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Quantum Physics Revealed As Non-Mysterious

16 points by hhm 18y ago

lg 18y ago
This bothers me because it pretends that it's railing against an unenlightened status quo, and it isn't. Philosophers of physics considered, and largely rejected, the many-worlds interpretation because, if quantum events result in every possible outcome occurring in some world, and our consciousness ends up in one of them by some chancy process, then there's no reason why we observe some events with higher probabilities than others. But we do, and many-worlds doesn't explain that. The author talks around this by saying that, yes, these probabilities are very mysterious, indeed. Well, there are other interpretations under which they're not. Such as a) the many flavors of GRW (a collapse theory), b) the bohmian interpretation (waves + particles), and c) the many-minds interpretation (anti-realist and therefore the most out-there of the three). Those are all pretty much consistent with QM, or there's a good reason to believe that they'll be beaten into a form that is so consistent (e.g. tumulka's relativized version of GRW-flash, but that's outside the scope of a HN comment).
- rms 18y ago
  http://en.wikipedia.org/wiki/Many-minds_interpretation http://en.wikipedia.org/wiki/Many-minds_interpretation
  - lg 18y ago
    Well, I mentioned many-minds because a couple guys actually do take it seriously, even though most don't. But I think this entry is a little off when they say that many-minds "extends" many-worlds. On the many-minds theory, there's only one world, which is pretty different on the face of it. And since there are an infinite number of minds, if you get an 80-20 likelihood on values of some observable, then 80% of your minds will go to one and 20% to the other, which is very different from how many-worlds approaches splitting on outcomes.
- hhm 18y ago
  I don't know much about this, but wouldn't it be a lot more probable to be in a world of those many where the probabilities of events are distributed in a reasonable way, than to be in another world where the distribution of probabilities is out of the standard? (that is, there are many possible time lines, but the distribution of probabilities would indicate that there would be a lot more time lines for probable events, than for improbable events, so it's easier for us to be in a probable time line than in an improbable one). Or am I understanding something wrong? (Sorry for my English, I'm not a native English speaker)
  - lg 18y ago
    The problem with many-worlds is that there aren't more timelines for probable events. If every outcome occurs in some world, then for some event with two possible outcomes, there ends up being two of you; say, Lefty and Righty, one in each world. So there's no sense in saying "I'll probably end up being Lefty, since his outcome was more reasonable," because you'll end up being both of them.
    - hhm 18y ago
      But I'm conscious of only one of only being Lefty, or not? If that's true, then for me at least, that behaves like a separate timeline of all others. That's what I meant in the post above: we are only conscious on what happens on a very reasonable timeline. Can this be like this?
      - lg 18y ago
        right, but Righty is conscious of being Righty, and if his outcome was highly unlikely, then he must be wondering why his world is so unreasonable. And since he's just as much you as Lefty is, post-event, it's not true that you're only conscious of what happens on a reasonable timeline.
        hhm 18y ago
        But... Righty could ask why his world is unreasonable, but actually, being Righty is very improbable, so if we find the world to be actually very reasonable, it's because it's more probable to be Lefty than to be Right. Whether if Lefty and Righty are the same conscious mind or two different minds, I guess that's more of a philosophycal question.
deleted 18y ago
[deleted]
hugh 18y ago
Y'know, I'm a physicist, specializing in quantumy stuff, and I suspect that some form of many-worlds is probably true. But I don't really like the preachy "Many Worlds is just the way it is, and anyone who thinks otherwise is a fool" tone of this series of articles. They're actually pretty well written (I'd rate them above David Deutsch's Fabric of Reality, frinstance -- though I don't consider that very high praise), but I recommend taking them with a grain of salt. Example: We have embarrassed our Earth long enough by failing to see the obvious. So for the honor of my Earth, I write as if the existence of many-worlds were an established fact, because it is. The only question now is how long it will take for the people of this world to update. --- Sheesh, that kind of thing just doesn't belong in any scientific debate. The domain name bothers me as well. Is it supposed to imply that anybody who doesn't agree with everything written in overcomingbias has simply done a poor job in overcoming their biases?
- DaniFong 18y ago
  I don't really like them either. They're written well enough for one to basically follow along the sentences, and the tone is such that it seems they're really understanding something I'm not. But I looked pretty deeply into these questions. I read the original papers of Einstein Podolsky and Rosen, of Bohr, of Born. I read much of John Bell's original work, and I'm pretty sure that there are results being assumed here (and elsewhere) that haven't really been proven, or were even originally stated. For example, it's commonly asserted that Bell's theorem rules out any deterministic quantum mechanical description of reality with local hidden variables. But this was, to my knowledge, never shown explicitly by Bell -- he simply ruled out a particular class of local hidden variable theories. There exist theories, consistent with experiment, which are local and deterministic: for what it's worth, a toy example is just a classical computer simulating everything in our universe we've yet seen. We don't know where the Born probabilities come from, but we also don't really understand the implications of many body entanglement. We don't even have a consistent definition of entanglement for three or more particles. We don't know, we haven't been able to calculate, but I have reason to suspect, that measurement consistent with Born probabilities could be entirely explained by the deterministic axioms already part of Quantum Mechanics. We haven't really gone as far as we could go with them. And already people are treating Many-Worlds as axiomatic. I don't really buy it.
mattmaroon 18y ago
Wow do I wish I had the time to read all of that. As a former physics nerd, I enjoy well-written pieces that explain complex principles simply (though I'm not averse to some calculus). Maybe someday after I leave startupland.
nazgulnarsil 18y ago
the AI and Bayesian stuff is OB's strong suit. I don't think they've made their pet QM case very well.

