--A Surprise at Sunset.*

   Many people have never heard of, much less seen, the "green flash", a remarkable optical effect sometimes seen at sunset over the ocean.

   When conditions are right, the last bit of the visible sun is seen to turn distinctly green as it disappears behind the horizon.

   The green flash is most often seen when layers of air are very stable over the ocean, which also sometimes shows a thin layer of fog.

   More people report seeing the green flash during winter, but this may be because sunset is earlier in the evening when more people may be outside to see it.

   Never stare at the bright sun!  Look only in the last few seconds when the last bit of the sun is about to disappear below the horizon.  If a bit of the sun seems to separate from the top, a green flash is more likely.

   The effect is caused by the variable bending of the colors of sunlight in the atmosphere.  One might think of the sun as overlapping images of red, orange, yellow, green, blue, indigo and violet.  The blue, indigo and violet are scattered by the atmosphere, and the last image visible is the green one -- The Green Flash.

Photos supplied by Tom Osborne
on July 27, 2005.