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A false sunset can refer to one of two related atmospheric optical phenomena, where either 1) the sun appears to be setting below the horizon, while in reality it is still some distance above it, or 2) the sun has already set, but still appears to be on or above the horizon (thus representing the reverse of a false sunrise). Depending on circumstances, these phenomena can give the impression of an actual sunset. There are several atmospheric conditions which may cause the effect, most commonly a type of halo, caused by the reflection and refraction of sunlight by small ice crystals in the atmosphere, often in the form of cirrus or cirrostratus clouds. Depending on which variety of "false sunset" is meant, the halo has to appear either above the sun (which itself is hidden below the horizon) or below it (in which case the real sun is obstructed from view, e.g. by clouds or other objects), making the upper and lower tangent arc, upper and lower sun pillars and the subsun the most likely candidates. Similarly to a false sunrise, other atmospheric circumstances may be responsible for the effect as well, such as simple reflection of the sunlight off the bottom of the clouds, or a type of mirage like the Novaya Zemlya effect. ==See also== *False sunrise *Sun pillar *Halo (optical phenomenon) *Upper tangent arc *Lower tangent arc *Subsun *Mirage *Novaya Zemlya Effect 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「False sunset」の詳細全文を読む スポンサード リンク
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