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opens up some fascinating possibilities
on 1 January 2017
Physics has a curious relationship with time. Most laws are time-reversible; famous ones that aren’t, like the Second Law of Thermodynamics, are approximate and emergent from underlying reversibility; in relativity a universal time cannot be defined consistently, and instead provides us with a static space-time. It’s almost as if physics doesn’t believe time exists.
Smolin is having none of that. For him, time is the fundamental property of the universe, whatever else may emerge. We are not flies caught in the amber of a static space-time; time itself is real.
How can he say this, when all the physical theories seem to point in the other direction? His argument is that those theories are local, and cannot be simply extended to apply to the entire universe. Those theories assume that crucial parts of the process must be outside the region they describe. This is what Smolin dubs the traditional Newtonian paradigm of doing “physics in a box”. It rests on some underlying assumptions: (1) the configuration space is timeless; (2) the forces, and hence the laws the system is subject to are timeless. If all the possible states of the system are predefined, and the laws under which the system evolves are predefined, then time does seem to be nothing more than an accounting variable: which of those states the laws say the system is currently occupying. What if the possible states of the entire universe aren’t predefined, because its laws aren’t predefined?
Smolin argues that this Newtonian paradigm, powerful as it is, cannot be extended to provide a theory of the entire universe. It is not a simple task to make a truly universal theory: one that doesn’t just apply to every part of the universe, but that applies to the whole universe at once.
He also argues that our current theories are approximations: physicists pretend that the system inside their box is an isolated system, unaffected by the rest of the universe, and they go to a lot of experimental effort to make that approximation as good as possible. Good approximations make effective theories, but they are only as good as their assumptions (energy ranges, for example). These approximations inevitably break down whenever a theory is extended to encompass the entirety of the universe.
So the timeless nature of isolated, local, approximate theories cannot be taken to imply that the universe itself is timeless.
Having argued that the laws cannot be extended naively to imply a timeless universe, Smolin also argues that there is no reason to assume that the laws themselves are timeless: "To make laws explicable, we must consider them as much a part of the world as the particles they act on. This brings them into the purview of change and causality."
Smolin explicitly links this view with his proposal for an evolutionary universe, where a new universe is born in each black hole, with its laws of physics being a mutation of its parent’s laws, as explained in his earlier work, The Life of the Cosmos. Smolin is a Leibniz fan: as well as following Leibniz’ relational view, he uses the Principle of Sufficient Reason: that everything must have a reason or cause, to show that the laws must also have a cause, an explanation. I wonder: do random mutations to the laws of physics obey this principle? (In passing: I was amused to discover that Smolin was introduced to Leibniz’ ideas by Barbour, but has come to rather different conclusions!)
This mutational view does not mean that Smolin thinks the laws, despite being changeable by mutation, are set at the beginning of the universe, and fixed thereafter. He gives an example of how a quantum system might be free to choose a result in a situation for which there is no precedent. Smolin suggests that this principle of precedence could be subject to experimentation, by preparing some genuinely novel quantum states, and measuring them. I’m not sure of the scope of the system’s freedom, however. What about all those more advanced alien races who have already done these experiments? Do those set precedents? Also, the second time a measurement is done, there is only a single precedent from which to select randomly; this seems to imply determinism.
I like his idea of explicable evolving laws; although I still wonder, does a random choice fit with the principle of sufficient reason? And I must admit, I’m not sure why these “principles”, of sufficient reason, of precedence, of whatnot, are allowed to be timeless and universal, when nothing else is. He mentions the need for meta-laws, laws to say how the laws change, but doesn’t go into this as deeply as I wanted. Are the meta-laws timeless? If so, why? If not, what governs their change? I didn’t get the answers here: Smolin refers his book with philosopher Unger, The Singular Universe and the Reality of Time; maybe the answers will be there. For the time being, I have a few new ideas for student projects: growing cellular automata or graphs with rules that depend on configurations, and only deciding on the rule when a new configuration is seen.
Smolin finishes up with more social concerns. He explains that our notion of the fundamental laws of nature as being timeless leads to a damaging distinction between the timeless natural (hence good and right being changeless) and the ephemeral artificial (hence bad and wrong being change). Rather, everything changes and evolves, and we should embrace that fact.
This is a clearly written and thought-provoking book. It makes plain some issues with physics, and its thesis, about time and change, opens up some fascinating possibilities. Well worth the read.