Universe or Multiverse? [Hardcover]

Bernard Carr (Editor)

Book Description

Publication Date: June 25, 2007 | ISBN-10: 0521848415 | ISBN-13: 978-0521848411 | Edition: 1

Recent developments in cosmology and particle physics, such as the string landscape picture, have led to the remarkable realization that our universe - rather than being unique - could be just one of many universes. The multiverse proposal helps to explain the origin of the universe and some of its observational features. Since the physical constants can be different in other universes, the fine-tunings which appear necessary for the emergence of life may also be explained. Nevertheless, many physicists remain uncomfortable with the multiverse proposal, since it is highly speculative and perhaps untestable. In this volume, a number of active and eminent researchers in the field - mainly cosmologists and particle physicists but also some philosophers - address these issues and describe recent developments. The articles represent the full spectrum of views, providing for the first time an overview of the subject. They are written at different academic levels, engaging lay-readers and researchers alike.

Editorial Reviews

Review

'... 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

Book Description

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.

See all Editorial Reviews

Product Details

• Hardcover: 544 pages
• Publisher: Cambridge University Press; 1 edition (June 25, 2007)
• Language: English
• ISBN-10: 0521848415
• ISBN-13: 978-0521848411
• Product Dimensions: 9.7 x 7.1 x 1.1 inches
• Shipping Weight: 2.6 pounds
• Average Customer Review: 4.5 out of 5 stars  See all reviews (4 customer reviews)
• Amazon Best Sellers Rank: #1,629,015 in Books (See Top 100 in Books)

Customer Reviews

Most Helpful Customer Reviews

17 of 19 people found the following review helpful:

5.0 out of 5 stars An excellent book on a very interesting topic, November 1, 2007

By 

Jill Malter ([e-mail]) - See all my reviews

This review is from: Universe or Multiverse? (Hardcover)

This is a wonderful and highly readable book about the question of whether or not our universe is part of a multiverse. The more than two dozen contributors all do a fine job.

We see plenty about the Anthropic Principle and about the Copernican Principle (also known as the Principle of Mediocrity). The Anthropic Principle merely points out that given that we exist in this universe, our universe must be habitable. But this argument can be extended. Steven Weinberg shows how he was able to use the Principle of Mediocrity and the Anthropic Principle to put some interesting probable bounds on a cosmological constant. A universe with such a constant being less than 0.6 would be relatively unlikely for humans to be in, so his guess was that this constant was over 0.6. At the time, most guesses for the cosmological constant were 0.0, but soon after this, studies of supernovae showed that this constant is around 0.7. Several of the contributors discuss this argument. It's an unusual type of argument, and Weinberg makes an analogy to Einstein's use of a symmetry principle argument to come up with the Special Theory of Relativity (nowadays, symmetry principle arguments are commonplace, but Einstein's, in 1905, was the first major successful one).

Several contributors also discuss Hoyle's use of the Anthropic Principle to claim that there must be an excited state of Carbon-12 with the right energy to produce carbon in stars. This excited state is no big surprise, given the general properties of alpha-particle couplings, so Weinberg and others are unimpressed. However, I side with Hoyle here.

Weinberg explains that we now have a vast number of possible values of physical parameters provided by the "string landscape." By the Anthropic Principle, we can guess that we must be in a universe that permits us to exist. The reader is left to guess that therefore, there are probably many other universes where we can not and do not exist.

Weinberg also points out that the Anthropic Principle shows how the universe can appear to be fine-tuned to allow our existence without requiring some sort of Intelligent Creator or Creators.

Frank Wilcek shows how in the case of inflationary cosmology, we see that universal laws need not be multiversal.

