How was Absolute Zero discovered?

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Offline 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.

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Offline 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?
Kinetic energy released in radiation?

But if we do so, what would then then our virtual 'radiation' be?
A 'not radiation' :)
« Last Edit: 07/08/2011 17:51:11 by yor_on »
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Offline 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.
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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.

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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.

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Maybe we need to define it as collisions?
Kinetic energy released in radiation?
But if we do so, what would then then our virtual 'radiation' be?
A 'not radiation' :)
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.
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Offline 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.

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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.

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Offline 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.
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Johann Mahne

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How was Absolute Zero discovered?
« Reply #105 on: 09/08/2011 16:03:05 »
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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?

 

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Offline Bored chemist

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« 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.
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Offline 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.
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Offline 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.
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Offline 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. 

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Offline 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)

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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.
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Johann Mahne

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How was Absolute Zero discovered?
« Reply #111 on: 10/08/2011 15:44:58 »
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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 »

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Offline 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.
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Offline yor_on

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« 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 »
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Offline JP

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« 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. 

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Offline imatfaal

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« 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.

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Offline yor_on

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« 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 »
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Offline 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 »
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Offline yor_on

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« 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?
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Offline Bored chemist

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« 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)
There's more about it here
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.
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« 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 »
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Offline JP

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« 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.

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Offline Bored chemist

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« 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.
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Offline yor_on

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« 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.
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Offline yor_on

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« 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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Offline Bored chemist

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How was Absolute Zero discovered?
« Reply #125 on: 12/08/2011 17:58:43 »
And yet I can show you the effect of zero point energy at temperatures above absolute zero which are quite accessible to experimentation.

Removing the last of the vibrational energy from a nitrogen molecule should be easy (classically), yet it is, experimentally, impossible
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Offline yor_on

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How was Absolute Zero discovered?
« Reply #126 on: 12/08/2011 19:32:38 »
I'm talking about 'absolute zero' here, you're talking about 'zero point energy'. Are you defining it as they are the same BC?
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Offline yor_on

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« Reply #127 on: 12/08/2011 20:23:28 »
Let's put it on a understandable spectrum.

Assume that I ask you to measure the 'temperature' of vacuum fluctuations, could you do that? Not their secondary effects, but the actual 'fluctuations'? Not as I know. Why? Because they're out of our range of measuring. You are still free to interpret this as they could be inside Planck scale, although too 'small' to be measured by us, or as I do, assume that they actually is outside Planck scale, and therefore forever unmeasurable as I see it.

'Absolute zero' is to me a definition made from temperatures measured inside our SpaceTime. If you assume that there is a temperature scale, ending in 'zero' K, or whatever other type of measure you use, then my interpretation is that this stage can't be reached classically. As you say, from a classical point of view it should be reachable, but it's not, as proven in those experiments that tries to reach those states.

From a QM point of view there is always a uncertainty in the measurements and, loosely speaking here, the better you define one variable the more uncertain the rest becomes. So from that point of view you might assume that there is no such thing as a 'absolute zero'. And as thermodynamics needs 'temperature' to wander from hot to cold in a mixed system, you meet a paradox in that the last remains of 'heat' in that thought up system will need a colder than 'absolute zero' to wander to, making 'absolute zero' as a definition wrong, as it now would exist another 'colder' stage beyond that 'zero', if that would be possible.

Temperature is to me a classical definition, defined inside a arrow. Zero point energy (vacuum fluctuations) is something else, just as 'virtual particles'. The only thing I'm reasonably sure of it that we won't tap any energy from it. If that was possible I'm sure Nature already would have taken advantage of it. And there is no phenomena I know of that gains 'energy' from a classical 'nothing'. That is if we not are going to discuss how to see & define gravity :)
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Offline Bored chemist

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« Reply #128 on: 13/08/2011 00:26:40 »
"Let's put it on a understandable spectrum.

Assume that I ask you to measure the 'temperature' of vacuum fluctuations,"
Make up your mind.
Do you really think that vacuum fluctuations are more understandable than, for example, the vibrations of a nitrogen molecule?
It has already been pointed out that such minutiae don't actually help.
You seem to hold this odd idea that, at absolute zero, everything stops moving.
Do you realise that nobody else seems to think that way?
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Offline yor_on

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« Reply #129 on: 13/08/2011 21:20:08 »
I said classically, and you come on as increasingly rude BC?
Is that because you know that your way must be the only way?
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« Reply #130 on: 14/08/2011 11:11:08 »
I have asked why you persist in believing that absolute zero is defined by the absence of motion.
You have not answered that.
I also asked if you think that vacuum fluctuations are more readily understood than the vibrations of a nitrogen molecule.
Again, you have not seen fit to answer.

