"Uncle Peter" wrote in message
news
On Fri, 31 Oct 2014 13:02:43 -0000, Dave Liquorice
wrote:

On Fri, 31 Oct 2014 11:55:23 -0000, Uncle Peter wrote:

"This is a fact. -20C air does not make you cold, .
You might shiver if you were naked, but the
shivering will stop you getting any colder".

To me, it sounds like he's talking absolute bull****
and he should be sent to the funny farm, but is
there an element of truth in what he said?....

Nope. Its certainly possible to be quite active when
naked in -20C air and do fine, but just standing there
naked and shivering wont let you survive for long.

Quite shivering (proper shivering not what most people think of as
shivering) is the bodies attempt at trying to maintain your core
temperature. It might be able to depending on the rate of heat loss
but naked in, even still, -20 C air you won't be able to generate
enough heat and your core temp will drop, you'll stop shivering, you
may even feel quite warm (so much so that people falling into
hypothermia may take their clothes off), then you drift off to
sleep...

You'd have to be an utter wimp with a dose of the flu, or 95 years old to
not be able to create enough heat for that, especially as you've reduced
blood flow to the surface of your skin (on your entire body), and your
brown fat cells are creating heat aswell.

Must be why no one ever dies of hypothermia.

Active or not it doesn't matter. Shivering replaces active, it's the
same thing, your muscles are moving. You also have reduced blood flow
to the surface (all of you, not just your fingers and toes and other
sticky out things), and brown fat cells which generate heat directly
from calories.

Yup, which leads to frostbite on your extremities.

Your body won't allow that if you have a reasonably fit body. I've gone
hillwalking barefoot in the snow. My feet go cold and numb at first,
then eventually they go red and warm up again.

Keep barefoot in that snow for a few hours and see what happens. What
temperature was that snow at? Fresh dry powder snow can be very cold,
think in the terms of -40 C ...

It was all day,

Bull****.

and on a few occasions it was snowing and quite windy. And I wasn't
wearing a shirt either. You don't get -40C snow in the UK. In fact wet
slushy snow is colder,

Bull****.

as the water contacts your whole foot and stays there. Frozen snow
conducts less heat away.

But its still perfectly possible to get frostbite if
you are stupid enough to try sleeping with your
bare feet in a snow drift.