緬因州上空的日柱

A Sun Pillar Over Maine



影像提供及版權： Lucy Orloski

Explanation:
      Have you ever seen a sun pillar? When the air is cold and the Sun is rising or setting, falling ice crystals can reflect sunlight and create an unusual column of light. Ice sometimes forms flat, six-sided shaped crystals as it falls from high-level clouds. Air resistance causes these crystals to lie nearly flat much of the time as they flutter to the ground. Sunlight reflects off crystals that are properly aligned, creating the sun-pillar effect. In the above picture taken late last month, a sun-pillar reflects light from a Sun setting over Bangor, Maine, USA.  

說明:
      你曾經看過日柱嗎？ 當天氣很冷而太陽正好升起或落下，落下的冰晶會反射陽光並產生一道罕見的光柱。當冰從高層的雲落下時，有時會形成平板，形狀像是停止號誌的冰晶。空氣阻力使得這些冰晶在落到地面時幾乎以水平的方式落下。被冰晶反射的陽光因此幾乎完全被準直了，並產生日柱的效應。上圖的拍攝時間是上個月，一道反射夕陽的日柱在美國 緬因州的 Bangor上空。  

資料來源: Scientific American
               Department of Physics, NCKU