[Illuyankas]

Hmm... tshirts in ricockulously cold weather, you say... Do you think you Canadians have space in Canadia for all our Geordies?

[Mentalist]

we have much empty land up North

[Illuyankas]

And you have coal! It's a match made in a cold, frozen hell heaven!

[Darkwatch]

With their funny accent?

[Kallyfudge]

I would like to see and explanation of why it isn't because of evaporation, mainly because part of the freezing is because of evaporation.

Also Celcius and Farenheit (spelling probably wrong but i don't care you know what i mean anyway so who gives a $h!T?) meet at - 40 celcius or farenheit. There is an absolute scale, Kelvin (K). This is an absolute temperature scale where there are no negative values of temperature. Temperature is based on the energy of the atoms or molecules in the medium you are considering, so there is an absolute 0, the temperature you cannot go below (where these atoms have 0 energy and I mean 0.00000000 forever) you cant have negative energy. This temperature is 0 degrees Kelvin or -273 celcius (I never learnt farenheit). Celcius was developed as the difference between the freezing and boiling points of water, by saying there are 100 different units of temperature between these points. Kelvin uses the same logic but starts at absolute 0. Interestingly the boiling point of water changes depending on atmospheric pressure (so on Earth with height) but the freezing point is set at 0 (although not quite true look for triple point of water on wikipedia if this is of any interest, if you want to look at realy cool stuff on wikipedia look for lake vostock (This is realy f'ing awesome and can turn a conversation about temperature into a conversation about alien life)). Other i think interesting bits: We cannot ever reach absolute 0 because of the uncertainty principle ( im drunk now but this has awesome implications). There is a background temperature of the universe (look for cosmic microwave background radiation or CMBR), this has been one of the main avenues of research into the shape and evolution of the universe we inhabit (and incidentally was first mistaken as bird poo by the people who found it and got a noble prize in physics).

I wish i could communicate this stuff better, but I wanted to show how a simple and obvious scale such as temperature is not as obvious as it would first appear. By questioning the basic bits, you get a lot of unexpected answers which are awesome! The best stuff in science is the bits we don't know.

This post has been edited by Kallyfudge: 27 January 2011 - 01:20 AM

[Beezulbubba]

So in other words "Can't-i-da" is North United States of Awesome (only in a geographic sense).

[D'rek]

Kallyfudge, on 27 January 2011 - 01:17 AM, said:

I would like to see and explanation of why it isn't because of evaporation, mainly because part of the freezing is because of evaporation.

Evaporation = liquid becoming gas

This liquid is becoming solid, ergo it is not evaporation.


On a related note, if you visit Canada in mid-winter, don't drink a lot of hot water before stepping outside. We've all seen the horrors...

This post has been edited by D'rek: 27 January 2011 - 02:59 AM

[amphibian]

Darkwatch, on 26 January 2011 - 05:34 PM, said:

Or the point where the Kelvin scale is better?

The Kevin scale is most useful in such situations.

Here's how works: "It's 6 Kevin outside." "You mean 6 Kelvin, right?" "No. It took 6 seconds for the snot in Kevin's nose to freeze."

There was a 3 Kevin day here a few years ago. This year, there was an 8 Kevin on Monday (-15 F).

[Korbal Broach]

Starshade, on 27 January 2011 - 12:27 AM, said:

Korbal Broach, on 27 January 2011 - 12:11 AM, said:

yes it can and does. I was out in just a t-shirt for a bit this afternoon.

I know it's been warmer, but a t-shirt? You're not one of those people who wear shorts outside in January, are you? (Because that is just _wrong_!)

I rarely wear shorts in the middle of summer, so no i'm not one to wear shorts in January. On the other hand there's nothing more fun than skating down the Rideau canal with just a t-shirt, or hitting the outdoor hockey rinks.

[Adjutant Stormy~]

You crazy canucks. Does a good solid body check hurt more, or less, from the cold?

[RodeoRanch]

The fucking puck sure hurts more when it's frozen solid.

[Menandore]

What's this? Small talk about the weather and it hasn't been taken over by Brits yet?

It's been a strange winter on this side of the pond. Britain came to a standstill in December, chaos in the airports, train stations etc, more snow than some of us have seen in our lifetimes. On the continent as well, much more snow than usual.

Finland on the other hand has been strangely warm. We expected it to be similar to last year - in line with Canada so -20 to -30 all through January and February (NB this is based on our limited knowledge having only just moved here a year ago). But since we got back from xmas hols it's been hovering around -5. Practically tropical! We have had a couple of -20 days but all in all it's been warm here. Still a shitload of snow everwhere though.

