Deep Dive: Saying the Quiet Part Out Loud

Physicists have known for 100 years that Quantum Mechanics disproves our conventional ideas about reality. And for 100 years, they've failed to admit what that means

Unless you’ve been living under a rock, by now you’ll have heard that three physicists won the 2022 Nobel Prize in physics for proving Einstein wrong. If you’ve dug into the subject, you may have read that what Alain Aspect, John F. Clauser, and Anton Zeilinger disproved was a seemingly intuitive fact. In a famous, long-running argument with Niels Bohr, Einstein defended the idea that we live in a universe of objects that have stable properties even when nobody’s looking and that don’t influence one another at a speed faster than light. Thanks to the work of Aspect, Clauser, Zeilinger and others, we now know that some or all of these assumptions are untrue. No experiment has yet shown which part, but all attempts to prove that particles communicate at FTL speeds have failed. The strong implication is that a principle basic to science, local realism, is false.

But what does that mean?

If you dig a little deeper, you’ll encounter a kind of shell game. The word entanglement will get thrown around a lot. Quanta Magazine, for instance, blandly states that “Two particles are entangled when together they form one quantum system, regardless of the distance between them.” Okay. Like, we’re supposed to nod sagely at this point and say we understand that. Articles on the subject will then add two more shells and swirl them around: they'll either dig into the logic of the Bell Inequalities and talk about coin-flips and particle pairs; or, they’ll talk about how we couldn’t have quantum computers without entanglement so it’s real. Different articles will swirl the shells differently, but the result is always the same. Nobody will say what the failure of local realism actually, viscerally, means.

Let’s throw the shell game aside and answer the question. In some ways, it’s easy to do. The standard response is that since physics lacks a test that will tell us exactly what’s going on in the heart of QM, the question is not for science to answer. It’s a philosophical issue and speculating about it adds nothing when you’re actually doing the math. “Shut up and calculate” is the rule of the Cophenhagen Interpretation of QM. Aspect, Clauser and Zeilinger actually did experiments to settle some of these questions, so they are not ‘merely’ philosophical. And if the answer they found undermines one of the principles used to define physics’s subject matter, then physics has to have an answer to what’s ‘really real’ or else accept that it invalidates itself. As a strategy, sticking with the one principle that you know is wrong because you don’t know which of the alternatives is right… kind of sucks. If you don’t (and maybe can’t) know which alternative to local realism is right, you can at least ask which is least wrong.

This is important for you and me because QM actually applies at all scales, not just the microscopic. The “classical realm” of macroscopic reality still obeys the laws of QM, and therefore, in reality, no objects exist that have intrinsic properties independent of their context. That includes you. Having an answer to what QM says about reality may not be of any importance to physicists doing the math—but it sure as hell matters to the rest of us.

There are new indications of what that answer might be. Since Unapocalyptic is having some fun building a 21st-century vision of the world whose foundations are firmer than those of the past, I’ll describe that new answer to “what’s real?” and suggest where it fits in our pantheon of new ideas.