The Moon always keeps the same face to us, but not exactly the same face. Because of the tilt and shape of its orbit, we see it from slightly different angles over the course of a month. And when each month is compressed into 24 seconds, as in this video, our changing view of the Moon makes it look as if it's wobbling.

You can see the extent of this wobbling, called libration, with the help of the graphic in the lower left corner of this animation, created by the NASA Scientific Visualization Studio. The blue dot represents the sub-Earth point— the apparent center of the Moon's disk and the location on the Moon where the Earth is directly overhead.

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The lunar latitude and longitude of the sub-Earth point is a measure of the Moon's libration. For example, when the blue dot moves to the left of the meridian (the line at 0 degrees longitude), an extra bit of the Moon's western limb is rotating into view, and when it moves above the equator, a bit of the far side beyond the North Pole becomes visible.

Of course, the most noticeable monthly variation in the Moon's appearance is the cycle of phases, caused by the changing angle of the Sun as the Moon orbits the Earth. The video shows the Moon's phases as they will appear to us in 2015. The name of each crater appears when its center is within 20 degrees of the day-night line.