Why do planets float in space? by Richard Muller
Answer by Richard Muller:
They only appear to be floating. In fact, they are being accelerated towards the Sun, but their velocity is so high that they miss; in fact they wind up going in a near circle. But physicists think of that as falling.
Shoot a cannon, and the cannonball falls towards the Earth and hits it. Shoot it fast enough, and as it falls, the Earth curves away, and the ball winds up getting no closer. So, although it is “falling”, it goes in a circle around the Earth. That’s what we call an “orbit”. Physicists think of orbiting satellites as satellites that are constantly falling.
Similarly for the planets around the Sun. If they weren’t moving so rapidly in a sideways direction, they would fall into the Sun.