The Making of the Earth
You know that the earth goes round the sun and the moon goes round the earth. You know also perhaps that there are several other bodies which, like the earth, go round the sun. All these, including our earth, are called planets of the sun. The moon is called a satellite of the earth because it hangs on to it. The other planets have also got their satellites. The sun and the planets with their satellites form a happy family. This is called the solar system. Solar means belonging to the sun, and the sun being the father of all the planets the whole group is called the solar system.
At night, you see thousands of stars in the sky. Only a few of these are the planets and these are really not called stars at all. Can you distinguish between a planet and a star? The planets are really quite tiny, like our earth, compared to the stars but they look bigger in the sky because they are much nearer to us. Just as the moon, which is really quite a baby, looks so big because it is quite near to us. But the real way to distinguish the stars from the planets is to see if they twinkle or not. Stars twinkle, planets do not. That is because the planets only shine because they get the light of our sun. It is only the sunshine on the planets or the moon that we see. The real stars are like our sun. They shine of themselves because they are very hot and burning. In reality, our sun itself is a star, only it looks bigger as it is nearer and we see it as a great ball of fire.
So then our earth belongs to the family of the sun–the solar system. We think the earth is very big, and it is big compared to our tiny selves. It takes weeks and months to go from one part of it to another even in a fast train or steamer. But although it seems so big to us it is just like a speck of dust hanging in the air. The sun is millions of miles away and the other stars are even further away.
Astronomers, those people who study the stars, tell us that long, long ago the earth and all the planets were part of the sun. The sun was then, as it is now, a mass of flaming matter, terribly hot. Somehow little bits of the sun got loose and they shot out into the air. But they could not wholly get rid of their father, the sun. It was as if a rope was tied to them and they kept whirling round the sun. This strange force, which I have compared to a rope, is something which attracts little things to great. It is the force which makes things fall by their weight. The earth being the biggest thing near us attracts everything we have.
In this way our earth also shot out from the sun. It must have been very hot, with terribly hot gases and air all round it, but as it was very much smaller than the sun it started to cool. The sun also is getting less hot but it will take millions of years to cool down. The earth took much less time to cool. When it was hot, of course, nothing could live on it – no man or animal or plant or tree. Everything would have been burnt up then.
Just as a bit of the sun shot out and became the earth, so also a bit of the earth shot out and became the moon. Many people think that the moon came out of the great hollow which is now the Pacific Ocean, between America and Japan. So the earth started to cool. It took a long time over it. Gradually, the surface of the earth became cooler although the interior remained very hot. Even now if you go down a coal mine, it becomes hotter and hotter as you go down. Probably if you could go down deep enough inside the earth you would find it red hot. The moon also started to cool, and because it was much smaller than even the earth it cooled more quickly than the earth. It looks delightfully cool, does it not? It is called the 'cold moon'. Perhaps it is full of glaciers and ice fields.
When the earth cooled, all the water vapour in the air condensed into water and probably came down as rain. It must have rained a tremendous lot then. All this water filled the great hollows in the earth, and so the great oceans and seas were formed.
As the earth became cooler and the oceans also became cooler, it became possible for living things to exist on the earth's surface or in the sea. We shall discuss the early beginnings of life in the next letter.
Comments
Post a Comment