Einstein’s Dice and Schrödinger’s Cat

I’ve written a review for the Wall Street Journal of Paul Halpern’s new book
Einstein’s Dice and Schrödinger’s Cat (It’s here, unfortunately now behind a paywall [commenter advice is try googling “The Half-life of physicists” and using the Google link]).
I liked the book quite a bit, and learned many things about some history I already thought I knew well. The most dramatic section of the book is the story of the 1947 trouble between Schrodinger and Einstein caused by Schrödinger’s publicity campaign for a supposed breakthrough in the search for a unified theory, and Halpern writes about that here.

The title of the book emphasizes their misgivings about the probabilistic interpretation of quantum mechanics, and describes how Schrödinger’s cat arose out of discussions with Einstein. More of the book though is actually about their efforts to generalize GR and find a unified geometrical theory of gravity and electromagnetism. This began almost as soon as the field equations for GR were in place (1915). The book’s stories of media hype for bad ideas, involving physicists given rock-star academic positions at institutes set up for them make clear that some contemporary problems go back much further than I’d ever realized.

Einstein’s later work is, for good reason, dismissed as misguided, since it ignored quantum theory. He and Schrödinger did however have good reasons for skepticism about the Copenhagen interpretation of quantum mechanics. The measurement problem has turned out to be a very subtle one, with the cat experiment a very good way of making clear the problem. Their enthusiasm for ideas about unification that weren’t working was also way ahead of their time…

Update: For some other reviews of the book, see Jennifer Ouellette in the New York Times, and Denis Weaire in Physics World.

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15 Responses to Einstein’s Dice and Schrödinger’s Cat

  1. cthulhu says:

    Have to add this one to my list…FYI, if you search with Google for the exact title of a WSJ article, you get a link that bypasses the paywall.

  2. Peter Woit says:

    cthulhu,
    Thanks. It does seem that the Google link behaves differently.

  3. Richard Gaylord says:

    this is IMO a really terrible book unless you’re into reading about the randiness of Einstein and Schrodinger. the scientific content is close to zero. it was a major dissappointment to me since i thought his “The Great Beyond” was quite good.

  4. Peter Woit says:

    Richard Gaylord,

    I strongly disagree. There’s relatively little in the book about Einstein’s romantic life, and Schrodinger’s is a significant part of the story, since one of the main reasons he ended up in Dublin instead of Oxford or Princeton is that he essentially had two wives.

    It’s true there’s little in the book about the details of the generalizations of GR that Einstein and Schrodinger were working on. That’s a very technical subject, and those ideas don’t seem to go anywhere, so it’s not an unreasonable choice to not focus on it.

  5. john McAllison says:

    Peter,

    in your review you say:

    “While most of their colleagues were moving on to the study of such quantum-field theories, the two of them resisted, feeling to different degrees that such theories were likely inherently flawed.”

    I can’t help feeling that this sounds a little like you with your attitude towards String Theory 😉 Nowadays, any respectable graduate course in HEP will include this.

  6. Peter Woit says:

    John McAllison,
    I think there are a few obvious differences between me and Einstein/Schrodinger (as well as between QED and string theory…).

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  8. Kenneth Vatz says:

    First I read the review in today’s Times Book Review by the “popular science” writer, Jennifer Ouellette, who says there is little that’s new in the book. Then I read your review in the WSJ (by Googling it, as described), and decided I would get it.

    But what really influenced me, as a lay reader, to ignore Ouellette altogether was this excerpt from the end of her review:

    “Mainstream physics left [Einstein] behind as the Standard Model of particle physics took shape, and the mathematical approaches once explored by Einstein and Schrödinger have long since given way to string theory and loop quantum gravity, two of the most promising candidates for quantum gravity.”

    I’m not sure if Ouellette reads your blog.

  9. Peter Woit says:

    Kenneth Vatz,
    I’ve added a link to the New York Times review and to one at Physics World.

    I don’t actually disagree all that much with Ouellette’s review. It’s a fact that much of the story of Einstein and Schrodinger is “well-traveled historical ground”, and it’s very hard for anyone to come up with a new take on it. Halpern’s decision to focus on their interactions in their later years is a new take, and that’s where he has new material. For the rest of the story, there are many other better sources, ones it’s hard for anyone to compete with.

