November 19, 2008

"Quantum Stupefaction" pwns Many-Worlds!

This is adapted from my comments to a thread about MW and morality going on at Uncertain Principles as well as a post to sci.physics, alt.fan.rawilson etc:

First, let me explain "quantum suicide" (c.f. quantum immortality, check Wikipedia. Later, I explain something even more perplexing.) If we imagine that only your conscious selves serve as possible carriers of what "you observe" as you split up into "many worlds", then you can do this: Set up the Schrödinger's cat experiment with yourself inside. That means, a radioactive nucleus decaying will cause HCN to flood the chamber, so the decay and you dying from it is a chance event and "not determined" by classical physics. In the many-worlds theory, each moment means the splitting of the universe into other universes representing possible outcomes (such as did or did not decay.) Robert Anton Wilson wrote about Everett-Wheeler MW theory, among other things, in the speculative/fabulist fiction work Schrodinger's Cat Trilogy.

Well, there is always a chance you will survive even after many half-lives of the death-dealing source. Hence there are always some "yous" which can enter some "branches" of MW. Sure, "you" die most of the time but the conscious survivors are the ones saying "Hey, here I still am after all this time." Hence you can never die! If you get into the chamber, you will always "still be there" wondering WTH happened and how you survived millions of half-lives of an unstable nucleus. You can even walk out later, by having a temporary period for the nucleus to be allowed to affect the death-dealing device.

BTW this does not depend on whether consciousness collapses WFs or is "weird" since any sentient being can only notice its survival, right? It is eerily reminiscent of the "multiverse" (that has differing physical constants like alpha) idea of explaining anthropic fine-tuning. However, I think that outcome ruins the whole "proportional" argument that sophistrizing MW advocates put out to imply that each of us has the same "expectation" of outcomes in MW as in ordinary collapse. (BTW I believe "decoherence" is a failed, circular argument for making "apparent" collapse work out OK. Note that use of "apparent" yadda is a warning sign of post-modern psychobabble.)

Note, it is quite possible to build this device. I challenge any supporter of MW to have the balls/etc. to actually get in one. We can even arrange a cash prize waiting outside of $10,000,000 or so, that you can only collect when the temporary danger period is over. Since we might set up a chance of only say 1:10,000,000 of a "you" getting out alive after the danger period, it is an eminently reasonable bet for the rest of us. But since you expect to experience surviving and winning, why not show your "faith" in MW and come out a multi-millionaire to boot? Not only that, but you can see the amazed expressions of the versions of us that see you walk out alive! We'd never live it down, heh.

Well, that's already rather weird, but let's take it further into the twilight zone: Suppose we change the quantum suicide scheme so it doesn't actually kill you if the agent nucleus decays. Let's say, it injects you with something causing total but temporary unconsciousness. Let's call this "quantum stupefaction" ;-) Well, the logic regarding "awareness" should work the same way at first. "I" expect to be one of the tiny minority that remains awake and knows it, for how can that be "experienced" any differently than if most of me actually died?

Yet after awhile, all the other me`s start waking up and there are so many more of them then those who never got put to sleep. So, now what? If "I" can "expect" to be able to say, "How fortunate, I didn't even have to become unconscious" what then takes over the expectations when the others wake up? So what do I really have to "likely" look forward to: not even being knocked out at all, or being put asleep and then waking up? The first option follows the original logic of quantum suicide, but the latter follows what we expect from the total chance of being put asleep and then waking up. Quantum [non-]Suicide was at least a potentially viable if wacky notion, but I think this further refinement makes the whole idea (and by extension, many-worlds "theory") look silly.

8 Comments:

Blogger Cyberax said...

I'm sorry, but your quantum stupefaction itself is quite silly:

"Yet after awhile, all the other me`s start waking up and there are so many more of them then those who never got put to sleep. So, now what? If "I" can "expect" to be able to say, "How fortunate, I didn't even have to become unconscious" what then takes over the expectations when the others wake up?"

MW tells us that there should exist a worldline where "you" won't lose your consciousness. However, the outside world will likely see you knocked unconscious since it's the most probable outcome.

MW is internally consistent. Get over with it. You can't falsify it by such mental experiments.

Oh, and "silliness" also doesn't affect validity of theories.

20/11/08 21:36  
Blogger Neil' said...

First of all Cyberax, we aren't talking about the outside "world" (I guess you mean, "worlds" right?) The issue is what you can expect to find. In the early phase of Experiment 1 (quantum suicide) most of you are dead.
Case 1A: dead > Case 1B: awake from the start

In the early phase of Experiment 2, most of you are anesthetized.
Case 2A: asleep > Case 2B: awake from the start

But either way, your expectation so far is to experience having been awake the whole time, since the more numerous unconscious branches don't contribute to your expectation of "what to experience." So far, the results should be in agreement.

In Experiment 1, that is irreversible and the dead versions drop and stay out of the picture - you should stay awake until E1 is over and you can walk out having never seen the HCN go off (or maybe, as Max Tegmark says, it would have to be sudden to avoid the moments just before death to soak up your expectations.)

But OTOH, in Expt. 2 there is later a phase II where the asleep versions wake up. Then, there are more of them than of your versions that were awake the whole time. Hence your revised expectation is to be one of those that were sleeping and then woke up, which contradicts the original expectation:

Case 2'A: formerly asleep but now awake > Case 2'B: awake from the start

Case 2'A are carriers of observation since they can say "here I am" etc. That removes their irrelevance to observational expectation. They aren't like people who died in "other universes" anymore Now there is a contradiction since the new expectation should be Case 2'A instead of Case 2'B. I hope you can get that now, but can't help much if you don't or won't.

