Lee Smolin. Time Reborn: From the Crisis in Physics to the Future of the Universe. Allen Lane, 2013.
Two ideas have had wide currency within physics; one is that at that most basic physical processes are time invariant, that is to say that we could not tell whether they were going backwards and forwards in time. Relativity theory argues that time is relative to the observer, there is no more a privileged time than there is a privileged space, and in Minkowski’s interpretation there is a block ‘space time’, in which both past and future in some sense already exist. The second idea is that physics is somehow reducible to mathematics, and that mathematics exists in some timeless Platonic realm. A corollary of the latter is that there exist timeless ‘laws of physics’, which might even exist prior to the universe. Time is thought of as an illusion, or at least as something that is very difficult to account for.
Smolin, who is a theoretical physicist at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, challenges all of that; he argues that time not only exists but that it, rather than space, is fundamental, that there is no transcendent realm of pure mathematics, and that the laws of physics may change with time, as the universe grows in complexity. He sees both quantum mechanics and relativity as merely approximations to some deeper theory (which presumably is in turn an approximation to some deeper theory still, ad infinitum?)
He also argues against the ideas of the multiverse, that beyond the observation horizon, our universe is infinite, or that it will end up in a thermodynamic equilibrium. Instead he argues that universe (or universes) reproduce through black holes and are subject to the principles of natural selection. As he argues that our universe already has had millions of progeny, I am not entirely certain what, in practical terms, the difference between that and the standard multiverse is; perhaps it is mainly that he, I think, sees a common time linking, these universes, whereas in the eternal inflation theory, there are separate times in each universe.
The first part of the book, which summaries, without maths, much of what is known of, and the problems of modern physics, is easier to follow than the sections in which he proposes his new theories, or rather I suppose proto proto theories, even without the maths, they take some following.
It must be left to someone with far more knowledge of physics that I have to assess the validity of Smolin’s ideas. He doesn’t sound like the typical crank, and unlike them works within and in dialogue with his colleagues in the scientific community and acknowledges his ideas could be wrong.
There are a couple of features which seem to be weaknesses; his rejection of the ideas of the infinite universe and thermodynamic equilibrium, on the grounds that they would produce something called a Boltzmann brain, that is a brain springing out of nowhere complete with delusory memories, as result of some random fluctuation, and that would be simpler than a whole universe springing up out of such a fluctuation, so if the universe were infinite, it is much more likely that we would be Boltzmann brains, he aren’t and so qv the universe is finite. This strikes me as nonsense, a BB might arise, but without an external energy source it would die at once, and in any case a quantum fluctuation out of which a universe might grow. (Still not convinced that this sort of statistical argument is nonsense, well how about this, amoebae are a lot more common and a lot simpler than human beings, so is it not much more probable, dear reader that you are an amoeba than a human being!)
A bigger problem with the idea of the endless generation of universes is that it seems to lead to endless regression, like the turtles all the way down. If universes are somehow evolving from generation to generation, there has be a ‘first’ universe with black holes, where did that come from, and whence came time in the first place. One consequence of Smolin’s view is that it outlaws both time travel and precognition.
No an easy read, but worth the effort to look at some really challenging ideas. -- Peter Rogerson