The Earth's Moon
For Earth being rather small, we have an impressive Moon!
The moon orbits Earth every 27.3 days (sidereal period),
also equal to the time it takes to rotate once on its axis.
Consequently, we see only one hemisphere of the Moon from Earth,
the near side. The far side is sometimes termed the `dark side'. But beware,
this is a misnomer!
The Moon lies in nearly the same plane as the Sun-Earth system (with just a 5o relative tilt). We always see the Moon along the ecliptic. To understand the Phases of the Moon, we must look at the location of the Moon relative to the Sun and our view from Earth.
New Moon:
the Moon is located between Earth and the Sun. The side of the Moon
we see is facing away from the Sun and is dark.
Full Moon: the Earth is between the Sun and Moon.
In this orientation, the Moon's entire surface is well
lit. Why do you NEVER see a full moon in the middle of the day?
Crescent (less than quarter) or Gibbous Moon (more than quarter).
