Comments by "Lepi Doptera" (@lepidoptera9337) on "The Trouble with Many Worlds" video.

  1. No, she doesn't. The trouble with MWI is so large that somebody has collected a list of like 60 major arguments against it, if I remember correctly. It doesn't matter, though. MWI is both physical and philosophical bullshit made up by a failed physicist and popularized by people who know that bullshit sells better than reality. It is really pointless to waste any time on it. What really matters is that people understand why Copenhagen, which is being decried as "incomplete" and worse is actually the physically correct description... within its very limited range of applicability (non-relativistic quantum mechanics is not a good theory and we should really not be teaching it as if it was). I think you will see a change in physics education, both at the high school and the university levels, that will correct the 19th century misconceptions that are still being taught. Be the end of the 21st century every kid will be given the tools to understand 20th century physics. :-)
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  2. MW is not a physical theory. It's some old nonsense that has gained new popularity on the internet. MW to physics is like horse-dewormer and aquarium cleaner are to medicine.
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  3. So you never went to the library to read up on the things that your teacher didn't tell you? I did.
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  4. Copenhagen doesn't make any assumptions about the observer. All it requires is irreversibility. There are trivial quantum processes that are irreversible without any classical observer system. This follows directly from special relativity which separates the world sharply in forward and backward light cones. The problem that you have in non_relativistic single particle quantum theory is that you have so over-simplified the world that you are losing the very effects that cause classical states to appear in the first place. This problem doesn't exist in relativistic quantum field theory and that's why "interpretations" are not required in high energy physics at all. Nature separates local reversible dynamics and global irreversibly dynamics for us automatically. All exact observables are simply living at infinity and any and all attempts to "zoom in" trivially results in a non-classical "smeared out" description of the world. People who have experience with a regular light microscope are familiar with that: no matter how good the objective lenses are, at higher magnification the "images" are always blurry. That's not an engineering limitation. That's nature showing us that reality is locally simply "not in focus".
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  5. I have never seen "multiple possible timelines" in QFT. Where did you get that from? There is no detector problem. "Detection" or "observation" is merely an irreversible energy transfer from the quantum system to an external system. There is absolutely nothing difficult about it, either philosophically or from a physicist's point of view. A good detector for photons has to be "black" in the spectral range of interest or it will simply not absorb the photons. A good detector for electrons might be shielded with a dedicated field grid that prevents them from leaving the collection anode. Physicists deliberately engineer detectors to be close to ideal thermodynamic absorbers, i.e. we know what we are trying to achieve at the level of experimentalists. No additional theory needed.
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  6.  @jth4242  Feynman diagrams are not representing physical processes in a spatial representation. That's just a trivializing explanation for the masses. The physics is in the sum of an infinite number of these diagrams, most of which will actually cancel out in well defined quantum field theories. Either way there is only one "timeline" in these diagrams because we are working in a single (relativistic) frame. Nature does not do any of what is going on in these diagrams, to begin with. They are an artifact of a quantization procedure (path integrals) that doesn't give us many good options to actually calculate theories with interaction terms. The infinite nested integrals that result from it can only be solved in closed for for gaussian wave packets, i.e. non-interacting systems. The interesting case requires a perturbation procedure which leads to non-physical "virtual particles", none of which can ever be observed in nature. I believe that they have found some interesting internal symmetries of this mathematical problem lately that allows shortcuts for these calculations in some cases (see "amplituhedron"). That may get us finally going in the right direction to understanding what the actual physical structure of quantum fields are.
