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Matthias
2008-Oct-28, 10:23 PM
What are the gravitational effects of quantum foam on light and matter across astronomical distances?

alainprice
2008-Oct-28, 10:39 PM
Don't mean to ruin your thread, but for some reason I was thinking of a club filled with foam(suds) and about to joke about opposite sexes mutually attracting.

Now back to our regular programming...

Excellent question, by the way. I'll be lurking.

PraedSt
2008-Oct-28, 10:41 PM
Yeah, me too. I hardly know what quantum foam is.

alainprice
2008-Oct-28, 10:43 PM
The quantum foam is a sea of virtual particles popping in and out of existence. It basically means that empty space is not empty, but you have to be looking VERY closely to notice.

An electron here, a positron there, and then they annihilate without a bang. Same goes for all families of particles.

PraedSt
2008-Oct-28, 11:14 PM
Ah, I see. So any effect would be small? Which is why the OP is about astronomical distances...ok.
Quantum foam is a real phenomenon I take it? And by that I mean observed and mainstream...?

mugaliens
2008-Oct-28, 11:31 PM
Yeah, me too. I hardly know what quantum foam is.

It's the froth on a head of Quark root beer.

No, wait...

It's what alainprice said.


What are the gravitational effects of quantum foam on light and matter across astronomical distances?

Your question is dead on target. The problem is, we don't know, as we don't have a good theory of quantum gravity. Quantum foam is real, and has been measured, via the Casimir effect, which increases as the distance between uncharged parallel plates decreases. The effect is approximately 1 bar when the plates are 10 nm apart, and results from the presence of conducting metals and dielectrics altering the vacuum expectation value of the energy of the second quantized electromagnetic field. In short, the shapes and positions of conductors and dielectrics determines the quantum energy field around them, resulting in, due to Heizenberg's uncertainty principle, fewer appearances of virtual particles in the quantum foam between to plates narrowly separated than on the outside of the plates.

The rest is sheer conjecture on my part: These particle apparitions may constitute the missing matter, and they're presence may be what defines light's constant, c. But both may also merely be a reflection of an as yet unknown factor.

PraedSt
2008-Oct-28, 11:39 PM
Lurking paid off. Thanks Mugs!

mugaliens
2008-Oct-29, 12:02 AM
Lurking paid off. Thanks Mugs!

Any time. Actually, I tripped over a funny bone and accidentally landed on my serious side.

Ouch!

PraedSt
2008-Oct-29, 12:05 AM
Any time. Actually, I tripped over a funny bone and accidentally landed on my serious side.

I noticed.

The effect is approximately 1 bar when the plates are 10 nm apart, and results from the presence of conducting metals and dielectrics altering the vacuum expectation value of the energy of the second quantized electromagnetic field.

:D

Cougar
2008-Oct-29, 02:34 AM
The quantum foam is a sea of virtual particles popping in and out of existence. It basically means that empty space is not empty, but you have to be looking VERY closely to notice.

I don't think that is quite right. Yes, the virtual particles play a role, but quantum foam is more a quality of spacetime - the turbulent, shifting fabric of the universe that allows virtual particles their brief existence.

As they explain it at the cafe (http://www.astronomycafe.net/qadir/ask/a11792.html), space-time itself is subject to the kinds of uncertainty required by quantum systems. This indeterminacy means that you cannot know with infinite precision BOTH the geometry of space-time, and the rate of change of the space-time geometry, in direct analogy with Heisenberg's Uncertainty Principle for quantum systems.

Cougar
2008-Oct-29, 01:41 PM
As to the OP....


What are the gravitational effects of quantum foam on light and matter across astronomical distances?

That is a good question. Somehow, physicists find a change of sign in the "energy of the vacuum" and attribute to it the repulsive effect of the accelerating expansion (resulting in the famous overestimation by 120 orders of magnitude). But vacuum energy also has positive gravitational effect, and in this case, there is a lot of it, amounting to ~70% of the mass-energy in the universe, which is enough to flatten spacetime. Does this also account for the dark matter? Apparently not, since dark matter "hangs" with mass conglomerations, but spacetime foam is everywhere.

mugaliens
2008-Oct-29, 06:28 PM
...since dark matter "hangs" with mass conglomerations, but spacetime foam is everywhere.

