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21 - Making predictions in a multiverse: conundrums, dangers, coincidences

Published online by Cambridge University Press:  05 July 2014

By
Anthony Aguirre
Edited by
Bernard Carr
Anthony Aguirre
Affiliation:
University of California
Bernard Carr
Affiliation:
Queen Mary University of London
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Summary

Introduction

The standard models of particle physics and cosmology are both rife with numerical parameters that must have values fixed by hand to explain the observed world. The world would be a radically different place if some of these constants took a different value. In particular, it has been argued that if any one of six (or perhaps a few more) numbers did not have rather particular values, then life as we know it would not be possible [1]; atoms would not exist, or no gravitationally bound structures would form in the Universe, or some other calamity would occur that would appear to make the alternative universe a very dull and lifeless place. How, then, did we get so lucky as to be here?

This question is an interesting one because all of the possible answers to it that I have encountered or devised entail very interesting conclusions. An essentially exhaustive list of such answers follows.

  1. (i) We just got very lucky. All of the numbers could have been very different, in which case the Universe would have been barren, but they just happened by pure chance to take values in the tiny part of parameter space that would allow life. We owe our existence to one very, very, very lucky roll of the dice.

  2. (ii) We were not particularly lucky. Almost any set of parameters would have been fine, because life would find a way to arise in nearly any type of universe.

  3. […]

Type
Chapter
Information
Universe or Multiverse? , pp. 367 - 386
Publisher: Cambridge University Press
Print publication year: 2007

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