tag:blogger.com,1999:blog-15005476.post1958374126144354983..comments2023-03-14T10:37:33.117-04:00Comments on Rationally Speaking: Eliezer Yudkowsky on Bayes and science: what?Unknownnoreply@blogger.comBlogger43125tag:blogger.com,1999:blog-15005476.post-61916766650393385652013-10-06T00:25:04.879-04:002013-10-06T00:25:04.879-04:00I realize this post is very late and will probably...I realize this post is very late and will probably go unread, but I'd like to make a few points. Massimo, I think your negative critiques of Yudkowsky's posts are simultaneously unfair and understandable. They're unfair because those posts are, essentially, conclusions to a lengthy QM sequence Yudkowsky wrote. Critiquing them alone would be like only critiquing the conclusion of a book. However, I think your critique is understandable in that it's often unclear when you first stumble onto LW posts where a sequence starts!<br /><br />I think you're fundamentally wrong on your points addressing B and C (in your original post): <br /><br />a) There’s no doubt that MWI is simpler than CI. I don’t think any physicists argue this. <br /><br />b) The best arguments are as much AGAINST CI as opposed to FOR MWI. CI flies in the face of macro physics being non-local, non-real, and indeterministic; it flies in the face of history, as it would be the first time a theory contradicted an old theory without falsifying the old theory OR subsuming the old theory into a more complete formulation (ala General Relativity with Newton); Worst of all, it does those things without an empirical or mathematical reason for doing so. <br /><br />c) One could argue MWI IS supported on empirical grounds. What we'd expect to see if MWI was true is that everything would be in a state of superposition like a particle. So far, we've managed to place 2424 particles in such a state without finding the "split" predicted by CI. MWI can really only be falsified, by, eg, showing how, at some points, large objects STOP being in superposition. If you want a good, short, simple argument on these points from a physicist, see here: http://www.askamathematician.com/2010/10/q-copenhagen-or-many-worlds/<br /><br />d) As for what this has to do with Bayes, it affects both priors and posteriors. It affects priors because MWI is more likely to be true a priori by being simpler. You've mentioned several times in these replies that there were times when simpler theories turned out false, which is no different than saying some smokers live long lives and some non-smokers die of lung cancer. The issue is one of probability, and simpler explanations are, a priori, more LIKELY to be true always. It affects posteriors because, thus far, every empirical test supports it and, to some degree, has made CI less likely. It’s made CI less likely because if CI is true there should be SOME split SOMEWHERE between the two worlds. There should come a point when a group of particles isn’t in superposition. <br /><br />So, with all that in mind, I think it's a little clearer why Yudkowsky is advocating Bayes "over" Science. I put "over" in quotes because I think many of the points that Yudkowsky makes are more against scientists than science, saying that they are waiting for that one great "eclipse experiment" that will "prove" one interpretation right and win everyone involved Nobel Prizes. In the absence of that, scientists are being far too flippant about just "going" with CI and not realizing how MWI is supported both a priori and by the empirical data. The reason they do is that they aren't making use of Bayes. Yudkowsky certainly isn't saying that Bayes (and MWI) contradicts the existing science. I think his "Bayes over Science" should really be "Bayes IN science,” and in arguing throughout his QM sequence why MWI is by far the best interpretation he’s showing how wrong even science can go when it doesn’t incorporate Bayes. solragehttps://www.blogger.com/profile/05672698903519045834noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-60970905705226279172012-06-14T06:04:04.060-04:002012-06-14T06:04:04.060-04:00Regarding simplicity, the argument that simpler th...Regarding simplicity, the argument that simpler theories are more probable (a priori) can be put on a firm mathematical footing. The trick is to have the appropriate definition of simplicity. The appropriate notion (first articulated by Ray Solomonoff) is Kolmogorov complexity. Roughly speaking, the Kolmogorov complexity of a theory is the length of the shortest computer program which simulates that theory. The simplicity argument for the many worlds interpretation says that the worlds drop out of the math, and thus a computer program which simulates MWI is shorter than a computer program which has to worry about "collapse".Patrick Robothamhttps://www.blogger.com/profile/13757553286588373351noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-82646832637260819262010-10-05T23:03:04.100-04:002010-10-05T23:03:04.100-04:00Jesus Pineda:
