflation?
- Inflation was when dramatic expansion and cooling took place after the first second or so in the life of the universe, when space swelled up and cooled enormously. ...More
HOW DO WE KNOW THE UNIVERSE IS GETTING BIGGER?
- We can tell the universe is getting bigger because every galaxy is speeding away from us. Yet the galaxies themselves are not moving- the space in between them is stretching. ...More
HOW DID THE FIRST GALAXIES AND STARS FORM?
- They formed from lumps of clouds of hydrogen and helium, either as clumps broke up into smaller, more concentrated clumps, or as concentrations within the clumps drew together. ...More
HOW OLD IS THE UNIVERSE?
- We know that the universe is getting bigger at a certain rate by observing how fast distant galaxies are moving. By working out how long it took everything to expand to where it is now, we can wind the clock back to the time when the universe was......More
HOW DID LIFE BEGIN?
- Scientific experiments in the 1950s showed how lightning flashes might create amino acids, the basic chemicals of life, from the waters and gases of the early Earth. But no one knows how these chemicals joined up to become......More
WHAT IS LIFE MADE OF?
- Life is based on complex compounds of the element carbon, known as organic chemicals. Carbon compounds called amino acids link up to form proteins, and proteins form the complex chemicals that build and maintain living cells. ...More
HOW ARE WE LOOKING FOR EXTRA-TERRESTRIAL LIFE?
- Since possible fossils of microscopic life were found in Martian meteorite found on Earth in 1996, scientists have hunted for other signs of organisms in rocks from space. Robotic probes are currently searching for signs of life on Mars. ...More
IS THERE LIFE ON OTHER PLANETS?
- Organic chemicals are widespread, and the chances are that in such a large universe there are many planets, like Earth, suitable for nurturing life. But no one knows if life arose on Earth by a fantastic and unique chain of chance events, or......More
WHERE DID LIFE COME FROM?
- Most scientists think life on Earth began on Earth, in the oceans or in volcanic pools. But some think the Earth was seeded by micro- organisms from space. ...More
WHAT DOES AN ALIEN LOOK LIKE?
- At the moment, the only aliens we are likely to encounter are very, very small and look like viruses. ...More
WHAT IS SETI?
- SETI is the Search for Extra-Terrestrial Intelligence project, designed to continually scan radio signals from space and pick up any signs of intelligence. It looks for signals that have a pattern, but are not completely regular, like those from......More
ARE THERE ANY OTHER PLANETS LIKE EARTH?
- There is no other planet like Earth anywhere in the solar system. Recently, though, planets have been detected circling other stars in neighbouring galaxies. But they are too far away for us to know anything about them at all. ...More
WHY IS THE UNIVERSE LIKE IT IS?
- The amazing chance that life exists on Earth has made some scientists wonder if only a universe like ours could contain intelligent life. This is called the weak anthropic principle. Some go further and say that the universe is constructed in......More
WHAT IS DNA?
- Deoxyribonucleic acid, the most remarkable chemical in the universe, is the tiny molecule on which all life is based. It is shaped a bit like a long rope ladder, with two strands twisted together in a spiral, linked by "rungs" of four......More
HAVE HUMANS CHANGED OUR PLANET?
- Over the ages, humans have changed the face of the world we live in. They have chopped down forests and dammed rivers. They have grown new plants and killed wild animals. They have built big cities and roads. ...More
HAVE PEOPLE ALWAYS LIVED WHERE THEY DO NOW?
- During history many peoples have moved huge distances, or migrated. The Polynesians may have taken 2,500 years or more to sail across the Pacific Ocean and settle its islands. ...More
WHO ARE THE WORLD PEOPLES?
- Human beings who share the same history or language make up "a people" or "ethnic group". Sometimes many different peoples share a country. Over 120 peoples live in Tanzania, Africa. ...More
HOW DIFFERENT FORE WE FROM ONE ANOTHER?
- All human beings are basically the same, wherever they live. We may speak different languages and have different ideas. We may wear different clothes and eat different foods. Our parents may give us dark or pale skin, blue eyes or brown, or......More
HOW MANY PEOPLE LIVE IN THE WORLD?
- Billions! In 2000 there were about 6.1 billion human beings living on our planet. That's more than twice as many as 50 years ago. ...More
ROOM FOR EVERYBODY?
- Just about! But sometime in the future people may have to live in towns under the ocean or even on other planets, where they would need a special supply of air to stay alive. ...More
WHERE ARE THE MOST CROWDED PLACES IN THE WORLD?
- Tiny countries and large cities may house many millions of people. Bangladesh is one of the most crowded places in the world. There are over 900 people per square km. ...More
WHAT IS A CONTINENT?
- The big masses of land that make up the Earth's surface are called continents. The biggest continent of all is Asia, which is home to more than 3.5 billion people. ...More
WHICH COUNTRY HAS THE MOST PEOPLE?
- More people live in China than anywhere else in the world. They number about 1,300,000,000 and most live in the big cities of the east and the south. In the far west of China there are empty deserts and lonely mountains. ...More
WHY ARE SOME LANDS RICHER THAN OTHERS?
- Some lands have good soil, where crops can grow. Some have oil, which is worth a lot of money. But other countries have poor soil, little rain and no minerals. However hard people work there, they struggle to survive. ...More
WHERE DO PEOPLE LIVE?
- Humans live wherever they can find food and water, which they need to stay alive. Nobody at all lives in Antarctica, the icy southern wilderness. Scientists do visit bases there, so that they can study rocks, icebergs and penguins. The Sahara......More
ARE THERE MORE AND MORE PEOPLE?
- Every minute, perhaps 270 babies are born around the world. Imagine how they would cry if they were all put together! By the year 2050 there will probably be 9.3 billion people in the world. ...More
WHY DO COUNTRIES HAVE FLAGS?
- Flags can be seen flying from buildings and from boats. They show bold patterns and bright colours as they flutter in the wind. Many flags are badges or symbols of a nation, or of its regions. The designs on flags sometimes tell us about a......More
WHERE CAN YOU SEE ALL THE FLAGS OF THE UNITED NATIONS?
- Rows and rows of flags fly outside the headquarters of the United Nations in New York City, USA. Most of the world's countries belong to this organization, which tries to solve all kinds of problems around the world. ...More
DO ALL PEOPLES HAVE A COUNTRY THEY CAN CALL THEIR OWN?
- No, the ancient homelands of some peoples are divided up between other countries. The lands of the Kurdish people are split between many nations. ...More
WHAT IS A COUNTRY?
- A country is an area of land under the rule of a single government. A country may be vast, or very small. Its borders have to be agreed with neighbouring countries, although this does sometimes lead to arguments. Countries that rule themselves......More
WHICH COUNTRY FITS INSIDE A CITY?
- The world's smallest nation is an area within the city of Rome, in Italy. It is called Vatican City and is the headquarters of the Roman Catholic Church. Less than 1,000 people live there. ...More
HOW LONG DOES IT TAKE TO CROSS RUSSIA?
- It depends how you travel! These days, trains on the famous Trans-Siberian Railway take eight days from Moscow to the Pacific coast. ...More
HOW MANY INDEPENDENT COUNTRIES ARE THERE?
- There are about 190 independent countries in the world - the number changes from one year to the next. ...More
WHAT ARE COUNTIES AND STATES?
- If you look at the map of a country, you will see that it is divided up into smaller regions. These often have their own local laws and are known as states, provinces, counties or departments. ...More
WHICH IS THE BIGGEST COUNTRY IN THE WORLD?
- The gigantic Russian Federation takes up over 17 million sq km of the Earth's surface. It spreads into two continents, Europe and Asia, and its clocks are set at 12 different times. ...More
HOW MANY DEPENDENCIES ARE THERE IN THE WORLD?
- Around 65 of the world's nations are still ruled by other countries. They include many tiny islands in the Caribbean Sea and in the Atlantic and Pacific Oceans. ...More
HOW DOES ANYONE GET TO BE A KING OR A QUEEN?
- Normally you have to be a prince or princess, born into a royal family with a king and queen for your dad and mum. In the past, kings and queens were very powerful people. They could have their enemies thrown into some horrible dungeon and then......More
WHO RULES THE BIRDS?
- Traditionally the king or queen of England owns all the swans on the River Thames, except for those marked in a special ceremony that takes place each summer. ...More
HOW DO YOU RECOGNIZE KINGS AND QUEENS?
- For special ceremonies kings and queens wear traditional robes, and some wear crowns and carry symbols of royal power, such as golden scepters. The beaded crown and robes shown here were worn by traditional rulers of the Yoruba people, who live......More
WHAT IS A HEAD OF STATE?
- The most important person in a country is the head of state. This may be a king or a queen or an elected president. The head of state often rides in a big car with a flag on it. ...More
WHAT IS A REPUBLIC?
- It's a country that has no king or queen. France is a republic. Over 200 years ago the French king had his head chopped off, during a revolution. ...More
WHICH IS THE WORLD OLDEST PARLIAMENT?
- A parliament is a meeting place where new laws are discussed and approved. The oldest parliament is in Iceland. Called the All thing, it was started by Viking settlers in AD 930. ...More
WHAT ARE JANA-GANA-MANA AND THE STAR-SPANGLED BANNER?
- Both of them are national anthems or songs. The first tune is played to show respect to India, the second to the United States of America. National anthems are played at important occasions, such as the Olympic Games. ...More
WHERE DO JUDGES WEAR BIG WIGS?
- In Great Britain judges wear wigs, which were in fashion 250 years ago. This old costume is meant to show that the judge is not in court as a private person, but as someone who stands for the law of the land. ...More
WHICH IS THE WORLD OLDEST ROYAL FAMILY?
- The Japanese royal family has produced a long line of 125 reigning emperors over a period of thousands of years. ...More
WHAT IS A GOVERNMENT?
- The members of the government run the country. They pass new laws on everything from schools to hospitals and businesses. Countries where the people can choose their government by voting for a political party are called democracies. Some......More
WHERE IS THE BIGGEST GENERAL ELECTION?
- Over 275 million people are eligible to vote in general elections in India. They can cast their votes at anyone of more than a million Electronic Voting Machines set up all over the country. ...More
WHO INVENTED DEMOCRACY?
- The people of ancient Athens, in Greece, started the first democratic assembly nearly 2,500 years ago. It wasn't completely fair, as women and slaves weren't given the right to vote. ...More
HOW MANY LANGUAGES ARE SPOKEN TODAY?
- Around 6,000 languages are spoken in the world today. Some are spoken by very few people. Less than 500 people in Latvia speak a language called Liv. One African language, Bikya, could have only one surviving speaker. The world's most spoken......More
DO WE ALL READ LEFT TO RIGHT?
- The Arabic language is read right-to-left, and traditional Japanese top-to-bottom. ...More
COULD WE INVENT ONE LANGUAGE FOR ALL THE WORLD?
- It's already been done! A language called Esperanto was invented over 100 years ago. Only about 100,000 people have learned how to speak it. ...More
WHAT HAS MADE THE WORLD SHRINK?
- The planet hasn't really got smaller, it just seems that way. Today, telephones, emails and faxes make it possible to send messages around the world instantly. Once, letters were sent by ship and took many months to arrive. ...More
HOW DO WE TALK THROUGH SPACE?
- Satellites are machines sent into space to circle the Earth. They can pick up telephone, radio or television signals from one part of the world and beam them down to another. ...More
DO WE USE DIFFERENT WAYS OF WRITING?
- Many different kinds of writing have grown up around the world over the ages, using all sorts of lines and squiggles and little pictures. This book is printed in the Roman alphabet, which has 26 letters and is used for many of the world's......More
CAN WE TALK WITHOUT WORDS?
- People who are unable to hear or speak can sign with their hands. Various sign languages have been developed around the world, from China to the USA. ...More
DOES EVERYBODY IN ONE COUNTRY SPEAK THE SAME LANGUAGE?
- Not often. For example, families from all over the world have made their homes in London, the capital city of England. Their children mostly speak English at school, but at home may speak anyone of hundreds of other languages, from Turkish to......More
SHOULD I STAY OR SHOULD I GO?
- Movements of the head and hands can be a kind of language. Be careful! In some countries wagging the hand palm down means "come here", but in others it means "go away". Shaking the head can mean "yes" in some......More
WHAT IN A NAME?
- In Norway there's a village called A. In New Zealand there's a place called Taumatawhakatangihangakoa-uauotamateaturipukakapikim- aungahoronukupokaiwhenuaki-tanatahu. ...More
WHAT WAS THAT YOU WHISTLED?
- In some parts of Central America, Turkey and the Canary Islands, people worked out a way of communicating using whistles instead of words. ...More
WHY DO CHALETS HAVE BIG ROOFS?
- In the mountains of Switzerland, the wooden houses have broad roofs, designed for heavy falls of snow each winter. ...More
WHAT ARE HOUSES MADE FROM?
- Mud, stone, slate, boulders, bricks, branches, reeds, steel girders, sheets of iron, concrete, glass, timber, straw, turf, ice, bamboo, animal hides, cardboard boxes - you name it! All over the world people make use of whatever materials they can......More
WHY BUILD HOUSES WITH REEDS?
- It makes sense to use the nearest building material to hand. Tall reeds grow around Lake Titicaca in Peru - so the Indians who live there use them to build their beautiful houses. ...More
WHY DO PEOPLE LIVE UNDERGROUND?
- To stay cool! At Coober Pedy in Australia it is so hot that miners digging for opals built houses and even a church underground. ...More
WHAT ARE HOUSES LIKE IN THE ARCTIC?
- Today the Inuit people of Canada live in houses, huts and tents. Traditionally, they lived in igloos made out of blocks of snow. Igloos are still used today by Intuits on the move. ...More
WHERE DO THEY BUILD MUD HUTS?
- Thatched huts with walls of dried mud can still be seen in parts of Africa, such as Mali. They are cheap to build, cool to live in and often look beautiful too. ...More
WHY DO PEOPLE LIVE IN TENTS?
- In many parts of the world, there are people who do not live in the same place all year round. Instead, they follow their herds of sheep and goats from one desert oasis to another, or from lowland to mountain pastures. Such people are called......More
WHICH PEOPLE LIVE IN CARAVANS?
- Many of Europe's Gypsies live in caravans, moving from one campsite to another. The Gypsies, who are properly known as Roma, Sinti or Manush, arrived in Europe from India about 500 years ago. ...More
WHY WERE SKYSCRAPERS INVENTED?
- So that more people could fit into a small area of city. High-rise flats and offices were first built in Chicago, USA, about 120 years ago. By 1857 new lifts were saving people a very long climb upstairs! ...More
WHO BUILT THE FIRST CITIES?
- Towns first grew up when people stopped being hunter-gatherers and learned how to farm, which meant staying in one place. The first cities were built in southwest Asia. Catal Huyuk, in Turkey, was begun about 9,000 years ago. ...More
WHO LIVES AT THE ENDS OF THE EARTH?
- One of the world's most northerly settlements is Ny-Alesund, in the Arctic territory of Svalbard. The southernmost is Puerto Williams in Tierra del Fuego, Chile. ...More
WHICH IS THE WORLD OLDEST CAPITAL?
- Damascus, capital of Syria, has been lived in for about 4,500 years. ...More
WHY WAS LONDON BRIDGE FALLING DOWN?
- Children today still sing a rhyme that says "London Bridge is falling down". It's a very old song. The ancient bridge over the River Thames may have been pulled down by a Viking named Olaf the Stout nearly a thousand years......More
WHERE IS THE BIG APPLE?
- This is a nickname for New York City, in the eastern United States. Take a bite! ...More
WHAT PROBLEMS DO CITIES CAUSE?
- Cities can be exciting places to live in. They are full of hustle and bustle. But they often have big problems, too. So many people in one place need a lot of looking after. They need water and electricity and proper drains, fire engines,......More
WHICH CITY IS NAMED AFTER A GODDESS?
- Athens, the capital of Greece, shares its name with an ancient goddess named Athena. Her beautiful temple, the Parthenon, still towers over the modern city. It was built in the mid-5th century BC. ...More
WHERE IS THE WORLD TALLEST BUILDING?
- Until recently Petronas Towers in Kuala Lumpur, Malaysia, was the tallest building in the world at 452 m. However, Taipei 101 in Taiwan is now the tallest at 509 m. ...More
WHICH FAMOUS BUILDING LOOKS LIKE A SAILING BOAT?
- The Sydney Opera House dominates the harbour front of Sydney, Australia. Its roofs look like the sails of a big yacht. ...More
WHERE ARE THE BIGGEST CITIES IN THE WORLD?
- In Japan, where big cities have spread and joined up to make giant cities! Japan is made up of islands that have high mountains, so most people live on the flat strips of land around the coast. In order to grow, large cities have had to stretch......More
WHY ARE LANDMARKS USEFUL IN A CITY?
- Each city has eye-catching buildings and monuments. These can be helpful if you are trying to find your way around a city. Paris, in France, has the Eiffel Tower. Berlin, in Germany, has the Brandenburg Gate. ...More
WHICH COUNTRY HAS THREE CAPITAL?
- The most important city in a country is called the capital. South Africa has three of them! Cape Town is the legislative capital. Pretoria is the executive capital. Bloemfontein is the judicial capital. ...More
WHICH IS THE HIGHEST CITY?
- Lhasa stands 3,650 m above sea level. It is the capital city of Tibet, a region in the Himalaya Mountains that is governed by China. Tibet is sometimes called the "roof of the world". ...More
HOW DO YOU CROSS THE ARCTIC SNOW?
- You could always ride on a sled pulled by a team of dogs, as in the old days. But most people today ride snowmobiles, which are a bit like motorcycles with runners instead of wheels. ...More
WHERE CAN YOU CATCH A TRAIN INTO THE SKY?
- In the Andes mountains of South America. One track in Peru climbs to about 4,800 m above sea level. In Salta, Argentina, you can catch another high-rise locomotive, known as the "Train to the Clouds". ...More
WHO RIDES IN A CARAVAN?
- No, not one pulled by a car! This kind of caravan is a group of traders who cross the desert by camel. Camels can carry people across the Sahara for more than six days without needing a drink of water. ...More
WHERE WAS A HOT-AIR BALLOON FIRST FLOWN?
- The place was Paris, the capital of France, and the year was 1783. The passengers were, believe it or not, a sheep, a cock and a duck! Later, people tried out the balloon for themselves. ...More
WHICH IS THE WORLD\'S LONGEST ROAD?
- The Pan-American Highway. It starts at the top of the world, in the chilly American state of Alaska. It then heads on through Canada and the USA to the steamy forests of Central America. There is still a bit missing in the middle, but the road......More
WHERE ARE THE LONGEST TRUCKS?
- In the outback, the dusty back country of Australia, the roads are long and straight and pretty empty. Trucks can hitch on three or four giant trailers to form a "road train". ...More
WHAT IS A JUNK?
- It is a big wooden ship, traditionally built in China. Its big sails are strengthened by strips of bamboo. Junks aren't as common as they used to be, but they can still be seen on the South China coast. ...More
HOW CAN YOU TRAVEL UNDERNEATH THE ALPS?
- The Alps are snowy mountains that run across France, Italy, Switzerland and Austria. They soar to 4,807 m above sea level at Mont Blanc. In the days of ancient Rome, a general named Hannibal tried to cross the Alps with a number of war elephants.......More
WHERE IS THE WORLD BIGGEST AIRPORT?
- Riyadh airport in Saud Arabia is probably bigger than some countries. It covers many miles of the Arabian desert. ...More
WHERE ARE BOATS USED AS BUSES?
- In the beautiful Italian city of Venice, there are canals instead of roads. People travel from one part of the city to another by boa ...More
HOW DO WE KEEP WARM AND DRY?
- Since prehistoric times, people have used fur and animal skins to keep out the cold. In the Arctic today, the Inuit people still often wear traditional clothes made from fur, sealskin or caribou (reindeer) hide. The Saami people of northern......More
WHERE IS THE CAPITAL OF FASHION?
- Milan, London, New York and many other cities stage fantastic fashion shows each year. But Paris, in France, has been the centre of world fashion for hundreds of years. ...More
WHAT IS BATIK?
- This is a way of making pretty patterns on cloth. Wax is put on the fibre so that the dye sinks in only in certain places. This method was invented in Southeast Asia. ...More
DO PEOPLE STILL WEAR NATIONAL COSTUME?
- Most people today wear T-shirts and jeans, skirts or suits. Only on special occasions do they still put on traditional, regional costumes. In some countries, people still wear local dress every day. ...More
WHICH LADIES WEAR TALL LACE HATS?
- The Breton people of northwest France are proud of their costume, which they wear for special occasions. The men wear waistcoats and big black hats. The women wear lace caps, some of which are high and shaped like chimneys. ...More
HOW DO PEOPLE DRESS IN HOT COUNTRIES?
- In hot countries people protect their heads from the sun with all kinds of broad-brimmed hats, from the Mexican sombrero to the cone-shaped straw hats worn by farm workers in southern China and Vietnam. They may wear robes like the Arabs, or......More
WHO INVENTED SILK?
- The Chinese were the first people to make silk, from the cocoons of silkworms, thousands of years ago. Today silk may be used to make beautiful Indian wraps called saris and Japanese robes called kimonos. ...More
WHERE DO SOLDIERS WEAR SKIRTS?
- Guards of honour in the Greek army are called Evz6nes.Their uniform is based on the old- fashioned costume of the mountain peoples - a white kilt, woolen leggings and a cap with a tassel. ...More
WHO ARE THE TRUE CLOGGIES?
- A hundred years ago wooden shoes, or clogs, were worn in many parts of Europe. The most famous clogs were the Dutch ones, which are still often worn today by farmers and market traders in the Netherlands. ...More
WHO WEARS FEATHERS TO A SINGSING?
- A singsing is a big festival in Papua New Guinea. Men paint their faces and wear ornaments of bone and shell and long bird-of-paradise feathers. Traditional dress may include skirts made of leaves and grass. ...More
WHERE DO PANAMA HATS COME FROM?
- Actually, Panama hats were first made in Ecuador, where they were plaited from the leaves of the jipijapa palm. They were first exported, or shipped abroad, from Panama, which is why they are now called Panama hats. ...More
WHICH IS THE SWEETEST CROP OF ALL?
- Sugar cane is grown on many islands in the Caribbean region. In Barbados, the end of the cane harvest is marked by Crop over, a grand celebration with music, dancing and parades. ...More
WHO ARE THE GAUCHOS?
- The cowboys of the Pampas, which are the grasslands of Argentina. Once the Gauchos were famous for their wild way of life. Today they still round up the cattle on big ranches called estancias. ...More
HOW CAN BARREN DESERTS BE TURNED GREEN?
- Water can be piped into desert areas so that crops will grow there. But this irrigation can be very expensive and the water can also wash salts from the soil, making it difficult to grow plants. ...More
WHERE ARE THE WORLD BREAD BASKETS?
- Important wheat-producing areas of the world are called "bread baskets", because they provide us with the bread we eat each day. Wheat is a kind of grass, and so it grows best in areas that were once natural grasslands. These include......More
WHEREARE THE WORLD BIGGEST RANCHES?
- The world's biggest sheep and cattle stations are in the Australian outback. The best way to cross these lands is in a light aircraft. ...More
WHERE DO FARMERS GROW COCONUTS?
- Coconut fruits are big and green - the bit we buy in shops is just the brown seed inside. The white flesh inside the nut may be dried and sold as copra. Coconut palms grow best on the shores of the Indian and Pacific Oceans. ...More
WHICH WERE THE FIRST ALL-AMERICAN CROPS?
- About five hundred years ago, nobody in Europe had ever seen potatoes, maize or tomatoes. These important food crops were first developed by the peoples who lived in the Americas before European settlers arrived....More
WHERE DO FISHERMEN USE HOOPS AND SCOOPS?
- Giant fishing nets like those above can be lowered from the shore into lakes and seas. They are often used in China and India. ...More
WHAT IS A CASH CROP?
- It is any crop that is sold for money. Many small farmers around the world can only grow enough food to feed themselves and their families, without having any to spare. ...More
ARE THERE ENOUGH FISH IN THE SEA?
- Modern boats catch so many fish that in many places fish have become scarce. Some of the richest fishing grounds were off Newfoundland, in the North Atlantic. Fishing there has now been restricted until the numbers recover. ...More
WHAT GROWS BEST IN FLOODS AND SOGGY WET MUD?
- Rice keeps the world alive. Billions of people eat it every day, especially in Asia. Grains of rice are the seeds of a kind of grass that grows wild in wet river valleys. To cultivate it, farmers plant out the seedlings in flooded fields called......More
WHAT IS THE MOST DELICIOUS FOOD?
- Haute cuisine is French, and it means high-quality cooking. People all over the world love French food. But is it really the most delicious food in the world? Chinese cooking is also considered delicious. But really, which food we like or dislike......More
WHERE DO YOU BUY MILK BY THE KILO?
- In the Russian Arctic it is so cold in winter that milk is sold in frozen chunks rather than by the litre. ...More
WHO MAKES THE WORLD HOTTEST CURRIES?
- The people of southern India. A mouthwatering recipe might include fiery spices such as red chilli pepper and fresh hot green chillies, ginger, garlic, turmeric and curry leaves. ...More
WHO WROTE A POEM TO HIS HAGGIS?
- Robert Burns, Scotland's greatest poet, who lived in the 1700s. The haggis is a traditional dish from Scotland made of lamb's heart, liver and lungs, suet, onions and oatmeal, cooked inside - guess what - a sheep's stomach! ...More
HOW DO WE KEEP FOOD FRESH?
- Today, butter can be sent to Europe all the way from New Zealand - kept cool by refrigeration. The first-ever refrigerator ship was invented in 1876 to carry beef from Argentina. But how did people keep food fresh before that? The old methods......More
WHO INVENTED NOODLES?
- Which noodles came first - Italian spaghetti or Chinese chow mein? Some people say that the traveller Marco Polo brought the secret of noodle-making back to Italy from China in the Middle Ages. Others say the Romans were making pasta in Italy......More
CAN YOU EAT SEAWEED?
- Various seaweeds are eaten in Japan, and in South Wales seaweed makes up a dish called laver bread. A seaweed called carrageen moss is often used to thicken ice cream and milk puddings. ...More
WHAT IS JAMBALAYA?
- Rice, prawns and peppers, all in an amazing hot spicy sauce. Where is this served up? New Orleans, in the steamy southern United States. ...More
WHAT IS CAVIARE?
- One of the most expensive foods in the world. It is made of eggs from a fish called the sturgeon, which lives in lakes and rivers in Russia and other northern lands. ...More
HOW DO YOU EAT WITH CHOPSTICKS?
- Chopsticks are popular in China and Japan. They can be used by holding them between the thumb and fingers in one hand. ...More
WHAT IS YERBA MATE?
- It is a bitter but refreshing hot drink, made from the leaves of the Paraguay holly. It is sipped from a gourd (a kind of pumpkin shell) through a silver straw, and is very popular in Argentina. ...More
WHERE DO PEOPLE BUY THEIR FOOD?
- In India, most people buy fresh produce at street markets. Among the goods sold are okra, tomatoes, beans, cauliflower, mooli, peppers and lemons. Where do you buy your food? At a city store or in a traditional market? ...More
WHERE DO PEOPLE DO BUSINESS?
- In Nigeria, money changes hands every day in the busy street markets, where goods are laid out on the ground. Customers haggle about the price of goods. In England trading might take place in a big store, packed with shoppers. In Switzerland......More
WHAT CAN PEOPLE USE AS MONEY?
- Today, every country in the world uses coins and paper bank notes, although in many regions goods are swapped rather than bought. Over the ages all kinds of other things have been used as money around' the world - shells, stones, bead or......More
WHO MAKES THE MOST MONEY?
- The mint - that's the place where coins and banknotes are made. The United States treasury in Philadelphia produces billions of new coins each year. ...More
WHERE WERE BANK NOTES INVENTED?
- Paper money was first used in China a thousand years ago. ...More
WHO CATCHES SMUGGLERS?
- If you wish to take some goods from one country to another, you might have to pay a tax to the government. Customs officers may check your luggage to see that you are not sneaking in - or smuggling - illegal goods. ...More
WHAT ARE CURRENCIES?
- A currency is a money system, such as the Japanese yen, the US dollar, the Mongolian tugrik, or the Bhutan ngultrum. The exchange rate is what it costs to buy or sell one currency for another. ...More
WHY PRINT SO MANY STAMPS ON PITCAIRN?
- Although only 50 or so people live on Pitcairn Island, in the Pacific Ocean, the islanders print lots of stamps to sell to stamp collectors who will pay a lot of money because they are rare. ...More
WHERE IN THE WORLD ARE THERE FLOATING MARKETS?
- In Thailand and other parts of Southeast Asia, traders often sell vegetables, fruit, flowers and spices from small boats called sampans, which are moored along river banks and jetties. ...More
WHERE IS THE SILK ROAD?
- This is an ancient trading route stretching all the way from China through Central Asia to the Mediterranean Sea. Hundreds of years ago, silk, tea and spices were transported along this road to the West by camel and pony trains. ...More
WHERE DO PILGRIMS GO?
- Pilgrims are religious people who travel to holy places and shrines around the world. Muslims try to travel to the sacred city of Mecca, in Saudi Arabia, at least once in their lifetime. Hindus may travel to the city of Varanasi, in India, to......More
WHICH COUNTRY HAS THE MOST MUSLIMS?
- Indonesia is the largest Islamic country in the world, although some parts of it, such as the island of Bali, are mostly Hindu. ...More
WHAT IS THE TAO?
- It is said "dow" and it means "the way". It is the name given to the beliefs of the Chinese thinker Lao Zi, who lived about 2,500 years ago. Taoists believe in the harmony of the universe. ...More
WHO WAS CONFUCIUS?
- This is the English name given to the Chinese thinker Kong Fuzi, who lived at the same time as Lao Zi. His beliefs in an ordered society and respect for ancestors became very popular in China. ...More
WHAT ARE THE FIVE K S?
- Sikh men honour five religious traditions. Kesh is uncut hair, worn in a turban. They carry a Kangha or comb, a Kara or metal bangle, and a Kirpan or dagger. They wear an under- garment called a Kaccha. ...More
WHY DO PEOPLE FAST?
- In many religions people fast, or go without food, as part of their worship. If you visit a Muslim city such as Cairo or Algiers during Ramadan, the ninth month of the Islamic year, you will find that no food is served during daylight hours. Many......More
WHICH CITY IS HOLY TO THREE FAITHS?
- Jerusalem is a holy place for Jews, Muslims and Christians. Sacred sites include the Western Wall, the Dome of the Rock and the Church of the Holy Sepulchre. ...More
WHY IS MOUNT ETHOS IMPORTANT?
