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### Author Topic: How was Absolute Zero discovered?  (Read 45215 times)

#### JP

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##### How was Absolute Zero discovered?
« Reply #100 on: 05/08/2011 15:38:23 »
I don't think Mr. Data will be joining us again, as he couldn't engage in debate without being rude to other forum members.

#### yor_on

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##### How was Absolute Zero discovered?
« Reply #101 on: 07/08/2011 17:46:10 »
Look, all of this is just irritating to me :)

I gave two simple definitions that clash with each other. Trying to mumble that there is such a thing as absolute zero, except in theory, also will mean that there is no 'motion'. If so there can be no fluctuations, as long as you find fluctuations inside our arrow of time you also have something that is in motion. the simple solution to this problem as I see it is to define it as such as it is outside Planck time. And that is a simple solution. Not doing so will get you into a place between a rock and a hard place.

As I see it, temperature is all about measuring motion, if that motion would exist inside Planck time I will expect a temperature.
=

Maybe we need to define it as collisions?

But if we do so, what would then then our virtual 'radiation' be?
« Last Edit: 07/08/2011 17:51:11 by yor_on »

#### imatfaal

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##### How was Absolute Zero discovered?
« Reply #102 on: 07/08/2011 18:07:47 »
I gave two simple definitions that clash with each other.
struggling to find the two simple definitions - can you requote them - they got lost in the melee.
Quote
Trying to mumble that there is such a thing as absolute zero, except in theory, also will mean that there is no 'motion'. If so there can be no fluctuations, as long as you find fluctuations inside our arrow of time you also have something that is in motion.
Your problem is that the definition of absolute zero is the theoretical temperature when entropy reaches zero - in the 19th century it was thought this would mean absolute stillness and lack of movement, it has not meant that for almost 100 years.

Quote
the simple solution to this problem as I see it is to define it as such as it is outside Planck time. And that is a simple solution. Not doing so will get you into a place between a rock and a hard place.
no; that solution is neither easy nor a solution.  Absolute zero  and the zero point energy are connected - but you are continuing Mr D fallacy if you insist they are the same.  Abs Zero is a temperature theorised over a system that is at its lowest entropy.  ZPE is a characteristic of individual entities and redefines the ground state as a state of motion.  The fact that Abs Zero is theoretical does NOT imply that ZPE is theoretical - we have good evidence of ZPE occurring in the lab.

Quote
Maybe we need to define it as collisions?
But if we do so, what would then then our virtual 'radiation' be?
There isn't really a problem with the definitions - nor is there a contradiction.  It isn't collisions; ZPE cannot be radiated away; and we don't need virtual radiation.

#### JP

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##### How was Absolute Zero discovered?
« Reply #103 on: 08/08/2011 18:14:38 »
Trying to mumble that there is such a thing as absolute zero, except in theory, also will mean that there is no 'motion'. If so there can be no fluctuations, as long as you find fluctuations inside our arrow of time you also have something that is in motion.
Your problem is that the definition of absolute zero is the theoretical temperature when entropy reaches zero - in the 19th century it was thought this would mean absolute stillness and lack of movement, it has not meant that for almost 100 years.

Quote
the simple solution to this problem as I see it is to define it as such as it is outside Planck time. And that is a simple solution. Not doing so will get you into a place between a rock and a hard place.
no; that solution is neither easy nor a solution.  Absolute zero  and the zero point energy are connected - but you are continuing Mr D fallacy if you insist they are the same.  Abs Zero is a temperature theorised over a system that is at its lowest entropy.  ZPE is a characteristic of individual entities and redefines the ground state as a state of motion.  The fact that Abs Zero is theoretical does NOT imply that ZPE is theoretical - we have good evidence of ZPE occurring in the lab.

Yor_on, this is the point I was trying to make.  Details like Planck scale effects are interesting, but they're just minor tweaks to the physics, and they don't really help with understanding the differences between ZPE and absolute zero, and why ZPE is achievable and absolute zero is not.

I still think the dice analogy is the simplest way of getting at it.  You can imagine the dice represent a very low-energy particle.  If you roll a die, the 1 represents it being in the ZPE state, while the 2-6 represent higher energy states that it might end up in due to quantum fluctuations.

If all you care about is the state of one particle, you roll one die.  There's a 1/6 chance in this case of it coming up a 1.  If you look at 100 particles, odds are that one of them will be in the ZPE state.