No, the QM (quantum mechanics) measu...Jesus Pineda:<br />No, the QM (quantum mechanics) measurement problem is a real problem for all variants of the "Copenhagen interpretation" of QM. Read again the last paragraph of my comment September 23, 2010 8:07 PM! The Copenhagen QM is not even well defined, so even if not for anything else it cannot for this reason be considered an acceptable fundamental theory of physics (and there is also a lot else).<br /><br />As a pragmatic approach for practical use of QM it does work of course (we do know practically when we have performed a measurement even if it not formally defined in the theory). So the "shut up and calculate interpretation" is fully acceptable for that purpose (even if it should really be called a pragmatic tactic, not an interpretation). The measurement problem remains an important outstanding problem in physics, but not everyone has to be interested in everything so if you want to leave the fundamental problems of the theory to others that is a perfectly acceptable position. But it does not make the fundamental problem dissapear.<br /><br />And, no, the Copenhagen QM is not in a true sense an extension of classical physics. It simply postulates two completely different realms of the world: the quantum realm and the classical realm (and this evem without in the theory giving a definition of where the boarder is, another way of stating why the theory is not even well defined). So it does actually not give classical mechanics as a special case. (To be completely fair, it does give a very small part of classical mechanics as a special case. Ehrenfest's theorem (or its many equvalent formulations) and all that. But this is only a tiny part of our empirically observed classical experience. In particular, the infamous cat is not part of the classical world that Copenhagen QM gives in its very limited classical limit!)<br /><br />We do not want to explain the quantum world in classical terms. We want to have a well dedfined (mathematically formulated) theory that is consistent with all our empirical data. Including as a special case all our "classical experiences". And Copenhagen QM simply does not deliver on this. Therfore something has to be done, and my personal judgement is that the reasonable position at the current level of knowledge in science is the "more research is needed interpretation" of QM.tonyfhttps://www.blogger.com/profile/16381314738702489946noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-31591066615250543362010-10-05T00:50:35.429-04:002010-10-05T00:50:35.429-04:00I'm arriving quite late to the party, however ...I'm arriving quite late to the party, however I'd like to contribute my two cents.<br /><br />I'm a theoretical high-energy physicist and the subject of the "interpretation" of quantum mechanics has always struck me as a bit of a hodgepodge of bad epistemology. <br /><br />Allow me to explain: Yes, as Feynman said, you can't understand quantum mechanics, if by "understand" we mean forming quantum mechanical concepts and interactions from the concepts and connections of our experience. Our brains did not evolve in conditions where our capacity to observe quantum phenomena would give us an advantage, so it is easy to understand our imposibility to grasp quantum mechanics like we can grasp classical mechanics.<br /><br />Now, in my eyes the "interpretation problem" seems silly: we physicists tell our students and the public that quantum mechanics is a "more fundamental" theory than classical mechanics, which is to say, it explains a larger set of natural phenomena and it includes classical mechanics as a special case. <br /><br />In spite of what I have just said we then go into the trouble of "interpreting" QM, which seems to be little more than trying to explain the behavior of a quantum system in terms of classical concepts that our classical minds can grasp. All this discussion of multiple worlds, pilot waves, wave function collapse and what not are all classical ideas, meaning that they are ideas we have gathered from our day to day classical experience.<br /><br />So we seem to want to put the "more fundamental" theory in terms of the "less fundamental" one... to some extent it is like trying to undestand biology in terms of sociology.Unknownhttps://www.blogger.com/profile/13341164635515296599noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-52375946861568876412010-09-30T09:08:27.177-04:002010-09-30T09:08:27.177-04:00@Tonyf
"Well, it would have been fine if it ...@Tonyf<br /><br />"<i>Well, it would have been fine if it had been actually the case.</i>"<br /><br />I agree with you, in any cases, the collapse remains at least as an heuristic method for infering predictions, and it's not certain we can deduce probabilities of observations from MWI. <br /><br />The question is wether we need to assume that the collapse is a physical phenomenon or not. This assumption is not required for the physicist's practice, as a "collapse" cannot be practically observed. It's only a matter of interpretation. That's what I meant in the sentence you've quoted.<br /><br />"<i>But you (and many other here) seems uncritically accept that MWI is just an interpretation, not a theory</i>"<br /><br />I think it is, because other "worlds" are not observable. Neither is the wave function collapse, that's why its nature needs to be interpreted.