Why is an improbable early universe unacceptable?

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Discussion Overview

The discussion centers around the concept of improbability in the context of the early universe, particularly regarding quantum fluctuations and the Big Bang. Participants explore the implications of low probability states and the anthropic principle, questioning why certain configurations are deemed improbable and how this relates to our understanding of cosmology and the multiverse theory.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants argue that the improbability of the early universe is not a valid concern since it has already occurred, suggesting that the probability becomes 1 post-event.
  • Others question the distinction between low probability and impossibility, seeking clarification on what is considered too improbable in this context.
  • There is a discussion about the multiverse theory, with some suggesting that our universe is one of many possible outcomes from quantum fluctuations, while others express skepticism about the speculative nature of these theories.
  • Participants highlight the challenge of explaining how the universe began in such an ordered state, noting that the probability of a low entropy state occurring is extremely small.
  • Some contributions emphasize that the universe's existence may not be a coincidence, questioning why we should view it as such after the fact.
  • There are references to the Boltzmann brain scenario, with participants discussing its implications and whether it constitutes a paradox.
  • One participant points out that the probability of complex arrangements, such as the formation of a textbook, is low but not surprising when considered retrospectively.
  • Another participant discusses the measure problem in cosmology, noting that the region of phase space that can produce a universe like ours is incredibly small.

Areas of Agreement / Disagreement

Participants express a range of views on the improbability of the early universe, with no clear consensus on whether it is a legitimate concern or merely a retrospective question. The discussion remains unresolved, with multiple competing perspectives on the implications of low probability states and the nature of the universe.

Contextual Notes

The discussion highlights limitations in understanding the early universe and the assumptions underlying various cosmological models. The speculative nature of multiverse theories and the measure problem in cosmology are noted as areas of ongoing debate.

  • #31
houlahound said:
Please define what a measure problem is.

A measure problem is either when different measures applied to the same space in a theory produce different predictions or there is no way to define a measure on a space at all.

Measures in set theory and topology are ways to assign numbers to subsets. They generalise lengths, areas and volumes.

https://en.wikipedia.org/wiki/Measure_(mathematics)

Measures also apply to probability spaces so come into topics like entropy and quantum theory.

Measure problems are endemic in cosmological theories and many different regularisation procedures have been created to overcome them but none are generally accepted. In eternal inflation theories the problem is how to apply probability measures to infinite sets of causally disconnected universes. In canonical quantum gravity the Wheeler-deWitt equation is regularisation dependent.

https://en.wikipedia.org/wiki/Measure_problem_(cosmology)

houlahound said:
Please define what a measure problem is.
 
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