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Re: a relativity question



Bob Sciamanda wrote:

John Mallincrodt wrote:
" . . . No; an elevated mass does not "have" more energy despite the
implications of standard textbooks (and not to mention the usefulness
of that gentle subterfuge in many common situations.) Gravitational
potential energy is a property of a *system* of interacting masses. . . ."

Which system?

Any system, as long as you are clear about what's "in" the system and
what is not.

The car/earth system is part of the earth/moon system, is
part of the earth/sun system, is part of the solar system, is part of the
milky way system, is part of . . . the universe. Thus the mass of the
universe increases, but not the mass of its parts!

It sounds like this is intended as an objection, but I'm not sure I
understand the specific nature of your objection. If it has to do
with a question about what happens to the idea of invariant mass when
applied to objects of cosmological scale or to the whole universe,
then I will admit that I'm not quite sure. But I don't see any
particular ambiguity or difficulty in the case of atomic scale, car
scale, or Earth scale objects.

Am I missing your point?

--
John Mallinckrodt mailto:ajm@csupomona.edu
Cal Poly Pomona http://www.csupomona.edu/~ajm

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.