Author Topic: Why does cold temp has a limit of -273C/0k and high temp has no limit?  (Read 7293 times)

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Offline MrOmnos

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How hot can it get?
« Last Edit: December 16, 2016, 06:15:39 pm by MrOmnos »
 

Offline Arjan Emm

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #1 on: December 16, 2016, 04:24:37 pm »
Physics thinks the highest possible temperature is the Planck temperature, around 1.4*10^32 K. So there is probably a limit. It's just strange that it's so incomprehensively high and -273 is so close to our comfort zone.

How incomprehensible?
supernovae around 10^10K
Large hadron collider 10^18K
Anything a few decades higher is bigbang theory.
« Last Edit: December 16, 2016, 04:43:19 pm by Arjan Emm »
 

Offline SeanB

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #2 on: December 16, 2016, 04:38:17 pm »
Look at in in Kelvin, where zero kelvin is where all atomic motion ceases. You cannot have lower energy than zero, but the high limit is set by the ability of the universe to contain the particle travelling at C.

Best we have reached is ca 0.01K, and that is really hard to get to, and where measuring the temperature is very difficult, as the measurement adds energy to the system. Below around 0.5K many things behave as a single particle, or at least He does, which is the gas most commonly used.
 

Offline Spuddevans

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #3 on: December 16, 2016, 04:43:34 pm »
Is it something to do with the point that you can't directly generate cold, you can only remove heat, but you can always inject more energy, ie add heat.

Tim
 

Offline grumpydoc

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #4 on: December 16, 2016, 04:44:52 pm »
I don't claim to understand it but apparently negative Kelvin is possible

https://www.mpg.de/research/negative-absolute-temperature
 

Offline Gyro

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #5 on: December 16, 2016, 04:48:25 pm »
It's always struck me as a bit odd too that we exist at such close proximity to absolute zero. Yes I know it's down to our chemistry but it still feels a bit strange that you can reach an equivalent temperature differential in the oposite direction with a bog standard soldering iron!
Chris

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Online Benta

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #6 on: December 16, 2016, 04:54:17 pm »
Just to correct the original question:

Absolute zero is 0 K
Which corresponds to appr. -273 degrees Celsius.

There is no such thing as -273 K.

 

Online Kleinstein

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #7 on: December 16, 2016, 04:58:31 pm »
If we are close to zero temperature depends on the scale on a logarithmic scale, there is plenty of room to both directs. The lowest temperature reached are also quit a bit lower than 10 mK. Those experiments with Bose-Einstein condensates are at micro kelvins.

With non equilibrium systems, there are different ways to define a temperature. One is to look at the population of two states of different energy. The higher the temperature the more equal probabilities for the two states. However for some reason the higher level is more likely than the lower one, one could call this a negative temperature - or one higher than infinite, depending on how you look at it.
 

Offline Arjan Emm

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #8 on: December 16, 2016, 05:29:35 pm »
It's always struck me as a bit odd too that we exist at such close proximity to absolute zero. Yes I know it's down to our chemistry but it still feels a bit strange that you can reach an equivalent temperature differential in the oposite direction with a bog standard soldering iron!

I agree with your feeling. But it is not down to our chemistry but chemistry in general. Molecular bonds are really weak, that's also why they can get as complicated as us humans. Between 400 degrees C and say 2000C most big molecules fall apart. At only 10.000K chemistry ceases to exist and all you have is single atoms, many already stripped of many of their electrons.
 

Offline Arjan Emm

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #9 on: December 16, 2016, 05:51:32 pm »
If we are close to zero temperature depends on the scale on a logarithmic scale, there is plenty of room to both directs. The lowest temperature reached are also quit a bit lower than 10 mK. Those experiments with Bose-Einstein condensates are at micro kelvins.

With non equilibrium systems, there are different ways to define a temperature. One is to look at the population of two states of different energy. The higher the temperature the more equal probabilities for the two states. However for some reason the higher level is more likely than the lower one, one could call this a negative temperature - or one higher than infinite, depending on how you look at it.

Good points. I guess cooling down to almost 0 K, let's say 10^-30 K is just as impossible to achieve as 10^30 K heat.
« Last Edit: December 16, 2016, 05:57:42 pm by Arjan Emm »
 

Offline CatalinaWOW

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #10 on: December 16, 2016, 06:12:57 pm »
It's always struck me as a bit odd too that we exist at such close proximity to absolute zero. Yes I know it's down to our chemistry but it still feels a bit strange that you can reach an equivalent temperature differential in the oposite direction with a bog standard soldering iron!

It is a consequence of when we live in the age of the universe.  When the universal background is down to 3 K.

Arthur C. Clark expressed it poetically.  He spoke wistfully of what it might have been like to live in the early universe, when everything was close by and high energy events were commonplace.  When entropy had just started to increase.   He then predicted that far in the future, as the heat death of the universe neared, any intelligences living then would be wistful of us who lived when the universe was young.
 

Offline 0xdeadbeef

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #11 on: December 16, 2016, 06:41:55 pm »
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.

I guess as with the temperature and other things, it's just a matter of anthropocentric worldview: as we can only exist in certain conditions, it's pointless to wonder why the conditions allow us to exist. As if they wouldn't, we couldn't wonder.
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Offline ajb

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #12 on: December 16, 2016, 07:45:37 pm »
I don't claim to understand it but apparently negative Kelvin is possible

https://www.mpg.de/research/negative-absolute-temperature

Quote
Atoms at negative absolute temperature are the hottest systems in the world

Sounds like somebody accidentally rolled over an integer somewhere.
 