<br /><br />A theory is only a mathematical model + a set of predictions. MWI does not change anything of the model of quantum physics nor its predictions. The question is why do we get such results and how do we interpret the wave function and the "collapse" ?<br /><br />"<i>It is not just different ontologies put on top of the two different [theories or interpretations], it is two very different mathematical formulations</i>"<br /><br />The mathematic formulations are the same, i.e. QM formalism. Decoherence has been empirically observed and is a consequence of QM formalism. There is no difference.<br /><br />"<i>the false dichotomy "MWI versus Copenhagen".</i>"<br /><br />I agree with you. Other interpretations exist (objective collapse, transactional interpretation, ...)<br /><br />I suggest everyone have a look at Carlo Rovelli's relational interpretation : http://en.wikipedia.org/wiki/Relational_quantum_mechanics<br /><br />I find it very promising. The postulate that an absolute objective reality exists is not required, which I find very interesting (and coherent with special relativity and locality of time).Quentin Ruyanthttps://www.blogger.com/profile/18395553776256376317noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-76258437175134038092010-09-29T20:21:53.281-04:002010-09-29T20:21:53.281-04:00Massimo: "One problem, as I pointed out in my...Massimo: "One problem, as I pointed out in my post, is that QM seems to be the only theory for which we need to somehow come up with an interpretation - because what it says is so alien to our everyday experience. And when you interpret you are not doing science anymore, at least not in any straightforwardly empirically testable way."<br />Interestingly enough this may actually be more the case for the special theory of relativity than for quantum mechanics. Einstein's theory of special relativity gives the same empirical predictions as Lorentz' "ether" theory. But Einstein's theory was immediately accepted due to it larger simplicity. This is also a counterexample to Yudkowsky's claim that if two theories/interpretations have the same empirical contents science chooses the one presented first, since Lorentz' theory was the first. (OK, maybe Yudkowsky could say that in this case practical science did not live up to "ideal science".) Later of course we got also another reason to prefer special relativity; it generalises quite naturally to general relativity which did new predictions that were confirmed empirically. But special relativity was accepted by most leading physicists already before general relativity.<br /><br />"alien to our everyday experience": this should not be a problem as long as an unambiguous mathematical formulation can be done?<br /><br />Massimo: "Yudkowsky has not established the strong thesis that had the many-worlds theory be presented first it would have been accepted."<br />We agree on this one.tonyfhttps://www.blogger.com/profile/16381314738702489946noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-23898729141338256052010-09-29T20:20:06.763-04:002010-09-29T20:20:06.763-04:00Q: "In my opinion, the Bayesianism argument s...Q: "In my opinion, the Bayesianism argument should not apply to an interpretation, but only to a theory."<br /><br />Maybe true and I would like to hear more coments on this from those who know more bayesianism. But you (and many other here) seems uncritically accept that MWI is just an interpretation, not a theory. I doubt that. The "Copenhagen" has rules how we get definite otcomes of measurements (as well as rule for what the probabilities for different possible outcomes should be). Not clearly enough defined rules and "weird" ones too, but it has them. The MWI is a [theory or interpretation] which is defined by the same postulates, save for that you have eliminated the one(s) (the collapse postulate) that gives you the definite measurement results. But from eperience we know that we at least perceive what "Copenhagen"says -- a dead cat or a live cat, not a linear combination of dead and live cat. So clearly "raw MWI" is falsified by empirical data. If MWI should survive we have to do something more to explain that we perceive measurements outcomes as we do. And nowdays we have at least some reasonable hope of being able to do this by decoherence (some think that is already fully accomplished which I doubt, but that's the subject of my previous comment, here it is sufficient to say that at least we have some hope of being able to accomplish it), the quantum correlations are killed or hidden by interaction by the environment. This works only in a universe with a lot of negentropy. We do live in such a universe since the big bang happened to create (for reasons we at the present state of science can only speculate in why) our universe in a state of low entropy. That, I would say, makes it reasonably to regard MWI as a different theory rather than just a different interpretation of the same theory. In "Copenhagen" measurement outcomes really are determinate (in the sense cat either dead or alive) while in the MWI they only are perceived to be so conditionally on the conditions of the universe.