Apollo 15 gravity demonstration. Astronaut photograph of a geological hammer and a feather used to demonstrate the effect of gravity on the Moon's surface. The hammer and feather were released at the same time from the same height, and landed on the Moon's surface simultaneously. On Earth the feather would fall more slowly than the hammer due to the resistance of air molecules. The near vacuum of the Moon means there is no air resistance and so objects fall at the same rate regardless of mass.