Is the Principle of Relativity a Tautology? (Yes, Almost – With a Key Assumption About Locality)

The principle of relativity often gets treated as a postulate (Einstein's assumption) or experimental fact (e.g., Michelson-Morley), but what if it's nearly tautological? Here's the gist from my note:

This note presents a conceptual argument demonstrating why the principle of relativity can be regarded as near-tautological. By combining the indistinguishability of uniformly moving closed systems—including co-moving light sources—with the requirement of strict locality (causal effects propagate locally, no instant action-at-a-distance—else space loses meaning), the invariance of the laws of physics across inertial frames follows analytically from physically well-motivated premises. The discussion clarifies why the principle, traditionally treated as a postulate or empirical fact, emerges as nearly inevitable when demanding a spacetime with meaningful causal structure.

For the full derivation, check the archived version on Zenodo:

PhysicsV.com (2025). A Refined Near-Tautological Derivation of the Principle of Relativity: From Strict Locality and Indistinguishability (Pedagogical note). Zenodo. https://doi.org/10.5281/zenodo.17982793

-- Me@2025-12-19 01:27:50 PM

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2025.12.19 Friday (c) All rights reserved by ACHK