I couldn't see how anything could possibly stay in orbit when gravity pulled everything together until I wrote a computer program to simulate orbits in 2d: http

I couldn't see how anything could possibly stay in orbit when gravity pulled everything together until I wrote a computer program to simulate orbits in 2d: http://ln-s.net/7oFZ http://ln-s.net/7oFZ It was really enlightening to fiddle with the constants and to create events that show how kinetic and potential energy interact in space.