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Unformatted text preview: A different interpretation of the velocities seen in spiral nebulae soon turned up. De Sitter's model of a static universe had a diminishing frequency of light vibrations with increasing distance. Slipher had calculated velocities by using the rule that the frequency of light observed will change if the source of the light is moving rapidly away but perhaps this was an illusion. Perhaps distant objects were not really receding at great speeds, but were only emitting a different frequency of light. Nothing like that happened in Einstein's model of a static universe, so Slipher's measurements might give a way to choose between the two models. World War I had slowed communications, but by 1921 de Sitter knew of Slipher's velocity measurements for 25 spiral nebulae. Only 3 were approaching. They could be explained away as the result of large velocities in random directions, superimposed on a much smaller...
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