The quiz for this video is here: quizwithit.com/start_thequiz/1737645316277x558406042661683200 Subscribed users can now revisit their questions with colour codes for what are wrong and right answers.
@@BishopStars Superdeterminism isn't even a theory. It's an idea. It's weird to say something is obvious that isn't fleshed out. If Sabine weren't so invested in the idea, she would call it unscientific. How do you test it? Sabine's answer is, eventually they'll notice it. At the moment, she is only saying "it's obvious", "it's provable by math". Isn't this a bunch of gobbledygook? I am not a physicist but per MWI, the world splits. One goes right, one goes left. You can observe either the beamsplitter or the photon, and by that, you'll find out in which universe you ended up with (or more precisely the you's are now entangled with). If we stay with Copenhagen, it is also debatable if the wavefunction collapse is actually instantaneous or not. It only needs to be consistent with causality. So, although I don't understand the topic, I am not terribly convinced that Superdeterminism is apparently necessarily the only correct solution.
Why wouldn't this interpretation result in a miniscule push against a mirror when photons bounce off? If they have momentum, then why not? Ahhh.. .nevermind.
Ah, New Scientist. I published a paper in The Lancet about an immunotoxin in an autoimmune disorder (many moons ago) and my colleagues and I were soon interviewed by the BBC World Service about the work. The New Scientist published a short article about our work possibly after a journalist had listened to the broadcast - it got our names wrong, what we did wrong, what it meant wrong.
I have the same problem on a lower level. Watching the news with a subject I know something about and they make a complete hash of it, what am I meant to think about the stories I know nothing about?
My comparison of psychology vs compsci articles always make we wish compsci had that level of quality in their articles ... but then again, I didn't study to become an engineer, just... a computer scientist (?)... so maybe in computer engineering there is more science and less coder high-school...
I've always wondered this, whenever people describe these experiments they always include things like beam splitters, detectors, mirrors etc... and I always think like doesn't that device do something, have some effect? Like how do you physically 'detect' a photon passing through, you must interact with it to accomplish that.
Yep. In the macroscopic world, observations (e.g. photons going from one object to the other) make object and measurement apparatus a rather loosely coupled system (so much as we get the impression we're "external observers, out of this world"). As quantum particles are tiny, observable and observation tool meet at the same scale with no loose connector in between. So they are, at least for a little bit, a rather tightly coupled system and we measure an interaction.
It is an interesting question, though, and may contribute to the solution of the measurement problem. If it would be possible to measure the movement of the beam-splitter, then it would be possible to force the wave function of the photon out of superposition by doing that measurement. The measurement problem then becomes: how large a movement is measurable?
@@SabineHossenfelder the thing that bothers me regarding the claim for the multiverse and for the creator/god thesis is that while they cannot be proven (at least for now) they cannot be ignored either. There is a self-evident truth: one or the other must be true or it makes no sense for the universe to exist precisely the way it is (following a particular and precise set of laws). For any other reason that can be conceived except these two it would be so improbable for the universe to exist exactly as is that it is safe to assume it is actually impossible to exist. These two, while mutually exclusive( ...or :) maybe in a superposition ), are the only conceivable ones that provide a non-negligible probability for the universe to exist (as is); An argument somewhat similar to "I think therefore I am", philosophical in nature of course but important to science because the purpose of science is to solve everything that is eventually. While proving the creator theory might be a long shot, the multiverse might be easier to tackle. It is not inconceivable for someone to come with a testable theory, same way Bell came with his inequality, do some experiment that has an effect in another universe that gives a testable feedback in ours...
Thanks! Sabine thank you so much, this is my only subscription on UA-cam but you deserve it. You teach so much relevant information that I find intriguing, but the best part is you remain honestly weigh in and are able to make me understand what if a topic has all the evidence to be considered highly valid and this has helped me understand numerous topics and more important weaknesses in numerous topics. You are also very witty but once again I love your candor and willingness to break things down in a very clear and concise manner. I pray 2025 is a great year for you!
For those that rely on subtitles there's an error at 5:50 "probably by Bell's theorem" and "provably by Bell's theorem" are very different statements with a single letter change.
@@louievito5701 Depending on the creator either UA-cam's crappy AI, a hired transcriber, or the creator themselves. I don't know which applies to Sabine's videos. But I wasn't trying to be mean, typos happen. It's just that in this instance a small typo drastically changes the meaning.
I came to the same conclusion after reading the New Scientist article and reading the version of the paper on arXiv. One would hope any competent peer reviewer would demolish it thoroughly. It should never make it into a reputable journal as it stands.
We are in the age of Deception. But at least we have one well known truth bearer in physics who understands how to make us understand. Thank you, Sabine.🙂
@ I agree, but I'd say New Scientist was at fault for presenting the thesis in the paper somewhat uncritically. Maybe the journalist was desperate for a story. It's forty years since I studied Physics and I could spot the errors straight away. Quantum mechanics wasn't even my chosen area of research. Readers of New Scientist unfamiliar with quantum theory might not have spotted such things. Personally, I believe our consciousnesses exist in a multiverse of sorts, perhaps along the lines of Wolfram's hypergraphs. However, if unfalsifiable, such an idea seems likely to remain in the realm of metaphysics as does Everett's relative state formulation.
@@sumfatdude4824 She seems to be presenting a pretty straightforward demolition of the paper though -- is the discussion that other experts are having over the paper present online somewhere or do they just talk amongst themselves? I am really curious what the authors say about the point made here concerning conservation of momentum being preserved in each interaction, not just on average.
@@sumfatdude4824 I didn't say anything was scientifically rigorous, rather, I asked for pointers on where to find the more scientifically rigorous discussion you're alluding to on this paper.
This is the first time that, in a Sabine's video, I got a glimpse of the solution before she reveals it. I immediately saw that it was necessary to consider also the "push" that the splitter receives and makes the sum of the momentum acquired by the splitter and that of the electron after it passes through the splitter, coincide with the initial momentum of the electron. Yippee
We don't know if Hossenfelder will have Big hair or Neat hair until we watch the video, sometimes the hair will change state during the video. I think this might be related to Schrodinger's Barber.
Another potential issue with energy conservation in QM: According to many authors (e.g Landau and Peierls) the law of energy conservation can be verified only to an accuracy of h/dt (energy-time uncertainty principle). Which implies that energy measurements carried out on short periods of time are not reproducible. However this was demystified by Aharonov and Bohm where they explain that it's indeed possible to measure the exact energy of a particle in an arbitrary short time. So apart of decay particles with lifetime tau that have a resonance width (and hence an unknown energy), we can determine, via certain measurements, the exact energy of a particle. However I'm not sure you can determine if the energy of the whole system (apparatus + observed particle) is conserved because of the uncertainty principle. It's a bit confusing...
5:47 I do understand that Superdeterminism is inevitable due to Bell's Theorem. Why people seem to have a problem with accepting Superdeterminism, this I do not understand. 🤔 (Or do they misunderstand Bell's Theorem to begin with?)
It does seem concerning that they missed basic concepts, like the photons imparting momentum to the reflector. If they don't even get the basics, they probably shouldn't be working on higher level stuff.
Actually in the paper they didn't use this example, they used angular momentum. The problem with the example is that since it doesn't use positions, one can't see the problem with local conservation laws.
Hmmm… this suggests we could (in principle) measure the momentum of the splitter and determine the position of the particle without disturbing the particle.
Would detecting the momentum transferred into the beam splitter collapse the superposition? If yes, would it also mean that say in case of an amplitude splitting interferometer, any interference pattern would appear and disappear as you turned on and off the momentum detection apparatus(in case there's only a single photon travelling in the interferometer at any given time of course)? If no, then what kind of sense does it make to detect a superposition of momentum? How would that... look like?
New Scientist have never understood conservation of momentum. I stopped reading it when they declared a reactionless EM drive would change the world. The problem with trashy science magazines is they need someone like Sabine to call them out because no scientist wants to read them.
Sure, but how about this? Place a large vacuum pump facing outward on the front of an airplane. It will create low pressure there and the normal air pressure at the back of the plane will push it forward! (Oh wait. How does a vacuum pump work?)
Because there was zero evidence the device would work. The whole reactionless EM drive relys on a theoretical background where they torture the math on a theory we *know* to be incomplete (i.e. does not always match observations). There is no experimental evidence supporting that the theory is reasonable to use that way, much less for reactionless EM thrust. On the other hand, it contradicts general principles of other, better-supported physical theories. Basically, extraordinary claims require extraordinary evidence, and they barely have anything that can be called evidence. It's arguable if anything done should even deserve a passing mention, much less calling it an 'upcoming revolution'
@@krisrhodes5180 So might a perpetual motion machine, but you won't see them give it the time of day cause it's *obviously* ridiculous and not worth mentioning.
Thanks Sabine. Your professional perspective is always notable. > I have to ask "Why does the photon have to be in 2 places at once?" How have they ever proved that is in 2 places when you can only ever measure 1. No one has ever detected the photon between the splitter and the detector? If that was so then it would be measured and still only following a single path. Has anyone detected 2 separate photons simultaneously before it collapses to one? I find it confusing to say 50 went one way and 50 the other therefore they all went both ways. > For me all I could say is we don't know which path it took until after it is measured. I would say it is in neither position/path until it is measured.
Someone a few comments earlier claims a photograph shows a photon in two places at once. But, I don't know because, first I don't know all the arguments and it seems to be unsettled whether a photon is even a "particle" at all....but back to the photo of a single photon in two places simultaneously:. How would they know if it's the same particle, or another stray particle, or some sort of anamoly in the measurement because "observing" the particle sure counts as a measurement.
@@stevedriscoll2539 If you take a photo it is a measurement and it collapses to a single photon. So to the best of my knowledge you can't get a photo or measurement of a photon in 2 places simultaneously. It's a mathematical probability, but that doesn't mean that it's a physical reality. > We can calculate the chance of a 6 on a die, but know one knows for sure until "after' the die has been measured. Some may say that the 6 is in every position simultaneously while it's spinning (as it is said with a particle), but part of me wants to say it is in NO places until it lands or is measured :) It's a bit of a weird distinction (in every place simultaneously vs in no place simultaneously) and comes down to an object in motion (not at rest), so when in motion you can't know it's velocity and position at the same time (Uncertainty principle). But it is the problem with motion for all things, in that you can never actually know where an object is, so you can never actually know where an photon is until it gets absorbed into something (as a measurement). . So for me, the photon has no describable position and is in no place that can be known, or in no places simultaneously. . Just sounds like a mirror reflection of the wording, or turning it backward. It's only when you look at the universe and physics from a slightly different paradigm that it makes sense :) aka the universe is always in motion (a state of flux) and is never static. The moment you take a static measurement the true nature of the universe (motion) is broken and we are left with the impression of a weird universe that doesn't seam right and doesn't make sense. > Sorry for the long dribble :)
@axle.student very good. I like the last paragraph, especially, where you said the moment one takes a static measurent of the universe (that is in perpetual motion), we get an impression or picture that is weird and not quite right. Have you watched any videos from "Chris, the Brain"? I have only watched one "Photons are not real, we made them up" and found it very interesting. You have said as much in your comment above, and I feel persuaded by both of you (and the "old masters" of science) that essentially the photon is not real in the sense it is not like an electron. I think Plank or Einstein said it was just "quanta" (a discrete packet of light). Is it just something that emerges, as a point-like entity because we are observing it/measuring it with our crude instruments?
