ABSTRACT
The Moon is officially ranked as the Earth’s satellite. Relative to its primary, it is however extremely large and massive, and it might well be more appropriate to regard the Earth–Moon system as a double planet. In the northern hemisphere, the full moon closest to the autumnal equinox, which falls around 22 September, is called Harvest Moon because the ecliptic then makes its shallowest angle with the horizon, and the retardation–that is to say, the time lapse between moonrise on successive nights–is at its minimum. Harvest Moon looks the same as any other full moon–and it is worth noting that the full moon looks no larger when low down than when high in the sky. Many theories have been advanced to explain the origin of the Moon. The most conspicuous rills on the Moon are those on the Mare Vaporum area and the Hadley Rill in the Apennine area, visited by the Apollo 15 astronauts.
