Solar Phenomenon – The Green Flash
THE GREEN FLASH –
Where will it be spotted next?
By: Slade Ogletree
Before you think I’ve spent too much time with old comic books, drank homemade tequila, or chewed on the wrong cacti, let me assure you that none of these are responsible for “The Green Flash”. The Green flash is a real illusion, optical illusion, that is. Before I dig myself too deep of a hole, let me explain. The Green Flash is an optical illusion that makes the sun appear to change to a greenish color at the very instant it disappears (or appears) over the horizon. Contrary to many misconceptions, it may occur at both sunrise and sunset, at virtually any latitude, and at any time of the year.
Legends and myths about the flash have popped up through the ages, but the green flash didn’t gain public attention until 1882, when it appeared as an important topic in the Jules Verne novel Le Rayon Vert — “The Green Ray.” One of Verne’s characters also recalls a Scottish legend that claims that whoever has seen the green flash will never again err in matters of the heart.
Well, sorry Mr. Verne, but that’s bunk! This is the stuff of 19th-Century romantic French novels, not Scottish folklore. Anyone who spends fifteen minutes on a search will find not only that no such legend exists; but that the Scots, along with the rest of the Celtic people, regard green as a color associated with evil spirits, death, and misfortune. Oops!
According to some scientists of the late 19th and early 20th centuries, the green flash did not arise in Earth’s atmosphere at all, but only in the viewer’s eyes. The green flash, they claimed, was the complementary-color afterimage created by staring too long at the bright setting Sun. You can produce this effect yourself by staring at a red object; say a ripe tomato, in a brightly lit room. After about 15 seconds, switch your gaze to a white surface and you’ll see a ghostly bluish green “anti-tomato.” This theory went out of the window when the flash was successfully photographed.
So, exactly what is it? It’s a phenomenon, meaning we can’t explain it fully, but here’s what we do know. When light enters Earth’s atmosphere it is refracted, or bent, in the direction of the denser air — in other words, downward. The amazing result of such refraction makes the image of any celestial object we see appear slightly higher than the true position it would occupy if Earth had no air. The effect is greatest at the horizon, where light takes the longest pathway possible through the atmosphere.
Now, let me introduce “Roy G. Biv”. These are the colors of the visible spectrum…Red, orange, yellow, green, blue, indigo, and violet. This is evident in a rainbow or when a glass prism is used to spread sunlight into its component colors. Sunlight is composed of a range of wavelengths (colors), each of which is refracted by a different amount. The shorter, (or bluer) the wavelength, the more it’s refracted by the atmosphere.
So why isn’t it a blue flash? To make a long story short, the blue light in the sun’s light has already been refracted by the upper atmosphere, making the sky appear blue. This leaves us the reds and the greens…and the sun is glowing bright red at sunset so just as the last of THAT light disappears behind the horizon, for an instant all we can see is the green, hence The Green Flash.
You’re most likely to see the green flash on a calm and clear evening. As the sun gets closer to the horizon, it distorts, and soon its edge becomes “notched” on both sides. The notches seem to be riding up the sides of the sun. (It’s actually the sun that’s moving down while they stay still) When the notches get to the top of the sun, they meet and pinch off the edge of the disk so that it looks like a floating cloud—this is the part that suddenly turns green.
So, now you know the truth about The Green Flash. In my travels in Baja, I have witnessed more than my fair share of spectacular sunsets, and only a handful of Green Flashes. There’s no guarantee that you’ll see it from any place on any day. It’s more of a “needle in the haystack” kind of search, but sitting on a beach watching the sunset is a really good place to start.