A Green Flash Over Italy
影像提供與版權: Danilo Pivato (Beyond the Moon)
Explanation:
How could the Sun turn green? Difficult to observe, the momentary green flash above the rising or setting sun has been documented as a phenomenon caused by the atmospheric bending or refraction of sunlight. Like a weak prism, the Earth's atmosphere breaks white sunlight into colors, bending red colors slightly and green and blue colors through increasingly larger angles. When the sky is clear, a green flash just above the sun's edge can sometimes be seen for a second or so, when the sun is close to a distant horizon. Still, from a site atop Mt. Autore (altitude 1,850 meters) in Italy astrophotographer Danilo Pivato captured this dramatic green flash movie. The time between frames varies from over one minute in the beginning to about one second as the flash becomes visible.
說明:
太陽怎麼會變成綠色的？ 這種綠色閃光的現象非常短暫，不易觀測。現在人們已經了解，這是只有在日出或日落時，由於地球大氣使得陽光產生偏折的現象。地球大氣就像一個三菱鏡一樣，將太陽的白光展開成各種顏色的光譜。紅光的部份較不易偏折，而綠光和藍光偏折的角度比較大。當太陽接近地平線時，如果天氣晴朗，有幾秒鐘的時間可以觀測到太陽的上緣有綠色閃光。這次，義大利的天體攝影家 Danilo Pivato，在義大利 Mt. Autore 的山頂上 (海拔約1,850公尺) 拍攝到了這戲劇性的綠色閃光影片。在影片剛開始時，每幅影格的間隔是一分鐘，到綠色閃光發生時，影格間距則是一秒鐘。
資料來源: Scientific American
Department of Physics, NCKU
