What are the phases of the moon?
The different phases of the moon are caused by the angle from
which an observer on earth can see the moon illuminated by the
sun as it orbits our planet.
As the moon makes its way around
the earth a person can look up in the sky and see various
fractions of its surface reflecting sunlight.
While there is
always half of the moon that is "lit" by the sun the observer
on earth will see the moon pass through its phases one complete
time in a span of 29 and a half days.