By Dave Fuller on 1/12/2014 10:17 PM
Lunar libration gif animationThe Moon is tidally locked with Earth, meaning it only shows one "face" to us, no matter where it is in its orbit around Earth. However, from Earth, we can see more than 50% of the Moon's surface due to libration. See graphic at right for what libration looks like over the period of a month. 

Here's the Wikipedia entry detailing why we see more than just 50% (in fact, up to 59%):



There are three types of lunar libration:



Libration in longitude results from the eccentricity of the Moon's orbit around Earth; the Moon's rotation sometimes leads and sometimes lags its orbital position. Libration in latitude results from a slight inclination between the Moon's axis of rotation and the normal to the plane of its orbit around Earth. Its origin is analogous to how the seasons arise from Earth's revolution about the Sun....

The Nightlight

This blog includes what to see in the night and daytime skies, thoughts on telescopes, binoculars, and other astronomy observing accessories and equipment, plus my own occasional notes on objects I've seen and observed. Oh, and the random theater or other "my take on life" post. In other words, there is always something interesting. Check it out.