Lunar Eclipse Overview
Science of Eclipses
The study of the Earth's shadow projected on the Moon allows us to deduce that the Earth is spherical. The Ancient Greeks worked this out. Using lunar eclipse timing, as far back as 3rd century BC Aristarchus from Samos estimated the lunar diameter. Using Eratosthene's previous measurement of the Earth's diameter, he deduced the Earth-Moon distance. Hipparcos (150 BC) and Ptolemeus (2nd century AD) improved with impressive precision the measurements of the lunar diameter and Earth-Moon distance.
In the 17th century, in order to improve longitude determination, absolute cartography made use of lunar eclipse phenomena, which were observable simultaneously from different points.
Today, during lunar eclipses, laser ranging measurements can be made with great accuracy using reflectors placed on the Moon during the Apollo and Lunakhod missions. This has allowed more precise measurement of lunar acceleration and the slow down in the Earth's rotation.
Analysis of the refracted light of the Earth's atmosphere during lunar eclipses has also made it possible to show that atmospheric ozone is confined to a layer between 50 and 80 km above the Earth's surface.