06. Why Are Planets Round?

This is a story about gravity. We learn that gravity is a force that works everywhere, even in space and it always pulls towards the centre of an object. When we point to “down’ we always point to the center of the Earth, no matter where we are. With gravity pulling towards the center, the smallest shape anything can be is a ball, so almost all planets have that shape, but not all. The big ones bulge out in the middle and very tiny worlds; with almost no gravity have odd shapes, like the asteroid that looks like a peanut! We see gravity at work in a gravity well, and fall into the ultimate gravity trap, the black hole!