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  7.  @jth4242  I didn't say that it's impossible to derive actual physical "elementary processes". What I said is that Feynman diagrams are not equivalent to these processes. That does not mean that there are no other representations of the behavior of quantum fields that can yield a much better interpretation. Personally I strongly suspect that there are and I gave you an example of recent theoretical insight into one possible such avenue. The problem with Feynman diagrams is simply that they weren't derived from physical insight but they are a purely mathematical necessity to get through the calculations in a naive way, at all. Why are Feynman diagrams like that? Because the path integral formulation of quantum mechanics, which is a quantization procedure, basically assumes that one can describe the world in terms of quanta, which are irreversible energy exchanges at the boundary of a quantum field. By pushing this irreversibility (that does not exist there) into the volume, we are opening up a whole slew of mathematical problems, which we then have to solve with more or less ad-hoc methods. Even our best solutions have remnants of trouble (like an extremely high calculated vacuum self-energy term) that do not exist in nature. In nature quantum fields behave like extremely smooth objects all the way across the universe (if they didn't, then we couldn't see all the way back to the beginning of time with telescopes). There are no dizzying virtual particles popping in and out of existence all over the place as poor visualizations of spacetime want to make you believe. Atoms in the ground state remain in the grounds state until actively excited etc... all of this tells you that something in our math is wrong. It's good enough to calculate a lot of things, but it's still not good enough to be satisfied with it. And we aren't. That's why very smart people are still thinking about the problem. QFT with Feynman diagrams is, by far, not the last word, neither mathematically nor in terms of physical interpretation.
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  8.  @jth4242  Religion is the occupation that tells you about events that didn't happen. Physics tells you about physical dynamics that can not be described in terms of classical events. I don't think you should rely on Sabine Hossenfelder too much in this area. She seems to have fallen into a rabbit hole about quantum mechanics herself.
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  9.  @jth4242  I am an experimentalist. A theory has only one function: it has to describe everything that is experimentally and observationally accessible within its range of application. If it does that, it's all good. I do not need a philosophical layer with imagined additional requirements of beauty, "realism" or whatever fancy ideas philosophers who have never set foot in a lab may assert to insert themselves into my ballgame. That's the same "attitude" that you will find in NFL coaches and players with regards to armchair coaching. Either you are willing to play or you are not. Either you take the daily punches of the game or you don't. If you don't, then please stay away from the field. That's not a statement about you personally. It's a statement about "philosophy" in science.
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  10.  @jth4242  Does the accreditation of the author decide about the quality of a paper? No. In physics the experiments and observations decide. If you don't like that rule, then physics and science in general are not the right games for you.
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  11.  @jth4242  Where did I introduce an argument of authority? Nature is the only authority in science. Either a scientist can correctly describe nature or he/she can't. Everything else is silliness. At this point I think you need to go back to basics.
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  12.  @jth4242  I told you that people need to either learn to play like a pro or to get out. That is another example of somebody not listening to details. See, I told you physics is detail oriented. You took it seriously and you didn't even notice the invitation to the real game.
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  13. @Imjust Observing Where did I say that there is such a thing as a wave function collapse? That's just unphysical nonsense.
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  14. @Imjust Observing Nature doesn't know about systems. The physicist defines them at will. We simply have to verify that they behave like the way we say they do. You are correct, the entire universe is just one quantum field, but much of it behaves classically for the purposes of physics. The trick is to know when, where and why.
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  15. @Imjust Observing Violation of any of the conservation laws. I don't know if you guys are aware of this (it does not seem you are), but an atom has to be brought into an excited state to release a photon. That means that a mixed state between exited and ground-state is simply some of the ensemble being in the excited state and some of it being in the ground state. The same atom, however, can never be in both states at the same time because that energy will, eventually, have to be released. Energy that is not in the system can not be released. Energy that is in the system can not stay in it forever because of the decay time constant. Goodness, gracious, kids. This ain't rocket science. One simply has to be able to distinguish between ensemble properties and individual system properties. What QM can't tell us for mixed states is which of the actual states one particular atom is in, that's all. This does have severe consequences for the phase space of systems that have many degrees of freedom, but even for those the total energy is the total energy, no matter how much it spreads out over the mix. You can make the same argument for any conserved quantity. Momentum, angular momentum, spin, charge, lepton number, whatever. These conservation laws are not just being obeyed in the average. They are being obeyed by any one of the samples in the ensemble. To think otherwise is unphysical. Maybe you really need to take a few lab classes in the atomic physics department to remind yourself how nature actually works. That is the problem with all this double slit nonsense and Schroedinger's cat etc. These toy examples do not force you to think about real physics. They all gloss over all the stuff that is of actual importance in real world experiments. Do you really think we would build a multi-billion dollar 17km circumference accelerator if protons would be equally likely in all possible momentum states????? Seriously? End rant.