<br /><br />Now of course those wanting to call it "only interpretation" could say that both "Copenhagen" and "MWI" always give the same perceived experience, because for a universe to have perceiving beings it has to have negentropy. So in that sense they give always the same empirical predictions and should be called just different nterpretation of the same theory. But that I think is to stretch it too much. It is not just different ontologies put on top of the two different [theories or interpretations], it is two very different mathematical formulations -- not at all equivalent in a technical mathematical sense.tonyfhttps://www.blogger.com/profile/16381314738702489946noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-55921923845460263092010-09-29T13:16:43.216-04:002010-09-29T13:16:43.216-04:00Q: "Quantum physics does not need a collapse ...Q: "Quantum physics does not need a collapse to be used for prediction, etc., and that's fine."<br /><br />Well, it would have been fine if it had been actually the case.<br /><br />Q, and many others above, the claim that MWI(="von Neumann QM minus projection postulate") is able to predict observed empirical data is a controversial one. Maybe it is able to do this, maybe not, but I repeat my request towards the end of my post September 23, 2010 8:08 PM. I do not claim to know the most recent literature on this but my impression is that it has not been demonstrated that MWI actually does give the predictions. As to whether MWI actually does that or not I am completely (temporarily) agnostic. But much of the other discussions seem to me a bit premature before that technical question has been resolved.<br /><br />As for the hypothetical question if MWI is to be preferred if it was actually delivering what its proponents claim/hope: Yes definitely over "Copenhagen". But here comes another limitation of Yudkowsky's presentation, the false dichotomy "MWI versus Copenhagen". Very satisfactory e.g. would (I think) be a local hidden-variable theory which, maybe, could be constructed by means of (microscopic only) causation both forwards and backwards in time. To my knowledge no one has succeeded actually doing that so far. But so I have not so far seen an actually technically working formulation of MWI. Think whatever you want about this particular proposal, it is just an example of my main point that the QM problem is not a dichotomy.tonyfhttps://www.blogger.com/profile/16381314738702489946noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-55359393247740027502010-09-28T11:49:37.192-04:002010-09-28T11:49:37.192-04:00In my opinion, the Bayesianism argument should not...In my opinion, the Bayesianism argument should not apply to an interpretation, but only to a theory.<br /><br />Quantum physics does not need a collapse to be used for prediction, etc., and that's fine. Bayesianism could apply if ever we had an other concurrent theory, I don't think this is the case.<br /><br />The problem of an interpretation is very different. The question is how do we interpret the objects of the theory.<br />MWI claims that the wave function is real. Copenhague interpretation claims that it's a catalogue of predictions (and the "collapse" is how we infer predictions from the catalogue).<br /><br />I don't think that Bayes is of any help for interpreting the objects of a theory. <br /><br />Copenhague interpretation sounds more reasonable to me, although it's not fully satisfying. MWI looks very much like a confusion between the scientific model and reality itself (a recurent problem), without any philosophical hindsight.Quentin Ruyanthttps://www.blogger.com/profile/18395553776256376317noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-76813475171467744022010-09-27T21:26:29.260-04:002010-09-27T21:26:29.260-04:00Dan,
Yeah, it seems like Yudkowski is taking Bayes...Dan,<br />Yeah, it seems like Yudkowski is taking Bayesianism to include arguments about prior probabilities. The thing is, those are the weakest kind of Bayesian arguments. Maybe if MWI were vastly simpler than Copenhagen, I would be convinced. But MWI is only a little bit simpler, so I'm only a little bit convinced.<br /><br />In any case, I think science really does consider prior probabilities. Steven Novella <a href="http://skepticblog.org/2008/12/15/skeptical-battlegrounds-part-iii-alternative-medicine/" rel="nofollow">once explained</a> this as the difference between science-based medicine and "evidence-based medicine" (a term unfortunately adopted by alternative medicine). The trouble with "evidence-based medicine" is that it levels the playing field for wildly implausible claims such as homeopathy.millerhttps://www.blogger.com/profile/05990852054891771988noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-36922071204036268452010-09-27T13:23:55.507-04:002010-09-27T13:23:55.507-04:00miller,
