Which way is down? Falling balls and planets

Do heavier things fall faster? Many people think so, but the answer is surprising. Gravity pulls a heavy ball with a bigger force than a light ball, but the heavy ball also needs more force to speed up, so both speed up in the same way. If there were no air, a feather and a metal ball would hit the ground together. On Earth, air pushes against everything that falls. This is air resistance. A wide, light thing such as a sheet of paper or a feather gets pushed back a lot, so it falls slowly. A crumpled paper ball has less area for the air to push on, so it falls much faster than a flat sheet. A parachute is a very wide cloth for this reason. When we compare balls in a fair test, we drop them from the same height at the same time. Only the thing we are testing changes.