My Science School

          The Moon is the biggest and brightest object that one can spot on the night sky. It appears quite large because it is the closest celestial body to Earth.

          The equatorial radius of the Moon is around 1737 kilometres and the equatorial diameter is about 3472 kilometres. It is almost one-fourth the size of Earth. You can roughly fit in four moons inside the Earth. The Moon’s surface is as big as North and South America put together. According to NASA, “if Earth was the size of a nickel, the Moon would be about as big as a coffee bean.”

          The Moon is not a perfect sphere, just like the Earth. It is slightly flattened towards the poles. The diameter of the Moon from pole to pole is lesser than its equatorial diameter.

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          Poets often describe the silvery moon. But, the Moon doesn’t always appear silvery; it is sometimes white, sometimes yellow, grey or even red at times.

          When the Moon is low in the sky, it is closer to the horizon. The light that travels through the air scatters near the horizon as it passes through a thick layer of atmosphere. As a result, the Moon looks yellowish or orange at times. When the Moon is high in the sky, the scattering effect is much lesser and it appears whitish. During a total lunar eclipse, the Moon appears to be red; this too is caused by the scattering of light. The colours of the Moon give us clues about the minerals present on its surface.

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          Even if there are a thousand stars in the sky, it will look a bit dull if we can’t spot the Moon. It is the brightest object in the night sky. But, the Moon does not have a light of its own. How ironic!

          Moonlight is produced when sunlight is reflected by the white dust on the Moon’s surface. The Moon will reflect only 3-12 per cent of the sunlight that hits its surface.

          The other factors that influence the brightness of the Moon include the movement of the Moon around the Earth and the simultaneous movement of the Earth around the Sun.

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          Some of you might have dressed up as astronauts for your school fancy dress competition. Was it easy for you to walk around in the costume? Surely not.

          An astronaut has to carry equipment with necessary supplies like oxygen. Their space suits are usually very heavy, weighing more than 90 kilograms. But, they walk around quite easily. This is because of the Moon’s lower gravitational pull.

          The Moon’s mass is 81 times smaller than the mass of the Earth. As a result, the force of gravity on the Moon is six times weaker than that on the surface of the Earth. A bag that would weigh six kilograms on Earth would weigh just one kilogram on the Moon. Astronauts feel lighter because of this reason and walk easily on the surface of the Moon.

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          Neil Armstrong set foot on the Moon in 1969. If one were to visit the Moon now, one could still find the footprints that he left behind in 1969.

          If you leave a footprint on sand or mud on Earth, either wind or rain would wash it away and it would soon disappear. On the other hand, the footprints left on the Moon last almost forever. Wonder why? Unlike on Earth, there is no wind or water on the Moon to wash it off.

          Therefore, the footprints won’t be eroded and will last for a really long time. So don’t expect to do something mischievous on the Moon and get away with it as your footprints will give you away!

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          We know that meteors fall like missiles on the surface of the Moon as there is no atmosphere to protect it. Instead of water, comets and chunks of asteroids rain on the surface of the Moon and their impact creates craters. These are known as impact craters.

          Craters are formed due to powerful volcanic explosions as well. When the Moon’s surface is pushed upwards by melted rock, hot lava and gases gush out of it, giving rise to craters. Some craters are more than two billion years old. Generally, the age of a large crater is determined by counting the number of smaller craters it contains.

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          The Moon’s surface is covered with flat, circular sunken areas known as craters. Some craters like Clavius are so big that they can be seen even without the help of a telescope. Clavius is 235 kilometres wide and is surrounded by huge mountains. Some craters however, are very small in diameter.

          The arrangement of mountains around a large crater is peculiar; they form a circular wall. These mountains slope down gently towards the outer surface while they form a steep slope inside. When Galileo first observed craters, they looked like cups. He named craters so from the Latin word for cup.

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          We know that the Moon does not have a protective layer of atmosphere around it. Likewise, there is no wind, rain or clouds on the Moon. There is only vacuum, and sound cannot travel through vacuum. Therefore, unaided communication is not possible on the Moon. This problem can be solved with the help of a radio.

          The helmets that astronauts wear are equipped with a device that would convert the sound waves to radio waves. Radio waves are electromagnetic in nature and can travel through vacuum. These radio waves are in turn transmitted to the ground or to their fellow astronauts.

