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  phases of the Moon
  what is a lunar eclipse?
  the coloured Moon
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the phases of the Moon


The appearance of the Moon in the sky changes from day to day. These changing shapes are called the Moon's phases.


Sometimes we see the whole Moon lit up (full Moon). Sometimes only half of it is lit (half Moon). Sometimes it's only a thin, curved shape (crescent Moon) or even not there at all (new Moon). What's going on? One thing is for sure, the Moon itself doesn't change shape!


The bright shape of the Moon we can see is just that part of the Moon which is facing Earth and which at the same time is facing the Sun. You can see what we mean in the diagram below. Put your cursor over the 8 Moon phases and get a 'space eye' view of the Sun, Earth and Moon, and an 'Earth eye' view of the Moon.

Only the part of the Moon which is facing the Sun has sunlight falling on it so the rest of the Moon is in shadow and appears dark to us.


The Moon phase we see just happens to be that part of the sunlit Moon which is facing Earth.

Phases of the Moon - an interactive diagram.
the phases of the Moon
Sun What you see from the Earth
Appearance of the Moon, as seen from the Earh, at each of the eight positions
Time 1 to 8
Image of the Moon changing phases

One of the magical things about the Moon is that the time it takes to spin on its axis is exactly the same as the time it takes to orbit the Earth. In theory, therefore, on Earth we should always see the same half, and only half, of the Moon. Because Nature is not always that simple, there are three reasons why, over time, we can see more than half of the Moon’s surface.


These effects are called librations and you can see them in this movie, which was created by taking an image of the Moon every day for a month and putting the images in a sequence. This is a great way to see not only the phases of the Moon, but also the wobbles (librations) it suffers during a month when viewed from Earth.

[Places on the Moon have day and night. - The Moon takes about 28 days to rotate on its axis. That means that places on the Moon have daylight for about 14 Earth days - and the nights are just as long!]
Image of an illustration of the Moon
Image of a blue button with a white arrow Image of a blue button with a white arrow Image of a blue button with a white arrow







One thing phases of the Moon ARE NOT CAUSED BY is the shadow of the Earth falling on the Moon. When that happens, it is called a lunar eclipse. Check out the next section for more on lunar eclipses.




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