Please bear with me as I try to construct a question which goes well
beyond my area of knowledge. Back in the fifties, when C, P, and T
were thought to be independently robust symmetries of Nature, the
standard story was that electromagnetic radiation which originated
from a source consisting solely of antimatter would be
indistinguishable from electromagnetic radiation originating from
its koinomatter* symmetric dual. For this reason we cannot
determine the kind of matter which makes up the most distant
galaxies by optical spectroscopy and polarimetry on their light.
In the late fifties P was shown to be violated in the famous
experiment of Wu et al, as we've been reminded here. A decade later
T was shown to be independently unsymmetrical in Nature, and by the
"CPT theorem" (which, being a theorem, I assume is absolutely true)
C must, therefore, not be a symmetry of Nature. Please correct any
misconceptions that might be evident in what I've written. If C is
not a symmetry of Nature (or, more properly, Natural law) then is
there hope that one might observe the electromagnetic radiation from
distant galaxies and discern some distinctive difference due to the
type of matter of which the galaxy is composed?
It seems to me that the chirality of neutrinos might offer us a tool
better fitted for the purpose of distinguishing antimatter from
koinomatter at a distance. I expect that the neutrinos emitted in a
Type II (core collapse) supernova event would be thermal, and for
that reason relatively racemic**, like black body photons are. The
far less numerous neutrinos emitted in the subsequent decay of the
products of the supernova (especially Ni56 and Co57, both of which
decay by electron capture) should yield neutrinos of the same
matter type as the supernova, and hence of the galaxy in which it
resides, and, in turn, the cluster of galaxies in which that galaxy
resides.
Now, I know that neutrino astronomy is not, by many orders of
magnitude, capable of such an observation. What better ideas are
there for an observational way of telling the difference between
koinomatter and antimatter without actually bringing them into
physical contact?
Leigh
* I adopt Hannes Alfven's term for "ordinary matter".
** Michael will like that term, but it means "roughly equal numbers
of neutrinos of each chirality".