What did it mean, that strange new phrase, expanding universe ? It meant that the light from distant nebulae was red-shifted not from some peculiar de Sitter effect, but because the nebulae were actually moving away from us. This was not because there is anything special about us — by now astronomers understood that the nebulae are galaxies more or less like our own. Each of these galaxies was moving away from all the other galaxies. Space itself was expanding between them. There was no special point somewhere among the stars where the great expansion had started—we and all other galaxies are inside that place. Thus the farther any two galaxies were apart, the faster they continued to separate—which was precisely Hubble's velocity-distance relation.
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