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  16. @Imjust Observing Single protons don't have any uncertainty. We have to measure the momentum of many protons to calculate an uncertainty.
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  17. @Imjust Observing Rationalism in science means that you describe what you measure. I, for one, have never measured a wave function and certainly not on a single system. When I measure a single photon, I get one energy value, one momentum value and one spin value. That's it. That is rational. Whatever else you think there is to it is entirely a construct of your mind. It does not have an equivalent in an experimental setup.
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  18. @Imjust Observing There are no operators in nature. That's formalism. In nature you can measure a few physical quantities at a time on quanta. Which quantities those are is given by the symmetries of spacetime (or, if you make e.g. 2d systems in solid state experiments by those local symmetries). When you measure photons you get energy, momentum and spin. An electron throws a a non-zero electric charge and a lepton number in there for you. Have you ever done actual measurements on quantum systems? There are no operators involved. It's all metal, vacuum, electric fields etc..
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  19. @Imjust Observing With regards to "collapse"... can you give me the experimental apparatus design to measure collapse? I have never seen a "collapsor" in my life. Not at CERN, not at atomic physics labs. It wasn't shown to me in my lectures on quantum mechanics, either. It must be a very rare apparatus, indeed, because no physicist I know personally has ever seen one, either. It's almost like the Santa Claus sled of physics. :-)
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  20. @Imjust Observing A detector is an irreversible energy transfer from a quantum field to an external system. A lump of coal will do nicely. Greetings from Farmhand Rupert. :-)
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  21. @Imjust Observing So you are still dreaming about a collapsor. Let me know when you have figured out what a photomultiplier tube does. Hint... it's a little bit like a solar panel. So what does that device do? Can you guess how they are related? :-)
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  22. @Imjust Observing What "decides"? The same that makes Earth go around the sun. What do you call that mechanism?
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  23. You don't know. We do. That's the truth. :-)
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  24. There are no such things as particles, to begin with. That is already a trivial misinterpretation of our observations.
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  25. The wave function is not a physical entity. It's just book keeping for what happens in case of an infinite number of identical experiments. It is no different from a probability distribution that way.
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  26. Yes, we do know "the full inner workings of the machinery". They are being described by quantum field theory.
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  27.  @2tehnik  No, QFT doesn't use measurement in the sense of non-relativistic QM. The only relevant quantities in QFT are scattering matrix elements and those have a perfectly natural interpretation in terms of plane waves coming in from infinity being scattered back to plane waves that are going out towards infinity... which is exactly the same as what our eyes do... plane waves from a light source illuminate an object, which then scatters the light back and we look at it and can tell by the colors and shapes what that object is. Turns out that nature behaves the same at the deepest level as it does in everyday life. All the QM measurement stuff was always just decoration on top of what nature prescribes herself.
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  28.  @2tehnik  All the measurement bullshit comes from people who didn't study relativistic quantum field theory or, if they did, lack the intuition to connect it to the fundamental questions of "reality" in quantum mechanics. Historically the study of quantum mechanical systems basically split at the end of the 1920s, shortly after the more or less final version of non-relativistic quantum mechanics was agreed upon. A number of physicists who were interested in low energy systems like solid matter and atomic and molecular spectra kept working with the non-relativistic theory, which can achieve reasonable accuracy for a number of problems but suffers from (mostly imaginary) interpretation issues because it is not a good theory of the world in general. It just happens to work if we squint and don't care too much about certain details. That's exactly how classical mechanics works in comparison to relativity. It's conceptually false but still good enough for many simple problems. The more serious faction of physicists like Dirac, however, realized immediately that non-relativistic QM was both insufficient and a kluge. They began to construct relativistic versions of the theory, initially very much in the style of the Schroedinger equation. These early attempts produced enormous mathematical problems and were very hard to work with. More importantly, they did not reproduce the plethora of ever higher energy physics data that came from ever more energetic accelerators easily. It took these physicists twenty years (all the way towards the late 1940s) to develop mathematical methods that could tackle non-trivial problems (like Feynman's path integrals and Feynman diagrams). It took another twenty years (bringing us closer to the 1970s) to tackle divergence problems and to develop what is called gauge theory that is the backbone of the standard model of physics. As a by-product of these mathematically very challenging problems the comparatively trivial issues of quantum mechanical measurement etc. are falling by the wayside completely. It is trivial to explain the source of uncertainty in a relativistic worldview and it is just as trivial to explain why the world seems to reduce to classical physics on its own without somebody staring at it all the time. So why are there still people who just can't take the relativistic quantum field theory "yes" for an answer? Beats me. Some people just don't want to get out of their Schroedinger comfort zone, I guess, no matter how poorly it matches to actual reality.