@ "I like the last paragraph, especially, where you said the moment one takes a static measurent of the universe (that is in perpetual motion), we get an impression or picture that is weird and not quite right." A recent comment by me: ua-cam.com/video/93EnBN0-X6s/v-deo.html&lc=UgwgcG3rwP_oqWuRpDF4AaABAg I fall short of using the term "perpetual", as there is for me possibilities where "motion" can stop (rare). But "a continuum" is another expression, as opposed to a static point in a line. We could in a way consider this line analogy like this. If we take a single point from the 2D line, we have effectively reduced that to a 1D point (we have lost the 2D properties of the line). When we measure (as a point or discrete value) motion, we destroy the property of "motion" and loose information about that property such as velocity. We can try and fool ourselves into a concept of motion by placing many static points in a line but it wont be a continuum or motion. It will just remain many "static" disconnected points in a row like a movie strip of static images. This later part is also the illusion of time that we create where time is something real that flows. > Nah haven't seen "Chris, the Brain", but have seen some videos come up in my feed. I typically try and work directly from the physics where I can (rather than videos), but video offer many perspectives to consider. > "I think Plank or Einstein said it was just "quanta" (a discrete packet of light). Is it just something that emerges, as a point-like entity because we are observing it/measuring it with our crude instruments?" Quanta or a quantity of or packet. aka a piece of a wave (particle). Wave particle duality is a bit of an oddity, it's the wave part that is more complex :) . I use radio wave frequency photons as it is easier to see in action in everyday life. A radio wave requires an antenna to absorb it and covert to a different energy form. Think of a vertical dipole antenna where a pole of aluminum at the top is positive, and the pole at the bottom is negative (ground). (Some antennas such as car radios use the vehicle as the bottom pole and a little rod sticking up for the top pole.) A little like when we drag a magnet back and forth along a peace of wire and create an electric charge, something similar happens with the antenna. The high side of the wave pushes electricity through the center of the antenna to the lower pole, and then the low part of the wave pushes it back toward the top pole. The wave has just converted to a point like representation, but where is the point? At the very center of the 2 poles. It's a kind of imaginary zero point. We typical y have to wires breaking that zero point where we collect the photon wave and convert it into a tiny pulse of voltage (another wave packet). The important part of the analogy is that very illusive zero point in the center of the antenna. It's an abstract zero mark (point) where all the energy passes through. . I don't conceptualize visible photons much differently. when the photon (visible) wave is collected on/into and object the energy created in the conversion is highest at that abstract zero point giving us what appears like a point like expression of the photon. . Photons travel as (and are naturally waves). it is only the energy conversion after the photon hits something that we see a point like representation, but it's no longer a photon (EM wave packet) by then :) > I am not a physicist and the above is just a simplified analogy, but I think it highlights the point (Pun) :P
Classical physics is inherently superdeterministic. When QM came onto the scene, stodgy old classical physicists objected: "There must be a way to make this superdeterministic". Except that the word "superdeterminism" hadn't been invented yet, even though the concept was a core assumption of classical physics. Then Bell proved that local realism is possible if and only if the universe is superdeterministic, but nobody realized that the people objecting to quantum weirdness had been assuming superdeterminism all along. The decoherence paradigm was developed to explain wavefunction collapse as a physical, thermodynamic process (I think with an underlying assumption of superdeterminism), but Copenhagenites and Many-Worlders routinely misinterpret it as some kind of many-worlds paradigm.
Classical physics is inherently deterministic. Not super-deterministic. These are two different concepts. Your argument seems to be implying that super-determinism and determinism are equivalent, and if it is why invent the word super-determinism when determinism already exist? With Bells theorem, the localism can happen if the newly created entangled particles know what the state of the detectors will be when they get to the detectors. Classical determinism can not explain this, so super-determinism was created. But without any explanation of how it works. Super-determinism is by magic, quantum particles know what is going to happen in the future.
@@yziib3578 The difference between classical determinism and superdeterminism in either the classical or quantum context is basically one of thermodynamics and metaphysics. Thermodynamics in that we generally only have statistical, rather than exact knowledge of the state of the universe at any given time, so we can't predict the configuration of detectors ahead of time to predict what measurements they'll make even if it is all predetermined, and metaphysics because the only deterministic scenario I can imagine where all measurements aren't predetermined in either classical or quantum physics is if scientists have souls that aren't part of the universe (and thus are inherently a non-local influence) and at least some measurements occur as the result of decisions scientists make that are affected by their souls. The general vibe I get is that most of the classical old-guard would have regarded the metaphysical angle as complete nonsense and all expected that the universe was fundamentally superdeterministic even if thermodynamic considerations made practical human prediction of what measurements will be made impossible.
Awesome, Sabine! As usual... 🙂. Sabine? Would you mind singing "Catching Light"? I really like that song! 🙂Since I've been watching you, I have grown to like that song even more. Not to say that it wasn't a ten all along, but I would love to see you sing that song these days. Not because we are getting closer to catching it (although we could be, and probably are), but because you have caused a lot more people to search for it.
The correct way to say it is "Everything Everywhere, Eventually." A variation of behaviour may not happen simultaneously, but rather sequentially over time, all possibilities may occur.
@ITS_STEINSGATE eventually a version of you will. Just not yet. Imagine incremental variations of a timeliness built like a spiral tower. The previous layer dictates the shape of the top but variations aggregate from imperceptible errors in the next layer. Theoretically if linear multiverse is deterministic it's like 3D printing a tower until it falls over and you build a new one with the old material.
@@krissnoe500 wow man. I'm going through a hard time and it's comforting to know that when I come back I'll be able to become something more than I could fathom right now.
@mal2ksc more like after rebuilding the ships of Theseus, realizing you have Two ships that are of incredible similarity vut the mast line is .02cm to far left of the rebuilt version and its got ash instead of beach wood inlay on rudder. But this ship is the data of your mind. There is only one true theseus based of the continuity of existing in a state of function. If you jumped to a new universe yours ceases to exist chronologically. And the parallel you is maybe .008% different from you (arbitrary percent choice ive done no math)
I subscribe to your channel for the quantum physics,keep them coming..I watched this one three times.I can only absorb a few discreet bundles at a time.
I always thought that in quantum mechanics, conservation laws apply to average values. If they truly hold for every single event, I find it hard to understand how the Mach-Zehnder interferometer would work. Wouldn’t the interaction with the mirrors destroy the interference pattern? After all, each part of the photon’s wavefunction is now in a superposition with the moving mirrors. Furthermore-still considering the Mach-Zehnder setup-wouldn’t the action of the first beam splitter alone be enough to reduce the interference effect? Since, in principle, one could measure its momentum, how is the interference preserved? Is there a good book where i can read more about it?
Yes, this is a very good question. The reason that the interaction with the beam splitter and/or mirror doesn't destroy the superposition is that you can't measure it and in fact don't measure it. You can imagine the mirror and/or splitter to be so small that they are another particle and the interaction causes a measurable change. If you then measure the splitter-particle, the superposition will collapse.
@@SabineHossenfelder Well, that may be experimentally true, but according to quantum mechanics, these two states-whether measurable or not-are still orthogonal in Hilbert space, right? Is there some rule stating that if there is no physical process in the universe that could distinguish what happens with the mirror, then effectively nothing happens to the mirror? If that’s the case, then in principle we could downsize the mirrors and test the limit of the universe’s sensitivity to momentum changes. We could argue that once the interference pattern starts to weaken, there must be some process-whether or not we know what it is-that allows us to distinguish the direction in which the mirror is moving. God, I hate quantum mechanics. Now that I think about quasi-phase matching in SPDC I feel like I don’t understand anything at all...
Only averages of observed values are conserved by the most basic theory. This is because the conserved quantity is the observable itself not the measured value. Which is what every graduate with a bachelor's degree should know.
Consider a single photon fired at a beam splitter. What Sabina means is that the photon only interact with a small nano-scale portion of the macro-scale beam splitter that you can see with your eyes. While that's technically false (since any small momentum change would propagate), the relevant thing is that the information about any momentum changes in the beam splitter that's caused by interaction with the photon is lost at the macro-scale scale, with all the background noises in whatever actual setup you have. Even if the momentum of the macro-scale beam splitter is very precisely measured, its correlation with interactions with the photon is extremely low. This is in contrast with the photon's interaction with a detector, where the photon's signal is intentionally amplified, so that its presence is correlated with a macro-scaled event (such as an electric current) that we can measure. If you then suggest to measure momentum changes in the beam splitter at nano-scale portions, then you are turning the beam splitter into a detector. This is similar to measuring which slit a particle passes through in a double-slit experiment.
Sabine, thanks for this thought provoking video. Alas, there was one statement that I didn't understand. At 1:57 into the video you say that when taking measurements of either of the superposition locations, momentum can't be conserved. But from your explanation of momentum, up to that point in the video, it seems to me that indeed each measurement shows momentum to be equal to the initial momentum of the photon and thus is conserved. (One arrow in, one arrow out). Oh and another question it raised is how a single photon, being a quanta of energy could be split in the first place. Please, please explain. Many thanks
Hmm, interesting by the way. I've never thought about this before. If the beam splitter is in a superposition and it is entangled with a photon, then the state of the photon is mixed, shouldn't it decohere and shouldn't we lose the ability to measure quantum effects with it in isolation without taking into account the position of the beam splitter?
Sabine the best presentation so far in every aspect. In support to your sponsor it is enough to say one word Brilliant ! Glad you managed not to scream which would be still appropriate. But no one who should listens. No one who should looked into his telescope of Galileo to see Jupiter's moons orbiting. The world is always perfect as it is. No one listens to me saying that we could demonstrate absolute motion. I say you are not ready for that yet but your kids will love it MarthyMc Fly
If the photon on the left has been sent off in a new direction, and you suppose that the beam splitter moved to conserve momentum in the system, does that mean that momentum was imported to the beam splitter? If so, is the momentum of the photon lessened? If the momentum of the left-most photon is not lessened, where does the energy come from the move the beam splitter?
I have a hypothesis that there is only one Olive Garden, and the buildings we see are just portals to this Unitary Olive Garden. If you get lost coming back from the restroom, you may end up walking out in another city. I'm trying to convince them to change their slogan to "When you're here, you're simultaneously everywhere".
This idea is actually well established in the literature. You describe being lost in the "Franchise-space" and it can also be observed with Dunkin' Donut and others; sometimes different Franchise-spaces can be nested within each other, making things even more complicated and bland.
@@mal2ksc Yes, like that. And the theoretical math allows for some wild stuff. Think a Walmart with a Starbucks housing a McDonald Cafe in a corner handing out vouchers for Ikea where you can buy furniture to earn points towards your next Walmart purchase. The basic shape is called a circle jerk and, theoretically, you can add an infinite amount of steps, before you have to close the loop (assuming a consumer with indefinite purchasing power). You see, the voucher allows the connection of different physically nested Franchise-spaces even if they otherwise do not intersect.
I should add that it might be possible to construct suitable consumers by means of handing out indefinite credit scores. First experiments didn't go too well though...it seems infinite credit scores might negatively impact character and lead to spoiled-child-syndrom, gaming fraud and a propensity for weird hand gestures. Nevertheless, it's an interesting research area.
Can we have another course from you on Brilliant please? Or a continuation of the existing one maybe. There are so many misconceptions about physics out there, maybe a course to make them straight?
As soon as you suggested that momentum wouldn't be conserved, I said "but surely yes it would be conserved and the beam splitter would simply move accordingly? Since it is attached to the Earth in turn it would move the whole Earth (very slightly)." A few minutes later I found out that I was spot on. I'm not a physicist. I just have a high school level understanding of physics. The fact that I can see the problem and professional physicists can't, is genuinely concerning.
