One of the two major fields in modern physics. See http://en.wikipedia.org/wiki/quantum_physics ---- Quantum Mysteries (Goof Guide) http://epunix.biols.susx.ac.uk/Home/John_Gribbin/Quantum.html ---- The next two sections below used to be at the very bottom. They're at the top so that the reader can know what they're getting into. ---- Who is talking to whom here!? I am trying to learn about QM, but this page *absolutely* doesn't help - what a mess * ''Sorry, but this can be part of the wiki experience. You can always try to fix it. Please keep in mind that since anyone can and does edit these pages, all the information on this wiki is subjective.'' ---- As someone with a Ph.D. in theoretical physics (but who has avoided the subject for the last decade), I agree that this page is definitely a mess. Here are some high-level comments about quantum mechanics. Quantum mechanics consists of some mathematical equations that do an excellent job of explaining a wide range of experimental observations. However, it has a few weaknesses. At a practical level, the equations are often too difficult to solve. For example, nobody can derive organic chemistry from first principles starting with the laws of quantum mechanics. Also, various theoretical difficulties remain, such as unifying quantum mechanics and general relativity in a single unified theory (GrandUnifiedTheory). Finally, there's the philosophical question of what the mathematics of quantum mechanics actually means in terms of understanding the physical world. The CopenhagenInterpretation is one approach to that question, and the many-worlds interpretation is another. Popular science books emphasize the philosophical angle, while most physicists instead focusing on solving the equations. Much of this page is a diatribe about the various interpretations. -- Anonymous ---- Be very careful about the CopenhagenInterpretation of quantum mechanics because it is deprecated, fundamentally anti-scientific and only gained popularity because of an error John von Neumann made in his "proof" that the universe is "non-deterministic". In actuality, the term "non-determinism" doesn't even mean anything coherent. Albert Einstein was right all along. When Stephen W. Hawking says that the universe is non-singular, he isn't claiming it's non-deterministic and he's basing his judgement on an interpretation of black hole evaporation (the belief that information is destroyed during the process) over which there is a lot of controversy. Many cosmologists actively resist the notion that information can be destroyed and theoreticians working with the theory formerly known as superstrings (the ''only'' known theory that can make sense of black holes) have neatly explained black hole evaporation without postulating the destruction of any information (destruction of information violates the second law of thermodynamics). The Heisenberg Uncertainty Principle is also deprecated. Modern physicists speak of entanglement and not "uncertainty"; the former is an information-theoretic concept while the latter is a purely classical concept. In fact, the HUP was originally introduced to explain quantum mechanical phenomena in a classical manner; it was a sop to people uncomfortable with a large paradigm shift. Unfortunately, there are thousands of books in every library claiming that the CopenhagenInterpretation is a coherent scientific theory and it will take decades for them to rot away. The nonsense about how light is "both a wave and a particle" (it is neither, it is a non-linear wave called a 'soliton') is an example of how badly physicists have screwed up the education of physics, both to the general population and to themselves. Believing self-contradictory nonsense like "both a wave and a particle" is a sure sign that reason and logic have been derailed. My high school physics textbook (bought circa 2002) states that (and I paraphrase) "But there is no contradiction. Light is neither a wave nor a particle, it has properties in common with both." This is from a book that has trigonometry as its math prerequisite. My standard calculus-based university textbook also has similar language. So I would have to argue that I was not miseducated in this regard, and I strongly suspect that others weren't either. These books were from major publishers, and quantum physics is, as you'd guess, far from discussed in detail and certainly no math is involved in what little there is. As to educating the general public,that I'd probably agree with you on. -JasonEspinosa In the 1920s, non-determinism was the only way to go. It took three decades for John Stuart Bell to prove a deterministic theory of quantum mechanics was possible. And it took another three decades for Hugh Everett III to construct such a theory. At this rate, I predict we will have conclusive evidence for Many-Worlds by 2010. But since everyone still "knows" that the universe is non-deterministic, I also predict that physicists at large will only believe this evidence by 