Visually Observing Lunar Rotation
Why is we continue to see the same side of the moon?
Because it takes the same amount of time for the moon to rotate
about its axis as it is to revolve around the Earth, the moon is
always facing the same hemisphere towards the Earth.
Here's a visual you can try: cut out an arrow shaped piece of paper
and tape it to the outer edge of a CD with the arrow pointing toward
the central hole of the CD. Put your finger through the CD. With
your finger representing the Earth and the arrow representing the
moon, you can spin the CD and note that while the arrow is changing
directions (it is spinning on its axis) it is always pointing toward
the middle (its revolution is the same period as its rotation).
Greg (Roberto Gregorius)
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Update: June 2012