 Green flash after sunset, July 1996, Che-Cheemaun ferry, Lake Huron, Ontario Immediately after sunset, the atmosphere continues to refract the sun’s rays from below the horizon. If the sky is clear and the horizon is flat, you may catch a glimpse of a green flash. Under perfect conditions, the weak prismatic effect of the atmosphere can cause this rare phenomenon.
Since refraction is stronger for the blue and green rays of the sun, they are lifted over the red and yellow rays, filling the entire sky with an eerie green glow. The same flash can happen in the eastern sky just before sunrise. A watery horizon -- from a ship (as in this photo) or from shore -- is the most common place to see a green flash. I caught this one while crossing north to south on the Che-Cheemaun ferry, Lake Huron, Ontario, to Tobermory. |
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