On Aug. 2, 1971, United States astronaut David Scott ran one of the most famous experiments ever carried out in the lunar atmosphere. Featured VideoNASA Solar System / YouTubeOn Earth, a feather and a hammer will fall at different speeds, but because of air resistance, not because of gravity or acceleration. As part of the Apollo 15 mission, Scott and fellow astronaut James Irwin managed three extravehicular activity (EVA) sessions, including the moonwalk that featured the hammer and feather experiment. as the feather and hammer touched down together. Lead image: Astronaut David Scott holds a hammer and a feather ready to test Galileo’s theory of falling bodies.