On the moon in 1971, Commander David Scott dropped a hammer and a falcon feather to validate Galileo’s theory that without air resistance, objects fall at the same rate due to gravity regardless of mass. Given the negligible lunar atmosphere, there was no drag on the feather, both experienced the same acceleration, and both hit the ground at the same time. NASA did this because they wanted a memorable popular science experiment to do on the Moon, for kids. Very cool to watch.