@@elitedelobos Puede ser de origen judío, pero nació en Lima, creció y estudió en Lima, graduándose de la Universidad Nacional de Ingeniería. Es recontraperuano
It's important to point out that when the polarizer is aligned at some "middle angle," then the light that comes out is NOT identical to the light that went in. Not only does only a fraction of the light come through, but that fraction now has polarization aligned with the POLARIZER, not aligned as it was going in. The polarizer "turns" the polarization angle so that the outgoing light is aligned with it. This raises the fascinating situation where you can put two polarizers at perpendicular angles together, and no light gets through. But if you then slip a third one in between the first two aligned at, say, 45 degrees, then suddenly some light does get through.
This lecture has nothing to do with me but I became entranced with his style and voice! And I actually learned something new in quantum theories. Thank you Sir.
Thank You for making it understandable !! I am a software engineer in network domain. I just watched these videos(first 4) out of curiosity, and I was able to understand a rough picture of what's trying to be conveyed. Last time I studied physics was in pre-college days.
I can tell he is a good teacher because I understood this little "lecture" better as when my teacher taught me the same subject, even if my teacher spoke my first language (french), and this teacher speak english, that is harder to understand for me.
In some sense, the fact that he is peruvian and has as first lenguage the spanish, it make him use simpler words to do his lectures so it's easy to follow him in his thoughts.
I definitely agree when you mentioned that it's good to learn from physicists and it's useful that we have them, it is good to make new explanations for what comes next.
Bertrand de Born I’m sorry MIT is one of the preeminent science and engineering schools on the planet. So this professor has earned his position in that esteemed University. Have a nice day. Also no one ridiculed anyone-I think you’re projecting-and I’ve learned quite a bit thank you much 😃😉
Bertrand de Born oh please-try this-why don’t you go to Feynman’s lectures in Physics and start reading at volume 3. You learned this in 9th grade huh? I doubt it. This is Quantum Physics-you did not learn this in 9th grade. Go to OCW, and look at the ENTIRE CLASS genius. Tell me, why do you have to use the renormalization group in Quantum Electrodynamics? How do you know you understand English? Fella, you lost all credibility when you questioned the status of MIT. All credibility. Have a nice day, remember not to go out as you don’t want to be exposed to SARS-Cov-2 and get COVID-19. There’s a good fellow. G’night 😉😃👍. Oh and we are done.
Well, the bell inequality just shows that you cannot have both a local and hidden variable theory combined. If you have a hidden variable theory, it has to be non-local, and if it's local, it has to not rely in hidden variables
Thank you. Was about to make a similar comment. Bell himself was a proponent of Pilot Wave theory aka Bohmian mechanics. A completely deterministic, nonlocal, hidden variable theory.
There is a difference in the way of thinking of the inequality sign (or information bra-ket) when we see light as Einstein inertial system and when we see light as quantum entanglement information. Is a very effective inertial vector. In quantum information entanglement, since it is not an inertial system, it is considered as |photon:〈xψy〉:photon｜, and it is an information system that should be distinguished from the inertial system, but (photon:ψ>)=(photon: :ψ〉), the optical inertial system and the optical information system are equivalent. This is an important lecture from the perspective of consideration.
.... what percentage of polarizers are unemployed .. that's what I wanna' know ... it seems the good professor overlooked this dilemma during the lecture ..... hmmm .....
@@brivda I had written that comment a month ago. I have no recollection what this video was about or what other video I was thinking about. Not to mention RUclips won't allow video comments.
Lo cierto que la UNI no hizo nada por él, pudo haber estudiado en cualquier otra universidad e igual hubiera sobresalido, más bien la UNI debería estar agradecido de haber acogido a una mente tan brillante
I appreciate the fact he is saying what actually happens with the correct terms, instead of abstracting it all away. I watched a similar MIT lecture but the professor was using terms like "color and hardness" to avoid "confusing us" but for me it made it really hard to picture anything in my head and follow along cause electrons don't have "color" or "hardness" in the classical sense
That's an exercise to get students to understand that nature does not consist of phenomena that can be described by commutative algebras alone. It's the big insight of Heisenberg... except that he had to figure it out without help.
