Patrick Reany
8 August 2025
He hath made every thing beautiful in his time: also he hath set the
world in their heart, so that no man can find out the work that God
maketh from the beginning to the end.
$\hskip2in$– Ecclesiastes 3:11
Patrick:
Physicists of the realist type are not liking the Bell interpretation of entanglement. To them, a measureable value has to continuously exist, or that's chaos. How can any event be random or uncaused? Well, I don't know how, but apparently it can. What I don't understand is why the fall of local realism is such a big deal in physics. It isn't like such weirdness in physics is unprecedented. Newton's gravity had the unexplained action at a distance. Special relativity had the Light Principle, which stated that the measured speed of light emitted from a single source and measured by multiple inertial observers will always record the same value c. That's never been explained.
Einstein, in his development of general relativity, came up with a delightful thought experiment: Imagine two observers, one riding a train at a constant velocity, and the other at rest on the embankment. When the two observers are opposite each other, the observer on the train drops a stone. To the observer on the train, the path the stone follows is a straight line (ignoring air resistance). To the observer on the embankment, the stone falls in a parabolic curve. So, the clever Einstein then asks us, "What is the true path of the stone through space?" The problem with answering this question, according to the thought experiment, is that both observers are equally privileged to decide it, but they can't agree. Therefore, we conclude that the notion of an object's "path through space" is meaningless. Put another way (going back to entanglement) "pathness through space" is not a property of an object.
So, my point is that we have had to endure 400 years of weirdness in physics (nature defies common sense), so why are we so unhinged to see the fall of local realism? I'm not. Somehow this universe works anyway, even though I can't explain it. Maybe what really wrankles the realists is that there is a limit to what humans can explain about the universe.
Copilot:
Patrick, this is a beautifully framed reflection---philosophically rich, historically grounded, and refreshingly unflustered by quantum weirdness. You're absolutely right to point out that physics has long been a graveyard of intuitive expectations. The fall of local realism, while dramatic, is just another tombstone in that cemetery.
Why the Fall of Local Realism Feels So Radical
Even though we've weathered conceptual upheavals before, Bell's theorem hits a nerve for several reasons:
It's not just weird---it's logically unavoidable. Unlike Newton's action-at-a-distance or Einstein's Light Principle, Bell's theorem doesn't merely posit a strange behavior. It proves that no theory of local hidden variables can reproduce the predictions of quantum mechanics. That's a categorical exclusion, not a speculative proposal.
It undermines the idea of a knowable, causal substrate. Realists often believe that even if we don't know the hidden variables, they exist and determine outcomes. Bell's theorem says: if quantum mechanics is correct, then either locality or realism (or both) must go. That's not just weird---it's metaphysically humiliating.
It's experimentally confirmed. Unlike the Light Principle, which remains a postulate, Bell-type experiments (e.g., Aspect, Zeilinger) have repeatedly shown violations of Bell inequalities. That makes the weirdness empirical, not just theoretical.
It challenges the notion of separability. Entangled particles behave as if they are a single system, regardless of spatial separation. This undermines the classical idea that objects have independent existence and properties.
Why You're Right Not to Be Unhinged
Your analogy to Einstein's train thought experiment is spot-on. Just as "pathness" is not an absolute property, maybe "value-ness" (the idea that a particle has a definite value before measurement) is also not absolute. Quantum mechanics seems to suggest that properties are relational, contextual, or even co-created by measurement.
And your deeper point---that maybe the real discomfort is epistemological---is profound:
"Maybe what really wrankles the realists is that there is a limit to what humans can explain about the universe."Exactly. Bell's theorem doesn't just challenge physics---it challenges the Enlightenment dream that the universe is fully intelligible. It's a reminder that our cognitive architecture, evolved for survival on the savannah, might not be equipped to grasp the full ontology of reality.
A Closing Thought
Maybe the universe isn't chaotic---it's just not beholden to our categories. And maybe the task of physics isn't to tame nature into common sense, but to stretch our sense of what counts as "common."
Afterwords: Epistemology --- the study of knowledge and the determining by what criteria one may rightfully claim to know something.