- This rocky headland in northern Greece is holy to Christians of the Eastern Orthodox faith. Monks have worshipped here since the Middle Ages. They wear beards, tall black hats and robes. ...More
WHERE DO YOUNG BOYS BECOME MONKS?
- In Myanmar a four year-old boy learns about the life of Buddha at a special ceremony. He is dressed as a rich prince and is then given the simple robes of a Buddhist monk. ...More
WHAT IS SHINTO?
- This is the ancient religion of Japan. At its holy shrines people pray for happiness and to honour their ancestors. Many Japanese people also follow Buddhist beliefs. ...More
WHICH MONKS COVER THEIR MOUTHS?
- Some monks of the Jain religion, in India, wear masks over their mouths. This is because they respect all living things and do not wish to harm or swallow even the tiniest insect that might fly into their mouths. ...More
WHAT ARE PARSIS?
- The Parsi religion began long ago in ancient Persia, now Iran. Many of its followers fled to India over a thousand years ago. They now live in India, Iran and Pakistan. ...More
WHAT IS HANUKKAH?
- This Jewish festival of light lasts eight days. Families light a new candle each day on a special candlestick called a menorah. Hanukkah celebrates the recapture of the temple in Jerusalem in ancient times. ...More
WHAT IS DIWALI?
- This is the time in the autumn when Hindus celebrate their new year and honour Lakshmi, goddess of good fortune. Candles are lit in windows and people give each other cards and presents. ...More
WHY DO PEOPLE LOVE TO DANCE?
- Dancing is a very dramatic way of expressing feelings of every kind. In Spain, passionate flamenco dancers stamp and click their fingers to guitar music. In England, morris dancers jingle bells tied to their legs and wave sticks. In Africa there......More
WHAT IS KABUKl?
- Kabuki is an exciting type of drama that became popular in Japan in the 1600s and may still be seen today. The actors wear splendid make-up and costumes. ...More
WHO DANCES A HAKA?
- In New Zealand, young Maori people have kept alive many of their traditional dances. The haka was a dance for warriors, to bring them strength to face the battles ahead. ...More
WHO MAKES PICTURES FROM SAND?
- The Navaho people of the southwestern United States make beautiful patterns using many different coloured sands. ...More
WHERE IS THE WORLD VERY OLDEST THEATRE?
- The oldest theatre building still in use today is probably the Teatro Olimpico, in Vicenza, Italy. It opened over four hundred years ago. But people were going to see plays long, long before that. In ancient Greece people went to see masked......More
WHERE IS STRATFORD?
- There are two famous Stratfords. Four hundred years ago, Stratford-upon- Avon, in England, was the home of the most famous playwright who has ever lived, William Shakespeare. The other Stratford, in Ontario, Canada, holds a drama festival every......More
WHO SINGS IN BEIJING?
- Beijing opera is a spectacular performance. Musicians clash cymbals and actors sing in high voices. They take the part of heroes and villains in ancient Chinese tales. Their faces are painted and they wear beautiful costumes decorated with......More
WHERE ARE THERE OVER 3 MILLION EXHIBITS OF ART?
- At St Petersburg in Russia, in an art gallery made up of two great buildings, the Hermitage and the Winter Palace. ...More
WHERE DO DRUMS TALK?
- The tama is nicknamed the "talking drum". Its tightness can be varied while it is being played, to make a strange throbbing sound. It is played in many places, including Senegal and the Gambia, in Africa. ...More
WHO PLAYS THE PANS?
- People in the Caribbean, at carnival time. The "pans" are steel drums, which can produce beautiful dance rhythms and melodies. ...More
WHERE DO THEY DANCE LIKE THE GODS?
- Kathakali is a kind of dance-drama performed in Kerala, southern India. Dancers in makeup that looks like a mask and gorgeous costumes act out ancient tales of gods and demons. ...More
WHO PAINTS PICTURES OF THE DREAMTIME?
- Australia's Aborigines look back to the Dreamtime, a magical age when the world was being formed, along with its animals and peoples. They paint wonderful pictures of it. ...More
WHERE DO DRAGONS DANCE?
- Wherever Chinese people get together to celebrate their New Year or Spring Festival. The lucky dragon weaves in and out of the streets, held up by the people crouching underneath its long body. Firecrackers are set off to scare away evil spirits.......More
WHERE IS THE BUN FESTIVAL?
- On the Chinese island of Cheung Chau, near Hong Kong, there is a big festival each May, with parades and religious ceremonies. During the celebrations people used to climb up huge towers made of buns. ...More
WHO REMEMBERS THE FIFTH OF NOVEMBER?
- People in England. The date recalls the capture of Guy Fawkes, who plotted to blow up the Houses of Parliament in London in 1605. The night is marked by fireworks and blazing bonfires, on top of which a home-made "Guy" is burned. ...More
WHERE IS NEW YEAR DAY ALWAYS WET?
- In Myanmar people celebrate the Buddhist New Year by splashing and spraying water over their friends! ...More
WHAT IS CARNIVAL?
- In ancient Rome there was a rowdy winter festival called saturnalia. People copied this idea in the Middle Ages. They feasted and had fun before the dark, cold days of Lent began, when Christians had to give up eating meat. People still celebrate......More
WHO WEARS GREEN ON ST PATRICK DAY?
- St Patrick's Day, on March 17, is the national day of Ireland. It is celebrated wherever Irish people have settled over the ages, from the United States to Australia. People wear green clothes or put green shamrock leaves in their......More
WHO RIDES TO THE FERIA?
- Each April the people of Seville, in Spain, ride on horseback to a grand fair on the banks of the River Guadalquivir. They wear traditional finery and dance all night. ...More
WHO GETS TO SIT IN THE LEADER CHAIR?
- In Turkey, April 23 is Children's Day. There are puppet shows, dances and a kite-flying competition. A child even gets the chance to sit at the desk of the country's prime minister! ...More
WHAT IS A POW-WOW?
- It means "a get-together". The Native American peoples of the United States and the First Nations of Canada meet up at pow- wows each year to celebrate their traditions with dance and music. ...More
WHO WALKED TO AMERICA?
- The first Americans! For millions of years, North and South America were cut off from the world by deep, stormy oceans. No one lived there. Then, during the last Ice Age, the oceans froze and parts of the sea bed were uncovered. A......More
WHAT DID THE FIRST AMERICANS CARRY WITH THEM?
- Everything they needed to survive: spears and nets for hunting; seeds, berries and dried meat to eat; furs to use as cloaks or blankets, and skin coverings for tents. ...More
WHO LIVED IN HUTS MADE OF BONES?
- Groups of nomads who lived on the plains of Eastern Europe about 15,000 years ago. They hunted woolly mammoths, ate the meat, and made shelters from the skin and bones....More
WHAT DID PREHISTORIC PEOPLE WEAR?
- In cold countries they were leggings and tunics made Jp6m furs and skin, sewn together using bone needles and sinews for thread. In hot countries, they wore skin loincloths, or nothing at all! ...More
DID PEOPLE LIVE IN CAVES?
- Yes, but not all the time. Nomadic hunter’s built-temporary shelters in cave entrances and used inner caves as stores. On hunting expeditions they camped in-shelters made of branches, brushwood, dry grass and bracken. ...More
WHEN DID PEOPLE START TO READ AND WRITE?
- About 6,000 years ago. The Sumerians (who lived in present-day Iraq) were the first people to invent writing. They used little picture-symbols scratched on to tablets of soft clay. Only specially trained scribes could read them. ...More
HOW DID MODERN HUMANS DEVELOP?
- Our distant ancestors are a group of animals known as primates. Primates first appeared on Earth about 50 million years ago, and looked rather like squirrels. Over millions of years they changed and grew, as the environment changed around them......More
HOW DO WE KNOW ABOUT APES WHO LIVED MILLIONS OF YEARS AGO?
- From fossil remains. Fossils are made when chemicals in the soil soak into dead bodies and turn the bones to stone. After many years, the soil turns into rock with fossils hidden inside. ...More
WHEN DID PEOPLE START TO LIVE IN TOWNS?
- Jericho in Jordan (built about 10,000 years ago) and Catal Huyuk in Turkey (built about 9,000 years ago) were the world's first big towns. They were centres of trade and craftwork, surrounded by strong walls. ...More
WHAT WERE THE FIRST HOUSES LIKE?
- Small, singles-storey and made of sun-dried mud. They were built in Middle Eastern lands about 11,000 years ago. The first villages were built close to streams and ponds, to ensure a steady water supply. ...More
WHO WERE THE NEANDERTHALS?
- A type of human who lived in Europe and Asia from about 200,000 to 35,000 years ago. Neanderthals were short and stocky with low, ridged brows. They died out (no one knows why) and were replaced by modern humans, who originated in Africa. ...More
WHY WERE THE PYRAMIDS BUILT?
- The pyramids are huge monumental tombs for pharaohs and nobility. The Egyptians believed that dead people's spirits could live on after death if their bodies were carefully preserved. It was specially important to preserve the bodies of dead......More
WHERE ARE THE PYRAMIDS?
- In Egypt, in North Africa. They stand on the west bank of the River Nile. The Egyptians believed this was the land of the dead, because the Sun set there. They built their homes on the east bank of the river, the land of sunrise and living......More
HOW OLD ARE THE PYRAMIDS?
- The first step pyramid was built between 2630 and 2511 BC. Before then, people were buried under flat-topped mounds, called "mastabas", and in pyramids with stepped sides. The last pyramid was built about 1530 BC. ...More
WHY WAS THE RIVER NILE SO IMPORTANT?
- Because Egypt got hardly any rain. But every year the Nile flooded the fields along its banks, bringing fresh water and rich black silt, which helped crops grow. Farmers dug irrigation channels to carry water to distant fields. ...More
HOW WERE CORPSES MUMMIFIED?
- Making a mummy was a complicated and expensive process. First, soft, internal organs were removed, then the body was packed in chemicals and left to dry out. Finally, it was wrapped in resin-soaked linen bandages, and placed in a beautifully......More
HOW WAS A PYRAMID BUILT?
- By man-power! Thousands of labourers worked in the hot sun to clear the site, lay the foundations, drag building stone from the quarry, and lift it into place. Most of the labourers were ordinary farmers, who worked as builders to pay their......More
WHAT WERE EGYPTIAN HOUSES LIKE?
- Small and simple, with flat roofs that served as extra rooms and courtyards where people worked. Rich people's homes were large and richly decorated, with fine furniture, gardens and pools. ...More
HOW MANY DIFFERENT BOATS MIGHT YOU HAVE SEEN ON THE NILE?
- Rafts made from papyrus reed, flat- bottomed punts, big, heavy cargo boats, splendid royal barges, and funeral boats carrying bodies across the river to pyramid tombs. ...More
WHY DID EGYPTIANS TREASURE SCARABS?
- Scarabs (beetles) collect animal dung and roll it into little balls. To the Egyptians, these dung balls looked like the life-giving Sun, so they hoped that scarabs would bring them long life. ...More
WHAT ARE THE PYRAMIDS MADE OF?
- Of hard, smooth limestone. Top quality stone was used for the outer casing; poor quality stone and rubble were used for the inner core....More
WHY DID THE GREEKS BUILD SO MANY TEMPLES?
- Because they worshipped so many different goddesses and gods! The Greeks believed each god and goddess needed a home where their spirit could live. So they built splendid temples to house them, with beautiful statues inside. Each god and goddess......More
WHY DID GREEK TEMPLES HAVE SO MANY COLUMNS?
- It may have been copied from ancient Greek royal palaces, which had lots of wooden pillars to hold up the roof....More
WHAT WERE THE ORIGINAL OLYMPIC SPORTS?
- At first, running was the only sport. Later, boxing, wrestling, chariot races, horse races and pentathlon (running, wrestling, long-jump, discus and javelin) were added. ...More
WHAT WERE GREEK WARSHIPS LIKE?
- Long, narrow and fast. Galleys called Triremes were powered by 170 oarsmen and huge sails. Sea battles were fought by ships smashing into one another, or by sailing close enough for men to jump across and fight on deck with swords and......More
DID THE GREEKS INVENT MONEY?
- No. The first coins were made in Lydia (part of present-day Turkey) about 600 BC. But the Greeks soon copied the Lydians and made coins of their own. ...More
COULD WOMEN TAKE PART IN THE OLYMPIC GAMES?
- No. And only the priestess of Demeter was allowed to attend. But once every four years, there were special games for women only. They were held in honour of Hera, wife of the god Zeus. ...More
DID THE GREEKS GO TO WAR?
- Yes. In 490 BC and 479 BC, the Greeks defeated Persian invaders, on land and at sea. From 431 BC to 362 Be, there were many civil wars. In 338 BC, Greece was conquered by the Macedonians, and Greek power ended. ...More
WHAT TOOK PLACE OUTSIDE TEMPLES?
- Sacrifices. Animals and birds were killed and burnt on altars outside temples as offerings to the gods. People also made offerings of wine, called "libations". ...More
WHO WERE THE BARBARIANS?
- Foreigners - people who did not speak Greek. The Greeks thought their words sounded like "baa, baa". ...More
WERE THERE GAMES IN OTHER GREEK CITIES?
- Yes. Sports and games were popular all over ancient Greece. ...More
WHAT WERE GREEK COINS MADE OF?
- Silver and gold. They were decorated with symbols of the cities where they were made, or with portraits of heroes and gods. ...More
WHY DID HADRIAN BUILD A WALL?
- To mark the frontiers of the Roman Empire and guard them from attack. It ran from coast to coast across the north of Britain. Roman emperor Hadrian (ruled AD 117-138) made many visits to frontier provinces, such as England, to inspect the......More
HOW LONG DID ROMAN POWER LAST?
- The Romans Empire lasted from 31 BC to AD 476, when the last Emperor, Romulus Augustulus, was deposed. ...More
WHY DID THE ROMANS SPEND SO LONG IN THE BATH?
- Because Roman baths were great places to relax and meet your friends. Most big towns had public bath-houses, with steam baths, hot and cold swimming pools, sports facilities and well trained slaves giving massages and beauty treatments. ...More
HOW ELSE DID THE ROMANS RELAX?
- By eating and drinking in taverns, gambling, going to the theatre, and watching chariot races and gladiator fights. ...More
WERE THE ROMANS EXPERT ENGINEERS?
- Yes, among the best in the world! They built roads, bridges, aqueducts (raised channels to carry water), long networks of drains and sewers, and the first-ever blocks of flats. ...More
WHO WANTED TO RULE THE WORLD?
- About 400 BC the Romans set out to conquer their Italian neighbours. By 272 BC they controlled all of Italy, but they didn't stop there! After defeating their rivals in Carthage (Northwest Africa), they invaded lands all around the......More
WHO ATTACKED ROME WITH ELEPHANTS?
- General Hannibal, leader of the Carthaginians, who lived in North Africa. In 218 BC he led a large army, including war- elephants, through Spain and across the Alps to attack Rome. ...More
DID THE ROMANS HAVE CENTRAL HEATING?
- Yes. They invented a system called the "hypocaust". Hot air, heated by a wood- burning furnace, was circulated through brick- lined pipes underneath the floor. ...More
WHO JOINED THE ROMAN ARMY?
- By 200 BC all able-bodied men between the ages of 17 and 46 were conscripted to join the Roman army. Roman citizens became legionary (regular) soldiers. Men from other nations enrolled as auxiliary (helper) troops. ...More
WHAT DID ROMAN CENTURIONS WEAR?
- Centurions were army officers. They dressed for parade in a decorated metal breastplate and a helmet topped with a crest of horsehair. They also wore shin guards, called greaves. ...More
WHERE DID ROMAN SOLDIERS LIVE?
- In goatskin tents, while on the march, or in big barrack blocks inside strongly built forts. Groups of ten ordinary soldiers shared a single room, fitted with bunk beds. Centurions (officers) had a room of their own, or shared with their wife and......More
HOW LONG DID ROMAN SOLDIERS SERVE?
- For about 25 years. After that, they retired. They were given a lump sum of money, or a pension, and a certificate recording their service. ...More
WHO WERE THE RAIDERS FROM THE SEA?
- Vikings from Norway, Denmark and Sweden! Warriors who terrorized the people of Europe. The Vikings made raids from Scotland to Italy, killing, burning and carrying away all they could. It was hard to make a living in the cold Viking homelands, so......More
WHY DID THE VIKINGS COMB THEIR BEARDS?
- Because they wanted to look good enough to attract girlfriends! At home, all Viking people liked to look good and keep clean. They combed their hair and took sauna baths in steam produced by pouring water over red- hot stones. Viking men and......More
DID THE VIKINGS REACH AMERICA?
- Yes, around 1000 AD. A bold adventurer named Leif Ericsson sailed westwards from Greenland until he reached 'Vinland' (present-day Newfoundland). He built a farmstead there, but quarreled with the local people, and decided to return......More
WHAT WERE VIKING SHIPS MADE OF?
- Narrow, flexible strips of wood, fixed to a solid wooden backbone called a keel. Viking warships were long and narrow, and could sail very fast. They were powered by men rowing, or by the wind trapped in big square sails. ...More
WERE THE VIKINGS GOOD SAILORS?
- Yes. They sailed for thousands of miles across the icy northern oceans in open wooden boats, known as longboats. They learned how to navigate by observing the sun and the stars. ...More
WHAT DID THE VIKINGS SEIZE ON THEIR RAIDS?
- All kinds of treasure. Churches were a favourite target for attack, because they were full of gold crosses and holy books covered with jewels. The Vikings also attacked farms and villages, and kidnapped the people to sell as slaves. ...More
WHEN WERE THE VIKINGS POWERFUL?
- Viking raiders first sailed south to attack the rest of Europe about AD 800. They continued raiding until about AD 1100....More
WHO LED THE VIKINGS ON THEIR RAIDS?
- Usually, the most powerful people in Viking society. But sometimes, Viking raiders were led by wild law-breakers, who had been expelled from their local community for fighting and causing trouble. ...More
WHO HELPED VIKING RAIDERS AND SETTLERS?
- The Vikings prayed to many different gods. Thor sent thunder and protected craftsmen. Odin was the god of wisdom and war. Kindly goddess Freya gave peace and fruitful crops. ...More
WHERE WERE THE VIKING HOMELANDS?
- The countries we call Scandinavia today: Norway, Sweden and Denmark. The word Viking comes from the old Scandinavian word vik, which means a narrow bay beside the sea. That's where the Vikings lived, ready to set off on raids. ...More
WHO CLIMBED UP STAIRWAYS TO GAZE AT THE STARS?
- Priests of the Maya civilization, which was powerful in Central America between 200 and 900 AD. They built huge, stepped pyramids, with temples and observatories at the top. The Mayans were expert astronomers and mathematicians. They worked out......More
WHO WERE THE INCAS?
- A people who lived in the Andes mountains of South America (part of present-day Peru). They ruled a mighty empire from early 15th century to early 16th century AD. ...More
WHAT WERE MAYAN PALACES MADE OF?
- Great slabs of stone, covered with a layer of plaster, then decorated with pictures of gods and kings. Mayan temples were built in the same way, but were often painted bright red. ...More
WHAT WAS A HUACA?
- An Inca holy object or place, or the spirit embodied in that object or place. Inca people made regular offerings to huacas, to bring good luck. Rich nobles left food or clothes. Poor people left blades of grass, drops of water, or just an......More
WHO WERE THE AZTECS?
- The Aztecs were wandering hunters who arrived in Mexico about AD 1200. They fought against the people already living there, built a huge city on an island in a marshy lake, and soon grew rich and strong. ...More
WHY WERE LLAMAS SO IMPORTANT?
- Because they could survive in the Incas mountain homeland, over 3,000 m above sea level. It is cold and windy there, and few plants grow. The Incas wove cloth and blankets from llama wool, and used llamas to carry heavy loads up steep mountain......More
WHO WROTE IN PICTURES?
- Mayan and Aztec scribes. The Mayans used a system of picture symbols called glyphs. Mayans and Aztecs both wrote in stitched books, called codexes, using paper made from fig-tree bark. ...More
WHO WAS THE GREAT FEATHERED SERPENT?
- An important Aztec god, whose name was Quetzalcoatl. The Aztecs believed that one day, he would visit their homeland and bring the world to an end. Quetzalcoatl was portrayed in many Aztec drawings and sculptures, and was worshipped by many other......More
WHO FOUGHT THE FLOWERY WARS?
- Fierce Aztec soldiers, armed with bows and arrows, knives and clubs. During the 15th and early 16th centuries, they fought against other tribes who lived in Mexico, in battles called the Flowery Wars. The Aztecs believed that the blood of their......More
HOW DID THE INCAS RECORD EVENTS?
- On bundles of knotted string, called quip us. The pattern of knots formed a secret code, which no one knows how to read today. ...More
WHO INVENTED CHOCOLATE?
- Aztec cooks. They made a bitter, frothy chocolate drink from ground-up cocoa beans and honey, flavoured with spices. The Aztec name for this drink was "xocoatl". ...More
WHO WAS THE SON OF THE SUN?
- The Inca ruler, a king who was worshipped and feared. The Inca people believed he was descended from Inti, the Sun god. The greatest Inca leader was Puchacuti Yupanqui (ruled 1438-1471), who conquered many neighbouring lands. ...More
HOW DID THE MAYAS, AZTECS AND INCAS LOSE THEIR POWER?
- They were conquered by soldiers from Spain, who arrived in American in the early 16th century, looking for treasure especially gold....More
WHAT WERE SHIPS OF THE DESERT?
- Camels belonging to travelling merchants who lived in Arabia. They were the only animals that could survive long enough without food and water to make exhausting journeys across the hot, dry desert, laden with valuable goods to sell. They stored......More
WHAT IS ISLAM?
- The religious faith taught by the Prophet Muhammad. People who follow the faith of Islam are called Muslims. ...More
WHO LIVED IN A CIRCULAR CITY?
- The citizens of Baghdad, which was founded in AD 762 by the caliph (ruler) al-Mansur. He employed builders and architects to create a huge circular city, surrounded by strong walls. His royal palace was at the centre, with government offices and......More
WHERE WAS THE MUSLIM WORLD?
- From about AD 700 to 1200, the Muslim world included southern Spain, North Africa, northwest India, Central Asia and almost all the Middle East. It was ruled by Muslim princes and governed by Muslim laws. The scientists and scholars of the Muslim......More
WHERE DID MUSLIM TRADERS SAIL?
- All round the Mediterranean, down the east coast of Africa, across the Indian Ocean and on to Indonesia. They traded silver, glass and perfumes for cloth, slaves, herbs and spices. ...More
WHO WERE THE MONGOLS?
- Nomads who roamed over the vast plains of Central Asia, tending their horses, sheep and goats. They lived in felt tents, called yurts. ...More
WHO INVENTED ASTROLABES?
- Muslim scientists who lived and worked in the Middle East, probably about AD 500. Astrolabes were scientific instruments that helped sailors find their position when they were out of sight of land. They worked by measuring the height of the Sun......More
WHEN DID THE MONGOLS ATTACK?
- In AD 1206, all the separate Mongol tribes united under a warlike leader, called Temujin. He took the title Genghis Khan (supreme ruler) and set out to conquer the world. His grandson, Hulegu, destroyed Baghdad in 1258. The Mongol Empire reached......More
WHERE IS THIS SPIRAL TOWER?
- At Samarra, in present-day Iraq. It is part of a mosque, built for the caliphs of Baghdad in about AD 848. By this time, there were Islamic mosques from Afghanistan in the east to Spain in the west. ...More
WHO WAS THE PROPHET MUHAMMAD?
- A religious leader who lived in Arabia from AD 570 to 632. He taught people to worship Allah (God). Muhammad reported that he had received many revelations (messages) from God about how to lead a good life. These were written down in a holy book......More
WHAT WERE THE CRUSADES?
- A series of wars fought between Christian and Muslim soldiers for control of the area around Jerusalem (in present-day Israel), which was holy to Muslims, Christians and Jews. The Crusades began in 1095, when a Christian army attacked. They ended......More
WHAT MADE CHINA SO PROSPEROUS?
- The inventions of chinese farmers and engineers made the land productive, and this made China wealthy. In the Middle Ages, the Chinese made spectacular strides in agriculture. They dug networks of irrigation channels to bring water to the rice......More
WHO VALUED HONOUR MORE THAN LIFE?
- Japanese warriors, called samurai, who were powerful from around the 12th century. They were taught to fight according to a strict code of honour. They believed it was better to commit suicide rather than face defeat. ...More
WHAT WAS CHINA BEST-KEPT SECRET?
- How to make silk. For centuries, no one else knew how. Chinese women fed silk- moth grubs on mulberry leaves, and the grubs spun thread and wrapped themselves in it, to make cocoons. Workers steamed the cocoons to kill the grubs, unwound the......More
HOW DID CHINA GET ITS NAME?
- From the Qin (pronounced Chin) dynasty, the first dynasty to rule over a united China. Founded by Qin Shi Huangd, it lasted from 221 to 206 BC. It was responsible for the standardization of Chinese script, weights and measures and the......More
WHERE DID THE SILK ROAD RUN?
- From rich Chinese cities, through the mountains of Central Asia to trading ports in the Middle East and around the Mediterranean Sea. European merchants travelled for years along the Silk Road to bring back valuable goods, especially silk and......More
WHERE WAS THE MIDDLE KINGDOM?
- The chinese believed their country to be at the very centre of the world, which is why they called it the Middle Kingdom. Certainly, for many centuries, China was one of the largest, richest and most advanced civilizations anywhere on Earth.......More
WHEN WAS THE WORLD FIRST BOOK PRINTED?
- No one knows for certain, but it was probably between AD 600 and 800, in China. The world's oldest surviving book is "The Diamond Surra", a collection of religious texts, also printed in China, in AD 868. ...More
WHERE DID THE SILK ROAD RUN?
- From rich Chinese cities, through the mountain of Central Asia to trading ports in the Middle East and around the Mediterranean Sea. European merchants travelled for years along the Silk Road to bring back valuable goods, especially silk and......More
WHO WROTE ONE OF THE WORLD FIRST NOVELS?
- Shikibu Murasaki, who lived at the elegant, cultured Japanese court about AD 978 to 1014. Japanese nobles loved music, poetry, painting, graceful buildings and exquisite gardens. They lived shut away from ordinary people, who had harsh, rough......More
WHICH RULERS CLAIMED DESCENT FROM THE SUN GODDESS?
- The emperors of Japan. The first Japanese emperor lived about 660 BC; his descendants ruled until AD 1192. After that, shoguns (army generals) ran the government leaving the emperors with only religious and ceremonial powers. ...More
WHO MADE LAWS ABOUT CARTWHEELS?
- Qin Shi Huangdi, the first Chinese emperor, who united the country, made strict new laws, reformed the coinage and burned all books he disagreed with. He ruled from 221 to 206 BC, and was buried with 6,000 terracotta warriors guarding his tomb.......More
WHO DID BATTLE IN METAL SUITS?
- Kings, lords and knights who lived in Europe during the Middle Ages. In those days, men from noble families were brought up to fight and lead soldiers into battle. It was their duty, according to law. About AD 1000, knights wore simple chain-mail......More
WHEN WERE THE MIDDLE AGES?
- From the collapse of the Roman Empire, around AD 500, to the Renaissance in about AD 1500. ...More
WHAT WAS A KNIGHT MOST VALUABLE POSSESSION?
- Probably a war horse. Keeping a war horse demanded a lot of money and time. ...More
WHAT JOB WAS FIT FOR A LADY?
- When knights went into battle, their ladies ran the castle. They supervised the household and discussed business and politics with important guests. Some women also fought to defend their castles against attack. ...More
WHICH RUSSIAN TSAR WAS TERRIBLE?
- Ivan IV, who became Tsar in 1533, when he was only three years old. He was clever but ruthless, and killed everyone who opposed him. He conquered many places, including Livonia, and passed laws turning all the peasants into serfs, who were not......More
WHO FARMED LAND THEY DID NOT OWN?
- Poor peasant families. Under medieval law, all land belonged to the king, or to rich nobles. The peasants lived in little cottages in return for rent or for work on their land. ...More
WHAT WAS THE ANCIEN REGIME?
- This is French for "old order" and describes the government of France in the 1700s, when the king ruled without a parliament, supported by the Church and rich nobles. The Ancien Regime was overthrown by the French Revolution of 1789,......More
WHICH FRENCH KING LOST HIS HEAD?
- King Louis XVI. In 1793 he was executed by guillotine, along with thousands of nobles. ...More
WHO BUILT CASTLES AND CATHEDRALS?
- Many people, including kings, queens and rich nobles. The first castles were just rough wooden forts. Later, they were built of stone, and became impressive homes. Cathedrals were very big churches, in cities or towns. Master-craftsmen built them......More
WHO WAS THE VIRGIN QUEEN?
- Elizabeth I of England, who reigned from 1558 to 1603, at a time when many people believed that women were too weak to rule. Elizabeth proved them wrong. Under her leadership, England grew stronger. She never married and ruled alone. ...More
WHO PRAYED THE DAY AWAY?
- Monks and nuns spent much of their lives at prayer. They promised never to marry and devoted their lives to God. ...More
WHO SWAPPED SALT FOR SANDALWOOD AND GOLD?
- Merchants from the north coast of Africa. They travelled across the Sahara Desert to trade with people living in the West African kingdoms of Ghana, Mali and Songhay, which were powerful from about AD 700 to 1600. Flakes of gold were found among......More
WHO BUILT HIS WIFE A BEAUTIFUL TOMB?
- Mughal emperor Shah Jehan (ruled 1628-1658). He was so sad when his wife Mumtaz Mahal died that he built a lovely tomb for her, called the Taj Mahal. It is made of pure white marble decorated with gold and semi-precious stones. ...More
WHO WAS THE GREAT SHE ELEPHANT?
- This was a title of respect given to the Queen Mother in southern African kingdoms, now part of present-day Botswana and neighbouring lands. It honoured her status as mother of the king, and showed her power. ...More
WHO LIVED IN A ROSE-COVERED PALACE?
- The rulers of Vijayanagar, a kingdom in southern India. Their royal palace was covered in carvings of roses and lotus flowers, and surrounded by lakes and gardens. Vijayanagar was conquered by the Mughals in 1565. ...More
WHERE DID DHOWS SAIL TO TRADE?
- Dhows were ships built for rich merchants living in trading ports like Kilwa, in East Africa. They sailed to the Red Sea and the Persian Gulf to buy pearls and perfumes, across the Indian Ocean to India to buy silks and jewels, and to Malaysia......More
WHO WAS THE TIGER KING?
- Tippu Sultan, king of the southern Indian state of Mysore from 1785 to 1799. Tippu means tiger, and he fought as fiercely as a tiger to defend his land against British and Mughal soldiers. ...More
WHICH KINGS BUILT TALL STONE TOWERS?
