How was Absolute Zero discovered?

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Offline yor_on

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How was Absolute Zero discovered?
« Reply #50 on: 03/08/2011 04:14:47 »
If we assume that gravity is connected to energy, then if you empty 'space' of its energy there should be no gravity, without its metric I would expect 'space' to cease to exist, as far as we are concerned, and is able to measure. Also the Heisenberg Uncertainty Principle forbids it
=
heh FTL.

Just empty 'space' of its energy, then refill as needed, behind your 'propagation' :)
And remember, forgetting this you might just 'run out of space'
« Last Edit: 03/08/2011 04:21:28 by yor_on »
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Offline JP

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How was Absolute Zero discovered?
« Reply #51 on: 03/08/2011 04:25:53 »
Yor_on, each cell of space should have a ZPE associated with it.  This is what gives rise to the casimir force, in theory.  The ZPE allowed between two nearby conducting plates is less than outside, so there's a pressure.  As for gravity, ZPE is a quantum effect and there is no quantum theory of gravity, so who knows!

Mr. Data, you're confusing ZPE of a single state with T=0, which is only meaningful for many particles.  Certainly you can't reach T=0, which would mean putting all particles in a many-particle system in their ZPE states at the same time.   But some of those particles will be at ZPE without violating any physical laws.  It's kind of like rolling millions of dice.  You'll never get them all to come up 1's, but some of them certainly will in any given roll...

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Offline syhprum

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How was Absolute Zero discovered?
« Reply #52 on: 03/08/2011 05:25:30 »
You will certainly get all ones rolling your millions of dice, all ones is no less probable then any other number but you will have to be patient it will take a lot of rolls!
syhprum

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Offline JP

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How was Absolute Zero discovered?
« Reply #53 on: 03/08/2011 05:29:14 »
You will certainly get all ones rolling your millions of dice, all ones is no less probable then any other number but you will have to be patient it will take a lot of rolls!

Sure you can, if you're immortal.

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Offline Mr. Data

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How was Absolute Zero discovered?
« Reply #54 on: 03/08/2011 05:55:08 »
Yor_on, each cell of space should have a ZPE associated with it.  This is what gives rise to the casimir force, in theory.  The ZPE allowed between two nearby conducting plates is less than outside, so there's a pressure.  As for gravity, ZPE is a quantum effect and there is no quantum theory of gravity, so who knows!

Mr. Data, you're confusing ZPE of a single state with T=0, which is only meaningful for many particles.  Certainly you can't reach T=0, which would mean putting all particles in a many-particle system in their ZPE states at the same time.   But some of those particles will be at ZPE without violating any physical laws.  It's kind of like rolling millions of dice.  You'll never get them all to come up 1's, but some of them certainly will in any given roll...

Well, fundamentally-speaking, this is all that counts. You can measure the mass of the universe in a single proton!

What do you mean, some of those particles will have ZPE without violating any laws? You do understand yourself that you surely that ZPE by definition is a system which is at T=0. These are by another name ''absolute temperatures''. Nothing can reach this. If it was T=0 then it must violate the Uncertainty Principle. NOT even a collection of particles, with a small sum of them will reach T=0. None of them by definition have actually reached zero temperatures.


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Offline Bored chemist

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How was Absolute Zero discovered?
« Reply #55 on: 03/08/2011 06:55:10 »
Bored, you said ZPE would still be presentt if I did remove all energy from a peice of spacetime, but I think this is a speculation at best, since there is no experimental evidence to varify that. As I said, you cannot make a bit of spacetime suit the idea of an ''empty space'' - all of it is filled with quantum fluctuations.
Another strawman.
I never said anything about removing energy from spacetime. I asked about removing it from a nitrogen molecule.
The fact that you have to keep saying things that I didn't is very telling.
 
You seem steadfast in your decision not to address the evidence so, for the third time of asking,
why doesn't helium freeze unless you  apply about 25 bar pressure?

All the textbooks say it's down to ZPE. What's your explanation?

« Last Edit: 03/08/2011 07:04:20 by Bored chemist »
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Offline Mr. Data

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How was Absolute Zero discovered?
« Reply #56 on: 03/08/2011 07:26:45 »
Indeed I remain steadfast - now you ask me this in the appearance of a question.