So with respect to Linearity discussed in previous lectures, Beam of photon should be described as Beam |photon_alpha> = a * cos_alpha * |photonX> + a * sin_alpha |photonY> Where a is some constant
We can write an expression for a wave, psi = exp(ikx-wt), is complex function. That's it . We represent sinusoidal waves by complex function. It's a representation
What are all the physical processes (besides the behavior of polarized photons) that are non-deterministic? Is radioactive decay non-deterministic? Is there a complete list of non-deterministic processes somewhere? Are all non-deterministic processes somehow the same process at their core?
smalin yes as quantum mechanics describes radioactive decay-yes. Same process at their core? Only in the sense that they are part of the class of non-deterministic things. Ah the point behind quantum mechanics and quantum theory is that what we think as determined is at base, not deterministic.
It's not an easy question to answer because what is deterministic (or whether anything is deterministic) depends on which interpretation of quantum mechanics is correct and we don't know which one is correct. For example, everything is deterministic in the Many Worlds interpretation, including radioactive decay, since the wave function describes all possible events. Questions about determinism are usually left to philosophers of physics nowadays so the Stanford encyclopedia of philosophy is a good starting point to read up on some of it. plato.stanford.edu/entries/determinism-causal/
@@eastwestcoastkid In my view It is the instant (now) that determins reality, on the base of what is determined previously. So that the instant is not completely severaged. By this, I do not means that the instant acts upon reality, but that it is the concrete manifestation of everything that takes place in the instant. Continously. But "free".
francoisdeletaille that is an interesting philosophy-but at base Quantum mechanics and Quantum theory hold that physical reality is not deterministic-hence the uncertainty principle.
Nonlocal hidden variables would not be deterministic, though. If information can travel at infinite speed, then events are determined instantaneously, not by past states.
This professor was a former student of one of the best universities in Latin America, the prestigious National University of Engineering (Peru). He was not your average student or teacher. He is a living legend, a GENIUS. Feel privileged to receive their knowledge in your country. Saludos 🇵🇪
Si bien la UNI es una de las más díficiles de ingresar en el Perú, no es una de las mejores universidades de Latinoamérica, de hecho, en rankings de universidades, no llega al Top 60 de Latinoamérica. No es por desmerecer nada, pero las cosas como son. Y sí, el profesor es un genio.
Solo no es de las mejor de LATAM porque no sabe investigar seriamente con metodología real. Pero que cubran este hueco y verás como brillará frente al mundo 😎
11:00- Really true, consistent with the wisdom there are more unknown unknowns than known unknowns. 15:25- This statement makes the superposition concept a bit easier to comprehend.
Nothing he says explains to you where superposition really comes from. If I were to test you orally on that question, I could easily fail you, right now.
Polarizers are not filters, they are re-radiators. Imagine two antennas connected by a coaxial cable. The interfaces between glass and air are the antennas and the glass is the coax. Light impinges the front face, just as an antenna. If the antenna's polarization matches, the light enters the glass, propagates and exits according to the polarization of the back face (antenna) of the glass. Using this correct model of a polarizer explains polarization completely and without mystery. Bell's Theorem is not required, only Maxwell's equations.
Prof. Zwiebach is actually very good, but for any "not perfect English speakers", it was absolutely necessary the presence of subtitles....in English! Anyway, thank you for the lesson and greetings from Athens, Greece.
The figure in this explanation would be better if shown in three dimensions. The professor’s explanation describes a plane wave oscillating in a plane parallel to the z-axis at an angle alpha to x--z plane. Then the closer the plane of the wave gets to the x-z plane, the greater the transmission of the wave through the polarizer.
Wow. Light starts waving at what point? My theory, however so humbled, is that light wont wave until it runs through its variance of color, atmosphere layers and was used different to assert waves. Like the energy collects some seeing alternating current but has proven its not the only current.