[Tsundoku]

You are all very strange indeed. Why live there? Why was there migration to these frozen wastelands???

[Mentalist]

running away from all the viruses and mosquitos.

[Menandore]

Sombra, on 27 January 2011 - 08:20 AM, said:

You are all very strange indeed. Why live there? Why was there migration to these frozen wastelands???

Cos our ancestors weren't criminals so we got to choose a cold environment without poisonous snakes, poisonous (big-ass) spiders, sharks, crocodiles and deadly sting-rays. This is why I still maintain Scotland is the best place in the world to live. The most dangerous animal we have is the wild haggis (they're small and shy but if you corner one they get vicious).

[MTS]

Menandore, on 27 January 2011 - 08:52 AM, said:

Sombra, on 27 January 2011 - 08:20 AM, said:

You are all very strange indeed. Why live there? Why was there migration to these frozen wastelands???

Cos our ancestors weren't criminals so we got to choose a cold environment without poisonous snakes, poisonous (big-ass) spiders, sharks, crocodiles and deadly sting-rays. This is why I still maintain Scotland is the best place in the world to live. The most dangerous animal we have is the wild haggis (they're small and shy but if you corner one they get vicious).

Sure, we've got all those things, and sometimes I think Australia is nature's prison for the excessively dangerous, but the Northern Hemisphere have bears (a.k.a. godless killing machines), wolves, big mountain cats, adders, vipers, wild boar, black widows etc.

I maintain you're all a bunch of pansies.

[Captain Beardface]

RodeoRanch, on 27 January 2011 - 12:04 AM, said:

After weeks of -30 or lower, -15 can feel positively balmy

Hence why I live in southern Georgia.

[Captain Beardface]

Mentalist, on 27 January 2011 - 08:22 AM, said:

running away from all the viruses and mosquitos.

I'd rather not deal with frostbite or hypothermia or snow or icey roads or negative temps.

[MTS]

Yep, just take a bath in Aerogard and you're golden (brown, that is ).

This post has been edited by MTS: 27 January 2011 - 12:00 PM

[cerveza_fiesta]

D, on 27 January 2011 - 02:58 AM, said:

Kallyfudge, on 27 January 2011 - 01:17 AM, said:

I would like to see and explanation of why it isn't because of evaporation, mainly because part of the freezing is because of evaporation.

Evaporation = liquid becoming gas

This liquid is becoming solid, ergo it is not evaporation.


On a related note, if you visit Canada in mid-winter, don't drink a lot of hot water before stepping outside. We've all seen the horrors...

When you have water at 100ish deg C entering air at -40ish deg C, a difference of 140deg C (same difference in Kelvin) you get much more rapid cooling than, say, cold tapwater at 5 degC entering the same temperature of air - a difference of only 45 deg C. Given that heat transfer from the liquid to the surrounding air occurs much faster at greater temperature differential, saying hot water has "farther to go" to reach -40 isn't entirely correct since it is cooling at a much more rapid rate than water that starts at 5deg C.

Water at 100deg C has a much greater evaporation potential than cold water. Evaporation removes heat from the bulk liquid, cooling it more rapidly. That's why you cover pots on the stove to trap the steam when you want to boil water faster.

Key in the phenomenon is atomization. Heat transfer to the environs through convective, conductive and evaporative cooling happens only on the surface of the liquid, so all else equal the only way to accelerate heat transfer is to increase the surface area for a given volume of liquid. You can increase the surface area in a lot of ways - like pouring it on a surface, using a long skinny container (a tube), or by shredding into tiny droplets. The smaller the droplets, the greater the surface area. The greater the surface area, the faster the cooling. Additionally, smaller droplets have less volume per surface area, so it takes less time for each droplet to reach freezing temperature.

Key to formation of droplets is surface tension, which quantifies (more or less) the amount of force required to part the surface of a liquid. Lower surface tension = greater ability to form smaller droplets. Water at 100deg C has a much lower surface tension than cold water, so it fragments more easily.

So with the concepts above you have:

• High rate of heat transfer due to temperature differential
• Increased evaporation due to high temperature of the liquid
• Large surface area because the liquid is tossed into the air, allowing it to fragment into small droplets.
• Increased surface area per volume of each droplet which shortens the time required to freeze.
• Hot water facilitates formation of smaller droplets because it has reduced surface tension.

A lot of the cloud that you see in the video is condensed steam - but the remaining liquid does in fact turn into snow and ice pellets.

Same concepts apply at ski hills that make snow. Pressurize water through nozzles to make tiny drops and feed them into a blast of freezing cold air. Result = snow and ice pellets.

SCIENCE!

This post has been edited by cerveza_fiesta: 27 January 2011 - 02:20 PM