On the Invariance of the Spacetime Interval

Marco Moriconi

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arXiv · 2512.14446

On the Invariance of the Spacetime Interval

Marco Moriconi

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Abstract

We present a geometric proof of the invariance of the relativistic spacetime interval based solely on the constancy of the speed of light, and the homogeneity and isotropy of spacetime. The derivation is based on a simple construction involving light rectangles, whose areas remain invariant across inertial frames. Based on this construction, we also derive the Lorentz transformations.

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Marco Moriconi. 2025-12-16. On the Invariance of the Spacetime Interval. https://arxiv.org/abs/2512.14446

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