15:41 but it is wrong only with LOCAL HV!!! 16:11 classical = non-contextual, with the 3 components of spin pre-fixed, that is clearly wrong, knowing how spin experiments results are
Bell just showed that a HVT is non local and, if the formalism of spin is correct, that it is also contextual. Look at the interpretation of spin in the works of David Hestenes and other physicists, and contextuality desappares
The funniest lie ever; if they cannot determine it, then the determinism is lost. The amount of grandiosity of the title of this video is ultimate; despite it appears to be super humble.
Our ability to determine is irrelevant if there are no local hidden variables. Bell's experiments prove that particles literally do not inherently contain the values needed to predict their behavior.
@@eoinlanier5508 There are no particles in nature. There are only quanta of energy. That there can be no local hidden variables follows directly from relativity. We never needed Bell for that. I would advise you to read Bell's paper. He says so himself at the end of it. ;-)
What a lovely man. So calm and precise. I remember being introduced to Imaginary numbers at school. POW. Mind blown. Two years later in college, they're vectors. Oh. Why didn't they say that ? On a par with year 2 maths class. Ok. Let's consider n. n is any number ! Pow. n is clearly a letter. Dropped out of the top maths class soon after. Got back in again though. Just the whole year missed and forever holding on by my finger nails since.
1:17 the classical notion of particle has zero size? I thought the classical notion of particle is defined as having absolute physicality hence having aspect of substance and dimension i .e. size. This is why it is deterministic. Phenomena of light break down the classical notion of particle with its fundamental state of duality of wave n particle
So... does that mean photons are constantly changing states, (polarization but not frequency?), before they are measured, because they exist as a wave function? Is that why when sent through one at a time all go through or none do? Moreover, why is it that when polarized light is sent through three polarizers, at right angles to each other... some light gets through? Is it because since it is not measured, some photons in the wave state change polarization between polarizers? Then why do three allow passage but two block all light? Plus why is it a wave function rather than a matrix of possibilities?
As far as photon/polarizer debacle: could it be that the photons are entangled in opposite spins and the spin is the deciding factor as to whether the photons goes through.
10:00 When considering a scale of the atoms, each photon incident on the polarizer seems to be a unique experiment. On that level of detail it is not a billion of equivalent experiments. Each photon has a different path. Leading to different sequence of interactions in the material. What do you think? Are they equivalent?
Surely - when we observe light as a wave, it behaves as a wave (Polarization, diffraction, superposition), and when we observe as a particle, it behaves as such. (Photoelectric effect). I get the feeling that you are asking the light to behave like (Commit to being) a wave and then questioning what happened to its particles...
Even Bell himself didn’t think that he proved the impossibility of hidden variables. Travis Norsen: in his book (titled ‘Foundations of Quantum Mechanics’) says: “There is a kind of rich and tragic irony here, in citing Bell as having supposedly refuted hidden variables theories …, Bell’s theorem was actually inspired by Bohm’s 1952 pilot-wave theory papers, and indeed Bell remained far and away the pilot-wave theory’s greatest champion until his death in 1990.”
the clue is in the title guys - Open Course. For anyone who wants to watch. And you've got to be pretty good at your subject to explain quantum physics so that anyone can even approach understanding that!
Does anyone know what experiments he is referring to when he mentions people have ruled out the argument "It is the unknown subatomic structure of the polarizer that determines which photos pass vs are absorbed?"
quanta was energy unit measurement. if we can program photon in twisted wave guide. is there two type of frequencies minum to have light so should it be Frequency**2 ) * wavelength= speed
What if _i_ - the imaginary component of the wavefunction - is the "hidden variable" that Einstein theorized might be present for photons? I mean, it isn't unreasonable to expect the _i_ component to have _some_ physical manifestation, is it?
