It’s a phenomenone that happens every single day on Earth, yet it’s one that very few people have every witnessed. In fact, it’s happening somewhere on Earth right now as the last sliver of the Sun dips below the horizon and day slowly fades into night. What is it? It’s the green flash, of course.
Wikimedia Commons No, it’s not a comic book character, but a natural phenomenon that occurs just as the Sun sets for the evening. They’re most often reported by people who live near an ocean, and, though the sea is the best place to witness this flash of green light, it can also be seen on land with the naked eye, when the conditions are right, and when you’re looking toward a very clear and distant horizon. Here’s more from EarthSky.org: Most people see green flashes just at sunset, at the last moment before the sun disappears below the horizon. Be careful and don’t look too soon. If you do look too soon, the light of the sunset will dazzle (or damage) your eyes, and you’ll miss your green flash chance that day.
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Wikimedia Commons But if you wait – looking away until just the thinnest rim of the sun appears above the horizon – that day’s green flash could be yours. Of course, the green flash can be seen before sunrise, too, although it’s harder at that time of day to know precisely when to look. There are many different types of green flash. Some describe a streak or ray of the color green … like a green flame shooting up from the sunrise or sunset horizon. The most common green flash, though – the one most people describe – is a flash of the color green seen when the sun is nearly entirely below the horizon.
Wikimedia Commons So, what causes us to see the green flash in the first place? Again from EarthSky.org: The green flash is the result of looking at the sun through a greater and greater thickness of atmosphere as you look lower and lower in the sky. Water vapor in the atmosphere absorbs the yellow and orange colors in white sunlight, and air molecules scatter the violet light. That leaves the red and blue-green light to travel directly toward you. Near the horizon, the sun’s light is highly bent or refracted.
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Wikimedia Commons It’s as though there are two suns – a red one and a blue-green one – partially covering each other. The red one is always closest to the horizon, so when it sets or before it rises, you see only the blue-green disk – the green flash. Here’s a rare video of the green flash, so you can see what it looks like:
Have you seen a green flash? Do you have pictures? Leave us a comment and let us know?