Temperature is only meaningful for a lot of particles.  I'm not sure on the technical definition of "a lot," but you're usually talking about a 1 with 20 or more zeros after it.  It's an average of the kinetic energy of the particles, so it can be represented as the average of all the numbers rolled on your dice.  Absolute zero in our dice case only happens when all the dice come up 1 at the same time.  If even a single die comes up 2, the temperature is slightly above absolute zero.  Imagine the odds against rolling all 1s on 100000000000000000000 dice!  In reality, you also have heat leaking into the system, so you can imagine someone constantly reaching in and turning one of your dice to a higher number, which obviously makes it impossible to stay at all 1's, even if you happen to somehow roll them.

Now, imagine that you've rolled those 100000000000000000000 dice.  Some of them are bound to be 1's, so even in a system whose temperature is above absolute zero, you have some particles in their ZPE states.

Of course, there's always the argument that dice aren't quantum particles, which is completely true.  You could apply quantum field theory to this problem as well, and include virtual particles, Planck-scales and many other fun things, but I don't see how it's any more enlightening than the dice example about why ZPE is achievable and T=0 K isn't.

#### Bored chemist

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##### How was Absolute Zero discovered?
« Reply #104 on: 09/08/2011 06:57:01 »
It's not like zpe is rare.
The (admittedly classical) KE of the electrons round an atom or molecule in the ground state are zpe.
The vibrational energy of most of the molecules you are breathing is zpe.
The obscure cases like liquid helium show it too.
All this stuff about quantum fields just makes it more complicated than it needs to be.

#### Johann Mahne

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##### How was Absolute Zero discovered?
« Reply #105 on: 09/08/2011 16:03:05 »
Quote
The vibrational energy of most of the molecules you are breathing is zpe.
BoredChemist,
I'm lost here.Totally.
Do you mean by this that zpe ("zero point energy") is a minimum state of energy of a molecule and that this can be achieved at ambient temperatures and not near zero kelvin?
If a nitrogen molecule is at ambient temperature then at what state are the electrons in?I thought they would be in a higher state than if the molecule was frozen?
Or are you saying that the electrons are in zpe because the molecules are in motion so that the kinetic energy is not appearing in the orbits of the electrons or nuclei vibrating?

#### Bored chemist

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##### How was Absolute Zero discovered?
« Reply #106 on: 09/08/2011 19:39:40 »
To get nitrogen into the first vibrational excited state you have to add quite a lot of energy. As I said, it is the equivalent of getting it very hot.
To get it into the first excited electronic state you have to get it very hot- say 10,000 degrees.

Most nitrogen molecules at normal temps only have rotational and translational energy.

#### yor_on

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##### How was Absolute Zero discovered?
« Reply #107 on: 10/08/2011 11:01:31 »
Yes, as long as we define it as two different states I have no real problem with ZPE. If we define it as the same as 'absolute zero' it got to be wrong.

Absolute zero is to my eyes where there can be no 'jiggling'. And that is to me the same as no longer being 'here'. Whatever we see is defined by its ability of interacting. If something interacts you will have to assume that there is something that allows it to do so. In my eyes that will be the 'vibrational energy' intrinsic to whatever you observe. As you say JP any temperature must be the result of something interacting, and if what (absurdity ad infinitum) 'interacts' would be at 'absolute zero' I would be wrong in my assumptions.

But I don't think I am.

As for Planck size, it's what defines what we can make sense of as I see it. That doesn't say that you can't have a mylliard bylliard different 'states' existing outside what we can observe, it just states that ''There there might be thygers' as there is no way we ever are going to observe them directly. And that's also why I prefer to place 'virtual particles' outside Planck size myself.

#### yor_on

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##### How was Absolute Zero discovered?
« Reply #108 on: 10/08/2011 11:11:59 »
What everyone seem to miss in this discussion is time. Whatever you observe is a direct result of you being inside a arrow of time, only delivering you in one direction, to your death. As long as nobody can prove me wrong in that assumption, and you can't :), then everything you define, whatever temporal direction, or no direction at all, is a direct result of observations made under that arrow. Only delivering you, and your experiment, one way. It constantly surprises me reading of diffuse definitions of systems being 2-dimensional and 'time reversible' as if this was  a defined truth. Symmetry is a truth, but time reversibility have still to be proven, and that goes directly to the truth that there can be no observations ever being able to be defined if we didn't have our arrow. People seem to miss that this is what makes all definitions able to stand the test of time :) If they're not constant under our arrow then they are no repeatable.

So times arrow has a lot to do with anything defined as 'vibrating', as I see it.

#### JP

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##### How was Absolute Zero discovered?
« Reply #109 on: 10/08/2011 14:35:35 »
As you say JP any temperature must be the result of something interacting, and if what (absurdity ad infinitum) 'interacts' would be at 'absolute zero' I would be wrong in my assumptions.

