Time Reborn by Lee Smolin

Cover of Time Reborn, a physics book by theoretical physicist Lee Smolin. Houghton Mifflin Harcourt

The Controversy

Before I can even begin a review of the book, I do feel that a bit of background must be provided on the scientific context in which this book appears. Smolin is a prominent if controversial figure within the theoretical physics community, well known for work on the cutting edge of our knowledge and promoting that work directly to the general public well before it has become widely accepted within the physics community itself.

Back in the 1990's, he published a work that focused on the idea that the universe (or rather a series of reproducing universes) evolved over time. The basic idea of Smolin's proposal for an evolving universe is that a universe can create other universes through the creation of black holes, meaning that it's highly probable that the universe we're in is one that is optimized for the creation of black holes. As I said, he's controversial!

Then, in 2001, he wrote The Three Roads to Quantum Gravity, which argued that differing approaches to the problem of quantum gravity (string theory, M-Theory, and loop quantum gravity) could work together to come up with an underlying theory of quantum gravity. This was a controversial stance within the physics community because string theory and M-Theory are both highly prominent theories that have been developed and worked on by a large number of scientists over the previous couple of decades ...

while loop quantum gravity was an approach which Smolin himself had helped to develop and pioneer, but which had nowhere near the same amount of acceptance within the theoretical physics community. In other words, The Three Roads to Quantum Gravity was seen by some as an attempt to artificially elevate Smolin's own pet theory to equal status with the prevailing approach to quantum gravity, even though many theoretical physicists did not believe it earned that status.

In his 2006 The Trouble With Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next, Smolin goes even further, claiming that the approach at the heart of string theory is fundamentally harming physics itself. In this book, he outlined 5 great problems in theoretical physics which, while still a controversial list, basically hits the mark of a number of things that theoretical physics really can't explain without speculating well beyond the foundation provided by the current evidence. He points out that string theory has failed to solve this problem ... or even to anticipate that some of these problems would arise. Needless to say, for a community that had spent three decades investing time, energy, and resources into developing string theory, this was not a welcome book, and the "string wars" have certainly had some memorable exchanges, even informing romantic breakdowns on television's The Big Bang Theory.

The current book that I'm about to review is just as controversial ... if not moreso. I found it an engaging book and am certainly recommending it, but it should be read with a great deal of care and skepticism. As I will discuss in the review, many aspects of Smolin's approach involves assumptions of his own which are, at best, no more certain than the assumptions he is trying to argue against.

Smolin's "Crisis in Science" Revisited

In Time Reborn: From the Crisis in Physics to the Future of the Universe, theoretical physicist Lee Smolin of Canada's The Perimeter Institute is once again taking a bold new scientific vision directly to the popular audience. This time, he's tackling the notion of time itself. In his stance, the current scientific understanding of time is that time is not "real" and he feels that's a fundamental flaw, one that could be corrected by taking time serious as a real quantity ... in fact, it would in his vision be one of the only real quantities, with the rest of the universe - indeed the very laws of the universe - evolving within time.

What he suggests is that instead of laws of physics that eternal and everlasting, physicists instead treat physics in a more "relational" way, in which they are viewed as dynamic systems of behaviors.

A key point in this is that Smolin himself is candidly honest that he's not presenting such a theory himself (at least not at this time):

The purpose of this book is to suggest that there is another way. We need to make a clean break and embark on a search for a new kind of theory that can be applied to the whole universe -- a theory that avoids the confusions and paradoxes, answers the unanswerable questions, and generates genuine physical predictions for cosmological observations.

I do not have such a theory, but what I can offer is a set of principles to guide the search for it.

Why does Smolin believe that such a theory is necessary? In part, it is an argument not rooted so much on science itself as on the field of natural philosophy and specifically grounded in the work of philosopher Gottfried Leibniz.

