How does the Hubble sphere limit our view of the Universe?


  • Research undertaken as part of the Commonwealth Cosmology Initiative (CCI:, an international collaboration supported by the Australian Research Council.



It has recently been claimed that the Hubble sphere represents a previously unknown limit to our view of the universe, with light we detect today coming from a proper distance less than this ‘cosmic horizon’ at the present time. By considering the paths of light rays in several cosmologies, we show that this claim is not generally true. In particular, in cosmologies dominated by phantom energy (with an equation of state of ω < −1) the proper distance to the Hubble sphere decreases, and light rays can cross it more than once in both directions; such behaviour further diminishes the claim that the Hubble sphere is a fundamental, but unrecognized, horizon in the universe.