Libration

We missed out on seeing the lunar eclipse last night due to the clouds, but here's an interesting fact about viewing the visible moon and a very cool picture to go with it! Through a process known as Libration it is possible to "view" more than 50% of the visible surface which is tidally locked in a fixed position relative to Earth.

There are three types of libration:

Libration in longitude is a consequence of the Moon's orbit around Earth being somewhat eccentric, so that the Moon's rotation sometimes leads and sometimes lags its orbital position.

Libration in latitude is a consequence of the Moon's axis of rotation being slightly inclined to the normal to the plane of its orbit around Earth. Its origin is analogous to the way in which the seasons arise from Earth's revolution about the Sun.

Diurnal libration is a small daily oscillation due to the Earth's rotation, which carries an observer first to one side and then to the other side of the straight line joining Earth's center to the Moon's center, allowing the observer to look first around one side of the Moon and then around the other.

Posted by Ted Zarras at 5:18 PM