In BBC’s Human Universe: Episode 4, Prof. Brian Cox visits NASA’s Space Power Facility in Ohio, home of the world’s biggest vacuum chamber, to test Galileo Galilei‘s Leaning Tower of Pisa experiment. Galileo says:
If you drop a brick and a feather at the same time the brick will probably hit the ground first. But this is because of differences in the amount of friction between these objects and the air around them, not because their masses are different. If there were no air…
So in the vacuum room they did Galileo a favor and try this without the air!