2040 and the general population by 2070. ''This is a nice bit of polemicism, but the timeline is unfortunately wrong. Everett's paper "Relative State Formulation of Quantum Mechanics" was published in 1957. Bell did not publish his theorem until 1964.'' Physics is actually very simple. So simple that you can teach it to 12 year olds. And if you did it with CartoonGuideToPhysics, it would be a breeze. It's only physicists that insist physics can only be "truly" understood by physicists. And since they're the ones saying self-contradictory nonsense like "both a wave and a particle", one has to wonder at their own depth of understanding. A charitable explanation would be that the meaning of the terms "wave" and "particle" have changed over the decades while physicists are in denial about this fundamental shift and don't realize how out of sync they are with the general population. I'm not feeling charitable. Indoctrination In Physics would be an excellent essay topic for someone's Truth And Propaganda class. An entire WikiPage could be devoted to the subject of the physicists' class structure, how it grinds people down and how inimical it is to non-physicists (laypeople and academics both). So how did this fiasco come about? In the early days of Copenhagen, Niels Bohr used his enormous personal authority to push his extremely radical pet theory. Without his authority, Copenhagen would have been rejected on the sole grounds that it was too radical. One of the things Bohr liked about the theory was that it implied an Ultimate Observer who caused the wave collapse of the universe; it's an ugly scene whenever anyone tries to mix religion into science. Add to that the fact that absolutely nobody bothered to verify von Neumann's "proof" that the universe was non-deterministic for ''three decades'' and one gets a glimpse of the hierarchical and authoritarian nature of the scientific community. -- RichardKulisz A different problem with the CopenhagenInterpretationError is the way observation determines reality. People sometimes claim it removes the privileged position of the observer by recognizing him as an intrinsic part of any experiment. However, whereas normal interactions between wave-functions can't cause them to collapse, observation does - i.e. the observer is given powers beyond those of ordinary matter. In short, CartesianDualism is introduced into physics, with all its problems - a second major complaint of Einstein, Schroedinger et al. -- JG '''What does non-determinism mean?''' The meaning of non-determinism, if indeed the term has any, must be formalizable. It may take years or even decades to formalize this meaning but it must be possible to do so. It's already been nearly a century and despite the pressing need for just such a formal definition (or something resembling a formal definition), the adherents of the Copenhagen interpretation haven't advanced a single one. There are four possibilities: 1 branching 2 singularity 3 choice function 4 non-mathematics '''Branching''' If you have a Turing machine which replicates itself at every decision point in order to explore all possibilities, this is what mathematicians call non-determinism. Unfortunately for Copenhagen advocates, this is precisely what Everett's Many-Worlds theory does and it is understood to be perfectly deterministic. The result of a computation by a TuringMachine that replicates itself is not "an unknown and undetermined machine" among the set of machines that exist at that point in time, rather the result is the set of all the Turing machines that exist at that point in time. That set is well-defined. '''Singularity''' This is the mathematical concept that has the most uses in physics. Stephen Hawking claimed that black holes are non-singular and simultaneously claimed that Einstein was wrong so the two must be related, right? Not so. Setting aside the fact that the singularity of the universe is hotly contested, singularity doesn't have any of the qualitative properties ascribed to non-determinism. The outcome of multiplying a matrix by a singular matrix is very well-defined; the outcome of multiplying a matrix by a "non-deterministic" matrix is not supposed to be well-defined. But there seems to be a way to rescue the concept if you consider non-determinism to be the ''inverse'' of a singular matrix. Now we're getting close to non-determinism. Unfortunately, there are two interpretations of taking the inverse of a singular matrix. 