“An "empty world," i. e., a homogeneous manifold at all points at which equations (1) are satisfied, has, according to the theory, a constant Riemann curvature, and any deviation from this fundamental solution is to be directly attributed to the influence of matter or energy.”

—  Howard P. Robertson

"On Relativistic Cosmology" (1928)

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Howard P. Robertson 28
American mathematician and physicist 1903–1961

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