In air, the feather falls slower than the ball, because the shape of the feather creates a greater air resistance. When the objects are dropped within a vacuum, there is no air or any other substance for the object to resist. Thus, both objects will drop at the same rate.

Both the feather and the ball drop as a result of gravitational pull. The motion of a falling object accelerates at an even rate. Falling objects push air out of their way, and their descent is slowed by air resistance. The extent of the air resistance depends upon the size, shape and speed of the object. As the speed of the descent increases, the air resistance also increases. Since air resistance is equal to the Earth’s gravitational pull, all falling objects will eventually achieve a final speed that no longer increases.

In a vacuum, the pressure of the gas is much smaller than the air pressure. A vacuum theoretically means a completely empty space, which, according to quantum mechanics, is not actually possible. The lowest possible energy state, or zero-point energy, is physically the closest to an absolute vacuum.

Skydivers make use of the slowing force of air resistance when they open their parachutes. The parachute slows the diver’s descent, because it increases the area of resistance.