The dynamics are when photons change.. Photo..photons..reflection of crystal or diamonds...photo..is it graphic like measure? Memory or weight divided by size of reflection times exponential aspect of ...so measure the remember..no measure the distance real..by the compared carbon measure..thanks for ?? All this.
During the introduction of the polarizer on the x-axis, energy is incident on the polarizer and this energy is lets just say fractional. Remember we have already assumed em waves here. I am failing to understand the subtle transition when the professor says energy but talks about the number of photons. How does one total the energy of the field which is proportional to the square of the electric field quantified as the number of photons? If we are indeed talking about the energy of one photon itself, and that energy should be a fraction of what was incident, aren't we forgetting that this was the case with the assumption that the energy was of an em wave? In short, I guess I am having a difficulty understanding when it is the energy of the em wave and when the energy of a photon.
The total energy is just the sum of individual photon energies. The classical wave, on the other hand, is an approximation that is valid for large numbers of photons. Think if it this way: dice rolls can have outcomes 1, 2, 3, 4, 5, 6. The average of many dice rolls will be a number close to 3.5, which is not a possible outcome. Same here. The smallest individual measurements will reveal photons with discrete amounts of energy. The time averaged sum of all these measurements behaves like a classical wave.
@@lepidoptera9337 so the average energy is proportional to the square of electric field here? Also, in the Young's experiment, while sending individual photons, we observe that it is as if photons have interfered with themselves creating the interference pattern. I understand this is what we "observe". But my classical mind wants to know just why?
@@chaoticlue What we are measuring are energy, momentum, angular momentum and charge. The averages of these measurements can be described with abstract quantities like electric and magnetic field. Interference is the absence of self-interaction. We are desperately trying to teach this in high school using wave pools and wave machines. 99.99% of all kids misunderstand the actual goal of that lesson. It is NOT trying to demonstrate interference as some "active physical mechanism". It tries to demonstrate that individual waves DO NOT interact with each other. At the photon level that means that photons do NOT interact with either each other or themselves. That's why the number of photons doesn't matter. Every photographer knows this, by the way. A scene captured on film or with a digital camera looks exactly the same, no matter if it was taken with a high intensity light source in a short amount of time or a low intensity light source during a long exposure.
@@lepidoptera9337 I was merely stating what was said in the video about "it is as if the photons have interfered with themselves" Of course the diffraction helps with the interference. And I am not disapproving of photons' absence of interaction with others (but why actually). My doubt is how to justify my classical mind that the "interference pattern" of a series of photons spewed back to back were able to give out the same pattern of a wave interference or rather wavelets interference? I guess I am confused to the core and hence am trying to look for resources that could give me actual meaningful insights into this field instead of talking about the prestige or the magic of this science. The method of teaching this field should also be unique is what I feel, because we've been hard wired to think classically. And even abstract examples from classical world seem highly misleading atleast to me.
@@chaoticlue The reason for the patterns is purely geometric. There is no physics in the bulk (that's what "self-interaction free" means) and therefor effects on the boundaries can only depend on the conditions on the remaining boundaries and the relative distance of boundary points from each other. We can eliminate the first dependency by using a single point source. That means that now the only "physical observable" that is left are geometric distances between the source and the detector. Because of relativity there can also be no absolute dependence, so we are basically down to geometric path differences (phase differences). I don't know if there is an easy handwaving argument to develop a good intuition for this. If there is, then I haven't heard about it. You can learn to "see this" by staring long enough at the integrals that form the solutions in the theory. It's readily visible in the general form of Lie-groups representations (exponentials of the generators). Is that real understanding? You decide. The physics of empty space is counterintuitive because we are used to think in terms of "contact physics" where nothing happens unless some thing touches some other thing. This is the exact opposite. Whatever happens happens because absolutely nothing touches anything.
The problem is that the photon is an absorbed or bound quantity, when it's free you cannot count the bosons, so saying things like ''perhaps billions of them" is referring to a certain energy or intensity, and is still a classical line of reasoning. Yes, you can count what you can catch, but the wave function occupies the whole Hamiltonian state space between t0 and t1. Indeed when a radiation source emits at a given frequency and amplitude, everything is determined, N bosons doesn't factor anywhere. When you divide up the radiation's amplitude by Planck's constant, you regain your frequency, not N ''photons''.
