Earth-Moon distance was measured by bouncing lasers off Moon

On May 9, 1962, MIT researchers successfully bounced a laser off the Moon for the first time. The Earth-Moon distance was found using time taken by reflected light to return while its accuracy was improved following the installation of retroreflectors on Moon by Apollo 11 astronauts. The Moon is spiralling away from Earth at a rate of 3.8cm/year, experiments found.