Explanation:
Our Moon's appearance changes nightly.
This time-lapse sequence shows
what our Moon looks like during a
lunation, a complete lunar cycle.
As the
Moon orbits the
Earth,
the half illuminated by the
Sun
first becomes increasingly visible,
then decreasingly visible.
The Moon
always keeps the same face toward the Earth.
The Moon's apparent size changes slightly, though,
and a slight wobble called a
libration is discernible as it progresses along its elliptical orbit.
During the
cycle, sunlight reflects from the
Moon
at different angles, and so illuminates different features differently.
A full
lunation takes about 29.5 days, just under a month
(moon-th).
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