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No. 108: Nov-Dec 1996

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A Blue Flash

Green flashes occasionally appear when the sun (or moon or Venus or Jupiter) sink below the horizon. Blue flashes are much rarer but still well-recognized phenomena. An example of the latter was observed in 1995 on the Indian Ocean.

August 11, 1995, Bay of Bengal. Aboard the m.v. Repulse Bay enroute Jeddah to Port Klang.

"Prior to sunset the vessel was proceeding due east across the Bay of Bengal and it was quite apparent that the sun was still very bright and had not taken on its usual darkorange or red appearance; even with half its diameter above the horizon, the sun was much too bright to view directly. As the last segment of the sun dipped below the horizon, a blue 'horn' formed at each end of it, as shown in sketch (a), and these then closed up to form a bright-blue arc, as shown in sketch (b)."

(Leslie, A.J.; "Blue Flash," Marine Observer, 66:115, 1996)

Comment. The blue flash is a shorter-wavelength version of the green flash. The basic phenomenon is explained in terms of dispersion of the sun's spectrum by the atmosphere near the horizon. Even so, many enigmas remain about these low-sun phenomena. There have been observed: multiple flashes, flashes preceding sunset, complex flash structures, and the apparent psychological origin of some flashes. For details, see GEL1 in Rare Halos, Mirages. This book is described here.

Bright-blue arc in the sky

From Science Frontiers #108, NOV-DEC 1996. 1996-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:

Quotes

  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987