1) you get the set of all matrices which multiplied with that matrix give you some identity, or 2) you get absolutely nothing. #1 gets you back to Branching and #2 clearly contradicts reality (the result of any allegedly non-deterministic experiment is always '''''something'''''). '''Choice function''' A choice function is a function that "selects" an element from a set. If you have a set with ten elements then there are ten possible choice functions on it. Choice functions are the only way to modify the CopenhagenInterpretation so as to make it intelligible without making it an entirely different theory (i.e., without making it into Many-Worlds). Unfortunately, it also immediately disproves the resultant theory. PhilosophyOfScience explains that its purpose is to explain everything we perceive around us in as concise and formal a manner as possible. So as it stands, the CopenhagenInterpretation is incomplete because it fails to explain everything. In fact, it explains almost nothing of what we perceive. The CopenhagenInterpretation doesn't explain how you get from a particle in state A at time t=0 to that particle in state B at time t=1 and the underlying quantum mechanical equations (which are fully deterministic since "non-deterministic math" is an incoherent concept) only tell you that the particle will evolve from state A at time t=0 to states B, C, D, and E at time t=1 (there's a story in here about how Copenhagenites abuse the mathematical concept of probability if someone wants to see me rant about physicists). So in order to complete the CopenhagenInterpretation you need to add a choice function to it that selects which state the particle will be in at time t=1. The problem is this. A complete theory of physics must explain all perceptions and all physical objects it defines. So the choice function that you add to the CopenhagenInterpretation must provide information on state changes of 10**70 particles (the estimated number of particles in the universe) for every time interval during which a state change can occur. And that time interval is short; if one were feeling uncharitable, one would choose Planck time (10**-43 seconds). And this is over the entire lifetime of the universe. If the universe has an open geometry then this means that the choice function must encode an infinite amount of information. But let's be charitable and assume that the choice function chosen contains only 10**100 bits of information. Now here is where the CopenhagenInterpretation dies. The complexity of the complete 'Copenhagen + choice function A' theory is greater than "God did it". From a formal point of view, there is nothing wrong with the theory "God created the universe" where you define; 1. 'the universe' = 'everything you perceive', and 1. 'God' = 'a powerful entity that would want to create the universe'. The only thing that's wrong with this theory is that it's ''too complex'' since 'the universe' must contain an exhaustive enumeration of every bit of perception you have ever and will ever experience. And yet, it's simpler than the CopenhagenInterpretation. '''Non-mathematics''' By that I mean only that 'non-determinism' is an undefined concept. Not the well-defined concept "undefined" but an undefined, null, meaningless concept. Per the above paragraph, this violates the philosophy of science and makes the CopenhagenInterpretation into incoherent nonsense. Hardline apologists for the CopenhagenInterpretation will claim "you can't explain everything" but how would they know when they've entirely given up on the endeavour? -- RichardKulisz ---- Ok, time for me to clean up the mess I made. In particular, anything I said about non-determinism in many-worlds was wrong, very wrong, and is being removed. Sorry, RK; it's easy to make mistakes when you're defending something you disagree with. Thanks for keeping me coherent. I still would say the above is unfair, though, since it assumes determinism as an axiom: "A complete theory of physics must explain all perceptions and all physical objects it defines." If you are going to try and evaluate non-determinism on its own merits, which it looks like the above is trying to do, you have to suspend that judgement (otherwise non-determinism is right out anyways). Non-determinism is a positive statement that science has fundamental limits ''(and most of the great theoretical work in the past century have had limiting results, Turing, Church, Goedel)''. It is not a scientific statement, but rather one about science itself, and those are a prerequisite to science existing. A quick way of stating non-determinism is that the information in the past is insufficient for predicting the future. The fundamental unrepeatability of some experiments gives some justification for this. As it turns out, though, non-determinism is not necessary unless you assume that the universe of observations is complete (singularity, right?) - Many-worlds is nicely deterministic, now that I am thinking about it properly. This is all for the good, because non-determinism is pretty ugly, ''but'' that doesn't change that it is a coherent philosophy, and it's unfair to say it isn't. The CopenhagenInterpretation is still a different matter, of course, and I don't think you can make it consistent without CartesianDualism. Btw, I still think it is a little bit strange that when you pick a world out of the Many-worlds hypothesis, you should use the square of the wave function as your distribution. But I guess that's what the wave function means, more or less, so it