I asked about the freezing behaviour of helium.
Once again, I got not reply.

I have made it clear all along that the "way" I am describing is not "My way", but the orthodox way.
It falls to you to back your extraordinary claim with extraordinary evidence.
Instead you say I'm rude.

Perhaps you would care to explain why you think everyone else is wrong?
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« Reply #131 on: 16/08/2011 22:56:43 »
You are rude alright.

As for the rest of, you may think that you've asked those questions, but I didn't see it.
And comparing the theoretical behavior of 'vacuum fluctuations' to nitrogen molecules? As for me defining it as 'no motion'. It's my choice, not yours, and if you had read what I wrote you might have seen how I looked at it?  there are other definitions too, but classically I find it possible to define it as I do, as far as I'm concerned.

As for your behavior though.
Getting to be a 'thought police' are we?
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Offline JP

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« Reply #132 on: 16/08/2011 23:50:47 »
Yor_on, BC might not be terribly diplomatic, but he has a good point.  Coming up with a new definition of temperature isn't inventing a new physical theory.  Temperature is a tool for approximating values of things, and redefining it is breaking it's ability to make useful approximations.

Temperature is not a fundamental property of matter.  It's an average value (of kinetic energy) that's useful because when you're dealing with billions upon billions of particles, you can't hope to solve the equations of motion of each particle to describe how the system changes in time.  Instead, you write a theory in terms of average values, which is much easier.  This is essentially the entire point of temperature: it's the average kinetic energy you'd get if you solved the equations of motion for all the particles in your system, and therefore the definition of temperature and it's properties are derived from the equations of motion for those particles.

Dealing with sub-Planck length temperature effects is pointless, since there are no valid sub-Planck length equations of motion (yet).  As the laws of motion are extended to to sub-Planck lengths, temperature will follow.  But temperature can't go there first, since it's defined from the laws of motion.

The same goes for the arrow of time: fundamental laws of motion don't care about the arrow of time*, so temperature can't depend on them.  If you want to include the arrow of time in the definition of temperature, you first have to show that the fundamental laws of motion depend on it.

Absolute zero is also not a special, fundamental property of matter.  It's a name we have for the case where all the particles being averaged over are in their lowest possible energy states.  If you're averaging over classical mechanics, this means nothing is moving at all.  If you're averaging over quantum mechanics, there's the possibility that things are still moving, since the lowest possible energy for quantum particles is sometimes not actually zero-energy. 

Zero point energy, again, isn't anything special, nor it it related at all to the definition of temperature.  It's just the name for the lowest energy state of a quantum particle, which often has non-zero energy.

Again, to reiterate: temperature is a tool that's designed to simplify solving the equations of motion.  Temperature's definition will change as the laws of motion change, not the other way around.  If you change the definition of temperature without changing the laws of motion, then temperature becomes useless: it can't simplify your calculations anymore, and it is no longer related to the laws of motion or physics going on.

-------------

* With the possible exception of CPT violation...

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« Reply #133 on: 17/08/2011 00:43:09 »
"Definition of Absolute Zero

Absolute zero is the temperature at which all classical motion stops.


Although temperature has no maximum value, absolute zero, at 0 Kelvin (K) or -273.15 degrees Celsius (°C), is the lowest temperature possible. At this temperature, no energy can be transferred out to another body. A common misconception is that all motion stops at 0 K, but quantum mechanics states that some molecular motion must always exist, as having no motion whatsoever would violate the Heisenberg uncertainty principle. Even at 0 K the atoms in molecules continue to oscillate (atomic bonds stretch and contract), giving them a minimum non-zero amount of energy, called the zero-point energy. The coldest temperature ever achieved in a laboratory was 100 pK, or 0.0000000001 K."
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« Reply #134 on: 17/08/2011 00:44:09 »
And even if BC had been right it doesn't make being rude any better.

