The Moon does not emit its own light, shining instead by reflecting sunlight. Depending on the relative positions of the Earth, Sun and Moon, varying amounts of the lunar surface appear to be illuminated.
When the Moon
is between the Earth and the Sun
, the bright side of the Moon
is facing away from the Earth, and we have a New Moon
(position A in the diagram below).
The New Moon
rises at sunrise, transits the meridian
at noon and sets at sunset. The New Moon
phase repeats every 29.531 days - one synodic month.
eclipses can only occur within a few days of the New Moon
, but they do not happen at every New Moon
. This is due to the 5.1 degree tilt of the Moon
around the Earth compared to the Earth's orbit
around the Sun
. The intersection of these two orbits
is the line of nodes, and solar
eclipses occur when this line is pointing towards the centre of the Sun
's motion around the Earth, with the Sun
illuminating only one side of the Earth and Moon