isn't so bad. All this sound ok to you? -- JoshuaGrosse More or less. I think the explanation of Many-World's determinism is interesting (I always get a kick out of the colour of Napoleon's white horse example) and I'll try to put it back in. From this point, there are two interesting points I'd like to discuss. One is the philosophical justification for determinism and the other is the conservation of information. As I stated earlier, determinism is a part of my definition of physical reality. Existence is just the property of a logical statement of belonging to some axiomatic system (I worked out this concept for myself before finding out Quine says the same thing). So objects physically exist if they are described by a statement in a particular axiomatic system. IOW, reality is nothing more than an axiomatic system. This observation is not enough since the term reality is still undefined, for now. Note that there are as many different types of existence as there are axiomatic systems. One very peculiar type of existence is the property shared by one's perceptions and conceptions (i.e., mental existence). One defines reality as the most elegant axiomatic system which explains the totality of mental reality. I can't see any alternatives to this definition of reality, there just aren't that many concepts involved. It may seem peculiar to define reality as a logical construct but this is a problem-free way of having an objective physical reality without dictating any of its properties a priori. For example, it is frequently stated that physical reality is something "out there" and that this is a fundamental axiom of metaphysics (of the nature of reality). To me this is very strange because before your acceptance of this axiom, reality was ''not'' out there. The axiom is essentially self-contradictory; how could your acceptance of the axiom of a physical reality affect the existence of an ''objective'' physical reality? One has no such problems with a definition because definitions merely attach labels to things which are already out there, they don't create anything new. Of course, this is the reverse of the impression most people have of definitions versus axioms. Given all that, I don't see any option but to have determinism. ''This strikes me as mostly sensible, but I suspect because it is a kindred thought - I tend to think about reality in terms of mathematical systems (a sort of Platonism I didn't expect to see on Wiki!). One thing that surprises me a little, though, is that you've made reality the system itself, rather than what the system contains.'' Actually, it's only Platonic if you're talking about the contents of the system instead of the system itself. Unless you're very careful at which point there's no difference between the two. Sometimes I make Platonic mistakes but I don't think it happens too often. :) ''Is that so? I thought Platonism was just a statement about mathematical systems existing...maybe this explains why people are so AntiPlatonic. But in this particular case, isn't reality more the contents of the system (physics) than the system itself? And what exactly does it mean for a system to exist, but its contents not to?'' Platonism says that the contents of mathematical systems exist regardless of people's ability to prove things about those contents. Consider prime pairs like 5 & 7 and 11 & 13. A Platonist would say that whether or not there exist an infinite number of prime pairs is an objective fact independent of our ability to prove it. A formalist would say that the existence of relations between the primes is independent of the existence of the primes themselves. Then he would go on to explain that though the existence of an infinite number of primes is established in most interesting algec systems by well-known theorems, the existence of an infinite number of prime pairs is a completely different thing. To a formalist, distinguishing between the contents of the system and the system itself is useless and very dangerous. ''Now hold on! What exactly is "ability to prove" something? Does it refer to whether or not people have bothered to do it? Does it refer to whether or not you believe people will ever be clever enough to do it? Or does this refer to formal decidability? These are very different things, you know!'' Ideally, it's #3 but in practice it's usually #2. :) Nobody can actually prove that the Continuum Hypothesis is undecidable, everyone just thinks it is. The problem lies in the fact that the decidability of a proposition is not always decidable. :) ''The continuum hypothesis was proved undecidable in terms of ZF by KurtGoedel and PaulCohen. Undecidability of undecidability could be a problem, but I'd like to ignore that for a second. Why is refuting that objects exist regardless of #3 a refutation of Platonism? It seems to me all that does is say that there are several different types of sets (eg ZF+CH-sets and ZF-CH-sets), just as there are different types of numbers, without impacting at