- Shona kings of southeast Africa, who built a city called Great Zimbabwe. Zimbabwe means "stone houses". The city was also a massive fortress. From inside this fortress, the Shona kings ruled a rich empire from AD 1200 to 1600. The Shona......More
HOW LONG DID THE MUGHALS RULE?
- For more than three centuries, from 1526 to 1858. But from about 1750, Mughal emperors were weak and powerless. The last Mughal emperor was turned off his throne when the British government took control of India after Indian soldiers working for......More
WHO MADE WONDERFUL STATUES OF BRASS AND BRONZE?
- Artists and craft workers living in the great rainforest kingdom of Benin (part of present- day Nigeria), which was powerful from about 1400 to 1900. The statues were used to decorate the royal palace, and were placed on family altars in honour......More
WHICH AFRICAN CITY HAD A FAMOUS UNIVERSITY?
- Timbuktu, in present-day Mali, West Africa. The city was founded in the 11th century and became a great centre of learning for Muslim scholars from many lands. Timbuktu also had many mosques and markets, a royal palace, and a library. ...More
WHO FOUNDED A NEW RELIGION IN INDIA?
- Guru Nanak, a religious teacher who lived in northwest India from 1469 to 1539. He taught that there is One God, and that people should respect one another equally, as brothers and sisters. His followers became known as Sikhs. To make their......More
WHY DID BRITISH MERCHANTS GO TO INDIA?
- They knew that Indian goods, especially cotton cloth, drugs and dyestuffs, fetched high prices in Europe. In 1600 they set up the East India Company, to organize trade. The Company grew very rich, and had its own private army. By 1757, it......More
WHO CONQUERED A KINGDOM AGED ONLY 14?
- Prince Babur, who was descended from the greatest Mongol warrior Genghis Khan. He captured the city of Samarkand in 1497, then invaded Afghanistan, and conquered northern India in 1526. He founded a new empire in India, and a new dynasty of......More
WHO SAILED AROUND THE WORLD?
- The first round-the-world trip was made by sailors in the ship "Victoria", owned by Ferdinand Magellan, a Portuguese explorer. In 1519, he sailed eastwards from Europe, but was killed fighting in the Philippines. Most of his crew died......More
HOW DID THE MAORIS CROSS THE VAST PACIFIC OCEAN?
- By sailing and paddling big outrigger canoes. They steered by studying the waves and the stars, and made maps out of twigs and shells to help themselves navigate. ...More
DID THE ABORIGINALS ALWAYS LIVE IN AUSTRALIA?
- No, they probably arrived there from Southeast Asia about 60,000 years ago, at a time when the sea surrounding Australia was much shallower than today. They may have travelled by land or in small boats. ...More
HOW DID SAILORS HELP SCIENCE?
- By observing the plants, fishes and animals as they travelled, and by bringing specimens home with them. When Captain Cook explored the Pacific Ocean, he took artists and scientists with him to study and record what they saw. ...More
WHO ARRIVED IN AMERICA BY MISTAKE?
- Italian explorer Christopher Columbus. In 1492, he sailed westwards across the Atlantic from Spain. He hoped to reach China or India, but arrived instead in America, which was unknown. ...More
A BRIEF HISTORY OF EXPLORATION ACROSS THE OCEANS OF THE WORLD
- 1304-1377 Ibn Battuta sails to India and China. 1405-1433 Cheng Ho's voyages to Africa and Indonesia. 1419 Portuguese explorers begin to sail along the west coast of Africa. 1492 Columbus sails by mistake to America. 1497......More
WHO LIVES IN THE AUSTRALIAN DESERT?
- The Aboriginal people have lived in the desert for thousands of years. They learned how to find underground water, and to dig up nourishing roots hidden deep in the earth. They discovered which seeds, berries, grubs and animals are poisonous, and......More
WHO WERE THE FIRST PEOPLE TO DISCOVER NEW ZEALAND?
- The Maoris. They began a mass migration from other Pacific Islands in about AD I 150, but remains dating back to AD 800 have been found. ...More
WHAT WERE DINGOES USED FOR?
- Dingoes are descended from dogs introduced by aboriginal settlers thousands of years ago. They were used as guard dogs, and to keep Aboriginal people warm as they slept around campfires in the desert, which gets very cold at night. ...More
WHO EXPLORED THE EASTERN SEAS?
- Muslim explorer Ibn Battuta, who was born in Tangiers, North Africa, sailed to India and China in the 14th century. He was followed by Cheng Ho, a Chinese admiral, who made seven long voyages between 1405 and 1433. Cheng explored the seas around......More
WHO LIVED IN TENTS ON THE GREAT PLAINS?
- Native American hunters, like the Sioux/Dakota and the Cheyenne. After Europeans settled in America, bringing horses with them, Native Americans spent summer and autumn moving across the wide, rolling grasslands of the Great Plains, following......More
DID NATIVE AMERICANS LIVE IN BIG CITIES?
- Yes, some of them. The people who lived in the Mississippi valley about AD 700 to 1300 built huge cities as centres of farming and trade. Their biggest city, Cahokia, was home to at least 20,000 people. ...More
WHO WERE THE FIRST EUROPEANS TO SETTLE IN AMERICA?
- Spanish colonists, who settled in present-day Florida and California from about 1540. An English settlement began in Chesapeake Bay in 1607 and in Massachusetts in 1620. ...More
WHAT STORIES DO TOTEM POLES TELL?
- Native American people who lived in the forests of northwest North America carved tall totem poles to record their family's history, and to re-tell ancient legends about the powerful spirits that lived in all rocks, mountains, wild animals......More
WHO WENT TO THE BOSTON TEA PARTY?
- European settlers in America attended this famous demonstration. In 1773, they poured tonnes of tea imported from Britain into the waters of Boston harbour. They were protesting against paying taxes to help the British government fund the wars it......More
WHO BUILT STRANGE SHAPED MOUNDS?
- The Hopewell Native American people, who lived on the banks of the Ohio River. They buried their dead under huge heaps of earth, and created massive earth-mound sculptures. The biggest, "Serpent Mound", dates from about AD 1070, and is......More
WHEN DID THE USA BECOME INDEPENDENT?
- On July 4, 1776, 13 English colonies (the land where most Europeans in America had chosen to settle) proclaimed a Declaration of Independence. In it they refused to be ruled by Britain any longer. They became a new nation, the United States of......More
WHY DID THE PILGRIMS LEAVE HOME?
- The Pilgrims were a group of English families with strong religious beliefs, who quarreled with Church leaders and the government. In 1620 they sailed in the "Mayflower" to America, to build a new community where they could practice......More
WHO OR WHAT WERE THE THREE SISTERS?
- Beans, maize and squash (pumpkin), three essential food crops that Native American farmers grew wherever they could. ...More
WHY DID A CIVIL WAR BREAK OUT IN AMERICA?
- The American Civil War was caused mainly by a quarrel over slavery. The war lasted from 1861 to 1865 and was fought between the southern and northern states of the USA. The economy of the southern states relied on black slaves shipped from Africa......More
WHAT WAS THE INDUSTRIAL REVOLUTION?
- It was a big change in the way people worked and goods were produced. It began around 1775 in Britain and spread to Belgium, Germany, northern Italy, France and, after 1850, to the USA. Machines in huge factories replaced the craft workers who......More
WHEN DID THE FIRST TRAINS RUN?
- Horse-drawn railway wagons had been used to haul coal, ore and stone from mines and quarries since the 16th century, but the first passenger railway was opened by George Stephenson in the north of England in 1825. Its locomotives were powered by......More
WHY WERE DRAINS AND LAVATORIES SO IMPORTANT?
- Because without them, deadly diseases carried in sewage could spread very quickly through crowded industrial towns. Pottery-making was one of the first mass-production industries. Machines in 19th-century pottery factories produced millions of......More
WHO WORKED IN THE FIRST FACTORIES?
- Thousands of poor men and women moved from the countryside to live in fast-growing factory towns. They hoped to find regular work and more pay. Wages in factories were better than those on farms, and some people enjoyed the excitement and bustle......More
DID CHILDREN LEAD BETTER LIVES?
- No. Many worked 16 hours a day in factories and down mines. Large numbers were killed in accidents with machinery, or died from breathing coal dust, cotton fibres or chemical fumes. But after 1833, governments began to pass laws to protect child......More
DID NEW INDUSTRIES MAKE PEOPLE RICH?
- They made some inventors and factory owners very rich indeed. This angered many ordinary workers, who often earned barely enough to stay alive. In 1833 Robert Owen founded the first trade union, to campaign for better pay and conditions. ...More
HOW DID RAILWAYS CHANGE PEOPLE\'S LIVES?
- They helped trade and industry grow, by carrying raw materials to factories, and finished goods from factories to shops. They carried fresh foods from farms to cities. They made it easier for people to travel and encouraged a whole new holiday......More
WHO DROPPED THE FIRST ATOMIC BOMB?
- On August 6, 1945, the USA bombed Hiroshima in Japan, killing 66,000 people instantly and injuring another 69,000. By using this terrible new weapon on Japan, the USA, together with its allies Britain, France and the Soviet Union, hoped to bring......More
WHO SHOT THE RUSSIAN TSAR?
- Russian rebels, called Bolsheviks. In 1918, after the Russian Revolution (1917), they killed the whole Russian royal family and set up a Communist government instead. ...More
WHAT WAS THE LONG MARCH?
- A grueling march across China, covering 8,000 kilometres, made by around 100,000 communists escaping their enemies. They were led by Mao Zedong, who became ruler of China in 1949. It began in October 1934 and lasted about a year. ...More
WHAT WAS THE COLD WAR?
- A time of dangerous tension from the mid-1940s to the 1980s between the USA and the USSR, the r two strongest nations in the world. They had very different political systems and distrusted and feared one another. The USA believed in democracy and......More
HOW HAS THE WORLD CHANGED SINCE 1900?
- In many ways! European empires in Asia have collapsed, and new independent nations have taken their place. Women now play an important part in government. New scientific knowledge has saved millions of lives; cars and planes make travel faster......More
WHO FOUGHT AND DIED IN THE TRENCHES?
- Millions of young men during the World War I (1914-1918). Trenches were ditches dug deep into the ground. They were meant to shelter soldiers from enemy gunfire, but offered little protection from shells exploding overhead. Soon, the trenches......More
WHO COMPETED IN THE SPACE RACE?
- The USSR and the USA. Each tried to rival the other's achievements in space, because they hoped to prove that their nation was best. The USSR took the lead by launching the first satellite in 1957 and the first manned space flight in 1961,......More
WHO MADE FIVE YEAR PLANS?
- Joseph Stalin, the Russian Communist leader who ruled from 1924 to 1953. He reorganized the country in a series of Five Year Plans. He built thousands of new factories, took land away from ordinary people and divided it into vast collective......More
WHAT HAPPENS IN EVAPORATION AND CONDENSATION?
- Evaporation happens when a liquid is warmed up and changes to a vapour. Particles at the liquid's surface vibrate so fast they escape altogether. Condensation happens when a vapour is cooled down and becomes liquid. Evaporation and......More
WHICH SUBSTANCE HAS THE LOWEST FREEZING POINT?
- Mercury has the lowest freezing point of any metal, at -38.87° C. Helium has the lowest freezing point of all substances, at -272.2° C, which is less than I° above absolute zero. ...More
WHEN DO THINGS MELT?
- Things melt from solid to liquid on reaching a temperature called the melting point. Each substance has its own melting point. Water's is O°C; lead's is 327.5°C. ...More
WHEN DO THINGS FREEZE?
- Things freeze from liquid to solid when they reach the freezing point. Most substances get smaller when they freeze as the particles pack closer together. But water gets bigger as it turns to ice, which is why frozen pipes burst in winter. ...More
WHAT IS A PLASMA?
- A plasma is the fourth state of matter. It occurs only when a gas becomes so hot its atoms and molecules collide and electrons are ripped free. This happens inside the Sun, other stars and lightning, and in gas neon tubes. Plasmas are good......More
WHAT ARE SOLIDS?
- Substances can be either solid, liquid or gas - the three "states of matter". Substances move from one state to another when they are heated or cooled, boosting or reducing the energy of the particles they are made of. In solids,......More
WHAT IS PRESSURE?
- Pressure is the amount of force pressing on something. Air pressure is the force with which air presses. The force comes from the bombardment of the moving air particles. ...More
HOW DOES PRESSURE CHANGE?
- If you squeeze a gas into half the space, the pressure doubles (as long as the temperature stays the same). This is Boyle's law. If you warm up a gas, the pressure rises in proportion (as long as you keep it the same volume). This is the......More
WHEN DO THINGS BOIL?
- Things boil from liquid to gas when they reach boiling point, which is the maximum temperature a liquid can reach. For water this is 100°C. ...More
WHATSUBSTANCE HAS THE HIGHEST MELTING POINT?
- The metal with the highest melting point is tungsten, which melts at 3,410°C. But the highest melting point of any substance belongs to carbon, which melts at 3,527°C. ...More
WHAT IS AN ATOM?
- Atoms are what every substance is made of. Atoms are the smallest recognizable bit of any substance. They are so small that they are visible only under extremely high-powered microscopes - you could fit two billion atoms on the full stop at the......More
HOW BIG ARE ATOMS?
- Atoms are about a ten millionth of a millimetre across and weigh 100 trillionths of a trillionth of a gram. The smallest atom is hydrogen; the biggest is meitnerium. (Since they are so small, atoms are measured in terms of "moles". A......More
WHAT IS THE NUCLEUS?
- Most of an atom is empty space, but right at its centre is a very tiny area that is densely packed with particles much bigger than electrons. This is the nucleus, and it usually contains two kinds of nuclear particle-neutrons with no electrical......More
WHO SPLIT THE ATOM?
- Electrons can be split off from atoms easily, but in 1919, the New Zealand-born British physicist Ernest Rutherford (1871-1917) managed to split the nucleus of an atom by firing alpha particles at it. (Alpha particles are the nuclei of helium......More
WHAT ARE ELECTRONS?
- Electrons are the very tiny electrically charged particles that whizz around inside an atom. They were discovered by the English physicist J.J. Thomson (1856-1940) in 1897 during some experiments with cathode ray tubes. ...More
WHAT HOLDS ATOMS TOGETHER?
- Electrons are held to the nucleus by electrical attraction, because they have an opposite electrical charge to the protons in the nucleus. The particles of the nucleus are held together by a force called the strong nuclear force. ...More
WHAT ARE ELECTR SHELLS?
- Electrons behave as if they are stacked around the nucleus at different levels, like the layers of an onion. These levels are called shells, and there is room for only a particular number of electrons in each shell. The number of electrons in the......More
HOW MANY KINDS OF PARTICLE ARE THERE?
- Since the 1920s, scientists have discovered that there are at least 200 kinds of sub-atomic particle besides electrons, protons and neutrons. Most of these are created in special conditions and exist only for a very short time. ...More
WHAT IS A MOLECULE?
- Quite often, atoms cannot exist by themselves, and must always join up with others - either of the same kind, or with other kinds to form chemical compounds. A molecule is the smallest particle of a substance that can exist on its own. ...More
WHAT IS THE SMALLEST PARTICLE OF ALL?
- No one is sure. Atoms are made of protons, neutrons and electrons. In turn, these are made of even tinier particles - quarks and leptons. But one day, we might discover even smaller particles. ...More
WHAT IS AN ION?
- An ion is an atom that has either lost one or a few electrons, making it positively charged (cation) or gained a few, making it negatively charged (anion). Ions usually form when substances dissolve in a liquid. ...More
WHAT IS AN ELEMENT?
- It is a substance that cannot be split up into other substances. Water is not an element because it can be split into the gases oxygen and hydrogen. Oxygen and hydrogen are elements because they cannot be split. Every element has its own atomic......More
WHY IS CARBON SO SPECIAL?
- Carbon is the most friendly element in the Universe. With four electrons in the outer shell of its atom (and so four gaps), carbon atoms link very readily with other atoms. ...More
WHAT IS THE HEAVIEST ELEMENT?
- The heaviest is hahnium. It has 105 protons and 157 neutrons in its nucleus. The atomic mass of hahnium is 262. ...More
WHAT ARE THE LANTHANIDES?
- The lanthanides are a group of 15 elements in the middle of the periodic table that take their name from lanthanum. They are all shiny silvery metals and often occur naturally together. They all have two or three electrons in their outer electron......More
WHAT IS THE LIGHTEST ELEMENT?
- The lightest element is hydrogen. It has just one proton in its nucleus and has an atomic mass of just one. The heaviest is osmium, which is 10 times denser than lead. ...More
WHAT IS ATOMIC MASS?
- Atomic mass is the "weight" of one whole atom of a substance, which is of course very tiny! It includes all the particles in the atom - protons, neutrons and electrons. ...More
WHAT ARE THE TRANSITION METALS?
- Transition metals are the metals in the middle of the periodic table, such as chromium, gold and copper. They are generally shiny and tough, but easily shaped. They conduct electricity well and have high melting and boiling points. ...More
WHY ARE SOME ELEMENTS REACTIVE?
- Elements are reactive if they readily gain or lose electrons. Elements on the left of the periodic table, called metals, lose electrons very easily. The further left they are, the more reactive they are. So Group I metals (called the alkali......More
WHAT IS THE PERIODIC TABLE?
- All the elements can be ordered according to their properties, forming a chart called the periodic table. Columns are called groups, rows are called periods. Elements in the same group have the same number of electrons in the outer shell of their......More
WHO DISCOVERED RADIUM?
- The Polish-French physicist Marie Curie (1867-1934), born Marya Sklodowska, was the first woman to win not one, but two, Nobel prizes. The first, in 1903, was for her part in the discovery of radioactivity, and the second, in 1911, for her......More
WHAT ARE NOBLE GASES?
- Group O is the furthest right-hand column of the periodic table. This group is called the noble gases, because they do not readily react with other elements. But krypton, radon and xenon do combine with fluorine and oxygen to from compounds. They......More
HOW MANY ELEMENTS ARE THERE?
- New elements are sometimes discovered, but the total number identified so far is 112. ...More
WHAT IS A METAL?
- Most people can recognize a metal. It is hard, dense and shiny, and goes "ping" when you strike it with something else made of metal. It also conducts both electricity and heat well. Chemists define a metal as an electropositive......More
WHAT ARE COMPOUNDS?
- They are substances made from two or more elements joined together. Every molecule in a compound is the same combination of atoms. Sodium chloride, for instance, is one atom of sodium joined to one of chlorine. Compounds have different properties......More
WHAT IS ELECTROLYSIS?
- Electrolysis is a chemical reaction caused when an electric current is passed through a substance, the electrolyte. The effect is to make positive ions (or cations) move to the negative terminals (the cathode) and negative ions (or anions) move......More
WHAT IS A CHEMICAL FORMULA?
- A chemical formula is a shorthand way of describing an atom, an ion or a molecule. Initial letters (sometimes plus an extra letter) usually identify the atom or ion; a little number indicates how many atoms are involved. The formula for water is......More
WHAT THE SEA MADE OF?
- The sea is water with oxygen, carbon dioxide, nitrogen and various salts dissolved in it. The most abundant salt is common salt (sodium chloride). Others include Epsom salt (magnesium sulphate), magnesium chloride, potassium chloride, potassium......More
HOW DO THINGS DISSOLVE?
- When solids dissolve in liquid, it may look as if the solid disappears. Its atoms, ions or molecules are, in fact, still intact- but are separated and evenly dispersed throughout the liquid. ...More
WHAT IS A MIXTURE?
- Mixtures are substances that contain several chemical elements or compounds mixed in together but not chemically joined. The chemicals intermingle but do not react with each other, and with the right technique can often be separated. ...More
HOW DO BATTERIES WORK?
- Batteries create electric currents from the reaction between two chemicals, one forming a positive electrode and the other a negative. The reaction creates an excess of electrons on the negative electrode, producing a current. Chemicals used......More
HOW DO CHEMICALS REACT?
- When substances react chemically, their atoms, ions and molecules interact to form new combinations, separating elements from compounds or joining them together to form different compounds. Nearly all chemical reactions involve a change in......More
WHAT IS THE AIR MADE OF?
- Pure air is 78.9% nitrogen, 20.95% oxygen. There are traces of argon (0.93%), carbon dioxide (0.03%), helium (0.0005%), neon (0.018%), krypton (0.001 %), xenon (0.0001%) and radon. ...More
HOW DO NUCLEAR POWER STATIONS WORK?
- Inside the reactor there are fuel rods made from pellets of uranium dioxide, separated by spacers. When the station goes "on-line", a nuclear fission chain reaction is set up in the fuel rods. This is slowed down by control rods, which......More
HOW CAN RADIOACTIVITY BE USED TO INDICATE AGE?
- Radioactivity proceeds at a very steady rate. So by measuring how much of a substance has decayed radioactively, you can tell how old it is. With once-living things, the best radioactive isotope to measure is carbon-14. This form of dating is......More
WHAT IS AN ATOMIC BOMB?
- An atomic bomb or A-bomb is one of the two main kinds of nuclear weapon. It relies on the explosive nuclear fission of uranium-235 or plutonium-239. Hydrogen bombs, also called H-bombs or thermonuclear weapons, rely on the fusion of hydrogen......More
WHY IS NUCLEAR POWER AWESOME?
- The energy that binds together an atomic nucleus is enormous, even though the nucleus itself is so small. In fact, as Einstein showed in 1905, the particles of the nucleus can also be regarded as pure energy. This enables nuclear power with just......More
WHO INVENTED THE ATOMIC BOMB?
- The first atomic bombs were developed in the USA towards the end of World War II by a team of scientists under the leadership of Robert Oppenheimer (1904-1967)....More
WHAT EXACTLY IS RADIOACTIVITY?
- The atoms of an element may come in several different forms or isotopes. Each form has a different number of neutrons in the nucleus, indicated in the name, as in carbon- 12 and carbon-14. The nuclei of some of these isotopes - the ones......More
WHAT IS HALF-LIFE?
- No-one can predict when an atomic nucleus will decay. But scientists can predict how long it will take for half the atoms in a given quantity of a radioactive element to decay. This is its half-life. Strontium-90 has a half-life of 9 minutes.......More
WHAT IS NUCLEAR FISSION?
- Nuclear fission releases nuclear energy by splitting big atomic nuclei, usually those of uranium. Neutrons are fired at the nuclei. As the neutrons smash into the nuclei they split off more neutrons, which bombard other nuclei, setting off a......More
WHAT IS NUCLEAR FUSION?
- Nuclear energy is released by fusing or joining together small atoms like those of deuterium (a form of hydrogen). Nuclear fusion is the reaction that keeps stars glowing and provides energy for thermonuclear warheads. Scientists hope to find a......More
WHAT IS HYDROELECTRIC POWER?
- Hydroelectric power or HEP is electricity generated by turbines turned by falling water. Typically, hydroelectric power stations are sited inside dams built to create a big fall or "head" in the water. ...More
WHO MADE THE FIRST WATERWHEELS?
- Nobody knows for sure, but wheels turned by water to generate power were described by Ancient Greek writers over 2,000 years ago. ...More
WHAT IS HEAVY WATER?
- Heavy water is deuterium oxide, water that is a little heavier than ordinary water because it contains the hydrogen isotope deuterium rather than ordinary hydrogen. Heavy water is used in the nuclear industry to slow down nuclear reactions. ...More
WHAT SO SPECIAL ABOUT WATER?
- Water is essential to all living things. It is chemically neutral, yet dissolves many substances, which is why it is so important for life. It is denser as a liquid than a solid and so expands when it freezes. Water is found naturally as solid......More
WHY DO ICEBERGS FLOAT IN THE SEA?
- Fluids like water are incompressible - that is they cannot be squashed. So if you push fluid through a pipe, it will push out the other end. Hydraulic power uses fluid-filled pipes working like this to drive things very smoothly. Hydraulic means......More
WHY DO ICEBERGS FLOAT IN THE SEA?
- When most things get colder, they contract, and when most liquids freeze they get very much smaller. Water is unique in that it contracts only down to a certain temperature, 4°e. If it gets colder still, it begins to expand, because the......More
WHY DOES SWEATING KEEP YOU COOL?
- Because sweat is nearly all water, and water needs warmth to turn to vapour, which we call "drying". Watery sweat dries from the skin by taking warmth from the body. This makes the body cooler. ...More
WHY DO PLANTS NEED WATER?
- Plants need water for building cells, and also for transporting nutrients from the roots to the leaves where they are needed. ...More
HOW MUCH WATER IS THERE IN THE BODY?
- Water is found in nearly every cell of the body, which is why human bodies are almost three-quarters water. Women's bodies have slightly less water than men's, and children's bodies slightly less than women. ...More
WHY DO THINGS FLOAT?
- When an object is immersed in water, the weight of the object pushes it down. But the water around it pushes it back up with a force equal to the weight of water displaced (pushed out of the way). The object sinks until its weight is equaled by......More
HOW IS NATURAL OIL MADE?
- Oil is formed from tiny plants and animals that lived in warm seas millions of years ago. As they died, they were slowly buried beneath the sea bed. As the sea bed sediments hardened into rock, the remains of the organisms were turned to oil and......More
WHAT IS ORGANIC CHEMISTRY?
- Organic chemistry is the chemistry of carbon and its compounds. Carbon's unique atomic structure means it links atoms together in long chains, rings or other shapes to form thousands of different compounds. These include complex molecules,......More
WHAT IS CELLULOSE?
- Cellulose is a natural fibre found in the walls of all plant cells. It is a polymer, made of long chains of sugar molecules. These long chains make it tough and stringy, which is why we can't digest it when we eat plants. It passes through......More
WHAT IS DNA?
- DNA is deoxyribonucleic acid. This is the amazing long double-spiral molecule that is found inside every living cell. It is made up of long chains of sugars and phosphates linked by pairs of chemical "bases"- adenine, cytosine, guanine......More
WHAT IS A POLYMER?
- Polymers are substances made from long chains of thousands of small carbon-based molecules, called monomers, strung together. Some polymers occur naturally, such as wool and cotton, but plastics such as nylon and polythene are human-made......More
WHAT ARE AROMATICS?
- Chemicals that have a benzene ring are called aromatics, because benzene has a distinctive aroma. Benzene is a clear liquid organic chemical found in coal tar. It can be harmful, but has many uses, for example as a cleaning fluid and in......More
WHAT IS THE CARBON CYCLE?
- Carbon circulates like this: animals breathe out carbon as carbon dioxide. Plants take in carbon dioxide from the air and convert it into carbohydrates. When animals eat plants, they take in carbon again. ...More
WHAT ARE CARBOHYDRATES?
- Carbohydrates are chemicals made only of carbon, hydrogen and oxygen atoms, including sugars, starches and cellulose. Most animals rely on carbohydrate sugars such as glucose and sucrose for energy. ...More
HOW IS OIL REFINED?
- Oil drilled from the ground, called crude oil, is separated into different substances, mainly by distillation. This means the crude oil is heated until it evaporates. The substances are then drawn off and condensed from the vapour at different......More
HOW IS PLASTIC MADE?
- Most plastics are made from ethene, one of the products of cracked oil. When heated under pressure, the ethene molecules join in chains 30,000 or more long. These molecules get tangled like spaghetti. If the strands are held tightly together, the......More
WHAT ARE OILS?
- Oils are thick liquids that won't mix with water. Mineral oils used for motor fuel are hydrocarbons - that is, complex organic chemicals made from hydrogen and carbon. ...More
WHAT IS A CARBON CHAIN?
- Carbon atoms often link together like the links of a chain to form very long thin molecules, as in the molecule of propane, which consists of three carbon atoms in a row, with hydrogen atoms attached. ...More
WHO DISCOVERED THE SHAPE OF DNA?
- The discovery in 1953 that every molecule of DNA is shaped like a twisted rope ladder or "double helix" was one of the great scientific breakthroughs of the 20th century. Maurice Wilkins and Rosalind Franklin did the groundwork for the......More
WHAT ARE BUCKY BALLS?
- Before 1990, carbon was known in two main forms or allotropes: diamond and graphite. In 1990, a third allotrope was created. Its molecule looks like a football or the domed stadium roofs created by American architect Buckminster Fuller, so this......More
WHAT IS A KNOCK-ON EFFECT?
- When two objects collide, their combined momentum remains the same if nothing else interferes. So if one object loses momentum, this momentum must be passed on to the other object, making it move. This is essentially a knock-on effect. In this......More
WHO WAS EINSTEIN?
- Albert Einstein (1897-1955) was the scientific genius who transformed science with his two big theories - Special Relativity (1905) and General Relativity (1915). The theory of Special Relativity was developed while he was working in the Swiss......More
WHAT IS A TURNING FORCE?
- When something fixed in one place, called a fulcrum, is pushed or pulled elsewhere, it turns around the fulcrum. When you push a door shut, that push is the turning force, and the hinge is the fulcrum. ...More
HOW DO THINGS GET MOVING?
- Things only move if forced to move. So when something starts moving, there must be a force involved, whether it is visible, like someone pushing, or gravity, which makes things fall. But once they are moving, things will carry on moving at the......More
WHAT THE DIFFERENCE BETWEEN VELOCITY AND SPEED?
- Speed is how fast something is going. Velocity is how fast something is going and in which direction. Speed is called a scalar quantity; velocity a vector. ...More
WHY DO THINGS GO ROUND?
- If only one force is involved, things will always move in a straight line. This is called linear motion. Things go round when there is more than one force involved. A ball loops through the air because gravity is pulling it down while its......More
WHAT IS SPECIAL RELATIVITY?
- The theory of Special Relativity shows how both space and time can be measured only relatively, that is, in comparison to something else. This means that time can speed up or slow down, depending on how fast you are moving. ...More
WHAT THE FASTEST THING IN THE UNIVERSE?
- Light, which travels at 300,000 km per second. This is the one speed in the universe that is constant - that is, it is always the same no matter how fast you are going when you measure it. ...More
WHAT WAS NEWTON BREAK THROUGH?
- Sir Isaac Newton's breakthrough in 1665 was to realize that all movement in the universe is governed by three simple rules, which we now called Newton's Laws of Motion. The First is about inertia and momentum. For his three Laws of......More
WHAT IS UNIFORM MOTION?
- Uniform motion is when an object carries on travelling at exactly the same speed in exactly the same direction. ...More
WHAT THE DIFFERENCE BETWEEN INERTIA AND MOMENTUM?
- Inertia is the tendency of things to stay still unless they are forced to move. Momentum is the tendency for things to keep going once they are moving, unless forced to stop or slow. This is the First Law of Motion. ...More
WHAT IS ACCELERATION?
- Acceleration is how fast something gains speed. The larger the force and the lighter the object, the greater the acceleration. This is Newton's Second law of Motion. ...More
WHAT HAPPENS WITH EVERY ACTION?
