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Jerry
Posted:
Mon Sep 12, 2005 1:28 pm
Joined: 04 Jun 2005
Posts: 9
Location: Australia
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I understand that all molecular movement is supposed to stop at absolute zero - no vibes=no energy.
What is theoretically happening to sub-molecular structures though? Is there no electron shell around a nucleus etc?
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Arthur Dent
Posted:
Mon Sep 12, 2005 2:55 pm
Joined: 26 Aug 2005
Posts: 7
Location: Ohio
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Absolute zero: Unobtainable
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Temperature is like most other measured things, reducing it is much like dividing it by half, you keep on doing it for as long as you like but you will never reach zero. I am sure though, that if you did reach absolute zero that the electrons would still orbit, because if they did not, they would fall into the nucleus.
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Jerry
Posted:
Tue Sep 13, 2005 8:46 am
Joined: 04 Jun 2005
Posts: 9
Location: Australia
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Thanks for that - I suppose I was really asking what was theorised to happen to sub molecular stuff at 0 Kelvin. Or rather, what is it that actually makes molecules vibrate in the first place - where does that energy come from? 
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Orion
Posted:
Tue Sep 13, 2005 7:07 pm
Joined: 08 Sep 2005
Posts: 9
Location: Va.
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| Quote: | | I suppose I was really asking what was theorised to happen to sub molecular stuff at 0 Kelvin. |
Absolute Zero--atoms and molecules will constantly vibrate anyway. This is described in quantum mechanics
as a consequence of the
Heisenberg Uncertainty Principle
and the power behind those vibrations is known as Virtual Energy
| Quote: | | Or rather, what is it that actually makes molecules vibrate in the first place - where does that energy come from? |
One form of energy is called "kinetic" and refers to something possessed by a moving mass. It takes effort (force) to cause a mass to move,and one definition of energy describes it as applying a force throughout some distance: Work equals Force multiplied by Distance. Thanks to Newton's First Law of Motion after putting that effort into moving something across a distance, it will keep going and going and going...until some other force is applied to it. Thus the motion of the object itself represents a kind of "stored" energy.
If we take the above, and examine atoms and molecules, then it is plain that when energy is applied to them, they will start to move. Next, since very often atoms and/or molecules are crowded together, few of them will move much, before colliding with their neighbors. And since atoms and molecules are generally pretty tough objects, they will usually bounce off each other, instead of shattering. From our macroscopic perspective, the tiny tiny motions of atoms and molecules bouncing off of each other can strongly resemble random vibrations...and the more energy those particles possess, the faster they will move and bounce.
The final part of this bouncing description involves the details of a bounce. Just like a rubber ball, an atom or molecule will deform from its usual shape during a collision. Since these particles are somewhat springy, the process of deforming them is akin to compressing a spring; energy is stored in the actual deformed shape. Afterwards, and before the next collision, that stored energy reshapes the atom or molecule. However, remember the First Law of Motion! The various parts of atom or molecule which are springily moved back towards their original configuration...will tend to keep moving!!! This leads to another deformation of the particle, even in the absence of a collision! And since another deformation means recompression of that springiness, it will naturally be followed by another movement back towards the original configuration.  .................................................Orion
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Jerry
Posted:
Thu Sep 15, 2005 2:24 pm
Joined: 04 Jun 2005
Posts: 9
Location: Australia
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Thanks for that Orion, all really helpful. Just confused on a point - the QM site thought that an atom would collapse at absolute zero, and electrons become virtual. Does that mean that Absolute Zero could never actually exist as a state?
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Orion
Posted:
Thu Sep 15, 2005 8:13 pm
Joined: 08 Sep 2005
Posts: 9
Location: Va.
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| Quote: | | Does that mean that Absolute Zero could never actually exist as a state? |
Sorry Jerry, I should have been more precise and said "*In Theory*, atoms and molecules will constantly vibrate anyway(at absolute zero)"
Although one can approach absolute zero as closely as one desires, one cannot actually reach this limit. The third law of thermodynamics, formulated by Walter Nernst and also known as the Nernst Heat Theorem, states that if one could reach absolute zero, all bodies would have the same entropy. In other words, a body at absolute zero could exist in only one possible state, which would possess a definite energy, called the zero-point energy which brings us back to Quantum Mechanics and the uncertainty principle. This state is defined as having zero entropy.
 Very interesting subject Jerry
Orion
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Jerry
Posted:
Fri Sep 16, 2005 6:06 am
Joined: 04 Jun 2005
Posts: 9
Location: Australia
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It is interesting – I wonder if this ‘non allowance’ of Absolute Zero has a direct bearing on the structure and mechanisms of the universe. As I understand it, the way the universe is expanding is a bit of a mystery in as much as Hubble’s observations reflect that some force or energy in the universe must act in the opposite way that gravity does and seems to act more strongly the further ‘out’ you look.
If the universe were thought of as being ‘sucked out’ into a void (at or very close to Absolute Zero) rather than ‘exploding’ into it, this could explain the increase in acceleration at the boundary of our observations. At the moment a Cosmological Constant, a gravitationally repulsive force, antigravity etc is required for theory and observation to agree.
Also, thinking of the expanding balloon model in representing the way the universe expands, it’s the potential energy held in the tension of the rubber that limits the rate of expansion. In any particular region of the surface the causal effects of the tension of the entire structure is represented.
So if there were ‘tension’ present in the boundary of our Universe (or Bubble, according to fractal views of the universe), could it be this that is actually dark matter? – or at least provides the mechanism by which dark matter is supposed to effect the universe’s expansion rate?
I also wonder if the mechanism that caused Inflation is connected with all this – back to the balloon for the moment – before the balloon has started to expand significantly, it’s resistance is at the highest it will be as it occupies the smallest volume it can (maximum [potential] energy density).
The tension in the rubber remains the same during expansion but is spread over an increasingly large area so it’s overall resistance to expansion decreases with time for the same energy input. So the balloon starts to expand a little (we all know this bit from using our lungs to do this) and a threshold is reached where suddenly it’s far easier to blow up, because we’re applying enough energy at a sufficient rate to finally overcome the resistance of the rubber.
Similarly, if our universe had inherent tension in its spacetime boundary just after the Big Bang and acted the same way for the same reasons as the balloon it would suddenly expand after reaching its threshold.
Then its tendency to continue expanding would be governed by the resistance of the boundary tension working against the vacuum into which it is expanding.
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