Re: a relativity question

[John Mallinckrodt <ajm@CSUPOMONA.EDU>]

Jack Uretsky wrote:

> Be not so arbitrary, John.  It is a matter of convention as to whether
> "mass" means restmass or it means the energy of a system divided by c^2.
> Using the latter definition, and delta E = mgh, one gets the correct
> answer for the Pound-Rebka experiment and 1/2 the correct answer for the
> bending of light by the sun (the other half we can ascribe to the
> curvature of space).
>
> Convention is like religion, you know.  Whatever gives you your jollies is
> fine with me.

Fair enough, I guess.

However, I don't think I'm the one who is being "arbitrary."  It
seems to me that there is remarkable clarity to be had by subscribing
to the increasingly accepted (and *not* at all arbitrary) convention
that "mass" means "invariant mass."  Indeed, I think the question
that initiated this thread is a very direct and obvious result of the
confusion engendered by teaching that mass is simply "energy (of any
kind) divided by c^2."

--
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.