Lunar eclipse

A lunar eclipse is produced when the moon passes partially or totally into the shadow of the Earth.

This happens when the Sun, the Earth and the Moon are almost aligned with the Earth between the Sun and the Moon. It is a frequent phenomenon observable by everyone situated in the night side of the Earth.

One must not get this phenomenon mixed up with a solar eclipse that also occurs when the three bodies are aligned, but the Moon is in this case between the Sun and the Earth. A solar eclipse is more rare and only seen by people situated near a small area of Earth (on the day side).

• To distinguish between a Lunar eclipse and a Solar eclipse.
• To illustrate the different types of lunar eclipses.
• To identify the dark and semi-light zones.

When the moon is behind the Earth in relation to the sun (full moon), it is possible to define three regions of light:

• A large region where all of the Suns rays reach the moon. The moon is very bright.
• The semi-light zone (of the earsh) which is the region where only a part of the rays emitted from the sun reach the Earth. It is therefore not as bright because there is less light.
• The dark zone is a cone-shaped region behind the Earth. Objects that cross here do not receive any ray of direct sunlight. The Moon is not bright. In reality, the Moon still shines a weak reddish colour that comes from Sun rays diffused by the fine layer of the Earth`s atmosphere.

When the moon passes completely into the dark zone, this causes a total lunar eclipse.

If only a part of the Moon enters into the dark zone, this is called a partial lunar eclipse.

If the Moon is totally or atleast partly in the semi-light zone, without crossing into the dark zone, it is a semi-light eclipse which is not interesting since it only decreases the light and usually goes unnoticed.

This animation only illustrates the first two cases.