The Apollo astronauts left mirrors on the Moon that scientists still bounce lasers off 57 years later, and the round-trip measurement is precise enough to track the Moon drifting away from Earth at the speed your fingernails grow - Space Daily

The retroreflectors left on the Moon by Apollo 11, 14, and 15 still return laser pulses fired from Earth, and 57 years of data have measured the Moon's recession at 3.8 centimeters per year while confirming Einstein's general relativity to extraordinary preci…