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Green flashes and green rays are optical phenomena that sometimes occur right after sunset or right before sunrise. When the conditions are right, a green spot is visible above the upper rim of the disk of the sun. The green appearance usually lasts for no more than a second or two. Rarely, the green flash can resemble a green ray shooting up from the sunset (or sunrise) point. Green flashes occur because the atmosphere can cause the light from the sun to separate out into different colors. Green flashes are a group of phenomena which stem from slightly different causes, and therefore some types of green flashes are more common than others.〔 While observing at the Vatican Observatory in 1960 D.K.J. O'Connell produced the first color photographs of a green flash at sunset. ==Observing== Green flashes may be observed from any altitude. They usually are seen at an unobstructed horizon, such as over the ocean, but are possible over cloud tops and mountain tops as well. They may occur at any latitude, although at the equator the flash rarely lasts longer than a second.〔 A green flash also may be observed in association with the Moon and bright planets at the horizon, including Venus and Jupiter.〔 With an unrestricted view of the horizon, green flashes are regularly seen by airline pilots, particularly when flying westwards as the sunset is slowed.〔 If the atmosphere is layered the green flash may appear as a series of flashes.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Green flash」の詳細全文を読む スポンサード リンク
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