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Online MasterTech

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #13 on: December 16, 2016, 08:56:07 pm »
It's always struck me as a bit odd too that we exist at such close proximity to absolute zero. Yes I know it's down to our chemistry but it still feels a bit strange that you can reach an equivalent temperature differential in the oposite direction with a bog standard soldering iron!
True, phillosophically one could argue that the Earth was designed as a low power system
 

Offline NANDBlog

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #14 on: December 16, 2016, 10:25:22 pm »
Yeah, well the other spectrum, electronics does not really work in the picoherz and the terahertz region.
 

Online T3sl4co1l

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #15 on: December 17, 2016, 12:09:01 am »
It's analogous to saying "there is no voltage [magnitude] below 0V".  And that thermal noise guarantees you will always have slightly more than zero, no matter how you measure it (except also at absolute zero temperature).

Different particles, and different aspects of the system, can possess different temperatures.  A system need not always be in perfect equilibrium; there needn't even be an exchange mechanism between the different parts of the system.  (Thermodynamics assumes there will eventually be some sort of exchange, which in real systems, always manages to happen in the end.  Over finite time scales, things can be very different: by pumping a magnetic field, you can chill the nuclear spins of any nonzero-spin atoms.  The heat energy contained therein is extraordinarily small, of course, but it's also fascinating that the thermal time constant is in the tens of seconds -- for a quantum system that's room-temperature (or not) and quite low energy (~ueV per flip).

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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 #16 on: December 17, 2016, 12:20:51 am »
Negative absolute temps are very different than one colloquially thinks of temperature, they are a result of systems with high constrained sets of possible states, and a definition of temperature grounded in statistical mechanics.

The interesting thing is negative temps are HOTTER than any positive temp, not colder.  Energy always flows out of a negative absolute temp systems into a positive temp one.  https://en.wikipedia.org/wiki/Negative_temperature

A commonly encountered system is in a laser in a state of population inversion.
 

Offline Tinkerer

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #17 on: December 17, 2016, 01:18:16 am »
Well, I dont think asking why we exist so close, relatively speaking, to absolute zero is the correct question. The question should be why are the energy levels needed for chemistry to exist so close to absolute zero. At higher temperatures, you dont really get much chemistry happening, its all mostly gas and plasma as the atoms are too energetic to to chemically interact in most cases.
The above leads to an interesting thought. What if electrons and such were more strongly bound to their respective atoms? etc etc, what if bonds were much stronger?
 

Offline LokiChaos

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #18 on: December 17, 2016, 02:11:04 am »
You'd end up with a lot less chemistry happening as most places would be too cold to have large numbers of interesting reactions (this would also likely preclude life in a sense we are familiar with).

Chemical reactions of all sorts would be rarer, but those that do occur would be far more energetic and the products far harder to break apart.  There are a lot of different effects, some depend on if you just increase the strength of the electromagnetic force, or increase the charge quanta, or if the other fundamental forces also scale as well.
 

Online T3sl4co1l

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #19 on: December 17, 2016, 04:32:28 am »
Well, I dont think asking why we exist so close, relatively speaking, to absolute zero is the correct question.

What the hell does that mean?  In other words -- relative to what?  :-//

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Offline neil t

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #20 on: December 17, 2016, 05:14:00 am »
It's all relative to what we can and can't measure or prove or disprove ie supposing nothing travels faster than the speed of light if It did could it be measured with current technology.
or would it be measured by unproven theory. based on what we know or think we know at this time.
« Last Edit: December 17, 2016, 05:15:37 am by neil t »
 

Offline mrpackethead

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Re: Why does cold temp has a limit of -273K and high temp has no limit?
« Reply #21 on: December 17, 2016, 05:59:33 am »
Look at in in Kelvin, where zero kelvin is where all atomic motion ceases. You cannot have lower energy than zero, but the high limit is set by the ability of the universe to contain the particle travelling at C.

Best we have reached is ca 0.01K, and that is really hard to get to, and where measuring the temperature is very difficult, as the measurement adds energy to the system. Below around 0.5K many things behave as a single particle, or at least He does, which is the gas most commonly used.

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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 #22 on: December 17, 2016, 06:17:36 am »
At very low temps quantum effects crop up at a macroscopic level because the number of states is so restricted that the normal classicalization that happens in statistical mechanics can no longer occur.  You get second sound, third sound, new states of matter, superconductivity, superfluidity, etc. 

In some ways it's a shame we generally exist at such /high/ temperatures, imagine if we could have superconductive materials at our "room temperature"!
 

Offline Galenbo

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #23 on: December 17, 2016, 12:05:12 pm »
How hot can it get?

When I was 12y old, or before physics studies, I would have understood it like:

* Temperature in Kelvin is like the amount of inside random movement.
* 0K = zero movement
* Random movement is not directional. It's like light on, light off, light half on.
* Much movement creates heat, you can feel it on the surface.
 
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Offline Red Squirrel

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Re: Why does cold temp has a limit of -273C/0k and high temp has no limit?
« Reply #24 on: December 18, 2016, 11:42:44 pm »
Once you get down to 233K, anything colder and it all feels the same to me. :P

French swears start coming out at that temp.  :-DD
 


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