We all know that the bright part of the Moon is illuminated by the Sun and that the phases we see are somehow related to the locations of the Sun and Moon relative to the Earth. We explore these geometric relations in this exercise. Interestingly, a poll of Harvard graduates revealed that most of them believe the dark part of the Moon is the result of portions of the Moon lying in the shadow of the Earth. Their opinion is ingenious, but dead wrong. We'll find out why.
Observations Here are some basic observations of the night sky as a starting point.
The phase of the Moon changes over the course of one month, from new, to waxing crescent, to first quarter, etc., and back to new. Likewise, as the Moon moves away in the sky from the Sun, it gets brighter. To save us all some time, the data we'd collect is reproduced here. You can see the ring structure even through binoculars. Aldebaran, the brightest star in Taurus, is just 2 below and to the left.