Proof for virtual particles... ?

[rrw4rusty]

Hi!

 

I read somewhere that two metal plates were placed parallel to each other and that after time these two plates moved slowly closer together. This test supposedly proved the existence of virtual particle pairs. Supposedly it was the pressure of the virtual particle pairs that was causing the plates to move closer together.

 

Does anyone know what I'm talking about?

 

If not I'll dig it up.

 

At any rate this test always bothered me and it came to me why? Wouldn't gravity pull these two plates closer?

 

Thanks,

Rusty

[iNow]

Look into the Casimir effect.

[Bob_for_short]

It is quite similar to attraction (or interaction) of distant neutral atoms, a la van der Waals force. Gravity effect is too weak.

[rrw4rusty]

It is quite similar to attraction (or interaction) of distant neutral atoms, a la van der Waals force. Gravity effect is too weak.

 

Thanks for replying!

 

So gravity is too weak to pull the plates together and so it was figured that it must be the virtual particle pairs popping in and out of existence that was pushing the plates together -- I guess some slight energy discharge of the VPPs leave behind? And there are less between the plates so that's why they are pushed together?

 

It seems a bit strange to jump to the conclusion that the movement was caused by VPPs which are kind of far out there (if you weren't already convinced by education that they were there) doesn't it?

 

Rusty

[Bob_for_short]

In fact, what is usually said about the Casimir effect is not virtual pairs (electron-positron pairs) but virtual photons or the "zero-point energy" of the virtual photons. Casimir first predicted this effect and later on they measured that force.

The strict understanding of this effect is a long-distance interaction of neutralized charges. It is their potential energy that is calculated and its gradient determines the force.

 

You know, it QM the charges are "smeared" quantum mechanically, they are not point-like, so their interaction is somewhat different from pure point-like particle interaction. In addition, there is the quantized electromagnetic field "hooked" at each charge that gives an additional smearing. For neutralized distant charges this additional force dominates.

Edited October 28, 2009 by Bob_for_short

[Baby Astronaut]

So gravity is too weak to pull the plates together and so it was figured that it must be the virtual particle pairs popping in and out of existence that was pushing the plates together --

Makes sense except...what about the other forces, all stronger than gravity -- doing the pulling instead?

[rrw4rusty]

Makes sense except...what about the other forces, all stronger than gravity -- doing the pulling instead?

 

I'm glad you took some time to think about it before replying, LOL.

 

I'm not at all sure, you'd have to ask the scientists who performed the test and I don't remember off hand who it was or where I read about it. My impression was that the other forces could not come into play in the situation they had set up. My impression is that there is not much doubt about the virtual particle pairs appearing out of nothing and returning just as quickly.

 

To me this seems like radiation from parallel universes, many worlds or other mem'branes' but that's just my own very unscientific impression.

 

Rusty

[swansont]

Makes sense except...what about the other forces, all stronger than gravity -- doing the pulling instead?

 

Stronger than gravity but short-ranged, so they cannot account for the effect. It must be electromagnetic in origin.

[Baby Astronaut]

Stronger than gravity but short-ranged, so they cannot account for the effect. It must be electromagnetic in origin.

Wow, I didn't realize the such vast difference between a few micrometers and the (less than) 1 femtometer range of distance.

[froarty]

It is quite similar to attraction (or interaction) of distant neutral atoms, a la van der Waals force. Gravity effect is too weak.

Are you sure the gravitational force is too small? I certainly agree the g force of a single plate is too small or even 2 point charges at that spacing would be too small but do we really know what happens when the gravitational field of both plates merge as the plate spacing approaches zero. Could these weak forces accumulate into a venturii like force between the ambient field outside the plates and a depleted field inside?

[Bob_for_short]

The static gravitational attraction of the plates was calculated and found to be negligible.

 

If you speak of gravitational vacuum fluctuations, their contribution cannot exceed the electromagnetic contribution because of too weak coupling constant involved.