4 Mb MP4 movie of the demonstration
At the end of the last Apollo 15 moon walk, Commander David Scott (pictured above) performed a live demonstration for the television cameras. He held out a geologic hammer and a feather and dropped them at the same time. Because they were essentially in a vacuum, there was no air resistance and the feather fell at the same rate as the hammer, as Galileo had concluded hundreds of years before - all objects released together fall at the same rate regardless of mass. Mission Controller Joe Allen described the demonstration in the "Apollo 15 Preliminary Science Report":
During the final minutes of the third extravehicular activity, a short demonstration
experiment was conducted. A heavy object (a 1.32-kg aluminum geological hammer) and
a light object (a 0.03-kg* falcon feather) were released simultaneously from
approximately the same height (approximately 1.6 m) and were allowed to fall to the
surface. Within the accuracy of the simultaneous release, the objects were observed
to undergo the same acceleration and strike the lunar surface simultaneously, which
was a result predicted by well-established theory, but a result nonetheless
reassuring considering both the number of viewers that witnessed the experiment and
the fact that the homeward journey was based critically on the validity of the
particular theory being tested.
Joe Allen, NASA SP-289, Apollo 15 Preliminary Science Report, Summary of Scientific
Results, p. 2-11
(* the 0.03-kg value is too high, typical feathers have masses between 0.0003 and 0.003 kg (0.3 - 3 grams), this may be due to a typo in the report.)
Larger Version
- 20 Mb MP4 movie
Author/Curator: