A Conversation with Lee Smolin about Time and Physics
Wednesday, April 17, 2013
What then is time? If no one asks me, I know what it is. If I wish to explain it to him who asks, I do not know. – St. Augustine
Time is like water to a fish. We’re so immersed in it that it’s extremely difficult to even think about except as the entirety of our lived experience. And yet there has been a concerted effort over the last few hundred years to demonstrate that the lived experience of time is ultimately an illusion!
When we get down to brass tacks there seem to be only two things we know with certainty: that there is consciousness, here, now; and that the contents of consciousness change. We call this process of change “time.” Everything other than these two basic features of reality is, literally, inferred, by each of us as we go through our lives moment to moment.
So how can it be that the majority of physicists today believe that time is an illusion? Well, that’s a good story and Lee Smolin’s new book, Time Reborn, delves into this story in detail. Smolin is an American theoretical physicist, a researcher and founder at the Perimeter Institute for Theoretical Physics, in Waterloo, Canada, and an adjunct professor of physics at the University of Waterloo. He’s written a number of previous books, including the 2006 book The Trouble With Physics, an extended critique of string theory and the tendency toward groupthink in physics today.
Smolin’s new book is a cornucopia of big ideas, expressed clearly and compassionately. Smolin truly wants to understand – and to help you, the interested reader, to also understand – the big questions in physics today. And, ultimately, physics is not just for physicists. Physics is, when we get down to it, about the nature of reality and our place in it. Time Reborn is, for these reasons, fundamentally a book of philosophy and even of spirituality – but without any woo woo. Well, maybe a tiny bit of woo right at the end, if we consider discussions of the nature of consciousness to be woo.
Smolin’s is a really rare book: one that is accessible and designed as much for lay readers as it is for physicists, but also a book that proposes new, ground-breaking, theories. More than that, Smolin is suggesting, explicitly and clearly, with fairly convincing arguments, that much of modern physics is either incomplete or wrong. That’s a heavy lift, but he pulls it off well.
I’ve written previously, as a philosopher of science, about my concerns with the common view that time is an illusion, and my own objections to relativity theory. Smolin is politic about it in his book, but he’s also suggesting that the prevailing views about the nature of time and relativity theory need some correction.
Smolin writes like a dream and his tone is spot on for someone who is trying to change a lot of minds about some really big issues. I had the pleasure of interviewing Smolin via email from his home in Toronto, based on an early review copy of his book, which is due out soon.
Why should we care about time anyway? Do different theories of time really impact our lives that much?
How we think about the future and the past determines everything about how we think about our situation as human beings. Are freedom, agency, will, discovery, invention, surprise, genuine? If time is an illusion so are they, and hence so are many of the human qualities we cherish.
Einstein famously stated that the distinction between past, present, and future is a “stubbornly persistent illusion.” Why is it, do you think, that the idea of time being an illusion has such appeal among physicists and regular people alike? Time is, as you write, one of the most real things we know. We can’t, as conscious beings, exist except to exist in time, and everything about our existence suggests that time is real. And yet the idea that time is ultimately an illusion is pervasive.
The first part of the book is aimed at answering that question. It is a good question. One part of the answer is the very common tendency to look down on what is changeable and temporary and admire those things we imagine are timeless. Some of us have a great desire to transcend the time-bound realm, which we experience directly, for fantasies of eternal beauty and truth.
How much should the human experience of time factor into our physics?
The book argues that the experience we have of time flowing from moment into moment is not an illusion but one of the deepest clues we have as to the nature of reality.
Many of our physical laws are said to be “time-reversible” because the equations work equally well when run forwards or backwards. Many people consider these equations and say something like: “Look, time is reversible! Time is an illusion and there is no free will.” But this ignores of course that the universe we live in is entirely uni-directional. We proceed from the present into the future. We remember the past. There is nothing in our universe that proceeds from the present into the past, as far as we know. So these equations, it seems, are wrong in their time-reversibility because they don’t fully describe the world we live in. Why do we so commonly mistake incomplete models of reality for reality itself?
In the book I propose that the time-reversible laws whose action we observe are approximations and that there are more fundamental laws that are time-irreversible. This seems a better explanation for the arrows of time than the standard one, which has to posit that the universe began in a highly improbable initial state.
I won’t try to answer your more general query. We all do our best with the theories and models we have.
A key factor in the commonly held view of time today, that time is an illusion, is the notion that the speed of light is absolute, a postulate of Einstein’s special theory of relativity. The previously held view was that space and time are absolute, but Einstein flipped these assumptions around, making the speed of light universal for all observers - no matter what their motion is in relation to the speed of light. This flipping of assumptions requires that time and space become malleable because the speed of light is of course, by definition, distance (space) divided by time. Setting aside any other debates about relativity theory for the moment, why would the speed of light be absolute? No other speeds are absolute, that is, all other speeds do indeed change in relation to the speed of the observer, so it’s always seemed a rather strange notion to me.