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          You might have observed the sudden flash of a bright moving object in the night sky. These bright trails are left by pieces of rocks in outer space, known as meteors. Millions of meteors speed towards our Earth every day, but they burn up due to the friction caused by Earth’s atmosphere.

          The Moon does not have an atmosphere to blanket itself. Therefore, there is no friction that would burn the pieces of rock approaching the Moon at great speeds. As a result, they crash on the surface of the Moon, forming lunar soil.

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          The Moon’s surface not only has mountains, it also has rocks. Scientists found out that these moon rocks are similar to the igneous rocks on the Earth. They too are formed when molten lava solidifies after cooling down. But, their chemical make-up is different from that of the rocks found on Earth.

          Moon rocks do not contain any traces of water. Much of the Moon’s surface is covered by tiny pieces of rocks, and dust. This is known as lunar soil.

          It takes billions of years to form lunar soil. It is formed when large and small pieces of rocks rain on the surface of the Moon. Unlike the Earth, there is less iron on lunar soil.

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          When seen with the naked eye from the Earth, the Moon looks like a smooth sphere, just like the globe, with dark and light patches here and there.

          A telescopic view of the Moon suggests otherwise. It would not be wrong if someone says that the Moon looks like cheese! Its surface has lots of holes and sometimes, it appears yellowish as well.

          The dark patches on the surface of the Moon are lowlands of rock. These areas were once thought to be water bodies by Galileo. It’s covered by a thin layer of rocky soil. On the other hand, the lighter areas are known as highlands. The highlands are mountainous and rough.

          Huge craters are found in the mountainous areas. Craters are found in the lowlands as well, but in much fewer numbers. The surface is barren and the sky always appears dark.

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          Since a lot many people wondered about the Moon, we have several theories about its formation. Though we still don’t know exactly how the Moon came into existence, these theories are based on scientific explanations.

          The Capture Theory suggests that the Moon was a planet that once moved in its orbit around the Sun. The Earth, with its greater gravitational force pulled the Moon towards our planet. The Co-formation Theory suggests that the Earth and Moon were formed at the same time from a cloud of dust and gas.

          It was George Howard Darwin, Charles Darwin’s son who proposed the Fission Theory. According to G H Darwin, the Earth spun so fast in the early years that a bulge formed on one of its sides. After a while, the Sun’s gravitational pull tore off this bulge. It fell off in space and later formed the Moon.

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          There are many theories that try to explain how the Moon was formed. ‘The Impact Theory’ is a popular one among them. This theory suggests that the Moon is younger than the Earth though it is billions of years old.

          The Impact Theory talks about something that happened about 4.5 billion years ago. Back then, the Earth did not have any satellites. A huge body about the size of Mars hit our planet. This shook off the Earth from its orbit as a result of which, portions of the Earth broke.

          Gradually, these broken pieces came together along with gas and dust, and solidified to form the Moon. This unification had other effects however; molten lava oozed out from the interior of the Moon for the next two billion years.

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          Ever since Man started looking at the Moon with his naked eyes, he was curious to learn about this brightly shining heavenly body. It was an Italian scientist who closely observed the Moon for the first time. His name was Galileo Galilei.

          It happened in 1609. Galileo built an equipment called telescope that made objects in space look larger and closer.

          For centuries, scientists had believed that the Moon had a smooth surface. Galileo shattered this belief; he observed that the Moon’s surface was not so smooth; instead it had mountains, pits, valleys, shadows and other features, just like the surface of the Earth. He thought the vast dark shadowy areas to be seas of water and called them ‘maria’, the Latin word for sea. Galileo’s work laid the foundation for modern studies in astronomy.

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          Tracing the origins of the Moon’s name is a bit difficult as the Moon existed from the prehistoric times.

          The Moon has been known by different names since times immemorial. For instance, the Greeks call it Selene, while Moon is known as Luna in Latin. However, the English ‘Moon’ comes from ‘mona’, an Old English word. This word is derived from a Latin word ‘mensis’ meaning month.

          In the olden days, people used the Moon to measure time. The satellites of other planets like Jupiter and Saturn are also commonly known as moons.

          You might have also heard words like lunar orbit and lunar rover. Anything related to the Moon is usually known as lunar.