- This is Newton's Third Law of Motion - for every action, there is an equal and opposite reaction. Which means that whenever something moves, there is a balance of forces pushing in opposite directions. When you push your legs against water to......More
WHY DO SATELLITES GO ROUND THE EARTH?
- Satellites are whizzing through space at exactly the right height for their speed. The Earth's gravity tries to pull them down to Earth, but they are travelling so fast that they go on zooming round the Earth just as fast as the Earth pulls......More
WHAT THE DIFFERENCE BETWEEN MASS AND WEIGHT?
- Mass is the amount of matter in an object. It is the same wherever you measure it, even on the Moon. Weight is a measure of the force of gravity on an object. It varies according to where you measure it. ...More
WHAT DID A GREAT SCIENTIST LEARN FROM AN APPLE?
- The mathematician and physicist Sir Isaac Newton is said to have developed his ideas about gravity while sitting one day under an apple tree. As he watched an apple fall to the ground, it occurred to him in a flash that the apple was not merely......More
WHAT IS POWER?
- Power is the rate at which work is done. A high-powered engine is an engine that can move a great deal of weight very quickly. Power is also the rate at which energy is transferred. A large amount of electric power might be needed to heat a large......More
WHAT IS GRAVITY?
- Gravity is the invisible force of attraction between every bit of matter in the universe. Its strength depends on the mass of the objects involved and their distance apart. ...More
WHAT DID GALILEO DO ON THE TOWER OF PISA?
- Galileo Galilei (1564- 1642) is said to have dropped metal balls of different weights from the Leaning Tower of Pisa to show that they all fall at the same speed. ...More
WHAT IS A FORCE?
- A force makes something move, by pushing or pulling it. Gravity is an invisible force. Other forces, such as a kick, we can see. To overcome Earth's gravity and fly into space, a rocket must reach a speed of roughly 40,000 km/h - this is......More
HOW FAST DOES A STONE FALL?
- At first the stone falls faster and faster at a rate of 9.8 m per second at every second. But as the stone's speed accelerates, air resistance increases until it becomes so great that the stone cannot fall any faster. It now continues to fall......More
WHY CAN YOU JUMP HIGHER ON THE MOON?
- The Moon is much smaller than the Earth, so its gravity is much weaker. Astronauts weigh six times less on the Moon than they do on Earth, and can jump much higher! ...More
HOW DOES GRAVITY HOLD YOU DOWN?
- The mutual gravitational attraction between the mass of your body and the mass of the Earth pulls them together. If you jump off a wall, the Earth pulls you towards the ground. You also pull the Earth towards you, but because you are tiny and the......More
WHAT IS FRICTION?
- Friction is the force between two things rubbing together, which may be brake pads on a bicycle wheel or air molecules against an aeroplane. Friction tends to slow things down, making them hot as their momentum is converted into heat. ...More
HOW IS FORCE MEASURED?
- Force is measured in newtons, in honour of Sir Isaac Newton. A newton is the force needed to accelerate 1 kg by 1 m per second every second. ...More
DOES GRAVITY VARY?
- An object's gravitational pull varies with its mass and its distance. In fact, gravity diminishes precisely in proportion to its distance away, squared. You can work out the force of gravity between two objects by multiplying their masses and......More
WHERE DOES OUR ENERGY COME FROM?
- Nearly all of our energy comes to us ultimately from the Sun. Some we get directly via solar power cells. Most comes indirectly via fossil fuels (coal and oil), which got their energy from the fossilized plants (and other organisms) of which they......More
HOW ARE ENERGY AND MASS LINKED?
- Energy is a form of mass; mass is a form of energy. In nuclear reactions, tiny amounts of mass are changed into huge quantities of energy. ...More
HOW IS TEMPERATURE MEASURED?
- Temperature is usually measured with a thermometer. Some thermometers have a metal strip that bends according to how hot it is. But most contain a liquid, such as mercury, in a tube. As it gets warmer, the liquid expands, and its level rises in......More
HOW IS ENERGY CONSERVED?
- Energy can be neither created nor destroyed. When energy is converted from one form to another, there is always exactly the same amount of energy afterwards as there was before. In this way energy is conserved, even when converted into a......More
WHAT THE DIFFERENCE BETWEEN HEAT AND TEMPERATURE?
- Heat is molecules moving. It is a form of energy, the combined energy of all the moving molecules. Temperature, on the other hand, is simply a measure of how fast all the molecules are moving....More
HOW DO YOU CONVERT FAHRENHEIT TO CELSIUS?
- You can convert from Fahrenheit to Celsius by subtracting 32 then dividing by nine and multiplying by five. You can convert from Celsius to Fahrenheit by dividing by five, multiplying by nine and adding 32....More
WHAT IS ABSOLUTE ZERO?
- Absolute zero is the coldest possible temperature, the temperature at which atoms stop moving altogether. This happens at -273.15 degree C, or 0 on the Kelvin scale. ...More
WHAT IS ENERGY EFFICIENCY?
- Some machines waste a great deal of energy, while others waste very little. The energy efficiency of a machine is measured by the proportion of energy it wastes. Waste energy is usually lost as heat....More
WHAT IS CONDUCTION?
- Conduction is one of the three ways in which heat moves. It involves heat spreading from hot areas to cold areas as moving particles knock into one another. The other ways are convection, in which warm air or water rises, and radiation, which is......More
WHAT IS ENERGY?
- Energy takes many forms. Heat energy boils water, keeps us warm and drives engines. Chemical energy fuels cars and aeroplanes. Electrical energy drives many small machines and keeps lights glowing. Almost every form of energy can be......More
HOW DO THINGS ABSORB LIGHT?
- When light rays hit a surface, some bounce off, but others are absorbed by atoms in the surface, warming it up very slightly. Each kind of atom absorbs particular wavelengths (colours) of light. The colour of the surface depends on which......More
HOW DO MIRRORS WORK?
- Most mirrors are made of ordinary glass, but the back is silvered - coated with a shiny metal that perfectly reflects all the light that hits it - at exactly the same angle. The image in a mirror is back-to-front or reversed. Left is on the......More
WHAT HAPPENS AT AN INTERFERENCE FRINGE?
- Interference is what happens when two light waves meet each other. If the waves are in step with each other, they reinforce each other. This is positive interference, and you see bright light. If they are out of step, they may cancel each other......More
WHAT IS AN INCIDENT RAY?
- When scientists talk about reflections, they distinguish between the light falling on the reflector (which may be a mirror) and the light reflected. Incident rays are the rays hitting the reflector. ...More
WHAT ARE PHOTONS?
- Photons are almost infinitesimally small particles of light. They have no mass and there are billions of them in a single beam of light. ...More
DOES LIGHT TRAVEL IN WAVES?
- In the last century, most scientists believed light did travel in tiny waves rather than bullet-like particles. Now they agree it can be both, and it is probably best to think of light as vibrating packets of energy. ...More
HOW IS LIGHT BENT?
- Light rays are bent when they are refracted. This happens when they strike a transparent material like glass or water, at an angle. The different materials slow the light waves down so that they slew round, like car wheels driving on to......More
WHY IS THE SKY BLUE?
- Sunlight is white, which means it contains all the colours of the rainbow. The sky is blue because air molecules scatter - reflect in all directions - more blue from sunlight towards our eyes than other colours. ...More
HOW DO YOUR EYES SEE THINGS?
- Light sources such as the Sun, stars and electric light shine light rays straight into your eyes. Everything else you see only by reflected light, that is, by light rays that bounce off things. So you can see things only if there is a light......More
HOW DO FIBRE-OPTIC CABLES BEND LIGHT?
- Actually they don't bend light, but reflect it round corners. Inside a cable are lots of bundles of glass fibres. Light rays zig-zag along the inside of each fibre, reflecting first one side, then the other. In this way, light can be......More
WHY IS THE SUN RED?
- The Sun is only red at sunrise and sunset, when the Sun is low in the sky and sunlight reaches us only after passing a long way through the dense lower layers of the atmosphere. Particles in the air absorb shorter, bluer wavelengths of light or......More
WHAT IS THE ELECTROMAGNETIC SPECTRUM?
- Light is just a small part of the wide range of radiation emitted by atoms - the only part we can see. This range of radiation is called the electromagnetic spectrum and ranges from long waves, such as radio waves and microwaves, to short waves,......More
WHAT IS INFRARED?
- Infrared is light with wavelengths too long for the human eye to register. But you can often feel infrared light as warmth. ...More
WHAT ARE THE COLOURS OF THE RAINBOW?
- The colours of the rainbow are all the colours contained in white light. When white light hits raindrops in the air, it is split up into a rainbow of colours, because each colour of light is refracted by the rainbow to a different extent. The......More
HOW DO TV SIGNALS TRAVEL?
- TV signals travel in one of three ways. Terrestrial broadcasts are beamed out from transmitters as radio waves to be picked up by TV aerials. Satellite broadcasts are sent up to satellites as microwaves, then picked up by satellite dishes. Cable......More
WHY CAN NOT YOU SEE ULTRAVIOLET?
- Ultraviolet light is light with wavelengths too short for the human eye to register. ...More
HOW DO CT SCANS WORK?
- CT (computed tomography) scans run X-ray beams right round the body, and pick up how much is absorbed with special sensors. A computer analyses the data to create a complete "slice" through the body. ...More
HOW DOES A PRISM SPLIT COLOURS?
- Prisms split white light into separate colours by refracting (bending) it. The longer the wavelength of the light, the more it is refracted, so long wavelength colours emerge from the prism at a different point from short wavelength......More
WHO MADE THE FIRST RADIO BROADCAST?
- Italian inventor Guglielmo Marconi first sent radio signals over 1.6 km in 1895. In 1898, he sent a message in Morse code across the English Channel. In 1901, he sent a radio message across the Atlantic Ocean. ...More
HOW DO X-RAYS SEE THROUGH YOU?
- X-rays are stopped only by the bones and especially dense bits of the body. They pass through the soft bits to hit a photographic plate on the far side of the body, where they leave a silhouette of the skeleton. ...More
WHAT MAKES LIGHTNING FLASH?
- Lightning flashes produce 100 million volts of static electricity. Lightning is created when raindrops and ice crystals inside a thundercloud become electrically charged as they are flung together, losing or gaining electrons from each other.......More
WHAT IS AN ELECTRIC CURRENT?
- A current is a continuous stream of electrical charge. It happens only when there is a complete, unbroken "circuit" for the current to flow through, typically a loop of copper wire. ...More
HOW DO ELECTRIC CURRENTS FLOW?
- The charge in an electric current is electrons that have broken free from their atoms. None of them moves very far, but the current is passed on as they bang into each other like rows of marbles. ...More
WHAT IS A SILICON CHIP?
- A silicon chip is an electronic circuit implanted in a small crystal of semi- conducting silicon, in such a way that it can be manufactured in huge numbers. This was the predecessor to the microprocessors that make computers work. ...More
WHY DOES YOUR HAIR GO FRIZZY?
- When you comb dry hair, tiny electrons are knocked off the atoms in the comb as it rubs past. Your hair is coated with these tiny negative electrical charges and so is attracted to anything that has its normal quota of electrons, or more. An......More
WHAT ARE THE BEST CONDUCTORS?
- The best conductors are metals like copper and silver. Water is also a good conductor. Superconductors are materials like aluminium, which is cooled until it transmits electricity almost without resistance. ...More
WHAT IS A VOLT?
- Electrical current flows as long as there is a difference in charge between two points in the circuit. This difference is called a potential and is measured in terms of volts. The bigger the difference, the bigger the voltage. ...More
WHAT IS AN ALTERNATING CURRENT?
- A direct current (DC) flows in one direction only. Most hand-held torches use DC. Electricity in the house is alternating current (AC), which means it continually swaps direction as the generator coil spins around past its electrodes. ...More
WHO INVENTED TRANSISTORS?
- Transistors were invented by three scientists working at the Bell Laboratories in the USA in 1948: William Shockley, Walter Brattain and John Bardeen. ...More
HOW DOES ELECTRIC LIGHT WORK?
- An electric bulb has a very thin filament of tungsten wire inside a glass bulb filled with argon or nitrogen gas. When current flows through such a thin wire, the resistance is so great that the wire heats up and glows brightly. If it wasn't......More
WHAT IS A SEMI- CONDUCTOR?
- Semi-conductors are materials such as silicon or germanium, which are partly resistant to electric current and partly conducting. They can be set up so that the conductivity is switched on or off, creating a tiny electrical switch. They are used......More
WHAT IS RESISTANCE?
- Not all substances conduct electric currents equally well. Resistance is a substance ability to block a flow of electric current. ...More
WHAT IS A MAGNETIC POLE?
- Magnetism is the invisible force that draws together some metals, such as iron and steel, or pushes them apart. This force is especially strong at each end of the magnet. These two powerful ends are called poles. One is called the north (or......More
WHY IS THE EARTH LIKE A MAGNET?
- As the Earth spins, the swirling of its iron core turns the core into a giant magnet. It is a little like the way a bicycle dynamo generates an electric current. Like smaller magnets, the Earth magnet has two poles, a north and a south. It is......More
HOW DOES SOUND TRAVEL?
- Every sound is created by vibration, be it an elastic band twanging or a loudspeaker cone shaking to and fro. But you can't hear any sounds in a vacuum. This is because the sound reaches your ears as a vibration, and there must be something......More
WHAT IS RESONANCE?
- An object always tends to vibrate freely at the same rate. This is its natural frequency. You can make it vibrate faster or slower by jogging it at particular intervals. But if you can jog it at just the same rate as its natural frequency, it......More
WHAT IS A LODESTONE?
- Thousands of years before people learned how to make steel magnets, they found that lumps of certain types of rock can attract or repel each other, or bits of iron. These rocks are called lodestones. They contain iron oxide, which makes them......More
WHAT IS AN ECHO?
- An echo is when you shout in a large empty hall or in a tunnel, and you hear the noise ringing back out at you a moment or two later. The echo is simply the sound of your voice bouncing back from the walls. You don't normally hear echoes,......More
WHAT IS SOUND FREQUENCY?
- Some sounds, like a car squealing brakes, are very high-pitched. Others, like a booming bass drum, are very low-pitched. What makes them different is the frequency of the sound waves. If the sound waves follow very rapidly one after another, they......More
WHAT IS A MAGNETIC FIELD?
- The magnetic field is the area around the magnet in which its effects are felt. It gets gradually weaker further away from the magnet. The Earth magnetic field extends some 80,000 km out into space. ...More
WHY DO BEAVERS BUILD DAMS?
- Beavers build their homes, or lodges, in streams or rivers. But first they need to build a dam to make an area of still water, or the current would wash the lodge away. With their huge front teeth, the beavers cut down trees to build the dam.......More
DO DORMICE REALLY SLEEP A LOT?
- Most dormice do sleep through the winter. This is called hibernation. It may start in October and last until April. Most dormice sleep in a cosy nest on the ground or in a burrow, though some nest in trees. ...More
HOW BIG IS A BEAVER?
- A fully grown beaver can measure over I m long, including its long, flat tail. It can weigh as much as 38 kg and is the heaviest rodent in North America and Eurasia. ...More
WHICH IS THE BIGGEST RODENT?
- The largest rodent in the world is the capybara, which lives in South America. It measures up to 1.25 m long and weighs up to 64 kg. Capybaras live beside water and feed on grasses. ...More
HOW MANY KINDS OF RODENT ARE THERE?
- There are more than 2,000 different species of rodent, including squirrels, hamsters and beavers as well as rats and mice. Rodents live all over the world in every kind of habitat, from the icy Arctic to scorching deserts and humid......More
WHERE DO PORCUPINES LIVE?
- There are two groups of porcupines. New World porcupines live in North and South America, mostly in trees. Old World porcupines live in Africa and parts of Asia. They are mostly ground-dwelling animals. All porcupines are covered in long, sharp......More
WHICH IS THE SMALLEST RODENT?
- One of the smallest rodents is the pygmy mouse of North America. It is only about 10 cm long, including its tail, and weighs just 7 g. The harvest mouse of Europe and Asia is only slightly bigger. ...More
WHAT DO BEAVERS EAT?
- Beavers eat plant food. In spring and summer they feed on fresh green leaves and grasses. In autumn they gather woody stems to eat. Some of these are stored under water near the lodge to keep fresh for the winter months. ...More
CAN FLYING SQUIRRELS REALLY FLY?
- No, but they can glide some distance from tree to tree. When the flying squirrel leaps into the air, it stretches out the skin flaps at the sides of its body. These act like a parachute, enabling it to glide gently down from one branch to......More
WHY DO RODENTS GET LONG IN THE TOOTH?
- The two sharp teeth, called incisors, at the front of the rodent jaw are the ones it uses for gnawing. A rodent incisors get worn down as it gnaws tough food, but they keep on growing throughout its life. ...More
WHEN IS A DOG REALLY A RAT?
- A prairie dog is actually not a dog at all. It is a type of rodent, and lives in North America. Prairie dogs live in family groups of one adult male and several females and their young. The family, or coterie, makes a burrow of connecting......More
IS A GUINEA PIG A RODENT?
- A guinea pig is a rodent. Wild guinea pigs, also known as cavies, live in South America, where they feed on leaves and grasses. Most cavies are about 22 cm long, but one type, the long- legged, hare-like mara, is up to 75 cm long. ...More
DO BEARS SLEEP THROUGH THE WINTER?
- Brown bears, Polar bears and American and Asian black bears that-live in the far north do sleep for much of the winter. Food supplies are poor and the bears hide themselves away in warm dens and live off their own fat reserves. Before their long......More
HOW BIG IS A BABY BEAR?
- Although adult bears are so big, they have tiny babies. A huge polar bear, weighing more than several people, gives birth to cubs of only about I kg, far smaller than most human babies. Baby pandas are tinier still. The mother weighs up to 100......More
WHAT DO GIANT PANDAS EAT?
- The main food of the giant panda is bamboo. An adult panda eats up to 18 kg of bamboo leaves and stems a day. Pandas also eat a small amount of other plants and even some little animals. ...More
HOW DO WOLF CUBS LEARN HOW TO HUNT?
- Wolf cubs learn how to hunt by watching their parents and other pack members and by playing. As the cubs run around and pounce on one another, they are also learning how to attack and ambush prey. ...More
HOW MANY KINDS OF BEAR ARE THERE?
- There are eight species of bear. They range in size from the sun bear, which weighs as little as 27 kg, to huge polar bears and brown bears. The brown bear is the most widespread bear. It lives in northern North America and parts of Europe and......More
HOW MANY KINDS OF WILD DOG ARE THERE?
- There are about 35 species in the wild dog family, including foxes, wolves, coyotes and hunting dogs. All are good runners and hunt other animals to eat. Antarctica is the only continent where there are no wild dogs. ...More
IS THE GIANT PANDA A BEAR?
- For years experts argued about whether this animal should be grouped with bears or raccoons or classed in a family of its own. Genetic evidence now suggests that the panda is a member of the bear family. ...More
WHERE DO GIANT PANDAS LIVE?
- Giant pandas live in bamboo forest reserves in west and central China, where they are protected. Some live in captivity in zoos. ...More
WHICH IS ONE OF THE BIGGEST BEARS?
- The polar bear of the Arctic is one of the largest bears. Fully grown males are up to 2.5 m long. Polar bears have thick white fur. They hunt seals and also young walruses and birds. ...More
WHAT DO FOXES EAT?
- Foxes, such as the red fox, are hunting animals. They kill and eat small creatures, including rats, mice and rabbits. But foxes are very adaptable and will eat more or less anything that comes their way, such as birds and birds' eggs, insects......More
WHAT IS A DINGO?
- Dingoes are Australian wild dogs. They are probably descended from dogs introduced 5,000-8,000 years ago by Aborigines. Nowadays, they hunt mainly sheep and rabbits. A fence of over 5,000 km has been built across southeastern Australia to keep......More
HOW BIG IS A WOLF PACK?
- In areas where there are plenty of large animals to catch, a pack may contain up to 30 wolves. Hunting in a pack means that the wolves can kill prey much larger than themselves, such as moose. A wolf pack has a home range, or territory, which it......More
CAN POLAR BEARS SWIM?
- Polar bears swim well and spend long periods in the freezing Arctic water. They are well equipped to survive the cold. They have a dense layer of underfur as well as a thin layer of stiff, shiny outer coat. Under the skin is a thick layer of fat......More
ARE THERE BEARS IN THE JUNGLE?
- Yes, there are two kinds of bear that live in jungle, or rainforest. Spectacled bears live in the cloud forest of South America, and the sun bear lives in rainforest in parts of Southeast Asia. ...More
WHY DO TIGERS HAVE STRIPES?
- A tiger stripes help it hide among grasses and leaves so it can surprise its prey. Tigers cannot run fast for long distances, so they depend on being able to get close to their prey before making the final pounce. The stripes help to break up......More
WHAT IS A SNOW LEOPARD?
- The snow leopard is a big cat that lives in the mountains in central Asia. Its beautiful pale coat with dark markings has made it the target of fur poachers. Killing snow leopards for their fur is now illegal, but poaching still goes on. ...More
WHICH CAT RUNS THE FASTEST?
- The cheetah is the fastest running cat and one of the speediest of all animals over short distances. It has been timed running at 93 km/h over a distance of 300 m. Olympic sprinters can only reach between 30-40 km/h. ...More
WHICH BIG CAT IS THE BIGGEST?
- Tigers are the biggest of the big cats. They can measure over 3 m long, including the tail, and weigh 250 kg or more. Tigers are becoming very rare. They live in parts of Asia, from snowy Siberia in the north to the tropical rainforests of......More
WHY ARE LIONS UNLIKE OTHER CATS?
- Unless they are rearing their young, most cats, including tigers and cheetahs, live alone. But lions live and hunt in a group called a pride. A lion pride includes several females and their cubs and one or two adult males who defend the pride......More
IS A CIVET A KIND OF CAT?
- No, civets belong to a separate family, which also includes mongooses, meerkats and genets. Most civets live in tropical forests in Southeast Asia or Africa. They have a long, slender body, short legs and a long tail. The African civet is about......More
HOW MANY KINDS OF CAT ARE THERE?
- There are about 36 species of wild cat, ranging from the tiger to the African wild cat, which is closely related to the domestic cats. Cats live in most parts of the world in every sort of habitat from tropical rainforest and desert to the icy......More
WHAT DOES A MONGOOSE EAT?
- The mongoose is a fast- moving little hunter. It kills small creatures such as rats, mice and frogs, and also eats insects and birds' eggs. It will even tackle a large snake. ...More
WHAT DO LIONS DO ALL DAY?
- Like domestic cats, lions are actually asleep for a surprisingly large part of the day. As much as 20 hours a day are spent resting and grooming. The rest of the time is taken up with looking for prey, hunting and feeding. Lionesses do most of......More
WHAT IS A PANTHER?
- A panther is simply a leopard with a black coat instead of spots. It is not a separate species of cat. Leopards live in Africa and Asia. ...More
WHERE DO JAGUARS LIVE?
- Jaguars live in the forests of Central and South America. They are the largest South American cats and measure up to 1.8 m long with a tail of up to 75 cm. Despite its size, the jaguar is a good climber and often clambers up a tree to watch for......More
WHAT IS A MEERKAT?
- A meerkat is closely related to the mongoose. Meerkats live in Africa in large groups of up to 30 or more animals. They share the guarding of young and finding of food. Sentry meerkats often stand up on their hind legs to watch out for......More
HOW TALL IS A GIRAFFE?
- A male giraffe stands up to 5.5 m tall to the tips of its horns. It has an extraordinarily long neck, and front legs that are longer than its back legs so that the body slopes down towards the tail. The long neck allows it to feed on leaves high......More
HOW MANY BONES ARE THERE IN A GIRAFFE NECK?
- A giraffe has seven bones in its neck, just like other mammals, including humans. But the giraffe neck bones are much longer than those of other animals, and have more flexible joints between them. ...More
CAN HIPPOS SWIM?
- The hippo spends most of its day in or near water and comes out onto land at night to feed on plants. It is a powerful swimmer and walks on the bottom of the river at surprisingly fast speeds. ...More
WHAT IS AN OKAPI?
- An okapi is a relative of the giraffe that lives in the African rainforest. It was unknown until 1900. The male has small horns on its head and a long tongue like a giraffe, but it does not have a long neck. ...More
HOW LONG ARE AN ELEPHANT TUSKS?
- An elephant tusks grow throughout its life, so the oldest elephants have the longest tusks. One pair in the British Museum weighs 133 kilograms, and one of them measures 3.5 metres. ...More
WHAT DO ELEPHANTS DO WITH THEIR TRUNKS?
- The elephant trunk is very useful. Without it, an elephant could not reach the ground to feed because its neck is so short. The trunk is also used for taking food from high in the trees and for breaking off branches. The elephant can smell with......More
HOW CAN YOU TELL AN AFRICAN ELEPHANT FROM AN ASIAN ELEPHANT?
- The African elephant is bigger and has larger ears and longer tusks. The head and body of the African elephant measures up to 7.5 m long. The Asian elephant measures up to 6.5 m long and has a more humped back. There is another difference at the......More
HOW MUCH DO ELEPHANTS EAT?
- A fully grown elephant eats 75 to 150 kg of plant food a day. Its diet includes grass, twigs, branches, leaves, flowers and fruits. ...More
ARE RHINOCEROSES FIERCE ANIMALS?
- Despite their ferocious appearance and huge horns, white rhinos are usually peaceful, plant-eating animals. However, black rhinos can be ill-tempered and aggressive. If threatened, one will charge its enemy at high speed. Mothers defending their......More
HOW BIG IS A BABY ELEPHANT?
- A newborn African baby elephant weighs up to 120 kg and stands up to I m high. It sometimes feeds on its mother milk for five years, by which time it may weigh more than 1 ton. ...More
HOW MUCH DOES A KOALA EAT EVERY DAY?
- A koala eats about 500 g of eucalyptus leaves every day, which it chews down to a fine pulp with its broad teeth. The leaves do not provide much energy, but koalas are slow-moving animals and sleep up to 20 hours a day. ...More
DO ALL MARSUPIALS LIVE IN AUSTRALIA?
- Most of the 260 or so species of marsupial live in Australia and New Guinea, but there are about 80 species of marsupial opossum in South America. One of these also lives in North America. KOALA BEAR ...More
WHAT IS A TASMANIAN DEVIL?
- The Tasmanian devil is the largest of the carnivores, or flesh-eating marsupials. It is about 90 cm long, including its tail, and has sharp teeth and strong jaws. The devil feeds mostly on carrion - the flesh of animals that are already dead -......More
IS A KOALA REALLY A KIND OF BEAR?
- No, it a marsupial like a kangaroo and not related to bears at all. Koalas live in Australia in eucalyptus forests. They feed almost entirely on eucalyptus leaves, preferring those of only a few species. A baby koala spends its first six or seven......More
DO ALL MARSUPIALS HAVE A POUCH?
- Most female marsupials have a pouch, but not all. Some very small marsupials such as the shrew opossums of South America do not have a pouch. Others, such as the American opossums, simply have flaps of skin around the nipples and not a full......More
HOW MANY KINDS OF KANGAROO AND WALLABY ARE THERE?
- There are more than 50 different species of kangaroo and wallaby. All live in Australia or New Guinea. The red kangaroo, which weighs about 90 kg, is the largest, and the tiny musky rat kangaroo, weighing only 0.5 kg, is the smallest. ...More
WHICH IS THE SMALLEST MARSUPIAL?
- The smallest marsupials are the mouse-like ningauis, which live in Australia. These little creatures are only about 5 cm long and can weigh as little as 2.8 g. They feed on insects. ...More
WHAT ARE BANDICOOTS?
- Bandicoots are a group of small marsupials that live in Australia and New Guinea. Most have short legs, a rounded body and a long pointed nose. They have strong claws, which they use to dig for insects and other small creatures in the......More
WHY DOES A KANGAROO HAVE A POUCH?
- At birth, kangaroos are very tiny and extremely poorly developed. In fact, a kangaroo is only about 2 cm long when it is born. The female kangaroo has a pouch so that its young can complete their development in safety. The tiny newborn crawls up......More
IS A PLATYPUS A MARSUPIAL?
- No, the platypus is not a marsupial, but it is an unusual animal that lives in Australia. Unlike most mammals, which give birth to live young, the platypus lays eggs. The mother leaves her two or four eggs to incubate in a burrow for between six......More
WHAT IS A WOMBAT?
- A wombat is a small bear-like marsupial with a heavy body and short strong legs. It digs burrows to shelter in and feeds mostly on grass. Its pouch opens to the rear so that it does not fill up with earth when the wombat is burrowing. ...More
HOW FAST DO KANGAROOS MOVE?
- A kangaroo bounds along on its strong back legs at up to 50 km/h. It can cover 13.5 m in one giant bound. ...More
DO ANY MARSUPIALS SWIM?
- The water opossum of South America is an excellent swimmer and has webbed back feet. Strong muscles keep its pouch closed when the opossum is in water. ...More
WHAT DO KANGAROOS EAT?
- Kangaroos eat grass and the leaves of low- growing plants, just like deer and antelopes do in the northern hemisphere. ...More
WHAT DO GORILLAS EAT?
- Gorillas eat plant food, such as leaves, buds, stems and fruit. Because their diet is juicy, gorillas rarely need to drink. ...More
DO CHIMPANZEES LIVE IN FAMILY GROUPS?
- Yes, in very large families that may include between 20 and 100 animals, led by a dominant male. Each group has its own home range. ...More
WHERE DO ORANG-UTANS LIVE?
- Orang-utans live in Southeast Asia in the rainforests of Sumatra and Borneo. This ape has long, reddish fur and spends most of its life in the trees. Fruit is its main food but the orang-utan also eats leaves, insects and even eggs and small......More
WHERE DO CHIMPANZEES LIVE?
- Chimpanzees live in forest and grasslands in Equatorial Africa. There is another less familiar chimpanzee species called the pygmy chimpanzee, or bonobo, which lives in rainforests in Congo in Africa. It has longer limbs than the common......More
WHAT IS AN APE?
- Apes are the most advanced animals in the primate group, which also includes animals such as lemurs, bush babies and monkeys. There are three families of apes. One includes all the different kinds of gibbons. The second contains the gorilla,......More
HOW MANY KINDS OF MONKEY ARE THERE?
- About 160 species in three main groups. One group lives in Africa and Asia. The other two groups live in Central and South America. ...More
WHY DOESA MONKEY HAVE A LONG TAIL?
- To help it balance and control its movements as it leaps from branch to branch in the rainforest. The tails of some South American monkeys are even more useful than those of their African and Asian relatives, because they are prehensile. A......More
DO CHIMPANZEES HUNT PREY?
- Yes they do. Although fruit is the main food of chimpanzees, they also eat insects and hunt young animals, including monkeys. They hunt alone or in a group. Groups work together, some cutting a couple of animals out of the herd and driving them......More
WHICH IS THE BIGGEST APE?
