- Hardcover: 544 pages
- Publisher: Cambridge University Press; 1 edition (June 25, 2007)
- Language: English
- ISBN-10: 0521848415
- ISBN-13: 978-0521848411
- Product Dimensions: 6.8 x 1.1 x 9.7 inches
- Shipping Weight: 2.6 pounds
- Average Customer Review: 5 customer reviews
- Amazon Best Sellers Rank: #6,539,097 in Books (See Top 100 in Books)
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Universe or Multiverse? 1st Edition
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'... probably the most comprehensive tome on the subject around at the moment and, like the others, I imagine it will have a long shelf-life ... this well-constructed collection of writings is the best we can possibly hope for in the era of this new great debate.' Pedro Ferreira, Physics World
'This book really does lie at the frontier of cosmology, philosophy and possibly even theology. It is essential reading for anyone who wants to consider these ideas in depth.' Martin Redfern, Science, People and Politics
'Reading this book is a complex and rich experience. I find it useful as recommended reading as an introduction for undergraduate students.' Luca Valenziano, CERN Courier
'... an essential acquisition for those requiring an up to date account of the various physical proposals and their problems.' Science and Christian Belief
Is our universe unique or just one of many? Eminent physicists explain how recent scientific developments lead to the 'multiverse' proposal. Suitable for professional physicists and scientifically-minded lay people, the articles reflect the full diversity of views on this highly speculative and untestable theory.
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A caveat, however, don't turn to this book for an easy read. On the whole, these are essays by scientists writing for other scientists or for readers who are, for example, comfortable with equations, technical terminology, and densely reasoned arguments. For a less technical survey of the field, I'd recommend Brian Greene's _The Hidden Reality: Parallel Universes nd the Deep Laws of the Cosmos_.
For example, S. Weinberg, in the opening article of the book takes it as unacceptable that the cancellation by quantum fluctuations of the vacuum energy would have to be exact to 56 decimals places. But many who work in fields such as cryptography deal with much larger numbers than 10^56 in everyday practice, and therefore they would probably not be concerned so much with the purported delicacy in this cancellation. Weinberg's objection also reflects his insistence on explaining everything using symmetry arguments, which as the first part of the article is clear evidence of. He does not want to face up to solving the bound state problem (via the Schwinger-Dyson equations or some other approach). This is also manifested in his totally unsubstantiated claim that galaxies and stars would not form if the vacuum energy density was too large. No explicit calculation is done to support this claim in the context of quantum field theory, which is the proper framework in which to discuss the interactions of elementary particles which of course make up stars and galaxies. Showing explicitly that stars and galaxies would not form would be an enormously difficult calculation in quantum field theory, requiring extensive numerical calculation (possibly within the lattice gauge theory framework). Weinberg does not do this, or reference articles that do. Instead readers are given only a rudimentary hand-waiving argument.
The next article by F. Wilczek will be more palatable to the skeptical reader, for in it he discusses the role that symmetry principles have had in determining the values of the fundamental parameters, and argues that they have not been able to. If one is to accept fine-tuning, even though the evidence is weak and the definition of it not really stated explicitly in any of the literature, there is much to find plausible in Wilczek's statement that some parameters could be understood dynamically while others anthropically.
Some other parts of the book that might annoy the skeptical reader who insists on evidence supported by explicit calculations in quantum field theory include:
- The article by M. J. Rees wherein he claims that different values of the "fluctuation parameter" Q may prohibit clusters of galaxies from forming, and that galaxies would form later than they did in our universe. He admits though that some researchers have attempted to derive the value of Q using the detailed physics of an inflationary era. I better idea would be to face up to solving the bound state problem in quantum field theory in order to determine just what is possible for star and galaxy formation, etc.
- The article by B. Carr, wherein he states that "in order for life to exist, there must be carbon". This is true of course, but this does not support any evidence for the anthropic principle. How about explicitly showing how carbon atoms form using basic principles of quantum field theory? This would be a formidable undertaking, one that the author may not be prepared to do.
- The article by R. Kallosh, wherein it is claimed that the probability of the emergence of life would be "appreciably suppressed" for certain values of the cosmological constant. But how is this outlandish claim for the probability to be calculated? Life depends on carbon atoms of course, but it also depends on a complicated process of folding of protein molecules. The computational difficulties behind protein folding are well known, but these difficulties, along with a complete omission of any estimates from quantum field theory of how carbon atoms themselves can form, make this article absolutely worthless from a scientific viewpoint.
- The article by C. J. Hogan, which asserts that "the world would disappear" if there were only a few per cent fractional change in the quark mass difference. A diagram is given that is supposed to justify this assertion, but it does not. Showing that the "world would disappear" using the formalism of quantum field theory would again entail an understanding of how to solve the bound state problem.
There are many other examples in the book of handwaving, unjustified claims but space prohibits a detailed listing. Speculative discussions about fine-tuning and the multiverse abound, with the rhetoric of a type that usually accompanies debates in religion and philosophy. And indeed the silliness of the claims is only exceeded by the last articles in the book which attempt to give a religious "theistic" justification of the universe/multiverse. When reading these articles, one can easily wonder if some of the authors ever even calculated a cross-section or transition amplitude in quantum field theory, let alone have the expertise to approach the bound state problem. Fine-tuning may seem like a constraint on the values of the parameters that "allow life", but the values of these parameters do not seem to "optimize life" in the sense that living organisms face an uphill battle when it comes to sustaining themselves. Indeed, the conditions on Earth itself versus what is found in the rest of the solar system lead to the impression that reality is not conducive in general to the sustainment of living organisms. Not only that, but the authors of those articles that support theistic perspectives never seem to entertain the possibility that the creator of the universe is a temporary, finite being itself. These articles were written before the discussion of "Boltzmann brains" in inflationary scenarios, and a generalization of these "brains" would open up the possibility of an entity that could come into existence, create (a portion of) the universe, and then die off. This is extreme speculation of course, but no different than the other extreme speculations found in this book, and it would also be a kind of twist on the words put on the title of a popular weekly newsmagazine back in the 1960's, namely that God is dead.