You seem steadfast in your decision not to address the evidence so, for the third time of asking,
why doesn't helium freeze unless you  apply about 25 bar pressure?

All the textbooks say it's down to ZPE. What's your explanation?


If zero point energy, is by definition:

where ''zero-point'' refers to the energy of the system at temperature T=0, or the lowest quantized energy level of a quantum mechanical system.

(From your link by calphysics) - then my explanation is more logical; that being systems have energy close to T=0 but can never be T=0 (and T=0 being where zero point truely exists), then in this case the energy we are really dealing with is the intrinsic energy of the particle. Note then energy remains as a stubborn refusal to reach zero point because this would directly violate the UP - so temperature arises in systems due to obiding by this principle, also meaning that zero point temperatures have never really been reached.

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Offline yor_on

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How was Absolute Zero discovered?
« Reply #57 on: 03/08/2011 10:13:55 »
Well JP I've seen two definitions there. Either the 'Casimir force' belongs to matter itself, or to space. As for zero point energy, sure it exists, at least I expect it to do so. As for it needs absolute zero? That I don't think myself, if it did the Casimir effect should be a effect of the matter, not space, as at that 'energy scale' there can be no 'energy' 'jiggling' at all. And after all, explaining it in terms of frequency's/wavelengths presume something 'jiggling' as far as I can see? That's another way to look at the idea of absolute zero.

Or how would you define it, as something 'jiggling'? Then we have a ground state of energy where it won't be 'still', but fluctuating. You might argue that HUP takes care of that though, maybe? But then I doubt it to be a 'constant', and it should be, as I see it.
==

Simply expressed if you want zero point energy to 'fluctuate' or 'jiggle' at the same time you define it as being at absolute zero then I think you're wrong.
« Last Edit: 03/08/2011 10:18:41 by yor_on »
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Offline yor_on

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How was Absolute Zero discovered?
« Reply #58 on: 03/08/2011 10:32:26 »
Turn it around, if we define absolute zero as where nothing 'jiggles' then if we also define vacuum fluctuations to it I now will state that there must be a state beyond what we call 'absolute zero' in where what you see as the 'fluctuations' disappear, theoretically that is. Or we have to define it as there is no ground state of 'non moving' in which case the opposite definition of absolute zero loses all coherence.
« Last Edit: 03/08/2011 10:35:40 by yor_on »
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Offline yor_on

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How was Absolute Zero discovered?
« Reply #59 on: 03/08/2011 10:46:30 »
A third way to define it, that I like, is to place quantum fluctuations outside of Planck scale. Doing so we still have to explain how it can influence 'SpaceTime', but that becomes no stranger than how to define the 'expansion' we believe us to see. And placing it 'outside' all discussions about 'absolute zero' lose its relevance as we use temperature as definitions inside Planck scales, SpaceTime that is. To use it for something we won't be able to measure except third hand, so to speak, may make some sense theoretically as we want our ideas to stretch as far as possible. But if you look at Einstein's definition of gravity that pipe dream already has gone broke once, and will probably do it again.

I don't expect SpaceTime to adapt to our ideas, to me it's the other way around.
=

One might want to look at in terms of it not being the vacuum 'fluctuating' possibly? Instead, maybe, as a property of 'times arrow' fluctuating at very small scales, and that has to be a very weird idea, hasn't it :) But they all seem to come together at that plane to me.

So 'chopping it up', you end up with Planck scale, and that is the smallest measurable (not really measurable, but theoretically 'understandable') 'bits' we have, as I see it? So when you're at that scale everything will be 'frozen' to me, and from there you might argue that this is 'absolute zero', but then we also are on the threshold of reality, and as I said 'frozen in state'.

Beyond that there might be thygers :)
« Last Edit: 03/08/2011 11:06:00 by yor_on »
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Offline imatfaal

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How was Absolute Zero discovered?
« Reply #60 on: 03/08/2011 11:26:08 »
Turn it around, if we define absolute zero as where nothing 'jiggles' then if we also define vacuum fluctuations to it I now will state that there must be a state beyond what we call 'absolute zero' in where what you see as the 'fluctuations' disappear, theoretically that is. Or we have to define it as there is no ground state of 'non moving' in which case the opposite definition of absolute zero loses all coherence.

