Back in the 16th century it was still believed that light objects would fall slower than heavy objects. The Italian scientists Galileo Galilei allegedly proved this theory to be wrong in a famous experiment where he dropped two balls of equal size but different masses from the leaning tower of Pisa. There is some controversy as to whether Galileo actually performed the experiment, but this experiment has been repeated in modern times in many ways. Two of such notable repetitions are shown below. The first is that carried out by astronaut Dave Scott of the Apollo 15 mission on the moon.
The second was conducted at NASA's massive Space Simulation Chamber in Ohio.