“Lee Smolin And Status Of Modern Physics” Interview by Jose Boswell

Lee Smolin argues that it is not the timeless laws of universe that controls it but the ‘current moment’ that dictates the future moment. A thought provoking interview( F. Sheikh).

Adam’s Opticks: Hi Lee, central to your thesis as outlined in Time Reborn, and in its recent follow-up The Singular Universe (co-authored with Roberto Mangabeira Unger) [5], is a rejection of the “block universe” interpretation of physics in which timeless laws of nature dictate the history of the universe from beginning to end. Instead, you argue, all that exists is “the present moment” (which is one of a flow of moments). As such, the regularities we observe in nature must emerge from the present state of the universe as opposed to following a mysterious set of laws that exist “out there.” If this is true, you also foresee the possibility that regularities in nature may be open to forms of change and evolution.

My first question is this: Does it make sense to claim that “the present moment is all that exists” if one has to qualify that statement by saying that there is also a “flow of moments?” Does the idea of a flow of time not return us to the block universe? Or at the very least to the idea that the present moment represents the frontier of an ever “growing” or “evolving” block as the cosmologist George Ellis might say?

Lee Smolin: Part of our view is that an aspect of moments, or events, is that they are generative of other moments. A moment is not a static thing, it is an aspect of a process (or visa versa) which generates new moments. The activity of time is a process by which present events bring forth or give rise to the next events.

I studied this idea together with Marina Cortes. We developed a mathematical model of causation from a thick present which we called energetic causal sets [6]. Our thought is that each moment or event may be a parent of future events. A present moment is one that has not yet exhausted or spent its capability to parent new events. There is a thick present of such events. Past events were those that exhausted their potential and so are no longer involved in the process of producing new events, they play no further role and therefore there is no reason to regard them as still existing. (So no to Ellis’s growing block universe.)

AO: Can you help me understand what you mean by a “thick present”? I’m confused because if the present moment is “thick” rather than instantaneous, and may contain events, it seems like you’re defining the present moment as a stretch of time, which looks like a contradiction in terms. Similarly, when you say that the activity of time is a process I’m left thinking that events, activities and processes are all already temporal notions, and so to account for time in those terms seems circular.

LS: I can appreciate your confusion but look, think about it this way: the world is complex. What ever it is, it contains many elements in a complicated network of relations. To say what exists is events in the present does not mean it is one thing. The present is not one simple thing, it is the whole world, therefore it contains a vast complexity and plurality. Of what? Of processes, which are dual to events.

AO: One of your main objections to the idea of eternal laws comes in the form of what you diagnose as the “Cosmological Fallacy” in physics. Your argument runs that the regularities we identify in small subsystems of the universe — laboratories mainly! — ought never to be scaled up to apply to the universe as a whole. You point out that in general we gain confidence in scientific hypotheses by running experiments again and again, and define our laws in terms of what stays the same over the course of many repetitions. But this is obviously impossible at a cosmological scale because the universe only happens once.

But what’s wrong with the idea of cautiously extrapolating from the laws we derive in the lab, and treating them as working hypotheses at the cosmological scale? If they fit the facts and find logical coherence with other parts of physics then great… if not, then they’re falsified and we can move on. As an avowed Popperian yourself, are you not committed to the idea that this is how science works?

In addition, wouldn’t the very idea of “laws that evolve and change” make science impossible? How could we ever confirm or falsify a hypothesis if, at the back of our minds, we always had to contend with the possibility that nature might be changing up on us? Don’t we achieve as much by postulating fixed laws and revising them on the basis of evidence as we might by speculating about evolving laws that would be impossible to confirm or falsify?

LS: To be clear: the Cosmological Fallacy is to scale up the methodology or paradigm of explanation, not the regularities.

Nevertheless, there are several problems with extrapolating the laws that govern small subsystems to the universe as a whole. They are discussed in great detail in the books, but in brief:

  1. Those laws require initial conditions. Normally we vary the initial conditions to test hypotheses as to the laws. But in cosmology we must test simultaneously hypotheses as to the laws and hypotheses as to the initial conditions. This weakens the adequacy of both tests, and hence weakens the falsifiability of the theory.
  2. There is no possible explanation for the choice of laws, nor for the initial conditions, within the standard framework (which we call the Newtonian paradigm).

Regarding your questions about falsifiability, one way to address them is to study specific hypotheses outlined in the books. Cosmological Natural Selection, for instance, is a hypothesis about how the laws may have changed which implies falsifiable predictions. Take the time to work out how that example works and you will have the answer to your question.

Another way to reconcile evolving laws with falsifiability is by paying attention to large hierarchies of time scales. The evolution of laws can be slow in present conditions, or only occur during extreme conditions which are infrequent. On much shorter time scales and far from extreme conditions, the laws can be assumed to be unchanging.