Re: Anti-matter

[Dennis.E.Krause@williams.edu (Dennis Krause)]

> > I'm not aware of experimental evidenve of the gravitational properties
> > of antimatter.  Since gravity is so weak this is a very hard experiment
> > to do.   Has it been done and I missed it?  Until experiment speaks,
> > theorists must remind themselves, they really know nothing about
> > the gravitational properties of antimatter.  Nature is under no constraint
> > to be the way we imagine it should be.
>
> Well, there is some evidence. Some particles are their own
> antiparticles. One of these, the photon, seems to have
> something like a positive gravitational mass. I believe many
> physicists would be very surprised to find antiparticles
> with negative gravitational mass.
>
> Leigh

In addition, Schiff gave an argument back in the late '50s in which the
gravitational effects of antimatter could be seen in ordinary matter.  For
example, different objects have different fractions of their masses arising
from binding energy, which has contributions due to the exchange of virtual
particles and antiparticles.  If gravity coupled significantly differently
to antimatter, composition-dependent effects would appear in tests of the
equivalence principle.

                                        Dennis


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