Nope - the realisation of Planck et al was that there is no point at which all fluctuations disappear - the lowest energy/ground state of any quantum oscillator is the zero-point energy (even at absolute zero the simplest system retains an energy of 1/2hν).  You are setting in opposition classical definitions and quantum mechanical ideas - and you will nearly always get a clash; you cannot slide seamlessly between the macro-scales of the macro-aggregation (that makes up temperature) to the micro-scales of quantum oscillations without a great deal of care.
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Offline Mr. Data

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How was Absolute Zero discovered?
« Reply #61 on: 03/08/2011 11:34:29 »
Let us not stray from the proposition being made. Zero point energy, the point at which motion should cease, does not. It is evidence enough to state that the definition of zero point energy is misunderstood.

It seems to be a strongly held belief that zero temperatures are reached, but there still remains a motion. This is an oxymoron.

Motion gives rise to temperature, so if there is no ceasing of motion, then how can your system really be called a zero point? In logical conclusion, zero point motion or temperatures (call it what you will) are never achieved.

If anyone can prove this wrong, I welcome them.

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Offline imatfaal

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How was Absolute Zero discovered?
« Reply #62 on: 03/08/2011 12:02:08 »
Mr D - you really need to understand that absolute zero and zero-point energy are not the same thing. 

The fact that zero-point energy is the energy remaining in a system at the limit T=0 does not logically imply, nor practically lead to the claim that zpe can only be observed at absolute zero.  ZPE is clearly demonstrated in the experimental world through many effects. Abs Zero is the theoretical limit where entropy is minimized and all oscillators within a system will be at zpe - this does not preclude a situation where some oscillators are at ground state and others are not. 

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It seems to be a strongly held belief that zero temperatures are reached, but there still remains a motion. This is an oxymoron.
I don't recall any post claiming that the limit T=0 can be reached.  But whilst we cannot practically reach it - we state with certainty that at T=0 there is still a ground-state oscillation ie the zero point energy.

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Motion gives rise to temperature, so if there is no ceasing of motion, then how can your system really be called a zero point?
It is called zero-point energy because i) it would still be there at T=0 ii) you cannot go any lower.

Quote
If anyone can prove this wrong, I welcome them.
Liquid helium will not solidify (unless pressurized) even as limit of T=0 is reached
http://en.wikipedia.org/wiki/Liquid_helium
Casimir plates feel a force
http://en.wikipedia.org/wiki/Casimir_effect
The lamb shift of energies of orbitals in hydrogen atom
http://en.wikipedia.org/wiki/Lamb_shift


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Offline Mr. Data

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How was Absolute Zero discovered?
« Reply #63 on: 03/08/2011 12:18:56 »

Mr D - you really need to understand that absolute zero and zero-point energy are not the same thing. 

I use zero temperatures, or absolute temperatures interchangeably.

http://en.wikipedia.org/wiki/Thermodynamic_temperature

The fact that zero-point energy is the energy remaining in a system at the limit T=0 does not logically imply, nor practically lead to the claim that zpe can only be observed at absolute zero.

Definition of the ZPE  -

''where ''zero-point'' refers to the energy of the system at temperature T=0, or the lowest quantized energy level of a quantum mechanical system.''

So it is stating that energy remains at T=0. You can use temperature interchangeably with energy or motion. As far as the definition is concerned, zero point energy is when temperatures are zero, and motion should no longer exist. It is entirely logical to assume that the zero point is not a factual temperature, since motion is never erradicated. So long as you have motion, your system cannot be said to be absolutely frozen, hence there is a temperature which cannot be quelled.

I don't recall any post claiming that the limit T=0 can be reached.  But whilst we cannot practically reach it - we state with certainty that at T=0 there is still a ground-state oscillation ie the zero point energy.

By what reasoning? If T=0 is never reached, how can speculations be given it is a true ground state? It seems outside the realm of testable physics.

It seems strange one can state with certainty that at T=0 there is still a ground state, if T=0 is never acheived.... think about it.

It is called zero-point energy because i) it would still be there at T=0 ii) you cannot go any lower.

Who says it would still be there, what evidence do you have that reaching T=0 reveals this prediction? Since we cannot reach the state T=0, then it seems redundant to make the speculation energy would still exist. Energy only exists because it cannot reach this state, not the other way around.

