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Astronomy and space science

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The Moon

The Moon orbits the Earth, so it is called a satellite of Earth. The Moon is a natural satellite. No-one built it or launched it into space.

Gravitational forces between the Moon and the Earth keep the Moon in orbit. The Moon does not produce light. But it does reflect light from the Sun, which is how we are able to see it from Earth. (Only stars produce light and they are called luminous for that reason.)

Phases of the Moon

It takes the Moon 28 days to make a complete orbit of the Earth. As it orbits, we see the Moon lit from different angles. This is why we see phases of the Moon.

Sometimes the Moon looks like a full circle. That is called a 'full Moon'. At other times we see a crescent shaped Moon, because we can only see the edge of the part that is lit by the Sun.

Remember that we can only see the part of the Moon that reflects the Sun's light. How much of that we can see depends upon the position of the Moon in its orbit.

This slideshow shows the phases of the Moon, as seen from the Earth.

Phases of the moon

no moon is visible

New moon

Eclipse of the Moon

A common mistake is to think that the phases of the Moon happen because the Earth gets in the way, and casts its shadow onto the Moon. That is not how the phases are caused.

However sometimes it does happen that the Earth's shadow falls on the Moon. Then we get an eclipse of the Moon. The whole Moon goes from full, to dark, and back again to full, in the course of a few hours.

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