What makes it complicated is that, if you recombine the two halves, they will interfere with eachother - as if the photon moved in both directions - but if you observe the paths it only goes one way. Which means that the act of observing the beam will change the momentum of the mirror (or collapse the mirror's momentum wavefunction)
@@takanara7 This seems spot on. Momentum would not be conserved because during the mirroring, the system and loop by which the wave stays intact are in velocity, and the mass, which is in momentum, is in change. What the mirroring does is more than weigh the momentum, but rather it puts the conservation in loop, which if you think about it hard may make it unscienctific to physics. However, Because the mirroring of momentum opens the many-world hypothesis, the wave is reinterpreted to conservation. This is a hypothesis she put to theory from another scientist in a video between 2021-2023, how she shuffles through video content is not up to me. But I had a ring that day, and this one stuck. To make this easier to understand: The many-world hypothesis says there will be a change of perspective, which we can define no less than to a psychological nature and the need for acadamia behavior which physics can contribute to. Conservation of momentum says there will be a change of momenta, but the many-world hypothesis will continue. Some physcisits makes it a point that their own interpretation of the many-world hypothesis are different or inobstructable from the public. Inobstructable is a good precedence, but they can't fend for it. It's the many-world hypothesis. Why the systems and loops to momentum will be inobstrctable elsewhere, that's the conservation of momentum. Maybe you read them, and I'm telling you they are the same wave. It's just that there isn't a change of function. Get it? We're moving in both direction. Feel free to observe some more. Momentum: The "product" "product" "product" (wave) of an object. This object is the "change" "change" of mass and velocity conserved of the object. The object is in "momentum." As soon as you grasp, NEVER SEE IN PHYSICS, the product, you'll have the content definition of this short comment history. Well that was Sabine's lunch. I'll have to go find something else.
Was the laser aligned east or west during the experiment? What was Earth's rotational speed that day, considering earthquake-induced changes? What was its orbital velocity that year? In which direction was the solar system moving relative to the CMB? How does quantum measurement affect laser-beam splitter and COM dynamics?
I never understood the need to assume in quantum mechanics that superposition means something is in BOTH locales at once. It's only the probability that it's in one or the other, and once measured you now KNOW which it was. Momentum is conserved because if you tried to measure the momentum of the beam splitter you cause the probability field to collapse. There is never a time when the particle is "jumping" because the very act of trying to measure the indeterminant phase causes the photons position and momentum to be known.
It's can't be that the particle is in a definite position that is just unknown until it is measured though. In the double slit experiment, you get the interference pattern even when you shoot one electron at a time. That means each individual electron is going through both slits and interfering with itself.
That's not quite right though, it would be easy if it were the case. Superposition is real. That's the whole basis of the wave property of the quantum. A particle really does lose it's identity and spreads out into fuzzy uncertainty when it is left to it's own devices. If your theory about it simply being a probability was true then there would be no such thing as an interference pattern in the double slit experiment for instance. For the nail in the coffin you can look up the recent published papers were scientists have taken literal photos of superposition with a single particle seen to exist in two places at once.
It’s because when you split the wave function in, say, two parts, you can have situations where the two wave functions interfere with each other. That, is measurable! It’s a very, very subtle effect! Even physicists, including myself, sometimes forget that part and derive incorrect results. This occurs because there is no corresponding effect like it in classical physics. Someday educators will figure out a better way to teach physics. In other words, students often get taught classical physics for 1 or more years. Then they try to learn quantum mechanics.
Bells Inequality can be violated using hidden variables, if you do what every practical Bell test does: Throw away single detections. Throwing away single detections is an exchange of information between the two detectors, that causes the discrepancy.
The thing I don’t get about the many worlds interpretation is there are 10^78ish atoms in the universe, so every Planck second there needs to be an observation. The superposition of all those particles needs to spawn new universes, and the next Planck second it repeats. The amount of new worlds blows up instantly. Where does the energy come from when the worlds “split”?
If you calculate the energy in the entire multiverse, you have to weigh it by the probability of each multiverse existing. It is conserved as much or as little as it is always conserved in quantum physics. Not so surprisingly because it is, up to interpretation, the same theory!
@@SabineHossenfelder sabine what ur thought about jacob barandes formulation of quantum theory? i have come across it, he seem confident about it but as outsider then no way for me to judge its validity or usefulness.
I have a physics theory where leprechauns swim in cauldrons of gold coins at the end of rainbows. This is totally physical and definitely means something in the real world and isn’t just me being bored with an imagination. I dare say, it id the simplest explanation of all.
It's been quite a while since I studied Quantum Mechanics, but as I recall that's like the Young's experiment, right? The beam splitter acts like the wall with the two holes. If I recall correctly, it had a screen behind the wall with the two holes. If we'd only send a stream of particles through the wall, the beam would present a interference pattern, but if we'd attempt to measure through which hole the particles would pass, we'd have to interact with those particles via a photon for instance, as now we'd know the hole where the particle passed, the interference pattern would disappear and we'd get two gaussian distributions with the peaks aligned with the holes. Yet, the act of measuring the path of the particles would destroy their initial state because the photon used to measure their path would change the energy/momentum slightly. Yet, the wavelength of the photons would have to be shorter than the distance between the holes, or it would not be able to measure the path and the particles would present a interference pattern again. If I also recall correctly, if we'd send single particles, as the number of test particles increase the patterns start to show. This experiment seems the same, right?
Firstly, the "multiverse" is abstracted throughout many papers in modern physics. Just a few weeks ago I had to tell an author his paper was nonsense because it was written in the "multiverse" nomenclature. I think it may have even been on this channel. He responded by telling me that just because a paper was written in such a manner didn't mean that the paper indicated that the "multiverse" theory was correct. I was like... Secondly, the descriptions of superposition through the beam splitter isn't really making sense to me. You have to break regions of space, into phase space between an emitter and an absorber. The photon is actually absorbed by the splitters electro magnetic phase space. The concept of the photon particle doesn't actually exist. Its just a field of phase space that holds the superposition of the absorber within that phase space. If the particle is absorbed by the splitter, it creates a new phase space depending on the electro magnetic field surrounding it. I hope that makes sense to you. It new physics basically.
That just sounds right, and even if it wasn't, at minimum, how does one know that the splitter isn't acting as a pure detector...which it is isn't it, according to what you are saying?
@@stevedriscoll2539 Yes, the photon is absorbed by the splitters refractive index causing the splitter to gain in voltage before the photoelectric effect and re-emission. So yes, it could be considered a "detector"
@@Shadow_B4nned "phase space" I don't believe I recognize that nomenclature. Is that the new physics you are talking about or would I have read that in other books by physicists such as Max Born, or Richard Feynman? (Oh, to get old😏) Anyway that just sounds right how your are describing the action through the splitter
@@stevedriscoll2539 Phase space is a very old foundational concept for classical and quantum mechanics, and I'm not sure you can attribute it to any one person. It's not really "new". It's just new to the modern consensus. It basically gives a position and momentum to energy in space. It narrows down the wave function from any and all possibilities to that of only within the phase space. Using this method in quantum mechanics allows one to detail the superposition of photons within a phase space, between an emitter and absorber and not have the superposition of the photon abstractly described as existing in multiple phase spaces. As far as the action through the splitter, it's quantified as an emission/absorption by the refractive index of the splitter. Which also affects the velocity of propagation. But we don't really need to know all that.
Again: a fantastic video on a topic I just discovered. A question about the paper. Have the authors correctly demonstrated that energy and momentum are separately conserved for every Quantum measurement outcome?
If super determinism is reality, then don't worry: nothing you do or don't do will affect if people will accept it anyway. Truly, Neitzche's favorite theory.
What if the photon becomes entangled & entanglement creates a spatial fold/portal via higher spatial dimensions or, in other words, a warp bubble forms between the photon in superposition. By making observations, you are collapsing the entanglement fold/warp bubble & so they return to being in one place/direction, as opposed to both.
The more we LEARN about the very small and the very large, the less we KNOW about the very small and very large. Thankfully, learning more about “the in between” is what improves our existence. . .
Not with conservation laws, but I've always had a question regarding th the many worlds interpretation. If entropy increase is explained as a statistical mechanism, and there are a near infinite amount of other branching worlds. Wouldn't that imply that there's at least some where entropy is constantly decreasing?
I think you also can have this in just one universe in a sufficient amount of time. It´s what this thought experiment with the "Boltzmann-brains" is about.
What if we start with a superposition of lets say an electron with spin up and spin down? After the measurement we have changed the expectation value of the angular momentum by 90 degree, violating the associated conservation law. However, in many worlds it is conserved.
If a trees falls in the forest and nobody's around to hear it, does it make a noise? Just because we can't see beyond the observable universe does not mean there's nothing there to observe.
Quite right, this is the "Plato's cave" puzzle. The problem is that if you're stuck in the cave and have never been outside, how can you know there is an outside?
Sabine, why would there be a problem with the non-locality of the momentum change? Wouldn't the process of the photon going through the beam splitter just entangle the two, s.t. the combined state of photon + beam splitter is in a superposition. if you measure one part, you fix the other. In essence, measuring the momentum of the beam splitter afterwards should tell you where the photon went. Or am I missing something?
Actually, no, Bell had another caveat to his measurements which allows for local realism without resorting to the (conspiratorial) Superdeterminism. Look at Harvard's Jacob Barandes' recent work which also eliminates superposition/states.
The phrase "local realism" was introduced by sophists to confuse the discussion. "Realism" has no relevance to Bell's theorem, he never uses the term. There is not even a consistent usage in the literature as I can easily pull up multiple papers that define it differently. "Local realism" gives the impression that these two are incompatible so you must reject one or the other. Locality seems very well experimentally verified as Lorentz invariance always seems to hold up when put to the test, so the conclusion these sophists want you to draw is you should deny "realism" and thus devolve into idealism and mysticism. But the fact is Bell's theorem never had anything to do with realism at all, it had to do with local hidden variable theories, not local realism. There is no reason at all to equate realism with belief in hidden variables, as reality might simply not have hidden variables. You can see the writings of Carlo Rovelli on _weak realism_ or Jocelyn Benoist and Francois-Igor Pris on _contextual realism_ which posit an understanding of reality which is not dependent upon hidden variables, and thus is compatible with locality and Bell's theorem.
@ Lol because it makes complete sense that the polarized light from a quasar 5 billion light years away should directly correlate with the parameters "chosen" by the experimentalist, right...?
Curious: ... The part with the momentum transfer on the beam splitter ... The beam splitter itself being a macroscopic object that is in contact with the environment and the observer ... Now if it was hypothetically possible to measure the momentum transfer of a single photon on the beam splitter right away ... (pause) I just try to get ahead around the idea that the superposition of the photon should break down right away, as soon as I measure the momentum at the beam splitter, but if I don't do it, the superposition should persist. So basically I have the momentum of the photon and the beam splitter in and entangled state, right ? But the macroscopic beam splitter and its quantum state is basically not in any way shielded from interacting with the environment and me right away. Isn't there a problem with some common interpretations people voice all the time ? Or maybe this is exactly the remark about ''only superdetermism works'' ... I am not a physicist, I am just wondering, what interpretations of ''measurement'' and ''collapse of the wavefunction'' get immediately ruled out by this experiment, if any. Maybe it's just me being confused. 🤔
New Science should change its name to No Science for publishing an article showing such fundamental misunderstanding of the basic tenets of quantum physics.
Because this is a literature and physics main concern is the current event rather than the setting of social science, it's important for contributors to reveal what they think about theories around boundaries. This is very credulous with Albert Einstein pushing quantum physics to a space where colleagues can grasp the conservation of momentum, almost like the simulation game in 3 body problem.
Why would you think the beamsplitter is not also in a superposition of left and right, entangled with the photon? And the measurer, upon measuring, entangles itself with the photon? Being a quantum gravity question, I don't expect it to be compatible with general relativity.
An anthropological approach is required here. We have exactly the same brain as our hunter-gatherers ancestors. This brain was optimal for a single task that was connecting dots. The ability to connect between finding tiger shit and the actual presence of a tiger was vital for the group survival. Same thing for buffalo dung and the actual presence of a buffalo herd. Unfortunately, quantum physics is far remote from tracking a tiger from his shit. Therefore, many people will resort to a religious viewpoint like multiverse or a conscious universe etc. rather than to admit their brain is sub optimal for this task.
