In a homogeneous gravitational field … let there be a stationary system of co-ordinates … In a space free of gravitational fields let … This experience, of the equal falling of all … has yielded; but in spite of that the … But we arrive at a very satisfactory interpretation … exactly equivalent … This assumption of exact physical equivalence makes it … the usual theory of relativity forbids us to … bodies in a gravitational field seem a matter …
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