On 20 July 2009 there were worldwide celebrations for the fortieth anniversary of the day astronauts from Apollo 11 mission became the first humans to set foot on the Moon.

The Moon is Earth’s only natural satellite. With the exception of Mercury and Venus all the planets in the solar system have moons, the number of moons attributed to some planets are increasing as smaller moons continue to be discovered. Currently, the statistics are Earth 1 moon; Mars 2 moons; Jupiter 63 moons; Saturn 61 moons; Uranus 27 moons; Neptune 13 moons; Pluto 3 moons.

The distance between the Earth and the Moon varies between 363,300 to 405,500 depending on the orbit; the mean is 384,400 kms. Because the revolution of the Moon and its rotation around Earth are synchronised, one side of the Moon is always turned towards Earth, and the other side is turned away, this is sometimes called the dark side of the Moon, however it is not dark merely unseen from Earth.

The Moon does not emit light itself, it only reflects the light of the Sun, consequently the way we see the Moon depends upon the relative positions of Moon, Sun and Earth and these are constantly changing. The Moon orbits the Earth every 27.3 days in an elliptical orbit. The Earth spins on its tilted axis once per day and orbits the Sun elliptically and returns to the same position every 365.26 days.

Over a 27.3 day period the Moon appears to change shape, from a new Moon (the Moon is between The Sun and the Earth) to the round full Moon (the Earth is between the Sun and the Moon). This phenomenon occurs because we can only see the part of the Moon that is illuminated as it faces the Sun, and this lit portion changes as the Moon orbits the Earth. These lunar phases are repeated on a  27.3 day cycle, as the Moon orbits the Earth. 

Lunar eclipses occur when the whole of the Moon (total eclipse) or a portion of the Moon (partial eclipse) passes through the Earth’s shadow. Lunar eclipses can only occur at the full moon phase, when the Earth is between the Moon and the Sun. The next total lunar eclipse will take place on 21 December 2010 and will be visible at moonrise in Australia.

Solar eclipses occur when the Moon passes between the Earth and the Sun, where the whole or part of the Sun is obscured by the Moon. Solar eclipses can only occur at the new moon phase, when the Moon is between the Sun and the Earth. A total solar eclipse occurred over Asia this month, the next will occur in July 2010, however we are unlikely to have a good view of this in Australia.

On Tamborine Mountain we have beautiful views of the moon, and as a bonus we may sometimes see interesting optical effects such as rings around the moon, moon coronas and moon rainbows.

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