The Abc Of Relativity by Bertrand Russell

A lucid, nontechnical introduction to Einstein’s theories of special and general relativity that explains how measurements of space and time depend on the observer, clarifies simultaneity and the Lorentz transformations, and shows how gravity can be understood as curvature of spacetime via the equivalence principle; it uses thought experiments and clear analogies to present the key physical ideas, experimental confirmations, and philosophical implications for our notions of absolute space and time.

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