"That's one small step for man, one giant leap for mankind." Was what Neil Armstrong said as he became the first human being to set foot on the Moon. Apparently though, he fluffed his lines a bit, he was meant to say "for a man", but we'll let him off. The Moon itself was formed in a cataclysmic event over four billion years ago. It is now believed that a protoplanet the size of Mars collided with the forming Earth. This would have thrown out vast amounts of material into orbit, where it eventually coalesced into the Moon.

The Apollo astronauts discovered that most of the lunar rocks are made out of mafic basalt from around the time of the Late Heavy Bombardment which occurred 3800-4100 mya. Basalt is a simple rock that also makes up most of the oceanic crust on Earth. Unlike the Earth however, the Moon appears to be bone dry. Although it is possible that water may exist as ice in craters at the poles that never see the Sun. Apollo 15 astronauts did however find what is called The Genesis Rock, a piece of the Moon's original crust. It was made of Anorthosite, a much more complex rock.

Earthrise. This photo was taken by Apollo 8 astronauts as they circled the Moon.

The Moon's orbit around the Earth is locked with its rotation, meaning that it always keeps the same side facing Earth. The other side that faces away from Earth, known as "the dark side" is not actually dark, it gets the same amount of sunlight as the other side. But people do now neem to be calling it "the far side" more. The Moon may seem like it can't effect Earth, but it does. The Moon's gravity is what causes the tides. The oceans are actually attracted to the Moon enough to make the sea rise and fall. The Moon also helps to stabilise the Earth's axis tilt and keeps it at a steady 23.5^o, give or take a bit.

By extraordinary co-incidence, the Moon just happens to be 400 time smaller than the Sun, and also 400 time closer. This means that they appear about the same size in the sky. So about once every 18 months or so, somewhere on the Earth the Moon moves in front of the Sun. This is a solar eclipse. During one, the corona (the outer atmosphere of the Sun) becomes visible.

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