Liquid helium will not solidify (unless pressurized) even as limit of T=0 is reached
http://en.wikipedia.org/wiki/Liquid_helium
Casimir plates feel a force
http://en.wikipedia.org/wiki/Casimir_effect
The lamb shift of energies of orbitals in hydrogen atom
http://en.wikipedia.org/wiki/Lamb_shift


I don't see this as a proof. The articles will naturally not take into account the arguements I have given.


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Offline Mr. Data

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How was Absolute Zero discovered?
« Reply #64 on: 03/08/2011 12:20:50 »
Noting also:

''Absolute zero is the theoretical temperature'' - so absolute zero temperature is absolutely fine when speaking about the ZPE -

http://en.wikipedia.org/wiki/Absolute_zero

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Offline Mr. Data

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« Reply #65 on: 03/08/2011 12:22:39 »
The article is also the closest thing I would agree with, it states:

''A system at absolute zero still possesses quantum mechanical zero-point energy, the energy of its ground state. The kinetic energy of the ground state cannot be removed. However, in the classical interpretation it is zero and the thermal energy of matter vanishes.''

As I said, the energy left over is not really anything special in the sense it is a ZPE - it is merely a kinetic energy of our system which refuses to vanish. T=0 will not imply a freezing of the system, hence T=0 is never acheived.
« Last Edit: 03/08/2011 12:25:50 by Mr. Data »

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Johann Mahne

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How was Absolute Zero discovered?
« Reply #66 on: 03/08/2011 13:04:34 »
 This discussion is quite fascinating but I'm not a scientist so i'm not sure that i understand the implications of absolute zero and kinetic energy of molecules.
  We are told that the universe has an average temperature of 2.7 k.But now i'm confused.Does this average only apply to matter and not space itself?
 If a space probe measures the temperature in space somewhere between our local group of galaxies and the virgo group then what kinetic energy are we taking about? Photons have no mass so they cannot have any kinetic energy?The Cosmic Background radiation cannot have any kinetic energy either.Does this mean that it's not valid to speak of a temperature and that the space probe is returning only the temperature of it's probe?

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Offline Mr. Data

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« Reply #67 on: 03/08/2011 13:21:42 »
It has the homogenous appearance that the Background temperature is even to about 10,000th of an error. Quite a room for error.

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Offline Mr. Data

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« Reply #68 on: 03/08/2011 13:22:55 »
Anyway, mass does not imply kinetic energy. A mass does have a kinetic energy, but kinetic energy is simply the energy of a moving particle. So a photon is simply a packet of kinetic energy.

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Johann Mahne

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« Reply #69 on: 03/08/2011 13:29:58 »
So a photon has no mass but has kinetic energy?

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Offline Mr. Data

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« Reply #70 on: 03/08/2011 13:33:04 »
It might be more accurate to say that a photon is kinetic energy purely.

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Offline Mr. Data

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« Reply #71 on: 03/08/2011 13:33:23 »
But yes... no mass.

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Johann Mahne

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« Reply #72 on: 03/08/2011 13:42:52 »
Ok mr Data,i'll accept that.
  So you are saying the average temperature of the universe includes empty space itself?
 So what would the temperature read in the location i was speaking of?

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Offline Mr. Data

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« Reply #73 on: 03/08/2011 13:47:02 »
Careful my friend, there is no such thing as an empty space in physics. All of spacetime is occupied by quantum flucuations. Many of these flucuations only last a fraction of a second, but some are longer lived.

Anyway... temperature is valued in the cold of space where temperatures can vary to 10,000th degrees of an error. Since matter in the universe only occupies 1% of all spacetime, then it makes little justice to measure temperature in our daily acttivities. It makes more sense to measure temperatures in the deep of space where it is more or less homogenous.

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Johann Mahne

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« Reply #74 on: 03/08/2011 13:57:14 »
It seems as though you are saying that temperature is really kinetic energy,and that there is no place where there is no kinetic energy?Ok i'll accept that, since as you say radiation has kinetic energy.
 What do you mean by 10000th of a degree of error?
 What do you mean by quantum fluctuations in space,is this a theory only or has it been measured?
I agree that space cannot be empty as all space has radiation in it.I just meant space without molecules.