Isn't momentum a correlated state between the superpositions of the particle, as measured by the wave function? Analogous to how an electron doesn't have a separate charge for each of its possible positions around the nucleus. Similar to how states are correlated between entangled particles, so that there's no need for information transfer that defies locality?
So, does this mean that the mirror also goes into a quantum state of having been moved ever so slightly vs still in the same spot it started? And then once the photon is measured the superposition of both the photon and mirror settle out?
The single photon cannot go through the beam splitter without having an interaction. This is at least very clear for the instance of the photon going off at an angle.
I think The authors are still kind of on the right track. Everything we've measured in particle physics are just large averages. Because of the nature of particle physics, the only thing we CAN measure are averages. Then we base our math on those averages. There certainly could be all sorts of super deterministic nonsense happening below the level we're able to measure but we'll never know. The universe could very well be clockwork at its core, but if the gears are smaller than we could ever measure directly, we'd have no way of ever actually proving that.
I agree mostly, except your suggestion of the authors being on track. The authors wrote this paper on the basis of their (baffling) misunderstanding that momentum is merely conserved on average in our current theories (e.g. standard model) of quantum physics. I would consider them to possibly be on the right track if they instead state their doubt about our belief in the conservation of momentum and adequate justifications for said doubt.
@@welhtataum Statistics is considered like aviation in some academic disciplines. The momentum being conserved in average is because if a system is being looped, like a number system, which is a "system", then the product, which would be the loops, would appear as numbers that are average, but not within distribution to the total system. The reason likely why Sabine did not shot it down because in General Systems Theory, there is a possibility that systems tells us about other systems. Maybe you've played 6 degrees of Kevin Bacon on your Nintendo Swithc.
Wouldn't an easier way to look at this be that measuring the momentum change of the beam splitter would be effectively the same as measuring the location of the photon? The photon detectors become redundant because the momentum change (or not) already tells you which way the photon went!
Make the Universe Great Again. It's the best place in the Multiverse to invest in. Here you'll get the lowest taxes, the lowest regulatory burden, and most protection from competitors in other universes. Should you wish to import products into our universe rather than produce them here, well slap 100% tariffs on your goods.
I'm afraid I was lost at the delayed (or was it non-local?) conservation of momentum and super-determinism. And I'm absolutely terrified of Bell's Theorem. It doesn't seem like the wave collapse has to go back and interact with the splitter at superluminal speeds. What's worrisome is that if these are "credentialed" physicists and they don't know or understand what you appear to believe is fairly fundamental, then what use are credentials? Or why wasn't / isn't it covered in coursework? Knowing anything real about the world and outsourcing so much understanding to a trust relationship is extremely hard!
If the proton deflector doesn't move because the left/right deflection hasn't yet been observed (Accounts for both options), does it move when or after the position of the proton is observed?
I'm not getting it. Momentum is already always conserved in this experiment, in the form that the beam splitter takes up some of the photon momentum upon reflection, a well-known phenomenon also called radiation pressure. Can someone please illuminate me which part I'm missing here?
@Casey-Jones Thanks! I had stopped watching there because of how it was presented, and I thought this was so blatantly, obviously off. Should have known better, Sabine has her physics together :D
I have a problem in my mind I don't understand : if two electrons are in quantum states, how do they know they repulse each other by electromagnetic force ? They send each others a photon, isn't it ? So they interact with each other (they observe one another), so they can't be in a quantum superposition, can they ? So how can two electrons ever be in a quantum superposition ?
Super liquid helium 2, when a blob of it is shot at a piece of paper, at contact, the blob splits apart and then spreads over the surface of the paper, the thing is that NO FORCE is exerted on the paper, the momentum temporarily stops going forward. The liquid reaches the edge and goes around and back 5o centre of the paper on the other side where the blob reforms and then continues moving forward (momentum returns) and departs the paper as a reformed blob heading along the original trajectory! Issue is that temporarily momentum not conserved. A specially designed device could harness this strange property of superfluid to generate an overal lthrust or overall warping on space, Perhaps by interrupting the superfluid state at a point in the above steps, so that the effects on both sides of paper do not balance out duetothe superfluid state being altered and producing a none net zero effect. Perhaps the above is an explanation for how apparent gravity effects have been observed by super conducting spinning discs in magnetic fields, where tthe paper can be represented as the surface of the superconductor, on one side (inside the superconductor) the electrons flow as superfluid, and outside is non superfluid. Thus producing a imbalance in effect on gravity and thus produces gravity effects.
I always had a somewhat 'logical' argument against the Multiverse. And it's quite simple, likely pointing to my own lack of knowledge. It goes like this: The multiverse theory states that any decision branches off into multiple other 'universes'. So that in theory, anything that ever can, will happen in some universe out there. The problem is that if ANYTHING can happen then what if 'something' happens that disrupts the nature of the multiverse, sending shocks through all other multiverses, perhaps even shattering it? You could think of many, many scenarios where any kind of disaster could break down the multiverse. So if ANYTHING can happen in some universe anywhere, then that must by definition happen, or have happened. It didn't (so far, as we can observe).
Sabine, can quantum mechanics explain a falling drawer in the bathroom after a huge fight? My life has been put into chaos and I’ve been noticing many strange signs from the “universe” After that I got a peculiar one hour panic attack. The idea of panic has been recently more researched right?
@ thanks for the reply, maybe it’s a mix of quantum mechanics and chaos theory? I will eventually learn quantum mechanics on Sabine’s course of course. I’m a young industrial designer and made a bachelor degree in design about the Moon myself. Greeting from Poland 🇵🇱
@ Hi Marcel, yes one can´t rule out these things, therefore I´m enthused about Dr.Sabine´s work on superdeterminism, she´s one of a few scientists who think out of the box on this topic and haven´t given up to slove the measurement problem. Greetings from Cologne.
As I understand it Bell's theorem relies on a statistical method that proves there cannot be any "local hidden variables." Is there a good reference that explains this assumption for lay person? Thx
What happens when a particle in Superposition is viewed by 2 people at the same time can one sees it left and the other right? OH What a tangled particle we weave when first we practice to [Quantium] perceive.
Asking on behalf of a layman engineer. Could one measure the beam splitter to see if it was imparted momentum in the direction of the photon? That way you could 'measure' which direction the photon went without detecting the photon itself? Or would that also collapse the wave function?
Could someone help me understand what she was saying about the "violate measurement independence" and "superdeterminism" point? Apparently it's really important as Sabine was really emphatic about it, but i didn't get what it was at all? What is the very important key point these scientists seem to have gotten wrong?
I hate the many worlds theory personally. It seems to me that it violates the conservation of matter more than the conservation of momentum. Every time you fire a photon at a beam splitter an entire universe has to be created for both outcomes to happen. That's a lot of matter to just appear out of nowhere. And it has to be happening an infinite number of times every second, because it's not just that beam splitter experiment, it's every time something goes into super position. And it's not just all the super position events in one universe, but the super position events in an infinite number of universes. So if matter can't be created or destroyed, but it's being created at an infinitely exponential rate, that seems to be a problem. Then again, maybe the infinite number of universes layered on to each other is the actual source of dark matter. It's just us in a universe that is almost exactly the same as ours. And dark energy is just the pressure of infinite universes coming into being.
It just occurred to me that if you had a photon of high enough momentum to actually have a measurable effect on the momentum of the beam splitter (like for instance X-ray impinging on a micro-electromechanical system = MEMS cantilever), then the photon should end up not being in a superposition between having reflected or gone through.
How do you "measure" the photon? I've always found it odd that the wave function collapse happens when you observe which slit it goes through. How is it being observed?
I thought the force vector diagram was interesting. I couldn't help but think of it in terms of an individual particle. If the particle hits the beam splitter does it not impart information (in the form of momentum) before the quantum waveform collapses, (that is to say the particle is resolved either left or right)? It seems to me that this principle could be used in a similar way to the Quantum Erasure experiment.
In a thought experiment, you could place many of these reflectors next to each other. In each case, the particle has to make a decision: left or right. That means, there can be many outcomes of the experiment, but you only measure one, namely the outcome. Does that mean that all possible states exist at the same time? If there are many reflectors, that would create a near-infinite number of states, and thus a near infinite momentum. Of course near-infinite momentum doesn't exist, so the states don't exist at the same time, even though we only have one measurement.
The quiz for this video is here:
quizwithit.com/start_thequiz/1737645316277x558406042661683200
Subscribed users can now revisit their questions with colour codes for what are wrong and right answers.
I prefer the "out-of-this-world theory"😄thank you for the quiz.
Keep fighting the good fight. Superdeterminism is obvious to me, too, and I can't grasp why it's even debatable.
Sabine, you must do an episode on Chris The Brain's theories on youtube, he is so good!!!
@@BishopStars Superdeterminism isn't even a theory. It's an idea. It's weird to say something is obvious that isn't fleshed out. If Sabine weren't so invested in the idea, she would call it unscientific. How do you test it? Sabine's answer is, eventually they'll notice it. At the moment, she is only saying "it's obvious", "it's provable by math". Isn't this a bunch of gobbledygook? I am not a physicist but per MWI, the world splits. One goes right, one goes left. You can observe either the beamsplitter or the photon, and by that, you'll find out in which universe you ended up with (or more precisely the you's are now entangled with). If we stay with Copenhagen, it is also debatable if the wavefunction collapse is actually instantaneous or not. It only needs to be consistent with causality. So, although I don't understand the topic, I am not terribly convinced that Superdeterminism is apparently necessarily the only correct solution.
Why wouldn't this interpretation result in a miniscule push against a mirror when photons bounce off? If they have momentum, then why not?
Ahhh.. .nevermind.
Ah, New Scientist. I published a paper in The Lancet about an immunotoxin in an autoimmune disorder (many moons ago) and my colleagues and I were soon interviewed by the BBC World Service about the work. The New Scientist published a short article about our work possibly after a journalist had listened to the broadcast - it got our names wrong, what we did wrong, what it meant wrong.
Yeah, thats what journalists do.
My mother was on the radio the other day. And look and behold they pronounced our family name correct.
Correctness is NOT a goal of journalism. The SOLE goal of journalism is attention-getting.
@@jpt3640 how do you pronounce jpt3640 ?
New Scientist became a tabloid rag decades ago.
I have the same problem on a lower level.
Watching the news with a subject I know something about and they make a complete hash of it, what am I meant to think about the stories I know nothing about?
Every time I watch Sabine's physics content, I always thank myself for choosing engineering.
.. . or Software
My comparison of psychology vs compsci articles always make we wish compsci had that level of quality in their articles ... but then again, I didn't study to become an engineer, just... a computer scientist (?)... so maybe in computer engineering there is more science and less coder high-school...
Same but software for me.
But the you in the universe where you picked otherwise just curses fate.
totally understand that!
I've always wondered this, whenever people describe these experiments they always include things like beam splitters, detectors, mirrors etc... and I always think like doesn't that device do something, have some effect? Like how do you physically 'detect' a photon passing through, you must interact with it to accomplish that.
Exactly!
Yep. In the macroscopic world, observations (e.g. photons going from one object to the other) make object and measurement apparatus a rather loosely coupled system (so much as we get the impression we're "external observers, out of this world"). As quantum particles are tiny, observable and observation tool meet at the same scale with no loose connector in between. So they are, at least for a little bit, a rather tightly coupled system and we measure an interaction.
👍🏽
It is an interesting question, though, and may contribute to the solution of the measurement problem. If it would be possible to measure the movement of the beam-splitter, then it would be possible to force the wave function of the photon out of superposition by doing that measurement.
The measurement problem then becomes: how large a movement is measurable?