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  29.  @2tehnik  The uncertainty simply stems from the fact that in relativity outgoing waves can't return. A local phenomenon that sets off a wave that propagates at the speed of light is automatically entangled with something that is irreversible and the state of which is therefor unknowable. Classically speaking one can't catch a light wave in any coordinate system (because light waves always move at the speed of light), hence whatever energy, momentum, angular momentum was transferred to that field is lost forever. It's not much of a mystery, really.
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  30.  @2tehnik  Entanglement is nothing but global symmetries combined with quantum mechanics. Energy, momentum, angular momentum and charge conservation. Trivial.
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  31.  @2tehnik  I just went out on my balcony and turned my flashlight on. It ran for 1 minute. The beam has a length of 18 million km and is moving away from Earth towards the center of the galaxy at the speed of light. Please go and catch it for me. ;-)
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  32.  @2tehnik  It doesn't connect to the double slit because the double slit is not even a quantum experiment. ;-)
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  33.  @2tehnik  It produces the hyperfine structure. :-)
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  34. I can only see one world.
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  35. You can't perform either experiment because there are no particles in nature.
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  36. An "observer" and an "emitter" are irreversible processes. A beam splitter is a reversible one. That's the difference.
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  37. The observer's quantum state doesn't become entangled, either. Entanglement is a reversible phenomenon. Observations are irreversible. People who are barking up the entanglement tree understand neither entanglement nor observation, even though the difference is absolutely trivial.
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  38.  @57Cell  What about "irreversibility" did you not understand just now? :-)
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  39.  @57Cell  Observation is irreversible energy transfer. You seem to have difficulties reading. :-)
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  40.  @57Cell  Why are you telling me that you failed in high school physics? You were shown simple irreversible systems. Why can't you remember them?????
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  41.  @57Cell  An inclined plane ending in an infinite flat is dynamically irreversible. Once you let go of a ball on the inclined plane it will pick up velocity until it reaches the flat part and then keep rolling to infinity. Dude, I can't help it that you are clueless about physics. You simply didn't pay attention in high school. :-)
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  42. Reductionism isn't even necessary. What would be necessary is an understanding of actual experimental physics, but most people who are engaged in the foundations of quantum mechanics lack that sorely.
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  43. Yes, you could try that... so now you are generating an energy uncertainty of 1.96e9J every 5.4e-44s. This amounts to an average power output of your measurement apparatus of 3.6e52W which is almost 2000 times the total luminosity of the observable universe (2e49W). Let me know when your electricity provider is done installing the new power lines. :-)
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  44.  @jamesruscheinski8602  Only if you have lots of very energetic photons. Given the power of your measurement device I wouldn't worry about photons. The whole thing would have formed a supermassive black hole before you could even say "Oops!".
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  45. There is no particle, to begin with. There are only quanta (of energy). The Born rule has been derived in different ways from different more fundamental principles. Even Sabine Hossenfelder wrote a recent paper about it. More importantly, the Born rule is only exact if the universe is unitary and hermetic. There are good reasons to assume that at the cosmic scale and in the presence of very strong gravity it is neither.
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  46.  @mathiaslist6705  I would suggest the entire physics library. ;-)
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  47. No, of course not. It would not even be good physics at the high school level. The problems MW tries to address have been solved or better "be made obsolete" by relativistic quantum mechanics (quantum field theory) in the 1930s. It had long been made unnecessary by the time it was even proposed.
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  48. Attention! Attention! World renown physicist Biao Wu is now going to give a lecture on the often misunderstood MW interpretation and probabilities in general! Everybody please drop everything you are doing and pay attention! This will be a life-changing opportunity to grow our minds! A warm welcome everybody for Dr. Wu!