I don't think I said that, and if I put it that way, I made a mistake.  Although one reason you can never measure absolute zero is the uncertainty principle--that if you measure it, you inject some energy.

What everyone seem to miss in this discussion is time. Whatever you observe is a direct result of you being inside a arrow of time, only delivering you in one direction, to your death. As long as nobody can prove me wrong in that assumption, and you can't :), then everything you define, whatever temporal direction, or no direction at all, is a direct result of observations made under that arrow. Only delivering you, and your experiment, one way. It constantly surprises me reading of diffuse definitions of systems being 2-dimensional and 'time reversible' as if this was  a defined truth. Symmetry is a truth, but time reversibility have still to be proven, and that goes directly to the truth that there can be no observations ever being able to be defined if we didn't have our arrow. People seem to miss that this is what makes all definitions able to stand the test of time :) If they're not constant under our arrow then they are no repeatable.

Well, according to all experimental evidence, most quantum mechanics is time-reversible.  There's a possible exception for certain interactions involving the production of antimatter, which might explain why it's uncommon, but those interactions are rare and not really relevant to the features of temperature that we're discussing.  As you know, you can't prove a that any theory (time-reversibility, in this case) is absolutely correct in science, but you can show a lot of evidence for it, which is what's been done.

Also, time's arrow seems to arise from thermodynamics, which is the same place we get a definition of temperature.  If you needed time's arrow to define temperature, you'd be in trouble, since you'd have a circular definition.

#### imatfaal

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##### How was Absolute Zero discovered?
« Reply #110 on: 10/08/2011 14:38:21 »
Yes, as long as we define it as two different states I have no real problem with ZPE. If we define it as the same as 'absolute zero' it got to be wrong.
But Yoron - no one does!  (apart from dear old late lamented MrD)

Quote
Absolute zero is to my eyes where there can be no 'jiggling'. And that is to me the same as no longer being 'here'. Whatever we see is defined by its ability of interacting. If something interacts you will have to assume that there is something that allows it to do so. In my eyes that will be the 'vibrational energy' intrinsic to whatever you observe. As you say JP any temperature must be the result of something interacting, and if what (absurdity ad infinitum) 'interacts' would be at 'absolute zero' I would be wrong in my assumptions.
Yoron - but since the early 20th century we haven't defined it as "no jiggling" we have defined it as the lowest entropy state

Quote
As for Planck size, it's what defines what we can make sense of as I see it. That doesn't say that you can't have a mylliard bylliard different 'states' existing outside what we can observe, it just states that ''There there might be thygers' as there is no way we ever are going to observe them directly. And that's also why I prefer to place 'virtual particles' outside Planck size myself.
planck SIZE? - you can view things of planck mass with a decent magnifying glass, the planck length and time are were things get small and high energy.  Not sure what you mean.

#### Johann Mahne

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##### How was Absolute Zero discovered?
« Reply #111 on: 10/08/2011 15:44:58 »
Quote
To get nitrogen into the first vibrational excited state you have to add quite a lot of energy. As I said, it is the equivalent of getting it very hot.
To get it into the first excited electronic state you have to get it very hot- say 10,000 degrees.

Most nitrogen molecules at normal temps only have rotational and translational energy.

Thanks very much.That is actually quite amazing!
What kind of speeds and rotations do you get?
What happens with helium and hydrogen?
« Last Edit: 10/08/2011 16:46:34 by Johann Mahne »

#### yor_on

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##### How was Absolute Zero discovered?
« Reply #112 on: 10/08/2011 16:47:52 »
Planck scale is the smallest definable quantities we have. Beyond that you find a lot of absurdities and infinities, making no sense to us Imatfaal. "Planck units may sometimes be semi-humorously referred to by physicists as "God's units". They eliminate anthropocentric arbitrariness from the system of units: some physicists argue that communication with extraterrestrial intelligence would have to use such a system of units to make common reference to scale. Unlike the meter and second, which exist as fundamental units in the SI system for historical reasons (in human history), the Planck length and Planck time are conceptually linked at a fundamental physical level." Planck units. I'm surprised that you want to argue this?

As for arguing that time is reversible. No, it is not as far as I know, but in QM you can find processes that you can play forth and back being equivalent as I understands it. And you can also use it mathematically, but any process you observe JP, you observe under our macroscopic arrow, so as long as you don't want to argue that you observe 'time ticking' as some atmospheric strata being able to wander in different directions depending on 'size of observation' I would expect time to have only one direction.

As for time being a thermodynamic phenomena, thats a theory, or just a hypothesis as far as I know. My death though, is not.