@@SabineHossenfelder the thing that bothers me regarding the claim for the multiverse and for the creator/god thesis is that while they cannot be proven (at least for now) they cannot be ignored either. There is a self-evident truth: one or the other must be true or it makes no sense for the universe to exist precisely the way it is (following a particular and precise set of laws). For any other reason that can be conceived except these two it would be so improbable for the universe to exist exactly as is that it is safe to assume it is actually impossible to exist. These two, while mutually exclusive( ...or :) maybe in a superposition ), are the only conceivable ones that provide a non-negligible probability for the universe to exist (as is); An argument somewhat similar to "I think therefore I am", philosophical in nature of course but important to science because the purpose of science is to solve everything that is eventually. While proving the creator theory might be a long shot, the multiverse might be easier to tackle. It is not inconceivable for someone to come with a testable theory, same way Bell came with his inequality, do some experiment that has an effect in another universe that gives a testable feedback in ours...
Thanks! Sabine thank you so much, this is my only subscription on UA-cam but you deserve it. You teach so much relevant information that I find intriguing, but the best part is you remain honestly weigh in and are able to make me understand what if a topic has all the evidence to be considered highly valid and this has helped me understand numerous topics and more important weaknesses in numerous topics. You are also very witty but once again I love your candor and willingness to break things down in a very clear and concise manner. I pray 2025 is a great year for you!
Thanks for subscribing brother, it keeps it free for people like me
thank you!
For those that rely on subtitles there's an error at 5:50 "probably by Bell's theorem" and "provably by Bell's theorem" are very different statements with a single letter change.
Even with Sabine's measured and immaculate diction, AI transcription isn't all it's cracked up to be!
Subtitles on youtube are laughably bad at the best of times. Who exactly is responsible for them?
@@louievito5701 Depending on the creator either UA-cam's crappy AI, a hired transcriber, or the creator themselves. I don't know which applies to Sabine's videos. But I wasn't trying to be mean, typos happen. It's just that in this instance a small typo drastically changes the meaning.
@@waynebowers4098 I knew I shouldn't have measured the subtitles.
Bill's Theorem?
I came to the same conclusion after reading the New Scientist article and reading the version of the paper on arXiv. One would hope any competent peer reviewer would demolish it thoroughly. It should never make it into a reputable journal as it stands.
We are in the age of Deception. But at least we have one well known truth bearer in physics who understands how to make us understand. Thank you, Sabine.🙂
@ I agree, but I'd say New Scientist was at fault for presenting the thesis in the paper somewhat uncritically. Maybe the journalist was desperate for a story. It's forty years since I studied Physics and I could spot the errors straight away. Quantum mechanics wasn't even my chosen area of research. Readers of New Scientist unfamiliar with quantum theory might not have spotted such things. Personally, I believe our consciousnesses exist in a multiverse of sorts, perhaps along the lines of Wolfram's hypergraphs. However, if unfalsifiable, such an idea seems likely to remain in the realm of metaphysics as does Everett's relative state formulation.
@@sumfatdude4824 She seems to be presenting a pretty straightforward demolition of the paper though -- is the discussion that other experts are having over the paper present online somewhere or do they just talk amongst themselves? I am really curious what the authors say about the point made here concerning conservation of momentum being preserved in each interaction, not just on average.
@@sumfatdude4824 I didn't say anything was scientifically rigorous, rather, I asked for pointers on where to find the more scientifically rigorous discussion you're alluding to on this paper.
This is the first time that, in a Sabine's video, I got a glimpse of the solution before she reveals it. I immediately saw that it was necessary to consider also the "push" that the splitter receives and makes the sum of the momentum acquired by the splitter and that of the electron after it passes through the splitter, coincide with the initial momentum of the electron. Yippee
Congrats
What electron?
We don't know if Hossenfelder will have Big hair or Neat hair until we watch the video, sometimes the hair will change state during the video. I think this might be related to Schrodinger's Barber.
Maybe the big/fuzzy hair is a superimposed state between cropped hair and a Mohican waiting to collapse one way or the other.
Anyhow, marvelous hair
It's an AI video, so why doesn't she get a Beehive Hairdoo and Saucy Tops? :P
Continuity errors in theoretical physics are a given.
I choose only to listen, not to watch. Therefore, her hair is both Big and Neat.
Thanks!
no, thank you! 😆
Fascinating! Thanks, Sabine! 😊
Stay safe there with your family! 🖖😊
Thanks, you too!
“Progresses one UA-cam video at a time” - lol - I love it. 😆
"science progresses one UA-cam video at a time"
That's what science came to?
That's sad
It doesn't matter in which field, the truth never stopped journalists from writing selling headlines
Another potential issue with energy conservation in QM: According to many authors (e.g Landau and Peierls) the law of energy conservation can be verified only to an accuracy of h/dt (energy-time uncertainty principle). Which implies that energy measurements carried out on short periods of time are not reproducible. However this was demystified by Aharonov and Bohm where they explain that it's indeed possible to measure the exact energy of a particle in an arbitrary short time. So apart of decay particles with lifetime tau that have a resonance width (and hence an unknown energy), we can determine, via certain measurements, the exact energy of a particle. However I'm not sure you can determine if the energy of the whole system (apparatus + observed particle) is conserved because of the uncertainty principle. It's a bit confusing...
"Wait that doesn't work at all!"
"It does, if you use that particle I have just invented." 😉
That paper's analysis sounds like something the high school science geeks would come up with in the school cafeteria.
5:47 I do understand that Superdeterminism is inevitable due to Bell's Theorem. Why people seem to have a problem with accepting Superdeterminism, this I do not understand. 🤔
(Or do they misunderstand Bell's Theorem to begin with?)
The illusion of libertarian free will is a powerful, emotionally overwhelming one. Apparently even for scientists...
It does seem concerning that they missed basic concepts, like the photons imparting momentum to the reflector. If they don't even get the basics, they probably shouldn't be working on higher level stuff.
Actually in the paper they didn't use this example, they used angular momentum. The problem with the example is that since it doesn't use positions, one can't see the problem with local conservation laws.
@@SabineHossenfelder - Thanks for the clarification.
Sounds like peer review should have caught this?
QM is a load of wank
I still don’t understand how a photon with 0 mass can impart momentum??
Hmmm… this suggests we could (in principle) measure the momentum of the splitter and determine the position of the particle without disturbing the particle.
Thanks for the video. Is there research in this area of superdeterminism? A video about that would be interesting 🤷🏽♂️
I believe she’s done a few already! They may be over a year old now but you could scroll through her page to check
Would detecting the momentum transferred into the beam splitter collapse the superposition?
If yes, would it also mean that say in case of an amplitude splitting interferometer, any interference pattern would appear and disappear as you turned on and off the momentum detection apparatus(in case there's only a single photon travelling in the interferometer at any given time of course)?
If no, then what kind of sense does it make to detect a superposition of momentum? How would that... look like?
New Scientist have never understood conservation of momentum. I stopped reading it when they declared a reactionless EM drive would change the world. The problem with trashy science magazines is they need someone like Sabine to call them out because no scientist wants to read them.
Sure, but how about this? Place a large vacuum pump facing outward on the front of an airplane. It will create low pressure there and the normal air pressure at the back of the plane will push it forward! (Oh wait. How does a vacuum pump work?)
Why wouldn't it change the world?
Because there was zero evidence the device would work.
The whole reactionless EM drive relys on a theoretical background where they torture the math on a theory we *know* to be incomplete (i.e. does not always match observations).
There is no experimental evidence supporting that the theory is reasonable to use that way, much less for reactionless EM thrust.
On the other hand, it contradicts general principles of other, better-supported physical theories.
Basically, extraordinary claims require extraordinary evidence, and they barely have anything that can be called evidence. It's arguable if anything done should even deserve a passing mention, much less calling it an 'upcoming revolution'
@@bluerendar2194 I understood the claim to be that EM "would" change the world, i.e., if it works.
@@krisrhodes5180 So might a perpetual motion machine, but you won't see them give it the time of day cause it's *obviously* ridiculous and not worth mentioning.
Thanks Sabine. Your professional perspective is always notable.
>
I have to ask "Why does the photon have to be in 2 places at once?"
How have they ever proved that is in 2 places when you can only ever measure 1. No one has ever detected the photon between the splitter and the detector? If that was so then it would be measured and still only following a single path.
Has anyone detected 2 separate photons simultaneously before it collapses to one?
I find it confusing to say 50 went one way and 50 the other therefore they all went both ways.
>
For me all I could say is we don't know which path it took until after it is measured. I would say it is in neither position/path until it is measured.
Someone a few comments earlier claims a photograph shows a photon in two places at once. But, I don't know because, first I don't know all the arguments and it seems to be unsettled whether a photon is even a "particle" at all....but back to the photo of a single photon in two places simultaneously:. How would they know if it's the same particle, or another stray particle, or some sort of anamoly in the measurement because "observing" the particle sure counts as a measurement.
@@stevedriscoll2539 If you take a photo it is a measurement and it collapses to a single photon. So to the best of my knowledge you can't get a photo or measurement of a photon in 2 places simultaneously.
It's a mathematical probability, but that doesn't mean that it's a physical reality.
>
We can calculate the chance of a 6 on a die, but know one knows for sure until "after' the die has been measured.
Some may say that the 6 is in every position simultaneously while it's spinning (as it is said with a particle), but part of me wants to say it is in NO places until it lands or is measured :)
It's a bit of a weird distinction (in every place simultaneously vs in no place simultaneously) and comes down to an object in motion (not at rest), so when in motion you can't know it's velocity and position at the same time (Uncertainty principle).
But it is the problem with motion for all things, in that you can never actually know where an object is, so you can never actually know where an photon is until it gets absorbed into something (as a measurement).
.
So for me, the photon has no describable position and is in no place that can be known, or in no places simultaneously.
.
Just sounds like a mirror reflection of the wording, or turning it backward. It's only when you look at the universe and physics from a slightly different paradigm that it makes sense :)
aka the universe is always in motion (a state of flux) and is never static. The moment you take a static measurement the true nature of the universe (motion) is broken and we are left with the impression of a weird universe that doesn't seam right and doesn't make sense.
>
Sorry for the long dribble :)
@axle.student very good. I like the last paragraph, especially, where you said the moment one takes a static measurent of the universe (that is in perpetual motion), we get an impression or picture that is weird and not quite right. Have you watched any videos from "Chris, the Brain"? I have only watched one "Photons are not real, we made them up" and found it very interesting. You have said as much in your comment above, and I feel persuaded by both of you (and the "old masters" of science) that essentially the photon is not real in the sense it is not like an electron. I think Plank or Einstein said it was just "quanta" (a discrete packet of light). Is it just something that emerges, as a point-like entity because we are observing it/measuring it with our crude instruments?
@ "I like the last paragraph, especially, where you said the moment one takes a static measurent of the universe (that is in perpetual motion), we get an impression or picture that is weird and not quite right."
A recent comment by me: ua-cam.com/video/93EnBN0-X6s/v-deo.html&lc=UgwgcG3rwP_oqWuRpDF4AaABAg
I fall short of using the term "perpetual", as there is for me possibilities where "motion" can stop (rare). But "a continuum" is another expression, as opposed to a static point in a line.
We could in a way consider this line analogy like this. If we take a single point from the 2D line, we have effectively reduced that to a 1D point (we have lost the 2D properties of the line).
When we measure (as a point or discrete value) motion, we destroy the property of "motion" and loose information about that property such as velocity.
We can try and fool ourselves into a concept of motion by placing many static points in a line but it wont be a continuum or motion. It will just remain many "static" disconnected points in a row like a movie strip of static images.
This later part is also the illusion of time that we create where time is something real that flows.
