Julian Bradley <<In any case I'm not entirely sure of how far CPT
Conservation or symmetry is regarded now, see
http://en.wikipedia.org/wiki/CP_violation and elsewhere.>>
I fear that you may have posted the wrong link, Julian, because the
Wikipedia article to which you refer appears to consist entirely of
supporting evidence for CPT symmetry, which is fairly fundamental to
Physics, and has been for quite some time - ever since K-mesons were
observed to violate CP symmetry by decaying so as to favour the production
of matter over antimatter. IANAP.
<< The question is fairly simple in a way.
If you had 1 Kg of neutrons (no charge) and 1 Kg of electrons (all
negatively charged) would both give the same amount of energy through their
total destruction?>>
According to E=mc^2, obviously.
To destroy the neutrons, you could use 1Kg of anti-neutrons.
To destroy the electrons, you could use 1Kg of anti-electrons (positrons).
It is not possible to convert the neutrons to energy without cancelling
their parity, and it is not possible convert the electrons without
neutralising their electric charge, and their parity.
<<Incidentally off list an ex-physics graduate has suggested that
E=mc^2 is an approximation (for public consumption) and that the actual
equation does take into account other factors, like some of the energy,
including charge that might be associated with any specific mass.
This seemed perfectly plausible and sensible to me, but it does slightly
undermine the idea that the underlying truths of physics are both beautiful
and _simple_.>>
I don't understand how your ex-physics graduate goes about destroying
electric charge. Charge must be carried by a particle, and that particle
must have a mass.
The underlying truth of special relativity is that distance and time are not
observed to be constant for all inertial observers, but that the speed of
light is. E=mc^2 is a consequence of special relativity rather that a
definition of it.
Your ex-physics graduate may have been referring to other conservation laws
than the conservation of energy - the conservation of momentum, for example.
In which case, an example of the over-simplification being referred to is
that even though a gamma ray photon, produced by the annihilation of an
electron and a positron has no mass, it still carries the net momentum of
the original electron and positron.
You can find out more by looking up the Physical Properties of Photons in
Wikipedia.
-Paul
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