=

And as I said, there are several ways too see it. I look at it as where 'classically' all motion should cease, quantum mechanically as where Heisenberg's Uncertainty Principle rules.
==

Also, we will never reach absolute zero. And that is because of HUP, classically we might assume it a reachable state. But it isn't, so from that point of view I have no problems with it. But I still expect there to exist a state of no motion, even though then defined as some constituent of time.

Because to me it's all about time :)
« Last Edit: 17/08/2011 00:59:42 by yor_on »
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« Reply #135 on: 17/08/2011 01:43:58 »
Every experiment we do, we do under the arrow. Every definition we have we get from there. Does that mean that the arrow is a must? That there can be no state where the arrow disappear. We can't reach that state where our macroscopic arrow 'breaks down', but we assume that this might be possible at very small scales. Still, as long as you have a motion you must have a duration, you can't presume a motion without it. But if assuming no duration, then that also should be a state where noting 'moves'.

All as I see it. And that might be seen as my very own definition, but, it wasn't what we discussed with 'Absolute Zero', although it has a relevance to my thinking.
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« Reply #136 on: 17/08/2011 06:58:32 »


As for the rest of, you may think that you've asked those questions, but I didn't see it.


Getting to be a 'thought police' are we?

There is none so blind as him who will not see.
and I'm not the thought police; reality does that. If your ideas are wrong, reality makes it clear by, for example, not letting helium freeze at absolute zero.
I may be rude, but I'm in good company; it's not polite to simply ignore questions people put to you.
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Offline JP

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« Reply #137 on: 17/08/2011 12:23:25 »
Every experiment we do, we do under the arrow. Every definition we have we get from there. Does that mean that the arrow is a must? That there can be no state where the arrow disappear. We can't reach that state where our macroscopic arrow 'breaks down', but we assume that this might be possible at very small scales. Still, as long as you have a motion you must have a duration, you can't presume a motion without it. But if assuming no duration, then that also should be a state where noting 'moves'.

All as I see it. And that might be seen as my very own definition, but, it wasn't what we discussed with 'Absolute Zero', although it has a relevance to my thinking.

Well, you know, yor_on, we can't live in a state where we experience quantum effects first hand, but we know they exist.  We don't experience relativistic effects by flying in a spaceship at nearly the speed of light.  But by setting up careful experiments, we can find that these effects exist.  In the same way, we can check if the arrow of time is important for the laws of motion of particles, and it isn't!  Time is important, obviously, but there's no fundamental reason why time goes in one direction. 

Since temperature is based on these laws of motion, it doesn't depend on the arrow of time, either.  It can't, unless you invent new laws of motion which need the arrow. 

Anyway, from what you're describing now, it seems you agree with the mainstream definitions of temperature, ZPE and absolute zero.

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« Reply #138 on: 17/08/2011 14:35:29 »
That is the Quantum realm you discuss JP, as defined from macroscopically. Assume a stone rolling down a hill, there you have a 'process'. Now tell me if it's enough calling that process for the sole reason to the 'rolling downhill' or if we need something more to define it by. When people use definitions that's 'rolled up in themselves' more or less, thinking they describe the sole reason for there existing a arrow, then I think they're wrong.
==

It's as with everything else we see. We have definitions that works 'perfectly' inside SpaceTime. But we also seem to have something that's more or less 'unmeasurable'. And that you can look at as either existing 'inside' SpaceTime in some manner, although unmeasurable, or define it as being outside the borders that defines it (SpaceTime) to us, and by that I also mean what's measurable.

We use what we can measure to define what we can't. And that makes for some remarkable ideas.

But 'time' is duration. Without 'duration' you can't define it as a 'motion'. Statistically you may discuss it as a 'probable motion' but that's not a motion. That's a probability of motion, and it will be the arrow that defines if it was.

And ahem yes :) I'm discussing QM there, not relativistic effects from macroscopic viewpoints. But I agree that they still have a relevance for 'time' those definitions we use macroscopically. The question of what 'motion' really is for example, as in 'uniform motion'.

But we do assume that 'motion' exist. We also define from it distance and 'clocks'. The clocks use a linear causality chain that makes it possible for us to define a beginning, middle, and possible end, to what we observe. We also see that processes is reversible in some circumstances. From that we get an idea of 'time' being reversible. But macroscopically it never was, as any repeatable experiment will show you. Because if it was there would be no guarantee of their repeatability. So we ground our experiment on the assumption that repeatability is the key to what makes the cosmos 'tick', and so also a arrow.

