From a thread in engineering: My point is this: though the earth accelerates the feather and the ball bearing equally, the feather and the ball bearing do not accelerate the earth equally. As a result, the time to impact for the ball bearing will be less than for the feather. For objects that small, it may not be noticeable, but it is still there. To notice it, you really need bigger masses. Any object arbitrarily low in mass will hit the earth in about two seconds when dropped from 9.8m. But lets say you could drop another earth from 9.8m above this one. Since each is being accelerated toward the other at 9.8m/s^2, impact would occur in 1s.