Why Wool is Warm and Snowflakes Aren't Always Pretty

By Veronique Greenwood | December 27, 2011 12:16 pm


If you live in the Northeast, chances are you’ve had a disappointingly balmy December so far (the snow seems to have taken a wrong turn somewhere and wound up over Texas instead). But when the air gets that snap and you  reach for the wool socks, Emily Eggleston at Scientific American has a few factoids that promise to fascinate. Here’s why wool keeps you warm:

Wool keeps out the cold because it is an excellent insulator. Crimped and crisscrossed woolen fibers create tons of little air pockets. The tiny air masses within my socks have difficulty moving in and out of the fabric. Without convective heat transfer and contact with air of other temperatures, the spaces between wool fibers maintains a steady temperature.

And why are snowflakes sometimes beautifully crystalline and sometimes clumpy as cold oatmeal?

The two main snowflake shapes are plates and columns. Plates are the typical hexagonal flakes and columns are elongated, blocky crystals. As a cloud’s temperature moves below 32º F(0º C), it will pass through various phases of crystalline potential. If enough water is present in a cloud, between 32 and 23º F (0 and -5º C), plates will form, sending small six-armed flakes to the earth. In the 23 to 14º F (-5 to -10º C) range, a cloud produces columnar snow crystals.

My own lingering question is, why does cold air have that particular smell? Is it something to do with how molecules change as they get colder? I’m off to scour the internet for an answer…

Image courtesy of Gui Seiz / flickr

CATEGORIZED UNDER: Environment, Living World
  • John Moore

    I thought I read on this website that they discovered that snow flakes and rain drops get seeded by microbes. Wouldn’t stop the columns or crystals though…

  • Bobby LaVesh

    Microbes don’t make rain- China does.

  • Georg

    “”crisscrossed woolen fibers create tons of little air pockets.””

    Btw a liter of air is about one gram.

  • Sandra

    “tons” is a VERY WELL KNOWN figure of speech, George.

    And learn how to spell your own name, you immature twit.

  • Tomek

    Regardless, that looks to be a quote from scientific america. Or, from a researcher quoted in scientific america. In the case of the former, thats semi-bad (I would try to avoid it..), in the case of the latter, that’s completely natural in casual speech.

  • John Lerch

    re the smell of cold air. I presume he means the smell we used to call Canadian air. I have guessed that it is ozonated air due to the friction of ice crystals against each other.

  • http://discovermagazine.com Iain

    Living in the great white north, I’ve often smelled that clean crisp air that tells you (via the nose) that snow is on the way. I’ve always thought that was the smell of clean air, since it comes from the even greater, whiter than white North (Arctic). Not even contaminated (much) by organics from the biosphere.

  • Scott

    I thought cold air had a smell because cold fronts came from the north, in my case, the mountains, but that could be wrong. Perhaps it smells crisper because it is drier. And it is the reaction of the nose to the dry air that gives cold air a feeling as well as a smell.

  • TRJc

    Good explaination of why dry wool socks keep your feet warm. What fabric, as socks, does the best keeping feet warm when the socks are wet, and why?

  • kik

    can any one explain ..which gas causes that foul smell (4rm socks)?????????

  • Carolyn

    Cold air does have a smell to it, although some people don’t seem to get it when I say it smells cold. 😛

  • Geack

    @9. TRJc – Ask any spring rafting guide, and they’ll tell you for wet insulation, you want wool. The explanation I’ve heard is that the fibers don’t absorb water and mat together the way cotton or many synthetics do, plus they’re more resilient. So they stay puffier when wet than other fibers, preserving the airspaces mentioned in the article and maintaining the insulating air layer better. There may be some synthetics that mimic this.


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