dw2

16 November 2008

Schrodinger’s Rabbits

Filed under: books, multiverse, philosophy, quantum mechanics — David Wood @ 9:22 pm

Long before I ever heard of smartphones, or the C++ programming language, or even C, I was intrigued by quantum mechanics. In November 1979, as a sophomore undergraduate, I was fascinated to read an article in the latest edition of the Scientific American: “The Quantum Theory and Reality”, written by French theoretical physicist Bernard d’Espagnat. As recorded in the Wikipedia article on d’Espagnat, this article contains the stunning quote,

The doctrine that the world is made up of objects whose existence is independent of human consciousness turns out to be in conflict with quantum mechanics and with facts established by experiment.

What particularly struck me was the claim that “facts established by experiment” were at odds with common-sense ideas about reality. These experiments involved the now-famous “correlation at a distance” experiments inspired by a paper originally authored in 1935 by Albert Einstein and two co-workers: Boris Podolsky and Nathan Rosen. The initials of the authors – EPR – became synonymous with these experiments. Particularly when viewed through the analysis of John Bell, who devised some surprisingly counter-intuitive inequalities applicable to correlations between results in EPR experiments, these experiments seemed to defy all explanation.

Early in 1980, Professor Mary Hesse of the History and Philosophy of Science department at Cambridge, gave one of the then-frequent lunchtime presentations on mathematical topics, to students (like me) sufficiently interested in such topics to give up their free time in pursuit of greater understanding of mathematics. Prof Hesse chose the philosophical problems of quantum mechanics as her subject for the meeting. I listened carefully, to find out if there were any good rebuttals to the claims made by d’Espagnat. My conclusion was that the whole area was decidedly weird. As months passed, I also asked various maths lecturers about this – but their advice was generally not to think about these questions!

Several years later, I chose Philosophy of Science as the area for my postgraduate studies, with a particular focus on trying to make sense of quantum mechanics. During that time, I even made my first trip to Finland – not to visit Nokia (since I had never heard of them at that time), but to attend a conference in 1985 in pictureseque Joensuu. It was a conference to commemorate 50 years since the publication of the EPR paper. Nathan Rosen, then aged 76, was the guest of honour.

The more I studied the philosophical problems of quantum mechanics, the more I came to respect what initially seemed to be the weirdest and most unlikely solution of all. This is the so-called “Many worlds” interpretation (though, as it turns out, the name is misleading):

  • Originally proposed by Hugh Everett III, in 1957;
  • It refuses to introduce some kind of demarcation between the quantum realm, where superposition (“wavelike behaviour”) is allowed, and the classical realm, where things need to be more definite;
  • Instead, it takes very seriously the idea that macroscopically large objects also spread out over a range of diverse states – in a so-called quantum superposition;
  • This includes the shocking and apparently absurd notion that even we humans end up (all the time) in a superposition of different states;
  • For example, although I subjectively feel, as I type these words now, that this is the unique instance of myself, there are countless other instances of myself, spread out in a wider multiverse, all having diverged from this particular instance as a result of cascading quantum interactions;
  • In some of these other instances, I am employed by companies other than Symbian (my employer for the last ten years in this instance); in yet other instances, Symbian was never created, or I remained in academia instead of joining the world of business, or human civilisation was destroyed when the Cuban missile crisis went wrong, or the values of physical constants were not capable of giving rise to complex mater – and so on.

If objections to this idea come to your mind, it’s very likely that the same objections came to my mind during the years I pursued my postgraduate studies. For example, to the objection “why don’t we feel ourselves splitting”, comes the reply given by Hugh Everett himself:

Well, Copernicus made the analysis that the Earth was moving around the sun, undoing thousands of years of belief that the sun was going around the Earth, and people asked him, If the Earth is moving around the sun, then why don’t I feel the Earth move?

In time, I deprioritised my postgraduate studies, to take a series of jobs, first as a part-time university supervisor, then as a maths tutor at a sixth form college, and then (from 1988) as a software engineer. But occasionally, I come across a link that re-awakens my fascination with quantum theory and the many worlds interpretation. Recently, there have been quite a lot of these links:

  • The son of Hugh Everett is a reasonably famous singer and guitarist in his own right – Mark Everett, also sometimes known as “Mr E” or just “E”;
  • Mark Everett has just released an autobiography “Things the Grandchildren Should Know” which addresses his growing awareness of his father’s remarkable thinking (Hugh Everett died, of a heart attack, in 1982, when Mark was just 19);
  • There has also been a PBS documentary on this same topic, “Parallel worlds, parallel lives“, which has generated considerable media interest (such as this piece in the Scientific American);
  • Coincidentally, various conferences have taken place in the last year or so, commemorating the fiftieth anniversary of Everett’s original thesis;
  • For example, several people I remember from my own postgraduate studies days took part in a conference “Everett at 50” at Oxford.

With this growing abundance of material about Everett’s ideas, I’d like to highlight what I believe to be among the best book on the subject. It’s “Schrodinger’s Rabbits: The Many Worlds of Quantum“, written by Colin Bruce. It deserves to be a lot better known:

  • The author has a pleasant writing style, mixing in detective story writing and references to science fiction stories, with analysis of philosophical ideas;
  • There’s no complex maths to surmount – though the reader will have to think carefully, going through various passages (the effort is worth it!);
  • Unlike many books which seem to repeat the same few themes spread over many chapters, each chapter in this book introduces important new concepts – which is another reason why it’s rewarding to read it;
  • The book highlights some significant difficulties faced by the many worlds theories, but still (in my view) makes it clear that these theories are more likely to be true than false.

Alternatively, for a book that is even wider in its scope (though less convincing in some of its arguments), try “The Fabric of Reality: The Science of Parallel Universes and Its Implications” by David Deutsch – who in addition to breaking new ground in thinking about the philosophy of quantum mechanics, also happens to be a pioneer of the theory of quantum computing.

Finally, for a book that generally leaves readers in no doubt that any “common sense” interpretation of quantum mechanics fails, take a look at the stunningly well-written “Quantum Reality: Beyond the New Physics” by Nick Herbert.

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7 Comments »

  1. Hi David,

    While your first love was Mathematics, mine was Physics. I have to say I’ve always thought that Many Worlds was a clear case for applying Occam’s razor, indeed if you read the wikipedia entry it almost exactly fits the latin versions (although of course we could argue about necessity).

    Personally I’ve always liked the way the Copenhagen Interpretation brings the observer back into science after it was carefully removed in a deal with the Church back in the time of Descartes. Philosophically I’ve always been more inclined towards the “consciousness causes collapse” end of the spectrum but with the caveat that until we’ve got some concrete tests to make it’s all just metaphysics.

    I actually still think we’ll discover a deeper theory that explains quantum mechanics a little better, whether it be superstrings or something else. One really interesting hint that it must exist is a book called Physics from Fisher Information, which “derives” many of the most famous equations of modern science from a pure information theoretic treatment of the problem domains (and in a very simple way – has to be read to be believed).

    Mark

    Comment by m_p_wilcox — 17 November 2008 @ 8:44 am

  2. Hi Mark,

    >Personally I've always liked the way the Copenhagen Interpretation…

    The first problem with “the” Copenhagen interpretation is the fact that its supporters all disagree with each other on what it means – Bohr, Heisenberg, Pauli, von Neumann, etc.

    >Philosophically I've always been more inclined towards the "consciousness causes collapse" end of the spectrum

    That was my starting point too. But the EPR Bell analysis shows that any such collapse would have to be a nonlocal effect – happening over arbitrarily large separations of space.

    >I actually still think we'll discover a deeper theory that explains quantum mechanics a little better, whether it be superstrings or something else.

    I’m sure that’s true. However, the EPR Bell analysis shows that the philosophical problems of potential non-locality (or non-reality) will have to remain, in any successor theory that replaces quantum mechanics.

    >One really interesting hint that it must exist is a book called Physics from Fisher Information, which "derives" many of the most famous equations of modern science from a pure information theoretic treatment of the problem domains (and in a very simple way – has to be read to be believed).

    Thanks for the pointer – I’ll look out for that book!

    However, as an aside, I’ve grown sceptical of the claims of similar books, to derive modern physics from a small number of simpler axioms. To be more convincing, such a derivation ought to come up with novel predictions, which can then be put to the test.

    // dw2-0

    Comment by David Wood — 17 November 2008 @ 8:57 am

  3. Hi David,

    >The first problem with "the" Copenhagen interpretation is the fact that its supporters all disagree with each other on what it means – Bohr, Heisenberg, Pauli, von Neumann, etc.

    Absolutely, it’s more a classification for a group of similar but incompatible interpretations. They all have the fundamental element of observer interaction though.

    >But the EPR Bell analysis shows that any such collapse would have to be a nonlocal effect – happening over arbitrarily large separations of space.

    I know, I don’t have any problem with this though, it’s just telling us that reality is non-local. Just because our perceptual filters tend to tell us otherwise doesn’t mean they’re right! There are a lot of things not widely believed (but still true) that clearly demonstrate that consciousness is non-local. Remote viewing is probably the least contentious. It has been demonstrated in many labs (although the skeptics always find ways to suggest the experiments are flawed) and used by military/security organisations all over world. You can read first-hand accounts written by people that did this for a living successfully for many years.

    There’s an interesting chap called Dean Radin in the parapsychology field who’s as hard-nosed a scientist as you’ll find. He won’t believe anything that can’t be proved by experiment. He’s written some very interesting stuff that will need to be explained by any physics that replaces quantum mechanics. The non-locality helps not hinders in this case.

    My take on the results in “Physics from Fisher Information” is that our current “laws” of Physics are simply a by-product of the assumptions we make and the way we choose to measure things (this is not a conclusion drawn by the authors). This is not to take anything away from the fantastically accurate models of the world that we’ve built. I think the models are just hard to comprehend because we’re starting from the wrong assumptions. Of course I have no idea what better assumptions would be!

    Mark

    Comment by m_p_wilcox — 20 November 2008 @ 12:20 pm

  4. Hi Mark,

    >"There are a lot of things not widely believed (but still true) that clearly demonstrate that consciousness is non-local. Remote viewing is probably the least contentious. It has been demonstrated in many labs (although the skeptics always find ways to suggest the experiments are flawed) and used by military/security organisations all over world…"

    I used to share this belief in the non-locality of consciousness. The remote viewing and ganzfeld experiments seemed to me, for a while, the strongest evidence in favour of such a view.

    During my student days, I was particularly impressed by the results from the ganzfeld experiments in the Cambridge University labs of Carl Sargent, who I briefly got to know at the time.

    It was therefore a blow to me when someone else I slightly knew at the time, Susan Blackmore (nowadays probably best known for her work on memetics, but at the time renowned as a youthful psychic investigator) identified lots of issues with the setup of these particular experiments.

    As Wikipedia reports, “[Sargent] stopped working in parapsychology after this and did not respond “in a timely fashion” when the Council of the Parapsychological Association asked for his data and so his membership of said organization was allowed to lapse.”

    I read some more of Blackmore’s writing (especially “Beyond the body“, which made a big impact on me) and (to cut a long story short) I started to accept that, in fact, there is no good evidence in favour of consciousness being non-local (or other worldly).

    >"There's an interesting chap called Dean Radin in the parapsychology field who's as hard-nosed a scientist as you'll find. He won't believe anything that can't be proved by experiment."

    Sorry, I’m not convinced that Dean Radin is a hard-nosed scientist. See eg this review.

    // dw2-0

    Comment by David Wood — 21 November 2008 @ 11:31 pm

  5. Hi David,

    Well, I've read Susan Blackmore and have great respect for her memetics work. I find her work on the skeptic side to be as biased against parapsychology as the most dedicated proponents in it's favour.

    Personally, having read Dean Radin's books I find him very reasonable (despite obviously having a bias, like all researchers in a specific field – if you didn't believe there was any value in it you wouldn't work on it). He admits he doesn't know what's going on, just that there is SOMETHING to be explained and, like most scientists, he advances tentative theories.

    I've found the involvement of James Randi in various de-bunkings to be particularly biased and blinkered. If you read, for example, the case of Jacques Benveniste, who was probably on course for a Nobel Prize for his earlier work, and Randi's involvement in his fall from favour from all sides you'll probably find it hard to disagree.

    Smears that point out associations with individuals with particular religous, mystic or philosophical beliefs always jar with me, since otherwise we should discount geniuses like Isaac Newton & Nikola Tesla (and probably a majority of our greatest thinkers throughout history – although they do say genius is close to madness…).

    When it comes down to it though, there's nothing that beats unexplained personal experience and that of family and friends. I've had out-of-body experiences, astonishingly successful experiments with dowsing to find hidden items or water and (shared with my father) the ability to detect the exact location of another persons injury or illness from 1 metre away. To me, these completely defy the skeptics claims. For people that haven't had such experiences I can see that it seems far more reasonable to apply Occam's Razor to non-local consciousness.

    I still don't rule out the possibility that something else is going on (and in fact have also intensively studied the sub-conscious, hypnosis, altered states of consciousness and the limits of perception – looking for explanations) but, at the moment at least, I find non-local consciousness effects the most probable form of explanation.

    Mark

    Comment by m_p_wilcox — 22 November 2008 @ 11:45 am

  6. Bell’s theorem isn’t necessarily as conclusive as first appears:

    http://www.mathpages.com/rr/s9-06/9-06.htm

    Comment by irf520 — 30 December 2008 @ 1:53 am

  7. Hi irf520,

    >"Bell's theorem isn't necessarily as conclusive as first appears: link

    I’m sorry, but I think the linked extract is weak and unconvincing.

    First, it wastes a lot of time on what is now a historical irrelevancy: von Neumann’s 1932 argument against hidden variables. The bite of the modern anti hidden variable arguments is much more severe than the case for von Neumann’s 1932 argument (clever though that argument was, for its time).

    Second, the extract grossly misses the point when it tries to poke fun at Bell by seeking to summarise Bell’s position as follows:

    “Bell understood the necessity of assuming free acausal events for his derivation, but since this amounts to assuming precisely that which he was trying to prove, we must acknowledge that the significance of Bell’s inequalities is less clear than many people originally believed.”

    Wrong. The underlying assumption Bell was making in this part of his proof is that of independence, rather than non-determinism. Supporters of Bell’s analysis are happy to concede that their decisions during experiments (for example, whether to measure variable A or variable B) might not be as mentally determined as an experimenter might like to think. The experimenter may think the decision happens by free will, whereas in reality there are likely physical determinants of that decision. But the point is that, to defeat Bell’s analysis, you have to suppose some kind of conspiracy between, on the one hand, the factors determining this choice of what variable to measure, and on the other hand, other widely diverse elements of the overall setup.

    A later article by Bell (published in 1987) makes it clear what kind of things would need to be caught up in this wider conspiracy. In this article, Bell notes that the choice of which variable to measure could be determined “by apparently random radioactive devices, housed in separate boxes and thickly shielded, or by Swiss national lottery machines, or by elaborate computer programs, or by apparently free-willed experimental physicists”.

    For more discussion of this point, I recommend the article by Peter Lewis, “Conspiracy Theories of Quantum Mechanics“.

    // dw2-0

    Comment by David Wood — 30 December 2008 @ 3:06 pm


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