No two Christmas cards are alike

December 25, 2008 at 1:07 am | Posted in Chatting, Wheater | 1 Comment
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After a very unpolite break, I am happy to announce that “Melting the ice” is back. And I’m not goinna start posting without wishing you all a Merry Christmas and a Happy New Year!

I chose this image as a Christmas card because, despite is not stylish, since I was a child I found it quite amazing how snowflakes can really look like that. I mean, this is the coolest design ever, isn’t it? And a but of scientific chatting before going to complete the daily knowledgement dose:

Ice crystals formed in the appropriate conditions can often be thin and flat. These planar crystals may be simple hexagons, or if the supersaturation is high enough, develop branches and dendritic (fern-like) features and have six approximately identical arms, as per the iconic ‘snowflake’ popularised by Wilson Bentley. The 6-fold symmetry arises from the hexagonal crystal structure of ordinary ice, the branch formation is produced by unstable growth, with deposition occurring preferentially near the tips of branches.

The shape of the snowflake is determined broadly by the temperature, and humidity at which it forms. Rarely, at a temperature of around −2 °C (28 °F), snowflakes can form in threefold symmetry — triangular snowflakes. The most common snow particles are visibly irregular, although near-perfect snowflakes may be more common in pictures because they are more visually appealing.

Planar crystals (thin and flat) grow in air between 0 °C (32 °F) and −3 °C (27 °F). Between −3 °C (27 °F) and −8 °C (18 °F), the crystals will form needles or hollow columns or prisms (long thin pencil-like shapes). From −8 °C (18 °F) to −22 °C (−8 °F) the habit goes back to plate like, often with branched or dendritic features. Note that the maximum difference in vapour pressure between liquid and ice is at approx. −15 °C (5 °F) where crystals grow most rapidly at the expense of the liquid droplets. At temperatures below −22 °C (−8 °F), the crystal habit again becomes column-like again, although many more complex habits also form such as side-planes, bullet-rosettes and also planar types depending on the conditions and ice nuclei.

Interestingly, if a crystal has started forming in a column growth regime, say at around −5 °C (23 °F), and then falls into the warmer plate-like regime, plate or dendritic crystals sprout at the end of the column producing so called ‘capped columns’.

There is a widely held belief that no two snowflakes are alike. Strictly speaking, it is extremely unlikely for any two macroscopic objects in the universe to contain an identical molecular structure; but there are, nonetheless, no known scientific laws that prevent it. In a more pragmatic sense, it’s more likely—albeit not much more—that two snowflakes are virtually identical if their environments were similar enough, either because they grew very near one another, or simply by chance.

See you soon, and thanks for waiting.

Riding an Utapanashku

August 14, 2008 at 10:34 pm | Posted in Alaska, Traditions | Leave a comment
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Have you ever wanted to ride an Innu toboggan through the snow? If this was your childhood dream, you can now make it come true thanks to François Bellefleur of Uanamen-shipu, who offered the description for the diary of Peter Armitage (Fall 1982):

Construction of an Utapanashku

utapan – a toboggan; automobile
utapaniapi – rope used to haul the toboggan
utapanashku – a toboggan; snowmobile; he/she loads his toboggan
utapanikueu – he/she makes a toboggan; he loads someone’s toboggan
utapatshimaushu – he/she pulls a child on a toboggan.
utapatshimeu – he/she pulls, tows someone
utapeu – he/she pulls, tows someone
utapeun – a tobaggon load
(Lynn Drapeu. 1991. Dictionnaire Montagnais-Français. Montréal: Presses de l’Université du Québec. p.879).

Tools used to make the toboggan included a hacksaw, pocket knife, crooked knife (mukutan), extremely sharp axe, small hand plane, pot for hot water, “brush” (split stick with old rag in end), holding wedge tool, a flat carpenter’s pencil, screw-driver-push drill, and a “needle” made out of twisted snare wire.

Some pictures

Looks like quite a hard job, but summer can be so boring for snow addicts!

Sundog Light Phenomenon in Manitoba

July 21, 2008 at 6:22 pm | Posted in Photography, Wheater | 1 Comment
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I just received this at my inbox from National Geographic:

Photo shot on assignment for, but not published in, “Refuge in White: Winter in a Canadian National Park,” December 2005, National Geographic magazine

A solar phenomenon known as a sundog arcs over the tundra in Churchill, Manitoba, Canada. Sundogs are fairly common occurrences in the Arctic and Antarctic. They form when the sun is near the horizon and ice crystals high in the sky line up in a way that bends the solar rays like a prism.

This is amazing, isn’t it? So I continued searching:

A sun dog or sundog (scientific name parhelion, plural parhelia, for “beside the sun”) is a common bright circular spot on a solar halo. It is an atmospheric optical phenomenon primarily associated with the reflection or refraction of sunlight by small ice crystals making up cirrus or cirrostratus clouds. Often, two sun dogs can be seen (one on each side of the sun) simultaneously.

Sundogs typically, but not exclusively, appear when the sun is low, e.g. at sunrise and sunset, and the atmosphere is filled with ice crystal forming cirrus clouds, but diamond dust and ice fog can also produce them. They are often bright white patches of light looking much like the sun or a comet, and occasionally are confused with those phenomena. Sometimes they exhibit a spectrum of colours, ranging from red closest to the sun to a pale bluish tail stretching away from the sun. White sundogs are caused by light reflected off of atmospheric ice crystals, while colored sundogs are caused by light refracted through them. White sundogs are also thought to be caused by the light from the sun reflecting off of water on the ground and focusing the reflected light on the clouds above.

More info on the Wikipedia.

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