#### yor_on

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##### How was Absolute Zero discovered?
« Reply #113 on: 10/08/2011 17:12:37 »
A simple way to define what time is under Einstein's definitions is to ask yourself if you think you will get a longer life measure by travelling close to light for an extended period of time.

Do you expect that to be true?

Why?

It's not, what you have is one measured life span, intrinsically the same no matter what you plan to do in form of travel etc. That the universe might die under that travel does not give you a longer life span. It's strange how many that miss that, assuming that because a relation might change they now have become 'immortal'. Time will 'tick' for you as long as you live, giving you the exact same treatment as if you had stayed at home. You might want to define it such as 'times arrow' do need some 'stuff' to exist, like a SpaceTime. Also that it have to be interactions following a linear chain of logic to make sense.

You living inside a thought up 'quantum computer' though, then 'time' as such has no meaning as everything already is 'there'. But if you're the operator of said quantum computer lifting out answers from it, then you live under a arrow.
==

If this how you think of it being thermo dynamical JP, you do have a point. But to me it's about interactions arranged in a logically explainable causality chain. And to be absolutely tru they do need to be experimentally defined and proven. Our macroscopic arrow is that. Any definitions discussing time reversibility under QM must be defined by observations under that arrow, and so I can see no possibility of proving that concept, other than as a mathematical equivalence of outcomes depending on how you play the movie. In reality, under those observations you really make though, 'times arrow' pointed only one way for anything you did and observed. if it didn't all definitions would become questionable and we would have to lift in new ways of defining 'clocks' as I see it.
« Last Edit: 10/08/2011 17:30:07 by yor_on »

#### JP

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##### How was Absolute Zero discovered?
« Reply #114 on: 10/08/2011 17:20:51 »
As for time being a thermodynamic phenomena, thats a theory, or just a hypothesis as far as I know.

But "it's just a theory" isn't a valid argument against a scientific theory.  Everything in science is "just a theory" on some level.

#### imatfaal

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##### How was Absolute Zero discovered?
« Reply #115 on: 10/08/2011 17:23:38 »
Planck scale is the smallest definable quantities we have. Beyond that you find a lot of absurdities and infinities, making no sense to us Imatfaal. "Planck units may sometimes be semi-humorously referred to by physicists as "God's units". They eliminate anthropocentric arbitrariness from the system of units: some physicists argue that communication with extraterrestrial intelligence would have to use such a system of units to make common reference to scale. Unlike the meter and second, which exist as fundamental units in the SI system for historical reasons (in human history), the Planck length and Planck time are conceptually linked at a fundamental physical level." Planck units. I'm surprised that you want to argue this?

If you had said beyond the planck scale- it would have made more sense, you said size so I was asking what you meant.  There are easily measurable objects that are below the planck mass - the planck scale is so highly energetic 10^27 eV because the planck mass is so big.  It is just not necessary to probe at the planck scale of energies to investigate ZPE.  To investigate at the planck scale requires such energy that quantum field theory breaks down - and as ZPE is an integral part of that you are not gonna have much joy.

#### yor_on

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##### How was Absolute Zero discovered?
« Reply #116 on: 10/08/2011 17:34:35 »
I don't know what you mean Imatfaal? You were the one questioning my definitions. Maybe you interpreted it differently than me? If so I hope you see what I mean now. And yes JP, I agree, everything is ultimately questionable, except some few things. My death is not, and so I will assume a arrow to exist, having a same 'ground state' in everything we can observe. That one has to be true.
==

As for me defining it as 'jiggling' :)
Something being in 'motion' relative you.

Entropy, does that have this definition, think about it :)
« Last Edit: 10/08/2011 17:42:21 by yor_on »

#### imatfaal

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##### How was Absolute Zero discovered?
« Reply #117 on: 10/08/2011 17:48:36 »
Yoron - you said we had to go beyond the planck size to probe ZPE .  The planck size is not a recognized term - it could mean either mass or length .  Thus it makes no sense because the planck length is unbelievably small  and the planck mass is actually quite a normal size (you can see a planck mass object with a decent magnifying glass).  Your second message moved onto the planck scale - now that is well defined - it is an energy scale at which photon have a mass equivalence energy of the planck mass, this is absolutely enormous.  Neither of these bear on the ZPE question.

On the jiggling - classical thermodynamical entropy certainly has that in the definition.  however the modern statistical mechanics definitions talks of the sum of probabilities over all possible microstates and involves neither temperature nor energy.
« Last Edit: 10/08/2011 17:58:28 by imatfaal »

#### yor_on

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##### How was Absolute Zero discovered?
« Reply #118 on: 10/08/2011 18:52:14 »
Well Imfatfaal. My definitions were not to your taste then :)
As for me using 'size', scale is about 'size' as I see it.