>
Nah haven't seen "Chris, the Brain", but have seen some videos come up in my feed. I typically try and work directly from the physics where I can (rather than videos), but video offer many perspectives to consider.
>
"I think Plank or Einstein said it was just "quanta" (a discrete packet of light). Is it just something that emerges, as a point-like entity because we are observing it/measuring it with our crude instruments?"
Quanta or a quantity of or packet. aka a piece of a wave (particle).
Wave particle duality is a bit of an oddity, it's the wave part that is more complex :)
.
I use radio wave frequency photons as it is easier to see in action in everyday life.
A radio wave requires an antenna to absorb it and covert to a different energy form. Think of a vertical dipole antenna where a pole of aluminum at the top is positive, and the pole at the bottom is negative (ground). (Some antennas such as car radios use the vehicle as the bottom pole and a little rod sticking up for the top pole.)
A little like when we drag a magnet back and forth along a peace of wire and create an electric charge, something similar happens with the antenna. The high side of the wave pushes electricity through the center of the antenna to the lower pole, and then the low part of the wave pushes it back toward the top pole. The wave has just converted to a point like representation, but where is the point? At the very center of the 2 poles. It's a kind of imaginary zero point. We typical y have to wires breaking that zero point where we collect the photon wave and convert it into a tiny pulse of voltage (another wave packet).
The important part of the analogy is that very illusive zero point in the center of the antenna. It's an abstract zero mark (point) where all the energy passes through.
.
I don't conceptualize visible photons much differently. when the photon (visible) wave is collected on/into and object the energy created in the conversion is highest at that abstract zero point giving us what appears like a point like expression of the photon.
.
Photons travel as (and are naturally waves). it is only the energy conversion after the photon hits something that we see a point like representation, but it's no longer a photon (EM wave packet) by then :)
>
I am not a physicist and the above is just a simplified analogy, but I think it highlights the point (Pun) :P
Classical physics is inherently superdeterministic.
When QM came onto the scene, stodgy old classical physicists objected: "There must be a way to make this superdeterministic". Except that the word "superdeterminism" hadn't been invented yet, even though the concept was a core assumption of classical physics.
Then Bell proved that local realism is possible if and only if the universe is superdeterministic, but nobody realized that the people objecting to quantum weirdness had been assuming superdeterminism all along.
The decoherence paradigm was developed to explain wavefunction collapse as a physical, thermodynamic process (I think with an underlying assumption of superdeterminism), but Copenhagenites and Many-Worlders routinely misinterpret it as some kind of many-worlds paradigm.
I don’t understand anything you said, but it sounds good and worthy of a thumbs up from me.
Classical physics is inherently deterministic. Not super-deterministic. These are two different concepts. Your argument seems to be implying that super-determinism and determinism are equivalent, and if it is why invent the word super-determinism when determinism already exist?
With Bells theorem, the localism can happen if the newly created entangled particles know what the state of the detectors will be when they get to the detectors. Classical determinism can not explain this, so super-determinism was created. But without any explanation of how it works. Super-determinism is by magic, quantum particles know what is going to happen in the future.
@@yziib3578 The difference between classical determinism and superdeterminism in either the classical or quantum context is basically one of thermodynamics and metaphysics. Thermodynamics in that we generally only have statistical, rather than exact knowledge of the state of the universe at any given time, so we can't predict the configuration of detectors ahead of time to predict what measurements they'll make even if it is all predetermined, and metaphysics because the only deterministic scenario I can imagine where all measurements aren't predetermined in either classical or quantum physics is if scientists have souls that aren't part of the universe (and thus are inherently a non-local influence) and at least some measurements occur as the result of decisions scientists make that are affected by their souls. The general vibe I get is that most of the classical old-guard would have regarded the metaphysical angle as complete nonsense and all expected that the universe was fundamentally superdeterministic even if thermodynamic considerations made practical human prediction of what measurements will be made impossible.
That Copenhagenites and Many-Worlders exists is a measurent of how desperate Quantists are.
Awesome, Sabine! As usual... 🙂. Sabine? Would you mind singing "Catching Light"? I really like that song! 🙂Since I've been watching you, I have grown to like that song even more. Not to say that it wasn't a ten all along, but I would love to see you sing that song these days. Not because we are getting closer to catching it (although we could be, and probably are), but because you have caused a lot more people to search for it.
thank you for talking common sense and logic rather then pure non logic!
It's so helpful to have discussions of quantum mechanics that don't elide false or misunderstood assumptions.
The correct way to say it is "Everything Everywhere, Eventually." A variation of behaviour may not happen simultaneously, but rather sequentially over time, all possibilities may occur.
so does this mean I could die and since that'd be the case I could open my eyes as the same me in a different time?
@ITS_STEINSGATE eventually a version of you will. Just not yet. Imagine incremental variations of a timeliness built like a spiral tower. The previous layer dictates the shape of the top but variations aggregate from imperceptible errors in the next layer. Theoretically if linear multiverse is deterministic it's like 3D printing a tower until it falls over and you build a new one with the old material.
All possibilities may occur. But only one will.
@@krissnoe500 wow man. I'm going through a hard time and it's comforting to know that when I come back I'll be able to become something more than I could fathom right now.
@mal2ksc more like after rebuilding the ships of Theseus, realizing you have Two ships that are of incredible similarity vut the mast line is .02cm to far left of the rebuilt version and its got ash instead of beach wood inlay on rudder. But this ship is the data of your mind. There is only one true theseus based of the continuity of existing in a state of function. If you jumped to a new universe yours ceases to exist chronologically. And the parallel you is maybe .008% different from you (arbitrary percent choice ive done no math)
I subscribe to your channel for the quantum physics,keep them coming..I watched this one three times.I can only absorb a few discreet bundles at a time.
I always thought that in quantum mechanics, conservation laws apply to average values. If they truly hold for every single event, I find it hard to understand how the Mach-Zehnder interferometer would work. Wouldn’t the interaction with the mirrors destroy the interference pattern? After all, each part of the photon’s wavefunction is now in a superposition with the moving mirrors.
Furthermore-still considering the Mach-Zehnder setup-wouldn’t the action of the first beam splitter alone be enough to reduce the interference effect? Since, in principle, one could measure its momentum, how is the interference preserved?
Is there a good book where i can read more about it?
Yes, this is a very good question. The reason that the interaction with the beam splitter and/or mirror doesn't destroy the superposition is that you can't measure it and in fact don't measure it. You can imagine the mirror and/or splitter to be so small that they are another particle and the interaction causes a measurable change. If you then measure the splitter-particle, the superposition will collapse.
@@SabineHossenfelder Well, that may be experimentally true, but according to quantum mechanics, these two states-whether measurable or not-are still orthogonal in Hilbert space, right?
Is there some rule stating that if there is no physical process in the universe that could distinguish what happens with the mirror, then effectively nothing happens to the mirror? If that’s the case, then in principle we could downsize the mirrors and test the limit of the universe’s sensitivity to momentum changes. We could argue that once the interference pattern starts to weaken, there must be some process-whether or not we know what it is-that allows us to distinguish the direction in which the mirror is moving.
God, I hate quantum mechanics. Now that I think about quasi-phase matching in SPDC I feel like I don’t understand anything at all...
@ Sorry to spam you, but now that I think about it: isn't what you just wrote in a direct contradiction with your argument in the video?
Only averages of observed values are conserved by the most basic theory. This is because the conserved quantity is the observable itself not the measured value. Which is what every graduate with a bachelor's degree should know.
Consider a single photon fired at a beam splitter. What Sabina means is that the photon only interact with a small nano-scale portion of the macro-scale beam splitter that you can see with your eyes. While that's technically false (since any small momentum change would propagate), the relevant thing is that the information about any momentum changes in the beam splitter that's caused by interaction with the photon is lost at the macro-scale scale, with all the background noises in whatever actual setup you have. Even if the momentum of the macro-scale beam splitter is very precisely measured, its correlation with interactions with the photon is extremely low. This is in contrast with the photon's interaction with a detector, where the photon's signal is intentionally amplified, so that its presence is correlated with a macro-scaled event (such as an electric current) that we can measure.
If you then suggest to measure momentum changes in the beam splitter at nano-scale portions, then you are turning the beam splitter into a detector. This is similar to measuring which slit a particle passes through in a double-slit experiment.
Sabine, thanks for this thought provoking video. Alas, there was one statement that I didn't understand. At 1:57 into the video you say that when taking measurements of either of the superposition locations, momentum can't be conserved. But from your explanation of momentum, up to that point in the video, it seems to me that indeed each measurement shows momentum to be equal to the initial momentum of the photon and thus is conserved. (One arrow in, one arrow out). Oh and another question it raised is how a single photon, being a quanta of energy could be split in the first place. Please, please explain. Many thanks
Thanks for this. My headache just got worse.
Sorry! 😂
I'm so glad you addressed (3:38) my disagreement! That saved me some valuable keystrokes :D
It’s a problem when you see a paper in an important magazine falls with basic quantum mechanics.
thank you for the sharing my friend
Thank you for the video.
Hmm, interesting by the way. I've never thought about this before. If the beam splitter is in a superposition and it is entangled with a photon, then the state of the photon is mixed, shouldn't it decohere and shouldn't we lose the ability to measure quantum effects with it in isolation without taking into account the position of the beam splitter?
So in summary, they disqualified an ascientific hypothesis with an unscientific methodology? I´m waiting for the superdeterministic breakthrough.
@ and to you
Sabine the best presentation so far in every aspect.
In support to your sponsor it is enough to say one word
Brilliant !
Glad you managed not to scream which would be still appropriate. But no one who should listens. No one who should looked into his telescope of Galileo to see Jupiter's moons orbiting. The world is always perfect as it is. No one listens to me saying that we could demonstrate absolute motion. I say you are not ready for that yet but your kids will love it
MarthyMc Fly
Thank you
If the photon on the left has been sent off in a new direction, and you suppose that the beam splitter moved to conserve momentum in the system, does that mean that momentum was imported to the beam splitter? If so, is the momentum of the photon lessened? If the momentum of the left-most photon is not lessened, where does the energy come from the move the beam splitter?
Yes, the photon energy is lessened by the "recoil energy.' This has been observed in atomic physics experiments. Good question.
@@squeakeththewheel Thank you.
I have a hypothesis that there is only one Olive Garden, and the buildings we see are just portals to this Unitary Olive Garden. If you get lost coming back from the restroom, you may end up walking out in another city. I'm trying to convince them to change their slogan to "When you're here, you're simultaneously everywhere".
This idea is actually well established in the literature. You describe being lost in the "Franchise-space" and it can also be observed with Dunkin' Donut and others; sometimes different Franchise-spaces can be nested within each other, making things even more complicated and bland.
@@jorgwei8590 Like when we used to have bookstores that all looked alike, and had a Starbucks inside?
@@mal2ksc Yes, like that. And the theoretical math allows for some wild stuff. Think a Walmart with a Starbucks housing a McDonald Cafe in a corner handing out vouchers for Ikea where you can buy furniture to earn points towards your next Walmart purchase. The basic shape is called a circle jerk and, theoretically, you can add an infinite amount of steps, before you have to close the loop (assuming a consumer with indefinite purchasing power). You see, the voucher allows the connection of different physically nested Franchise-spaces even if they otherwise do not intersect.
I should add that it might be possible to construct suitable consumers by means of handing out indefinite credit scores. First experiments didn't go too well though...it seems infinite credit scores might negatively impact character and lead to spoiled-child-syndrom, gaming fraud and a propensity for weird hand gestures. Nevertheless, it's an interesting research area.
Can we have another course from you on Brilliant please? Or a continuation of the existing one maybe. There are so many misconceptions about physics out there, maybe a course to make them straight?
As soon as you suggested that momentum wouldn't be conserved, I said "but surely yes it would be conserved and the beam splitter would simply move accordingly? Since it is attached to the Earth in turn it would move the whole Earth (very slightly)."