- The gorilla. A fully grown male stands up to 1.7 m tall and weighs as much as 220 kg. Gorillas live in the forests of West and Central Africa. A family group contains one or two adult male, several females and a number of young of different ages.......More
DO ANY MONKEYS LIVE IN COLD PLACES?
- Most monkeys are found in warm areas near to the equator, but some macaque monkeys live in cooler places. The rhesus macaque lives in the Himalayas as well as in parts of China and India, and the Japanese macaque survives freezing winters with......More
DO CHIMPANZEES USE TOOLS?
- Yes. The chimpanzee can get food by poking a stick into an ants' nest. It pulls out the stick and licks off the ants. It also uses stones to crack nuts, and it makes sponges from chewed leaves to mop up water or wipe its body. ...More
WHICH IS THE SMALLEST MONKEY?
- The smallest monkey is the pygmy marmoset of the South American rainforests. It is about 14 cm long, plus tail, and it weighs only about between 85 and 141 g. ...More
WHICH MONKEY MAKES THE LOUDEST NOISE?
- Howler monkeys shout louder than other monkeys and are among the noisiest of all animals. Their voices carry for more than 3 km. ...More
HOW BIG ARE SEA LIONS?
- The biggest sea lion is the huge male steller sea lion, It is about 3 m long and weighs as much as 1,000 kg. Females are much smaller and weigh only about 270 kg. The smallest is probably the female Galapagos fur seal, which is about 1.2 m long......More
HOW DEEP DO SEALS DIVE?
- The Weddell seal of Antarctic waters is one of the deepest- diving seals. It can go down to depths of more than 600 m in search of food. When he seal dives, blood flow is cut off to all but essential organs such as the heart. ...More
HOW BIG IS A WALRUS?
- The largest male walruses are more than 3 m long and weigh 1,70o, kg. Females are smaller, averaging 2.7 m long and weighing about 800 kg. The walrus skin is up to 4 cm thick and covered With coarse hairs. The thick skin helps protect the walrus......More
ARE ANY SEALS VERY RARE?
- Yes, monk seals, which live in, the Caribbean, Mediterranean and Hawaiian seas, are extremely rare. The Caribbean seal is probably already extinct. They live in warm seas, closer to human activity than most other seals, so they have suffered......More
HOW CAN YOU TELL A SEAL FROM A SEA LION?
- With practice! Seals and sea lions both have streamlined bodies adapted to marine living, and flippers instead of limbs. But there are several differences between them. Sea lions have small ear flaps, whereas seals have only ear openings. Sea......More
WHICH IS THE BIGGEST SEAL?
- The male elephant seal is the biggest of all the seals. It is 6.5 m long and weighs up to 3,600 kg, which is as much as a small elephant. ...More
ARE BABY SEALS AND SEA LIONS BORN IN WATER?
- No, they are born on land. Seals and sea lions spend most of their lives in water, but do come out onto land to give birth. They remain on land for a number of weeks, feeding their young on their rich milk. ...More
DO SEALS LIVE IN FRESH WATER?
- Yes, there is a species of freshwater seal in Lake Baikal in Russia. Baikal is the deepest freshwater lake in the world and holds more water than any other. Thousands of seals live there, feeding on freshwater fish and resting on the remote......More
HOW DO SEALS KEEP WARM IN COLD SEAS?
- A layer of fatty blubber under the skin helps to keep seals and sea lions warm. The blubber may be up to 10 cm thick. These animals also have a covering of fur. ...More
HOW LONG AREA WALRUS TUSKS?
- The tusks of an adult male walrus can be up to 55 cm long. Tusks are used as hooks for climbing on ice and as weapons for fighting. Experts also believe that the tusks are for display and attracting mates. ...More
DO SEALS AND SEA LIONS BREATHE AIR?
- Seals and sea lions are mammals so they have to come to the surface regularly to breathe air. But they can stay underwater much longer than we can. Dives lasting 20 minutes or more are common and the Weddell seal has been timed making a dive of......More
WHICH IS THE SMALLEST SEAL?
- The Baikal seal is the smallest seal in the world. It is about 1.2 m long and weighs between 63 and 70 kg. The Baikal seal is only found in Russia isolated Lake Baikal. It is the only seal to live solely in fresh water. ...More
WHAT DO SEALS AND SEA LIONS EAT?
- Fish is their main diet, but some also eat shellfish and catch larger prey. Some seals have a more varied diet. The crabeater seal feeds mostly on krill - small shrimp-like crustaceans. The bearded seal eats sea bed creatures such as clams, and......More
HOW MANY KINDS OF SEAL AND SEA LION ARE THERE?
- There are about 14 species of sea Ii n, 18 species of seal an one species of walrus. Most sea lions live along North Pacific coasts and on the southern coasts of Africa, Australia and South America. Most seals live in waters to the far north and......More
HOW FAST CAN SEALS AND SEA LIONS SWIM?
- Sea lion can reach swimming speeds of 40 km/h. On land, the crabeater seal can reach 25 km/h. ...More
WHICH IS THE BIGGEST WHALE?
- The blue whale is the largest whale, and also the largest mammal that has ever lived. It measures more than 30 m long and weighs at least 90 tonnes. The biggest blue whales may weigh more than twice this amount. Although it is so huge, the blue......More
HOW DOES A BLUE WHALE FEED?
- A blue whale filters small shrimp-like creatures called krill from the water. Hanging from the whale upper jaw are lots of plates of a fringed bristly material called baleen. The whale opens its mouth and water full of krill flows in. The whale......More
WHICH WHALE DIVES DEEPEST?
- The sperm whale is routinely found at I km beneath the surface of the sea. ...More
DO HUMPBACK WHALES REALLY SING?
- Yes, they do. They make a series of sounds, including high whistles and low rumbles, that may last from five to thirty-five minutes. No one knows why the humpback whale sings, but it may be to court a mate or to keep in touch with others in the......More
WHY DO SOME WHALES MIGRATE?
- Whales such as humpbacks migrate - travel seasonally - to find the best conditions for feeding and breeding. They spend much of the year feeding in the waters of the Arctic and Antarctic, where there is lots of krill to eat. When it is time to......More
DO WHALES EVER COME TO LAND?
- No, whales spend their whole lives in the sea. But they do breathe air and have to come to the surface regularly to take breaths. ...More
HOW BIG IS A BABY BLUE WHALE?
- A baby blue whale is about 8 m long at birth and is the biggest baby in the animal kingdom. It weighs about 3 tonnes. ...More
IS A DOLPHIN A KIND OF WHALE?
- A dolphin is a small whale. Most of the 32 or so species of dolphin live in the sea, but there are five species that live in rivers. The biggest dolphin is the killer whale, or orca, which grows up to 9.8 m long. Dolphins have a streamlined shape......More
WHAT IS A PORPOISE?
- A porpoise is a small whale with a rounded head, not a beaked snout like a dolphin. There are about six species of porpoise. They live in coastal waters in the Atlantic, Pacific and Indian oceans. ...More
HOW FAST DO WHALES SWIM?
- Blue whales normally swim at about 8 km/h, but can move at speeds of up to 30 km/h when disturbed. Some small whales, such as pilot whales and dolphins, may swim at more than 50 km/h. ...More
DO WHALES GIVE BIRTH IN THE WATER?
- Yes, they do. The baby whale comes out of the mother body tail first so that it does not drown during birth. As soon as the head emerges, the mother and the other females attending the birth help the baby whale swim to the surface to take its......More
WHAT IS A NARWHAL?
- A narwhal is a whale with a single long tusk at the front of its head. The tusk is actually a tooth, which grows out from the upper jaw. It can be as much as 3 m long. Only male narwhals have tusks. They may use them in battles with other......More
HOW MANY TYPES OF FROG AND TOAD ARE THERE?
- There may be as many as 4,000 species of frog and toad. They live on all continents except Antarctica. Most live in areas with plenty of rainfall, but some manage to live in drier lands by sheltering in burrows. ...More
WHAT DO FROGS EAT?
- Adult frogs catch insects and spiders and other small creatures such as crayfish - and even other frogs - to eat. Tadpoles usually feed on small water plants. ...More
WHY DO FROGS CROAK?
- Male frogs make their croaking calls to attract females. The frog has a special sac of skin under its chin, which blows up and helps make the call louder. ...More
CAN THE FLYING FROG REALLY FLY?
- No, but it can glide 15 m through the air between trees. When the frog jumps into the air it stretches out its legs and toes so that its webbed feet act like little parachutes. Small flaps of skin on the legs also help the frog to glide. The......More
HOW CAN TREE FROGS CLIMB TREES?
- Tree frogs are excellent climbers. On each of their long toes is a round sticky pad, which allows them to cling to the undersides of leaves and to run up the smoothest surfaces. Tree frogs spend most of their lives in trees, catching insects to......More
WHAT IS AN AMPHIBIAN?
- An amphibian is a creature that lives in water and on land. Amphibians evolved from fish and were the first vertebrates (creatures with backbones) to live on land. There are over 4,000 species of amphibian, including frogs, toads, newts and......More
DO ALL FROGS LAY THEIR EGGS IN WATER?
- No, some frogs have very unusual breeding habits. The male marsupial frog (and sometimes the female) carries his mate eggs in a pouch on his back or hip. The male Darwin frog keeps his mate eggs in its vocal pouch until they have developed into......More
WHICH IS THE SMALLEST FROG?
- The smallest frog, and the smallest of all amphibians, is the Cuban frog, which measures around 9.8 mm long. The tiny gold frog, which lives in Brazilian rainforests, is probably about the same size. ...More
HOW DID THE SPADEFOOT TOAD GET ITS NAME?
- The spadefoot toad got its name from the hard spade-like projections on each back foot, which it uses for digging its burrow. The toad backs into the ground, pushing soil away with its "spades". It usually spends the day deep in its......More
WHAT IS A SALAMANDER?
- A salamander looks like a lizard with its long body and tail, but it is an amphibian like frogs and toads. There are over 350 different kinds. The biggest is the giant salamander, which can grow as big as 1.5 m long. ...More
ARE FROGS AND TOADS POISONOUS?
- Some are - the giant, or cane toad can squirt poison at an enemy from glands near its eyes, and the fire-bellied toad has poison in its skin. But most deadly of all are the poison-arrow frogs that live in South American rainforests. Their skin......More
WHAT IS A TADPOLE?
- A tadpole is the young, or larva, of an amphibian such as a frog or newt. The amphibian egg is usually laid in water and hatches out into a small, swimming creature with a long tail called a tadpole. The tadpole feeds on water plants and......More
HOW BIG IS A GIANT TOAD?
- The giant, or cane toad, which is native to parts of the southern United States and South America, is up to 24 cm long. It eats beetles, and was introduced into Australia by farmers, in an effort to control the beetles that eat crops such as......More
DO TURTLES EVER COME TO LAND?
- Female sea turtles do come to land to lay their eggs. The female turtle drags herself up on to a sandy beach and digs a deep pit. She lays lots of eggs and covers them with sand. She then returns to the sea. When the young hatch, they must dig......More
WHAT DO SEA TURTLES EAT?
- Most sea turtles eat a range of underwater creatures, such as clams, shrimps and snails, but some concentrate on certain foods. The hawksbill is one of the few creatures that feed mostly on sponges. The leatherback main food is jellyfish, while......More
WHICH IS THE BIGGEST TURTLE?
- The leatherback is the largest of all the turtles. It grows up to 1.6 m long and weighs up to 360 kg. ...More
HOW CAN YOU TELL A CROCODILE FROM AN ALLIGATOR?
- You can recognize a crocodile because its teeth stick out when its mouth is shut! In many ways, crocodiles and alligators are very similar. They both have long bodies covered with thick scales. And they both have long jaws with lots of sharp......More
DO CROCODILES LAY EGGS?
- Crocodiles do lay eggs and they look after them very carefully. Most female crocodiles dig a pit into which they lay 30 or more eggs. They cover them over with earth or sand. While the eggs incubate for about three months, the female crocodile......More
HOW BIG IS A GIANT TORTOISE?
- Giant tortoises can grow to over 1.3 m long and weigh more than 140 kg. They live on the Galapagos Islands in the Pacific and on the island of Aldabra in the Indian Ocean. Seychelles giant tortoises were thought to be extinct in the wild - to......More
WHICH IS THE BIGGEST CROCODILE?
- The Nile crocodile grows up to 6 m long, but the Indopacific crocodile may be even larger. This mighty crocodile, which lives in parts of Southeast Asia, has been recorded as growing to 7 m or more. ...More
WHAT DO CROCODILES EAT?
- Baby crocodiles start by catching insects and spiders to eat. As they grow, fish and birds form a larger part of their diet. Fully grown crocodiles prey on anything that comes their way, even large animals such as giraffes. The crocodile lies in......More
HOW MANY TYPES OF CROCODILE ARE THERE?
- There are 14 species of crocodile, two species of alligator, several species of caiman and one species of gavial. The gavial is very like the crocodile and the alligator, but has a long, very slender snout. ...More
WHICH IS THE LARGEST LIZARD?
- The Komodo dragon, which lives on some Southeast Asian islands. It grows up to 3 m long and hunts animals such as wild pigs and small deer. ...More
WHY DOES A RATTLE SNAKE RATTLE?
- Rattlesnakes make their rattling noise to warn their enemies to stay well away. The rattle is made by a number of hard rings of skin at the end of the tail that make a noise when shaken. Each ring was once the tip of the tail. A new one is added......More
WHY DOES A CHAMELEON CHANGE COLOUR?
- Changing colour helps the chameleon get near to its prey without being seen and allows it to hide from its own enemies. The colour change is controlled by the chameleon nervous system. Nerves cause areas of colour in the skin to be spread out or......More
WHERE DO CHAMELEONS LIVE?
- There are about 85 different sorts of chameleon and most of these live in Africa and Madagascar. There are a few Asian species and one kind of chameleon lives in parts of southern Europe. ...More
HOW MANY KINDS OF LIZARD ARE THERE?
- There are probably over 3,000 species of lizard. These belong to different groups, such as the geckos, iguanas, skinks and chameleons. lizards live on all the continents except Antarctica, mostly in warm parts of the world. ...More
HOW MANY KINDS OF SNAKE ARE THERE?
- There are over 2,500 species of snake. They live on all continents except Antarctica. but there are no snakes In Ireland, Iceland or New Zealand. All snakes are carnivorous means that they feed on other animals. ...More
WHICH IS THE MOST DANGEROUS SNAKE?
- The saw-scaled carpet viper is probably the world most dangerous snake. It is extremely aggressive and its poison can kill humans. Saw- scaled carpet vipers live in Africa and Asia. ...More
HOW FAST DO SNAKES MOVE?
- The fastest-moving snake on land is thought to be the black mamba, which lives in Africa. It can wriggle along at up to 11 km/h. ...More
ARE THERE ANY POISONOUS LIZARDS?
- There are only two poisonous lizards in the world, the gila monster and the Mexican beaded lizard. Both of these live in southwestern North America. The poison is made in glands in the lower jaw. When the lizard seizes a prey and starts to chew,......More
ARE THERE ANY SNAKES IN THE SEA?
- Yes, there are about 50 to 60 different species of snake that spend their whole lives in the sea. Most are completely helpless on land. They eat fish and other sea creatures, such as shrimp, and all are extremely poisonous. One species, the......More
WHY DO SNAKES SHED THEIR SKIN?
- Snakes shed their skin, or moult, to allow for growth and because their skin gets worn and damaged. Some snakes, even as adults, shed there skin every 20 days. ...More
ARE ALL SNAKES POISONOUS?
- Only about a third of all snakes are poisonous and fewer still have poison strong enough to harm humans. Non-poisonous snakes either crush their prey to death or simply swallow it whole. ...More
WHICH IS THE BIGGEST SNAKE?
- The world longest snake is the reticulated python, which lives in parts of Southeast Asia. It grows to an amazing 10m long. The anaconda, which lives in South American rainforests, is heavier than the python but not quite as long. Pythons and......More
WHICH IS THE BIGGEST PENGUIN?
- The emperor penguin lives in Antarctica and is the biggest penguin in the world. It stands about 115 cm tall. Like all penguins, it cannot fly, but it is an expert swimmer and diver, using its wings as paddles. It spends most of its life in the......More
WHAT IS A TROPICBIRO?
- A tropicbird is a seabird with two very long central tail feathers. There are three species, all of which fly over tropical oceans. ...More
HOW FAST PENGUINS SWIM?
- Penguins can swim at speeds of 13 km/h, but they may move even faster for short periods. They can dive under water for two minutes or more. Some penguins are believed to be able to stay under water for up to 20 minutes. ...More
WHICH IS THE SMALLEST PENGUIN?
- The little, or fairy, penguin is the smallest penguin. It is only about 40 cm long. It lives in waters off the coasts of New Zealand and Tasmania, Australia. ...More
DO ALL PENGUINS LIVE IN ANTARCTICA?
- Most of the 18 species of penguin live in or near Antarctica, but some are found in warmer areas. There are several species around New Zealand and South America, one in the tropical Galapagos Islands and one on South African coasts. There are no......More
HOW MANY KINDS OF GULL ARE THERE?
- There are about 45 species of gull. They live in all parts of the world, but there are more species north of the equator. Gulls range in size from the little gull, which is only 28 cm long, to the great black-backed gull, a huge 65 cm long. Many......More
HOW DOES A GANNET CATCH ITS FOOD?
- The gannet catches fish and squid in spectacular dives into the sea. This graceful seabird flies over the water looking for prey. When it sees something, it plunges from as high as 30 m above the ocean, dives into the water with its wings swept......More
WHICH BIRD MAKES THE LONGEST MIGRATION?
- The Arctic tern makes the longest migration journey of any bird. Each year it makes a round trip of more than 35,000 km. The birds nest in the Arctic during the northern summer and then travel south to escape the northern winter, spending the......More
CAN ALL SEABIRDS SWIM?
- Not all seabirds can swim. Frigate birds cannot swim and avoid going into the water. They seize food from the surface or rob other birds of their catches. Storm petrels, too, rarely land on the water, preferring to swoop close to the......More
WHICH BIRD HAS THE LONGEST WINGS?
- The wandering albatross has the longest wings of any bird. When fully spread, they measure up to 3.3 m from tip to tip. This majestic seabird spends much of its life soaring over the ocean far from land and may travel many kilometres each day. It......More
CAN ALL CORMORANTS FLY?
- There are about 30 different kinds of cormorant and all but one can fly. The flightless cormorant lives in the Galapagos Islands off the coast of South America. It has tiny wings and cannot fly, but it is an expert swimmer. It catches all of its......More
IS A PUFFIN A KIND OF PENGUIN?
- No, puffins belong to a different family of birds, called auks. They live in the northern hemisphere, particularly around the Arctic. Auks are good swimmers and divers, like penguins, but can also fly. ...More
WHY DOES A PELICAN HAVE A POUCH?
- The pelican has a pouch to help it catch fish to eat. When the bird plunges its open beak into the water, the pouch fills up with water and fish. As it brings its head up again, the water drains from the pouch, leaving any fish behind to be......More
DO VULTURES HUNT AND KILL PREY?
- Vultures do not usually kill their prey. They are scavengers, feeding on animals that are already dead or have been killed by hunters such as lions. They have strong claws and beaks, and the bald head allows them to plunge into carcasses without......More
WHICH IS THE FASTEST FLYING BIRD?
- As it dives to catch other birds in the air, the peregrine falcon may move at about 320 km/h, faster than any other bird. The falcon circles above its victim before making its fast dive and killing the prey on impact. ...More
DO EAGLES REALLY CATCH SNAKES?
- Yes, serpent eagles feed mostly on snakes and lizards. The rough surface of the serpent eagle toes helps it hold on to slippery snakes. ...More
HOW CAN OWLS HUNT AT NIGHT?
- Owls have excellent sight, even in low light, and extremely sharp hearing. Even in complete darkness they can pinpoint where a sound is coming from and swoop. Owls also have special soft-edged wing feathers that make very little noise as they......More
DO EAGLES BUILD NESTS?
- Yes, and the nest made by the bald eagle is the biggest made by any bird. Some bald eagle nests are up to 5.5 m deep. They are used again and again, with the eagles adding more nesting material each year. ...More
WHICH IS THE BIGGEST BIRD OF PREY?
- The Andean condor is the biggest bird of prey in the world. It measures up to I 10 cm long and weighs up to 12 kg. Its huge wingspan is over 3 m across. ...More
WHAT DOES AN OSPREY EAT?
- The osprey feeds mostly on fish. When it sees something near the surface, it dives down towards the water and seizes the fish in its feet. The soles of its feet are covered with small spines to help it hold on to the slippery fish. ...More
HOW MANY KINDS OF OWL ARE THERE?
- There are 145 species of owl in two families. The barn owl family contains about 10 species and the true owl family about I 35 species. Owls live in most parts of the world, except a few islands. They usually hunt at night, catching small......More
WHICH IS THE BIGGEST EAGLE?
- The biggest eagle in the world is the great harpy eagle, from the rainforests of South America. It is up to I m long and has huge feet and sharp talons, which it uses to kill its prey. Unlike other eagles, the giant harpy does not soar high in......More
HOW DO EAGLES KILL THEIR PREY?
- An eagle kills with the four long, curved claws on each of its feet. It drops down on to its prey, seizes it in its long talons and crushes it to death. The eagle then tears the flesh apart with its strong hooked beak. ...More
WHY ARE MOST PLANTS GREEN?
- Most plants are green because they contain the green pigment chlorophyll in their stems and leaves. Sometimes the green pigment is masked by other colours, such as red. This means that not all plants that contain chlorophyll look green. ...More
HOW DO GREEN PLANTS FEED?
- Green plants make their own food in a process called photosynthesis. Chlorophyll helps to trap energy from the Sun. Plants use this energy to convert water and carbon dioxide into sugars and starch. ...More
HOW DOES A FLOWER FORM SO QUICKLY?
- When a flower opens out from a bud, it may appear like magic in just a day or even a few hours. This is possible because the flower is already formed in miniature inside the bud, just waiting to open out. If you cut open a flower bud, you can see......More
WHAT MAKES A SEED GROW?
- To grow, a seed needs moisture, warmth and air. Some seeds can only germinate (begin to grow) if they have first been in the low temperatures of winter. The seeds of some plants can lie dormant (inactive) for years before germinating. ...More
WHY DO SHOOTS GROW UPWARDS?
- Plants need water, mineral salts, and foods such as carbohydrates. Green plants make their own foods, while other plants may take in food from decaying plants or animals, or direct from other living plants. ...More
WHAT DOES A PLANT NEED TO GROW?
- Most shoots grow upwards, towards the sunlight. The growing tip of the shoot can detect the direction of the light, and chemicals are released that make it grow more on the lower or darker side, thus turning the shoot upwards. ...More
HOW DO PLANTS TAKE IN WATER?
- Plants use their extensive root systems to take in water from the ground. Each root branches into a network of rootlets, which in turn bear root hairs. Water passes into the root across the cell walls of millions of tiny root hairs. ...More
WHY DO ROOTS GROW DOWNWARDS?
- Roots generally grow downwards because they can detect the pull of gravity. The root responds to gravity by releasing chemicals that cause more growth on the upper side, thus turning the root downwards. ...More
HOW DOES A VENUS FLY-TRAP CATCH ITS PREY?
- The fly-trap is a carnivorous (meat-eating) plant that catches insects and other small animals. The trap is a flattened, hinged pad at the end of each leaf, fringed with bristles. When an insect lands on the pad and touches one of the sensitive......More
HOW MUCH SUGAR DOES PHOTOSYNTHESIS MAKE IN A YEAR?
- Plants turn the sugar they make by photosynthesis into other chemical compounds that they need for growth and development. They also use sugar to make energy. Some scientists have estimated that the total mass of green plants alive in the entire......More
HOW DOES A PARASITIC PLANT FEED?
- Parasitic plants do not need to make their own food, and many are not green. Instead, they grow into the tissues of another plant, called the host, and tap into its food and water transport system, taking all the nourishment they need from its......More
HOW FAST DOES SAP FLOW THROUGH A TREE?
- In warm conditions, with a plentiful supply of water to the roots, and on a breezy day, sap may flow through a tree as fast as 100 cm every hour. ...More
HOW ARE FLOWERS POLLINATED?
- Pollination is an important part of reproduction in plants. The pollen, containing the male sex cells, fertilizes the ovules, which are the female sex cells. This can happen in several ways. The flowers of many trees release masses of tiny pollen......More
WHICH FLOWERS LAST FOR ONLY ONE DAY?
- The flowers of morning glory open each morning and shrivel and die towards evening. Day lilies also produce flowers that last one day. ...More
CAN PLANTS REPRODUCE WITHOUT SEEDS?
- Some plants, such as mosses, liverworts and ferns, do not produce seeds. Instead, they spread by dispersing spores. But even among seeding plants, reproduction without seeds is possible. Many plants can reproduce vegetatively by sending out......More
WHAT HAPPENS IN A FLOWER AFTER POLLINATION?
- After pollination, the pollen that has landed on the stigma of another flower of the same species will begin to germinate, if conditions are right. It sends a tube down into the style and eventually into the ovary of the flower, which it enters......More
WHERE DO SEEDS DEVELOP?
- Each ovule is destined to become a seed, and develops inside the ovary of the flower. An ovule consists of the zygote, or fertilized egg, surrounded by the endosperm, the seed food store. ...More
WHICH PLANTS HAVE THE SMALLEST SEEDS?
- Orchids produce huge numbers of microscopic seeds that drift invisibly through the air. As many as two million seeds may be produced from a single orchid seedpod. ...More
WHY ARE MANY SEEDS POISONOUS?
- Many mammals and birds eat seeds. Some plants have seeds that are poisonous to mammals and birds, which prevents them being eaten. Poisonous seeds are often brightly coloured so the seed- eaters quickly learn to avoid them. ...More
HOW MUCH POLLEN DO FLOWERS MAKE?
- Flowers can produce enormous quantities of pollen. Some American ragweeds can produce one billion pollen grains, and each grain can travel more than 160 kilometre from its source - which is bad news for sufferers of hay-fever! ...More
WHICH FLOWERS ARE POLLINATED BY MAMMALS?
- The flowers of the African baobab tree are pollinated by bush babies and bats. ...More
HOW ARE SEEDS DISPERSED?
- Many seeds are dispersed by animals. Birds eat berries and pass out the tougher seeds unharmed in their droppings. Some fruit capsules have hooks that catch in animal fur and are transported that way. Both small and large seeds can be carried by......More
HOW MANY SEEDS CAN A PLANT PRODUCE?
- In the tropical forests of Central and South America, a single trumpet tree produces 9,000 seeds which are about 1.9 mm long. Many of these end up in the soil and germinate when there is a gap in the canopy. ...More
WHY DO FLOWERS OPEN IN SPRING AND SUMMER?
- In temperate regions, this is the best time of year to attract insect pollinators. Ideally, the flowers open as early as possible in the season so that they can use the warm summer to grow and develop their seeds. ...More
WHAT HAPPENS TO ALL THE LEAVES THAT FALL?
- Huge quantities of leaves fall each season from forest trees, but they do not build up on the woodland floor from year to year. The dead leaves are attacked, for example by fungi and bacteria, and break down, gradually becoming part of the soil.......More
WHAT LIVES IN A TREE?
- Trees provide homes for countless animals, and also for other plants. The tree leaves are eaten by the caterpillars of moths and butterflies and other insects, and many species of beetle lay their eggs in the tree bark. Birds select a fork in a......More
HOW DO FORESTS HELP IMPROVE THE AIR?
- They do this by releasing huge quantities of water vapour and oxygen into the atmosphere. Plants also absorb carbon dioxide, and help prevent this gas from building up to damaging levels. ...More
HOW DO PLANTS RECYCLE WATER?
- Plants help to return water to the air through the process of transpiration. This is when water evaporates from the stems and leaves of plants. Water enters the plant through its roots. A column of water moves up through the plant, from the roots......More
HOW DO PLANTS HELP US RECLAIM LAND?
- Several types of grass, including marram, can be planted on coastal dunes. Their roots anchor the sand and help to stop it blowing away. Plants can even begin to reclaim land contaminated by industrial poisons. Some species have evolved forms......More
HOW ARE PLANTS USED TO CLEAN UP SEWAGE?
- Sewage works use tiny algae and other microscopic organisms in their filter beds. These algae and other organisms feed on the pollutants in the water and help to make it clean. ...More
HOW CAN PLANTS BE USED TO HELP STOP EROSION?
- Erosion is when soil is loosened and removed by the action of natural forces such as wind and water. This can often be reduced or prevented by using plants. The roots of the plants trap the loose soil and stop it being blown away. ...More
HOW DO PLANTS MAKE THE SOIL MORE FERTILE?
- When plants die, they decompose, releasing the chemicals in their tissues into the surrounding soil. The mixture of rotting leaves and other plant material in the soil is called humus, and this makes the soil more fertile. ...More
WHAT IS THE NITROGEN CYCLE?
- Bacteria in the soil use nitrogen from the air and turn it into a form that plants can use. Plants then use the nitrogen in their cells to make many complex compounds. When animals eat plants, the nitrogen returns to the soil in their droppings.......More
HOW DO PLANTS COLONIZE BARE GROUND?
- Some plants can quickly colonize bare soil by germinating rapidly from lightweight, wind-blown seeds. Some colonizing plants spread by putting out runners, which split off, becoming new plants. ...More
HOW BIG IS THE LARGEST CACTUS?
- The largest of all cacti is the giant cactus or saguaro, of the southwestern USA and Mexico. A 125 year old saguaro can measure up to 15 m tall and weigh as much as 6 tonnes. ...More
WHICH IS THE COLDEST DESERT?
- Antarctica is sometimes called a cold desert, and is in fact extremely dry, because all its water is locked up as ice. The deserts of Central Asia - in Mongolia and western China - are chilled in winter by cold air from the Arctic. Even in......More
WHAT IS A DESERT?
- Deserts make up about a third of the land surface of the world. They are found wherever there is not enough water available to support much plant growth. Examples of deserts are the Sahara, Namib and Kalahari deserts in Africa; the Atacama in......More
WHICH IS THE DRIEST DESERT?
- Most areas of the Sahara have around 76 mm of rainfall in an average year, making this one of the driest deserts. Parts of the Atacama Desert in Chile are also very dry. Some years may pass there between rainfalls. ...More
WHICH IS THE HOTTEST DESERT?
- Parts of the Sahara and the Mojave Desert in North America experience extremely high temperatures. The average summer temperature may be over 40°C. In Death Valley in the Mojave Desert, USA, temperatures of 50°C have been recorded. ...More
WHAT LIVES IN A LARGE CACTUS?
