There’s a new popular book out this week entitled Once Before Time: a whole story of the universe, by Martin Bojowald, promoting his ideas about “Loop Quantum Cosmology”. It’s a translation of the original German edition, Zuruck vor den Urknall, published last year.
The topic of the book is work by Bojowald on toy models using loop quantum gravity that avoid the Big Bang initial singularity of classical general relativity. For a much shorter version of all this, see his 2008 Scientific American cover story Big Bang or Big Bounce?
There’s a very deep human desire to understand origins and thus to trace the history of the universe back before the earliest periods for which cosmological theory and observations have provided some degree of scientific understanding. Unfortunately this has led in recent years to a flood of over-hyped claims by physicists claiming to have a scientifically viable theory of what happened “Before the Big Bang”. To qualify as legitimate science, such claims need to be backed up by some conventional sort of evidence. This might take the form of experimental predictions, testable either now or in principle in the future. It might also take the form of a highly constrained and beautiful theory whose success in other realms makes a compelling case that it could also explain experimentally inaccessible phenomena. I don’t know of any example of such pre-Big Bang scenarios now being sold to the public that comes even close to having such backing.
The cover of Bojowald’s book tells us about Loop Quantum Cosmology:
Now the theory is poised to formulate hypotheses we can actually test.
I’m no sure exactly what that is supposed to mean, but it appears to be misleading hype, not corresponding to anything actually in the book. The text of the book itself wavers back and forth, sometimes explaining the overwhelming problems one faces if trying to extract some kind of prediction out of the LQC framework and emphasizing how speculative it all is, at other times expressing ungrounded optimism that somehow these problems will be overcome. It ends on an upbeat, hopeful note
Will we ever, with a precision that meets scientific standards, see the shape of the universe before the big bang? The answer to such questions remains open. We have a multitude of indications and mathematical models for what might have happened. A diverse set of results within quantum gravity has revealed different phenomena important for revealing what happened at the big bang. But for a reliable extrapolation, parameters would be required with a precision far out of reach of current measurement accuracies. This does not, however, mean that it is impossible to answer questions about the complete prehistory of the universe. Cosmology as well as theoretical investigations are currently moving forward and will result in unforeseen insights. Among them might well be experimentally confirmed knowledge of the universe before the big bang.
but I found nothing in the book to justify this optimism. The few allusions to specific attempts to find some relation to something observable are vague and suffer from the book’s nearly complete lack of any references to more technical sources of information.
About fifteen years ago, in The End of Science, John Horgan described the field of fundamental physics as degenerating into what he called “ironic science”, something more like literature, art or philosophy than traditional science, pursued in a “speculative post-empirical mode”. At the time I thought he was going too far, but Bojowald’s book provides an unfortunate confirmation of the phenomenon Horgan was describing. It’s written in a rather dense and sometimes impenetrable style, featuring quotations from Nietzsche, some science-fiction set off in italics, and a few pictures of contemporary art-works supposedly relevant to the argument. Attempts are made to claim a role for pre-Socratic philosophy, with LQC finally providing a means of going beyond the pre-Socratics:
Otherwise, one can find among the pre-Socratics most of the elements of modern cosmology. Only with quantum gravity did truly new elements enter the game.
Aficionados of the loop quantum gravity – string wars will find various accurate comments about string theory and the sociology of science, and Bojowald also describes an interesting insider’s point of view on the story of the development of loop quantum gravity and the scientific figures behind it. He’s quite right that it’s a fascinating possible approach to quantum gravity well worth pursuing, but the applications to cosmology seem to me not even close to being ready for prime-time and this kind of treatment in a popular book.
Update: There’s a review by Brian Clegg at the Wall Street Journal here.
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