From reader Caleb Hansen comes this email:
I hemorrhaged brain cells while reading this article from “Interesting Engineering” and thought to share it with you.
The experts get so giddy when “disproving” objectivity with “the laws of quantum physics” aka: their poor understanding of potency and act.
-Ad Majorem Dei Gloriam
The article is typical breathless science journalism, but it’s useful enough for us to highlight the difference between a thing’s nature and our knowledge of a thing; i.e. between ontology and epistemology.
Wigner’s initial thought experiment was simplistic in principle, starting with a single polarized photon that can have either vertical or horizontal polarization, upon measuring. The laws of quantum mechanics hold that a photon exists in both states of polarization simultaneously, in what’s called superposition. In his thought experiment, Wigner imagined a friend measuring the state of a photon in a different lab, and recording the result while Wigner watched from afar. He has no clue what his friend’s measurement is, and is thus forced to assume that the photon and its measurement are in a state of superposition of every possible outcome for the experiment.
Wigner can say, however, that the “fact” of the superposition’s existence is real. And, strangely, this state of affairs suggests that the measurement can’t have taken place. Obviously, this stands in direct contradiction to Wigner’s friend’s point-of-view, who just measured and recorded the photon’s polarization. He can even call Wigner and tell him the measurement was taken, without revealing the results. This means there are two realities at odds with one another, and “calls into question the objective status of the facts established by the two observers,” explained Proietti and colleagues, in an MIT Technology Review report. And the new research reproduced Wigner’s thought experiment by using entanglement techniques for many particles at the same time.
“Calls into question” is equivalent to “questions raised”, a trope and trick used in journalism to create the illusion of objectivity.
Let that pass, and let’s do Wigner’s Friend Iterated. Wigner’s pal is in the lab doing the experiment, as described. Wigner is thinking about it from afar. Yet here are you, watching Wigner. Your presence created a batch of new superpositions, now including Wigner, and we now have an even farther flight from objective reality.
And so on. If we get enough people to watch each other, nothing can ever exist, all will endlessly exist in superposition and the universe will be an amorphous blob. Clearly, this is an undesirable situation, so we must stop Wigner’s friend from performing his experiment if we want to get on with life.
This paradox, if it can be given so glorified a name, is solved in two ways.
The first accepts the standard fuzzy explanations of “superpositions” and the like, and reminds Wigner that his knowledge of the state of the experiment is not equivalent with the essence or state of the experiment itself. He is not part of it because of or when he thinks of it.
That’s easy to prove, too, using my favorite example of interocitors. These are the communication devices used in This Island Earth. Imagine the interocitor can only have three states (A, B, or C), and must take one of them. Given this, and only this evidence, what is the probability it is in state C? We deduce 1/3.
The interocitor is not in a superposition, it is in a position, but we don’t know what it is. Same with the polarization when Wigner’s friend measured it. Wigner has nothing to do with it. Even stronger, interocitors don’t even exist! They can’t really take superpositions or even positions, not ontologically, not in Reality. But we can still express our uncertainty in their state, as we do with any logic puzzle. Epistemology does not need ontology, if you like.
Incidentally, this is the same first solution (with more detail) given by “The Information Philosopher”, whose article quotes Wigner at length.
The second solution is to suppose, as Hansen, Heisenberg, and Aristotle, do, that objects are composed of potentiality and actuality, and that the idea of “superpositions” express potentiality, a form of Reality. We discussed that at greater length here: Quantum Potency & Probability (links to Ed Feser in here, who explains it better than anybody).
Briefly, it’s easier for these fundamental almost singular objects to be comprised more of potentiality than actuality, to be fuzzier and less concrete. It’s the interactions, or “measurements”, that force objects to take on more actuality—while also retaining some potentiality. Even macros objects have potentiality. You, for instance, while being mostly actual have the potential to be somewhere else.
That’s all too short, so go to the other article for details.
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