A solar eclipse occurs when the moon is between the earth and the sun and blocks the sun's light from reaching a small portion of the earth. Most eclipses are partial, blocking only a portion of the sun. Within a given year, a maximum of five solar eclipses can theoretically occur. However, a total eclipse visible from land occurs only about every two to four years on average. Since energy from the sun generates our weather and climate, solar studies are an important part of atmospheric research, and total eclipses offer the best opportunities to observe the sun's corona (outer atmosphere). Pictured: A partial solar eclipse visible behind high clouds from near La Dole, Switzerland, in May 1994.
