In addition to flying, landing, and returning from the moon in 1969 — NASA's Apollo 11 crew helped with a series of scientific experiments. One of them was to leave a special instrument with lots of little reflectors on the surface of the moon. The goal of that experiment was to beam a laser at the moon. Today on the show, Scientist-In-Residence Regina G. Barber talks to host Aaron Scott about the lunar laser ranging experiment — and how shooting that laser helped us better understand one of Einstein's theories. Follow Aaron on Twitter @AaronScottNPR and Regina @ScienceRegina. Reach the show by beaming an email to ShortWave@NPR.org.