As for statistical definitions, I agree that those are very useful, but what I refer to when speaking of 'jiggling' is a single object. And I actually knew that already, so I'm not sure why you are mixing that with this?

#### Bored chemist

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##### How was Absolute Zero discovered?
« Reply #119 on: 10/08/2011 19:29:31 »
"Absolute zero is to my eyes where there can be no 'jiggling'. "
Perhaps, but to other people's eyes it's not that at all.
It's where everything is in the ground state.
The ground states are not stationary because, if they were, they would breach the uncertainty principle (in most cases).
However the ground states are perfectly accessible.
You keep breathing them.

Johann,
The speeds are roughly the speed of sound (which is why sound travels roughly that fast)
http://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution

The rotation rates are roughly speaking in the microwave region.
http://en.wikipedia.org/wiki/Rotational_spectroscopy

For what it's worth, the vibrational energy levels are in the infra red.
http://en.wikipedia.org/wiki/Infrared_spectroscopy

But if you want to talk about them it's probably best to find another thread.

#### yor_on

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##### How was Absolute Zero discovered?
« Reply #120 on: 10/08/2011 20:31:06 »
Yep, that's another way of defining it that makes sense. But I will stand with that to me 'absolute zero' is where there can be nothing happening, as observed by us. And also that this state is unreachable by us, much by the same reasons you give BC. And I define it as over 'Planck scale' being what belongs under our arrow. Outside that scale I don't think we have the right definitions yet, I mean, how could we? If it's not observable?

This universe is mighty strange.
==

Just as a bypass, sometimes I think of this universe as being only one thing, energy. And conservation of energy defines it as nothing gets really 'lost' in here, it just 'moves' into another 'position/state' whatever. Which means that all we ever do here is to shuffle energy :) from one 'position/state' to another. And that's also a weird thought, isn't it?
« Last Edit: 10/08/2011 20:51:52 by yor_on »

#### JP

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##### How was Absolute Zero discovered?
« Reply #121 on: 10/08/2011 20:53:21 »
Yep, that's another way of defining it that makes sense. But I will stand with that to me 'absolute zero' is where there can be nothing happening, as observed by us.

BC's definition isn't "another way of defining it," it's the actual definition.

#### Bored chemist

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##### How was Absolute Zero discovered?
« Reply #122 on: 10/08/2011 21:45:52 »
"But I will stand with that to me 'absolute zero' is where there can be nothing happening,"

FFS! Why?
Why do you persist with a definition that makes no sense- for example, it fails to explain the freezing of helium.

"as observed by us."
I presume that's the "Royal We" because nobody else here is claiming to have seen absolute zero.

#### yor_on

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##### How was Absolute Zero discovered?
« Reply #123 on: 12/08/2011 13:17:14 »
BC humor is not needed for this:)
As for the 'we' it's the way I write it, take it or leave it.

And absolute zero will be a state of no motion to me, whether you like it or not.
That simple.

#### yor_on

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##### How was Absolute Zero discovered?
« Reply #124 on: 12/08/2011 13:54:55 »
We can formulate it two ways. Assuming that motion exist then I will define Absolute zero as where that motion cease. That is what sometimes seem to be called a 'classical approach'. Then we have HUP Heisenberg's Uncertainty Principle where we find that if applied to the definition of absolute zero there still will exist an uncertainty, making it possible to define it as the 'vibrational energy' of whatever kind, still must have an existence. But that's, to me that is, also a measure of something 'fluctuating' under Planck scale. And to prove your thesis here you will have to probe that 'state' of absolute zero, interacting with it, and so transferring 'new energy'  to it. Which doesn't mean that I expect this definition to be wrong, just that to me it's also a function of time, as I wrote earlier, above. And time and its arrow is one of the most fundamental things we have in this cosmos, doesn't really matter if you're observing QM systems or macroscopic. You're still doing inside this arrow doing so, and all conclusions you draw is a function of what you see under that arrow. The laws of thermodynamics state that absolute zero can't be reached as I understands it?

Anyway, when I define it as no motion I'm doing it in from a classical approach. When it comes to QM oscillators at 'absolute zero' I assume the same as you BC, that there still will be a possibility of 'energy' according to HUP, but both assumptions fails in that there is no way we can probe this situation, as far as I know it's an unattainable proposition to ever reach 'absolute zero'. And that's also why I'm as free as you in defining it my way, it's after all a state that doesn't 'exist' to us, experimentally.

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##### How was Absolute Zero discovered?
« Reply #124 on: 12/08/2011 13:54:55 »