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Offline Mr. Data

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« Reply #75 on: 03/08/2011 14:03:53 »
It seems as though you are saying that temperature is really kinetic energy,and that there is no place where there is no kinetic energy?Ok i'll accept that, since as you say radiation has kinetic energy.
 What do you mean by 10000th of a degree of error?
 What do you mean by quantum fluctuations in space,is this a theory only or has it been measured?
I agree that space cannot be empty as all space has radiation in it.I just meant space without molecules.

By 10,000th of an error, this simply gives us a degree of freedom to allow certain parts of space to be slightly warmer than let us say the X-directionality. It is a smudge-factor.

Now, temperature can be thought of as a kinetic energy, or even the sum of the kinetic energy of the constituents of a macroscopic object. For instance, by theory it is said that a metal becomes hotter when the particles it is made of increase in kinetic energy. The faster they move, the hotter the object becomes.

As for quantum fluctuations, you may want to read this: http://arxiv.org/abs/gr-qc/0401082 - it is our best understanding of the vacuum in context of quantum mechanics.

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Johann Mahne

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« Reply #76 on: 03/08/2011 14:18:55 »
This is all detracting from the OP,but anyway...
 It seems as though the link you gave is saying that the fluctuations can add energy to particles (cosmic rays),but not detract from them?Seems strange to me because if a particle moves through a zone that has a lower energy then it should suck energy away from the particle.Do the fluctuations not average zero?Seems like perpetual motion?

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Offline JP

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« Reply #77 on: 03/08/2011 14:20:02 »
Well JP I've seen two definitions there. Either the 'Casimir force' belongs to matter itself, or to space. As for zero point energy, sure it exists, at least I expect it to do so. As for it needs absolute zero?

Yor_on, what is the meaning of defining absolute zero for a single particle?  Zero-point energy is meaningful and achievable for a single particle, temperature is not.

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Offline Mr. Data

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« Reply #78 on: 03/08/2011 14:30:48 »
Well JP I've seen two definitions there. Either the 'Casimir force' belongs to matter itself, or to space. As for zero point energy, sure it exists, at least I expect it to do so. As for it needs absolute zero?

Yor_on, what is the meaning of defining absolute zero for a single particle?  Zero-point energy is meaningful and achievable for a single particle, temperature is not.

Well, zero point energy for a particle would be a particle which ceases to exist strictly by the classical definition. Of course, quantum mechanics has something else to say. Even if T=0, a particle will still move. Indeed, large collections of particles will move. Speaking of one particle, is just as rewarding if not simpler than speaking or concentrating on a system with a large amount of particles.

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Offline Mr. Data

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« Reply #79 on: 03/08/2011 14:36:06 »
This is all detracting from the OP,but anyway...
 It seems as though the link you gave is saying that the fluctuations can add energy to particles (cosmic rays),but not detract from them?Seems strange to me because if a particle moves through a zone that has a lower energy then it should suck energy away from the particle.Do the fluctuations not average zero?Seems like perpetual motion?

Take out some qoutations which highlight your incongruities, and we can analyze them.

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Offline JP

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« Reply #80 on: 03/08/2011 14:45:10 »
Of course, quantum mechanics has something else to say. Even if T=0, a particle will still move. Indeed, large collections of particles will move. Speaking of one particle, is just as rewarding if not simpler than speaking or concentrating on a system with a large amount of particles.

Nope, you can't talk meaningfully about temperature of a single particle.  Temperature is defined for an ensemble of particles and it's properties (such as never reaching T=0) rely on the statistics of many particles.  That's where you keep going wrong when you say you can't reach T=0 for a single particle.  Such a phrase is meaningless. 

Here's a paper on reaching ZPE for a single molecule:
http://prl.aps.org/pdf/PRL/v62/i4/p403_1

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Offline Mr. Data

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« Reply #81 on: 03/08/2011 14:55:08 »
I don't know if I agree with you. Temperature is part of the equation which describes the ZPE for a single quantum oscillator:

ε = hv/(ehv/kT-1) + hv/2

If temperature cannot be defined for a single oscillator, how does it enter the equation?

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Offline JP

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« Reply #82 on: 03/08/2011 15:58:51 »
That's not the equation that described ZPE for a single quantum oscillator.  That's a thermodynamic equation for a collection of them.  The single quantum harmonic oscillator energy is:

E=(N+1/2)hbar*omega, where N=0,1,2,3,4,...

When N=0, you're at the ZPE, which has energy hbar*omega/2.

