What is the Distance to the Moon and How is it Measured?

-- | April 21, 2016

Question: What is the true distance of the moon from the surface of the earth, since VLT @ Paranal can shoot a high powered laser to measure the distance? Based on surface temperatures recorded by NASA, it appears to be much closer than stated and potentially within the middle thermosphere. — Robert

Answer: From the nice description of the Moon’s distance from us provided by the Universe Today, the average distance to the Moon is on average 384,403 kilometers, which is about 238,857 miles. This distance is routinely measured using LIDAR (LIght Detection And Ranging) stations which bounce laser pulses off of the retroreflecting mirrors placed on the Moon by the Apollo astronauts. I am not aware of a LIDAR installation at the Very Large Telescope (VLT) observatory in Chile. The accuracy of these measurements is a few millimeters, which has allowed scientists to determine that the Moon is slowly moving away from us at a rate of about 3.8 cm (about 1.5 inches) per year.

Jeff Mangum

Facebook

Twitter

The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
	Founded in 1956, the NRAO provides state-of-the-art radio telescope facilities for use by the international scientific community. NRAO telescopes are open to all astronomers regardless of institutional or national affiliation. Observing time on NRAO telescopes is available on a competitive basis to qualified scientists after evaluation of research proposals on the basis of scientific merit, the capability of the instruments to do the work, and the availability of the telescope during the requested time. NRAO also provides both formal and informal programs in education and public outreach for teachers, students, the general public, and the media.
	The National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 "to promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense..."
	AUI collaborates with the scientific community and research sponsors to plan, build, and operate cutting-edge facilities. We cultivate excellence, deliver value, enhance education, and engage the public.