Unfortunately, I probably know less about...miller,<br /><br />Unfortunately, I probably know less about Bayesian probability than I do about quantum mechanics, so I don't think I can answer your questions satisfactorily. Most of what I've read by him was the quantum mechanics stuff, because I'd heard it was a good explanation of the many worlds interpretation.<br /><br />I gather that what I mentioned earlier, that Copenhagen is the same as many worlds, except that we make some additional, unsupported assumptions, constitutes arguing about prior probabilities?<br /><br />In that case, it may be that Yudkowsky would suggest that there *is no* body of evidence that can distinguish the two interpretations. But, you can argue about the priors, and perhaps he considers doing so to fall within Bayesianism.<br /><br />That might explain the content of the article that sparked this discussion, too. That is, if there were actual evidence upon which to base an argument for one interpretation over the other, scientists would use it. But, science (allegedly) doesn't allow arguing about prior probabilities to allow one theory to supplant another when they are otherwise indistinguishable based on evidence (instead, preference is given to the theory that came first). So, even though Bayesian probability may model scientific reasoning, it may be that someone acting as a Bayesian accepts arguments that someone acting as a scientist wouldn't.<br /><br />But, this is merely a guess about something well out of my area of expertise, so take it with a grain of salt.Dan Doelhttps://www.blogger.com/profile/16761291400347369301noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-4720424890649514552010-09-27T10:47:45.420-04:002010-09-27T10:47:45.420-04:00Regarding your remarks, you are correct that Yudko...Regarding your remarks, you are correct that Yudkowskyis arguing that "The order in which scientists arrive at their theories matters" but he's also arguing that it shouldn't. Essentially his argument boils down to:<br /><br />1) Given two theories, scientists are more likely to accept the one that came first even if all data supports them equally.<br />2) (1) is bad from a Bayesian perspective.<br />3) His example of this is the interpretation of quantum mechanics where he argues that MWI is essentially simpler than most other interpretations of QM and thus if one is accepting an interpretation, MWI should be the one accepted since it is simpler.<br /><br />1 and 2 seem reasonable to me. I don't have the expertise to evaluate 3.Joshuahttps://www.blogger.com/profile/00637936588223855248noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-39399267939480606182010-09-27T02:40:03.741-04:002010-09-27T02:40:03.741-04:00It seems to me that many people don't understa...It seems to me that many people don't understand how observation can collapse the wave function. The fact of the matter is that waves interfere with waves and, thus, we get an interference pattern whenever there is "observation." Wave interference causes the initial wave to break up into a trillion little wavelets, which then interact to form the complex system we describe as a particle. It's all waves -- and communicating waves, which communicate using waves. Thus, it is all information -- defined as "that which is without form, which gives form."Troy Camplinhttps://www.blogger.com/profile/16515578686042143845noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-35565765285763581542010-09-25T21:04:11.452-04:002010-09-25T21:04:11.452-04:00Dan,
If Yudkowski is not making the argument that...Dan,<br /><br />If Yudkowski is not making the argument that I thought he was, then good for him. However, I find it rather difficult to imagine what other Bayesian argument you could possibly make for the Many Worlds Interpretation. A Bayesian argument takes some prior probabilities, and finds posterior probabilities given a collection of evidence.<br /><br />What is the collection of evidence here? All I see is arguing about prior probabilities. That's great and all (I'm a MWI partisan myself), but how is that a Bayesian argument?millerhttps://www.blogger.com/profile/05990852054891771988noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-76226261126296761092010-09-25T13:25:44.077-04:002010-09-25T13:25:44.077-04:00Justin,
thanks! Great to hear from a real QM phys...Justin,<br /><br />thanks! Great to hear from a real QM physicist! I don't know of any sociological data along the lines you suggest, but I'd certainly be interested.<br /><br />> Most interpretations out there smack of our classical brains trying desperately to understand quantum reality. <<br /><br />Precisely.Anonymoushttps://www.blogger.com/profile/09099460671669064269noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-2503961039215212792010-09-25T11:26:10.738-04:002010-09-25T11:26:10.738-04:00Massimo,
