Very interesting seminar last night by Guy Blaylock  on the multiple worlds interpretation of quantum physics. Nice example of the principle that a given set of empirical observations is always subject to multiple interpretations , ie that there is always a perspectival or "subjective" element in scientific stories . And an interesting dissection of reasons for preferring one or another several stories, a dissection that might in turn lead to some new stories.
As Guy neatly pointed out, the "traditional" interpretation of quantum physics has several "weirdnesses," with one more coming up in discussion:
- non-realism (things are different when observed than when not observed)
- non-determinism (knowing everything there is to know now does not suffice to predict the future
- non-locality (there are phenomena that cannot be accounted for by immediate interactions between near by things)
- non-reversibility (one can't deduce the past from the present)
What struck me as interesting is that these are all "weirdnesses" for many physicists but not for all people and very much not for this particular neurobiologist. Of course things are different when observed than when not observed; the brain constructs what we see , what we see isn't actually out there at all. Of course knowing everything there is to know does not suffice to predict the future; the brain uses a degree of internal indeterminacy  to generate its "best guesses" about what's out there. Of course there are phenomena that cannot be accounted for by immediate interactions between near by things; things remote from one another in space and time are related by their histories as well as by stories the brain makes up about them. And of course one can't deduce the past from the present; the brain uses threshholding in its processing and so inevitably discards information about the past in constructing the present.
Several interesting questions follow from this, for me at least. Guy suggested that the many worlds intepretation originates in, and draws much of its current appeal for some physicists from, a desire to do away with this these weirdnesses (while creating new ones). And so the most obvious question: why would physicists (at least some of them) prefer stories that have realist, determinist, local, and reversible characteristics? What about their experiences/brains makes these sorts of stories more appealing/aesthetic? There is also a subtler version of this question: what is the relation among these four characteristics? are they independent of one another or do they all relate to one (or more) deeper preferences?
A second set of questions has to do more specifically with the relation between the brain and quantum physics. Guy noted that the multiple words interpretation does away with the "measurement problem" of the traditional intepretation of quantum physics, the lack of a good theory of wave function collapse and the ambiguity about who/what is an "observer" adequate to produce that collapse. But neurobiology provides a perfectly good explanation of both wave function superposition and its collapse: the state of Schrodinger's cat is in fact, for something with a brain like outselves, uncertain (it is neither alive nor dead) unless and until we look into the box. Arguably, the superposition and its collapse aren't going on "out there" but rather in our brains, "in here."
This line of thinking might also help to do away with the weirdness created by the multiple world interpretation of quantum mechanics: where are all those extra worlds? is there space for them in the universe and why don't we see them? Perhaps they're all in the brain, constructions of the brain? And we can't all see them because only some of us have constructed them?
Multiple interpretations = multiple worlds? Physics is as much about what's "in here" as it is about what's "out there"? And because of what's in here, some of us would prefer local, reversible, deterministic, "real" worlds, while others of us enjoy the expansiveness of other worlds? That opens some new space to think more about.