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There are plenty of ways the Universe could be steady-state and still not have a white-hot sky. Suppose you have metric expansion as you do now, but new matter

There are plenty of ways the Universe could be steady-state and still not have a white-hot sky. Suppose you have metric expansion as you do now, but new matter magically appears as a sparse, uniform cloud of particles throughout space to feed the creation of new stars and maintain the energy density we see today. Metric expansion guarantees that light is redshifted in proportion to distance, so the sky remains dark, even though the Universe is infinitely old and stable. This model is wrong, obviously, but the reason has nothing to do with Olber's paradox.

jerf 11y ago
The Steady State hypothesis isn't really a class of hypotheses, it was a specific one. The Steady State hypothesis predates the entire concept of metric expansion, after all. History, everyone. Olber's paradox is important because of the history, not its relevance to 21st century physics.
- goodside 11y ago
  The model I described is the historical model, as developed (and later repudiated) by Einstein. It does not "predate the entire concept of metric expansion". The whole point was to reconcile expansion, which was both predicted by GR and confirmed by Hubble's observation of recessional redshift, with the belief that the Universe was infinitely old and unchanging. And there were many variants of Steady State, as the model was discovered independently after Einstein, and refined throughout the 1950s as its adherents struggled to explain new observations that distant quasars are far more common than near ones. There was even a brief (and apparently failed) attempt by Hoyle to revive a Steady State as late as 1993, involving widely varying rates of expansion in different regions of the Universe. What ultimately disproved Steady State was seeing the CMBR. None of this has anything to do with Olber's paradox, which is not an issue in a Steady State model for exactly the same reasons it's not an issue in modern cosmology.

jerf 11y ago

The Steady State hypothesis isn't really a class of hypotheses, it was a specific one. The Steady State hypothesis predates the entire concept of metric expansion, after all. History, everyone. Olber's paradox is important because of the history, not its relevance to 21st century physics.

goodside 11y ago
The model I described is the historical model, as developed (and later repudiated) by Einstein. It does not "predate the entire concept of metric expansion". The whole point was to reconcile expansion, which was both predicted by GR and confirmed by Hubble's observation of recessional redshift, with the belief that the Universe was infinitely old and unchanging. And there were many variants of Steady State, as the model was discovered independently after Einstein, and refined throughout the 1950s as its adherents struggled to explain new observations that distant quasars are far more common than near ones. There was even a brief (and apparently failed) attempt by Hoyle to revive a Steady State as late as 1993, involving widely varying rates of expansion in different regions of the Universe. What ultimately disproved Steady State was seeing the CMBR. None of this has anything to do with Olber's paradox, which is not an issue in a Steady State model for exactly the same reasons it's not an issue in modern cosmology.