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Universe

Life

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LIFE

 

LIFE

 

 

 

1. HOW DID LIFE BEGIN?

Ans: Scientific experiments in the 1950 s 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 “self replicating -that is, able to make copies of themselves. This is the key to life, which remains a mystery. However, the first life forms were probably tiny bacteria called Archebacteria, which thrive in very hot, chemically rich places.

 

 

2. WHAT IS LIFE MADE OF?

Ans: 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.

 

 

3. WHERE DID THE MATERIALS OF LIFE COME FROM?

Ans: It used to be thought that organic chemicals all originated on Earth, but traces of all kinds of organic chemicals
have be on detected in giant molecular clouds, including formaldehyde, alcohol, and also acetaldehyde, one of the
components of amino acids.

 

 

4. WHERE DID LIFE COME FROM?

Ans: 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.

 

 

5. ARE THERE ANY OTHER PLANETS LIKE EARTH?

Ans: 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.

 

 

6. WHAT DOES AN ALIEN LOOK LIKE?

Ans: At the moment, the only aliens we are likely to encounter are very, very small and look like viruses.

 

 

7. HOW ARE WE LOOKING FOR EXTRA-TERRESTRIAL LIFE?

Ans: 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.

 

 

8. IS THERE LIFE ON OTHER PLANETS?

Ans: 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 whether it is fairly likely to happen given the right conditions.

 

 

9. WHY IS THE UNIVERSE LIKE IT IS?

Ans: 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 such a way that intelligent life must develop at some stage. This is called the strong anthropic principle.

 

 

10. WHAT IS DNA?

Ans: 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, inked by “rungs” of four different chemical bases. The order of these bases is a chemical code that provides all the instructions needed for life.

 

 

11. WHAT IS SETI ?

Ans:  SETI  is the Search for Extra-Terrestrial Intelligence project, designed to continually scan radio signals from space and pick up any signs of intelligence. lt looks for signals that have a pattern, but are not completely regular, like those from pulsating stars.

 

 

 

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History Of The Universe

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HISTORY OF THE UNIVERSE

 

 

 

 

 

 

 

1. WHAT WAS THE UNIVERSE LIKE AT THE BEGINNING?

Ans: 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 force. But this original universe lasted only a split second. After just three trillion of a trillionth of a trillionth of a second, the super force split up into separate forces.

 

 

2. WHAT WAS THERE BEFORE THE UNIVERSE?

Ans: No one knows. Some people think there was an unimaginable ocean beyond space and time of potential universes continually bursting into life, or failing Ours succeeded.

 

 

3. WHAT WAS THE BIG BANG?

Ans: 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 universe has been swelling ever since.

 

 

4. CAN WE SEE THE BIG BANG?

Ans: 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.

 

 

5. HOW DO WE KNOW WHAT IT WAS LIKE?

Ans: 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 a tunnel, and then crash them together.

 

 

6. WHAT IS INFLATION?

Ans: Inflation was when dramatic expansion and cooling took place after the first second or so in the life of the universe, when spaces welled up and cooled enormously.

 

 

7. HOW DO WE KNOW THE UNIVERSE IS GETTING BIGGER?

Ans: 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.

 

 

8. HOW DID THE FIRST GALAXIES AND STARS FORM?

Ans: 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.

 

 

9. HOW OLD IS THE UNIVERSE?

Ans: 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 very, very small indeed. This suggests that the universe is between 10 and 20 billion years old. However, studies of globular clusters suggest some stars in our galaxy may be older than this.

 

 

 

History of the Universe

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Galaxy

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GALAXIES

galaxy

 

 

 

 

1. WHAT IS A GALAXY?

Ans: 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 Way. (Galaxy comes from the Greek for milky.) But earlier this century it was realized that the Galaxy is just one of billions of similar giant star groups scattered throughout space, which we also call galaxies. The nearest is the Andromeda galaxy.

 

 

2. WHAT ARE STAR CLUSTERS?

Ans: 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.

 

 

3. HOW MANY GALAXIES ARE THERE?

Ans: There are currently estimated to be about 125 billion galaxies in the universe – there may be many, many more than this.

 

 

4. WHAT IS THE MILKY WAY?

Ans: 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.

 

 

5. WHAT ARE DOUBLE STARS?

Ans: Our Sun is alone in space, but many stars have one or more nearby companions. Double stars are called binaries.

