Geographic Phenomenon: Sun Dogs

Sun Dogs, known scientifically as parahelia, are optical phenomena characterized by bright spots directly to the right and to the left of the sun.  Although the name is supposedly a mistranslation of an Inuit term referring to “the sun’s dogs,” sun dogs can be seen anywhere in the world, at any time of the year, though are most often visible when the sun is at or near the horizon.  This has to do with the underlying cause of sun dogs: hexagonal ice crystals in cirrus clouds and ground-level “Diamond Dust” which forms at exceptionally low temperatures.  As these ice crystals drift downwards they do so parallel to the ground, creating the perfect prism through which to refract a sun at or near the horizon.

Due to the specific optical properties of ice crystals, sun dogs are always located 22° away from the sun, and may be accompanied by a 22° halo, which occurs when enough ice crystals “wobble” from their parallel-to-the-ground orientation.

Sun dogs have a long history in art, literature, and religion — as both a source of trepidation and inspiration — with references dating back to Aristotle, Cicero, and Seneca before the common era.  Shakespeare mentioned them in Henry VI.  Someone in 1535 Sweden dramatically depicted them very dramatically.  And they’re still a source of conspiracy theories in modern times.

Friday News and Links

Islands on Islands on Islands

Here is something fun and inconsequential to think about over the Thanksgiving break:  islands on islands on islands, or, as they’re known, “triple islands.”

sweater within a sweater

Triple islands are a relatively recent geographic phenomenon du jour, likely aided in popularity (at least on some level) by the successful, though somewhat-laughable and oft-meme’d, blockbuster film, Inception.  There are at least three recognized triple islands on the planet: one in the Philippines known as Vulcan Point, and two in Canada — one on Victoria Island, part of the Canadian Arctic Archipelago, and one on Glover Island in Newfoundland.  Vulcan Point in the Philippines can be read about in more detail here, which includes a nice zoom-in slideshow of the island.  Below I’ve compiled zoom-in Google Map images of the two in Canada, for which information is a little more scarce.

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Aurora Borealis Visits Chicago

If you live in the Chicagoland area (as we do), you’ve probably heard about the northern lights show that graced our part of the country last Monday night.  According to astronomers it was the first significant event of Aurora Borealis to appear in Chicago in the last seven years.  The phenomenon occurs when high energy protons and electrons released by the sun (solar wind) interact with our planet’s magnetic field.  However, if you live in the city (where light pollution restricts visibility) or were inside (where walls and ceilings restrict visibility) between 8 and 9PM last Monday, you most likely missed it.  Fortunately, NASA has released some truly spectacular images and videos of the show.

(click for larger image)

[vimeo w=500&h=331]

(image and video courtesy of NASA)

Another angle: