Thursday, January 18, 2007

The Goldilocks Enigma

The following is some correspondence I had with Paul Davies on his latest book “The Goldilocks Enigma” (Penguin/Allen Lane 2006)

Dear Paul,
I read your new book “The Goldilocks Enigma” over Christmas with great interest. I certainly found it a very informative and helpful survey of the latest ideas in this fascinating area – so interesting that I actually did an entry in my blog about it. I am particularly fascinated by your ideas on self-referencing necessity being found within the cosmos (I’m a theist so I have always automatically thought of necessity as lying outside the cosmos). Also, I very much feel that there is something in your conjecture that observers are not just incidental to the cosmic set up, but somehow imbue meaning and reality to the cosmos.

Your comments on Young’s slits have prompted me to have another think about this experiment. My understanding of the experiment in fig 32 on page 278 of your book is as follows: The “telescopes” do not detect a fringe pattern even when the object end of the “telescope” is placed in a dark area of the fringe pattern, because the wave from the sighted slit will travel right through the dark node and into the “tube” of the detector where, according to the respective probabilities, the state vector may “collapse” into a “detection state”. In this case, the tubular shape of the detector, if of sufficient aperture, blocks entry of waves from the other slit and so no fringe pattern will be observed. The three dimensional nature of the wave field means that it is effected by the three dimensional configuration of experimental set-ups even if those set-ups change at the last moment. True, the particle wave field is a rather mysterious entity as is the discontinuous swappings of the state vector but I hadn’t up until now thought them to be governed by anything other than conventional “forward” causation (Neglecting the effect of relativity in conjunction with state vector changes). In fact if you increase the wavelength sufficiently, then the wave from the other slit will “get into” the “telescope” and interference patterns will be re-established.

However, what I have said above may be entirely an artifact introduced by my own view of quantum mechanics. I tend to think only in terms of waves and discontinuous changes of the state vector. I don’t think in terms of particles: I see particles as an approximation brought about as a result of cases where the state vector swaps to a localized form, thus giving the impression of “particles”. This perspective on QM tends to expunge teleology. But having said that I must admit that you have prompted me think again here: if one envisages a particle model of reality then the teleological issue does arise. Moreover, one might see in the telescope detector a more complex and therefore “more conscious” piece of apparatus than just a screen. So perhaps our own very sophisticated sentience acts as a “detector” that somehow removes spatial ambiguities even in past states and thus imbues them with greater spatial reality! But then according to the uncertainty principle, less spatial ambiguity is complementary with greater dynamic ambiguity, so the more we are aware of what something is spatially the less aware we are of what it is becoming.

The moral of the story may be that artifacts in one’s perspective have a bearing. As we know, Newtonian dynamics can be developed using the “teleological” looking extremal principles. But, of course, these are mathematically equivalent to the conventional view that sees one event leading to another in sequence without recourse to end results. It is almost as if the choice of interpretation on the meaning of things is ours to make! Thus, perhaps the way we personally interpret the cosmos constitutes a kind of test that sorts out the sheep from the goats! Which are you? Some theists (but not me, I must add!) probably think you are a goat, but then some atheists probably have the same opinion! Can’t win can you?
Tim Reeves

Dear Tim,
Thank you for your thoughtful interpretation of the delayed choice experiment. I believe the teleological component in quantum mechanics is qualitatively quite distinct from the extremal principle of classical mechanics. One can formulate QM in that language too (via Feynman path integrals), but that concerns only the propagation of the wave function. The key point about the delayed choice experiment is the measurement (or collapse of the wave function), at which point the dynamics changes fundamentally. It is not the measurement per se that introduces the teleology, but the choice of which experimental configuration to use - a subtlety that lies at the heart of Wheeler's "meaning circuit." Correct though your observations of aperture diffraction etc. may be, I don't think the specific details of the telescope design and operation are germane to the central issue here. It is more a matter of whether one makes "this" sort of measurement, or "that." Complications with the telescope optics may produce "don't know" answers, but these can be filtered out.

I hate being pigeonholed, so I won't respond to the sheep/goats question.
With regards,

Paul Davies
(The above correspondence has been published with permission)

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