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Why Snow is Blue Jan 2, 2004 After a fairly mild autumn and beginning of winter, we have finally had some cold days and a few inches of snow. Of course, even in a country where this type of weather happens every year, the snow brought traffic chaos and many cases of electrical supply failure, with snow laden trees finally succumbing to the extra weight and toppling down over power lines. The power supply companies have promised to investigate the possibilities of putting power lines underground, but as they made the same promises last year and the year before, nobody really believes them anymore. But despite the problems with power and simply getting from place to place, the snow covered countryside is beautiful and provides a very rewarding experience for those brave (some would perhaps say foolish) enough to venture outdoors. It was on one of these brave, or foolish if you will, walks with the two dogs, that I suddenly started to wonder why it is that the snow takes on a particular blue coloration in sunlight. Like most people, I suppose, I had sub- consciously noted this before, both in real life and in movies and photographs, but I had never really stopped to think about why it is so. Returning to the warmth of the house, I decided to investigate further and see if there was a scientific explanation for what I had seen. And sure enough, through the wonder of the Internet, I discovered a paper on just this subject. It was written way back in 1986, by Larry Gedney, a seismologist at the Geophysical Institute attached to the University of Alaska. And if anyone should know, Larry certainly should. My initial thoughts were that the snow colour was perhaps a reflection of the blue sky above, but in fact, although the colours in the skies and ice are the result of the same phenomenon – light scattering – the processes are almost the opposite of each other. Apparently blue skies result from light bouncing off molecules and small dust particles in the atmosphere. Because blue light scatters more than red light, the sky appears blue, except in the direction of the sun. When light passes through ice or snow, however, the red light is absorbed while the blue is allowed to pass through. Because of the large size of snow grains and ice crystals, all wavelengths of visible light are scattered equally, so it is mainly the absorption of the red light, which gives the snow and ice the characteristic blue colour. Browsing further through the Internet, I also came across another possibility, this time in an article published in a magazine called “Fate”, from December 1992. This article describes how a Mr. and Mrs. Milton Mayer were driving in California in April 1953, when they watched a most unusual snow fall: the snow flakes were bluish in colour and appeared to be glowing. Knowing that others would find their story hard to believe, they found several other witnesses to verify that blue, phosphorescent snow had fallen. A couple of days later, the Mayers developed an itching rash, accompanied by blisters, on their faces, hands and arms. Could they possibly be the victims of radioactive snow? (This was in the fifties, remember). A check with the Atomic Energy Commission informed them that the nearest atomic cloud was over the distant Atlantic Ocean. The AEC also denied that snow would appear to be luminous if it were radioactive. To date, no scientific explanation for the mysterious blue, glowing snow has been forthcoming. Of the two explanations for blue snow described above, I think I prefer to believe the one provided by Larry Gedney. Certainly I did after I started to get this itchy rash on my arms and hands…. Hälsningar till nästa gång, ------------ About the author: Robin Alan Bell is an Englishman by birth, but migrated to Australia back in '72. Married and divorced there. Spent the last 3 years living by myself on a remote farm in rural New South Wales with no mains electricity, water etc. All power, heating was from natural resources (solar, wind, wood). "Met" a Swedish girl on the internet, came to Sweden for a holiday, loved the place (and the girl), moved to Sweden permanently Christmas 2001 and married the girl in Easter 2002. Living happily ever after... Email Robin Alan Bell: sosoft@ozemail.com.au Comment on this column in the forum. Tell a friend about this site! ------------ |
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