Thursday, February 20, 2014

lunar distance - how high the moon

Click to enlarge
In astronomy, a lunar distance (LD) is a measurement of the distance from the Earth to the Moon. The average distance from Earth to the Moon is 384,400 km (238,900 mi). (about 389 LD is 1 AU, the Earth-Sun distance) The actual distance varies over the course of the orbit of the moon, from 363,104 km (225,622 mi) at the perigee and 405,696 km (252,088 mi) at apogee, resulting in a differential range of 42,592 km (26,465 mi).
High-precision measurements of the lunar distance are made by measuring the time taken for light to travel between LIDAR stations on Earth and retroreflectors placed on the Moon.
The Moon is spiraling away from Earth at an average rate of 3.8 cm (1.5 in) per year, as detected by the Lunar Laser Ranging Experiment. The recession rate is considered anomalously high. By coincidence, the diameter of corner cubes in retroreflectors on the Moon is also 3.8 cm (1.5 in).
Read More
From Wikipedia, the free encyclopedia

Hear Less Paul & Mary Ford "How  high the Moon"