Thank you for that post. As a quantum ph...Massimo,<br /><br />Thank you for that post. As a quantum physicist, I was quite bothered by Yudkowsky’s post, but we’re untrained in Bayes’ theorem so I had no ground to argue on.<br /><br />When it comes to the interpretations themselves, it seems to me that most of us are in the “shut up and calculate” camp (I'm not, but I'm not really in any camp). I don’t think a majority of physicists actively subscribe to many-worlds, but I would actually be curious if there was any sociology of science data on what interpretation physicists most subscribe to. Do you know of any?<br /><br />For myself, all interpretations seem lacking to me. I’m unsatisfied with many-worlds and Copenhagen. Most interpretations out there smack of our classical brains trying desperately to understand quantum reality. <br /><br />And thanks for your plug about the wave-particle duality being a gross analogy. We only use one mathematical object for light (photons): the quantum field (QED for light). It just so happens that it has properties of both particles and waves.<br /><br />-JustinJustinhttps://www.blogger.com/profile/10243948971189727525noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-28527862423194246672010-09-24T19:49:19.363-04:002010-09-24T19:49:19.363-04:00Massimo, I have a somewhat tangential but I think ...Massimo, I have a somewhat tangential but I think important meta-criticism.<br /><br />Quote: "It is no secret that my already normally skeptical baloney detector now jumps to deep orange alert any time I hear the word “singularity.”... My later encounters with that particular group of techno-optimists and futurists have not improved my opinion of the whole shebang a bit."<br /><br />We don't always have the time or resources to investigate ideas fully, so heuristics are an extremely useful tool for time-constrained rationality. However, every time we use a heuristic like "judge an idea by the personality & conduct of its proponents," or "judge an idea based on surface analogies to religions & cults" as you've done here & in other posts, we should feel a strong twinge of guilt for having failed to really give the idea a fair shake.<br /><br />One of the very few recurring mistakes that I feel you & Michael often make (probably unconsciously), is to look at some behaviour (by conservatives or singularitarians, for example) that you disapprove of, & then tacitly imply that you've made some sort of argument against the idea.<br /><br />But alas, one cannot learn about the feasibility of, say, recursively self-improving AI, by observing the psychology of transhumanists. As Yudkowsky loves to say, reversed stupidity is not intelligence.<br /><br />Now I am not saying you *explicitly* believe that social judgments are crucial to evaluating ideas. But the problem is, it is an empirical *fact* that humans tend to evaluate ideas based on factors such as whether they would like to affiliate with the proponents.<br /><br />This bias comes in addition to a <a href="http://en.wikipedia.org/wiki/List_of_cognitive_biases" rel="nofollow">majestic suite</a> of others, none of which are easily overridden by conscious effort. This is why being a rationalist is a lot like being a recovering alcoholic.<br /><br />Given these epistemic dangers, even *mentioning* personality in passing, in a discussion we wish to be rational, is like bringing vodka to an AA meeting. Yeah yeah, I know, we're not robots, but it would be nice to particularly avoid such comments when the topic under consideration is still legitimately controversial.<br /><br />But maybe I'm too hard-line about biases?ianpollockhttps://www.blogger.com/profile/15579140807988796286noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-37612741902101717872010-09-24T16:41:03.367-04:002010-09-24T16:41:03.367-04:00Dan,
I'm all in favor of more people understa...Dan,<br /><br />I'm all in favor of more people understanding quantum mechanics. But as you point out, there are two levels of "understanding" here. One is the math. Obviously, many people understand that, though I suspect you overestimate most people's math skills in that respect.<br /><br />The second issue is whether we understand the reality behind the metaphors. Take the dual nature of light: when we say that it behaves both like a particle and like a wave, that is a gross analogy, because clearly light isn't either a particle or a wave as commonly understood, but something else that we can approximate using those two metaphors combined (even though they are usually antithetical!).<br /><br />As for our friend Yudkowsky, my criticism of his three posts was that they don't make an argument, and that if he thinks Bayesianism is opposed to good scientific practice then he is wrong. None of that has much to do with how many people understand QM.<br /><br />Last point: we better not be too confident that QM tells us how the world "really is," because plenty of previous scientific theories have claimed that, and it turns out the world was really different. Indeed, if string theory is correct, then the world isn't quite like what QM tells us it is.Anonymoushttps://www.blogger.com/profile/09099460671669064269noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-39440942906031981072010-09-24T15:20:41.042-04:002010-09-24T15:20:41.042-04:00"just to make clear, the bit you quote was no..."just to make clear, the bit you quote was not from my article, but from a previous commenter."<br /><br />Yes, I should have made that clearer.<br /><br />"But I have to disagree that Feynman's chestnut somehow doesn't apply. QM is the most complex scientific theory we have, and to really understand it one has to understand the math, which most of us (including me) don't."<br /><br />Lots of people do understand the math though. Even back when Feynman said that, there were people who were well acquainted with the it. And certainly, we expect physics students to be capable. It's not really even especially difficult math. The majority of engineers in the US probably learned enough to understand quantum mechanics.