Rik van Riel <riel@nl.linux.org> writes:
> So it is established that there is a certain energy density in
> the vacuum? (it would seem so from your comments above and
> from various pieces of information that I've seen elsewhere)
Yes. In many quantum field models it is hard to even get a finite energy density in vacuum.
The Casimir effect shows the existence of some vacuum energy density (or demonstrates a negative energy density): if you put two conducting plates close to each other, there is an attractive force. The simplest explanation is that virtual particles with wavelengths longer than the gap become forbidden inside it, while they still can exist outside the gap - hence a "pressure" difference. Hmm, I probably mangled the physics there. Oh well...
> I believe this is the theory that the 0-point energy physics
> folks are busy with. No comments about the merits of those
> theories and/or experiments though because I don't know enough
> about that...
Neither do I, but I think they run afoul of the laws of thermodynamics when they try to extract energy from the 0-point energy.
> There's no reason to assume that it hasn't happened by now.
> Or that there are indeed slight variances in the background
> energy level in the universe (after all, the background
> radiation isn't completely equal in every direction)
If there were differences in background energy level, even very small ones, tremendous amounts of energy could be released by redistributing the vacuum - this isn't observed, it ought to be very visible. The background radiation seems to show that the matter in the early big bang was not quite homogenous, but it says little about the vacuum.
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