# Abs zero degrees K ?

#### drjohsmith

Joined Dec 13, 2021
499
There have been a few comments on the forums recently including references to zero K

which got me wondering,
is it possible to go below zero K ?

My thought was,
zero K , atoms stop moving,
which is a rather old model now,
what about Quarks et all , do they stop moving ?

A search,
https://www.sciencedaily.com/releases/2013/01/130104143516.htm

Seems - Kelvin is possible

Amazing...
way beyond me,
but any thoughts ?

I'm just wondering abstractly ,

is zero K a barrier, similar to the sound barrier, or faster than light travel, or the minute mile,

as in once we have seen how to break it, its "easy"

Any thought,

#### crutschow

Joined Mar 14, 2008
30,753
Zero K is when the molecules/atoms stop moving.
It may be an old model, but it's still valid.

There's no way to slow down Quarks, et all.
They are at a much lower level of abstraction, and their movement has nothing to do with temperature.

#### drjohsmith

Joined Dec 13, 2021
499
Zero K is when the molecules/atoms stop moving.
It may be an old model, but it's still valid.

There's no way to slow down Quarks, et all.
They are at a much lower level of abstraction, and their movement has nothing to do with temperature.
But it does seem we can get below 0 Kelvin from the link , but it was beyond me. Hence asking for thoughts on paper

#### dl324

Joined Mar 30, 2015
15,097
But it does seem we can get below 0 Kelvin from the link , but it was beyond me. Hence asking for thoughts on paper
By definition, there are no negative Kelvin temperatures.

From space.com. Coldest temperature in the universe = 1K

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#### ZCochran98

Joined Jul 24, 2018
214
There's also a statistical thermodynamics reason we can't reach 0 K, which is the $$\beta$$ parameter:
$\beta \equiv \frac{1}{k_B T}$
This is a parameter that describes, in a sense, the amount of entropy associated with thermal energy (or, more precisely, the change in entropy, as entropy $$S$$ relates to it via $$\beta = k_B^{-1}\partial_E S$$). What this means is that at $$T = 0$$, there would be (roughly-speaking) an infinite change in thermodynamic entropy per unit of energy within a system, which is impossible to achieve. More intuitively, this describes how much the system will randomize with a change of energy (and infinite randomization is meaningless).

The concept of "negative temperature" does exist, but is physically impossible as well, in the traditional sense. If you define temperature as a measure of Boltzmann's entropy (aka: via the $$\beta$$ above), then for very, very specific confined systems you can end up with what mathematically corresponds to negative temperature. A real negative temperature would correspond to, effectively, "absolute hot" - something hotter than any positive temperature could reach.

The main problem is how temperature is defined, so you can get some really weird results if you're mixing definitions (like the entropy-based definition of temperature vs. the kinetic energy definition of temperature). From a statistical thermodynamics (entropy)-based point of view, negative temperature makes sense in very, very specific cases. But for the kinetic energy definition (and, frankly, the standard intuition and experience) of temperature, from which the Kelvin scale was originally derived/created, negative temperature has no meaning.

Here's a page on $$\beta$$, and here's one on negative temperature.

#### xox

Joined Sep 8, 2017
782
There have been a few comments on the forums recently including references to zero K

which got me wondering,

is it possible to go below zero K ?

My thought was,

zero K , atoms stop moving,

which is a rather old model now,

what about Quarks et all , do they stop moving ?

A search,

https://www.sciencedaily.com/releases/2013/01/130104143516.htm

Seems - Kelvin is possible

Amazing...

way beyond me,

but any thoughts ?

I'm just wondering abstractly ,

is zero K a barrier, similar to the sound barrier, or faster than light travel, or the minute mile,

as in once we have seen how to break it, its "easy"

Any thought,

First of all it is important to remember that temperature is a MACROSCOPIC measurement of a system. Whenever large differences develop on the microscopic scale however, thermodynamically negative temperatures can and do occur.

A simple example of this is the "population inversion" effect in the operation of lasers. You have a certain number of atoms in the ground state while the rest are highly excited.

Eventually the interaction between the distinct states causes the system behave rather unusually. As more and more energy is added to the system, suddenly the entropy starts to DECREASE (the system becomes more ordered). This is exactly opposite to homogeneous systems, where adding energy to the system results in an INCREASE of entropy.

#### xox

Joined Sep 8, 2017
782
But for the kinetic energy definition (and, frankly, the standard intuition and experience) of temperature, from which the Kelvin scale was originally derived/created, negative temperature has no meaning.
Even classical kinetic system can achieve negative temperatures. Again it just requires a large enough degree of internal differences in order to cause the temperature to "flip" in the negative direction.

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#### drjohsmith

Joined Dec 13, 2021
499
Thank you guys

Can I highlight my aims

I woke with a though, and when I did google, I was surprised when I read what I thought was saying that below abs zero is possible,

Now,
I know if posted on a Physics forum,
I am instantly in undated with references to things I have know knowledge of
My come to forum is here,
as its "manned" ( Sorry Wendy ) by engineer,
very knowledgeable engineers, but , you speak my language

What Im taking from this
is Kelvin is defined in terms of "classic" atomic theory
and zero is when atoms stop "vibrating"

But other ways can be used to "just" get lower in "temperature" as in they can absorb "heat" before they come to a set Kelvin value more than if they were at zero degrees.

Which I find a pivotal moment
rather like when I learnt that electrons were not "lumps" orbiting a nucleus, and light is a wave and a particle at the same time,

#### drjohsmith

Joined Dec 13, 2021
499
I think your teeth might not be chattering at -272°C
:->

I don't know if at 1K my jaw would be able to move !

I used to have a professor ,
who would swill liquid nit around there mouth and spit it out !
NOT to be tired , and who know why they first tried it !

#### Delta Prime

Joined Nov 15, 2019
1,311
:->

I don't know if at 1K my jaw would be able to move !

I used to have a professor ,
who would swill liquid nit around there mouth and spit it out !
NOT to be tired , and who know why they first tried it !
I believe Mr.Leidenfrost first tried it!

#### DickCappels

Joined Aug 21, 2008
9,289
@drjohsmith The answer to your question is to be found in the abstract of the article to which you linked. Simple as that.