Time

Lee Smolin has made a name for himself over the past decade by running against the majority in theoretical physics, including his outright anger at the way the largely untestable string theory and M-Theory have come to dominate physics. In his latest book, The Trouble With Physics, Smolin hammers string theory, and by extension, the notion of a larger multiverse which must be posited to understand how we see the physical laws we see in our universe.

He penned a few thoughts on the idea that time, as posited by many current popular physics theories, is emergent and therefore there must not be fundamental. Smolin argues instead that taking time as fundamental in our view of physical laws is not only natural but necessary in order to make any sense of what we experience. Newtonian laws, he asserts, must be understood as merely local approximations, which fail to explain much of observational cosmology. A few excerpts:

It is apparent that a scenario in which a population of universes evolves, rather than just being a random timeless distribution, requires a notion of time that is real at a level above individual universes. But to understand why the timeless picture fails, we have to go deeper to the foundations of quantum theory. For example, without time, and without the assumption that what exists is the single universe that we observe, it is hard to make sense of statements about probability relevant to what we observe in our universe. Since quantum mechanics is a probabilistic theory, we then run into trouble by trying to extend it to a realm where probability appears to make no sense. A number of authors have attempted to address this question, by proposing ad hoc measures for deducing predictions from ensembles of multiverses. At least up to the present time, none of these appears to be justified by anything other than the need to reproduce what we observe.

The third principle incorporates the notion that time is an aspect of causal relations. A reason for asserting it is that anything that just existed in a moment, without causing or implying an aspect of the state at a future moment, would be gone in the next moment. Things that persist must be thought of as processes leading to newly changed processes. An atom in a moment is a process leading to a different or a changed atom in the next moment.

This alternative metaphysical framework has implications for the nature of physical law. Since nothing is true or real outside of time, there is no possibility of speaking of eternal laws. Laws are regularities that we discover hold for very long stretches of time, but there is no reason for laws to be true timelessly — indeed, there is no way to make sense of that notion. This opens the door to the possibility that laws evolve in time, which is an idea that has been on the table ever since the great American logician Charles Sanders Peirce wrote in 1891 that “To suppose universal laws of nature capable of being apprehended by the mind and yet having no reason for their special forms, but standing inexplicable and irrational, is hardly a justifiable position. Uniformities are precisely the sort of facts that need to be accounted for. Law is par excellence the thing that wants a reason. Now the only possible way of accounting for the laws of nature, and for uniformity in general, is to suppose them results of evolution.”

From this point of view, the notion of transcending our time-bound experiences in order to discover truths that hold timelessly is an unrealizable fantasy. When science succeeds, we do nothing of the sort; what we physicists really do is discover laws that hold in the universe we experience within time. This, I would claim, should be enough; anything beyond that is more a religious urge for transcendence than science.

So, what is physics without a clean separation into laws and initial conditions, and hence, without the notion that there is a space of configurations that exists timelessly? We do not know the full answer to this, but we have a few observations.

First, by discarding the Newtonian schema for cosmology we have much less reason to consider our universe one of many other actual universes. Indeed, we may also be able to dispense with the notion of a vast number of other possible universes, that somehow are never realized. We can imagine instead a notion of law that applies only to the single universe that really exists. We also no longer have any reason to suspect that time is an illusion because, as outlined above, the main arguments from physics for time being emergent and not fundamental come from the misapplication of the Newtonian schema to the universe as a whole.