 

 

7. WHAT IS A SPIRAL GALAXIES?

Ans: A spiral galaxies are  galaxies that has spiralling arms of stars like a gigantic Catherine wheel. They trail because the galaxy is rotating Our Galaxy is a spiral galaxy.

 

 

8. WHAT IS THE BIGGEST THING IN THE UNIVERSE?

Ans: 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.

 

 

9. WHERE IS THE EARTH?

Ans: The Earth is just over half way out along one of the spiral arms of the Galaxy, about 30,000 light-years from the center.

 

 

10. WHAT EXACTLY ARE NEBULAE?

Ans: 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 star With others, called dark nebulae, we see only inky black patches hiding the stars behind. This is where stars are born . A few, called glowing nebulae, glow faintly of their own a as the gas within them is heated by nearby stars.

 

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Matter

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MATTER

 

1. WHAT IS THE UNIVERSE MADE OF?

Ans: 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 concentrations. This happens in the few rocky planets like Earth, where iron, oxygen and magnesium are the most common elements. Carbon, a scarcer element, is the one on which all
life forms are based.

 

 

2. WHAT WAS THE FIRST ELEMENT?

Ans: The first element to form was deuterium – a heavy form of hydrogen. It formed within I.5 minutes of the dawn of the universe.

 

 

3. HOW WAS IRON MADE?

Ans: Iron was forged in the heart of super giant stars near the end of their lives, when the immense pressures there forced carbon atoms together.

 

 

4. WHAT IS ANTI-MATTER?

Ans: 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.

 

 

5. WHAT HOLDS EVERYTHING TOGETHER?

Ans: 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 the invisibly small nucleus of the atom, holding it all together.

 

 

6. HOW WERE ATOMS MADE?

Ans: 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.

 

 

7. WHAT ARE PARTICLES?

Ans: 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.

 

 

8. WHAT IS THE SMALLEST KNOWN PARTICLE?

Ans: The smallest particle inside the nucleus is the quark. It is less than 1020 m across, which means a line of ten billion billion of them would be less than a metre long.

 

 

 

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Gravity and Black Hole

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GRAVITY AND BLACK HOLE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

1. WHAT IS A BLACK HOLE?

Ans: If a small star 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 singularity. The gravitational pull of a Singularity is so immense that it pulls space into a  “hole” like a funnel. This is the black hole, which sucks in everything that comes near it with its huge gravitational force- including light, which is
why it is a “black” hole.

 

 

2. WHAT IS GRAVITY?

Ans: 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 Sun is so big, it makes its pull felt over millions of kilometres of space. The Earth is smaller, but big enough to keep the Moon circling around it. The weight of an object is simply how hard gravity is pulling on it.

 

 

3. HOW STRONG IS A PLANET’S GRAVITY?

Ans: 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.

 

 

4. HOW BIG IS A BLACK HOLE?

Ans: 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 maybe about the size of the solar system.

 

 

5. WHAT ARE ORBITS?

Ans: 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.

 

 

6. WHAT HAPPENS INSIDE A BLACK HOLE?

Ans: 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 gravity.

 

 

7. HOW MANY BLACK HOLES ARE THERE?

Ans: No one really knows. Because they trap light, they are hard to see. But there may be as many as 100 million black holes in the Milky Way.

 

 

8. WHAT DID NEWTON DISCOVER?

Ans: The discoveries of Sir Isaac Newton (1642-1727) include the three fundamental laws of motion. He also discovered the force called gravity, which holds the Moon in orbit around the Earth, and the planets in orbit around the Sun.

 

 

 

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Birth of a Star

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BIRTH OF A STAR 

 

 

 

 

 

 

 

 

 

1. DESCRIBE THE BIRTH OF A STAR?

Ans: 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 million C, so a nuclear fusion reaction starts.

 

 

2. WHAT IS A STAR?

Ans: 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 also distant that we can see stars only as pinpoints of light in the night sky, even through the most powerful telescope. As far as we can see there are no other large objects in the universe.

 

 

3. HOW MANY STARS ARE THERE?

Ans: 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 billion.

 

 

4. WHAT IS THE BIGGEST STAR?

Ans: The biggest stars are the super giants. Antares is 700 times as big as he Sun. There may be a star in the Epsilon system in the constellation of Auriga that is ,860 million (3 miles billion km) across 4,000 times as big as the Sun!

