Bad Astronomy: Misconceptions and Misuses Revealed, from ...

32 BAD ASTRONOMY BEGINS AT HOME
The bright side, and therefore the dark side as well, is not a fixed
place, but appears to move as the Moon rotates.
Seen from the surface of the Earth, the Moon does not appear
to rotate. It seems to show the same face to us all the time. Actually
it does spin; it’s just that it spins once for every time it goes
around the Earth. Its rotation teams up with its revolution in such
a way that it always shows that one face to us. We call that face
the near side of the Moon. The other side, the one we never see, is
called the far side. The far side of the Moon has only been seen by
probes or by astronauts who have actually orbited the Moon. Since
it’s remote and not well known, the far side of the Moon has become
synonymous with something terribly far away or unexplored.
The problem is, people confuse the far side with the dark side.
You almost never hear the phrase “far side of the Moon.” It’s
always the “dark side of the Moon.” This phrase isn’t really wrong,
but it is inaccurate.
Like the Earth, the Moon spins. The Earth spins once every 24
hours, so that someone standing on its surface sees the Sun go up
and down once a day. As seen from outside the Earth, that person
is on the dark side of the Earth when he or she is on the half that
is facing away from the Sun. But the dark side is not a permanent
feature! Wait a few hours, and the Earth spins enough to bring
that person back into the sunlight. He or she is now on the bright
side of the Earth. No part of the Earth is on the dark side forever.
The same goes for the Moon, except its day is 29 of our Earthdays
long. Someone on the Moon will see the sun set two weeks
after it rises! Since half the Moon is in sunlight and half in darkness,
there is technically a dark side to the Moon, but it changes as
the Moon rotates. Except near the poles, a single point on the
Moon is in sunlight, then in darkness, for two weeks.
You can see that the dark side of the Moon is simply just the
night side of the Moon. It is no more a fixed feature than the night
side of the Earth. Sometimes the far side is the dark side, but it’s
also sometimes the bright side. It just depends on when you look.
One of the best selling music albums of all time is Pink Floyd’s
Dark Side of the Moon. It may be popular, but astronomically it’s
in eclipse.