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  49. It's much worse than that because here we are dealing with a lot of real valued measurements (energy is not quantized). Hence the cardinality of the many worlds universe is, at least aleph_1. A more detailed analysis will probably drive this even higher.
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  50. Observers are special. They are irreversible processes. Not every physical process is irreversible, therefor not every process is automatically an observer process.
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  51. A quantum is field energy. You don't have to dig any deeper than that.
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  52.  @rustyosgood5667  In case of photons the electromagnetic field. In case of electrons an electron field etc.. In totality these fields form the physical vacuum. At low energy they are separable, at high energy they are not. Once they separate and weak measurement conditions are applied, emergent qualities like classical matter and its "paths" are being recovered. There is not nearly as much "magic" here as poor explanations on the internet suggest. It's really not all that much different than gas/liquid/solid phase transitions. Gases take in any volume they are given, liquids condense to near constant density and solids can have lasting shapes, which neither liquids nor gases produce. The physical vacuum is merely the next quantum step beyond the usual "phases of matter" classification.
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  53.  @rustyosgood5667  Yes, the theory has all of these. Nature doesn't, of course. It's all one vacuum, we are merely separating these observations to make the physics easier to digest for humans. That's what science does. It reduces to make things easy enough for the human mind. It already did that in classical mechanics, you just didn't notice. Non-physicists rarely have that level of structural insight. :-)
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  54. There has been no need for interpretations since the mid 1930s to late 1940s, depending on how we historically qualify the serious beginnings of quantum field theory.
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  55.  @twokidsmovies  MWI was invented by a failed physicist in 1957 and it was popularized in the 70s by DeWitt. The latter would have happened years after the prediction of the Higgs, kid. You really need to use your mind for other stuff than failed history. :-)
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  56.  @twokidsmovies  Dude, I have a PhD in physics and I have been reading up on these issues (including most of the founder's papers and the early quantum field literature) for over 20 years to understand who knew what and when. You are just a kid with physics Dunning Kruger who has never set foot in a physics library. Wise up, kid. You are making a fool of yourself here. :-)
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  57.  @twokidsmovies  Graduate program, huh? So, kid, what causes the structure of the Copenhagen interpretation to be what it is? On your level you should know this and I am sure you can give us a proper physical explanation in a few sentences. I am looking forward to learning from you. :-)
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  58.  @twokidsmovies  In other words, you don't know. See how easy it was for you to make a fool out of yourself? ;-)
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  59.  @twokidsmovies  I just looked into my drawer... and there it is... a physics PhD diploma of one of the world's leading universities in my name. :-)
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  60.  @twokidsmovies  I just looked again. The diploma is still there. It must be a classical object. ;-)
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  61. The words "decoherence" and "entanglement" are just as deceptive to the average person as MWI. They all hide the real physics that is going on behind completely irrelevant explanation attempts.
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  62.  @dinobotpwnz  No, it's not. The real physics is that every measurement removes a quantum of energy from the system. That is what really causes the system to "collapse" (which was always a completely superfluous and nonsensical term). You are changing it irreversibly. If you don't know that, then you have never done a quantum experiment in your life. I suspect that you haven't, and that's why you can't correlate the formalism with the real world phenomenology.
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  63. I don't know any physicist personally who believes in this and I know a lot of physicists. The people who "give credence" are probably almost entirely embedded in the internet culture and are milking the idea for money.
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  64.  @jimmybrice6360  No, he gave up being a physicist when he noticed that religious preacher and motivational speaker pays better.
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  65.  @jimmybrice6360  If you want to find real physicist on the internet, then you can go to the physics stack exchange. Those folks are the real deal. Tyson is a physics educator. He does it well, but within the limitations of how one can communicate physics to a wider audience. Most of the folks who are writing books for laymen are under the usual commercial pressure and they are human. Humans give in. When your editor tells you to water it down and to pep it up or to get out of his office because he can't afford to sell three copies of your scientifically precise horse tranquilizer, then you do what humans do. You go with the flow, which goes towards fake news, even in the laymen literature. Many worlds is a side show. There are fundamental problems in quantum mechanics, but not of the kind that many worlds is trying to cure. Anything that has to do with the double slit is bad physics, for instance, but unfortunately of the kind that is even being taught in undergraduate university classes. There are trivial things in every field that are just so cringeworthy that nobody even notices them any longer. They are just being retold to every new generation, which then adopts them without questioning. Unfortunately, that is the "salacious" material that makes it to the internet and into books and on tv.