There is no wave-particle duality. That's just a nonsensical term from the great confusion phase of quantum mechanics. There are uncertainty relations and they also apply to waves on the ocean. They simply have nothing to do with quantum mechanics. They are properties of certain linear operators over function spaces... every theoretical description that has them has uncertainty. Acoustics, seismology, water waves... doesn't matter.
@@schmetterling4477 ..😀. then the question comes, what are subatomic particles made of? are "electrons", "protons", "neutrons" , solids, liquids, gases or what state they are?
@@nickharrison3748 There are no subatomic particles. We are teaching in high school that a photon is the amount of energy that gets emitted into or absorbed from the electromagnetic field. Energy is not a thing. It's a property. Every time somebody talks about "particles", all they really mean is energy flow from one system to another. This is simply a matter of poor language choices that have been confusing minds for the last 100 years.
@@schmetterling4477 ..sure..I try to understand what you are meaning. yes, photons are just energy or forces or disturbances in EM field. so, you mean, all subatomic particles are just disturbances in their respective "fields". every particle has its own "field". field is the medium. so water is in its own "ocean" or sea field.
@@nickharrison3748 There is not even a disturbance. That's just your mind hanging on to classical concepts that don't exist on the quantum level. Take a piece of spacetime. Divide into two sections. On has more energy than the other, then that energy can flow from one to the other. The smallest possible energy flow of that kind is a quantum. That's it.
How would polarizer work on the moon... example... Why astronauts didn't see their own foot in the shadow area?how light can be curved by gravity. photons don't have mass( just energy)? Influence of atmosphere?? Complex....
The notion of photons and their relationship to determinism invites intriguing questions about the fundamental nature of reality. Photons, as quanta of light, exhibit behaviors that can appear inherently probabilistic, particularly when analyzed through the lens of quantum mechanics. The famous double-slit experiment demonstrates that photons can behave as both particles and waves, exhibiting interference patterns that suggest an underlying randomness to their behavior. This challenges classical notions of determinism, which hold that future states of a system can be precisely predicted given complete knowledge of its initial conditions. Instead, the behavior of photons often embodies unpredictability, highlighting a universe where inherent uncertainty reigns, thereby prompting deeper philosophical inquiries into the fabric of reality and whether determinism can truly coexist with the principles governing quantum mechanics.
But what if the polarizer inside has some frequency of reaction states to light going through? In some states it allows the photon go through, in another doesn't. No need in probability.
From Rene (Decartes)'s Materialism to Russell (Bertrand)'s Mechanicalism..our view on the Materialistic world was profound and set forth every Rational Aspect of our understanding. So we call the elementary ingredients study, the PARTICLEs Physics, due to Democritus 's undividable Atoms (though later we found many "p" are much smaller than 'P'). Light is particle called Photon, electric is classified as lepton, 900 times smaller than Proton (Neutron). Even binding Energy we considered them as Gluons-exchanged ? And same as gravity, forcefully we try to MAKE such Interaction as GRAVITON exchange process, another kind of tiny(minute) PARTICLE as well. All were found by materialistic view of the universe, Interacted together with some deterministic MECHANISM, either exact or by STATISTICS (that You consider it UNdeterministic.)
I don't buy the particle simply moving in wave It's an estimation of a particle Thet is light weight...gets hit all over the place... Looks like a wave as an average. We have to find the particle where how it exists
@@lepidoptera9337 it does not matter as the Bell inequality is both incomplete and inaccurate. Bell was more of a philosopher and not so much a physicist.
