GREENVILLE, N.C. (WNCT) – The next time you head to the beach to catch a sunrise or sunset, try also spotting the elusive green flash.What is it?

It’s an optical phenomenon that happens when the sun is almost entirely below the horizon, with the smallest sliver of the top edge of the sun still visible. For a second or two, the top edge of the sun will appear green in color. Because it is so brief, it is known as the green flash. It’s said that once you’ve seen a green flash, you’ll never again go wrong in matters of the heart.

Green flash on setting sun observed from a mountain. Image via Amiteshomar / Wikimedia Commons

How can you see it?

Don’t look at the sun until it is almost entirely below the horizon. If you look too soon, you could ruin your chances of seeing the green flash for the day by dazzling your eyes. Here’s what else you need:

  • A clear day with no haze or clouds on the horizon.
  • A distant horizon and a distinct edge to the horizon. You can see the green flash from a mountaintop or high building. But it’s most often seen over the ocean, by people on beaches or in boats.

What causes it?

The green flash happens because at sunrise or sunset, you are looking at the sun through a greater and greater thickness of atmosphere (the atmosphere is thicker lower in the sky than it is higher up). Water vapor in the atmosphere absorbs the yellow and orange colors of white light and air molecules scatter violet light away. That leaves red and blue-green to travel to you. Near the horizon, the sun’s light is highly bent or refracted. 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.Bonus

The green flash can be a like a flame that shoots above the horizon. This is known as a green ray.

– Meteorologist Pierce Legeion

Pierce Legeion is a meteorologist and digital journalist for WNCT 9 First Alert Weather.