Author Topic: Why does cold temp has a limit of -273C/0k and high temp has no limit?  (Read 7289 times)

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Offline timb

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #25 on: December 19, 2016, 02:04:31 am »
Imagine the "shrinkage" at 0K! I mean, skinning dipping on a cold day is bad enough...
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Offline xrunner

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #26 on: December 19, 2016, 02:19:09 am »
Well since we're asking these types of questions - what would be the maximum negative charge obtainable? Would it be the combination (if it were possible) of every single electron in the Universe?
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Online IanB

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #27 on: December 19, 2016, 02:58:07 am »
Well since we're asking these types of questions - what would be the maximum negative charge obtainable? Would it be the combination (if it were possible) of every single electron in the Universe?

How are you going to measure "charge" in this question? A collection of charge spread out thinly is an entirely different prospect than a collection of charge bunched up close together. And then you have to ask, how close together?
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Offline LokiChaos

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #28 on: December 19, 2016, 05:19:12 am »
I am going to answer "what is the maximum negative charge?" with "mu"

If you could hypothetically concentrate every negatively charged particle (not just electrons, though most others have short lifespans, one would want to include antiprotons, muons and tau… W Bosons also can have a negative charge, but getting them wrangled is more complex matter) in the observable universe in a specified region in space, but very quickly the energy would collapse such an assembly into a black hole (never mind there isn't enough energy within the entire observable universe to actually do this).
Source and more musings: https://what-if.xkcd.com/140/

You could calculate how close you could force two electrons  together before it collapses into a singularity. 
On the other hand, electrons themselves are rather weird too, and general relativity and quantum mechanics don't combine very well.
 

Offline NiHaoMike

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #29 on: December 20, 2016, 07:01:17 am »
Yeah, well the other spectrum, electronics does not really work in the picoherz and the terahertz region.
Solid state oscillators that work in at a few hundreds of THz are very common and cheap. And so are diodes that can detect/rectify that.
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Offline Gyro

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #30 on: December 20, 2016, 02:12:55 pm »
Imagine the "shrinkage" at 0K! I mean, skinning dipping on a cold day is bad enough...

Theres no helping your 'Junk' size fixation, not long ago you were bragging about it dipping in the toilet bowl!  ::) ;D

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« Last Edit: December 20, 2016, 02:18:10 pm by Gyro »
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Offline timb

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #31 on: December 20, 2016, 05:55:07 pm »
Imagine the "shrinkage" at 0K! I mean, skinning dipping on a cold day is bad enough...

Theres no helping your 'Junk' size fixation, not long ago you were bragging about it dipping in the toilet bowl!  ::) ;D

https://www.eevblog.com/forum/chat/how-good-is-your-aim-at-night/5/

Maybe I just have a really small toilet! Did you ever think of that?! (For the record, I don't...but that's not the point!) XD

Anyway, at 0K, I don't think anybody can brag about size. At that temperature I suspect an outie becomes an innie! Or, would it even get the chance? I guess *any* exposed skin would instantly freeze, like being exposed to liquid nitrogen. So I guess you wouldn't have to worry about, because you'd be dead...

I wonder what the coldest temperature a naked human can survive at? (Even for just a few seconds...) Hmmm...
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Offline Gyro

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #32 on: December 20, 2016, 06:25:35 pm »
Quote
Maybe I just have a really small toilet! Did you ever think of that?! (For the record, I don't...but that's not the point!) XD
;D

Quote
Anyway, at 0K, I don't think anybody can brag about size. At that temperature I suspect an outie becomes an innie! Or, would it even get the chance? I guess *any* exposed skin would instantly freeze, like being exposed to liquid nitrogen. So I guess you wouldn't have to worry about, because you'd be dead...

Actually I think there is a mechanism that allows you to briefly put your skin in contact with liquid Nitrogen. I think it works because the layer immediately next to the skin instantly vapourizes due to the huge temperature difference giving an insulating layer of Nitrogen gas. Obviously it would only work until the surface of the skin retains enough heat. A similar effect allows droplets of water to dance on top of a very hot plate (again buffered by vapour).