@@bustercam199 Reading the original publication that you are talking about does matter, because if you didn't actually read it then I won't take you seriously. I will instead treat you like a troll. Would you like some more attention with that? ;-)
Perhaps A new type of individual “determinism” emerges as an observer concentrates with dedication and energy, and on a result, turning a probability into a specific intentional personal outcome. Focused Thought with passion and energy, eventually creates through photons, light, what the observer concentrates on, with energy. Perhaps this points to the possibility of the hidden variable theory harmonizing with our participation making a phenomenon complete …with a result we intentionally zero in on.
Que nivel de clase de este profesor . Orgullo peruano .
No es peruano es Judío Ultramar. Judío ...
@@elitedelobos Puede ser de origen judío, pero nació en Lima, creció y estudió en Lima, graduándose de la Universidad Nacional de Ingeniería. Es recontraperuano
@@juanrodrigovalencia No. El siempre la tuvo clara. Es un judío y tiene nacionalidad judía.
@@elitedelobos En serio? Y tiene pasaporte "judío"? Por favor JAJAJAJJAJA
@@elitedelobosmira mongol si Vienes a opinar sin info mejor ni opines lapiz😅
This is brilliant. This professor explains things extremely clearly.
Agreed totally. His pacing also is fantastic
Lol.
He is a pseudo scientist!
I'm 12 and I got it too
Does he tho ?
Besides the wonderful clarity in his lecture, I am amazed at his very clear, beautiful, and organized writing on the board.
Barton, el único estudiante en la historia de la UNI que se graduó antes de terminar su carrera.
It's important to point out that when the polarizer is aligned at some "middle angle," then the light that comes out is NOT identical to the light that went in. Not only does only a fraction of the light come through, but that fraction now has polarization aligned with the POLARIZER, not aligned as it was going in. The polarizer "turns" the polarization angle so that the outgoing light is aligned with it. This raises the fascinating situation where you can put two polarizers at perpendicular angles together, and no light gets through. But if you then slip a third one in between the first two aligned at, say, 45 degrees, then suddenly some light does get through.
El mejor alumno de la historia de la UNI.
Es de mi facultad
@@ARCP-mj1mrq nunca lo ejerció
@@paultarazona7989XD
@@paultarazona7989😂😂
Buena la profesión le sirvió para hacer investigación, dónde invierten otros países extranjeros.
Great Teacher. Takes time and explains well. Defined indeterminism very clearly.
Well spoken with excellent handwriting. A rarity among physics professors
there's something about writing on a chalkboard that just makes it much better than presentation slides as a teaching medium for showing equations
This lecture has nothing to do with me but I became entranced with his style and voice! And I actually learned something new in quantum theories. Thank you Sir.
This guy is really good. A brilliantly clear explanation. Moving slowly enough for a dummy like me to grasp it. No wasted words.
Thank You for making it understandable !! I am a software engineer in network domain. I just watched these videos(first 4) out of curiosity, and I was able to understand a rough picture of what's trying to be conveyed. Last time I studied physics was in pre-college days.
peruvian's proud!
@@andressuarez6153 así es.
This professor is outstanding! It’s been over 30 years since I studied QM/QP. Never used it so forgot it. Great reintroduction. Thank you sir.
Sure, sure. If you had studied quantum mechanics for good, then you would know that he kind of sucks, of course. ;-)
I can tell he is a good teacher because I understood this little "lecture" better as when my teacher taught me the same subject, even if my teacher spoke my first language (french), and this teacher speak english, that is harder to understand for me.
In some sense, the fact that he is peruvian and has as first lenguage the spanish, it make him use simpler words to do his lectures so it's easy to follow him in his thoughts.
This exposition is as clear as can be
I definitely agree when you mentioned that it's good to learn from physicists and it's useful that we have them, it is good to make new explanations for what comes next.
Such amazing job Mr. Zwiebach! Thank you...
What a wonderful teacher you are, if I may say so. Thank you for sharing this lecture with the public. 🤓
A shill can only repeat the obvious -- it's in the public.
🙂
Bertrand de Born really?
