Dear Tom,
I've read about the "green flash" being seen in southern Florida. Fact or fiction?
Helen Baker, Naperville, Ill.
Dear Helen,
The "green flash" is real. It is a momentary flash of green light emanating from the
upper rim of the rising or setting sun at the moment it crosses the horizon.
Widely thought to be visible only in the tropics, the green flash can be seen anywhere in
the world, and most easily from a vantage point with an unimpeded view of the horizon,
such as over a large lake or ocean.
Sunlight passing through the atmosphere is bent upward, and the bending is greatest
when the sun is on the horizon. The shortest wavelengths of light (blue and green) are
bent the most, so they are the first colors seen on the rising sun and the last as it sets.
Blue wavelengths are removed by atmospheric scattering, leaving the green
wavelengths visible for the flash.
