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Coldest natural temperature in the universe?


Elthy
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Just a random showerthought:

Were there ever temperatures (significantly) below the cosmic background radiation other than those created by intelligent life? It takes realy advaced technologies to reach temperatures that low, i cant imagine a natural process that could achive that. Without active cooling everything would just cool to the cosmic background of about 2.7K, right?

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There are negative temperatures as well, according to the course of the statistical physics.

Because the temperature is a statistical abstraction which integrates properties of statistical states of the system elements (say, particles)

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14 hours ago, kerbiloid said:

There are negative temperatures as well, according to the course of the statistical physics.

Any good course in statistical mechanics, including Landau and Lifshitz, explicitly points out that while there are similarities between the statistics of inverted population states, such as these of lasing media, and statistics of a hypothetical medium with negative temperature, this similarity disappears once you consider all of the interactions the medium is involved in, and is therefore not a negative temperature in any meaningful sense. Indeed, this fact is often used to derive some theoretical limits on lasing efficiency.

This is much like pointing out that by rotating a mirror, you can observe reflected object move at superluminal speeds, and then claiming that according to some optics texts, superluminal speeds are possible. That's not at all the implication nor the intended conclusion.

Edited by K^2
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You should read the given more attentively.

It wasn't a question if we can cool a real body below the absolute zero.
It was a question of the lowest temperature existing in the universe.

And the vol. V of the standard course of theoretical physics is pretty descriptive in this sense.

Edited by kerbiloid
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49 minutes ago, kerbiloid said:

And the vol. V of the standard course of theoretical physics is pretty descriptive in this sense.

The closest I can even think of what you might be thinking of in V is the fact that temperature goes imaginary inside the event horizon of a black hole, as T√g00 = constant in equilibrium, and g00 goes negative when r < rs. There are no regions of space-time that can go to negative temperature, however, following the same derivation.

If you are thinking of something else, please, let me know which chapter you're thinking of.

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11 hours ago, K^2 said:

Lifexcrementsz

:D

Sidebar:

... We have a very aggressive / effective nanny system active on this site - one of the reasons I don't mind my 11yo daughter reading it.  The kids are safe! 

But... Has anyone actually listened to middle school kids talk?  They can make a Sailor blush! 

Edited by JoeSchmuckatelli
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38 minutes ago, JoeSchmuckatelli said:

Has anyone actually listened to middle school kids talk? 

Yes. Since being one of them. 

Don't accuse them, they don't have schoolbooks how to speak properly, so get experienced speakers much later, while in school their speech is primitive and full of repeated short words or ugly, unnatural tree-like constructions.

Edited by kerbiloid
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2 hours ago, JoeSchmuckatelli said:

:D

Sidebar:

... We have a very aggressive / effective nanny system active on this site - one of the reasons I don't mind my 11yo daughter reading it.  The kids are safe! 

But... Has anyone actually listened to middle school kids talk?  They can make a Sailor blush! 

my own use of profanity has diminished significantly from grade school. when i do use it i try to avoid going for the usual four letter words and express my vulgarity with a much more refined vocabulary. if i am disappointed at hearing children swear. its usually for their lack of imagination. 

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On 2/21/2022 at 11:53 PM, K^2 said:

Any good course in statistical mechanics, including Landau and Lifshítz, explicitly points out that while there are similarities between the statistics of inverted population states, such as these of lasing media, and statistics of a hypothetical medium with negative temperature, this similarity disappears once you consider all of the interactions the medium is involved in, and is therefore not a negative temperature in any meaningful sense. Indeed, this fact is often used to derive some theoretical limits on lasing efficiency.

Aye.

A system with a statistically "negative" temperature is actually hotter than an infinitely hot system because it fills high-energy states before it fills low-energy states.

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59 minutes ago, sevenperforce said:

Aye.

A system with a statistically "negative" temperature is actually hotter than an infinitely hot system because it fills high-energy states before it fills low-energy states.

And again. The given was about the lowest possible temperature, not about its physical nature or possibility to use.

Mathematically speaking, -1 < 0.

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13 hours ago, kerbiloid said:

And again. The given was about the lowest possible temperature, not about its physical nature or possibility to use.

Mathematically speaking, -1 < 0.

The context of the “random showerthought” in the OP was how much cooling something could undergo in nature. You cannot reach a negative-temperature system population inversion by “natural” cooling. 

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The absolute temperature is a signed value with accurate scientific definition, and doesn't need in somebody's interpretations and understanding.

It can be both positive and negative, and negative values are colloquially called "cooler" than positive ones.

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5 hours ago, kerbiloid said:

The absolute temperature is a signed value with accurate scientific definition, and doesn't need in somebody's interpretations and understanding.

Temperature isn't a number. Temperature is a physical quantity. It is defined as the inverse of the derivative of entropy with respect to energy. If that quantity cannot go negative, temperature cannot go negative. That quantity cannot go negative for any physical system. And the very book you claim as the source explains that. So unless you want to quote a specific chapter or alternative source, you're wrong based on the very material you are quoting. Again.

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1/T = dS/dQ, but you can keep inventing new ideas as long as you wish.

11 minutes ago, K^2 said:

Temperature isn't a number.

A number is a mathematical computable representation of a physical value quantity.

(Or take the vol. V in library and study it, like I was doing for a whole year.)

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1 hour ago, kerbiloid said:

1/T = dS/dQ, but you can keep inventing new ideas as long as you wish.

You do know that dS/dQ is derivative of entropy with respect to (heat) energy, right? And you can solve 1/T = dS/dQ for T, surely? Or are you not aware that inverse of x is 1/x?

Please, explain to me, how it is that you are trying to argue about thermodynamics with me and, infinitely worse, with Landau, when you can't compare two statements of the formula and tell that it's the same formula.

I've studied thermodynamics from people who graduated from Phystech. My father also had a doctorate from there. So lets just say I've read Course of Theoretical Physics a few times. But I also actually learned from it, not just memorized a few formulas without being able to do the most rudimentary analysis of it.

So again, please, do point to the place in V that claims that dS/dQ can turn negative. Because I can point you to numerous places that show explicitly that it can't. And I already quoted one of them, from the section on relativity. But you don't have to touch relativity. For starters, if you actually understood anything, and I do mean anything from vol V, you'd know that dS/dQ < 0 implies heat capacity < 0. But more excitingly, there has to be a temperature gradient, since dS/dQ is continuous, implying dS/dQ = 0 somewhere, making the temperature infinite. And oughtn't that do something interesting according to vol. V. Hm... If there was only a way to turn the arcane symbols inscribed on pages into actual knowledge.

Honestly, reading material and comprehending it is clearly very different concepts. But you insisting that I should be reading Stats when I've been quoting directly from it over several posts and you seem to be unaware of it is just hilarious.

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