Fact or fiction? Bob claims to have seen it twice. I think I
saw it once but when you stare at the setting sun it’s hard to tell if it’s
really a flash or just your retinas reacting from the light. I looked it up
once and posted about it but there came an interesting article in our ship’s
daily newspaper that I couldn’t help but share with you.
It has to do with the spectrum of colors around the sun. As
the rays hit our atmosphere they are slowed, bent and refracted. The lower the
sun the greater the thickness of air light must pass through before reaching
the eye of the observer. The dispersion of light is greatest at sunrise and
sunset.
As the sun disappears, the colors of the spectrum disappear
one by one. The red rays are the first to go. (Red is also the first color you
lose as you dive deeper in the ocean.) The red rays sink, the orange and yellow
are absorbed and the blue and violet are scattered away. The color least
affected is green and that is what we see for an instant just as the sun
disappears.
Now what we found really interesting is that the slower the
sun sets, the longer the green flash lasts. As you move closer to the poles,
the sun takes longer to set and at some times of the year barely sets before
rising again. In Norway midsummer’s green flash can last as long as fourteen
minutes, seven as it sets and seven as it rises again immediately (the midnight
sun).
The best spot to see the green flash is where there is a
sharp horizon and the sky is free of haze. So a desert, or on mountains or over
water would be best. Hey! Wish us luck. We’d like to see it again at least once
while we’re here on the sea.
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