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Author Topic: How was Absolute Zero discovered?  (Read 45492 times)

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
 

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?
 

Offline yor_on

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How was Absolute Zero discovered?
« 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 :)
 

Offline Bored chemist

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How was Absolute Zero discovered?
« 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?
 

Offline yor_on

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How was Absolute Zero discovered?
« 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?
 

Offline Bored chemist

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How was Absolute Zero discovered?
« 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?
 

Offline yor_on

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How was Absolute Zero discovered?
« 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?
 

Offline JP

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How was Absolute Zero discovered?
« 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...
 

Offline yor_on

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How was Absolute Zero discovered?
« 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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Offline yor_on

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How was Absolute Zero discovered?
« Reply #134 on: 17/08/2011 00:44:09 »
Shrunk
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 »
 

Offline yor_on

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How was Absolute Zero discovered?
« 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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Offline Bored chemist

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How was Absolute Zero discovered?
« Reply #136 on: 17/08/2011 06:58:32 »
Shrunk


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.
 

Offline JP

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How was Absolute Zero discovered?
« 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.
 

Offline yor_on

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How was Absolute Zero discovered?
« 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 »
 

Offline JP

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How was Absolute Zero discovered?
« 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.
 

Offline yor_on

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How was Absolute Zero discovered?
« 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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Offline Bored chemist

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How was Absolute Zero discovered?
« Reply #141 on: 17/08/2011 19:26:47 »
Shrunk
"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?
 

Offline JP

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How was Absolute Zero discovered?
« 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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How was Absolute Zero discovered?
« 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?
 

Offline JP

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How was Absolute Zero discovered?
« 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 »
 

Offline yor_on

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How was Absolute Zero discovered?
« 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.

 

Offline Bored chemist

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How was Absolute Zero discovered?
« 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.
 

Offline Geezer

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How was Absolute Zero discovered?
« 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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How was Absolute Zero discovered?
« Reply #147 on: 21/08/2011 22:28:33 »

 

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