It’s not every book which changes my understanding of how the Universe works, but Lee Smolin’s recent work, Time Reborn, does the trick nicely.
I bought it for myself a few months ago, expecting that it would be a rather typical example of the “pop-science” genre. No doubt, I figured, the author has devised some new theory and is trying to publicize it. What I thought that I would find was a tantalizing glimpse of an interesting new idea, but with all of the awkward mathematical bits (which are nonetheless necessary for real understanding) banished to the supplementary reading.
How wrong I was! Smolin is not arguing for a new theory–he’s arguing for a new Physics altogether.
Physics, Lee Smolin argues, has reached a dead-end. For the past four hundred years, it has successfully explained the behaviours of parts of our Universe (everything from sub-atomic particles to groups of galaxies), but when we attempt to apply it to the Universe itself, it breaks-down. The same assumptions which formerly served us so well start producing either ridiculous results or theories which could describe a nigh-infinite number of possible Universes with no means of telling us, a priori, which Universe we live in. After decades of waiting for Physics to resolve this problem, Smolin has concluded that it can not…or at least, not in its present form.
The author critiques the very philosophy behind Physics as a discipline. His hero is the seventeenth-century German polymath (and Newtonian rival) Gottfried Leibniz, whose Principle of Sufficient Reason (and its derivatives) serve as Smolin’s primary tool. This Principle holds that everything in the Universe should be the way that it is for some rational reason; or, as the author puts it: “there should be an answer to any reasonable question we ask about why the Universe has a particular feature.” Current Physics does not provide such answers; it cannot tell us why the laws of Physics are the way that they are instead of some other way, or why, for that matter, the initial conditions of the universe should have been what they were either. To Smolin’s mind, this represents a critical flaw, and so he promotes the overthrow of what he calls the “Newtonian Paradigm” of Physics (under which the Universe is governed by unchanging and indeed timeless mathematical laws which simply exist) and its replacement with a more Leibnizian view, whereby the “why these laws?” question can, in principle, be answered. This has the incidental effect, as Smolin argues, of reifying time.
Here it’s necessary for me to point-out that our current Physics, by and large, assumes (perhaps counter-intuitively) that time doesn’t really exist*. And Smolin is quick to note, the case against time is actually pretty formidable. Quantum Field Theory, describing the interactions of fundamental particles, appears fully reversible in time; Special Relativity can be used to argue that if the present is real, then the entire history and future of the universe must also be real. And perhaps most damningly, the laws of physics (even though they may contain time-dependent terms) are purely mathematical objects and as such exist outside of the flow of history–a calculation performed today will produce the same result as it would a million years ago, or a million years from now. But Smolin shows that all of these supposed proofs of the unreality of time depend upon what he calls the “Cosmological Fallacy:” the supposition that a rule derived by looking at a part of the Universe (under the unphysical assumption that it is completely isolated from everything else) can be meaningfully applied to the Universe itself. The author correctly points-out that there is no logical basis for this assumption.
The remainder of the book is largely spent surveying new hypotheses on the cutting edge of physics which adhere to Smolin’s new paradigm while reproducing the successes of the old Newtonian view. To his credit, the author tries to limit himself to hypotheses which are actually currently falsifiable by experiment, viewing the alternative as being unscientific.
While the book has some powerful arguments (and I would personally argue that the argument against the Cosmological Fallacy is actually stronger than the titular argument in favour of the reality of time), it is not without its flaws. Chief among them is that Smolin never satisfactorily explains why we should assume the truth of Leibniz’s Principle of Sufficient Reason. Leibniz’s reason was clear: he believed in a rational God–but surely such a belief should not underpin physics in the twenty-first century. Nor does he explain how other principles, such as “the Principle of No Unreciprocated Actions” emerges as a consequence of the Principle of Sufficient Reason; I am not a philosopher, but it does not seem at all obvious to me that it does. Finally, the book could possibly benefit from providing a survey (and refutation) of philosophical arguments which no doubt exist against Leibniz’s principles. I hope that these issues will be addressed in the follow-up book that Lee Smolin is writing on this topic alongside philosopher Roberto Mangabeira Unger.
*Or, to quote Albert Einstein, “people like us, who believe in physics, know that the distinction between past, present and future is only a stubbornly persistent illusion.”