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The Green FlashMany people have heard of the "green flash" but few have seen it. Lots of others have never heard of it. More than a few don't believe us when we tell them about it. The green flash is a real phenomenon that is caused by atmospheric refraction of the sun's light just as it disappears below the horizon. The Nautical Almanac explains what causes it. For some reason, the green flash is rarely seen outside of the tropics. It occasionally happens when the sun rises as well, but you have to be looking at the right spot or you'll miss it. We've seen it many times. I also once saw Venus turn green one evening as it set, about 15 minutes after we'd had a magnificent display of the green flash of the sunset. The green flash is most likely to occur on nice days when the horizon is clear. You can watch it for a longer period if you squat down and then stand up, or climb the rig, as the sun turns green. This is because your horizon distance is further away the higher you are. We've done this often, and it really works! We were lucky enough to capture the green flash on video one evening. This was taken through a dark neutral gray filter, and you can clearly see the sun as the upper limb turns green!
January, 2006: Abemama, Kiribati. This somewhat blurry, but unretouched, image shows the upper limb of the sun turning green just before it disappears below the horizon. |
