Cheung, Siu Mui (2026) Light Propagation in Curved Spacetime: Geometry, Travel Time, and the Interpretation of Invariance. [Preprint]

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Abstract

This paper develops a philosophy-of-physics reinterpretation of light propagation in curved spacetime. The central question is whether some intuitions commonly expressed in terms of light having different speeds in different gravitational or geometric settings are better understood as claims about geometry, travel time, and measurement than as literal denials of relativistic invariance. To answer that question, the paper distinguishes local measurements of vacuum light propagation from global and coordinate-dependent descriptions across extended curved regions. It then places that distinction in dialogue with three bodies of literature: experimental and theoretical work in general relativity, explicit varying-speed-of-light proposals, and recent philosophy-of-physics debates about spacetime geometry, dynamical explanation, and curvature realism. The main claim is limited but substantive. Curved spacetime helps determine the observable propagation history of light between separated events, yet this does not by itself support the conclusion that locally measured vacuum light speed varies in a way that overturns relativity. The paper therefore argues that the strongest version of the underlying idea is interpretive rather than revisionary: it concerns how invariance should be understood, described, and explained within relativistic physics.

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Item Type:	Preprint
Creators:	Creators Email ORCID Cheung, Siu Mui
Keywords:	philosophy of physics; relativity theory; curved spacetime; light propagation; invariance; spacetime geometry; measurement; Shapiro delay
Subjects:	General Issues > Explanation General Issues > Operationalism/Instrumentalism Specific Sciences > Physics > Relativity Theory
Depositing User:	Ms Siu Mui Cheung
Date Deposited:	31 May 2026 12:48
Last Modified:	31 May 2026 12:48
Item ID:	29825
Subjects:	General Issues > Explanation General Issues > Operationalism/Instrumentalism Specific Sciences > Physics > Relativity Theory
Date:	May 2026
URI:	https://philsci-archive.pitt.edu/id/eprint/29825

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