It's presence is, certainly. But what about it's magnitude? Do we have any empirical evidense which suggests that quantum foam is isotropic and not dependant (variably speaking) on the local gravitational gradient or gravimetric strain?

trinitree88
2008-Oct-29, 08:12 PM
I don't think that is quite right. Yes, the virtual particles play a role, but quantum foam is more a quality of spacetime - the turbulent, shifting fabric of the universe that allows virtual particles their brief existence.

As they explain it at the cafe (http://www.astronomycafe.net/qadir/ask/a11792.html), space-time itself is subject to the kinds of uncertainty required by quantum systems. This indeterminacy means that you cannot know with infinite precision BOTH the geometry of space-time, and the rate of change of the space-time geometry, in direct analogy with Heisenberg's Uncertainty Principle for quantum systems.

Cougar, Mugs...I'm glad the cafe link says that there is at present no evidence that quantum foam exists, other than in the original premise by Wheeler.
The exchange of virtual particles in the models of the other three fields, strong, electromagnetic and weak, on the other hand works pretty well, and when sufficient energy is applied to the members of these interactions, the virtual particles are promoted into the real world, indicating that the model has some merit to it.
The scale at which quantum foam might exist may be beyond our experimental capabilities, and may forever be only the topic of discussions.

BigDon
2008-Oct-29, 09:08 PM
Cougar, Mugs...I'm glad the cafe link says that there is at present no evidence that quantum foam exists, other than in the original premise by Wheeler.
The exchange of virtual particles in the models of the other three fields, strong, electromagnetic and weak, on the other hand works pretty well, and when sufficient energy is applied to the members of these interactions, the virtual particles are promoted into the real world, indicating that the model has some merit to it.
The scale at which quantum foam might exist may be beyond our experimental capabilities, and may forever be only the topic of discussions.

So something horrifically energetic like a core collapse supernova or a neutron star merger should produce "lots" of virtual particles made real?

Cougar
2008-Oct-30, 01:31 AM
It's presence is, certainly. But what about it's magnitude? Do we have any empirical evidense which suggests that quantum foam is isotropic and not dependant (variably speaking) on the local gravitational gradient or gravimetric strain?

Let me take a spin in my new intergalactic craft, and I'll check. :)

Right, it's pretty much strictly theoretical, but there certainly are areas of physics and cosmology that need theories :o , dark energy being one....

trinitree88
2008-Oct-31, 12:22 AM
So something horrifically energetic like a core collapse supernova or a neutron star merger should produce "lots" of virtual particles made real?

BigDon. Yes. At low temperatures, electric discharge through a gas..(say neon) promotes the virtual photons that exchange the electromagnetic force between the neon nucleus and it's surrounding electron cloud into reality, and they appear when the bartender turns on the neon light that says"Beer" in the window. Some few- tens of ev's per photon.
At more energetic temperatures, the pions shuttling the Yukawa model of the strong force, between nucleons are promoted into reality when an accelerator lab turns a beam of electrons/protons towards a target. Some hundreds of millions of ev's per pion...~200-300 Mev's.
More energetic collisions, billions of ev's, or Gev's yields the weak force carriers, the W+, W-, and the Z0, around 88-90 Gev's. Fermilab/CERN/DESY, etc...
Supernovae are the Scandanavian smorgasbord of them all, which is why the variability of the composition of the progenitors at touch-off, makes it tricky to model the interior dynamics correctly.
Since beer came up in the Mars thread today, it plays a role here. :shifty:If you climb to the top of Everest, or K2, and pop a bottle of beer, you might be the first human to see a Higg's boson trail as a cosmic ray secondary smashes through it just as the gas phase equilibrium is disturbed (and people will think you disturbed...:lol:)...that's how Donald Glaser invented the hydrogen bubble chamber...watching his beer. Have a cold one on me. pete

BigDon
2008-Oct-31, 03:21 PM
Mr. Tree, your post has given me a lot of homework.

pions, Yukawa model being two off the bat...

And I have to go find that Mars/beer thread.

Thank you.