Stephen Hawking says that the reason we live in four dimensions (three of which are spatial) is not due to any anthropic principle (maybe there could be intelligent life in eleven dimensions) but simply because we can see that we live in four dimensions. He does, however, say that it may be significant that we live in the interior of anthropically allowed regions of omega-space. By not being at the edge of such a region, we wind up in a universe with many galaxies, not just one galaxy. That implies that variations in omega are fairly flat. One galaxy ought to suffice for life to exist, and since there are many, Hawking does not conclude that we need many galaxies, but that there are in fact many sites which contain life. Max Tegmark also indicates that there may be plenty of life in the Galaxy, as well as as many as 10 to the 20 "habitable planets in our Hubble volume alone." Our Hubble volume is, of course, what many of us would call the Universe.

Craig Hogan discusses the difference between the down quark mass and the up quark mass, in relation to the electron mass. Well, that's obviously critical for life: it causes the neutrons to be a little heavier than the protons. If we change that mass difference, we can quickly get into regimes in which chemistry does not exist.

Let me give an example of the Principle of Mediocrity, which says that in the absence of evidence to the contrary, we ought not treat ourselves (or our position in the universe) as special. Suppose there is a big lottery with a hundred winners. The winners are congratulated, but they are not told in what order they were selected. They are then told that they will double their winnings if they guess correctly whether they were in the first 25 or last 75 to be chosen. Invoking the Principle of Mediocrity, they all guess that they were in the final 75. At the awards ceremony the winners are presented in the order they were chosen. We note that the first few all guessed wrong! Does that show a problem with the Principle of Mediocrity? Of course not, and we see that when the final 75 all guess right.

Incredibly, in his chapter, Lee Smolin steps out of character and makes a big logical error. He gives the case in which the population of the world increases exponentially. Many people realize that there may be a population crash, and using the Principle of Mediocrity, they guess that they have a relatively high chance to be in the final few generations before that crash. Smolin boasts that someone 1000 years ago would have been incorrect to make such an argument. But he's totally wrong here: he's ignoring the fact that in his example, the majority of those who make this argument will be right. That means that everyone was right to make that argument, even the minority who get the wrong answer thereby.

I think that the Principle of Mediocrity is indeed a very good default that can spare us from making wild arbitrary politically correct guesses, but it is still just a default.

I truly enjoyed this book, and I highly recommend it.

1 of 1 people found the following review helpful:

5.0 out of 5 stars Superb multiverse compendium by the experts in the field, October 21, 2011

By 

Robert Adler "science writer & author" (Santa Rosa, CA USA) - See all my reviews
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Amazon Verified Purchase

This review is from: Universe or Multiverse? (Paperback)

Popular science outlets have been covering the possibility that our universe is just one among a potentially infinite number of universes--the multiverse--for years now, but in bits and pieces. If you are seriously interested in the science behind the various multiverse concepts, read this book. It's a compendium of 28 invited articles on every aspect of the multiverse field by the theoreticians and researchers who invented and are advancing this very active area. I found Bernard Carr's essay on the anthropic principle very helpful, along with Max Tegmark's multiverse hierarchy,Leonard Susskind's discussion of the anthropic landscape of string theory, Lee Smolin's essay on alternatives to the anthropic approach, and John Barrow's "Living in a simulated universe." However, readers will find definitive essays on every aspect of the multiverse, inclouding many that don't get covered in the popular science press.

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_.

2 of 3 people found the following review helpful:

5.0 out of 5 stars The state of knowledge as it stands now, February 15, 2010

By 

John Matlock "Gunny" (Winnemucca, NV) - See all my reviews
(REAL NAME)   

This review is from: Universe or Multiverse? (Paperback)

One answer to the question about us being the only intelligent life in the cosmos is answered by the multiverse theory of multiple universes. This is a subject that has received a lot of thinking and mathematical analysis in recent years. Recent developments in cosmology and particle physics, such as the string landscape picture, have led to some serious thinking that ours is not the only universe.

This book has papers from a number of active and eminent researchers in the field, mainly from cosmologists and particle physicists, but also from such diverse fields as philosophy. The papers cover the complete spectrum from enthusiastic support to outright scepticism. There is very little advanced mathematics in the book when compared with some other texts on the subject.