Change Without Change, and How to Observe it in General Relativity

Healey, Richard (2003) Change Without Change, and How to Observe it in General Relativity. UNSPECIFIED. (In Press)

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Abstract

All change involves temporal variation of properties. There is change in the physical world only if genuine physical magnitudes take on different values at different times. We defend the possibility of change in a general relativistic world against two skeptical arguments recently presented by John Earman. Each argument imposes severe restrictions on what may count as a genuine physical magnitude in general relativity. These restrictions seem justified only as long as one ignores the fact that genuine change in a relativistic world is frame-dependent. We argue on the contrary that there are genuine physical magnitudes whose values typically vary with the time of some frame, and that these include most familiar measurable quantities. Frame-dependent temporal variation in these magnitudes nevertheless supervenes on the unchanging values of more basic physical magnitudes in a general relativistic world. Basic magnitudes include those that realize an observer's occupation of a frame. Change is a significant and observable feature of a general relativistic world only because our situation in such a world naturally picks out a relevant class of frames, even if we lack the descriptive resources to say how they are realized by the values of basic underlying physical magnitudes.

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Creators:

Creators	Email	ORCID
Healey, Richard

Keywords:

change, general relativity, observables

Subjects:

Specific Sciences > Physics > Relativity Theory
General Issues > Theory/Observation

Depositing User:

Richard Andrew Healey

Date Deposited:

15 May 2003

Last Modified:

13 Sep 2015 15:49

Item ID:

1162

Public Domain:

Commentary on:

Earman, J.: 2002, �Thoroughly Modern McTaggart: or What McTaggart Would Have Said If He Had Learned the General Theory of Relativity�, Philosophers� Imprint 2, http://www.umich.edu/~philos/Imprint/frameset.html?browse

Subjects:

Specific Sciences > Physics > Relativity Theory
General Issues > Theory/Observation

Date:

May 2003

URI:

https://philsci-archive.pitt.edu/id/eprint/1162