A hammer and a feather fall at the exact same speed on the Moon.

On August 2, 1971, Commander David Scott performed one of the most famous physics experiments in history during the Apollo 15 mission. Standing on the lunar surface at the Hadley-Apennine landing site, he held a 1.32-kilogram aluminum geologist's hammer in one hand and a 0.03-kilogram falcon feather in the other. He released them from a height of approximately 1.6 meters while the television camera recorded the event for millions of viewers on Earth.The experiment was a live demonstration of a principle first proposed by Galileo Galilei in the late 16th century. Galileo hypothesized that in a vacuum, all objects fall with the same acceleration regardless of their mass. On Earth, air resistance pushes back against light objects like feathers, causing them to flutter and fall slowly. However, the Moon has an extremely thin exosphere that acts as a near-perfect vacuum, eliminating aerodynamic drag.When Scott released the items, the Moon's gravity, which is about one-sixth as strong as Earth's, pulled on both objects equally. They accelerated toward the surface at roughly 1.62 meters per second squared. As predicted, they struck the lunar dust at the exact same moment, prompting Scott to remark that it proved Mr. Galileo was correct in his findings.This demonstration remains a cornerstone of physics education, illustrating the Equivalence Principle. This principle later became a fundamental part of Albert Einstein’s General Theory of Relativity. By conducting this test in a natural vacuum, NASA provided visual proof of laws that had been mathematically accepted but were difficult to demonstrate so perfectly within Earth's atmosphere.