Isotropic Blackbody Cosmic Microwave Background Radiation as Evidence for a Homogeneous Universe

Timothy Clifton, Philip Bull, Chris Clarkson

Research output: Contribution to journalArticlepeer-review

Abstract

The question of whether the Universe is spatially homogeneous and isotropic on the largest scales is of fundamental importance to cosmology but has not yet been answered decisively. Surprisingly, neither an isotropic primary cosmic microwave background (CMB) nor combined observations of luminosity distances and galaxy number counts are sufficient to establish such a result. The inclusion of the Sunyaev-Zel’dovich effect in CMB observations, however, dramatically improves this situation. We show that even a solitary observer who sees an isotropic blackbody CMB can conclude that the Universe is homogeneous and isotropic in their causal past when the Sunyaev-Zel’dovich effect is present. Critically, however, the CMB must either be viewed for an extended period of time, or CMB photons that have scattered more than once must be detected. This result provides a theoretical underpinning for testing the cosmological principle with observations of the CMB alone.
Original languageEnglish
Article number051303
Pages (from-to)1-5
Number of pages5
JournalPhys. Rev. Lett.
Volume109
Issue number5
DOIs
Publication statusPublished - 1 Aug 2012

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