Solar Wind Sherpas
Eclipses
What is a Total Solar Eclipse?
A total solar eclipse (TSE) occurs when the Moon passes between the Earth and the Sun covering the solar disk and casting a shadow over Earth. Specifically, the Sun’s diameter, which is 400 times bigger than the Moon’s and 400 times farther from Earth than the Moon, combined with planetary motion, results in the alignment of the Sun, the Moon and the Earth every 12 to 18 months.
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Totality occurs when the Sun’s disk is completely covered by the Moon. This occurs because the Moon is at the correct distance from the Earth to appear to be the same size as the Sun’s disk. It is only during totality that we are able to see the Sun’s atmosphere, or corona. The brightness of the solar disk hides the dimmer atmosphere on a regular basis.
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Eclipse Sunglasses: Why and When?
Eclipse sunglasses are a safe way to view the Sun at any time other than during totality. In particular, as the Moon starts to cover the Sun (this is called first contact), look through the glasses in order to see the crescent shape forming. For about an hour, as the Moon continues to cover the Sun, the crescent will continue to get smaller and smaller until it disappears and the Sun is completely covered by the Moon (this is called second contact).
At second contact, it is safe to remove the sunglasses as totality has been reached. At this point, when the corona is visible to the naked eye, the structure of the corona, white rays and streamers radiating around the lunar disk can be seen. The intensity of the corona is much like that of a full Moon. Once the Moon begins to uncover the Sun (this is called third contact) and continues to move across the sky, the eclipse can be viewed in reverse order. Once again, eclipse sunglasses must be worn.