I can't remember where I saw the demonstration (if I didn't in fact dream the whole thing!) but obviously, don't try this at home folks!  :scared:

P.S. Ahah,  the Leidenfrost effect...   
« Last Edit: December 20, 2016, 06:27:57 pm by Gyro »
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Offline CatalinaWOW

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #33 on: December 20, 2016, 06:27:31 pm »
Your question of cold temps survival is too complex to answer.  Survival of arbitrarily low temps for a few seconds isn't a problem.  But combined with the vacuum that normally would exist at those temps you might come up with something lethal in a few seconds.  Or immersed in a lake of liquid helium you might get survival down in the seconds range. 

A few seconds of very low temps is actually refreshing.  When working in a very hot climate with access to LN2 (~72 K) we would occasionally dump some down pant legs (loose fitting obviously) or shirt backs.  Between small quantities and Leidenfrost it actually felt good.  I am sure were risking small areas of frostbitten skin, but nothing lethal.  I don't even recall a single instance of frostbite.

I would guess that in most cases it takes significant numbers of seconds to get serious damage (loss of fingers, ears and the like), and minutes for actual lethality.  The body has a reasonably long thermal time constant.  The short survival times in Arctic waters is due to an almost ideal combination of temperature, heat capacity, conductivity and other factors in cold sea water.
 

Offline LokiChaos

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #34 on: December 20, 2016, 09:17:47 pm »
Survivability is more a matter of heat transfer and less about the actual temperature.  The temperature differential matters, but is only one factor and dwarfed by others.

Take space (in the shadows, so we are cold and not heated by the solar radiation), you'd asphyxiate well before you freeze to death.  Initially most heat loss would be from your blood and other liquids (mostly water) boiling off, this would actually be most of the total heat loss (and decidedly fatal if you somehow didn't need oxygen).  After that initial stage the only thermal losses would be blackbody radiation and it would take a total of around 8-12 hours for you to freeze solid (depend on body mass and other factors).

Even immersed in liquid nitrogen would take hours simply because of how slowly the internal heat would take to conduct though the body without the circulatory system to transport it. 

At what point you'd die is a little complex, as the cellular processes slow down and eventually cease at lower temps, a quick search shows known instances of body temps as low as 18C being recovered from, so the lower limit is rather fuzzy.  However even a drop of a few degrees of you core body temp leads to hypothermia that will quickly render you unable to remove yourself from the conditions and eventual death.
 

Offline grumpydoc

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #35 on: December 20, 2016, 11:03:24 pm »
At what point you'd die is a little complex, as the cellular processes slow down and eventually cease at lower temps, a quick search shows known instances of body temps as low as 18C being recovered from, so the lower limit is rather fuzzy.

Wikipedia cites 9oC during Deep Hypothermic Circulatory Arrest although the body is not generally cooled this much in typical practice.

Individuals, especially children have survived very prolonged periods of cardiac arrest having fallen into frozen lakes.

As they say in resus - "you are not dead until you are warm and dead"!

However the range of temperatures where we are comfortable and at which our biochemistry works are largely down to the accident of life having evolved on a planet with large amounts of liquid water and a surface pressure of about 100kPa. Other solutes have been suggested from liquid hydrogen to plasma. It would be neat to meet a Hydrogen Flouride based life-form but you would not want to shake whatever it uses as a hand  :)

I suspect, however, that water+carbon based chemistries are probably "best" although that does not necessarily mean that another system could not work.
 

Offline VK3DRB

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #36 on: December 24, 2016, 08:28:20 am »
As a side note it might be worth mentioning that also the pressure range is not very symmetric from our perspective. The absolute vacuum is just 1bar (or 100 kPa) away but it's relatively simple to achieve pressure values that are magnitudes higher and near the code of our planet, it's supposed to be 330 Gigapascal, letting aside Neutron stars and the like...

Let's assume one can travel to the centre of the core of our planet and and there was an empty room there where you could stay for a few minutes and survive the heat and pressure. Would you float around weightless as if you were in outer space?
 

Online IanB

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #37 on: December 24, 2016, 09:28:10 am »
Let's assume one can travel to the centre of the core of our planet and and there was an empty room there where you could stay for a few minutes and survive the heat and pressure. Would you float around weightless as if you were in outer space?

Yes. The gravitational pull would be the same in all directions so it would cancel out to nothing.
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