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  66.  @jimmybrice6360  Well, then I got bad news for you. The double slit works just as well with goats and a sack of potatoes in the room, which obviously proves that human, goat and potato consciousness are completely equivalent. :-)
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  67. Being a realist you should want to read up on the Noether theorem and why it doesn't apply to the universe as a whole.
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  68.  @wayneyadams  Yes, that is exactly the problem. You need to learn physics to talk about energy. :-)
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  69.  @wayneyadams  No, your "masters degree in physics" is obviously not good enough. :-)
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  70.  @wayneyadams  I didn't have to damage anything. A person who starts out with "physics is the way I say it is because I have a masters degree in physics" is damaged goods already. Grow up.
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  71.  @wayneyadams  No, kid, physics is the way NATURE says it is.
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  72.  @wayneyadams  Exactly. Did I mention that I have a PhD in physics? ;-)
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  73.  @wayneyadams  I used to work as a physicist, including at CERN. Why does that matter to nature, again? Unlike you nature is not a sucker for authority. So why are you? :-)
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  74.  @greghansen38  I didn't say that you needed to read up on interpretations. As you said, they are not useful. They are also not necessary. Nature gives you a natural physical interpretation in quantum field theory. The problem with "quantum mechanics for beginners" is that they are not actually teaching you real physics. The world does not behave anywhere close to what non-relativistic QM suggests. If you were to try to probe the location of an electron inside an atom with ever higher precision, for instance, then all you would achieve is to ionize the atom. If you then ramp up the precision of your measurement by another three to four or orders of magnitude, what you get is not one electron but pair production of electron-positron pairs. At a few hundred MeV of probe energy muons will pop out, then taus and eventually quarks and gluons and W and Z. We have no idea what cute stuff happens at 10TeV. Non-relativistic QM is not even a theory. It does not describe the world correctly except in a very narrow range of energies. It does have the advantage of being simple, but that comes at the disadvantage of being non-physical. Reality is much more complicated mathematically, but ontologically it's much, much less convoluted than non-relativistic QM suggests. That is what your teachers didn't tell you... they simply didn't know.
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  75.  @greghansen38  Scattering matrices don't have ontological problems. They are describing the scattering of waves from infinity with the outgoing solutions also being probed at infinity. This eliminates questions like "what is a measurement" completely (not that that's hard to answer in non-relativistic QM but one has to drag thermodynamics into the mix, which is not necessary in relativistic theory). It eliminates the classical-quantum system boundary. Infinity always provides more than enough degrees of freedom for decoherence without having to construct "measurement objects". Phase doesn't matter at infinity, it all automatically boils down to amplitudes, just to name a few advantages. I do agree with you all the way that we are not teaching classical scattering theory nearly enough. It is extremely important in practice (optics, electromagnetic systems engineering, radar, medical imaging etc.) but the average physics student gets to see almost nothing about it. I certainly didn't, except for a trivial 2-d Coulomb toy problem. We also didn't learn relativistic dynamics enough to have a solid handle on collisions and high-boost systems. That leaves accelerator physics mostly in the dark, even from a classical perspective. I was taught some nuclear physics, but basically all in the non-relativistic approximation. High energy physics? Forget about it. That, however, is the real "footprint" of the universe. OK, it would have been different at a university that had an active high energy physics program, but even those lectures (I took them later as part of my PhD) were kind of very basic and insufficient to understand QFT on more than a surface level. One can, of course, learn important lessons about QM from atomic, molecular and solid state physics, but the fact that we are teaching the formalism independently of its applications makes connecting the dots harder, IMHO. I hope that younger professors are slowly getting a better handle on how to give students a working knowledge of QM, because for sure mine didn't.
