Ethan Siegel on his Starts With a Bang blog has an interesting review of Paul Halpern’s new book on Einstein and Schrodinger, and their refusal to allow the implications of quantum physics to dissuade them from idea that the universe is strictly deterministic. It’s an interesting post and one that I recommend reading in full. I may well have to read Halpern’s book.
The idea that the universe is fully deterministic is one that many people hold on to tightly, even though science has made that view questionable since the 1920s. Things that happen with a particular quantum particle, such as an electron, can’t be predicted. We can only assign probabilities to particular outcomes. It’s only with populations of vast number of those particles that we begin to be able to make predictions. Determinism appears to be an emergent phenomenon.
Many strict determinists find comfort in the notion that since the uncertainties average out over large enough scales, that we leave quantum uncertainty behind as we go up to the macroscopic scale. And we do, to some extent. It’s why we can use innumerable physical laws to make predictions. But quantum uncertainty does intrude in the macroscopic world. The very fact that we can do experiments that tell us about it is proof of that. The question is to what extent it bleeds into macroscopic reality in natural processes.
Even if it only does so in one in a trillion interactions, within the uncertainty involved in any scientific measurement, in complex dynamic systems, chaos theory shows that that one in a trillion outcome can snowball in time to make those complex dynamic systems unpredictable, even in principle. This means that complex dynamic systems such as the weather, economies, the human mind, and even sufficiently advanced computer systems, may have behavior that will never be predictable, at least not completely.
In my experience, those that do hold on to strict determinism, either don’t understand the implications of quantum mechanics (I won’t accuse them of not understanding quantum mechanics itself since even experts like Richard Feynman never claimed to have that understanding), choose to ignore those implications, or they tightly grasp on to interpretations of quantum mechanics that supposedly preserve determinism, such as the MWI (Many World Interpretation).
While I personally see the MWI as a candidate for reality, I’ve never been particularly impressed by the idea that it preserves determinism. What does it mean to say that reality is deterministic when everything possible happens, but we still can’t predict what we’ll observe, even in principle, along our subjective timeline? I’m not convinced that deserves the name “determinism.” It certainly isn’t very useful for predicting future observations.
Anyway, Siegel’s post is a reminder that we’re all human and fallible, including the geniuses who, sometimes despite themselves, have broken new ground that call into question our most fundamental assumptions about reality. And that reality itself has no obligation to conform to our most ingrained expectations.