[MIham] Two Suns

[FSK]

TWO SUNS: Weekend sailor Chris Ware was anchored in Banks Channel at
Wrightsville Beach, NC, when he witnessed a very strange sight: two suns
setting. "What planet are we on?" wondered an onlooker in a neighboring
boat.

Answer: Earth, where ice crystals in clouds can create the appearance of a
second sun.

"The 'extra sun' Ware witnessed is an unusually bright sundog," explains
atmospheric optics expert Les Cowley. To produce such a intense display,
"the ice crystals must be larger than a tenth of a millimeter with nearly
optically perfect faces and free of air bubbles and flaws. And they must not
wobble too much! When we think of the time and effort needed to polish a
perfect gemstone, it is a wonder that nature makes millions of icy examples
in the sky to provide fine halo displays."

Sometimes ice crystals conspire to produce even stranger sights: "Very early
halo observers described their displays as three, four and sometimes even
'seven suns.'" notes Cowley. "Matthew Paris' display of 1233 had five."


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