Bouncing Light Off the Moon: The Geometry of Lunar Retroreflectors

When the Apollo astronauts walked on the moon, they left behind several unassuming panels covered in small, geometric silica prisms. Decades later, these Lunar Ranging Retroreflectors remain the only Apollo experiments still actively gathering data, and they are the key to our understanding of celestial mechanics. Unlike a standard mirror that scatters light, a retroreflector is mathematically d...