<br /><br />Yet it seems to be standard practice to tell people, "this stuff is weird, and you probably won't understand it, and Feynman said no one does." I don't think that's because of the math, but, as you say, "because what it says is so alien to our everyday experience."<br /><br />It is alien. I'm sure Yudkowsky would agree. However, the tack he takes is: quantum mechanics is how the universe actually works. Your everyday experience is what is weird, and wrong (sort of). So when quantum mechanics says something alien, you shouldn't just say, "that's weird, and un-understandable." You should instead try to think of the quantum mechanical happenings as natural, because, well, they are. And perhaps, "I won't understand QM because it's weird and alien," won't become a self-fulfilling prophecy.<br /><br />He actually doesn't even get into the details of the math much. You can get into some of the unexpected results without it. Like, shooting single photons through a network of mirrors can lead to unintuitive results, but why what happens happens can be explained with simplified math (i.e. solving differential equations isn't the important part).<br /><br />I think he's relatively successful, but I'm not a physicist, so maybe I've been duped.<br /><br />I actually have experience with something like this elsewhere. I know a certain programming language (Haskell) where some common techniques are introduced to the language via a mathematical construct (monads). For a long time, when explaining this to new folk, people would preface their explanation by how scary and difficult this all was, and how it was related to abstract mathematics (category theory). But, in reality, it isn't all that difficult to understand what's going on on a practical level, and isn't much more difficult to use than more typical languages. So one wonders how much trouble people have had merely because they've been told they *should* have some; that there *is* something especially difficult here to understand.<br /><br />QM probably isn't in exactly the same boat, but prefacing explanations by, "you aren't really expected to understand this, because it's weird, and no one does," probably isn't helpful.Dan Doelhttps://www.blogger.com/profile/16761291400347369301noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-31067645466814618382010-09-24T13:25:10.955-04:002010-09-24T13:25:10.955-04:00The many-world interpretation is indeed simplier t...The many-world interpretation is indeed simplier than any other interpretation : it does not require any collapse.<br /><br />But it is also incomplete. <br /><br />It's merely a mathematical description of everything that may happen / have happened / will happen, the infinite set of all possibilities.<br /><br />If you think of a scientific theory as a predictive tool, that is fine : you don't need a collapse, and MWI is the best heuristic choice. But if you think of a scientific theory is a kind of ontological candidate and begin to claim that all the possibilities described by the evolution of the wave function actually exist, then you step into metaphysics and problems will arise...<br /><br />You can claim that other branches of reality exist, although you have no way to perceive them. That's not a problem.<br />But you can also claim that your past exist : it is indeed described by the theory as a wave function, just as your present is. You don't perceive your past anymore, but that's not a problem, is it ? What is so special with your present to be more "real" than your past?<br /><br />And every possible future exists too. And every alternate futures of all your past instants... Everything exists!<br /><br />To this point, one could say: ok, everything exists... But what do we mean exactly by "exists"?<br /><br />Quantum physics questions the fundaments of science: epistemology itself. What do we mean by "exist" and how can we know something exist? Is there an objective reality ? What exactly is the scientific model, is it a description of reality like a map is the description of a territory, or is it something else?<br /><br />Please tell me if you have an answer...Quentin Ruyanthttps://www.blogger.com/profile/18395553776256376317noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-67483330750374226072010-09-24T13:16:09.404-04:002010-09-24T13:16:09.404-04:00Dan,
