
	Introduction The influence of The Moon Mythology Astronomy

The Moon is the only natural satellite of the Earth:

Orbit: Diameter: Mass:		384,400 km from Earth 3476 km 7.35e22 kg

Astronomy

The Moon, of course, has been known since antiquity, and it is the second brightest object in the sky after the Sun. The Moon is about one-quarter of the size of the Earth and has only one-sixth the amount of gravity. This means you could jump six times higher than on Earth and take giant steps to move about, just like the first men to walk on the Moon did.

The Moon orbits around the Earth once every month, and during this orbit, the angle between the Earth, the Moon and the Sun changes, a phenomenon known as the cycle of the Moon's phases. The time between successive 'new moons' is 29.5 days (709 hours), slightly different from the Moon's orbital period (which is measured against the stars), as the Earth moves a significant distance in its orbit around the Sun in that time.

The gravitational forces between the Earth and the Moon cause some interesting effects. The most obvious of these is the tides. The Moon's gravitational attraction is stronger on the side of the Earth nearest to the Moon, and weaker on the opposite side. Since the Earth is not particularly rigid, and the oceans are definitely not so, there is a pull exerted along a line toward the Moon. There are two small 'bulges', one in the direction of the Moon and one directly opposite. The effect is much stronger in the ocean water than in the solid crust of the Earth. And because the Earth rotates much faster than the Moon moves in its orbit, the 'bulges' move around the Earth about once a day giving two high tides per day. (This is a greatly simplified explanation, and the actions of the actual tides, especially near the coasts, for example, are much more complex.)

The Moon appears to 'wobble' a bit (due to its slightly non-circular orbit) so that a few extra degrees of its far side, which is never seen on Earth, can be seen from time to time. The majority of the far side was completely unknown until the Soviet spacecraft Luna 3 photographed it in 1959. It is important to note that there is no "dark side" of the Moon, as many people still believe. Apart from a few deep craters near the poles, all parts of the Moon get sunlight half the time. The use of the term 'dark side of the Moon', whilst leading to some confusion, has also been used metaphorically to indicate the unknown, or mysterious, much in the sense of the phrase 'darkest Africa'.

The Moon has no global magnetic field, and there is no atmosphere at all, so visitors from Earth need to take their own air supplies. The temperature on the Moon's surface can rise to 100 degrees Centigrade (212F), and can plunge to minus 150 degrees C (-240F) during Lunar nights, which last two weeks.

If you would like to know more about the solar system, Starscine suggests the following websites: