The moon's orbit around Earth appears so regular that civilizations have based the month on lunar motion for thousands of years. However, the moon is actually creeping slowly away from Earth. So will Earth lose its moon at some point?
Scientists determined the rate at which the moon is drifting away from Earth with help from reflective panels that NASA placed there during the Apollo missions. For more than 50 years, researchers have fired laser beams from Earth at these mirrors and measured how long it took to detect the reflected pulses. Using the speed of light, scientists estimated that the moon is straying away from Earth by about 1.5 inches (3.8 centimeters) per year, roughly the rate at which fingernails grow, according to NASA.
