A solar eclipse is a celestial event in which the Sun is obscured by the moon. For viewers on certain parts of the Earth, the Sun may appear to completely or partially disappear. Before the mechanism of solar eclipses was understood, a great deal of superstition and mythology surrounded them. Historical documentations of solar eclipses indicate that people greeted them with fear and awe, especially when the sun was totally eclipsed.
Put simply, an eclipse happens when the moon gets between the Earth and the Sun. The moon casts a shadow on a certain section of the Earth, and while that section is in the moon's shadow, the sun appears to vanish. Typically, an eclipse of the sun will not last for more than around seven minutes, as the various astronomical bodies involved move out of alignment very quickly. Eclipses will also not strike the same place twice within 300 years, as a general rule.
In order for a solar eclipse to occur, several conditions must be satisfied. First, the moon must be in the phase known as a new moon, meaning that it is not visible in the sky. The new moon happens once a month, when the moon is between the Earth and the Sun, so that the illuminated portion of the moon faces away from Earth. The moon must also be at an angle which will intercept the sun, which is why solar eclipses are not observed on a monthly basis.
A total solar eclipse occurs when the Sun is totally covered by the moon. In another type of eclipse, an annular eclipse, the moon appears slightly smaller than the Sun, and the Sun shows up as a bright ring around the sun. In a partial eclipse, the sun is only partially obscured. In all cases, the solar eclipse falls along a predictable path which crosses the illuminated surface of the Earth.
The times and paths of eclipses can be predicted, using basic scientific principles. Many nations publish lists of predicted future eclipses, so that observers can optimally position themselves. Many people try to position themselves in the umbra of the eclipse, directly below the moon. Others settle for a position in the perumbra, where the sun will appear only partially eclipsed.
When people observe a solar eclipse, they should use eye protection, as the light of the sun can still hurt the eyes. Many people use indirect viewing methods to observe the eclipse without the risk of eye damage.