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Offline Mr. Data

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« Reply #83 on: 03/08/2011 16:09:16 »
Not according to this:

http://en.wikipedia.org/wiki/Zero-point_energy

''Then in 1913, using this formula as a basis, Albert Einstein and Otto Stern published a paper of great significance in which they suggested for the first time the existence of a residual energy that all oscillators have at absolute zero.''

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Offline Mr. Data

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« Reply #84 on: 03/08/2011 16:09:48 »
Or maybe I picked it up wrong...

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Offline Mr. Data

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« Reply #85 on: 03/08/2011 16:11:16 »
''the most famous such example of zero-point energy is E={\hbar\omega / 2} associated with the ground state of the quantum harmonic oscillator.''

From the same link. E={\hbar\omega / 2} is just the part of the remaining kinetic energy in the equation given.

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Offline imatfaal

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« Reply #86 on: 03/08/2011 16:13:21 »
Mr D - please learn to read your own sources before contradicting others.  We know you picked it up wrong.  Why are you persisting to try and "answer" these questions when it is quite clear that you haven't even read up to a wikipedia level?
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Offline Mr. Data

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« Reply #87 on: 03/08/2011 16:20:14 »
Mr D - please learn to read your own sources before contradicting others.  We know you picked it up wrong.  Why are you persisting to try and "answer" these questions when it is quite clear that you haven't even read up to a wikipedia level?

The speculations from the equations match those of JP's... after the equation given (which I presented) it simply states that

''According to this expression, an atomic system at absolute zero retains an energy of Ĺhν.''

Now, I don't see a great difference here. If you set N = hv/(ehv/kT -1) = 0 then you still end up with the same result.

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Offline Mr. Data

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How was Absolute Zero discovered?
« Reply #88 on: 03/08/2011 16:22:11 »
And I think it a bit sanctimonious of you to suddenly challenge my ability to read something. It's a common frequent thing here to see that kind of behaviour - we are all fallible, prone to mistakes. But I don't see you coming down on other people. Perhaps I left a mark with you?

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Offline imatfaal

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How was Absolute Zero discovered?
« Reply #89 on: 03/08/2011 16:27:51 »
This discussion is quite fascinating but I'm not a scientist so i'm not sure that i understand the implications of absolute zero and kinetic energy of molecules.
  We are told that the universe has an average temperature of 2.7 k.But now i'm confused.Does this average only apply to matter and not space itself?
 If a space probe measures the temperature in space somewhere between our local group of galaxies and the virgo group then what kinetic energy are we taking about? Photons have no mass so they cannot have any kinetic energy?The Cosmic Background radiation cannot have any kinetic energy either.Does this mean that it's not valid to speak of a temperature and that the space probe is returning only the temperature of it's probe?
Johann - the whole of the universe is full of thermal radiation (ie radiation given off by hot objects) that is a relic of three hundred years or so after the big bang.  This radiation, which when emitted by hot hydrogen ions was ultraviolet, has been stretched by the expanding universal so that it has been red-shifted to the microwave band.  All bodies above absolute zero will give off black body radiation - the spectrum they emit is related to the temperature of the the black body; the wavelength of the CMBR is that of a body at 2.75K.  

What that means is that any object colder that 2.75K will on average absorb radiation and warm up (ignore black holes they are weird) and any object warmer than 2.75K will on average emit radiation and cool down; ie the two systems will tend towards equilibrium.  As the entire universe is homogeneously full of this radiation it makes sense to talk of a temperature.  

A probe always measures the temperature of the probe - but we hope that by clever engineering we can ensure that the probe will be in equilibrium with the surroundings.  Other ways to measure temperature rely on the spectrum of radiation the object is emitting and use the black body equation to find the temperature.  
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Offline imatfaal

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How was Absolute Zero discovered?
« Reply #90 on: 03/08/2011 16:38:48 »
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Zero point energy is the zero point temperatures at which motion should cease to exist.
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Hence why a zero point energy (zero implying zero temperatures) is just nonesense.
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You are implying zero point energy is real; this would mean you can freeze your system to absolute temperatures!!!!! This is impossible!
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But in all cases, there is an energy and momentum associated to every particle in the universe, so by logical deduction, ZPE is non-existant.

