1. Does the Moon Rotate?
The Moon is familiar; it always looks the same. We know that the Earth rotates, that’s
why the Sun, Moon and stars seem to move through the sky every day. But does the Moon
rotate? And if the Moon rotates, why do we alway see the same side – it never seems to change.
Well, the Moon does rotate. In fact, the Moon takes 27.3 days to turn once on its axis.
But the Moon also takes 27.3 days to complete one orbit around the Earth. Because the Moon’s
rotation time is exactly the same amount of time it takes to complete an orbit, it always presents
the same face to the Earth, and one face away.
Because it only presents one face to the Earth, astronomers say that the Moon is tidally
locked to the Earth. Although the Moon looks like a perfectly smooth ball, it has slight
differences in the shape of its gravity field. A long time ago, the Moon did rotate. But each time
it turned, the Earth’s gravity tugged at it, slowing down
its rotation until it only presented one face to the Earth.
At that point, the Moon was tidally locked, and from
our perspective, it doesn’t seem to rotate.
Many other moons in the Solar System are also
tidally locked to their planet. In fact, most of Jupiter’s
large moons are tidally locked.
So, to answer the question: does the Moon rotate? The
Moon rotates once every 27.3 days; the same amount of
time that it takes to go around the Earth, and so it always presents the same face to the Earth.
Source: http://www.universetoday.com/19699/does-the-moon-rotate/