all whether they "Truly" exist or not.'' Non-determinism is indeed a statement about information. It states that information is being created through some non-physical process. If this is so then one turns one's mind to the question of where this information comes from and also of the nature of the process which brings this information into the universe. There doesn't appear to be answers to these questions any more satisfactory than NeverNeverLand and Magic. Scratch that; there doesn't appear to be '''any''' answers and that's even less satisfactory than NeverNeverLand and Magic. ''You have to make this hard on me, don't you? Ok... since non-determinism is more or less a supposition that information is not conserved, it doesn't make a heck of a lot of sense to talk about where it's coming from; it simply isn't there yet. If you regard the universe like math systems as a SortOfPlatonicBlob where the future exists just as much as the past, this isn't too problematic...'' ''In particular, you can regard a causal universe as non-deterministic if it has time-delayed initial conditions. We can't know about these until they've happened, since we only see part of the universe - the past. But after one has activated you can tell it was there, and conclude the universe is nd. I agree, though, that this is really ugly and really unsatisfying and I'm not particularly surprised experiment doesn't indicate this.'' If you do it on any kind of large scale it's intolerable but on a small scale it makes sense the way you explained it. One difference between the initial conditions and non-determinismic effects is that the former are located at an edge of the universe whereas the latter are embedded within it. So in the former case, it's possible to think of the information as coming from somewhere (e.g., a previous universe) even if knowledge of that place is inaccessible to us. Of course, the creation of information is just the reverse of its destruction. Here's where I strongly disagree with Hawking. Most cosmologists do too. So much so that they're willing to accept looney ideas like "the remnants of exploding black holes get sucked into other universes" rather than accept the destruction of information. I believe a slightly less extreme solution to the problem. Basically, physical information is convertible into digital information and vice versa. This also means that physical entropy is convertible into digital entropy. But this provides an insight into entropy since the difference between digital information and digital entropy is just that the latter is useless junk to people. Entropy is information that happens to be junk. There's a more important insight; a ReversibleComputer (a deterministic universe) can uncompute information into its original compact form. That's what I think is going on in the case of black hole evaporation; not the destruction of information but its uncomputation. ''Ah, down here conversation is free, free from non-determinism! Btw, I'm not quite sure what the formal definition of physical info is, would you care to help me out? Also, I'm not convinced a deterministic universe is necessarily reversible. Why can't the universe be like Conway's GameOfLife... causal, deterministic and irreversible? -- JG'' All I know about the nature of information is that it shares the same units as entropy and that it always increases (thermodynamics). I don't know enough information physics to say more. The term for irreversible determinism is 'singular'. I like determinism. :) ''Well, that's enough to rule out Conway...information is clearly decreasing. But doesn't that also rule out what you said before - namely that information is never created? This would seem to me to imply that info is constant.'' It depends how you calculate it. If you copy a file, you haven't actually increased the information in your computer. Same with compressing or uncompressing a file. You're not creating information, just modifying its form. If the universe is deterministic then information is never created. If it is non-singular then it is never destroyed. Thermodynamics can be interpreted as an approximation or an illusion caused by the expansion of the universe. I will illustrate with an example. Suppose you create a copy of a file in a perfectly reversible computer (which ours are not but the universe theoretically is) then you could always uncopy (though never erase) the file to get back a single copy. Now suppose that your computer sends the copy to my computer, so far no problem, and then our computers are carried along by the expansion of the universe so that they can no longer communicate with each other. In that case, I could never send back the copy to you for it to be uncopied and our computer network would be stuck with two copies. ''This needs more refactoring. At the same time, I think some info on philosophies other than Copenhagen should be mentioned...as fun as it is to complain about prevalent idiocy, potential truths are more important. You