CBSE Class 9 Answered

According to Newton's theory, the reason for the earth or any planet orbit the Sun is related to why objects fall to Earth

when we drop them. The Sun's gravity pulls on the planets, just as Earth's gravity pulls down anything that is not held up by

some other force. Heavier objects (really, more massive ones) produce a bigger gravitational pull than lighter ones,

so as the heavyweight in our solar system, the Sun exerts the strongest gravitational pull.

Now if the Sun is pulling the planets, why don't they just fall in and burn up? This is because in addition to falling toward the Sun,

the planets are moving sideways. This is the same as if we have a stone on the end of a string and if we swing it around,

we are constantly pulling it towards our hand, just as the gravity of the Sun pulls the planet in, but the motion sideways

keeps the stone swinging around. Without that sideways motion, it would fall to the center; and without the pull toward the center,

it would go flying off in a straight line, which is, of course, exactly what happens if we let go of the string.