Question

why planeys revolve around the sun

Answer 1

sun is most heaviest object of our solar system is it has high gravitational force, The lighter object orbits the heavier one,Sun is pulling the planets
in addition to falling toward the Sun, the planets are moving sideways. This is the same as if you have a weight on the end of a string. If you swing it around, you are constantly pulling it toward your hand, just as the gravity of the Sun pulls the planet in, but the motion sideways keeps the ball swinging around. Without that sideways motion, it would fall to the center

Answer 2

According to Newtonian laws of gravitation, the planets rotate in that exact speed that allows the gravitational pull of sun to keep the planets in orbit and enough centrifugal force to resist falling in and collapsing. So, fixed orbits are there for revolution.
Later, Einstein published in his theory of relativity that the spacetime is warped and the weight of the sun allows it to warp the spacetime beneath it and the round bodies of planets move around the sun due to the curved spacetime. This is illustrated by the example that in a bowl, if you leave a ball with a certain amount of velocity in the curve, the ball rotates in circles and ultimately collapses in the middle. In case of planets, a certain velocity helps exert enough centrifugal force to keep it in orbit.
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