would probably be better at writing up ManyWorlds stuff than I would.'' Possibly. I still don't understand in what way it violates the assumptions of BellsInequality. ''The explanation given in that FAQ is pretty obtuse, but I don't think anything's wrong with it per se. It seems to me to be saying that rather than splitting everywhere instantaneously (poorly defined relativistically anyway), they sort of peal apart as info of an event spreads outward...normally you think of the second detector's value as being determined where the particle reaches it. Then the only way the two can be related is if there was FTL info transmission. But with this model the results aren't determined (i.e. it is decided what someone who saw a spin-up at detector I) until later, when they reach the info cone where the worlds are splitting. Or at least that's what I read into it. It's easy to justify something to yourself, and as I said, the FAQ was somewhat confusing.'' That's what I got from the FAQ but that's not the part that's confusing me. The FAQ explains that Many-Worlds violates the ContraFactual Definiteness assumption of BellsInequality and then goes on to define CFD in a way that makes no sense to me .... ''I think all it's saying is that CFD means measurable quantities exist regardless of whether they actually have been measured. If that's it, the many-worlds model violates this trivially, since measurable quantities are many-valued until you pick what world you're looking at.'' ---- '''Book Recommendations:''' Since there is a deluge of trash on quantum mechanics reprinted from decades past, it is imperative to be able to weed the wheat from the chaff. 'Quantum Reality' undermines the Heisenberg Uncertainty Principle by, all too briefly, explaining entanglement in a coherent manner. Unfortunately it never calls attention to that fact. It doesn't have a very clear explanation of Bell's Theorem though it at least gives one. It seems to predate most of the developments of Many-Worlds and so gives the theory short shrift. Not a very good book but at least ''somewhat'' consistent with modern developments. The Many-Worlds FAQ available online is pretty good though not stellar. It makes a mess of Bell's Theorem too. John Cramer's paper on the TransactionalInterpretation: http://www.npl.washington.edu/npl/int_rep/tiqm/TI_toc.html The '''''excellent''''' pages at http://www.mathpages.com/rr/rrtoc.htm are highly recommended for their outstanding clarity in dealing with advanced concepts. Section 9.6 explains von Neumann's "proof" that hidden variable theories are impossible and why that "proof" is meaningless and horrible. Section 9.7 explains why Bell's theorem is incorrect (its conclusion can be found in its assumptions and its assumptions are absurd to begin with). Section 9.8 proves that all attempts to prove our universe is non-deterministic (or even merely unpredictable) will ''always'' assume their conclusions and can ''never'' be verified to apply to our reality. And in between those chapters, it's also explained why people cling to such a destructive and anti-scientific idea as non-determinism. ---- I agree that the interpretational foundations of Quantum Mechanics is a worthwhile subject of study. However, while the various forms of the Copenhagen interpretation may be deeply unsatisfying to many (including myself), they are not necessarily inconsistent, deprecated or "fundamentally unscientific" as alleged above. Readers of this page can do worse than measure some of the contributions against the index described at: http://math.ucr.edu/home/baez/crackpot.html My calculation based on certain sections of this page came to -5 (starting credit) + 1 (point 2) + 10 (point 9) + 10 (point 16) + 10 (point 17) + 10 (point 18) + 40 (point 29) + 40 (point 31) = 116. Nobody has claimed that quantum mechanics is fundamentally misguided. Copenhagen is '''not''' QM. (point 9) Insofar as Copenhagen predicts nothing (because it only gives "statistical" predictions), it is widely agreed in the scientific community that it does not. (point 16) Nobody has claimed on this page that GR is fundamentally misguided, nor compared themselves to Einstein. (point 17) Nobody has claimed that their contributions constitute significant "work" (I've always felt my contributions to be in the "bloody freaking obvious" category), so such non-existent work has never been claimed to be on the "cutting edge of a paradigm shift". (point 18) Nobody has claimed that there is a conspiracy to prevent them from getting fame or credit. (point 29) The actual claim is of narrow class interests working against society as a whole. Nobody has claimed that the insights on this page will ever significantly contribute to revealing Copenhagen for the sham it is. (point 31) So the actual crackpot score of this page is -4. You're obviously just a hidebound reactionary (score 16) and self-appointed defender of the orthodoxy!! (score 36 and still a ways to go before we reach 116) As for Copenhagen