A few minutes later I found out that I was spot on.
I'm not a physicist. I just have a high school level understanding of physics. The fact that I can see the problem and professional physicists can't, is genuinely concerning.
What makes it complicated is that, if you recombine the two halves, they will interfere with eachother - as if the photon moved in both directions - but if you observe the paths it only goes one way. Which means that the act of observing the beam will change the momentum of the mirror (or collapse the mirror's momentum wavefunction)
@@takanara7 This seems spot on. Momentum would not be conserved because during the mirroring, the system and loop by which the wave stays intact are in velocity, and the mass, which is in momentum, is in change. What the mirroring does is more than weigh the momentum, but rather it puts the conservation in loop, which if you think about it hard may make it unscienctific to physics. However, Because the mirroring of momentum opens the many-world hypothesis, the wave is reinterpreted to conservation. This is a hypothesis she put to theory from another scientist in a video between 2021-2023, how she shuffles through video content is not up to me. But I had a ring that day, and this one stuck.
To make this easier to understand: The many-world hypothesis says there will be a change of perspective, which we can define no less than to a psychological nature and the need for acadamia behavior which physics can contribute to. Conservation of momentum says there will be a change of momenta, but the many-world hypothesis will continue. Some physcisits makes it a point that their own interpretation of the many-world hypothesis are different or inobstructable from the public. Inobstructable is a good precedence, but they can't fend for it. It's the many-world hypothesis. Why the systems and loops to momentum will be inobstrctable elsewhere, that's the conservation of momentum. Maybe you read them, and I'm telling you they are the same wave. It's just that there isn't a change of function. Get it? We're moving in both direction. Feel free to observe some more.
Momentum: The "product" "product" "product" (wave) of an object. This object is the "change" "change" of mass and velocity conserved of the object. The object is in "momentum." As soon as you grasp, NEVER SEE IN PHYSICS, the product, you'll have the content definition of this short comment history.
Well that was Sabine's lunch. I'll have to go find something else.
Was the laser aligned east or west during the experiment? What was Earth's rotational speed that day, considering earthquake-induced changes? What was its orbital velocity that year? In which direction was the solar system moving relative to the CMB? How does quantum measurement affect laser-beam splitter and COM dynamics?
I never understood the need to assume in quantum mechanics that superposition means something is in BOTH locales at once. It's only the probability that it's in one or the other, and once measured you now KNOW which it was. Momentum is conserved because if you tried to measure the momentum of the beam splitter you cause the probability field to collapse. There is never a time when the particle is "jumping" because the very act of trying to measure the indeterminant phase causes the photons position and momentum to be known.
QM realism instead of instrumentalism. With Pythagorean Forms hovering in the background.
It's can't be that the particle is in a definite position that is just unknown until it is measured though. In the double slit experiment, you get the interference pattern even when you shoot one electron at a time. That means each individual electron is going through both slits and interfering with itself.
That's not quite right though, it would be easy if it were the case. Superposition is real. That's the whole basis of the wave property of the quantum. A particle really does lose it's identity and spreads out into fuzzy uncertainty when it is left to it's own devices. If your theory about it simply being a probability was true then there would be no such thing as an interference pattern in the double slit experiment for instance. For the nail in the coffin you can look up the recent published papers were scientists have taken literal photos of superposition with a single particle seen to exist in two places at once.
It’s because when you split the wave function in, say, two parts, you can have situations where the two wave functions interfere with each other. That, is measurable!
It’s a very, very subtle effect! Even physicists, including myself, sometimes forget that part and derive incorrect results.
This occurs because there is no corresponding effect like it in classical physics.
Someday educators will figure out a better way to teach physics.
In other words, students often get taught classical physics for 1 or more years. Then they try to learn quantum mechanics.
@@fullyawakened Measurement is real. Sometimes unexpected interference is seen. Superposition is a backward derivation. Schoedinger's Cat.
Bells Inequality can be violated using hidden variables, if you do what every practical Bell test does: Throw away single detections. Throwing away single detections is an exchange of information between the two detectors, that causes the discrepancy.
The thing I don’t get about the many worlds interpretation is there are 10^78ish atoms in the universe, so every Planck second there needs to be an observation. The superposition of all those particles needs to spawn new universes, and the next Planck second it repeats. The amount of new worlds blows up instantly. Where does the energy come from when the worlds “split”?
If you calculate the energy in the entire multiverse, you have to weigh it by the probability of each multiverse existing. It is conserved as much or as little as it is always conserved in quantum physics. Not so surprisingly because it is, up to interpretation, the same theory!
@@SabineHossenfelder sabine what ur thought about jacob barandes formulation of quantum theory? i have come across it, he seem confident about it but as outsider then no way for me to judge its validity or usefulness.
I have a physics theory where leprechauns swim in cauldrons of gold coins at the end of rainbows. This is totally physical and definitely means something in the real world and isn’t just me being bored with an imagination. I dare say, it id the simplest explanation of all.
@@rushyscoper1651 She talked on twitter about that, conclusion: Nothing fundamental new.
Beyond that energy thing, that always sounded crazy to me.
It's been quite a while since I studied Quantum Mechanics, but as I recall that's like the Young's experiment, right?
The beam splitter acts like the wall with the two holes. If I recall correctly, it had a screen behind the wall with the two holes. If we'd only send a stream of particles through the wall, the beam would present a interference pattern, but if we'd attempt to measure through which hole the particles would pass, we'd have to interact with those particles via a photon for instance, as now we'd know the hole where the particle passed, the interference pattern would disappear and we'd get two gaussian distributions with the peaks aligned with the holes. Yet, the act of measuring the path of the particles would destroy their initial state because the photon used to measure their path would change the energy/momentum slightly. Yet, the wavelength of the photons would have to be shorter than the distance between the holes, or it would not be able to measure the path and the particles would present a interference pattern again.
If I also recall correctly, if we'd send single particles, as the number of test particles increase the patterns start to show.
This experiment seems the same, right?
Sad that the paper was written. Even sadder that it is heralded by a major journal.
The saddest part would be if it was written by AI.
Excellent stuff. It's refreshing to see a bad paper being completely shredded like this.
Firstly, the "multiverse" is abstracted throughout many papers in modern physics. Just a few weeks ago I had to tell an author his paper was nonsense because it was written in the "multiverse" nomenclature. I think it may have even been on this channel. He responded by telling me that just because a paper was written in such a manner didn't mean that the paper indicated that the "multiverse" theory was correct. I was like...
Secondly, the descriptions of superposition through the beam splitter isn't really making sense to me. You have to break regions of space, into phase space between an emitter and an absorber. The photon is actually absorbed by the splitters electro magnetic phase space. The concept of the photon particle doesn't actually exist. Its just a field of phase space that holds the superposition of the absorber within that phase space. If the particle is absorbed by the splitter, it creates a new phase space depending on the electro magnetic field surrounding it.
I hope that makes sense to you. It new physics basically.
Yes,the idea of a multiverse is just fantasy.
That just sounds right, and even if it wasn't, at minimum, how does one know that the splitter isn't acting as a pure detector...which it is isn't it, according to what you are saying?
@@stevedriscoll2539 Yes, the photon is absorbed by the splitters refractive index causing the splitter to gain in voltage before the photoelectric effect and re-emission. So yes, it could be considered a "detector"
@@Shadow_B4nned "phase space" I don't believe I recognize that nomenclature. Is that the new physics you are talking about or would I have read that in other books by physicists such as Max Born, or Richard Feynman? (Oh, to get old😏) Anyway that just sounds right how your are describing the action through the splitter
@@stevedriscoll2539 Phase space is a very old foundational concept for classical and quantum mechanics, and I'm not sure you can attribute it to any one person. It's not really "new". It's just new to the modern consensus. It basically gives a position and momentum to energy in space. It narrows down the wave function from any and all possibilities to that of only within the phase space. Using this method in quantum mechanics allows one to detail the superposition of photons within a phase space, between an emitter and absorber and not have the superposition of the photon abstractly described as existing in multiple phase spaces.
As far as the action through the splitter, it's quantified as an emission/absorption by the refractive index of the splitter. Which also affects the velocity of propagation. But we don't really need to know all that.
Again: a fantastic video on a topic I just discovered. A question about the paper. Have the authors correctly demonstrated that energy and momentum are separately conserved for every Quantum measurement outcome?
If super determinism is reality, then don't worry: nothing you do or don't do will affect if people will accept it anyway. Truly, Neitzche's favorite theory.
What if the photon becomes entangled & entanglement creates a spatial fold/portal via higher spatial dimensions or, in other words, a warp bubble forms between the photon in superposition. By making observations, you are collapsing the entanglement fold/warp bubble & so they return to being in one place/direction, as opposed to both.
The more we LEARN about the very small and the very large, the less we KNOW about the very small and very large. Thankfully, learning more about “the in between” is what improves our existence. . .
Not with conservation laws, but I've always had a question regarding th the many worlds interpretation.
If entropy increase is explained as a statistical mechanism, and there are a near infinite amount of other branching worlds. Wouldn't that imply that there's at least some where entropy is constantly decreasing?
I think you also can have this in just one universe in a sufficient amount of time. It´s what this thought experiment with the "Boltzmann-brains" is about.
Oi, that last point you make needs more space to breathe...ie I'd love to see a dedicated video on superdeterminism.
It exists, titeld "Why No Portals"
@@Thomas-gk42 thanks. I'll check it out.
What if we start with a superposition of lets say an electron with spin up and spin down? After the measurement we have changed the expectation value of the angular momentum by 90 degree, violating the associated conservation law. However, in many worlds it is conserved.
If a trees falls in the forest and nobody's around to hear it, does it make a noise?
Just because we can't see beyond the observable universe does not mean there's nothing there to observe.
Quite right, this is the "Plato's cave" puzzle. The problem is that if you're stuck in the cave and have never been outside, how can you know there is an outside?
Assuming there is something there to observe when we can’t observe it is no less foolish than assuming there isn’t.
Sabine, why would there be a problem with the non-locality of the momentum change? Wouldn't the process of the photon going through the beam splitter just entangle the two, s.t. the combined state of photon + beam splitter is in a superposition. if you measure one part, you fix the other. In essence, measuring the momentum of the beam splitter afterwards should tell you where the photon went. Or am I missing something?
Actually, no, Bell had another caveat to his measurements which allows for local realism without resorting to the (conspiratorial) Superdeterminism. Look at Harvard's Jacob Barandes' recent work which also eliminates superposition/states.
Superdeterminism doesn't eliminate superpositions.
The phrase "local realism" was introduced by sophists to confuse the discussion. "Realism" has no relevance to Bell's theorem, he never uses the term. There is not even a consistent usage in the literature as I can easily pull up multiple papers that define it differently. "Local realism" gives the impression that these two are incompatible so you must reject one or the other. Locality seems very well experimentally verified as Lorentz invariance always seems to hold up when put to the test, so the conclusion these sophists want you to draw is you should deny "realism" and thus devolve into idealism and mysticism. But the fact is Bell's theorem never had anything to do with realism at all, it had to do with local hidden variable theories, not local realism. There is no reason at all to equate realism with belief in hidden variables, as reality might simply not have hidden variables. You can see the writings of Carlo Rovelli on _weak realism_ or Jocelyn Benoist and Francois-Igor Pris on _contextual realism_ which posit an understanding of reality which is not dependent upon hidden variables, and thus is compatible with locality and Bell's theorem.
"Conspiratioral" - you use that boring old battle term of standard QM and biased philosophers, congrats.
@ I never said it did. Look at Jacob Barandes' work.
@ Lol because it makes complete sense that the polarized light from a quasar 5 billion light years away should directly correlate with the parameters "chosen" by the experimentalist, right...?
