Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jaiii on 18/03/2011 15:21:30
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Hi,
what happens when the conductive plates in Casimir phenomenon touches and make a short circuit?
Thank you.
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They do not form part of a circuit - so when they touch they are just a single conductor in free space
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Thank.
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There are no circuit there, maybe you could call it a 'suction'? It's not a pressure as that would imply that 'space' suddenly is 'measurable' as being 'something acting' which it is not.
Maybe you should just call it a imbalance on the 'virtual plane' created by matter enforcing its bonds, but it sure is weird :)
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There are no circuit there, maybe you could call it a 'suction'? It's not a pressure as that would imply that 'space' suddenly is 'measurable' as being 'something acting' which it is not.
You are dead right on one thing - it's weird. However one way of thinking about it is almost exactly as you said above was impossible. The suction is an absence of a pressure - we cannot measure background energy causes by quantum fluctuations (and when we try to calculate it the answers are hugely huge) - but we can provide an explanation for the Casimir effect by postulating its absence.
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Thank.
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Not for me Imatfaal. Neither suction or pressure is totally satisfactorily. An absence of possibilities is the closest I come to it, expressed as the Casimir effect. But it's about what definitions one use too. To me a space is a vacuum, it's not measurable in any reasonable way. That we have mathematical definitions for 'virtual thingies' fluctuating do not change that, and neither does the Casimir effect.
To me it's a description of two universes, meeting in the Casimir effect, as the 'observable' macroscopically. Or maybe 'emergences' interacting? But we live in one of them, not both, although they interact constantly.
But it sure is weird.
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Yoron - there are explanations for Casimir that rely on VdW forces (which of course was what the expriment was originally designed to investigate)
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Yep Imatfaal. Ah, I'm not saying that it is wrong too define it differently than me :)
Here's the difference between Casimir force and the Van der Waals force, as I understands it. "The London-van der Waals forces are related to the Casimir effect for dielectric media" (e.g materials with negligible electrical or thermal conductivity), "the former being the microscopic description of the latter bulk property". Those sentences cited I took from the wikis Van der Waals force. (http://en.wikipedia.org/wiki/Van_der_Waals_force) The last sentence is in fact an 'assumption' still, not anything proved as I know. I need to stop trusting in those Wiki's :)
The first detailed calculations of this were done in 1955 by E. M. Lifshitz, but he didn't succeed to explain sonoluminescence, where ultrasound waves exciting a liquid creates tiny bubbles, that then emits light as they collapse. And that he failed I understand as due to the way the Casimir force is directly coupled to the 'systems' geometry, becoming repulsive between two metal hemispheres.
That the Casimir effect is repulsive between two metal hemispheres do not agree with Casimir effect and Van der Waals forces being the same. There has been several different experiments after Schwinger, some of them agreeing with his proposal, other finding differences with his predictions larger by a magnitude of ten orders. So it has very much to do with how you set up your experiment, and your definitions it seems?
But a simple way of defining it as 'the 'exact' same' is to find a way to describe it where we all can agree that under those 'circumstances' it can be no doubt, as Einstein did when defining gravity as a constant acceleration (ignoring tidal forces).
Schwinger's idea was that as the size of those bubbles changed so would the magnitude of the 'zero point energy' do, intrinsic to the vacuum electromagnetic field, in this case meaning the 'field' not really there macroscopically, unless 'forced' into interaction by the Casimir force.
To me it has no real importance if they would be 'the same' as they, according to me, can't be :)
The only thing I dare to say about that is that the Van der Waals force possibly can be seen as an 'emergence' from the Casimir force? Gaining new properties as it express itself in matter. But that is the attraction with 'emergences', that they actually more or less expect new properties emerging in a transition e.g water becoming ice, gaining new weird properties from the transformation.
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Here is a nice description of it. What are van der Waals forces? (http://antoine.frostburg.edu/chem/senese/101/liquids/faq/h-bonding-vs-london-forces.shtml)
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Why they can't be is that I see a clear difference between 'vituality' and QM as 'particles' and then 'macroscopicallity'. And it's all about the 'arrow of time' and the way it expresses itself, or not.
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Thank veri much.