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  76.  @greghansen38  How does scattering hide the ontological problems? Do your eyes have ontological problems seeing? Is the sun in a quantum superposition between day and night when it shines? Of course not. By referencing everything to infinity you have a perfectly classical reference surface because it has an infinite (i.e. large enough) number of uncorrelated degrees of freedom that will disentangle all physical observables for you. No such thing can ever exist in a closed volume. In a closed volume we are always running into the recurrence problem, which is no different from classical physics. Infinity is and always was the solution to recurrence, to statistical mechanics and it is the solution to quantum mechanics. People are just so afraid of it that they desperately try to remove it from their systems, which necessarily ends in inconsistencies. Nature doesn't have that problem. It even gave you an expanding universe to make absolutely sure that there is a true event horizon at a finite distance in which absolutely everything disappears without ever coming back. The perfect MS Windows waste basket. Absolutely spyware proof. Use it! :-)
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  77.  @mindyourbusiness4440  You should be interested in learning physics, instead. Take a good class on atomic physics, then another good one on nuclear physics and then, for god's sake, take a class on phenomenological high energy physics. You will soon see how silly the interpretation thing really is.
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  78. Entanglement is reversible, measurement is irreversible. Your physics DK is showing, kid.
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  79. That is actually exactly the wrong way around. The major quality of a measurement is that it produces an irreversible result, i.e. it has changed the world forever.
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  80. No, that's not it. You just got an F in physics, just like Everett. ;-)
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  81. Because he doesn't care about an actual debate. It is just his way of milking the public.
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  82.  @scottk7515  The issue was solved in the 1950s when the idea was born and absolutely nobody gave a frell.
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  83.  @scottk7515  No, it rests on what it can predict. MW can't predict anything but needs an infinity of an infinity of an infinity of copies of the universe to do so. :-)
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  84. The trouble with statements like that is that there are no "particles" in quantum mechanics. There are only field quanta, which are irreversible energy, momentum, angular momentum and charge exchanges between different artificially defined parts of quantum fields ("systems", usually called "particle source", "particle" and "detector"). The often repeated semi-classical ontology that naive non-relativistic QM assigns to these "systems" is physically (by which I mean in an experimentally testable way) simply not realized. Even in non-relativistic QM the notion of superposition is problematic for the "casual user". Technically a superposition is reserved for an ensemble of a single quantum system, i.e. it is a property of many repetitions of the same experiment. We like to imagine that, just like in classical physics, this ensemble can be replaced by many "independent" quanta at the same time, but that is just not so. The wave function of many quanta is the product of the wave functions of single quanta, which makes for an exponentially larger phase space. This is the very idea behind quantum computing, for instance.
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  85. Photons don't take any paths, at all. Photons are energy values. They are the work that a source performs on the electromagnetic field and the work that the electromagnetic field performs on the detector. That "work" does not have "a path" between source and detector. It's just distributed field energy.
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  86.  @michaelcohen5076  The path integral is not a description of a physical process but a quantization procedure. It takes a classical action and converts it into an infinite expression of nested integrals. These integrals are not solvable except in the case of free fields (which is boring, because those mean that nothing happens, at all, except for plain wave propagation). When we try to solve these integrals numerically, we run into an enormous number of problems. They do not converge, at all, unless we sample the classical field in a very special way, for instance (using a midpoint formula, I believe). Even then this quantization procedure predicts an enormous and unphysical ground state energy, which tells us that it way overcounts something. In other words: Feynman's path integrals are not the proper physical representation of these systems. They can be made to work for many predictions, but they certainly do not express the "natural" physical state of these fields. Even if they did... "all possible paths" are no more physical than the statement that "Santa Claus visits all living rooms in the world through the chimneys in one night" is a statement about physical motion. Quanta are a phenomenon of quantum-classical system boundaries. What nature is trying to tell us with this enormous complexity is that they are not a natural phenomenon "inside" of quantum systems.
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  87. The major trouble with many worlds is that nobody has ever seen a second world. :-)
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  88.  @sploofmcsterra4786  Take your time. It only took me like 30 years or so to "get it". ;-)
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  89. How does a talking donkey matter?
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  90. You can't run anything backwards from a detector. The definition of detector is that of an irreversible process.
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