Later I'll have more to say about what's wrong with MW/decoherence. One simple point for now: MW distributes an effectively complete WF amplitude at more than one place, etc. Hey, if there's an entire electron "here" then there isn't also an entire same electron "there" - OK? You can't turn the ~0.7 amplitude at detector A into a "one" and the ~0.7 amplitude at detector B into a "one" as well. It doesn't go anywhere to hide under some physics-psychobabble that the extra integrated squared-amplitude quantity just slips off into the twilight zone.

No, it's got to be either unity at A and zero at B, or vice versa - the same old same old collapse problem. Sorry, MW is not internally consistent IMHO, and besides it involves believing in things (the "other branches") we can't observe.

BTW, you're right that "silliness" doesn't affect validity of theories. But lack of validity or a good argument does make them silly - that was clearly my point. You got the direction of it wrong.

21/11/08 11:45  
Blogger Cyberax said...

I don't understand how subjective expectations have anything to do with the validity of MW.

"Later I'll have more to say about what's wrong with MW/decoherence. One simple point for now: MW distributes an effectively complete WF amplitude at more than one place, etc. Hey, if there's an entire electron "here" then there isn't also an entire same electron "there" - OK?"

Wrong, again. Electron may as well be "there" and "here" with 100% (for simplicity) probability if observers can't communicate (i.e. if they are in different universes). So you can't actually _observe_ electron in two places simultaneously.

You think that an electron in some 'universe' is more significant than this electron in another 'universe'. But it's wrong.

"Sorry, MW is not internally consistent IMHO, and besides it involves believing in things (the "other branches") we can't observe."

MWI _is_ consistent - it's just an _interpretation_. It doesn't currently give any testable predictions, it just interprets existing results.

If you want to disprove it, then give us an experiment with results which can not be interpreted in MWI.

And philosophical arguments do not count.

21/11/08 12:01  
Blogger Neil' said...

Hmmm, what a funny way to defend a theory. You're saying, incredibly, that I should have to disprove the theory, not that supporters have to prove it? That goes against the entire Western, scientific, empirical and logical tradition. No, I don't have to disprove MW any more than I have to disprove flying saucers or gods and devils or the tooth fairy or the "flying spaghetti monster" If you and the other MW fantasists believe in those other universes, then prove it (or sheesh, even just support it with a convincing argument) or quit pretending it should be believed.

I don't think you're right anyway that the results of personal experiments don't have implications. It isn't just a false subjective feeling argument like "I feel like God exists so therefore God exists." This is about what you expect *to happen* in every sense of what you can find out.

BTW it is a matter of physics and not mere philosophy whether we should expect one electron to stay that way and not split into more - don't you believe in mass and charge conservation, etc? And don't confuse a case of multiple universes existing to begin with (with copies of things here in various degrees of similarity), with the case of *splitting* one universe into others, in truth or as metaphor for disconnected waves or mumbojumbo.

21/11/08 12:56  
Blogger Neil' said...

BTW MW is not just an interpretation since its enthusiasts go to great lengths to talk about how interaction with the environment causes decoherence and the appearance of classical physics, etc. Note that I am also picking on decoherence, not just MW.

But if MW is just an interpretation, what good is it, what difference does it make at all? Why even care to support it or say you believe in it, it is "meaningless" isn't it? But since it has the additional problem of postulating something additional to what we can actually find, it can't be a mere "interpretation" after all IMHO. To me, an interpretation is a conceptual scheme for understanding what really does happen, not an excuse to imagine things that we don't even have contact with. And its supporters have to use philosophical arguments (to expand on the known physical facts), so that invalidates it by your word.

21/11/08 13:30  
Blogger Cyberax said...

I'm not defending MWI (in fact, I don't like it). I'm just pointing out mistakes in your logic.

And yes, MWI currently is not a scientific theory since it's not falsifiable. In fact, choosing QM
interpretation right now is just a
matter of personal preference.

That's why I don't like ALL interpretations of QM.

"BTW it is a matter of physics and not mere philosophy whether we should expect one electron to stay that way and not split into more - don't you believe in mass and charge conservation, etc?"

Conservation laws are results of various symmetries (see "Noether theorem") so they work perfectly well along individual world-lines, but are not applicable to the whole 'multiverse'.

21/11/08 14:05  
Blogger Neil' said...

BTW it is not true that MW/aspects/whatever is just "an interpretation." No, it isn't just that, it introduces new aspects of reality. You might say: imagining a WF spreading out and then collapsing isn't really the science, that is also "just an interpretation." If so, you'd be wrong. In the case of the WF, we are at least trying to link together what "we" observe: the emission and detection events. We are presuming that electrons and photons continue to exist between those times. That is a reasonable assumption given some kind of realism, conservation: that things are at least "in existence" when we don't look at them - even if their properties meanwhile, are debatable.

So that leads to the orthodox WF idea, that is great for predicting the chance of getting hits after going through an MZ etc. It also leads to the “disturbing” idea of collapse, but at least it doesn’t mean imagining *more* than we already know should exist: particles being emitted, continuing to exist, and then being “found” one place and not elsewhere.

But OTOH, the MW concept is not just “an interpretation” because it imagines these other branches of WF, or “worlds” or whatever double-talk is employed. Regardless of how you phrase it, saying that the same photon hits D1 AND hits D2 is multiplying into more/other worlds in some very real sense (if you mean it at all, and if you don’t, then why bother to support it at all either?)

23/11/08 12:20  
Blogger easwaran said...

You should look up the work of Hilary Greaves and David Wallace on the problems facing the many-worlds account of quantum mechanics in dealing with the notion of uncertainty. For instance, one article is available here: http://www.rci.rutgers.edu/~hgreaves/papers/pitei.pdf

27/1/09 00:39  

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