The Moon is the Earths natural satellite although we see it as a bright object in the night sky it only reflects about 10% of the light falling on it ( albedo 0.12) so it is quite poor compared with the 39% reflected from the Earth ( albedo 0.39 ). The moon always keeps one face towards the Earth, this often misleads people into thinking that the moon does not rotate, in fact it does but at the same rate as it orbits the Earth. The phenomenon of the same face towards a planet is not uncommon and is known as synchronous rotation. Another common misconception is that the Moon has a dark side actually it does not. Although we cannot see the other side of the moon it gets just as much light as the side we can see, it is just that the days are 14 Earth days of daylight and 14 days of night.
|
Distance from the Earth |
384400 km |
|
Orbital Period |
27.3217 Days |
|
Inclination |
5.15 degrees |
|
Eccentricity |
0.055 |
|
Diameter |
3476 km |
|
Density |
3340 kg/m3 |
|
Albedo |
0.12 |
|
Mean Magnitude |
-12.7 |
The Earth is about 81 times heavier than the moon and both orbit a common centre of mass, this happens to be about 1700 km below the surface of the Earth.
The most obvious feature of the Moon from the Earth is its phase. We begin with a New moon when we see nothing, this progresses or waxes through crescent shapes to the first quarter then via the gibbous phase to the full Moon. We then see the Moon wane through gibbous to last quarter and finally to a crescent and then New Moon again.
It is a mere coincidence that the Moon is the same angular size as the Sun and also a stroke of fortune that its orbit is in the same plane as the path of the Sun, however it does give us the good fortune of enjoying the spectacle of an eclipse. See the eclipse in 1999 as it will be seen from Bingham.