16 points by hhm 18y ago

lg 18y ago

This bothers me because it pretends that it's railing against an unenlightened status quo, and it isn't. Philosophers of physics considered, and largely rejected, the many-worlds interpretation because, if quantum events result in every possible outcome occurring in some world, and our consciousness ends up in one of them by some chancy process, then there's no reason why we observe some events with higher probabilities than others. But we do, and many-worlds doesn't explain that. The author talks around this by saying that, yes, these probabilities are very mysterious, indeed. Well, there are other interpretations under which they're not. Such as a) the many flavors of GRW (a collapse theory), b) the bohmian interpretation (waves + particles), and c) the many-minds interpretation (anti-realist and therefore the most out-there of the three). Those are all pretty much consistent with QM, or there's a good reason to believe that they'll be beaten into a form that is so consistent (e.g. tumulka's relativized version of GRW-flash, but that's outside the scope of a HN comment).

rms 18y ago
http://en.wikipedia.org/wiki/Many-minds_interpretation http://en.wikipedia.org/wiki/Many-minds_interpretation
- lg 18y ago
  Well, I mentioned many-minds because a couple guys actually do take it seriously, even though most don't. But I think this entry is a little off when they say that many-minds "extends" many-worlds. On the many-minds theory, there's only one world, which is pretty different on the face of it. And since there are an infinite number of minds, if you get an 80-20 likelihood on values of some observable, then 80% of your minds will go to one and 20% to the other, which is very different from how many-worlds approaches splitting on outcomes.
hhm 18y ago
I don't know much about this, but wouldn't it be a lot more probable to be in a world of those many where the probabilities of events are distributed in a reasonable way, than to be in another world where the distribution of probabilities is out of the standard? (that is, there are many possible time lines, but the distribution of probabilities would indicate that there would be a lot more time lines for probable events, than for improbable events, so it's easier for us to be in a probable time line than in an improbable one). Or am I understanding something wrong? (Sorry for my English, I'm not a native English speaker)
- lg 18y ago
  The problem with many-worlds is that there aren't more timelines for probable events. If every outcome occurs in some world, then for some event with two possible outcomes, there ends up being two of you; say, Lefty and Righty, one in each world. So there's no sense in saying "I'll probably end up being Lefty, since his outcome was more reasonable," because you'll end up being both of them.
  - hhm 18y ago
    But I'm conscious of only one of only being Lefty, or not? If that's true, then for me at least, that behaves like a separate timeline of all others. That's what I meant in the post above: we are only conscious on what happens on a very reasonable timeline. Can this be like this?
    - lg 18y ago
      right, but Righty is conscious of being Righty, and if his outcome was highly unlikely, then he must be wondering why his world is so unreasonable. And since he's just as much you as Lefty is, post-event, it's not true that you're only conscious of what happens on a reasonable timeline.
      - hhm 18y ago
        But... Righty could ask why his world is unreasonable, but actually, being Righty is very improbable, so if we find the world to be actually very reasonable, it's because it's more probable to be Lefty than to be Right. Whether if Lefty and Righty are the same conscious mind or two different minds, I guess that's more of a philosophycal question.

deleted 18y ago

[deleted]

hugh 18y ago

Y'know, I'm a physicist, specializing in quantumy stuff, and I suspect that some form of many-worlds is probably true. But I don't really like the preachy "Many Worlds is just the way it is, and anyone who thinks otherwise is a fool" tone of this series of articles. They're actually pretty well written (I'd rate them above David Deutsch's Fabric of Reality, frinstance -- though I don't consider that very high praise), but I recommend taking them with a grain of salt. Example: We have embarrassed our Earth long enough by failing to see the obvious. So for the honor of my Earth, I write as if the existence of many-worlds were an established fact, because it is. The only question now is how long it will take for the people of this world to update. --- Sheesh, that kind of thing just doesn't belong in any scientific debate. The domain name bothers me as well. Is it supposed to imply that anybody who doesn't agree with everything written in overcomingbias has simply done a poor job in overcoming their biases?

DaniFong 18y ago
I don't really like them either. They're written well enough for one to basically follow along the sentences, and the tone is such that it seems they're really understanding something I'm not. But I looked pretty deeply into these questions. I read the original papers of Einstein Podolsky and Rosen, of Bohr, of Born. I read much of John Bell's original work, and I'm pretty sure that there are results being assumed here (and elsewhere) that haven't really been proven, or were even originally stated. For example, it's commonly asserted that Bell's theorem rules out any deterministic quantum mechanical description of reality with local hidden variables. But this was, to my knowledge, never shown explicitly by Bell -- he simply ruled out a particular class of local hidden variable theories. There exist theories, consistent with experiment, which are local and deterministic: for what it's worth, a toy example is just a classical computer simulating everything in our universe we've yet seen. We don't know where the Born probabilities come from, but we also don't really understand the implications of many body entanglement. We don't even have a consistent definition of entanglement for three or more particles. We don't know, we haven't been able to calculate, but I have reason to suspect, that measurement consistent with Born probabilities could be entirely explained by the deterministic axioms already part of Quantum Mechanics. We haven't really gone as far as we could go with them. And already people are treating Many-Worlds as axiomatic. I don't really buy it.

mattmaroon 18y ago

Wow do I wish I had the time to read all of that. As a former physics nerd, I enjoy well-written pieces that explain complex principles simply (though I'm not averse to some calculus). Maybe someday after I leave startupland.

nazgulnarsil 18y ago

the AI and Bayesian stuff is OB's strong suit. I don't think they've made their pet QM case very well.