With the launch of Apollo 15 on 26 June 1971, NASA introduced the second stage of lunar exploration with the “J” missions.  Through changes and modifications in hardware and technology, the Apollo astronauts could have longer and more frequent walks on the Moon, move around along the lunar surface more freely in the lunar roving vehicle, and conduct geologic research on the surface. Perhaps one of the best known outcomes of the Apollo 15 mission is David Scott’s demonstration of Galileo’s theory that in a vacuum, objects of differing masses will fall at the same speed and land at the same time. Scott’s use of a Falcon feather and a geologic hammer has become the physics classroom demonstration for all time.

The Ask An Expert lecture series at the National Mall building is presented every Wednesday at noon. A Museum staff member talks to the public about the history, collection, or personalities related to a specific artifact or exhibition in the Museum.