Shadow bands

Shadow bands are thin wavy lines of alternating light and dark that can be seen moving and undulating in parallel on plain-coloured surfaces immediately before and after a total solar eclipse.^[1] They are caused by the thin slot-like solar crescent illuminating the Earth's atmosphere moments before and after the eclipse totality,^[2] Their movement is caused by atmospheric winds.^[3]

In 2008, Dr. Stuart Eves suggested that shadow bands might be caused by infrasound, which involves the shadow of the moon travelling at supersonic speed, which in turn produces low frequency sound that humans can't hear. Due to this, he theorized, the movement of the moon creates a shock-wave in front of the shadow, which causes shadow bands. Dr. Eves said "If proven, it would be a something of a revelation that eclipses are a sonic as well as an optical phenomenon." Professor Brian Jones stated "The [accepted] theory works, there's no need to seek an alternative".^[4]

Shadow bands have been noted throughout history:

In the 9th century AD shadow bands during a total solar eclipse are described for the first time-in the Völuspá, part of the old Icelandic poetic edda.
In 1820, Carl Wolfgang Benjamin Goldschmidt of Germany calls attention to the shadow bands visible just before and after totality at some eclipses.^[5]
In 1842, George B. Airy, the English astronomer royal, saw his first total eclipse of the sun. He recalled shadow bands as one of the highlights: "As the totality approached, a strange fluctuation of light was seen upon the walls and the ground, so striking that in some places children ran after it and tried to catch it with their hands"^[6]

References

^ Effects During a Total Solar Eclipse
^ Jones, Barrie. "Explanation from Barrie Jones, Open University". http://www.williams.edu/Astronomy/IAU_eclipses/explanation.html. Retrieved 2010-07-24.
^ Strickling, Wolfgang (2007-01-26). "Wolfgang Strickling's eclipse observations 2001 page". http://www.strickling.net/2k1_engl.htm#shadowbands. Retrieved 24 July 2010. "The best theory for the emergence of the shadow bands is published by Codona 1986 [3]. His theory meanwhile accepted by the most scientists. ... movement of the shadow bands is caused by winds in the different atmospheric levels."
^ "Sound 'cause of shadow spectacle'". BBC News. May 21, 2008. http://news.bbc.co.uk/1/hi/sci/tech/7347180.stm. Retrieved 2009-11-14.
^ Chronology of Discoveries about the Sun
^ M.Littmann, K.Willcox, F.Espenak: Totality: eclipses of the sun 2nd edition. Oxford university press. page 119

External links

Shadow bands during a total solar eclipse, by Dr. Wolfgang Strickling