Monday, March 25, 2019

Even Feyerabend accepted Copenhagen

A recent paper quotes a well-known philosopher of science making a point about quantum mechanics in 1962:
If I am correct in this, then all those philosophers who try to solve the quantum riddle by trying to provide an alternative interpretation of the current theory which leaves all laws of this theory unchanged are wasting their time. Those who are not satisfied with the Copenhagen point of view must realize that only a new theory will be capable of satisfying their demands (Feyerabend 1962b, 260, fn 49).
The paper notes that John von Neumann said something similar in 1932.

Feyerabend had a lot of goofy views, but he was right about this.

I mention this because there are a lot of people today who admit that quantum mechanics is quantitatively correct in the sense that it makes very accurate predictions, but argue that the Copenhagen interpretation is flawed, and we must find a better interpretation.

Dream on. It's okay if you prefer QBism or consistent histories or decoherence, as these are just minor variations on Copenhagen. Those who attack Copenhagen as untenable really have a problem with quantum mechanics, and no interpretation is going to make them happy.

This was all recognized by experts in 1932 and by informed outsiders in 1962. Today's Copenhagen deniers are going against what has been conventional wisdom for a long time.


  1. A major point of Copenhagen, however, is that classical description of experimental procedures is essential. The question to ask then is how far that classical description can go, specifically if you adopt Koopman's Hilbert space approach to classical Mechanics, from 1931. Pushing that way of describing experiments as far as it can go makes classical physics much less distinguishable from quantum physics, essentially because the logic becomes that of projections on Hilbert space, for random/quantum fields as well as for classical/quantum mechanics (the differences are almost only technical). So Copenhagen was right: push classical description as hard as possible. I'm pretty sure I've commented similarly here before, but I'm so far out in left field that only a few people are taking me seriously so far, so I won't bother giving you a link to my recently accepted paper in Physica Scripta.

  2. Unless you understand a structure, you at best have a black box from which you assign numbers to its output. Pinning abstract meaningless titles on things and labeling their statistical outcomes as a mechanism isn't a mechanism, it's a behaviorist's sleight of hand (or delusion) which pretends you really don't need to know what the hell is going on inside the mechanism to understand it's functioning as long as you act officious and use clincal sounding jargon.

    Epicycles is what you get when you lose track of what informs your model. Reality isn't math.

    1. I somewhat agree with you, except that I suppose that any new structure sufficiently different from what it replaces will typically not be understood that well at its beginning. As familiarity and facility with its tools develops, however, what at first seem to be, as you say, epicycles, gradually become comfortable in use. QM has become much more comfortable tool in the last 20 years. In any case, only the most unreal of equations have ideal analytic solutions: almost every useful model is built of approximations around those ideals. At some later time, dissatisfaction with details of that comfortable relationship will lead a new generation to want something better, and replacements will again be in the air.
      I also agree that mathematical models are not reality, but models can be better or worse, easier or harder to use for engineering purposes, prettier or not, et cetera. Not a few of our most effective tools can be, figuratively, London Underground maps, and none the worse for it, though I personally think it's good not to fool oneself too much about the nature of what you use.

    2. There is a pretty good article about the problems of those living in their la la 'model land', and the consequences of what this has done to the sciences.

      The site is primarily oriented around climate science, but since modeling is rampant in that area, the discussions and responses to them often revolve around the misuse of computer models.

  3. Dear Roger,

    Please change the string in the main text of the post from ``taht'' to ``that.'' Otherwise, grammatically, it's OK, I think.

    But I don't accept the Copenhagen. Though I respect it a lot.

    Anyway, bye for now...


  4. "Today's Copenhagen deniers"

    Spoken by a true mystic who disagrees with unicity. Sounds like multiple worlds to me.

    "But it is contrary to a deeply rooted faith or intuition, shared by philosophers, physicists, and the proverbial man in the street, that at any point in time there is one and only one state of the universe which is 'true', and with which every true statement about the world must be consistent. In Sec. 27.3 of Griffiths (2002a) this belief is referred to as unicity, and it is what must be abandoned if the histories interpretation of quantum theory is on the right track."

    If you abandon truth claims, you abandon theory altogether. Go meditate and leave our physics alone.

  5. The moon is there, even when you are not looking at it. It does not pop into and out of existence to suit your occasionally peeking at it through the curtains while frantically scribbling rubbish calculations. At no time does ripping the map in two cause the earth to split in half.