 

 

5. WHY DO SOME STARS THROB?

Ans: 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.

 

 

6. WHAT ARE CONSTELLATIONS?

Ans: Constellations are small patterns of stars in the sky, each with its own name. They help astronomers locate things in the night sky.

 

 

7. HOW HOT IS A STAR?

Ans: The surface temperature of the coolest stars is below 3,500° C: that of the hottest, brightest stars is over 40,000°C.

 

 

8. WHERE ARE STARS BORN ?

Ans: 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 are called giant molecular clouds. Here temperatures plunge to -263 C, which is just 10° short of absolute zero. These nebulae are thin and cold, but contain all the materials needed to make a star.

 

 

9. WHAT MAKES STARS TWINKLE?

Ans: 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.

 

 

10. WHAT MAKES STARS GLOW?

Ans: Stars glow because the enormous pressure deep inside generates nuclear fusion reactions in which hydrogen atoms are fused  together, releasing huge quantities of energy.

 

 

11. WHAT COLOR ARE STARS?

Ans: It depends how hot they are. The color 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.

 

 

Distance

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DISTANCE 

 

 

 

 

1. WHAT IS THE DISTANCE OF THE SUN FROM THE EARTH?

Ans:  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.

 

 

2. WHAT IS RED SHIFT?

Ans: 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.

 

 

3. WHAT IS A LIGHT-YEAR?

Ans: 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.

 

 

4. HOW FAR IS IT TO THE NEAREST STAR?

Ans: The nearest star is Proxima Centauri, which is 43 light-years away, or 40 trillion km.

 

 

5. WHAT IS A PARSEC?

Ans: 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.

 

 

6. HOW DID ASTRONOMERS FIRST ESTIMATE THE SUN’S DISTANCE?

Ans: 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 work out by simple geometry the distance from Earth to the Sun, Cassini’s estimate was only a few percent out.

 

7. WHAT IS THE FURTHEST OBJECT WE CAN SEE?

Ans: The furthest objects we can see in space are quasars,which may be over 13 billion light-years away.

 

 

8. ARE THE STARS GETTING FURTHER AWAY?

Ans: 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.

 

 

 

9. HOW FAR AWAY IS THE MOON?

Ans: At its nearest, the Moon is 356.517 km away from Earth; at its furthest, it is 406,71| 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 distance is shown by how long it takes the beam to travel to the Moon and back.

 

 

The Outer Planets

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THE OUTER PLANETS 

 

 

 

 

 

 

 

 

 

 

1.WHAT ARE THE OUTER PLANETS?

Ans: 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, Neptune in 1846,Pluto in 1930 and Charon as recently as 1978. Uranus and Neptune are gas giants like Jupiter and Saturn.

 

 

2. WHAT’S STRANGE ABOUT URANUS?

Ans: 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.

 

 

3. WHAT’S AN ASTEROID?

Ans: 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 asteroid shave been identified so far.

 

 

4. WHAT IS A COMET?

Ans: Comets are really just dirty ice balls. 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 the solar wind. We may see this spectacular tail in the night sky shining in the sunlight for a few weeks until it swings round the Sun and out of sight. The Hale-Bopp comet gave a spectacular display in 1997.

 

 

5. WHO FOUND NEPTUNE?

Ans: Two mathematicians, John Couch Adams in England and Urbain le 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.

 

 

6. HOW LONG IS A YEAR ON NEPTUNE?

Ans: Neptune is so far from the Sun- over 4,500 million km that its orbit takes about 165 Earth years. So one year on
Neptune lasts 165 Earth years.

 

 

7. WHY IS NEPTUNE GREEN?

Ans: Neptune appears greeny-blue because of the methane gas (a component of natural gas) in its atmosphere.

 

 

8. HOW BIG IS PLUTO?

Ans: 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.

 

 

9. WHAT IS A METEORITE?

Ans: Meteorites are lumps of rock from space big enough to penetrate the Earth’s atmosphere and reach the ground without burning up.

