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Re: energy, work, heat



Leigh,

You are certainly correct in claiming that energy and momentum
are not conserved (locally or globally) as measured in accelerated
reference frames. This is indeed a difference between energy
and charge (for example). Whether this makes energy "insubstantial"
depends on your definition of "substance"; my intuitive notion of
substance is closer to mass than it is to charge or even to number
of particles. My intuition also tells me that lots of strange things
are going to happen in accelerated reference frames.

On the other hand, I don't understand all your nitpicking about
local conservation of nongravitational energy-momentum. This is
an extremely important physical principle, whatever one wants to
call it. In tensor notation it's written D_mu T^munu = 0.
In a locally inertial frame with cartesian coordinates this
says d_mu T^munu = 0 (ordinary rather than covariant derivative),
and I would interpret this as saying that each component of the
energy-momentum vector is locally conserved. Would you like to
restate it in some other way?

Dan