    I’m pretty sure Ouellette has heard of my point of view on string theory (maybe she was even in the audience when Sean Carroll and I debated this once..). Saying that the failed ideas of Einstein and Schrodinger have been replaced by string theory etc. doesn’t necessarily make much of a positive claim for string theory, even with the “promising”. If you read Halpern’s book, you’ll see that he also probably has a more positive take on string theory than I do.

  10. Anonymous says:

    My understanding of Einstein’s motivations (which might well be wrong) is that he was trying to obtain a theory from which quantum mechanics would naturally emerge, and so “quantization” would not be the starting point of such a theory.

    From the standard biography by Pais :

    “He was looking for a unified field theory, but to him that concept meant something different from what it meant and means to everyone else. He demanded that the theory shall be strictly causal that it shall unify gravitation and electromagnetism, that the particles of physics shall emerge as special solutions of the general field equations, and that the quantum postulates shall be a consequence of the general field quations.”
    [p. 465 in the OUP edition]

    In addition, he had a favoured mathematical idea for reaching this end : overdetermination of systems of partial differential equations [mentioned in Pais].

    From another (excellent) articulation of Einstein’s position :

    https://www.marxists.org/reference/archive/einstein/works/1940s/reply.htm

    “Assuming the success of efforts to accomplish a complete physical description, the statistical quantum theory would, within the framework of future physics, take an approximately analogous position to the statistical mechanics within the framework of classical mechanics. I am rather firmly convinced that the development of theoretical physics will be of this type; but the path will be lengthy and difficult.”

    So he had a fairly clear and not entirely unreasonable notion of what he was looking for, and how he would go about it. It’s just that he didn’t succeed.

    And neither String Theory, nor Loop Quantum Gravity are – in this sense – attempts towards fulfilling Einstein’s “dream”.

    I can stand corrected on anything I’ve said here.

  11. Phil Harmsworth says:

    Richard Gaylord,
    If you’re interested in the technical details, the Pais biography of Einstein provides an overview.

    Pais also explains that, far from ‘ignoring quantum theory’, as Peter stated, Einstein initially thought it was possible to derive its features without invoking probabilities at a fundamental level. As Pais makes clear, to some extent he wavered in this conviction towards the end of his life.

  12. Richard Gaylord says:

    sorry for sendingg so many comments but i wanted to add the following:

    Einstein quote: “I consider it quite possible that physics cannot be based on the field concept, that is, on continuous structures. Then nothing remains of my entire castle in the sky, including the theory of gravitation, but also nothing of the rest of modern physics.” (In a letter to a friend in 1954, the year before he died.)

    and to get a good understanding of Einstein’s research program in his post GR period, see the book “Einstein’s Unification”.

    Also, recently there have been a number of very interesting articles on arXiv (history and philosphy of physics) describing Einstein’s methodology in seeking a cosmological model based on GR.

    finally, i’d like to read a discussion of the causal net approach to spacetime proposed by Raphael Sorkin and taken up (without attribution) and modified by Stephen Wolfram who considers the concept of spacetime itself to be misguided.

  13. I found the Peter Woit review absorbing and it interested me in the book.

    Regards,
    Mike

  14. Oldster says:

    Anonymous: I think you covered your points pretty well. I was never sure what Einstein thought overdetermined PDE’s would quantize however. Somehow, I got the impression he might have been thinking more about quantization of charge or such there, but that’s merely my speculation, not something I recall him writing down. But the quote you gave from Pais may be consistent with that …

  15. Cormac says:

    Good review Peter, well written and interesting. Given their kerfuffle concerning the possible theft of ideas in the 1940s, I find it surprising that Einstein never pointed out that the Schroedinger cat paradox was an extension of his gunpowder argument, outlined in a letter to Schroedinger…does the author touch on this?

    I hope the author mentions that Schrodeinger wrote two excellent early books on GR and cosmology, this is not widely known.
    Fun fact. Did you know that Schroedinger published a short paper on relativistic cosmology way back in 1918, asking this: why not put the cosmic constant on the RHS of the field equations? And why a constant, might it not be a variable? [Yes, he really did suggest this. Einstein’s reply was that, if constant, putting the cc on the RHS made no difference (not quite true): if not constant, one would have to hypothesize a time variation and he had “no wish to enter this thicket of hypotheses” !
    Such little titbits make historical books interesting..

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