It is a kind of oscillation that presents the lunar globe. It can be of three types:
1.- Libration in length, because the orbital velocity of the Moon varies (Kepler's Law II), while the rotation speed of our satellite around its own axis is uniform.
2.- Libration in latitude, because the lunar equator is inclined with respect to the plane of the lunar orbit about 6 degrees.
3.- Daytime libration, due to the fact that the Earth observer, in rotation with our planet, sees the lunar globe from different perspectives during the same day.
These three combined oscillatory movements make the Moon, although it always directs the same face towards the Earth, in practice it shows more than 50 percent of its surface (59 percent). Even without moving from Earth it is possible, therefore, to observe a small portion of the other side of the Moon.
The liberation movement was described by Galileo Galilei, who defined it hesitation.
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