being inconsistent, nobody has claimed so, except maybe inconsistent with reality and with having a gram of common sense. Here's some advice you should consider: read this page before passing judgement on it. Finally, if there is a mathematical proof that non-determinism can never be proved (and it should be obvious that it cannot), Copenhagen '''is''' fundamentally anti-scientific gibberish as well as deprecated (stillborn would have been better) One mathematical proof by Chaitin trumps generations of idiot physicists preaching their sham religion. Note that non-determinism isn't an issue on which reasonable people can disagree because it has never been treated that way. It has always been used as the sine qua non of quantum mechanics by idiot physicists. If your n was , you "got it", whereas if you thought the whole thing was absurd gibberish, you "just didn't get it". It's time for some payback from those who have committed crimes against science. Perhaps some show trials in which they're forced to recant... (point 31, score 66) ---- ''Just to be sure. Apart from all the emotion, I take it your problem with the Copenhagen interpretation is that it assumes the causal independence of the measuring system from the measured system?'' No! There are about two dozen different problems with Copenhagen. "causal independence of the measuring system from the measured system" doesn't have anything to do with why Copenhagen is intolerable but with why Bell's Theorem is nonsense. ''If so then the many-worlds interpretation isn't required. A simple 'limit of knowledge' approach does fine. For me the Heisenberg Uncertainty principle simply says that our uncertainty of our own linkage to what is being measured is reflected in the uncertainty of our measurements. Are we on the same track here?'' No! And you are so flat wrong too. First "uncertainty" is a bullshit concept. If you know anything about 21st century (or even mid-20th) quantum mechanics, you'd know that too. The concept is a holdover from the very beginnings of quantum mechanics, back when people refused to think of quantum phenomena in anything but a classical manner. So given that the basic concepts you're dealing with are nonsense, I don't even care to see how you've put them together. ''Many-worlds expresses a global determinism compatible with a local observers non-determinism but it still makes this local non-determinism a matter of principle, like it is impossible in principle for the particular universe which the measurer will occupy to be known in advance. I find this unsatisfying, though that is highly likely due to my own limit of knowledge :).'' You're able to say "the particular universe which the measurer will occupy" only because you don't understand Many-Worlds. If you understood it, you'd know that phrase is nonsense. ''Can we not take a more conservative approach and say that it is unlikely, as a matter of fact, that we will know everything about the entire history of our (singular) universe that led to the particular event we are observing? Thus the indeterminism could be simply a matter of ignorance?'' No! That's 19th century mechanics, which has been disproved time and time again. ''I think of this as the 'singular interpretation', which is rather an old one (a few thousand years or so). I would be very interested in what I am missing (or not).'' The entire 20th century apparently. ''Okay. So perhaps you might display your knowledge rather than asserting it? As far as I understand it these pages are supposed to be educative rather than performance zones. One assertion above is that physicists have deliberately obfuscated the simplicity of what is 'really' going on. So make it simple. Make your case.'' ---- ''If so then the many-worlds interpretation isn't required. A simple 'limit of knowledge' approach does fine. For me, the Heisenberg Uncertainty principle simply says that our uncertainty of our own linkage to what is being measured is reflected in the uncertainty of our measurements. Are we on the same track here?'' There are a couple of different versions of uncertainty. Heisenberg's original interpretation was that some quantities couldn't be measured simultaneously, because measuring one altered the other. Bohr's interpretation was that complementary quantities didn't simultaneously exist until measured. The proper version has to do with the spread of the wave function, and is a simple property of Fourier transforms. I don't recognize ''any'' of these in the above statement. What's linkage? ---- Perhaps of interest; Pilot wave theory is a deterministic formalism that can reproduce all (if I recall correctly) QM results. ''Some quick searches find a number of difficulties with pilot waves: for instance dealing with relativistic effects, dealing with antiparticles, and dealing with the special status of observers.'' ---- Wow. Five rants on one page. ---- See also GrandUnifiedTheory, QuantumMechanics, TransactionalInterpretation CategoryPhysics CategoryWikipediaLink