A sidebar to “The new shape of reality,” by Anil Ananthaswamy in NewScientist (29 July 2017, paywall) describes a different approach to classical physics – and its implications:
History shows that radical new ways of thinking about reality are well worth grappling with. Take Newton’s laws of motion. Given the position of a particle and all the forces acting on it, you can show deterministically – by describing cause and effect – how it goes from point A to point B. But there is another way to think about the particle’s path. It’s called the principle of least action. It says that a particle will take the path that minimises a quantity called classical action, which is the average value of the particle’s kinetic energy minus its potential energy along the path.
This principle felt weird to minds trained in classical physics. “[No one] thought that particles smelled around all possible paths and took the one that minimised this silly number,” says Jacob Bourjaily of the Niels Bohr Institute in Copenhagen, Denmark. “It’s a very weird starting point for classical physics.” What’s more, the theory appears non-deterministic because a particle’s trajectory isn’t obvious at the onset. Nonetheless, the principle of least action makes the same predictions as Newton’s laws, suggesting that determinism is emergent, and the calculations involved are easier.
So what does it mean to say that determinism is emergent? Does this imply the substrate from which it emerges is, itself, non-deterministic?
I got a feeling I’d need about ten years of training before this would even start to make any sense. But if it makes that math easier, it’s worth exploring.
