Scientists who analyze data from the Lunar Laser Ranging Experiment have reported some watershed results from these long-term experiments, begun 25 years ago when the Apollo 11 astronauts deployed a reflector array in the Sea of Tranquillity. "Using the Lunar Laser Ranging Experiment, we have been able to improve, by orders of magnitude, measurements of the Moon's rotation," said Jet Propulsion Laboratory team investigator Dr. Jean Dickey. "We also have strong evidence that the Moon has a liquid core, and laser ranging has allowed us to determine with great accuracy the rate at which the Moon is gradually receding from the Earth."

The first laser ranging retroreflector was positioned on the Moon in 1969 by the Apollo 11 astronauts. By beaming laser pulses at the reflector from Earth, scientists have been able to determine the round-trip travel time that gives the distance between the two bodies at any time to an accuracy of about 3 centimeters. The laser reflector consists of 100 fused silica half-cubes, called corner cubes, mounted in a 46-centimeter square aluminum panel. Each corner cube is 3.8 centimeters in diameter. Corner cubes reflect a beam of light directly back toward the point of origin.
NASA - Accuracy of Eclipse Predictions

Have a good one!:jointsmile: