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Very long wavelength universal gravitational waves cannot now produce in clusters of galaxies velocity dispersions greater than that which these systems would possess if they were expanding with the Universe, if the Universe is not younger than 10¹⁰ yr and Hubble's constant is not less than 50 km/sec/ Mpc. A diagram shows that actual velocity dispersions are significantly greater than this limit.
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John C. Jackson (1972) studied this question.
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