Superdeterminism part 1

Last year, Sabine Hossenfelder and Tim Palmer published “Rethinking Superdeterminism” (Frontiers in Physics, 8, 139), a startling defence of determinism in quantum physics.  Hossenfelder, who is a physicist with the Frankfurt Institute of Advanced Studies, is well known as a critic of the current direction of physics research. (You can go to her blog, YouTube channel or very readable recent book “Lost in Math” for more, but the book title gives you the general idea.) Palmer is a physics professor at Oxford, a Fellow of the Royal Society and a Dirac Medal winner for climate modelling. If you’re looking for a critique of the conventional wisdom in physics—one that isn’t based on amateur incomprehension or silly mistakes—there aren’t many better people to go to.

Famously (or notoriously) quantum mechanics seems to show that microphysical events are genuinely random.1 Physics can’t predict for certain where particles will go, for example; it can only give you odds. To find out where a particle has actually gone, you have to look.2 This randomness famously offended Einstein, who insisted that “God does not play dice with the Universe”.3

But the great theoretician was defeated by experiment. Starting in 1969, physicists have observed violations of a formula known as Bell’s inequality, which can only happen if determinism is false (or something even weirder is true). Since then the consensus of physicists has been that sometimes, at the fundamental level, shit just happens.

So how do H&P deal with Bell’s inequality? Violations of the inequality only disprove determinism if some—very plausible!—assumptions about the experimental setup are true. Over the years physicists have tried to test those assumptions, and have gone a long way to confirming them. But the theoretical possibility of a loophole remains. 

In particular, the inequality could be violated deterministically if the properties of fundamental particles were correlated with physicists’ decisions about how to set up their experiments to observe those particles. In other words, when physicists set up devices to measure particular properties, they happen to encounter particles whose properties violate the inequality. If they had measured different features of those particles, the inequality wouldn’t have been violated; but if they’d chosen different measurements, they’d have encountered different particles.

Its easy to understand why this loophole hasnt been very popular: for want of a better word, its bizarre. Obviously particles don’t care what measurements physicists have chosen to make; the idea of them sorting themselves into different locations so that only an appropriate subset encounters the experimental apparatus is absurd. And the physicists don’t know what the particle’s properties are until after they’ve set up and run the experiment, so they can’t be making their measurement decisions based on the particles’ properties.  Which suggests that… something… is determining physicists’ decisions for them. Even worse, experiments have shown that whatever that something might be, it must have operated billions of years in the past.

Nonetheless, thats how Hossenfelder and Palmer think determinism is preserved. After that setup, it might be surprising that I think they do an excellent job. Indeed, they’ve convinced me!  Not that superdeterminism is true; the actual physics of superdeterminism is in its early stages. But that it’s a perfectly reasonable approach, and, in fact, less implausible than the alternatives.  Moreover, it seems to me that their approach might shed light on some long-standing philosophical puzzles. 

So: astrology on steroids and why I’m now a one-boxer. [To be continued…]

[1] There are deterministic approaches to fundamental physics besides superdeterminism, but these are weird in other ways. One is the “many worlds” interpretation of QM, where every possible outcome occurs, but in different universes; which seems like an expensive way to avoid probability. A less fantastical approach is whats called pilot-wave mechanics; but like the conventional view this is ”non-local”, which means that events in one place can have effects in distant places instantaneously, breaking the light-speed limit imposed by Relativity. Superdeterminism tries to rescue both determinism and locality.

[2] Of course in everyday life the number of particles involved in events is so huge that the averages rule; ordinary objects behave in predictable ways.

[3]  For the benefit of any Einstein-theism-truthers, his actual words were ‘The theory [QM] produces a good deal but hardly brings us closer to the secret of the Old One. I am at all events convinced that He does not play dice.’