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Question:
Why are we only warned not to look at the Sun during an eclipse, because of the damage it could cause your retina? What is the difference from any ordinary day? Why was the eclipse or May 10, 1995 not as dark as usual?



Replies:
It is almost impossible to stare at the uneclipsed Sun long enough to do damage to the retina; our reflexes make us shut our eyes and turn away. So there is no real need for a warning about doing this. With the recent annular eclipse, though: at places where there was only a ring of Sun around the Moon, that ring may not have been bright enough to make a person look away before damage occurred (perhaps a ring-shaped burn on the reti- nas). That was the reason for all the warnings. In a true total solar eclipse, ALL of the Sun is blocked by the Moon, and at totality it IS safe to look directly at it. (By the way, there will not be a total solar eclipse visible in the United States until the year 2017.)

The May 10, 1994 solar eclipse was what is called an annular eclipse (the Latin word "annulus" means "ring"). The Moon has an elliptical orbit, so sometimes it is closer to the Earth, sometimes farther away. For this eclipse, it was in the "farther away" part of its orbit, so the Moon's disk was not able to completely block the Sun. Even at places where the eclipse had maximum coverage (producing the "ring of Sun" around the Moon's disk), that ring was enough to keep the sky fairly bright.

RC Winther


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