- Cacti are home to a variety of wildlife. Their flowers are visited by butterflies and moths, and also by hummingbirds. Holes in cactus stems provide nest sites for desert rodents, and also for birds like the tiny elf owl. ...More
WHAT IS AN OASIS?
- An oasis is a place in the desert where water is in plentiful supply, such as at a pool permanently fed by a spring. Many plants can grow at an oasis, even in the heat of the desert. Date palms are commonly planted at oases, both for shade and to......More
HOW DO DESERT FLOWERS SURVIVE DROUGHTS?
- Many desert flowers live for only a short time, but survive as seeds in the desert soil. When the next rains fall, they trigger the seeds to germinate. ...More
HOW DEEP DO THE ROOTS OF DESERT PLANTS GO?
- Some desert plants have very long roots that can tap into deep underground water sources. Mesquite roots often grow as deep as 20 m in search of water. ...More
HOW DO RESURRECTION PLANTS SURVIVE THE DROUGHT?
- When conditions get very dry, the leaves of these plants shrivel up and turn brown. This cuts down the loss of water. When it rains, they turn green again. ...More
WHAT IS THE STRANGEST DESERT PLANT?
- Welwitschia is probably the strangest desert plant of all. It lives for centuries, growing very slowly and producing just two twisted leathery leaves. It lives in the coastal deserts of southwest Africa and gets its water mainly from sea......More
WHAT ARE LIVING STONES?
- Living stones are special desert plants from southern Africa. They have swollen leaves and grow low down among the sand and gravel of the desert surface, looking very much like small pebbles or rocks. It is only when they flower that they reveal......More
HOW DOES A CACTUS SURVIVE IN THE DESERT?
- Cacti have generally leafless, swollen stems that store water. Since they lack leaves, they do not lose much water through transpiration. Most cacti are spiny, which probably protects them from being eaten by hungry (and thirsty) desert......More
WHAT IS A JOSHUA TREE?
- The Joshua tree grows in the Mojave Desert, California, USA. It grows only about 10 cm a year, and its leaves can last for 20 years. The fibres inside the leaves can be used to make paper. ...More
WHY ARE SOME DESERTS EXPANDING?
- The Sahara is growing larger each year partly because the climate is getting gradually warmer, but mainly because the plant life on the edges of the desert has been destroyed by grazing animals. ...More
WHERE IS THE PAMPAS?
- The pampas stretches across Argentina, Uruguay and southeastern Brazil, on the lowlands around the River Plate. The pampas is the largest area of temperate grassland in the southern hemisphere. ...More
WHERE ARE THE STEPPES?
- The steppes - the grasslands of Asia - cover a huge swathe of country from eastern Europe, through southern Russia, right across Asia to Mongolia in the east. ...More
WHAT ANIMALS LIVE IN THE GRASSLANDS OF ASIA?
- Wild horses once grazed on the Asian steppe, along with antelopes and deer, but they are rare today. Many rodents live in the steppe, such as hamsters, voles, mice and sousliks (a kind of ground squirrel). ...More
HOW DO THE PLANTS SURVIVE FIRE?
- Some grassland plants survive fires by persisting as thickened roots, and sprouting again after the fire has passed. Others may die, but germinate again later, from seeds left behind in the soil. ...More
WHAT MAKES GRASSLAND?
- In temperate regions with warm or hot summers and cold winters, natural grassland develops in areas that don't have enough rainfall for trees and woods to grow. Many types of grasses dominate in these habitats. Mixed in with the grasses are......More
WHERE ARE GRASSLANDS FOUND?
- There are grasslands in Central Asia, North America, Argentina and southern Africa. The Asian grasslands are called the steppes, and the North American grasslands are the prairies. In Argentina they are called pampas, and in southern Africa the......More
WHAT ANIMALS LIVE IN THE GRASSLANDS OF SOUTH AMERICA?
- The animals of the pampas include the unusual mara (long-legged and hare-like) and of the plains viscacha (related to the chinchilla), as well as wild guinea pigs, giant anteaters, the maned wolf and the rhea - a large, flightless bird. ...More
HOW DO GRASSLAND FIRES START IN NATURE?
- Fires can start quite naturally, for example when lightning strikes dead or dying grass. If a wind is blowing, the sparks can quickly turn into a fire that begins to spread. Grassland fires are most likely in the summer months. ...More
WHY DO NOT TREES TAKE OVER THE GRASSLAND?
- Trees cannot survive easily in natural grassland areas, mainly because the rainfall is too low to support their growth. But in areas where the rainfall is higher, trees will gradually invade, unless they are chopped down or eaten by grazing......More
WHAT ANIMALS LIVE IN THE GRASSLANDS OF NORTH AMERICA?
- The original animals of the prairie were buffalo and deer, and smaller species such as ground squirrels and prairie dogs. The wild buffalo once numbered some 40 million, but they were almost wiped out by settlers. ...More
WHAT ARE GRASSLANDS USED FOR?
- Grasslands have long been used for grazing herds of domestic animals, especially bison. But because the soils are so fertile, much of the original prairie land has now been ploughed up and planted with crops, such as wheat and corn (maize). ...More
WHICH GARDEN FLOWERS COME FROM NATURAL GRASSLANDS?
- From the grasslands of Europe and Asia come flowers such as adonis, anemones, delphiniums and scabious. Flowers from the prairie grasslands of North America include the coneflower, sunflower and blazing star. ...More
WHERE ARE THE PRAIRIES?
- The prairies extend from central southern Canada, through the mid-west of the USA, right down into northern Mexico, to the east of the Rocky Mountains. The area is known as the Great Plains, reflecting the open, treeless expanse of natural......More
HOW DOES THE PLANT LIFE CHANGE AS YOU GO UP A MOUNTAIN?
- Conditions generally get harsher, the higher you go up a mountain, and the plant life reflects this. There may be temperate woodland in the lowlands, but as you climb, this changes, typically to coniferous woodland, then to mountain scrub, then......More
HOW DO SOME MOUNTAIN PLANTS REPRODUCE WITHOUT FLOWERS?
- Many mountain plants have dispensed with flowers because of the lack of insects to pollinate them, and reproduce vegetatively instead. For example, some grasses grow miniature plants where the flowers should be. These drop off and grow into new......More
WHY DO DIFFERENT PLANTS GROW ON DIFFERENT SIDES OF A MOUNTAIN?
- Different sides of a mountain have different climates. On the south side (or north side in the southern hemisphere), there is more sunshine and conditions are warmer, while on the other side the snow and ice stay on the ground much longer. ...More
WHAT LIMITS PLANT GROWTH IN THE MOUNTAINS?
- The climate changes as the land rises from valley to mountain. It gets colder with increased height, and also windier. There is also usually much less level ground in the mountains, and the soils are thinner. Other factors that influence plant......More
HOW DO MOUNTAIN PLANTS ATTRACT POLLINATORS?
- Many mountain plants have large, colourful flowers to attract the few insects that live there. Some, such as mountain avens, track the sun to warm their flowers, which attracts insects to sunbathe there. ...More
HOW CAN PLANTS SURVIVE THE SNOW AND ICE?
- Few plants can survive being completely frozen, but many can thrive under the snow. Snow acts like a blanket to keep the freezing ice and wind at bay, and saves the plants from being killed. Alpine grasses stay alive and green under the snow,......More
WHY IS IT COLDER IN THE MOUNTAINS?
- The Sun heats the ground and this heat is trapped close to the ground by the Earth atmosphere. As you go up a mountain, and rise above the zone in which the heat is held, the atmosphere becomes thinner and the air gets colder. It falls about......More
HOW DO MOUNTAIN HERBIVORES FIND THEIR FOOD?
- Many mountain mammals burrow under the snow and continue to feed on mountain plants even at high altitudes. Others, such as marmots, store fat in their bodies and hibernate during the winter. ...More
WHY ARE ALPINE FLOWERS SO POPULAR IN GARDENS?
- Many mountain plants, such as gentians and saxifrages, are known as alpines because they come from the alpine tundra. They are popular for their bright flowers, and also because they tend to grow well even in poor conditions, such as on a rock......More
HOW DO PLANTS SURVIVE THE COLD?
- Plants have evolved many different ways of surviving mountain conditions. Many grow close to the ground in cushion-like shapes, which keeps them out of the wind. Some have thick, waxy, or hairy leaves to help insulate them. ...More
WHAT IS THE TREE-LINE?
- Trees cannot grow all the way up a mountain, and the highest level for them is known as the tree-line. This varies according to the local climate of the region, but is about 1,800 m in the Alps. Trees at this level grow slowly and are often......More
WHY ARE MANY ARCTIC SHRUBS EVERGREEN?
- Many Arctic shrubs keep some or all of their leaves throughout the winter. Leaves formed in late summer stay on the plant, often protected by dead leaves formed earlier. Then as soon as the spring returns, the green leaves can begin to......More
WHAT IS THE TUNDRA LIKE?
- The most striking feature of the tundra is its total lack of trees. Woody plants cannot survive here unless they are very small - there is simply not enough warmth in the summer for their growth. The dominant plants are grasses and sedges, mosses......More
WHY ARE THERE MORE PLANTS IN THE ARCTIC?
- The Arctic is surrounded by land masses, from Canada and Greenland to northern Europe and Siberia, with many islands. These offer many open habitats for plant growth, especially in the summer. About 900 species are native to the Arctic......More
HOW DO SOME POLAR PLANTS MELT THE SNOW?
- Several Arctic and mountain plants that survive under the snow have dark coloured leaves and stems. When the Sun begins to shine, they absorb the heat and melt the snow around them. ...More
WHY DO MANY ARCTIC PLANTS HAVE SWOLLEN ROOTS?
- Many Arctic plants have swollen roots or underground stems. They contain food reserves in readiness for a quick spurt of growth in the following summer. ...More
WHY ARE MANY TUNDRA FLOWERS WHITE OR YELLOW?
- Most tundra flowers are pollinated by insects. However, there are relatively few bees this far north, and the main pollinators are flies. Flies cannot distinguish colours like bees can, so the flowers do not need to be so colourful. ...More
WHERE IS THE TUNDRA?
- The tundra lies north of the coniferous forest belt, in a band roughly following the Arctic Circle. It covers about 25 million square km, from Alaska, through Canada, Greenland, Iceland, across to northern Norway, Finland and Sweden and into......More
WHY ARE THERE SO FEW PLANTS IN THE ANTARCTIC?
- Reindeer (or caribou) survive the Arctic winter by foraging for food. They dig beneath the snow with their hooves and antlers to seek out tender lichens, mosses, sedges and grasses. ...More
WHAT PLANTS DO REINDEER EAT?
- Most of Antarctica is covered with snow and ice all year. Only the Antarctic Peninsula has habitats where plants can survive, because it is warmed by the sea. Only two kinds of flowering plant - a hair- grass and a cushion plant - are native to......More
WHAT IS PERMAFROST?
- Even where the surface soil in the Arctic thaws in the summer, further down it is permanently frozen. This icy layer is known as the permafrost. Because the ice prevents rain water seeping further down, the surface can be wet. ...More
WHAT IS THE MOST NORTHERLY FLOWER?
- A species of poppy has been found growing further north than any other flower, at 83°N, or on a level with the north of Greenland. ...More
WHAT IS THE TEMPERATE FOREST LIKE IN SUMMER?
- In summer the temperate deciduous forests are humming with life - birds and insects call from the trees, mice and voles rustle in the undergrowth, and plant growth is at its height. The leaf canopy is fully developed, cutting out much of the......More
WHAT IS THE TEMPERATE FOREST LIKE IN WINTER?
- In winter, the tall trees forming the woodland canopy have lost all their leaves, the insects are quiet - most have either died or gone into hibernation - and there is not so much bird song. Many of the loudest songbirds are summer visitors and......More
WHICH FOREST TREE CAN BE TRACKED DOWN BY ITS SOUND?
- The leaves of the aspen tree move from side to side in the wind and rustle against each other, even in the lightest breeze. So the practised ear can easily track down an aspen. ...More
HOW OLD CAN FOREST TREES GET?
- Many forest trees reach a great age, notably oaks, which live between 200 and 400 years. Most elms live to about 150 years. ...More
HOW ARE TEMPERATE FORESTS HARVESTED FOR WOOD?
- Many temperate forests are not natural, but have been managed for centuries to provide timber. Traditional management involves a rotation of timber extraction, with only a proportion of the tree being removed at one time. This allows the forest......More
WHAT ELSE DO WE GET FROM TEMPERATE FORESTS?
- Lots of things! Charcoal is made by slowly burning certain kinds of wood. In the past, people depended upon woodland animals such as wild boar and deer for food and skins. Many edible fungi, including chanterelle, penny-bun and truffles grow in......More
WHY DO TREES LOSE THEIR LEAVES IN AUTUMN?
- Trees and other plants that lose their leaves all at once each year are known as deciduous. Most lose their leaves in the autumn, and remain bare through the winter. This way they shut down their main life processes - transpiration and......More
WHAT LIVES ON THE FOREST FLOOR?
- Invertebrates thrive in the dead leaves, twigs, fungi and roots of the woodland floor. Beetles, woodlice, worms, slugs, snails, springtails, ants, mites and millipedes, to name but a few, help break down the organic material, as well as providing......More
WHY DO MOST WOODLAND FLOWERS APPEAR IN SPRING?
- By developing early, they can benefit from the sunlight before it is shut out by the trees. Insects, which help to pollinate flowers, may also find it easier to spot them before the rest of the vegetation grows. ...More
WHICH CONIFER IS DECIDUOUS?
- Larch is a coniferous tree - it bears cones. But unlike most conifers, larch loses its leaves all at once, in the autumn, so it is also deciduous. In fact, there are also broadleaved trees that are evergreen, such as the oaks of the Mediterranean......More
HOW MUCH RAIN FALLS IN THE RAINFOREST?
- The tropical rainforests are warm and wet. In many, the rainfall is more than 2,000 mm per year. It may rain at any time of the day, but there are often storms in the afternoon. ...More
WHAT ARE LIANES?
- Lianes, or lianas, are plants that clamber over and dangle down from rainforest trees. They grow very long and use the trees as supports. Animals such as monkeys and squirrels use lianes to help them move about in the branches. ...More
HOW RICH ARE THE RAINFORESTS?
- They are the richest habitats on earth, containing SO per cent of the world plants. Just 2.S acres of tropical rainforest can contain 600 species of trees. The forests also contain untold riches in the shape of timber, fruits and herbs that can......More
WHY ARE THE TROPICAL RAINFORESTS SO RICH IN SPECIES?
- No one knows for certain, but it may be because they have been undisturbed for so long, and also perhaps because they have such a stable, warm climate. ...More
WHAT IS AN AIR-PLANT?
- An air-plant grows without anchoring itself to the ground. Air plants are common in some tropical forests. They get the moisture they need direct from the damp air. ...More
WHERE ARE THE RAINFORESTS?
- The world largest rainforest is around Brazil Amazon River, and also along the foothills of the Andes Mountains. The world main areas of tropical rainforest are in South and Central America, in West and Central Africa, in Southeast Asia and in......More
WHAT DO WE GET FROM RAINFORESTS?
- We get many things from rainforests, including timber, Brazil nuts, fruit, rubber, rattan (a kind of palm from which furniture is made), cosmetics and medicines. ...More
WHICH PLANTS CAN TRAP THEIR OWN RAIN WATER?
- It rains very often in the tropical rainforest, and many plants trap the water before it reaches the ground. Bromeliads have special leaves that form a waterproof cup for this purpose. ...More
WHAT STOPS THE TALL TREES FROM BLOWING OVER?
- Many of the taller forest trees have special supporting flanges near the base of their trunks, called stilts or buttresses. These make the tree less liable to be pushed over in a storm. ...More
WHY ARE RAINFORESTS BEING CUT DOWN?
- Many rainforests are destroyed so the land can be used for crops, or for grazing. Tropical forest soils are fertile, and many crops, such as cocoa and sugar cane, can be grown after the trees have been felled. However, the fertility of the soil......More
HOW FAST ARE THE RAINFORESTS BEING DESTROYED?
- Rainforests are being destroyed at a speed of 28 hectares (70 acres) a minute. Every year an area the size of the state of Wisconsin is lost or badly damaged. When the forest is cleared, the tropical rainstorms work directly on the soil, erosion......More
HOW TALL ARE THE BIGGEST RAINFOREST TREES?
- The main canopy of the rainforest develops at around 30 m, with occasional taller trees (known as emergents) rising above these to an incredible 50 m or more. ...More
HOW DO WATER PLANTS STAY AFLOAT?
- Even though their growth is mainly below the surface, most water plants hold their flowers above the water, for pollination by the wind or by insects. Some, like the water starwort, have water-resistant floating pollen that drifts to the female......More
HOW DO WATER PLANTS DISPERSE THEIR FRUITS?
- The running water of streams and rivers carries floating fruits along, and there is usually some water movement even in ponds and lakes. Many floating fruits have tough coats that stop them from germinating too soon, so that they can travel a......More
HOW ARE WETLANDS DAMAGED?
- When soil is drained, or too much water is pumped from the land nearby, wetlands suffer as the water-table is lowered. They are easily damaged by pollution as well. Sewage and chemicals released from factories find their way into streams, where......More
WHY DO MOST WATER PLANTS GROW ONLY IN SHALLOW WATER?
- Most plants need to root themselves in the soil, even if they live mainly submerged in the water. In deep water there is not enough sunlight for plants to grow successfully. ...More
HOW DO RIVER PLANTS COPE WITH THE CURRENT?
- In the current of fast rivers, tiny algae encrust stones on the river bed. In slower currents by the bank, river plants anchor themselves firmly with roots. They tend to grow narrow ribbon- or strap-like leaves that offer little resistance to the......More
HOW DOES THE BLADDERWORT FEED?
- Bladderwort is a carnivorous plant found in boggy pools. The underwater stems develop small bladders, each with a trigger. When a small animal, such as a water flea, bumps into the trigger, the bladder springs open, sucking in the animal with the......More
WHY IS THE WATER HYACINTH SOMETIMES A PROBLEM?
- Water hyacinth is a floating plant with beautiful mauve flowers. However, it is also a fast- growing weed, and can spread rapidly to choke waterways, alter the ecology and impede boat traffic. ...More
WHY DO SOME LAKES HAVE VERY FEW PLANTS?
- Lakes vary in the chemical composition of their water. Some lakes, such as those draining from lime-rich soils, are very fertile and can support a lot of plants. Others, especially those whose water is acid (as in granite areas), are poor in......More
WHAT IS PAPYRUS?
- Papyrus is a tall sedge that grows along rivers and in swamps. It was used in ancient Egypt from about 3000 BC to make paper, but the plant is rare there today. ...More
WHAT FOOD PLANTS COME FROM WETLANDS?
- The most important wetland crop is rice, which is grown in many parts of the world, notably India and China. It grows best in flooded fields called paddies. Another aquatic grass crop is Canadian wild rice, a traditional food of Native Americans,......More
HOW DOES A LAKE TURN INTO LAND?
- Over time, a lake will gradually turn into dry land by a process called succession. Slowly, the remains of the plants growing in the shallows accumulate, making the water more and more shallow. Eventually, the edges of the lake dry out and land......More
WHAT IS THE AMAZON COW-TREE?
- The Amazon cow-tree is a tropical fig. It takes its name from the fact that it produces a milk-like sap, or latex, which can be drunk just like cow milk. ...More
WHICH TREES GIVE US A SWEET, SUGARY SYRUP?
- The sugar maple has a sweet sap, which is harvested to make maple syrup. Most maple syrup comes from the province of Quebec, in Canada. ...More
WHAT ARE THE MOST IMPORTANT FOOD CROPS?
- Some 12,000 species of plant are known to have been used as food by people, and about 150 of these are in regular cultivation. The most important crops are the cereals - wheat, rice and maize (corn), followed by barley, sorghum, oats, millet and......More
WHICH FRUITS ARE GROWN FOR FOOD?
- Fruits of the temperate regions include apples, pears, grapes, plums, cherries, red and black currants, strawberries, raspberries, blackberries and gooseberries. In warmer regions, there are citrus fruits such as oranges, grapefruits, lemons and......More
WHICH PLANTS GIVE US OIL?
- The seeds of many plants are rich in oil, which they store as a source of food and energy. We extract oil from several of these plants, including olive, sunflower, corn (maize), soya bean, peanuts, oil- seed rape, sesame and African oil......More
HOW IS TEA MADE?
- Tea comes from the leaves of a camellia grown on hillsides in India, Sri Lanka, Indonesia, Japan and China. The young leaf tips are harvested, dried and then crushed to make tea. ...More
WHERE DOES COFFEE COME FROM?
- The coffee plant is a large shrub, and its berries are used to make coffee. The ripe berries are harvested, then dried to remove the flesh from the hard stones inside. These are the coffee "beans", which are then treated further, often......More
WHERE WERE POTATOES FIRST GROWN?
- Potatoes grow wild in the Andes Mountains of South America and were first gathered as food by the native people of that region. All the many varieties grown today derive from that wild source. ...More
HOW IS CHOCOLATE MADE?
- The cacao tree comes originally from the lowland rainforests of the Amazon and Orinoco. The fruits, called pods, develop on the sides of the trunk, and each pod contains about 20 to 60 seeds - the cocoa "beans". The beans must be......More
WHICH PLANTS ARE USED TO MAKE SUGAR?
- The main source of sugar is the sweet stems of sugar cane, a tall grass that grows in tropical countries. In some temperate areas, including Europe, there are large crops of sugar beet. This plant stores sugar in its thickened roots. In some......More
WHERE DID WHEAT COME FROM?
- Wheat is one of the oldest known crops. It was probably first cultivated over 6,000 years ago in Mesopotamia - present-day Iraq - between the rivers Tigris and Euphrates. Many useful crop plants have their origin in the Middle East. Other......More
WHAT IS BREADFRUIT?
- Breadfruit is a tree native to the Malay Archipelego. It grows to about 20 m, and has large edible fruits. The fruits are up to 20 cm across and are cooked before being eaten as a vegetable. The related jackfruit, from India and Malaysia, also......More
WHICH COUNTRIES USE MAINLY HERBAL MEDICINES?
- In much of the world, especially in China and India, herbal remedies are used more than any other kind of medicine. Plants have been used as medicine for at least 100,000 years. As long ago as 3000 BC, the Chinese had identified over 350......More
WHAT LINKS WILLOW TREES WITH ASPIRIN?
- Willow twigs were once chewed to give pain relief. A compound similar to the drug aspirin was once extracted from willow bark, as well as from the herb meadowsweet. Meadowsweet used to be known as spiraea-hence the name aspirin. ...More
HOW CAN A DEADLY OPIUM POPPY SAVE LIVES?
- Many useful medicinal plants can also yield dangerous drugs, and the beautiful pink-purple opium poppy is no exception. This poppy is a source of morphine, which is widely used as an anaesthetic. It is also a source of codeine, which is used in......More
WHAT IS GINSENG?
- Ginseng is a plant related to ivy, and has been used in herbal medicine for centuries. It is claimed to help many conditions, including fatigue and depression, kidney disease, heart problems and headaches. ...More
CAN PLANTS HELP FIGHT CANCER?
- Several plants are known to be effective against cancer tumours. One of the most famous is the rosy periwinkle. One of its chemical extracts, vincristine, is very effective against some types of leukaemia, a cancer of the blood. ...More
WHAT ARE COCA AND COLA?
- A world-famous fizzy drink originally contained extracts of two South American plants called coca and cola. The seeds of cola are chewed as a pick-me-up, because they contain caffeine. Coca is the source of the powerful anaesthetic cocaine, which......More
WHICH PLANTS HELP WITH BREATHING PROBLEMS?
- Lungwort is a herb with purple flowers and spotted leaves. It is used to treat asthma and catarrh. Ephedrine, from the ephedra or joint-pine plant, is used to treat asthma and hay fever. ...More
WHICH HERB IS USED TO TREAT HEADACHES?
- Feverfew is a pungent plant belonging to the daisy family. It takes its name from its long use as a remedy for fevers, and it has also been proven to be effective against headaches. ...More
WHAT LINKS YAMS WITH BIRTH CONTROL?
- Wild yams provided the medicines for the first contraceptive pills. Both the female and male sex hormones can be prepared using extracts of yam, and the first birth- control pills were made using this natural plant extract. ...More
WHAT PLANTS AID DIGESTION?
- Many plants, including the herbs and spices used in cooking, are used to help digestion. In Europe, the very bitter extract of wild gentians provides a good remedy for digestive problems. Plantain is another herb used for this purpose. ...More
WHICH PLANT HELPS COMBAT MALARIA?
- Quinine, from the bark of the quinine tree, which grows in the South American Andes, can cure or prevent malaria. Before the widespread use of quinine, malaria used to kill two million people each year. ...More
WHAT MEDICINE COMES FROM DEADLY NIGHTSHADE?
- Deadly nightshade has bright juicy berries, which are very poisonous. However, they can be used to prepare the chemical atropine, which is used to dilate the pupil of the eye in medical examinations. ...More
HOW MANY THINGS CAN YOU SPOT IN THIS PICTURE THAT HAVE BEEN MADE FROM PLANT MATERIALS?
- We make all kinds of things from plant materials. Wood alone is used to make countless objects, big and small, from construction timbers to musical instruments. All kinds of cloth are also made from plants - and so is the paper you are looking......More
HOW MANY THINGS CAN BE MADE FROM BAMBOO?
- Bamboo is one of the world most useful natural plant products. It is used for scaffolding and building houses, and for making paper, furniture, pipes and tubes, walking sticks, and (when split) for mats, hats, umbrellas, baskets, blinds, fans and......More
WHAT IS JOJOBA?
- Jojoba is a low-growing bush found in Northern Mexico. The fruits have a high-grade oily wax. It is used as a lubricant, in printing inks, and in body lotions and shampoo. ...More
WHAT IS BALSA?
- Balsa is the world lightest timber - it floats high in water. Balsa trees grow in tropical America. Balsa wood is used for making models such as airplanes, and also for rafts, life-belts and insulation. ...More
WHAT IS RAFFIA?
- Raffia is a natural fibre made from the young leaves of the raphia palm, which grows in tropical Africa. Raffia is used in handicrafts such as basketry. ...More
WHAT WOOD MAKES THE BEST CRICKET BATS?
- The best cricket bats are made in northern India, from the timber of the cricket-bat willow, a form of white willow. The blade (the part the ball strikes) is made from willow, and the handle usually from a different wood or cane. ...More
WHAT IS KAPOK?
- Kapok is similar to cotton. It comes from the kapok tree, which is cultivated in Asia and can be as tall as 50 m. The fluffy seed fibres are used to stuff mattresses, jackets, quilts and sleeping bags. ...More
HOW IS CORK PRODUCED?
- Cork comes from a tree called the cork oak, which grows wild around the Mediterranean Sea and has been cultivated in Portugal, Spain and North Africa. The cork is the thick, spongy bark. It is stripped away from the lower trunk, then left to grow......More
CAN PLANTS PRODUCE FUEL TO RUN CARS?
- When tapped like a rubber tree, the copaiba tree of the Amazon rainforest yields an oil similar to diesel, at a rate of 18 litres every 2 hours. It can be used to run engines. The petroleum nut tree of southeast Asia produces a high-octane oil in......More
WHAT IS THE WORLD LONGEST SEAWEED?
- Giant kelp is a huge seaweed that forms underwater forests in the coastal waters of California, USA. Its fronds can be up to 65 m long, making it one of the tallest plants known. ...More
WHICH PLANT HAS THE LONGEST LEAF?
- The raphia palm of tropical Africa produces the longest known leaves. The stalk can be nearly 4 m and the leaf-blade almost 20 m long. ...More
HOW DEEP ARE THE DEEPEST ROOTS?
- Roots of a South African fig were found to have penetrated 120 m below the surface. ...More
WHAT IS THE OLDEST PLANT?
- The oldest known plant may be the creosote bush. It grows in southwestern USA and Mexico. Some of these bushes are thought to be 11,700 years old. The bristlecone pine, which grows mainly in the southwestern USA, notably in the White Mountains of......More
WHAT PLANT CAN SPREAD ACROSS THE WIDEST AREA?
- The banyan of India and Pakistan often starts life as an epiphyte - a small plant growing on another tree. As it grows, it sends down woody roots that come to resemble tree trunks. Eventually it can cover a large area and seem like a grove of......More
WHAT IS THE SMALLEST FLOWERING PLANT?
- A tiny tropical floating duckweed is the world smallest flowering plant. Some species measure less than 0.5 mm across, even when fully grown. ...More
WHAT IS THE TALLEST TREE?
- The California redwood, which grows along the North American Pacific coast, is the tallest tree in the world, reaching 112 m. Some Australian eucalyptus trees can grow to 90 m. ...More
WHICH PLANT GROWS THE SLOWEST?
- The record for the slowest- growing plant probably goes to the dioon plant. The dioon grows in Mexico, and one specimen was recorded to have an average growth rate of 0.76 mm per year. ...More
WHICH PLANT GROWS THE FASTEST?
- The giant bamboo of Myanmar grows at up to 0.3 m per day, making it one of the fastest growing of all plants. However, another species from India, the spiny bamboo, holds the record for growth in a greenhouse - it achieved 91 cm in one day. ...More
WHAT IS THE LARGEST SEED?
- The coco de mer of the Seychelles has the largest seeds, each weighing up to 22 kg. They are produced inside a large, woody fruit that takes six years to develop. ...More
WHICH PLANT HAS THE LARGEST FLOATING LEAVES?
- The giant waterlily of the Amazon region has huge leaves. They grow up to 1,8 m across, and can support the weight of a child. ...More
WHAT IS THE LARGEST
- The world largest flower grows on the raffiesia, a plant without leaves that thrives in the tropical forests of Southeast Asia. It is a parasite, growing on the stems of lianes in the forest. Individual flowers can measure up to 91 cm across,......More
HOW IS EARTH HISTORY DIVIDED UP?
- Scientists divide the last 590 million years of Earth history into three main eras: the Paleozoic (meaning "old life") era, the Mesozoic ("middle life") era, and the Cenozoic ("new life") era. The eras are subdivided......More
WHAT WAS THE EARTH LIKE AFTER IT FORMED?
- The Earth surface was probably molten (hot and liquid) for many millions of years after its formation. The oldest known rocks are about 3,960 million years old. ...More
WHEN DID LIVING THINGS FIRST APPEAR ON EARTH?
- The oldest known fossils (of microscopic bacteria) are about 3,500 million years old. Primitive life forms may have first appeared on Earth about 3,850 million years ago. ...More
WHEN DID PLANTS START TO GROW ON LAND?
- The first land plants appeared in the Silurian period. Plants produced oxygen and provided food for the first land animals - amphibians. Amphibians first appeared in the Devonian period. ...More
WHEN DID MAMMALS FIRST APPEAR?