The Principle of Sufficient Reason

Leibniz is well known in scientific circles for having independently developing calculus at the same time that Sir Isaac Newton was also doing so, but Leibniz's body of work as a philosopher is far more well-developed than that. Specifically, he held a belief that all things that happen in the universe have an exact cause. Leibniz was deeply religious, so his stance was basically that God had a reason for every choice he made and that none of these choices could be arbitrary. Smolin does not rely on a divinity for his argument, but he is willing to accept as a fundamental principle that everything that happens has a reason for that thing happening as opposed to something else, and given knowledge of all of the factors going into the result, there would be no other possible outcome.

This of course seems like a perfectly reasonable ... except that the last century's work in quantum physics has drastically challenged this notion. In situations such as the quantum double slit experiment and the EPR Paradox, it really seems as if things happen on the quantum level with a given probability. In the customary formulation of the EPR paradox, for example, when a particle decays into two particles of opposite spin, there is really no way to determine prior to the event which particle will have which spin.

The best we can do is estimate the probabilities. And, in our understanding of quantum physics, this isn't just a matter of us missing some information ... there's actually no way to tell which is which.

Smolin rejects this conclusion, insisting that there must be something fundamental that quantum physics has missed. He is a proponent of a hidden variables theory, even though most physicists agree that Bell's Theorem has really ruled out the possibility of any such theory. At least, to date, no one has come up with one that really works.

Cosmological Fallacy

Having embraced Leibniz's stance, Smolin introduces the idea of a cosmological fallacy, which he defines as:

It remains a great temptation to take a law or principle we can successfully apply to all the world's subsystems and apply it to the universe as a whole. To do so is to commit a fallacy I will call the cosmological fallacy.

Now, this takes some parsing out to really figure this out. First of all, realize that all of cosmology (and astrophysics, for that matter) involves taking results we observe on Earth and extending them to apply to distant parts of the universe. In other words, we basically assume that the physics we observe here on Earth and in our nearby region of space applies equally well to distant regions in space. In other words, our world and region of space are not particularly special. This is a principle called the Copernican principle. Smolin does not seem to be arguing against this practice.

However, the whole reason that we develop these findings on Earth is through testing them with experiments that are carefully controlled, so we know as precisely as we can which influences are caused by which components of the system. This cannot, of course, be done to the universe as a whole. Smolin rightly identifies this as a major problem in cosmology. We have a sample of only one universe, after all.

But what about the multiverse, you ask? Smolin views this as an attempt by physicists to create a hypothetical set of possible universes, so that applying normal methodologies seems valid. But, since we actually can't observe these universes, I admit that it's a highly suspect conclusion.

Smolin's Science

Despite his goal of treating time as "real" in a new way, Smolin is not suggesting that any current scientific evidence is incorrect. In other words, he's not saying that relativity itself is wrong when it talks about the fluid nature of time, only that there might be alternative explanations or theoretical structures which would yield the same correct results as relativity but would be a bit less relativistic in how it talks about time. (He discusses one approach in the book, called shape dynamics, at a very high level.)

My Conclusion

Smolin makes a compelling but not airtight case for problems with the current understanding of time, but repeatedly while reading the book I felt like Smolin was trying to shoehorn the laws of physics into his own preconceptions of what they should be. We certainly have strong intuitions about time and Smolin's approach involves taking those intuitions more seriously than the mathematical results we've found thus far in physics, which have suggested that time is fluid and that the arrow of time itself is an artifact of entropy. I think this would be useful book for those interested in gaining a deeper understanding of the scientific issues related to time, but I really think that it should only be read alongside Sean Carroll's From Eternity to Here: The Quest for the Ultimate Theory of Time, which presents the more general consensus understanding of time within theoretical physics. Reading Smolin's book alone, without a deep understanding of the physics involved, will very possibly lead the reader to thinking that the flaws are more serious and pervasive than they may actually be.

Disclosure: A review copy was provided by the publisher. For more information, please see our Ethics Policy.