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---Begin Message---Jesse and George: the cobbler apprentice speaketh:## Advertising

you, mathematically high-minded savants look for a primitive realization of 'negative mass' etc, while you find it natural to use negative numbers. If I was 185lb last week and now 180 lb, then I have 5 lb in negative. Of course I cannot physically identify the 'missing mass', but mathematically it exists and I can calculate with it, speak about it, think about it: it 'exists'. Not " a piece of negaitive mass", of course. You got used to "how much is minus 2" as a POSITIVE value, it is a matter of habit-speak, it means: missing from the rest. "As compared to..." washed away in routine talk. I wouldn't look for something positive in negative. What you are missing is the language to fit it into any theory made up for poitive items. Imagine the confusion when the zero was invented. Does zero exist? (Ask Hal) Have a good day John Mikes --- Jesse Mazer <[EMAIL PROTECTED]> wrote: > George Levy wrote: > > > >Negative matter/energy however are different. If > negative matter/energy > >could exist they would give space a negative > curvature. > > The issue of negative curvature is somewhat separate > from negative mass, > though--if the density of matter/energy in our > universe was below the > critical density Omega, the universe would have > negative curvature, no need > for negative mass (see http://tinyurl.com/9ox67 ). > It might be true that > adding a certain density of negative mass/energy > would have the same effect > on spacetime curvature as subtracting the same > amount from the density of > positive mass/energy though, I'm not sure. > > >Negative matter/energy may be identical to dark > energy. > > I think dark energy has negative pressure (tension, > basically), but not > negative energy--see section 6 of the article at > http://tinyurl.com/8kepb , > the one titled "Negative Pressure". But the "Casimir > effect" that pulls two > parallel plates together (see > http://tinyurl.com/anoky ) might qualify as > negative energy--at least, the energy density > between the plates is lower > than the energy of the ground state of the quantum > vacuum, but whether this > would actually have the same effect as "negative > energy" in GR is probably > something physicists can't be sure of without a > theory of quantum gravity. > > Here's an article on negative mass/energy, and its > relevance to keeping > wormholes open in GR: > > http://www.physics.hku.hk/~tboyce/sf/topics/wormhole/wormhole.html > > Jesse > > >

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