Gravitation is a very important force in the universe. Every object has a gravitational pull, which is like magnetism. But, unlike magnetism, gravitation is not found only in iron and steel. Sir Isaac Newton, the great scientist of the seventeenth century, first studied gravitation. When he was a boy, he often saw apples falling to the ground. He wondered why they fell towards the earth, and why they did not fly up in to the sky. According to the law he later produced, everything in the universe attracts everything else toward itself. The sun attracts the earth and the earth attracts the sun. The earth attracts the moon and the moon attracts the earth. Although the bigger object has the stronger attraction, all objects, in fact, have some; but we do not notice the gravitational pull of a book because the pull of the earth is very much greater. Why does the earth always move round the sun, and not fly off in to cold space? The sun's gravitation gives the answer. The earth is always trying to move away in a straight line, but the sun is always pulling it back. So it continues on its journey round and round the sun. The sun is one of the stars in the galaxy, in which there are about 100,000 million stars. It is not in the meddle of the galaxy, but rather near one edge. There stars from a group, the shape of which is rather like the shape of a watch. There are millions of galaxies in the universe, and so there are thousands of millions of millions suns. Many astronomers believe that some of these suns have planets as our sun does. Gravitation is the force which holds all the atoms of the earth together. It holds us on the earth; if there were no gravitation, we and everything else would fly off the earth in to space. Einstein produced a new law of gravitation. Its main results are the same as the results of Newton's law; but in every small and find matters; Einstein's law gives different results. One of these is that gravitation bends light a little; but according to Newton's law gravitation has very little effect on light. Einstein showed this fact by means of mathematics, and not by experiment. This result of his law tested during an eclipse of the sun, usually, when the light of a star passes the sun, we cannot see it; the sun is too bright. But during an eclipse, the sun's light is shut out by the moon; then we can see the light of the star. The astronomers who watched noticed that the star appeared to change its position a little. The cause of this was that the star's light was turning from the straight line as it passed the sun. The sun's gravitation was bending the beam of light. This showed that Einstein was right.
Gravitation: the force which causes objects to be attracted towards each other.
Universe: whole world
Steel: a strong metal made mainly from iron.
Fly off: deviate
Fly up: go up in the air
Galaxy: similar group of stars
Watch: a small clock
To be shut out: to be covered
Beam: shaft of light
good luck,everybody
محتوای مخفی: Main Lyrics