The reason I have asked you to be more careful is the comments you have made so far in this thread - you will note they are in direct contradiction to what you are now seem to be agreeing with.
Thereís no sense in being precise when you donít even know what youíre talking about.  John Von Neumann

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Offline Mr. Data

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How was Absolute Zero discovered?
« Reply #91 on: 03/08/2011 16:39:59 »
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Zero point energy is the zero point temperatures at which motion should cease to exist.
Quote
Hence why a zero point energy (zero implying zero temperatures) is just nonesense.
Quote
You are implying zero point energy is real; this would mean you can freeze your system to absolute temperatures!!!!! This is impossible!
Quote
But in all cases, there is an energy and momentum associated to every particle in the universe, so by logical deduction, ZPE is non-existant.

The reason I have asked you to be more careful is the comments you have made so far in this thread - you will note they are in direct contradiction to what you are now seem to be agreeing with.

Elaborate. And note I will be away for the next hour or so, so make it good for my return.

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Offline JP

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How was Absolute Zero discovered?
« Reply #92 on: 03/08/2011 16:42:36 »
Now, I don't see a great difference here. If you set N = hv/(ehv/kT -1) = 0 then you still end up with the same result.

The derivation of the ZPE of a single quantum harmonic oscillator is here: http://en.wikipedia.org/wiki/Quantum_harmonic_oscillator

There is a huge difference because: 1) N is an integer for the harmonic oscillator, while N in your above equation isn't, and 2) these are completely different physical situations.  Yours is, from what I recall, an expression for the energy density of a black body radiator.  A quantum harmonic oscillator is completely different.

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Offline Mr. Data

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How was Absolute Zero discovered?
« Reply #93 on: 03/08/2011 16:42:54 »

Mr D - you really need to understand that absolute zero and zero-point energy are not the same thing. 

I use zero temperatures, or absolute temperatures interchangeably.

http://en.wikipedia.org/wiki/Thermodynamic_temperature

The fact that zero-point energy is the energy remaining in a system at the limit T=0 does not logically imply, nor practically lead to the claim that zpe can only be observed at absolute zero.

Definition of the ZPE  -

''where ''zero-point'' refers to the energy of the system at temperature T=0, or the lowest quantized energy level of a quantum mechanical system.''

So it is stating that energy remains at T=0. You can use temperature interchangeably with energy or motion. As far as the definition is concerned, zero point energy is when temperatures are zero, and motion should no longer exist. It is entirely logical to assume that the zero point is not a factual temperature, since motion is never erradicated. So long as you have motion, your system cannot be said to be absolutely frozen, hence there is a temperature which cannot be quelled.

I don't recall any post claiming that the limit T=0 can be reached.  But whilst we cannot practically reach it - we state with certainty that at T=0 there is still a ground-state oscillation ie the zero point energy.

By what reasoning? If T=0 is never reached, how can speculations be given it is a true ground state? It seems outside the realm of testable physics.

It seems strange one can state with certainty that at T=0 there is still a ground state, if T=0 is never acheived.... think about it.

It is called zero-point energy because i) it would still be there at T=0 ii) you cannot go any lower.

Who says it would still be there, what evidence do you have that reaching T=0 reveals this prediction? Since we cannot reach the state T=0, then it seems redundant to make the speculation energy would still exist. Energy only exists because it cannot reach this state, not the other way around.


Note you never answered any of this. I will also remind you of my conjecture:

Let us not stray from the proposition being made. Zero point energy, the point at which motion should cease, does not. It is evidence enough to state that the definition of zero point energy is misunderstood.

It seems to be a strongly held belief that zero temperatures are reached, but there still remains a motion. This is an oxymoron.

Motion gives rise to temperature, so if there is no ceasing of motion, then how can your system really be called a zero point? In logical conclusion, zero point motion or temperatures (call it what you will) are never achieved.

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Offline Mr. Data

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How was Absolute Zero discovered?
« Reply #94 on: 03/08/2011 16:43:44 »
Now, I don't see a great difference here. If you set N = hv/(ehv/kT -1) = 0 then you still end up with the same result.

The derivation of the ZPE of a single quantum harmonic oscillator is here: http://en.wikipedia.org/wiki/Quantum_harmonic_oscillator

There is a huge difference because: 1) N is an integer for the harmonic oscillator, while N in your above equation isn't, and 2) these are completely different physical situations.  Yours is, from what I recall, an expression for the energy density of a black body radiator.  A quantum harmonic oscillator is completely different.