Special relativity works extremely well and the postulate of the invariance or universality of the speed of light is extremely well-tested. It might be wrong in the end but it is an extremely good approximation to reality. This issue is discussed in some detail in the book. We are also working on the website, which will have on-line appendices to give more details of some topics including special relativity. Even if special relativity ultimately is transcended, it is a beautiful experience to comprehend it.
You discuss in your book some of the tension between quantum theory and special relativity, including the fact that quantum theory seems to require some kind of superluminal (faster than light) causation. Doesn’t this evidence, generally described as “nonlocality,” constitute experimental falsification of special relativity? Or at least falsification enough to prompt serious re-thinking of the validity of special relativity?
This is a pretty subtle issue, as discussed in the book. There certainly is a tension between the relativity of simultaneity and non-locality in quantum theory, but it’s not strong enough to add up to a falsification of either side by itself. What is true is that if one demands that there be a deterministic explanation of what causes outcomes of quantum processes, then some physicists, such as Antony Valentini, suggest there is a violation of the relativity of simultaneity. But if you are happy with quantum indeterminacy then there is no problem reconciling them.
Your book is full of delicious iconoclasm, argued sincerely and compassionately - and quite clearly. You argue, essentially, that much of modern physics has been waylaid by bad ideas and theories! I know that it’s always hard to criticize relativity theory and to be simultaneously taken seriously as a physicist or a philosopher. And yet you do tackle this sacred cow - along with many other sacred cows - of modern physics. And you are taken very seriously as a physicist. So do you see a new opening for new ideas that view time as real? Do you sense that your colleagues are perhaps more ready now than in years past for new ideas that go beyond or even contradict special and general relativity?
First, the critique I offer of relativity theory is subtle and embraces the experimental success of Einstein’s special and general theories of relativity. For example, I describe shape dynamics, which is a new way of reconciling the existence of a preferred time that is perceptible at the scale of the universe as a whole, with the validity of the principle of relativity on smaller scales.
You’ve argued for some time that the particular physical laws we know are likely to be a consequence of “cosmological natural selection,” which results from black holes creating new universes, with slightly different laws than the laws in the universe that contains the progenitor black hole. This theory has a number of advantages, which you describe in your new book, particularly compared to alternative theories. However, at a basic level, why would new universes be formed through black holes?
General relativity predicts that time ends inside black holes because the gravitational collapse squeezes matter to infinite density. However, it has long been hypothesized that quantum effects prevent this from happening, causing a “bounce” where the matter stops contracting and starts expanding. This creates a new expanding region of the universe that cannot be seen from outside the black hole. This can be called a new universe. This scenario has a lot of support from the study of mathematical models of quantum effects in the interiors of black holes.
And why would each new universe’s laws change a little, after being born from a black hole?
Because I can make that hypothesis without contradicting anything that is known and its implications are interesting.
You argue that Leibniz’s “principle of sufficient reason” should be a key criterion for good theories. This principles states that everything that is real must have some reason behind it, and thus some equivalent in our theories. But isn’t it rather hard to pin down what qualifies as a “reason”? To be a bit flip, we could argue that the moon is whitish gray because it’s made of cottage cheese, and this is a reason - but it’s just a really bad reason. How do we use this principle in a way that has teeth?
Leibniz means reason in the sense of an explanation for why the universe has one feature when it might have had a different feature. The classic case, which is discussed in the book, is why the universe was not created ten meters to the right or ten minutes earlier. Since nothing in the actual universe would be changed in these scenarios Leibniz concludes there can be no meaning to absolute position or time.
Hendrik Lorentz, a mentor to Einstein, developed the “Lorentz transformations,” the mathematics behind both Einstein’s special relativity and Lorentz’s own theory of relativity. Lorentz’s theory, while considered to be empirically indistinguishable from special relativity, is not widely accepted because it relies on a version of absolute time and space. However, shape dynamics, a theory that you discuss favorably, seems to reinterpret general relativity in a way that mirrors Lorentz’s theory of relativity in that it takes time as fundamental. Can shape dynamics be viewed as a generalization of Lorentzian relativity?
No, because the preferred time in shape dynamics is not absolute, it is determined dynamically as a result of the distribution of matter and fields in the universe.
