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In page Quasars, Redshifts and Controversies:

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Halton Arp's proposal was an idea based on analyses done before the sky surveys increased the number of measured redshifts by several orders of magnitude. The idea was that the cosmological redshift might be showing evidence of periodicity which would be difficult to explain in a Hubble's law universe that had the feature of continuous expansion. However, most astronomers agree that the analysis suffers from poor methodology and small number statistics.[citation needed]