Curious: ... The part with the momentum transfer on the beam splitter ... The beam splitter itself being a macroscopic object that is in contact with the environment and the observer ... Now if it was hypothetically possible to measure the momentum transfer of a single photon on the beam splitter right away ... (pause)
I just try to get ahead around the idea that the superposition of the photon should break down right away, as soon as I measure the momentum at the beam splitter, but if I don't do it, the superposition should persist. So basically I have the momentum of the photon and the beam splitter in and entangled state, right ?
But the macroscopic beam splitter and its quantum state is basically not in any way shielded from interacting with the environment and me right away. Isn't there a problem with some common interpretations people voice all the time ? Or maybe this is exactly the remark about ''only superdetermism works'' ...
I am not a physicist, I am just wondering, what interpretations of ''measurement'' and ''collapse of the wavefunction'' get immediately ruled out by this experiment, if any. Maybe it's just me being confused. 🤔
New Science should change its name to No Science for publishing an article showing such fundamental misunderstanding of the basic tenets of quantum physics.
The word "nescience" has got it covered.
@@picksalot1 Had to look up that one and it is perfect. Thanks for the education.
Because this is a literature and physics main concern is the current event rather than the setting of social science, it's important for contributors to reveal what they think about theories around boundaries. This is very credulous with Albert Einstein pushing quantum physics to a space where colleagues can grasp the conservation of momentum, almost like the simulation game in 3 body problem.
Why would you think the beamsplitter is not also in a superposition of left and right, entangled with the photon? And the measurer, upon measuring, entangles itself with the photon?
Being a quantum gravity question, I don't expect it to be compatible with general relativity.
An anthropological approach is required here. We have exactly the same brain as our hunter-gatherers ancestors. This brain was optimal for a single task that was connecting dots. The ability to connect between finding tiger shit and the actual presence of a tiger was vital for the group survival. Same thing for buffalo dung and the actual presence of a buffalo herd. Unfortunately, quantum physics is far remote from tracking a tiger from his shit. Therefore, many people will resort to a religious viewpoint like multiverse or a conscious universe etc. rather than to admit their brain is sub optimal for this task.
I agree, but what´s your consequence? Give up to solve an inconsistency (measurement problem) in physics?
Isn't momentum a correlated state between the superpositions of the particle, as measured by the wave function? Analogous to how an electron doesn't have a separate charge for each of its possible positions around the nucleus. Similar to how states are correlated between entangled particles, so that there's no need for information transfer that defies locality?
My simple thought rebuttal to MWI was simply: "Infinite universes being created every couple of Planck times? Where's the energy coming from?"
It’s inherently antiphysical comic book level logic and always has been.
So, does this mean that the mirror also goes into a quantum state of having been moved ever so slightly vs still in the same spot it started? And then once the photon is measured the superposition of both the photon and mirror settle out?
Thanks, Sabine. You demolished their argument ;)
The single photon cannot go through the beam splitter without having an interaction. This is at least very clear for the instance of the photon going off at an angle.
I think The authors are still kind of on the right track. Everything we've measured in particle physics are just large averages. Because of the nature of particle physics, the only thing we CAN measure are averages. Then we base our math on those averages. There certainly could be all sorts of super deterministic nonsense happening below the level we're able to measure but we'll never know. The universe could very well be clockwork at its core, but if the gears are smaller than we could ever measure directly, we'd have no way of ever actually proving that.
Yes, but in atomic physics, we can measure single events. That's what the 2012 Nobel Prize was about.
I agree mostly, except your suggestion of the authors being on track. The authors wrote this paper on the basis of their (baffling) misunderstanding that momentum is merely conserved on average in our current theories (e.g. standard model) of quantum physics. I would consider them to possibly be on the right track if they instead state their doubt about our belief in the conservation of momentum and adequate justifications for said doubt.
@@welhtataum Statistics is considered like aviation in some academic disciplines. The momentum being conserved in average is because if a system is being looped, like a number system, which is a "system", then the product, which would be the loops, would appear as numbers that are average, but not within distribution to the total system. The reason likely why Sabine did not shot it down because in General Systems Theory, there is a possibility that systems tells us about other systems. Maybe you've played 6 degrees of Kevin Bacon on your Nintendo Swithc.
Wouldn't an easier way to look at this be that measuring the momentum change of the beam splitter would be effectively the same as measuring the location of the photon? The photon detectors become redundant because the momentum change (or not) already tells you which way the photon went!
The biggest problem in Physics is funding.
Does that mean measuring the movement of the beam splitter destroys the superposition, because it would tell, which way the photon went?
Make the Universe Great Again. It's the best place in the Multiverse to invest in. Here you'll get the lowest taxes, the lowest regulatory burden, and most protection from competitors in other universes. Should you wish to import products into our universe rather than produce them here, well slap 100% tariffs on your goods.
😂
I'm afraid I was lost at the delayed (or was it non-local?) conservation of momentum and super-determinism. And I'm absolutely terrified of Bell's Theorem. It doesn't seem like the wave collapse has to go back and interact with the splitter at superluminal speeds.
What's worrisome is that if these are "credentialed" physicists and they don't know or understand what you appear to believe is fairly fundamental, then what use are credentials? Or why wasn't / isn't it covered in coursework?
Knowing anything real about the world and outsourcing so much understanding to a trust relationship is extremely hard!
Keep em honest Sabine
If the proton deflector doesn't move because the left/right deflection hasn't yet been observed (Accounts for both options), does it move when or after the position of the proton is observed?
'Physicists claim...'...here we go again...
I'm not getting it. Momentum is already always conserved in this experiment, in the form that the beam splitter takes up some of the photon momentum upon reflection, a well-known phenomenon also called radiation pressure. Can someone please illuminate me which part I'm missing here?
you are missing the last part of the video
@Casey-Jones Thanks! I had stopped watching there because of how it was presented, and I thought this was so blatantly, obviously off. Should have known better, Sabine has her physics together :D
👇🏻 Superdeterminism Gang
Superdeterminism is sad but true
Like a global thermodynamic minimum
God bless you
I have a problem in my mind I don't understand : if two electrons are in quantum states, how do they know they repulse each other by electromagnetic force ? They send each others a photon, isn't it ? So they interact with each other (they observe one another), so they can't be in a quantum superposition, can they ? So how can two electrons ever be in a quantum superposition ?
Best video I've seen on this problem :) Excellent
Super liquid helium 2, when a blob of it is shot at a piece of paper, at contact, the blob splits apart and then spreads over the surface of the paper, the thing is that NO FORCE is exerted on the paper, the momentum temporarily stops going forward. The liquid reaches the edge and goes around and back 5o centre of the paper on the other side where the blob reforms and then continues moving forward (momentum returns) and departs the paper as a reformed blob heading along the original trajectory!
Issue is that temporarily momentum not conserved.
A specially designed device could harness this strange property of superfluid to generate an overal lthrust or overall warping on space, Perhaps by interrupting the superfluid state at a point in the above steps, so that the effects on both sides of paper do not balance out duetothe superfluid state being altered and producing a none net zero effect.
Perhaps the above is an explanation for how apparent gravity effects have been observed by super conducting spinning discs in magnetic fields, where tthe paper can be represented as the surface of the superconductor, on one side (inside the superconductor) the electrons flow as superfluid, and outside is non superfluid. Thus producing a imbalance in effect on gravity and thus produces gravity effects.
I always had a somewhat 'logical' argument against the Multiverse. And it's quite simple, likely pointing to my own lack of knowledge. It goes like this: The multiverse theory states that any decision branches off into multiple other 'universes'. So that in theory, anything that ever can, will happen in some universe out there. The problem is that if ANYTHING can happen then what if 'something' happens that disrupts the nature of the multiverse, sending shocks through all other multiverses, perhaps even shattering it? You could think of many, many scenarios where any kind of disaster could break down the multiverse. So if ANYTHING can happen in some universe anywhere, then that must by definition happen, or have happened. It didn't (so far, as we can observe).
Sabine, can quantum mechanics explain a falling drawer in the bathroom after a huge fight? My life has been put into chaos and I’ve been noticing many strange signs from the “universe” After that I got a peculiar one hour panic attack. The idea of panic has been recently more researched right?
Also, I’m noticing quantum mechanics in today’s many artist’s popular music
Is it possible that “supernatural things” are happening in the “centres of panic”?
@@marceldobosz6476 I don´t think that "supernatural things" have something to do with quantum mechanics.
@ thanks for the reply, maybe it’s a mix of quantum mechanics and chaos theory? I will eventually learn quantum mechanics on Sabine’s course of course. I’m a young industrial designer and made a bachelor degree in design about the Moon myself. Greeting from Poland 🇵🇱
@ Hi Marcel, yes one can´t rule out these things, therefore I´m enthused about Dr.Sabine´s work on superdeterminism, she´s one of a few scientists who think out of the box on this topic and haven´t given up to slove the measurement problem. Greetings from Cologne.
As I understand it Bell's theorem relies on a statistical method that proves there cannot be any "local hidden variables." Is there a good reference that explains this assumption for lay person? Thx
Your gentle touch of Bobble Albert's head was cute.
😅
What happens when a particle in Superposition is viewed by 2 people at the same time can one sees it left and the other right?
OH What a tangled particle we weave when first we practice to [Quantium] perceive.
Asking on behalf of a layman engineer. Could one measure the beam splitter to see if it was imparted momentum in the direction of the photon? That way you could 'measure' which direction the photon went without detecting the photon itself? Or would that also collapse the wave function?
Could someone help me understand what she was saying about the "violate measurement independence" and "superdeterminism" point? Apparently it's really important as Sabine was really emphatic about it, but i didn't get what it was at all? What is the very important key point these scientists seem to have gotten wrong?
I hate the many worlds theory personally.
It seems to me that it violates the conservation of matter more than the conservation of momentum.
Every time you fire a photon at a beam splitter an entire universe has to be created for both outcomes to happen.
That's a lot of matter to just appear out of nowhere. And it has to be happening an infinite number of times every second, because it's not just that beam splitter experiment, it's every time something goes into super position. And it's not just all the super position events in one universe, but the super position events in an infinite number of universes.
So if matter can't be created or destroyed, but it's being created at an infinitely exponential rate, that seems to be a problem.
Then again, maybe the infinite number of universes layered on to each other is the actual source of dark matter. It's just us in a universe that is almost exactly the same as ours.
And dark energy is just the pressure of infinite universes coming into being.
It is not created it was there all the time. For a person in that universe it is yours that was created.
Can you clarify your postion?
So did AI hit a wall and is overhyped or are AI companies dominating the world in the near future?
How do papers like that get published?
It just occurred to me that if you had a photon of high enough momentum to actually have a measurable effect on the momentum of the beam splitter (like for instance X-ray impinging on a micro-electromechanical system = MEMS cantilever), then the photon should end up not being in a superposition between having reflected or gone through.
How do you "measure" the photon? I've always found it odd that the wave function collapse happens when you observe which slit it goes through. How is it being observed?
Thank The Mighty Multiverse for Sabine, otherwise many of us zombies would be totally brain dead and clueless.
I thought the force vector diagram was interesting. I couldn't help but think of it in terms of an individual particle. If the particle hits the beam splitter does it not impart information (in the form of momentum) before the quantum waveform collapses, (that is to say the particle is resolved either left or right)? It seems to me that this principle could be used in a similar way to the Quantum Erasure experiment.
In a thought experiment, you could place many of these reflectors next to each other. In each case, the particle has to make a decision: left or right.
That means, there can be many outcomes of the experiment, but you only measure one, namely the outcome.
Does that mean that all possible states exist at the same time? If there are many reflectors, that would create a near-infinite number of states, and thus a near infinite momentum.
Of course near-infinite momentum doesn't exist, so the states don't exist at the same time, even though we only have one measurement.