The general view in the philosophy of science is that new theories that gain acceptance do so not by replacing but by going beyond the old paradigm - Einstein’s general relativity (GR), for example, doesn’t falsify Newtonian gravity, it goes beyond Newton by showing that Newton’s gravitational theory is a limiting case of Einstein’s GR. However, sometimes theories are simply replaced by new ones because there are, of course, an infinite number of possible theories for explaining any given set of data and sometimes new theories are simply better than old theories at explaining the data. For example, Copernicus’s heliocentric view of the solar system has entirely replaced Ptolemy’s geocentric epicycle view because, even though Ptolemy’s model was highly accurate in terms of explaining the data, it makes far more sense to suggest, as Copernicus did, that the Sun is in fact the center of the solar system, for a variety of reasons. You criticize GR in some ways in your book, but you also suggest that much of the theory has merit. Could it be, however, that it’s in need of replacement whole cloth, even though it makes many correct predictions, like Ptolemy’s view of the solar system?
This is the kind of question best answered in retrospect. Let’s see what happens.
I hate to pick on Einstein because he was in so many ways a great man: a great physicist, a great humanitarian, and all around a great human being. But I agree with one of your key points in your book – that Einstein’s view that time is ultimately an illusion is not only wrong but very damagingly wrong, because of the consequences that flow necessarily from the view that time is an illusion: Free will is an illusion and, arguably, human consciousness becomes an illusion, because we seem to have no way to reconcile the view that time is an illusion with the obvious flow of time that is the foundation of human consciousness.
So let me pick a bit more on Einstein and ask you this: You write (p. 56) that Einstein showed that simultaneity is relative. But the conclusion of the relativity of simultaneity flows necessarily from Einstein’s postulates (that the speed of light is absolute and that the laws of nature are relative). So he didn’t really show that simultaneity was relative - he assumed it. What do I have wrong here?
The relativity of simultaneity is a consequence of the two postulates that Einstein proposed and so it is deduced from the postulates. The postulates and their consequences are then checked experimentally and, so far, they hold remarkably well.
You argue against Platonism, the notion that our reality is a corrupted reflection of a timeless perfect reality, and I tend to agree. Yet you also state or imply frequently that laws “guide” physical outcomes. This seems to me to be reverting back to Platonism. Aren’t laws better viewed as human creations based on observed behaviors in the universe around us? And behaviors are simply built in to the constituents of our universe.
Please let’s be careful here. When we human beings hypothesize that a law of nature holds – even temporarily or situationally – we are creating an idea, but we are also making a hypothesis about how nature behaves, whose truth or usefulness has nothing to do with what we know or believe.
Turning to the philosophy of science, I’m curious if you or anyone else has thought about putting the evolution of scientific theories under the spotlight in terms of “memetic” natural selection. There are various theories of how scientific change occurs, but to my knowledge no one has done any detailed study (testing and falsification) of these theories of memetic change in the real world. Could this be done? Would it be useful in order to better understand how scientific progress really occurs?
I recall in graduate school hearing Quine and others discuss evolutionary approaches to epistemology, but I haven’t thought seriously about it since then.
You view the universe as ultimately indeterministic – contrary to the prevailing view that all things are ultimately determined – based essentially on your view that the laws of physics are always changing. How important to your general worldview is it to understand that we, and the universe we live in, are ultimately free to choose our own course?
Personally, I have become fond of this view. I find in it a kind of consolation that goes some distance to replacing what is lost by rejecting both the consolations of religion and the consolations of aspiring to transcendence to a timeless reality.
You venture far beyond physics in your Epilogue, including some musings on the nature of consciousness. You discuss David Chalmers favorably, a well-known panpsychist (this is the view that all matter has some associated mind/subjectivity and vice versa). You also discuss Leibniz, Spinoza, and Peirce, all of whom were also panpsychists of various stripes (see David Skrbina’s Panpsychism in the West). Would you like to take this opportunity to “out” yourself as a panpsychist?
In college I wrote a long essay on the body-mind problem where I invented for myself an idea that I’ve later come to understand is a form of panpsychism. It is expressed on page 270 of Time Reborn as:
The problem of consciousness is an aspect of the question of what the world really is. We don’t know what a rock really is, or an atom, or an electron. We can only observe how they interact with other things and thereby describe their relational properties. Perhaps everything has external and internal aspects. The external properties are those that science can capture and describe — through interactions, in terms of relationships. The internal aspect is the intrinsic essence; it is the reality that is not expressible in the language of interactions and relations. Consciousness, whatever it is, is an aspect of the intrinsic essence of brains.
This is as far as I am willing to go now, on an issue where I don’t know the literature well, and I haven’t thought enough about.
Last, you write that an entirely new approach to physics is needed, and that mathematics needs to be demoted a little in favor of more conceptual approaches to physics, and yet you don’t offer an alternative! Is this your next book?
I disagree. I do discuss alternative approaches to physics along the lines of the principles I propose. Because I am a scientist they are developed as explorations of models and hypotheses. Those discussed in the book include cosmological natural selection, the principle of precedence, and the real ensemble interpretation of quantum theories, as well as the responses to the metalaws dilemma I describe, including the idea of the universality of metalaws and the merging of the concept of state and law. All of these have been the subject of scientific papers which are referenced in the notes.