Hubble's law in astronomy, statement that the distances between galaxies (see galaxy ) or clusters of galaxies are continuously increasing and that therefore the universe is expanding. Discovery and Explanation of the Red Shift Edwin Hubble first proposed this law in 1929 based on a study of the light received from the distant galaxies. He observed that the characteristic colors, or spectral lines (see spectrum ), emitted by the stars in the galaxies do not have exactly the same wavelengths observed in the laboratory; rather they are systematically shifted to longer wavelengths, toward...
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