- Mammals lived on Earth from at least the start of the Jurassic period. But they did not become common until after the extinction of the dinosaurs. ...More
WHEN DID PEOPLE FIRST LIVE ON EARTH?
- Hominids (ape-like creatures that walked upright) first appeared on Earth more than four million years ago. But modern humans appeared only about 100,000 years ago. ...More
WHAT WERE THE FIRST ANIMALS WITH BACKBONES?
- Jawless fishes were the first animals with backbones. They appeared during the Ordovician period. Fishes with skeletons of cartilage, such as sharks, first appeared in the Devonian period. ...More
WHY DID THE DINOSAURS BECOME EXTINCT?
- The Dinosaurs first appeared on Earth during the Triassic period. They became the dominant animals during the Jurassic period, but at the end of the Cretaceous period, 65 million years ago, they became extinct. Scientists still argue about why......More
WHY IS THE CAMBRIAN PERIOD IMPORTANT?
- During the Precambrian, most living creatures were soft-bodies and left few fossils. During the Cambrian period, many creatures had hard parts, which were preserved as fossils in layers of rock. ...More
WHAT ARE PLATES?
- The Earth hard outer layers are divided into large blocks called plates. These consist of the Earth crust and the top part of the mantle. ...More
HOW DEEP ARE THE PLATES?
- There are about seven large plates. Their exact thickness is uncertain but they could be up to 145 km in places. ...More
CAN PLATES MOVE SIDEWAYS?
- Plates not only move apart or push against each other, they can also move sideways along huge cracks in the ground called transform faults. ...More
WHAT HAPPENS WHEN PLATES COLLIDE?
- If this happens along a deep ocean trench, one plate is pulled beneath another, and is melted and recycled. On land, when continents collide, their edges are squeezed up into new mountain ranges. ...More
HOW FAST DO PLATES MOVE?
- Plates move, on average, between 4 to 7 cm a year. This may sound slow. But over millions of years, these small plate movements dramatically change the face of the Earth. ...More
WHO FIRST SUGGESTED THE IDEA OF CONTINENTAL DRIFT?
- In the early 1900s, an American, F.B. Taylor, and a German, Alfred Wegener, both suggested the idea of continental drift. But scientists could not explain how the plates moved until the 1960s, following studies of the ocean floor. ...More
HOW DO EARTH PLATES MOVE APART?
- Earth plates float on a partly molten layer within the mantle. Currents in the partly molten rocks slowly move the plates around. Where the plates are moved apart, liquid rock, called magma, rises and plugs the gaps. When the magma hardens, it......More
HOW DO VOLCANIC ISLANDS FORM IN THE MIDDLE OF OCEANS?
- Volcanic islands form when magma rises from the mantle. Lava (the name for magma when it reaches the surface) piles up until it emerges above sea level. ...More
HAVE FOSSILS HELPED TO PROVE CONTINENTAL DRIFT?
- Fossils of animals that could not possibly have swum across oceans have been found in different continents. This suggests that the continents were once all joined together and that animals could walk from one continent to another. ...More
HAS THE EARTH ALWAYS LOOKED THE SAME?
- If aliens had visited Earth 200 million years ago, they would have seen only one huge continent, called Pangaea, surrounded by one ocean. Around 180 million years ago. Pangaea began to break up. By 135 million years ago, a plate bearing South......More
WHEREARE EARTHQUAKES LIKELY TO HAPPEN?
- Earthquakes can occur anywhere, whenever rocks move along faults (cracks) in the ground. But the most violent earthquakes occur most often around the edges of the plates that make up the Earth hard outer layers. For most of the time, the......More
HOW DO EARTHQUAKES CAUSE DAMAGE?
- Powerful earthquakes shake the ground. They make buildings sway and wobble until they collapse. The shaking sometimes breaks gas pipes or causes electrical short-circuits, starting fires. Earthquakes on high mountain slopes cause landslides that......More
WHAT INSTRUMENTS RECORD EARTHQUAKES?
- Seismographs are sensitive instruments that record earthquakes. The shaking of the ground is recorded by a pen that marks the movements on a revolving drum. ...More
DO EARTHQUAKES AND VOLCANOES OCCUR IN THE SAME PLACES?
- Yes, most active volcanoes occur near the edges of plates that are moving apart or colliding. Earthquakes are common in these regions too. ...More
WHAT IS THE SAN ANDREAS FAULT?
- The San Andreas fault is a long transform fault in California, USA. Movements along this plate edge have caused huge earthquakes in the cities of San Francisco and Los Angeles. ...More
WHICH EARTHQUAKE IN MODERN TIMES CAUSED THE MOST HARM?
- In 1976, an earthquake struck Tang Shan in China. An estimated 240,000 people died. a further 500,000 were injured. ...More
CAN SCIENTISTS PREDICT EARTHQUAKES?
- In 1975, Chinese scientists correctly predicted an earthquake and saved the lives of many people. But scientists have not yet found a sure way of forecasting them. ...More
CAN ANIMALS SENSE WHEN AN EARTHQUAKE IS ABOUT TO HAPPEN?
- Scientists have noticed that animals often behave strangely before an earthquake. Horses rear up, dogs bark and snakes come out of holes in the ground. ...More
WHAT MAKES VOLCANOES ERUPT?
- Volcanoes erupt when hot molten rock from deep down in the Earth mantle rises through the Earth hard outer layers and reaches the surface. The molten rock is called magma, but when it reaches the surface, it is called lava. Most volcanoes occur......More
WHAT ARE HOT SPOTS?
- Some volcanoes lie far from plate edges. They form over "hot spots" - areas of great heat in the Earth mantle. Hawaii in the Pacific Ocean is over a hot spot. ...More
WHAT ARE HOT SPRINGS AND GEYSERS?
- These are places where underground water, heated by magma inside the Earth, breaks through to the surface. Warm water bubbles up at hot springs. Geysers hurl boiling water and steam into the air. ...More
WHAT IS AN EXTINCT VOLCANO?
- Volcanoes that have not erupted in recorded history are said to be "extinct". This means that they are not expected to erupt ever again. ...More
DO ALL VOLCANOES ERUPT IN THE SAME WAY?
- No, they don't. Volcanoes can explode upwards or sideways, or erupt "quietly". Trapped inside the magma in explosive volcanoes are lots of gases and water vapour. These gases shatter the magma and hurl columns of volcanic ash and......More
DO VOLCANOES DO ANY GOOD?
- Volcanic eruptions cause tremendous damage, but soil formed from volcanic ash is extremely fertile. Volcanic rocks are also used in building and chemical industries. ...More
WHAT IS A DORMANT VOLCANO?
- Some volcanoes erupt continuously for long periods. But other active volcanoes erupt only now and then. When they are not erupting, they are said to be dormant, or sleeping. ...More
WHAT ARE THE THREE MAIN KINDS OF ROCK?
- There are igneous, sedimentary and metamorphic rocks. Igneous rocks are formed from cooled magma. Sometimes it cools on the surface to form rocks such as basalt. Other magma cools underground to create rocks called granites. Many sedimentary......More
WHAT ARE ELEMENTS AND MINERALS?
- Earth crust contains 92 elements. The two most common elements are oxygen and silicon. Also common are aluminium, iron, calcium, sodium, potassium and magnesium. These eight elements make up 98.59% of the weight of the Earth crust. Some elements,......More
IS COAL A ROCK?
- No. Although coal is sometimes called an organic rock, it is not a proper rock as rocks are inorganic (lifeless). Coal, like oil and natural gas, was formed millions of years ago from the remains of once-living things. That is why coal, oil and......More
CAN MINERALS MAKE YOU INVISIBLE?
- No, although in the Middle Ages people thought that you would become invisible if you wore an opal wrapped in a bay leaf. ...More
WHAT IS THE HARDEST MINERAL?
- Diamond, a pure but rare form of carbon, is formed under great pressure deep inside the Earth. It is the hardest natural substance. ...More
WHAT ARE THE MOST VALUABLE MINERALS?
- Gemstones such as diamonds, rubies, sapphires and emeralds are valuable minerals. Gold and silver are also regarded as minerals, although they occur as free elements. ...More
WHAT ARE BIRTHSTONES?
- Birthstones are minerals that symbolize the month of a person birth. For example, garnet is the birthstone for January, while ruby is the stone for people born in July. ...More
WHAT ARE THE MOST COMMON ROCKS?
- Sedimentary rocks cover 75% of the Earth land surface. But igneous rocks make up 95% of the rocks in the top 16 km of the Earth crust. ...More
WHAT COMMON ROCKS ARE USED FOR BUILDINGS?
- Two sedimentary rocks, limestone and sandstone, and the igneous rock granite are all good building stones. The metamorphic rock marble is often used to decorate buildings. ...More
ARE SOME MINERALS MORE PLENTIFUL THAN OTHERS?
- Many useful minerals are abundant. Other less common, but important, minerals are in short supply and are often recycled from scrap. Recycling saves energy, which has to be used to process metal ores. ...More
WHAT ARE FOSSILS?
- Fossils are the impressions of ancient life preserved in rocks. When dead creatures are buried on the sea floor, the soft parts rot away, but the hard parts remain. Later, the mud and sand on the sea bed harden into rock. Water seeping through......More
WHAT IS AMBER?
- Amber is a hard substance formed from the sticky resin of trees. Tiny animals were sometimes trapped in the resin. Their bodies were preserved when the resin hardened. ...More
HAS FLESH EVER BEEN PRESERVED AS A FOSSIL?
- In Siberia, woolly mammoths, which lived more than 40,000 years ago, sank in swampy ground. When the soil froze, their complete bodies were preserved in the icy subsoil. ...More
WHAT ARE TRACE FOSSILS?
- Trace fossils give information about animals that lived in ancient times. Animal burrows are sometimes preserved, giving scientists clues about the creatures that made them. Other trace fossils include footprints preserved in hardened mud and......More
WHAT IS EOHIPPUS?
- Eohippus is the name of the dog-sized ancestor of the horse, which lived about 55 million years ago. Fossil studies of eohippus and its successors have shown how the modern horse evolved. ...More
HOW ARE FOSSILS TURNED TO STONE?
- When tree trunks or bones are buried, minerals deposited from water sometimes replace the original material. The wood or bone is then petrified, or turned to stone. ...More
HOW DO YOU DATE FOSSILS?
- Sometimes, dead creatures are found buried under volcanic ash. The ash sometimes contains radioactive substances that scientists can date. Hence, they can work out the time when the animals lived. ...More
WHAT IS CARBONIZATION?
- Leaves usually rot quickly after plants die. But sometimes they float to the bottom of lakes and are buried under fine mud. Sediments above and below the leaf are gradually compressed and hardened into sedimentary rocks. Over time, bacteria......More
WHAT WAS PILTDOWN MAN?
- Some bones, thought to be fossils of an early human ancestor, were discovered at Piltdown Common, England, between 1910 and 1912. But Piltdown man was a fake. The skull was human, but the jawbone came from an orang-utan. ...More
WHAT CAN SCIENTISTS LEARN FROM FOSSILS?
- From the study of fossils - known as palaeontology - scientists can learn about how living things evolved on Earth. Fossils can also help palaeontologists to date rocks. This is because some species lived for only a short period on Earth. So, if......More
WHAT ARE SPRINGS?
- Springs occur when ground water flows to the surface. Springs are the sources of many rivers. Hot springs often occur in volcanic areas, where the ground water is heated by magma. ...More
HOW DOES WEATHERING HELP SHAPE THE LAND?
- Weathering is the breakdown of rocks on the Earth surface. The wearing away of the rock limestone is an example of chemical weathering. Limestone consists mostly of calcium carbonate. This chemical reacts with rainwater, which contains carbon......More
WHAT IS GROUND WATER?
- Ground water is water that seeps slowly through rocks, such as sandstones and lime stones. The top level of the water in the rocks is called the water table. Wells are dug down to the water table. ...More
CAN THE SUN HEAT CAUSE MECHANICAL WEATHERING?
- In hot, dry regions, rocks are heated by the Sun, but they cool at night. These changes crack rock surfaces, which peel away like the layers of an onion. ...More
DOES WATER REACT CHEMICALLY WITH OTHER ROCKS?
- Water dissolves rock salt. It also reacts with some types of the hard rock granite, turning minerals in the rock into a clay called kaolin. ...More
WHAT ARE STALACTITES?
- Water containing a lot of calcium carbonate drips down from the ceilings of limestone caves. The water gradually deposits calcium carbonate to form hanging, icicle-like structures called stalactites. ...More
WHAT ARE POT-HOLERS?
- Pot-holes, or swallow holes, are holes in the ground where people called pot-holers can climb down to explore limestone caves. They are formed when the roofs of shallow caves collapse. ...More
WHAT ARE STALAGMITES?
- Stalagmites are the opposite of stalactites. They are columns of calcium carbonate deposited by dripping water, but stalagmites grow upwards from the floors of caves. ...More
WHAT IS BIOLOGICAL WEATHERING?
- Biological weathering includes the splitting apart of rocks by tree roots, the exposing and consequential weathering of rocks by burrowing animals, and the work of bacteria, which also helps to weather rocks. ...More
CAN PLANTS CHANGE THE LAND?
- Plant roots can break up the rock. When the seed of a tree falls into a crack in a rock, it develops roots that push downwards. As the roots grow, they push against the sides of the crack until the rock splits apart. ...More
HOW QUICKLY IS THE LAND WORN AWAY?
- Scientists have worked out that an average of 3.5 cm is worn away from land areas every 1,000 years. This sounds slow, but over millions of years, mountains are worn down to make plains. ...More
HOW DOES THE ACTION OF FROST BREAK UP ROCKS?
- At night in the mountains, people may hear sounds like gunshots. These are made by rocks being split apart by frost action (an example of mechanical weathering).As the water in cracks in the rocks freezes and turns into ice, it takes up nearly......More
WHERE DO RIVERS START?
- Some rivers start at springs, where ground water reaches the surface. Others start at the ends of melting glaciers or are the outlets of lakes. ...More
WHY DO WATERFALLS OCCUR?
- Waterfalls can occur when rivers cross hard rocks. When softer rocks downstream are worn away, the hard rocks form a ledge over which the river plunges in a waterfall. ...More
HOW DO RIVERS SHAPE THE LAND?
- Rivers sweep away weathered rocks and wear away the land. Young rivers push loose rocks down steep slopes. The rocks rub against river beds and deepen their valleys. The rocks rub against each other and break down into finer and finer pieces.......More
CAN SEA WAVES SHAPE COASTS?
- Large storm waves batter the shore. The waves pick up sand and pebbles, hurling them at cliffs. This hollows out the bottom layers of the cliff until the top collapses and the cliff retreats. Waves hollow out bays in soft rocks, leaving hard......More
WHAT ARE SPITS?
- Waves and currents transport sediments along coasts. In places where the coasts change direction, the worn sand and pebbles pile up in narrow ridges called spits. ...More
WHAT IS A BAY MOUTH BAR?
- Some spits join one headland to another. They are called bay mouth bars, because they can cut off bays from the sea, turning them into lagoons. ...More
WHAT ARE TRIBUTARY RIVERS?
- Tributary rivers are rivers that flow into a main river. This swells the amount of water in the main river and increases its load of worn material. ...More
DOES THE SEA WEAR AWAY THE LAND?
- Waves wear away soft rocks to form bays, while harder rocks on either side form headlands. Parts of the coast of northeast England have been worn back by up to 5 km since the days when the Romans ruled the area. ...More
HOW CAN PEOPLE SLOW DOWN WAVE EROSION?
- Along the beaches at many coastal resorts, structures are built at right angles to the shore. These breakwaters, slow down the movement of sand on the beaches by waves and sea currents. ...More
WHAT ARE DELTAS?
- Deltas are areas of sediments, made up of sand, mud and silt, that pile up around the mouths of some rivers. In many rivers, currents sweep the sediments into the sea. ...More
WHICH ARE THE WORLD LARGEST BODIES OF ICE?
- The largest bodies of ice are the ice sheets of Antarctica and Greenland. Smaller ice caps occur in the Arctic, while mountain glaciers are found around the world. ...More
WHAT ARE ERRATICS
- Erratics are boulders made of a rock that is different from the rocks on which they rest. They were carried there by moving ice. ...More
WHEN DID THE LAST ICE AGE TAKE PLACE?
- The last ice age began about 1.6 million years ago and ended 10,000 years ago. The ice age included warm periods and long periods of bitter cold. ...More
WHAT IS AN ICE AGE?
- During ice ages, average temperatures fall and ice sheets spread over large areas that were once ice-free. Several ice ages have occurred in Earth history. ...More
HOW DOES ICE SHAPE THE LAND?
- In cold mountain areas, snow piles up in hollows. Gradually the snow becomes compacted into ice. Eventually, the ice spills out of the hollows and starts to move downhill to form a glacier. Glaciers are like conveyor belts. On the tops of......More
HOW CAN WE TELL THAT AN AREA WAS ONCE COVERED BY ICE?
- Certain tell-tale features give this away. Mountain areas contain deep, steep-sided valleys that were worn out by glaciers. Armchair-shaped basins where glacier ice once formed are called cirques. Knife-edged ridges between cirques are called......More
WHAT ARE FIORDS?
- Fiords are deep, steep-sided valleys that wind inland along coasts. They were once river valleys that were deepened by glaciers during the last Ice Age. ...More
HOW MUCH OF THE WORLD IS COVERED BY ICE?
- Ice covers about 10% of the world land area. But during the last Ice Age, it spread over much of northern North America and Europe. The same ice sheet reached what is now New York City in America, and covered London. ...More
HOW DOES WIND--BLOWN SAND SHAPE SCENERY?
- In deserts, wind-blown sand is important in shaping the scenery. Winds lift grains of sand, which are then blown and bounced forward. Sand grains are heavy and seldom rise over 2 m above ground level. But, at low levels, wind- blown sand acts......More
WHAT ARE DUST STORMS?
- Desert winds sweep fine dust high into the air during choking dust storms. Wind from the Sahara in North Africa is often blown over southern Europe, carrying the pinkish dust with it. ...More
CAN WATER CHANGE DESERT SCENERY?
- Thousands of years ago, many deserts were rainy areas and many land features were shaped by rivers. Flash floods sometimes occur in deserts. They sweep away much worn material. ...More
WHAT ARE OASES?
- Oases are places in deserts that have water supplies. Some oases have wells tapping ground water. Sometimes, the water bubbles up to the surface in a spring. ...More
WHAT ARE WADIS?
- Wadis are dry waterways in deserts. Travellers sometimes shelter in them at night. But a freak storm can soon fill them with water and drowning can be a real danger. ...More
WHY DO PEOPLE IN DESERTS WEAR HEAVY CLOTHES?
- Deserts are often cold at night and heavy clothes keep people warm. Cloaks and headdresses help to keep out stinging wind-blown sand and dust, and prevent sunburn. ...More
WHAT IS DESERTIFICATION?
- Human misuse of the land near deserts, caused by cutting down trees and overgrazing grasslands, may turn fertile land into desert. This is called desertification. Natural climate changes may also create deserts. This happened in the Sahara about......More
HOW ARE SAND DUNES FORMED?
- The wind blowing across a desert piles the sand up in hills called dunes. Where the wind directions keep changing, the dunes have no particular shape. But when they blow mainly from one direction, crescent-shaped dunes called barchans form.......More
WHY ARE ICEBERGS DANGEROUS TO SHIPPING?
- Icebergs are huge chunks of ice that break off from glaciers. They float in the sea with nine-tenths of their bulk submerged, which makes them extremely dangerous to shipping. Icebergs from Greenland have sunk ships off the coasts of North......More
WHAT IT IS LIKE AROUND THE NORTH POLE?
- It is bitterly cold. The North Pole lies in the middle of the Arctic Ocean, which is surrounded by northern North America, Asia and Europe. Sea ice covers much of the ocean for most of the year. In spring, the sea ice is about 3 m thick in......More
WHERE ARE THE POLES?
- The Earth is always spinning on its axis, giving us day and night. The points at the ends of this axis are the North and South geographic poles. ...More
WHAT ANIMALS LIVE IN POLAR REGIONS?
- Penguins are the best known animals of Antarctica. Polar bears, caribou, musk oxen and reindeer are large animals that live in the Arctic region. ...More
WHAT ARE ICE SHELVES?
- Ice shelves are large blocks of ice joined to Antarctica ice sheet, but which jut out over the sea. When chunks break away, they form flat, table-topped icebergs. Some of them are huge. One covered an area about the size of Belgium. ...More
IS THE ICE AROUND THE POLES MELTING?
- In parts of Antarctica, the ice shelves began to melt in the 1990s. Some people think this shows that the world is getting warmer because of pollution. ...More
WHAT ARE MAGNETIC POLES?
- The Earth is like a giant magnet, with two magnetic poles. They lie near the geographic North and South poles, though their positions change from time to time. ...More
HOW THICK IS THE ICE IN ANTARCTICA?
- The South Pole lies in the cold and windy continent of Antarctica, which is larger than either Europe or Australia. Ice and snow cover 98% of Antarctica, although some coastal areas and high peaks are ice-free. The Antarctic ice sheet is the......More
WHERE DO THE WORLD NATURAL WONDERS OCCUR?
- The world natural wonders can be found in every continent, and some, such as Australia Great Barrier Reef, occur in the oceans. ...More
WHAT ARE NATURAL WONDERS?
- The ancient Greeks and Romans made lists of the Seven Wonders of the World. They were all made by people. But the Earth also has many natural wonders, created by the forces that continuously shape our planet. Most lists of natural wonders include......More
WHERE IS THE GREAT PEBBLE?
- The word Uluru is an Australian Aboriginal word meaning "great pebble". Also called Ayers Rock, it is the world biggest monolith (single rock). ...More
WHICH IS THE WORLD HIGHEST MOUNTAIN RANGE?
- The Himalayas, in Asia. It contains 96 of the world 109 peaks that are more than 7,315 m above sea level. One of these peaks is Mount Everest, the world highest mountain. ...More
WHICH MOUNTAINS LOOK LIKE DRAGON TEETH?
- Steep-sided hills made of limestone, found around the town of Guilin in southeastern China. Wearing away by rainwater has made them their strange shapes. ...More
HOW CAN WE PROTECT OUR NATURAL WONDERS?
- Many people work to protect natural wonders so that they can be enjoyed by people in the future. One important step in protecting them was made in 1872, when the world first national park was founded at Yellowstone, site of the famous geyser......More
WHICH IS THE WORLD MIGHTIEST RIVER?
- The Amazon River in South America contains far more water than any other river. Its river basin (the region it drains) is also the world largest. ...More
WHAT IS METEOR CRATER?
- Meteor Crater in Arizona, USA, is a circular depression. It resembles a volcanic crater, but was formed about 50,000 years ago when a meteor hit our planet. The crater is 1,275 m wide and 175 m deep. ...More
WHERE CAN YOU FIND SMOKE THAT THUNDERS?
- The local name of the beautiful Victoria Falls on the Zambezi River between Zambia and Zimbabwe is Mosi oa Tunya, meaning "smoke that thunders". ...More
WHAT IS THE GREAT BARRIER REEF?
- The Great Barrier Reef is the world longest group of coral reefs and islands. It lies off the northeast coast of Australia, and is about 2,000 km long. ...More
WHICH JAPANESE WONDER ATTRACTS PILGRIMS?
- Mount Fuji in Japan is a beautiful volcanic cone. Many people regard it as a sacred mountain - a dwelling place for the gods - and they make long pilgrimages to the top. ...More
WHERE IS THE MATTERHORN?
- The Matterhorn is a magnificent mountain on Switzerland border with Italy. It was created by glaciers wearing away the mountain from opposite sides. ...More
WHAT HAPPENS WHEN PEOPLE EXPLOIT THE EARTH?
- In many areas, people are changing the Earth and causing great harm through pollution. They are cutting down forests to produce farmland. But in some places, rain and winds wear away newly exposed soil, causing soil erosion and making the land......More
WHAT IS COASTAL POLLUTION?
- Coral reefs and mangrove swamps are breeding places for many fishes. The destruction or pollution of these areas is threatening the numbers of fishes in the oceans. ...More
CAN THEPOLLUTION OF RIVERS HARM PEOPLE?
- When factories pump poisonous wastes into rivers, creatures living near the rivers' mouths, such as shellfish, absorb poison into their bodies. When people eat such creatures, they, too, are poisoned. ...More
HOW HAVE PEOPLE TURNED SEA INTO LAND?
- In crowded countries, people sometimes turn useless coastal land into fertile farmland. The Netherlands is a flat country and about two-fifths of it is below sea level at high tide. The Dutch have created new land by building dykes (sea walls)......More
WHAT IS SOIL EROSION?
- Natural erosion, caused by running water, winds and other forces, is a slow process. Soil erosion occurs when people cut down trees and farm the land. Soil erosion on land made bare by people is a much faster process than natural erosion. ...More
WHAT IS AIR POLLUTION?
- Air pollution occurs when gases such as carbon dioxide are emitted into the air by factories, homes and offices. Vehicles also cause air pollution, which produces city smogs, acid rain and global warming. ...More
WHAT IS HAPPENING TO THE WORLD RAINFORESTS?
- The rainforests in the tropics are being destroyed. These forests contain more than half of the world living species. Many of them are now threatened with extinction. Huge forest fires in 1997 and 1998 destroyed large areas of rainforest. ...More
WILL GLOBAL WARMING AFFECT ANY ISLAND NATIONS?
- Coral islands are low-lying. If global warming melts the world ice, then sea levels will rise. Countries such as the Maldives and Kiribati could vanish under the waves. ...More
CAN DESERTS BE FARMED?
- In Israel and other countries, barren deserts have been turned into farmland by irrigation. The land is watered from wells that tap ground water, or the water is piped from far-away areas. ...More
WHAT IS THE BIGGEST CONTINENTS?
- Asia covers an area of 44,009,000 sq km. The other continents, in order of size, are Africa (30,246,000 sq km), north America (24,219,000 sq km), South America (17,832,000 sq km),Antarctica (14,000,000 sq km), Europe (10,443,000 sq km), and......More
WHERE IS THE WORLD LOWEST LAND?
- The shoreline of the Dead Sea, between Israel and Jordan, is 400 m below the sea level of the Mediterranean Sea. ...More
WHAT IS THE WORLD LARGEST ISLANDS?
- Greenland covers about 2,175,000 sq km. (Geographers regard Australia as a continent and not as an island.) ...More
WHICH IS THE DEEPEST LAKE?
- Lake Baikal, in Siberia, eastern Russia, is the world deepest lake. The deepest spot measured so far is 1,637 m. ...More
HOW MUCH OF THE WORLD IS COVERED BY LAND?
- Land covers about 148,460,000 sq km, or 29 % of the world surface. Water covers the remaining 71 %. ...More
WHAT IS THE WORLD LARGEST RIVER BASIN?
- The Amazon river basin in South America covers about 7,045,000 sq km. The Madeira River, which flows into the Amazon, is the world longest tributary, at 3,380 km. ...More
WHAT IS THE WORLD HIGHEST PEAK?
- Mount Everest on Nepal border with China reaches 8,848 m above sea level. Measured from its base on the sea floor, Mauna Kea, Hawaii, is 10,203 m high. But only 4,205 m appear above sea level. ...More
WHAT IS THE WORLD LARGEST BAY?
- Hudson Bay in Canada covers an area of about 1,233,000 sq km. it is linked to the North Atlantic Ocean by the Hudson Strait. ...More
WHAT IS THE WORLD LARGEST HIGH PLATEAU?
- The wind-swept Tibetan Plateau in China covers about 1,850,000 sq km. ...More
WHAT IS THE LARGEST INLAND BODY OF WATER, OR LAKE?
- The salty Caspian Sea, which lies partly in Europe and partly in Asia, has an area of about 371,380 sq km. The largest freshwater lake is Lake Superior, one of the Great Lakes of North America. Lake Superior has an area of 82,350 sq km. ...More
IS THERE A LAKE UNDER ANTARCTICA?
- Scientists have found a lake, about the size of Lake Ontario in North America, hidden under Antarctica. It may contain creatures that lived on Earth millions of years ago. ...More
WHERE DO MOST PEOPLE LIVE?
- The continent with the largest population is Asia, which has more than 3,000 million people. Europe ranks second in world population, followed by Africa, North America, South America and Australia. The continent of Antarctica has no permanent......More
WHICH IS THE WORLD LONGEST RIVER?
- The Nile in northeast Africa is 6,617 km long. The second longest river, the Amazon in South America, discharges 60 times more water than the Nile. ...More
WHAT IS THE WORLD LARGEST DESERT?
- The Sahara in North Africa covers an area of about 9,269,000 sq km. This is nearly as big as the United States. ...More
WHAT IS THE DEEPEST CAVE?
- The Reseau Jean Bernard in France is the deepest cave system. It reaches a depth of 1,602 m. ...More
HOW THICK IS YOUR SKIN?
- Skin covers the surface of the body at a thickness of around 1.4 to 4 mm. Skin has two layers. The outer skin that you see and touch is made of hard, tough cells of dead skin and is part of the epidermis. Below the epidermis is the dermis. It......More
WHAT DOES SKIN DO?
- Skin is a tough, stretchy covering that acts as a barrier between your body and the outside world. It stops the moisture inside the body from drying out and prevents dirt and germs from getting in. Tiny particles of melanin inside the epidermis......More
WHAT GIVES HAIR ITS COLOUR?
- The colour of your hair is determined mainly by the pigments (coloured substances) it contains. There are two kinds of pigment: melanin, which is very dark brown, and keratin, which is reddish- yellow.AII hair colour is formed by one or other or......More
WHAT ARE GOOSE BUMPS?
- Goose bumps are bumps on your skin formed by the tiny muscles that make the hairs on your skin stand up when you are cold. ...More
WHY DOES SKIN HAVE PORES?
- Skin has tiny holes, called sweat pores, to let out sweat and water vapour. When you are too hot, glands pump out sweat, which cools you as it dries. ...More
HOW DO NAILS GROW, AND HOW FAST DO THEY GROW?
- A fingernail grows about 1 mm every 7 days. As new nail forms behind the cuticle, under the skin, it pushes the older nail along. ...More
WHAT MAKES FINGERPRINTS UNIQUE?
- A fingerprint is made by thin ridges of skin on the tip of each finger and thumb. The ridges form a pattern of lines, loops or whorls, and no two people have the same pattern. ...More
WHY DOES HAIR FALL OUT?
- No hair lasts more than about six years. Every day you lose about 60 hairs, but since you have about 100,000 on your scalp, you hardly notice. After a while new hairs grow from the hair follicles. ...More
WHAT MAKES HAIR NATURALLY CURLY?