just to make clear, the bit you quote was no...Dan,<br /><br />just to make clear, the bit you quote was not from my article, but from a previous commenter.<br /><br />I don't know whether Yudkoswky is right abut the difference between the two theories. Seems to me that if it were that obvious a few smart physicists would have figured it out by now.<br /><br />But I have to disagree that Feynman's chestnut somehow doesn't apply. QM is the most complex scientific theory we have, and to really understand it one has to understand the math, which most of us (including me) don't.<br /><br />One problem, as I pointed out in my post, is that QM seems to be the only theory for which we need to somehow come up with an interpretation - because what it says is so alien to our everyday experience. And when you interpret you are not doing science anymore, at least not in any straightforwardly empirically testable way.Anonymoushttps://www.blogger.com/profile/09099460671669064269noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-82438576987090318412010-09-24T12:47:55.827-04:002010-09-24T12:47:55.827-04:00I must agree, it's hard to know what to make o...I must agree, it's hard to know what to make of Yudkoswky. On the one hand, I've read some of his quantum mechanics stuff, and random smattering of other posts, and a lot of what he says seems well-thought out, and makes sense. But then, at random, he'll say something that reminds me that I'm reading someone who thinks that one of the biggest threats to humanity is, paraphrasing, super-smart, evil, artificial intelligences.<br /><br />But:<br /><br />"My guess, without reading Yudkowski, is that he thinks Many Worlds is more likely because the more worlds there are, the more likely life is to arise. I think this reasoning is flawed for complicated reasons. In short, this argument favors Many Worlds by a factor of order N, where N is the number of worlds."<br /><br />Perhaps you should go read him. I've read a fair amount of his stuff about quantum mechanics, and I can't imagine him making that argument. It's not even clear that that argument makes sense given his explanation of many worlds, because it isn't a multiverse theory where there are N worlds, but rather that the apparent collapse of wave functions upon measurement is due to the wave function of a 'world' splitting into multiple, non-interacting parts.<br /><br />Rather, I think he argues that the Copenhagen interpretation is essentially many worlds, plus the postulate that when the wave function splits as it does in many worlds, there is a single designated "real" world part of the wave function, and all of the other parts disappear. But, this is an extra, (so far) unobservable assumption on our part, and makes the interpretation less simple.<br /><br />Regardless of whether he's right about various aspects of this stuff, I do think there's one useful idea in his series of articles: let's stop telling everyone that quantum mechanics is mysterious and hard to understand right off the bat. Even Massimo immediately quotes Feynman's chestnut about how no one really understands quantum mechanics. But that was decades ago, and QM is no longer as new as it once was. What if the reason it has a reputation for being so weird and difficult to understand is merely because people keep repeating the meme and quoting old authorities?Dan Doelhttps://www.blogger.com/profile/16761291400347369301noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-65010985661153290032010-09-24T12:35:17.011-04:002010-09-24T12:35:17.011-04:00Furcas,
sorry, I aint' gonna read 30 posts by...Furcas,<br /><br />sorry, I aint' gonna read 30 posts by Mr. Yudkowsky. Seems to me that at least the outline of an argument could be made in a single post. At the very least Yudkowsky makes no argument at all in the three posts I have read, even though the title of one of those posts implies that one is about to read an argument.<br /><br />And no, I don't think ianpollack has it right, but of course intelligent disagreement is the point of this blog.Anonymoushttps://www.blogger.com/profile/09099460671669064269noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-74633521868875266902010-09-24T09:59:31.882-04:002010-09-24T09:59:31.882-04:00Alex,
I can't read everything Yudkowsky, or a...Alex,<br /><br />I can't read everything Yudkowsky, or anybody else, for that matter, writes. I was directed to those posts by one of Julia's picks, so my analysis is limited to those posts.<br /><br />I stand by what I wrote about quantum mechanics. I am no expert, but that's what I got from general readings about it.<br /><br />Thesis (b) needs to be argued in detail, and at any rate - as I have repeated argued above - simplicity per se is not enough to decide between scientific theories.Anonymoushttps://www.blogger.com/profile/09099460671669064269noreply@blogger.comtag:blogger.com,1999:blog-15005476.post-55268404175701310552010-09-24T09:55:19.712-04:002010-09-24T09:55:19.712-04:00These posts are random samples from long sequences...These posts are random samples from long sequences on their respective topics. I don't think you have understood much of what Eliezer was trying to say (and I'm not passing judgement on whether that's your fault or Eliezer's).<br /><br />- The copenhagen interpretation does _not_ say that a particle collapses to a specific point when measured. The so-called "collapse postulate" refers to disjoint regions of quantum configuration space disappearing.<br />- The wavefunction does _not_ describe anything probabilistic. It says that a particle is "smeared" through space and time, no probabilities about it!<br />- The topics of the fictional dialogues are covered formally and directly in other posts.<br />- Thesis (b) has been argued in detail, and it's pretty clearly true once you do the analysis.AlexFhttps://www.blogger.com/profile/11131160667450362658noreply@blogger.com