星空故事：光污染

放大圖片

　外太空生命學先驅卡爾．薩根（1934-1996）曾指出地球具備4項可被外星人探測得的生命特徵，分別是：缺少紅光波的色譜（葉綠素所致）；FM廣播電波；大氣存在分子氫和甲烷（沼氣）。假如當年卡爾．薩根有幸可以看到由人造衛星拍得的地球夜景（見圖），他的論據肯定會更精彩。

　對一般人來說，這幅地球夜景圖片可能是美麗的景象，可對天文學家來說，這卻是夢魘。圖片中亮點越大，代表光污染越嚴重，想信大家不難從光點中辨認出香港等大城市。可惜的是，對於生活在這些嚴重光污染地區的孩子來說，他們的天空只有太陽和月亮。試想想，沒有星空的孩子，又如何有能力為祖國的太空事業作出貢獻？

Light pollution

　Exobiology pioneer Carl Sagan (1934-1996) wrote that our planet had four biogenic signatures that could easily be detected by a spacecraft: the absorption of red light (by chlorophyll), modulated narrowband radio emissions, and the presence of both molecular oxygen and methane in our atmosphere. What Carl Sagan overlooked was light pollution.

　Look at the picture. You probably have no difficulty in identifying some famous cities such as Hong Kong. What seems to be beautiful night scenery is nightmare for astronomers. They are the brightest dots and therefore, the most severely light polluted. 　■甄枝強　香港天文學會