- How curly your hair is depends on the shape of the follicle - the tiny pit from which it grows. Curly hair grows from flat hair follicles, wavy hair from oval follicles and straight hair from round follicles. ...More
WHY DO OLD PEOPLE HAVE GREY HAIR?
- Some people hair stops making melanin as they grow older. Fair-haired people tend to go white, while dark-haired people usually go grey. Greyness is lack of melanin plus tiny air bubbles in the hair. ...More
WHAT ARE FRECKLES?
- Freckles are small patches of darker skin made by extra melanin. Exposure to sunshine increases the amount of melanin in the skin and the darkness of the freckles. ...More
WHY DO BODIES NEED BONES?
- Bones provide a strong framework that supports the rest of the body. Without bones, you would flop on the floor like an octopus! Some of the bones form a suit of internal armour, which protects the brain, the lungs, the heart and other vital......More
WHAT ARE LIGAMENTS?
- They are strong, bendy straps that hold together the bones in a joint. Nearly all the body joints have several ligaments. ...More
WHAT IS A VERTEBRA?
- A vertebra is a knobbly bone in your spine. The 33 vertebrae fit together to make a strong pillar, the spine, which carries much of your weight. At the same time the vertebrae allow your back to bend and twist. ...More
WHAT IS A JOINT?
- Where two bones meet, their ends are shaped to make different kinds of joint. Each kind of joint makes a strong connection and allows a particular kind of movement. For example, the knee is a hinge joint that lets the lower leg move only back and......More
WHY DO JOINTS NOT SQUEAK?
- Joints are cushioned by soft, squashy cartilage. Many joints also contain synovial fluid, which works like oil to keep them moving smoothly and painlessly. ...More
WHICH IS THE LONGEST BONE?
- The thigh bone in the upper part of the leg is the longest bone in the body. It accounts for more than a quarter of an adult height. ...More
WHICH JOINTS MOVE LEAST?
- Your skull is made up of more than 20 bones fused together in joints that allow no movement at all. These are called suture joints. ...More
WHICH JOINT MOVES THE MOST?
- The shoulder joint is a ball and socket joint and it allows the greatest amount of movement in all directions. ...More
WHICH IS THE SMALLEST BONE?
- The smallest bone is called the stirrup and is no bigger than a grain of rice. It is deep inside your ear and its job is to pass on sounds from the outer and middle ear to the inner ear. ...More
WHAT IS INSIDE A BONE?
- Inside a bone is a crisscross honeycomb of lighter bone. Blood vessels weave in and out of the bone, keeping the cells alive. ...More
WHAT DO THE MUSCLES DO?
- Muscles make parts of your body move. The skeleton is covered with muscles that move your bones and give your body its shape. Muscles in the face move your cheeks, eyebrows, nose, mouth, tongue and lower jaw. A different kind of muscle works in......More
WHY CAN NOT MOST PEOPLE MOVE THEIR EARS?
- Humans, like most other animals, have a muscle behind each ear. Animals can turn their ears to hear better, but most people never learn how to use their ear muscles. ...More
HOW DO MUSCLES WORK?
- Muscles work by contracting. This makes them shorter and thicker so that they pull on whatever bone or other part of the body they are attached to, thereby making it move. ...More
HOW MANY MUSCLES ARE THERE?
- You have about 650 muscles that work together. Most actions - including walking, swimming and smiling - involve dozens of muscles. Frowning uses 40 different muscles, but smiling is less energetic, using only 15. ...More
WHICH IS THE STRONGEST MUSCLE?
- The strongest muscle is the one that shuts your mouth! It is called the masseter, and you use it for talking and chewing up food. ...More
WHAT IS A TENDON?
- A tendon is like a tough rope that joins a muscle to a bone. If you bend and straighten your fingers, you can feel the tendons in the back of your hand. The body strongest tendon is the Achilles tendon, which you can feel above your heel. ...More
WHY DO MUSCLES WORK IN PAIRS?
- Muscles cannot push, they can only pull, and so you need two sets of muscles for many actions. For example, the biceps in your upper arm bends your elbow and you can feel it tighten when you clench your arm. To straighten the elbow again, you......More
WHY DOES EXERCISE MAKE MUSCLES STRONGER?
- A muscle is made of bundles of fibres that contract when you use the muscle. The more you use the muscle, the thicker the fibres become. They contract more effectively, which means the muscle is stronger. ...More
WHICH IS THE BIGGEST MUSCLE?
- The biggest muscle is the gluteus maximus in the buttock. You use it to straighten your leg when you stand up and it makes a comfortable cushion when you sit down. ...More
HOW FAST DO NERVES ACT?
- A nerve signal is a tiny pulse of electricity. It travels at about I m per second in the slowest nerves to more than 100 m per second in the fastest ones. ...More
HOW DOES A NERVE WORK?
- A chain of nerve cells carries a signal to or from the brain. The electrical impulse is received by the nerve endings and sent through the first nerve cell and along its nerve fibre to the nerve endings of the next nerve cell. ...More
WHAT DO THE NERVES DO?
- Nerves carry information and instructions to and from the brain and from one part of the brain to the other. Sensory nerves bring information from the eyes, ears and other sense organs to the brain, and motor nerves control the muscles. For......More
WHAT IS THE SPINAL CORD?
- The spinal cord is the largest nerve in the body. It is 2 cm wide and runs through the centre of the spine. It connects the nerves in the body with the brain. ...More
WHICH IS THE LONGEST NERVE?
- The longest nerve is the tibial nerve. It runs alongside the tibia (the shin bone). and in adults is 50 cm long. ...More
HOW MANY NERVES DO YOU HAVE?
- Thousands of millions of nerves reach out to all parts of the body. ...More
WHAT IS A REFLEX ACTION?
- A reflex action is something you do automatically. without thinking about it. Swallowing, blinking and choking are reflex actions. So is snatching your hand away from a hot plate. ...More
HOW DO ANAESTHETICS WORK?
- An anaesthetic stops you feeling. A local anaesthetic deadens the sensory nerves so that part of your body goes numb. A general anaesthetic puts you into a deep sleep so that none of your senses is taking in information. ...More
WHAT ARE THE BODY FIVE MAIN SENSES?
- The five main senses are seeing, hearing, smelling, tasting and touching. Between them, the five senses give you all the information you have about the outside world. Each sense has a special part of the body, called a sense organ, which reacts......More
WHAT CAUSES PINS AND NEEDLES?
- If a nerve gets squashed, it cannot carry nerve signals. If you kneel for a long time, your leg goes numb and then, when you stretch it, it tingles as the signals begin to flow again. ...More
WHY DO YOU NEED TO SLEEP?
- A 10-year-old sleeps on average nine or 10 hours a night, but sleep time can vary a lot between four and 12 hours. If you sleep for eight hours a night, that a third of your life! You need to sleep to rest your muscles and to allow your body time......More
WHY DO SOME PEOPLE SLEEP-WALK
- People may walk in their sleep because they are worried or anxious. If someone is sleep-walking, you should gently take them back to bed. ...More
WHAT DOES THE BRAIN DO?
- Your brain controls your body. It keeps the heart, stomach, lungs, kidneys and other vital organs working. The information collected by the senses is processed by different parts of the brain. Some is discarded, some is stored and some is reacted......More
WHAT DOES THE BRAIN LOOK LIKE?
- The brain looks soft and greyish pink. The top is wrinkled like a walnut and is covered with many tiny tubes of blood. The spinal cord links the brain to the rest of the body. ...More
WHY DO YOU REMEMBER SOME THINGS AND FORGET OTHERS?
- On the whole, you remember things that are important to you in some way. Some things need to be remembered for only a very short while. For instance, you might look up a telephone number, keep it in your head while you dial, and then forget it......More
WHY ARE SOME PEOPLE MORE ARTISTIC THAN OTHERS?
- One side of the brain deals more with music and artistic skills, and the other side with logical skills. How artistic or mathematical you are depends on which side of your brain is dominant (stronger). ...More
DOES THE BRAIN EVER REST?
- Even while you are asleep the brain carries on controlling body activities such as breathing, heartbeat and digestion. ...More
WHY ARE SOME PEOPLE LEFT-HANDED?
- Most people are right-handed - the left side of their brain is dominant. In left-handed people, the right side of the brain is dominant. The part of the brain that controls speech is usually on the dominant side. ...More
WHAT IS THE BRAIN MADE OF?
- The brain is a mass of pinkish-grey jelly-like tissue made of around 100 billion nerve cells and nerve fibres. ...More
HOW OFTEN DO YOU DREAM?
- You probably dream about five times every night, but you are only aware of dreaming if you wake up during a dream. ...More
WHAT DOES THE CEREBRAL CORTEX DO?
- The cortex is the wrinkly top part of the brain. It controls all the brain activity that you are aware of-seeing, thinking, reading, feeling and moving. Only humans have such a large and well developed cerebral cortex. Different parts of the......More
WHAT DOES THE SKULL DO?
- The skull is a hard covering of bone that protects the brain like a helmet.AII the bones of the skull except the lower jaw are fused together to make them stronger. ...More
HOW DO THE EYES SEE THINGS?
- You see something when light bounces off it and enters your eyes. The black circle in the middle of the eye is a hole, called the pupil. Light passes through the pupil and is focused by the lens onto the retina at the back of the eye. Nerve......More
WHAT MAKES YOU CRY?
- If dust or something gets into your eye, the tear gland above the eye releases extra tears to wash it away. Being upset can also make you cry. ...More
WHAT IS THE BLIND SPOT?
- The blind spot is a spot on the retina where the optic nerve leaves the eye. There are no light- sensitive cells here, making the spot "blind". ...More
WHY DO PEOPLE HAVE DIFFERENT COLOURED EYES?
- The iris is the coloured ring around the pupil. The colour is formed by a substance called melanin. Brown-eyed people have a lot of melanin, while blue-eyed people have very little. ...More
WHAT KEEPS THE EYE IN PLACE?
- The eyeball is held firmly in place by six muscles attached to the top, bottom and each side of the eye. These muscles work together to move your eyes so that you can look around. ...More
CAN SUNSHINE DAMAGE THE EYE?
- Sunshine contains ultraviolet rays, which can damage your eyes as well as your skin. You should wear sunglasses in bright sunlight and never, never look directly at the Sun. ...More
WHY DOES THE PUPIL CHANGE SIZE?
- The pupil becomes smaller in bright light to stop too much light from getting in and damaging the retina. In dim light the pupil opens to let in more light. ...More
HOW DO YOU SEE COLOUR?
- Different nerve cells in the retina react to the colours red, blue and green. Together they make up all the other colours. ...More
WHY DO YOU BLINK?
- You blink to clean your eyes. Each eye is covered with a thin film of salty fluid, so every time you blink, the eyelid washes the eyeball and wipes away dust and germs. The water drains away through a narrow tube into the nose. You also blink to......More
HOW BIG IS YOUR EYEBALL?
- An adult eyeball is about the size of a golf ball, but most of the eyeball is hidden inside the head. ...More
WHY CAN NOT YOU SEE COLOUR WHEN IT STARTS TO GET DARK?
- The cells that react to coloured light, called cones, only work well in bright light. Most of the cells in the eye see in black, white and grey, and these - called rods - are the ones that work at night. ...More
WHY DO YOU HAVE TWO EYES?
- Two eyes help you to judge how far away something is. Each eye gets a slightly different picture, which the brain combines into a single three-dimensional or 3D picture - one that has depth as well as height and breadth. ...More
WHAT ARE EYELASHES FOR?
- Your eyelashes help to protect your eyes by stopping dust and dirt getting blown into them. ...More
WHY DO YOU GET DIZZY?
- If you spin round and round and then stop, the world seems to carryon spinning. This is because the fluid in the semicircular canals is still moving as though you were still spinning. ...More
HOW DO EARS HELP YOU BALANCE?
- Three curved tubes in the inner ear help you to balance. They are filled with fluid and are called the semicircular canals. They are arranged at right angles to each other (like three sides of a box) so that as you move, the fluid inside them......More
WHY DO YOU HAVE TWO EARS?
- Two ears help you to detect which direction sounds are coming from. ...More
HOW DO YOU HEAR?
- Sound reaches your ears as vibrations in the air. The vibrations travel down the ear canal to the eardrum, which then vibrates, making the bones in the middle ear vibrate too. These three small bones make the vibrations bigger and pass them......More
IS LOUD NOISE DANGEROUS?
- Any noise over about 120 decibels can damage your hearing immediately, but, if you are constantly listening to sounds of 90 decibels or more, they can damage your hearing too. ...More
WHERE DOES THE EUSTACHIAN TUBE GO?
- This tube joins the middle ear to the empty spaces behind your upper throat. If mucus from a cold fills the tube, it stops you hearing as well as usual. ...More
HOW DO YOU MEASURE SOUND?
- The loudness of a sound is measured in decibels. The sound of a pin dropping is less than 10 decibels, and the hum of a refrigerator is about 35 decibels. A loud personal stereo makes about 80 decibels. ...More
WHY DO YOUR EARS POP?
- If you are flying in an aircraft and it changes height quickly, you may go a bit deaf, because the air inside and outside the eardrum are at different pressures. Your ears "pop" when the pressures become equal again. ...More
WHAT IS EARWAX?
- This yellow-brown wax is made by glands in the skin lining the ear canal. Wax traps dirt and germs and is slowly pushed out of the ear. ...More
HOW LOUD IS A WHISPER?
- A whisper is between 10 and 20 decibels. Some animals can detect much quieter sounds than we can. ...More
WHAT IS SOUND?
- Sound is waves of energy that are carried as vibrations through air, liquid and solid objects. ...More
WHY DO YOU LIKE SOME TASTES BETTER THAN OTHERS?
- Most people prefer things that taste sweet or slightly salty, but your sense of taste can easily become used to too much sugar and salt. How you like food to taste is very much decided by your eating habits. ...More
HOW DO YOU DETECT TASTE?
- The surface of the tongue has about 10,000 microscopic taste buds sunk in it. As you chew, tiny particles of food dissolve in saliva and trickle down to the taste buds. The taste receptors react and send messages about the taste to the brain.......More
DOES TASTE MATTER?
- Unpleasant tastes can warn you when food has gone bad or is poisonous. Your body needs healthy food, so enjoying the taste of it encourages you to eat. ...More
WHY DOES A BLOCKED NOSE STOP YOU TASTING?
- When you eat, you both taste and smell the food. If your nose is blocked with mucus from a cold, you can't smell properly and so food seems to have less taste too. ...More
WHY DO SOME ANIMALS HAVE KEENER SMELL?
- So they can find food and detect the presence of attackers. The inside of their nose is lined with many smell receptors, which are situated close to their nostrils. ...More
HOW DO YOU SMELL?
- A smell is made by tiny particles in the air. When you breathe in, they reach the smell receptors in your nose, which react to chemicals dissolved in the mucus inside your nose and send a message to the brain. ...More
WHY DO SOME THINGS SMELL MORE THAN OTHERS?
- Things that smell strongly, such as perfume or food cooking, give off more smell particles that float through the air. ...More
WHICH PARTS OF THE BODY ARE MOST SENSITIVE TO HEAT?
- Your elbows and feet are more sensitive to heat than many other parts of the body. You may have noticed that bath water feels much hotter to your feet than it does to your hand. Your lips and mouth are very sensitive to heat too. ...More
HOW DOES TOUCH WORK?
- There are many different kinds of sense receptor in the skin, which between them react to touch, heat, cold and pain. Some touch receptors react to the slightest thing, while others need a lot of pressure to make them respond. The brain puts......More
WHY DOES SNIFFING HELP YOU DETECT SMELLS BETTER?
- The smell receptors are at the top of your nose, so when you sniff you bring more smell particles up to them, which helps you detect the smell better. ...More
WHICH PARTS OF THE BODY ARE MOST AND LEAST SENSITIVE TO TOUCH?
- Any part of the body that has lots of touch receptors is particularly sensitive to touch. These parts include the lips, tongue, fingertips and soles of the feet. The back is one of the least sensitive areas of the body. ...More
CAN BLIND PEOPLE USE TOUCH TO SEE?
- Yes. Outside, they may use a long cane to feel the way in front of them. They may also read by touch, running their fingertips over Braille - patterns of raised dots that represent different letters. ...More
WHERE DOES FOOD GO AFTER IT IS SWALLOWED?
- When you swallow, the mushy ball of food goes down the gullet or oesophagus into the stomach. Here it churns around for up to four hours, while it is broken down into chyme, a soupy liquid. It is then gradually squeezed out of the stomach and......More
HOW BIG IS YOUR STOMACH?
- An adult stomach holds about 1 litre of food, and a child a bit less. Your stomach gets bigger the more you eat. A large adult can eat and drink up to 4 litres of food and liquid at one meal. ...More
WHAT IS THE APPENDIX?
- The appendix is a spare part of the large intestine that plays no part in digestion. Sometimes the appendix becomes infected and has to be removed. ...More
WHAT IS THE EPIGLOTTIS?
- The epiglottis is a kind of trap door that closes off your windpipe when you swallow. It stops food going down into the lungs. ...More
HOW LONG ARE THE INTESTINES?
- The small intestine is more than three times as long as the whole body! In an adult this is about 6 m. The large intestine is a further 1.5 m and the whole tube from mouth to anus measures about 9 m. ...More
WHY DO FAECES SMELL?
- Bacteria in the large intestine help to break down waste material, but they also make it smell. ...More
HOW MANY TEETH DO YOU HAVE?
- Each person has two sets of natural teeth during their life. The first set of 20 are called milk teeth and start to appear at about the age of six months. From about the age of six years, the milk teeth are gradually replaced by 32 adult......More
WHAT ARE TEETH MADE OF?
- The outside of a tooth is made of enamel and is the hardest substance in the body. Underneath is dentine, which is as hard as bone, and in the centre of each tooth is a tender pulpy mass of blood and nerves. ...More
WHY ARE TEETH DIFFERENT SHAPES?
- Different teeth do different jobs to help you chew up food. The broad, flat teeth at the front slice through food when you take a bite. They are called incisors. The pointed canine teeth are like fangs, and grip and tear chewy food such as meat.......More
WHY DOES VOMIT TASTE SOUR?
- When you vomit you bring back partly digested food into your mouth. It tastes sour because it is mixed with acid made by the lining of the stomach. The acid kills germs and helps to break the food down into smaller pieces. ...More
WHICH FOODS GIVE YOU ENERGY?
- Bread, rice, potatoes and pasta contain a lot of carbohydrates. Carbohydrates give you energy to move, work and grow. Fats and sugars also give you energy. ...More
WHICH FOODS MAKE YOU GROW?
- Milk, cheese, fish, meat and beans contain a lot of protein, a substance that the body needs to make new cells. A varied and balanced diet provides what that the body needs to grow. ...More
HOW DO YOU BREATHE IN AND OUT?
- The lungs do not have their own muscles to make you breathe in and out. The muscles between your ribs and the diaphragm - a sheet of muscle under the lungs - do the job instead. As your ribs move up and out, the diaphragm contracts and moves......More
WHAT HAPPENS WHEN YOU SNEEZE?
- When you sneeze, air rushes down your nose like a mini hurricane at 160 km/h - up to 20 times faster than normal. Sneezing blasts away whatever dust or pollen is irritating your nose. ...More
WHY DOES RUNNING MAKE YOU PUFF?
- Muscles use up oxygen as they work. When you run, your muscles are working hard and need extra oxygen. Puffing makes you breathe in up to 20 times more air, to supply your muscles with the oxygen they need. ...More
WHY DO YOU COUGH?
- You cough when extra mucus, dust or other particles clog the air passages between your nose and lungs. The sudden blast of air helps to clear the tubes. ...More
WHAT HAPPENS WHEN YOU HICCUP?
- Sometimes the diaphragm begins to contract in short, sharp spasms. These sudden movements make you "hic" as the gulps of air pass over the vocal cords. ...More
WHY DO YOU NEED TO BREATHE IN AIR?
- The air contains oxygen, which the body needs to stay alive. When you breathe in, you pull air through your mouth or nose into the windpipe and through narrower and narrower tubes in the lungs. At the end of each tiny tube, or bronchiole, are......More
HOW DO YOU TALK?
- When you breathe out, the air passes over the vocal cords in the voice box or larynx in the neck. When the cords vibrate they make a sound. Changing the shape of your lips and tongue makes different sounds, which can be put together into......More
WHY CAN BREATH LOOK MISTY?
- The air you breathe out contains water vapour. On a cold day this condenses into a mist of tiny water droplets. ...More
HOW MUCH AIR DO YOUR LUNGS HOLD?
- An adult lungs can hold up to 6 litres of air, while a child lungs hold less. ...More
WHY DO THE LUNGS HAVE SO MANY ALVEOLI?
- In order to provide a huge surface across which oxygen and carbon dioxide can move in and out of the blood. In fact the lungs have over 700 million alveoli. The area of the alveolar surface in the adult human is about 100 square metres. ...More
HOW LONG CAN YOU HOLD YOUR BREATH?
- You can probably hold your breath for about a minute. The longer you hold your breath the higher the carbon dioxide level in your blood rises, and the more you feel the need to breathe out. ...More
WHAT JOB DOES YOUR HEART DO?
- The heart job is to pump blood to the lungs and then all around the body. The right side of the heart takes in blood from the body and pumps it to the lungs. The left side of the heart takes blood filled with oxygen from the lungs and pumps it to......More
WHAT IS PLASMA?
- Just over half the blood is a yellowish liquid called plasma. It is mainly water with molecules of digested food and essential salts dissolved in it. ...More
WHAT IS A BLOOD TRANSFUSION?
- If a person loses a lot of blood, perhaps due to an accident or operation, the lost blood can be replaced with blood given by someone else. The new blood is dripped straight into a vein. ...More
HOW MUCH BLOOD DO YOU HAVE?
- An average man has 5 to 6 litres of blood; an average woman has between 4 and 5 litres. Children have less depending on how tall and heavy they are. ...More
WHAT ARE BLOOD GROUPS?
- There are four main groups of blood: A, B, AB and O. Only some groups can be mixed with others, so doctors find out which blood group a patient belongs to before giving a blood transfusion. ...More
WHY IS BLOOD RED?
- Each tiny drop of blood contains up to 5 million red blood cells that give blood its colour. Red blood cells contain a substance called haemoglobin, which takes in oxygen in the lungs. Blood that is rich in oxygen is bright red. As this bright......More
HOW OFTEN DOES THE HEART BEAT?
- A child heart usually beats about 80 times a minute, a bit faster than an adult (70 times a minute). When you run or do something strenuous, your heart beats faster to send more blood to the muscles. ...More
WHAT IS A CAPILLARY?
- Blood travels around the body through tubes called arteries and veins. These branch off into smaller and smaller tubes that reach every cell of the body. Capillaries are the tiniest blood vessels of all. Most capillaries are thinner than a single......More
HOW OFTEN DOES BLOOD GO AROUND THE BODY?
- It goes around about once a minute or 1,500 times a day. ...More
WHAT DO WHITE BLOOD CELLS DO?
- They surround and destroy germs and other intruders that get into the blood. ...More
HOW BIG IS THE HEART?
- The heart is about the size of a clenched fist. It lies nearly in the middle of your chest and the lower end tilts towards the left side of the body. ...More
WHAT IS THE HEART MADE OF?
- A special kind of muscle, called cardiac (heart) muscle, which never gets tired. ...More
WHAT DO THE KIDNEYS DO?
- Kidneys filter the blood to remove wastes and extra water and salts. Each kidney has about a million tiny filters, which between them clean about a quarter of your blood every minute. The kidneys work by forcing many substances out of the blood......More
WHY DO YOU SWEAT WHEN YOU ARE HOT?
- Sweating helps to cool you down. When the body becomes hot, sweat glands pump lots of salty water on to the skin. As the sweat evaporates (changes into water vapour), it takes extra heat from the body. Cleansed blood leaves the kidneys and......More
WHAT DOES THE LIVER DO?
- The liver is a chemical factory that does more than 500 different jobs. Some of its most important functions concern the processing of digested food and the removal of waste and poisons from the blood. Digested food is taken straight from the......More
WHAT IS BILE?
- Bile is a yellow-green liquid made by the liver and stored in the gall bladder. From there it passes into the small intestine, where it helps to break up fatty food. ...More
HOW MUCH URINE DOES THE BLADDER HOLD?
- An adult bladder can hold up to about 600 ml of urine (a child holds less). But you usually need to go to the bathroom as soon as your bladder is about a quarter full. ...More
WHY DO YOU GO RED WHEN YOU ARE HOT?
- As different parts of the body burn up energy they make heat. Blood carries the heat around the body. If the body becomes too hot, the tiny blood vessels near the surface of the skin expand to help the blood cool. Blood flowing near to the skin......More
HOW MUCH LIQUID DO YOU NEED TO DRINK?
- You need to drink about 1.2 to 1.5 litres of watery drinks every day. The amount of water you take in balances the amount you lose. Most water is lost in urine and faeces. But sweat and the air you breathe out also contain water. ...More
WHY IS URINE YELLOW?
- Urine contains traces of waste bile and this makes it yellowish. If you drink a lot of water, your urine will be diluted and less yellow, but the first urine of the morning is usually stronger and darker. Some foods affect the colour of urine.......More
WHY DO YOU NEED TO DRINK MORE IN HOT WEATHER?
- When it is hot, you sweat more and so lose more water, which you then replace by drinking more. ...More
WHAT MAKES YOU URINATE?
- The bladder stretches as it fills. When it has about 150 ml in it, nerves in the walls of the bladder send signals to the brain and you feel the need to urinate....More
HOW LONG CAN YOU LIVE WITHOUT WATER?
- Although some people have lived for several weeks without food, you can survive only a few days without drinking water. ...More
WHY DO CHILDREN LOOK LIKE THEIR PARENTS?
- You inherit a mixture of genes from your parents, so in some ways you will look similar to your mother and in others to your father. ...More
HOW DOES A NEW BABY BEGIN?
- A new baby begins when a sperm from a man joins with an egg from a woman. This is called fertilization, and it happens after the man ejaculates sperm into the woman vagina during sex. The cells of the fertilized egg begin to multiply into a......More
WHAT IS A FOETUS?
- A foetus is an unborn baby from eight weeks after conception until birth. In the first seven weeks after conception it is called an embryo. By 14 weeks the foetus is fully formed, but it is too small and frail to survive outside the womb. Babies......More
WHAT IS LABOUR?
- Labour is the process of giving birth. The neck of the womb stretches and opens, and then the womb, which is made of strong muscle, contracts to push the baby out. Labour can take several hours. ...More
HOW FAST DOES AN UNBORN BABY GROW?
- You grow faster before you are born than at any other time in your life. Three weeks after the egg is fertilized, the embryo is no bigger than a grain of rice. Five weeks later, almost every part of the new baby has formed - the head, brain,......More
WHAT DO BABIES DO IN THE WOMB?
- As the unborn baby gets bigger, it exercises its muscles by kicking, moving and punching. It also sucks its thumb sometimes, opens and shuts its eyes, and goes to sleep. ...More
WHERE DOES A MAN SPERM COME FROM?
- Sperm are made in the testicles, two sacs that hang to either side of the penis. After puberty the testicles make millions of sperm every day. Any sperm that are not ejaculated are absorbed back into the blood. ...More
WHAT ARE GENES?
- Genes are a combination of chemicals contained in each cell. They come from your mother and father and determine everything about you, including the colour of your hair, how tall you will be, and even what diseases you might get in later......More
WHERE DOES THE EGG COME FROM?
- When a girl is born she already has thousands of eggs stored in her two ovaries. After puberty, one of these eggs is released every month and travels down the Fallopian tube to the womb. ...More
HOW DOES AN UNBORN BABY FEED?
- Most of the cluster of cells that embeds itself in the womb grows into an organ called the placenta. Food and oxygen from the mother blood pass through the placenta into the blood of the growing baby. ...More
WHAT IS A PERIOD?
- If the egg is not fertilized by a sperm, it passes out of the woman body through the vagina. At the same time, the lining of the womb and some blood also pass out of the body. This slow flow of blood lasts about five days every month and is......More
WHAT IS PUBERTY?
- Puberty is the time in which you grow from a child into an adult. You grow taller and your body changes shape. A girl develops breasts and her hips become broader. Her waist looks thinner. A boy chest becomes broader and his voice grows deeper.......More
WHAT HAPPENS WHEN A BOY VOICE BREAKS?
- A boy may be growing so fast during puberty that the muscles that control his vocal cords cannot keep up. His voice may suddenly change from high to low before finding the right pitch. The vocal cords also become thicker, making his voice......More
WHEN ARE YOU FULLY GROWN?
- Boys and girls grow quickly during puberty, and then they grow more slowly until they reach their full height sometime around age 20 years. ...More
ARE NEWBORN BABIES COMPLETELY HELPLESS?
- Not completely - a baby can breathe, suck and swallow from the moment it is born. ...More
WHY CAN NOT YOUNG BABIES SIT UP?
- Young babies cannot sit up until their back muscles have grown strong enough to support them. This happens around 6 months. ...More
WHEN DO BABIES LEARN TO WALK AND TALK?
- By its first birthday, a baby is usually already pulling itself up on to its feet and is nearly ready to walk. It may also be beginning to say a few words, though talking develops slowly over the next few years. ...More
WHAT ARE HORMONES?
- Hormones are chemicals released into the blood from various glands. Some glands make sex hormones that control the menstrual cycle. ...More
WHY DO PEOPLE AGE?
- The cells of the body are constantly being renewed, except for brain cells and other nerve cells. As people get older, the new cells do not perform as well as the cells of younger people. ...More
WHAT DO ALL NEW BABIES NEED?
- All newborn babies need food, warmth, love and protection. At first a baby can only drink liquids, so it sucks milk from its mother breasts or from a bottle. Milk contains everything the new baby needs to grow and stay healthy. A baby also needs......More
WHAT MAKES YOU GROW?
- A growth hormone tells your body to grow. This is produced in the pituitary gland in the brain and taken all round the body in the blood. Exactly how tall you grow is determined by genes inherited from your parents. ...More
WHAT IS THE MENOPAUSE?
- The menopause is when a woman body changes so that she is no longer able to have children. As sex hormone levels drop, her ovaries stop producing eggs. The woman may experience uncomfortable hot flushes and unpredictable mood swings. ...More
WHO HAD THE MOST CHILDREN?
- It is believed that a Russian woman who lived in the 1700s holds this record. She was called Madame Vassilyev and she gave birth to no fewer than 69 children. ...More
WHY DO YOU HAVE TO SUPPORT A YOUNG BABY HEAD?
- When a baby is born the muscles in its back and neck are very weak - too weak to hold up its own head. A baby head is much bigger for the size of its body than a child or an adult. Very old people may become quite frail. ...More
WHY DO BABIES CRY?
- A baby cries when it needs something - when it is hungry or lonely. It also cries when it has a stomach ache or other pain....More