Re: New version of a relativity FAQ

Juan R. González-Álvarez wrote:
Tom Roberts wrote on Mon, 23 Jun 2008 12:00:41 +0200:
As I challenged before: write down the Lagrangian for classical
electrodynamics in terms of "relativistic mass" and all those 3-vectors.
Then do it for QED. THESE are the sort of problems with which
theoretical physicists are concerned; indeed, these are SIMPLE and
WELL-KNOWN problems, the real point is to use the known symmetries of
the world to find NEW theories. "Relativistic mass" completely abandons
the underlying symmetry, and is indeed useless for that; the 4-vectors
used by mainstream theoretical physicists make the Lorentz symmetry
completely transparent (i.e. one can tell at a glance if one's guessed
Lagrangian is Lorentz invariant or not).

Your argumentation may be pretty applied to your geometrical views on gravitation.

I don't have "geometrical views on gravitation", I have geometrical views on GENERAL RELATIVITY. Because that theory is, in essence, geometrical, regardless of whether or not there are other interpretations of it.


"Now write the GR Lagrangian in terms of metric spacetime, R and all those geometric stuff. Then do it for hypothetical QGR. THESE are the sort of problems with which theoretical physicists are concerned [...] geometric GR is indeed useless for that."

Probably. Almost certainly. Indeed, it seems likely that a full theory of quantum gravity will abandon the whole notion of a continuous manifold (certainly the current major efforts toward QG do that). The geometry of GR is, of course, inherently based on an underlying manifold.


Tom Roberts
.

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