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Solar Eclipses

The angular size of the Moon and Sun are nearly identical as seen from Earth's surface. The shadow thrown on the Earth from the Moon, creating a Solar Eclipse is very small. For this reason, to see a total solar eclipse, you have to be in just the right spot on the earth. The "path of totality" is never more than 167 miles in diameter, and is usually less. Very few people have seen a total eclipse on the earth.


Not only is position on the Earth important, but the Moon-Earth distance is important. If the moon is close to the Earth, the Earth will pass through the umbra, the darkest region of the shadow. The Moon may pass directly in front of the Sun, however, if the Earth-Moon distance is far, the Moon angular size will be too small to fully cover the Sun. The Earth will instead pass through the penumbra shadow.

Total Solar Eclipses occur when the umbra of the Moon's shadow touches a region on the surface of the Earth. Partial Solar Eclipses occur when the penumbra of the Moon's shadow passes over a region on the Earth's surface. Annular Solar Eclipses occur when a region on the Earth's surface is in line with the umbra, but the distances are such that the tip of the umbra does not reach the Earth's surface.