Astronomy
Using Lunar Laser Ranging to Measure the Moon's Recession
Quick fact
Lunar laser ranging has measured the Moon's distance with millimeter precision and shows that it is receding at about 3.8 centimeters per year — roughly the rate your fingernails grow!
Why this is interesting
Have you ever wondered how we know the Moon is slowly drifting away from Earth? The answer lies in bouncing laser beams off mirrors left on the lunar surface!