Lunar and Solar Eclipse

What is an eclipse?

Sometimes during their orbits, the moon and the Earth form a line with the sun.

There are two kinds of eclipses - lunar and solar.

As seen from the earth, a solar eclipse is a type of eclipse that occurs when the moon passes between the sun and Earth, and the moon fully or partially blocks the sun. The image below depicts the moon in the middle of the sun and the Earth and that creates a penumbra and an umbra.

Diagram of earth, moon and sun during eclipse

A solar eclipse can only occur during a new moon, when the sun and the moon are aligned. In a total eclipse, the disk of the sun is fully obscured by the moon. In partial and annular eclipses only part of the sun is obscured.

This image is of a total eclipse captured on film in 1999.

During a solar eclipse, the moon blocks the light of the sun and a shadow of the moon is cast on the earth's surface.
Actually, the moon casts two shadows towards Earth. One shadow is called the umbra which becomes smaller as it reaches the earth. The second shadow is called the penumbra which becomes larger as it reaches the earth. A total solar eclipse, or a complete blocking out of the sun's light, can only be seen from the area on the earth's surface that enters the moon's umbra, the smaller shadow. People viewing the eclipse from the area of the earth's surface that enters the penumbra, the larger shadow, will see only a partial blocking of the sun.

Look at the image again

Diagram of position of earth, moon and sun during eclipse

In a solar eclipse, the moon moves between the earth and the sun. When this happens, part of the sun's light is blocked. The sky slowly gets dark as the moon moves in front of the sun. When the moon and sun are in a perfect line, it is called a total eclipse. These are very rare. Most people only see one in their lifetime.

Lunar Eclipse

A lunar eclipse occurs when the moon passes directly behind the earth into its umbra (shadow). This can occur only when the sun, Earth, and moon are aligned exactly, or very closely so, with the Earth in the middle. Hence, a lunar eclipse can only occur the night of a full moon.

Geometry of a Lunar Eclipse

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