Thank you for the link. I will take back what I said about the equation. I admit it is based on a flaw, an incorrect application.

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Offline JP

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How was Absolute Zero discovered?
« Reply #95 on: 03/08/2011 16:46:32 »
Quote
Zero point energy is the zero point temperatures at which motion should cease to exist.
Quote
Hence why a zero point energy (zero implying zero temperatures) is just nonesense.
Quote
You are implying zero point energy is real; this would mean you can freeze your system to absolute temperatures!!!!! This is impossible!
Quote
But in all cases, there is an energy and momentum associated to every particle in the universe, so by logical deduction, ZPE is non-existant.

The reason I have asked you to be more careful is the comments you have made so far in this thread - you will note they are in direct contradiction to what you are now seem to be agreeing with.

Elaborate. And note I will be away for the next hour or so, so make it good for my return.

Oh, you'll be away for more than an hour, I think, as this response makes it clear you don't have any desire to be civil on this forum: something you've been warned about in the past.

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Offline Bored chemist

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How was Absolute Zero discovered?
« Reply #96 on: 03/08/2011 20:48:10 »
You really do keep missing the point.

You say "It seems to be a strongly held belief that zero temperatures are reached, but there still remains a motion. This is an oxymoron."
Nope, it's the truth.

You can't remove the vibrational energy from a nitrogen molecule. It's not that you can't get it cold enough, it's that there is no lower energy state for it to be in.
The ground state is the lowest you can get. There's still energy associated with it.
Cooling it further doesn't make sense ( all you could do would be to reduce the fraction of molecules in any excited state.)

Once you get a nitrogen molecule into the vibrational ground state (as most of them are).
1 you cannot take any more vibrational energy out of it because, to do that you would have to move it to a lower energy state and, since it's in the ground state, there isn't one.
2 It will therefore stay in that ground state no matter how far you cool it (including, in principle, to zero)
Yet, because the ground state has a vibrational energy of about 0.15 eV, it still has quite a lot of energy. (Very roughly, the same energy as something glowing red hot)
That energy is the zero point energy of the system.
It's prefectly real.
It's the sort of thing that stops helium freezing unless you compress it.
« Last Edit: 03/08/2011 20:50:00 by Bored chemist »
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Offline Soul Surfer

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How was Absolute Zero discovered?
« Reply #97 on: 04/08/2011 23:47:59 »
BC one thing that this discussion shows how many people do not understand that we live in a dynamic universe and it is this residual vibrational energy that actually holds the atoms in molecules together.  Also this dynamic energy gets greater as you look further inside the atom the electrons in atoms have much greater energies corresponding to optical to x ray frequencies and the quarks inside the neucleons have so much energy that there is more energy in their motion than their rest masses.
Learn, create, test and tell
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Offline imatfaal

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How was Absolute Zero discovered?
« Reply #98 on: 05/08/2011 00:32:35 »
To an extent SoulSurfer - but the fact that the bound system has a lower energy than its constituent parts, ie that energy is needed to separate the stable system (the binding energy), does not logically entail the fact that the lowest energy is not zero.  In other words it is not obvious from the fact that energy is required to break either molecular or nuclear bonding that these systems must have a ground state that is not zero.  Strong bonds are the lowest energy state - not an energy rich state.  Whether you can make the connexion between vibrational energy and the quantum chromodynamic binding energy of quarks and gluons is beyond me - but it seems to be explaining non-classical matters in a far too classical a manner
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Offline Bored chemist

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How was Absolute Zero discovered?
« Reply #99 on: 05/08/2011 06:57:14 »
My personal opinion is that this thread largely shows that Mr data doesn't know what he is talking about to an extent that is verging on trolling.
I cite this excerpt as evidence for that opinion
"Let us not stray from the proposition being made. Zero point energy, the point at which motion should cease, does not. It is evidence enough to state that the definition of zero point energy is misunderstood.

It seems to be a strongly held belief that zero temperatures are reached, but there still remains a motion. This is an oxymoron.

Motion gives rise to temperature, so if there is no ceasing of motion, then how can your system really be called a zero point? In logical conclusion, zero point motion or temperatures (call it what you will) are never achieved."

Other evidence is plentiful, as cited by Imatfaal earlier

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