Humans first walked on the Moon 50 years ago this summer. During that first Moonwalk, the astronauts left a mirror (retroreflector) on the surface. Hal Walker led the team that developed the Lunar Laser Ranging Experiment.  He and his team then fired a laser from Earth that hit the retroreflector and was bounced back providing the most precise measurement of the distance to the Moon ever recorded. This experiment also proved that humans had visited the surface of the Moon. Learn about the science behind this experiment and the amazing work done by Hal Walker.

This program is made possible through the generous support of Boeing.