On Wednesday, July 22, 2009 there will be a total solar eclipse of the Sun. It is the longest eclipse that any of us may ever witness in this lifetime at 6 minutes and 39 seconds and will not be exceeded again until 2132. Although no part of the eclipse will be visible from the continental United States, China will be provided with the best view. The path of the totality will begin in Eastern India and will end about 2,000 miles south of Hawaii. This is the second in a series of three eclipses in one month. There was a lunar eclipse on July 7, and now the solar eclipse on the 22nd and a lunar eclipse again on August 6.
Whenever a solar eclipse is expected, there is much concern over risk of eye damage while watching the event. Danger to the eye is from heat, UV and excessive blue light. There is no damage to the eye in looking directly at the total solar eclipse, however the risk is greatest just prior to its totality or during its partial phases when the disk is present. The 1 percent of the Sun's surface that is just visible before the eclipse is 10,000 times brighter than the full moon. Staring at the sun under these circumstances can damage the retina. According to Dick Land, of the Schepens Research Institute at Harvard, the danger comes from the fact an eclipse changes the circular, too bright disk, into something interesting. The brightness is the same and still too great, but in eclipse there is a shape, a black part, and the crescent remaining of the sun. Now the normal safety feature of eye motion is defeated by the cognitive event of having a point to fixate. The two sharp cusps are points that the eye may focus upon and now the damaging image on the retina is stopped on the most sensitive neural tissue. This short stoppage begins damage from all mechanisms, too much blue light, too much UV, and too much heat. This damage is not recoverable. To observe the bright phases of the eclipse, a projected image is the safest. There are filter options, but caution should be used advises Mr. Land.
Total solar eclipses can be frightening events for people unaware of their astronomical nature, as the Sun suddenly disappears in the middle of the day and the sky darkens in a matter of minutes. According to Yahoo News Sourced, Indian astrologers are predicting violence and turmoil across the world as a result of this week's total, which the superstitious and religious view as a sign of potential doom.
Whatever your views, a total solar eclipse is a once in a lifetime opportunity to enjoy the beauty and spectacle of nature's wonder.