Maybe 'time' is 'rolled up' in some manner, but it's not 'rolled up' in here. Here it seems a function of the room, and 'frames of reference', having one direction macroscopically.

« Last Edit: 17/08/2011 15:10:49 by yor_on »
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« Reply #139 on: 17/08/2011 15:12:39 »
Yor_on, you keep talking about your opinion of the definitions.  Your opinion happens to contradict experimental fact, which shows that microscopic interactions don't have a preferred arrow of time.  It doesn't matter that we as humans happen to always experience an arrow of time.  Part of modern science is learning how to do experiments that go beyond our everyday scales and viewpoints of the universe.  If we could only do experiments that are limited by our particular viewpoint of the universe, we'd not have relativity or quantum mechanics, since we generally don't directly experience either.

Your opinion isn't going to be valid science as long as it contradicts experimental evidence.

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« Reply #140 on: 17/08/2011 15:26:21 »
Well, I don't see where it 'contradicts'?
What I'm saying is that all definitions you use is grounded on assumptions, one of them is the arrow and repeatability.
==

I also pointed out that this is mine own view on it, didn't I?
=

Tell me JP, how can there be statistics without a defined arrow of time?
Isn't that a necessary presumption for it?

Or could you expect it possible to beget statistics without a arrow too?
« Last Edit: 17/08/2011 15:34:08 by yor_on »
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« Reply #141 on: 17/08/2011 19:26:47 »
"I also pointed out that this is mine own view on it, didn't I?"
Yes, and I repeatedly asked why you keep believing it.
Just so you don't miss it this time,

Why do you keep defining it in a way that doesn't make sense and which is at odds with reality?


Are you just trolling?
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Offline JP

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« Reply #142 on: 17/08/2011 20:18:24 »
Yor_on, this is the same thing we say to everyone posting new theories: you're welcome to your opinion, but it isn't science. 

I suggest you check out the laws of classical mechanics and quantum mechanics and convince yourself that there is no arrow of time in those cases:

Quote
By contrast, all physical processes occurring at the microscopic level, such as mechanics, do not pick out an arrow of time. Going forward in time, an atom might move to the left, whereas going backward in time the same atom might move to the right; the behavior of the atom is not qualitatively different in either case.
[ http://en.wikipedia.org/wiki/Entropy_(arrow_of_time) ]

You can argue all you want, but until you overturn the laws of classical and quantum mechanics, you're wrong about the arrow of time being fundamental.

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« Reply #143 on: 18/08/2011 09:32:32 »
Quote
You can argue all you want, but until you overturn the laws of classical and quantum mechanics
It seems as though the laws of classical mechanics are already overturned.
 Are there any that have survived quantum mechanics?

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Offline JP

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« Reply #144 on: 18/08/2011 10:30:22 »
Quote
You can argue all you want, but until you overturn the laws of classical and quantum mechanics
It seems as though the laws of classical mechanics are already overturned.
 Are there any that have survived quantum mechanics?


As I've said above, temperature is a tool used to predict average values of kinetic energy in some pre-existing model. So temperature doesn't tell you what you need in an underlying model.  The problem at hand places requirements on whether you use classical or quantum mechanics to model the situation.

There are times when classical mechanics works very well, so you don't need the more accurate quantum theory.  In these cases, a classical mechanical temperature definition is fine.  If you need to worry about quantum effects, you can base a temperature definition on quantum mechanics. 

There's always the tendency to say "but that theory isn't 100% accurate in all cases," which is true of every theory, since no theory describes everything in the universe perfectly accurately.  The trick in physics and engineering is to know which model is accurate to the case at hand.
« Last Edit: 18/08/2011 12:07:14 by JP »

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Offline yor_on

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« Reply #145 on: 21/08/2011 17:55:04 »
Well, it depends from where you look I would say. The best theory still is Einsteins relativity, in where time is a function of the room. As for the quality of BC:s comments?

Seems the standard is sinking here.

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Offline Bored chemist

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« Reply #146 on: 21/08/2011 21:41:48 »

Seems the standard is sinking here.
Too right. There was a time when someone who asked a question could reasonable expect an answer.
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« Reply #147 on: 21/08/2011 22:28:33 »
Okdoky!

Well, it looks like this horse has been well and truly flogged, so I think it's best to lock the thread for a bit.
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