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The Giant Planets

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THE GIANT PLANETS :

 

 

 

 

 


 

 

 

 

 

 

 

 

 

1. WHAT ARE SATURN’S RINGS?
Ans: Saturn’s rings are the planets shining halo, first seen by Galileo Galilei ( I564-1642), 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 refrigerator and most the size of ice cubes. The rings are incredibly thin no more than 50 m deep yet they stretch from 7,000 km to 74,000 km out into space. One of Saturn’s rings is as thin as a piece of tissue paper being stretched over a football pitch.

 


2. HOW WINDY IS SATURN?
Ans: Saturn’s winds are even faster th roar round up to I,800 km/h. But Neptune’s a even faster!Jupiter’s and the planet.

 


3. WHAT IS THE CASSINI DIVISION?

Ans: Saturn’s rings occur in broad bands referred to by the letters A to G. In 167 the astronomer Cassini spotted a dart gap between rings A and B. This is now called the Cassini division, after him.

 


4. HOW MANY MOONS HAS SATURN?

Ans: Saturn has at least 18 moons, including Lapetus, which is dark on one side and light on the other.

 


5. HOW BIG IS JUPITER?
Ans: Very big. Even though Jupiter is largely gas, it weighs 320 times as much as the Earth and is 142,984 km in diameter.

 


6. HOW LONG DOES IT TAKE JUPITER TO ORBIT THE SUN?
Ans: Jupiter takes 11 years and 314 days (by our Earth calendar) to complete its journey around the Sun.

 


7. WHAT ARE THE GIANT PLANETS?
Ans: 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, and only their very core is rocky. This does not mean they are vast cloud balls. The enormous pressure of gravity means the gas is squeezed until it becomes liquid, and even solid.

 


8. COULD YOU LAND ON JUPITER?
Ans: 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.

 


9. HOW FAST DOES JUPITER SPIN?
Ans: 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!

 

 

The Inner Planets

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THE INNER PLANETS :

 

 

 

 

 

 

 

 

 

1. WHAT ARE THE INNER PLANETS?
Ans: 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 made of rock, unlike the bigger planets further out, which are made mostly of gas. Because they are made of rock, they have a hard surface a spaceship could land on, which is why they are sometimes called terrestrial(earth) planets. They all have a thin atmosphere, but each is very different.

 

2. WHY IS MARS RED?
Ans: Mars is red because it is rusty.The surface contains a high proportion of iron dust, and this has been oxidized in the carbon dioxide atmosphere.

 

3. WHAT’S FRIGHTENING ABOUT MARS’S MOONS?
Ans: One night American astronomer Asaph Hall got fed up with studying Mars and decided to go to bed.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 Phobos (fear) and Deimos (panic), after the attendants of the Roman war god, Mars.

 

4. LIFE ON MARS?
Ans: The Viking landers of the 1970 s 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.

 

5. WHY IS VENUS CALLED THE EVENING STAR?
Ans: Venus reflects sunlight so well it shines like a star. But because it is quite close to the Sun, we can see it in the evening, just after the Sun sets.We can also see it just before sunrise.

 

6. WHAT ARE THE INNER PLANETS MADE OF?
Ans: Each of the inner planets is formed a little bit like an egg with a hard “shell” or crust of rock, a “white” or mantle of soft, semi-molten rock, and a”yolk” or core of hot, often molten, iron and nickel.

 

7. WHAT CANYON IS BIGGER THAN THE GRAND CANYON?
Ans: A canyon on Mars! The surface of Mars is more stable than Earth’s, and there is no rain or running water to wear down the landscape. It has a volcano called Olympus Mons which is 17 miles (27 km s)high three times higher than Mount Everest. It also has a great chasm, discovered by the Mariner 9 space probe and called the Valles Marineris. This is
over 4,000 km long and four times as deep as America’s Grand Canyon.

 

8. COULD YOU BREATHE ON MERCURY?
Ans: Not without your own oxygen supply. Mercury has almost no atmosphere-just a few wisps of sodium because gases are burned off by the nearby Sun.

 

9. WHAT IS THE AIR ON VENUS?
Ans: Venus’s atmosphere would be deadly for humans. It is very deep, so the pressure on the ground is huge. It is made mainly of poisonous carbon dioxide and is also filled with clouds of sulphuric acid.

 

10. HOW HOT IS MERCURY?
Ans: Temperatures on Mercury veer from one extreme to the other because it has too thin an atmosphere to insulate it. In the day, temperatures soar to 400° C; at night they plunge to -175°C.