Bertrand de Born I’m sorry MIT is one of the preeminent science and engineering schools on the planet. So this professor has earned his position in that esteemed University. Have a nice day. Also no one ridiculed anyone-I think you’re projecting-and I’ve learned quite a bit thank you much 😃😉
Bertrand de Born oh please-try this-why don’t you go to Feynman’s lectures in Physics and start reading at volume 3.
You learned this in 9th grade huh? I doubt it. This is Quantum Physics-you did not learn this in 9th grade. Go to OCW, and look at the ENTIRE CLASS genius.
Tell me, why do you have to use the renormalization group in Quantum Electrodynamics?
How do you know you understand English?
Fella, you lost all credibility when you questioned the status of MIT. All credibility.
Have a nice day, remember not to go out as you don’t want to be exposed to SARS-Cov-2 and get COVID-19. There’s a good fellow. G’night 😉😃👍. Oh and we are done.
Well, the bell inequality just shows that you cannot have both a local and hidden variable theory combined. If you have a hidden variable theory, it has to be non-local, and if it's local, it has to not rely in hidden variables
Yeah pretty good argument 🤷♂️
Thank you. Was about to make a similar comment. Bell himself was a proponent of Pilot Wave theory aka Bohmian mechanics. A completely deterministic, nonlocal, hidden variable theory.
"It's a debacle! A total disaster!"
Well spoken with excellent handwriting. A rarity among physics professors. Maravilha de aula! Eu diria um pacote de fótons de aula! Parabéns!!.
There is a difference in the way of thinking of the inequality sign (or information bra-ket) when we see light as Einstein inertial system and when we see light as quantum entanglement information. Is a very effective inertial vector. In quantum information entanglement, since it is not an inertial system, it is considered as |photon:〈xψy〉:photon｜, and it is an information system that should be distinguished from the inertial system, but (photon:ψ>)=(photon: :ψ〉), the optical inertial system and the optical information system are equivalent. This is an important lecture from the perspective of consideration.
"That's what polarizers do for a living" :)
lol
.... what percentage of polarizers are unemployed .. that's what I wanna' know ... it seems the good professor overlooked this dilemma during the lecture ..... hmmm .....
The polarizer proves that light is a wave and not a particle.
@Phoenix do you think Trump is a real president?
@Phoenix when the Suits come for you, don't answer the door.
Man, I just enjoy listening to his voice....
Me tooo I swear to God 😄😄😄😄
This must be the best lecture on loss of determinism on the net, much thanks.
You lost determinism when you flip a coin. Write parents to send more money.
I've seen better
No
@@nassimabed care to share the better video?
@@brivda I had written that comment a month ago. I have no recollection what this video was about or what other video I was thinking about. Not to mention RUclips won't allow video comments.
Brilliant lecture given by Barton Zweibach Sir .....
Thank you MIT and sir. Wish him long life and happiness.
I really like his handwriting
This looks so passionate
In that case I advise you to check out Nima Arkani-Hamed.
Si estuviera traducido al español, seria genial. Excelente Profesor. La UNI siempre destacando.
Lo cierto que la UNI no hizo nada por él, pudo haber estudiado en cualquier otra universidad e igual hubiera sobresalido, más bien la UNI debería estar agradecido de haber acogido a una mente tan brillante
Aprende inglés en vez de perdir subtitulos, por eso los egresados de la uni muchas veces terminan enseñando de profes en academias 🤣🤣🤣
Ese Barton solo copiaba en la uni yo lo conozco le ponían 20 los profes solo porque su viejita era bien bandida la prra😅
@@s0ulseeker.? Por no aprender inglés?, mano como en toda u siempre hay gente que no ejerce su carrera.
@@luchomarranoconcuerdo
I appreciate the fact he is saying what actually happens with the correct terms, instead of abstracting it all away. I watched a similar MIT lecture but the professor was using terms like "color and hardness" to avoid "confusing us" but for me it made it really hard to picture anything in my head and follow along cause electrons don't have "color" or "hardness" in the classical sense
That's an exercise to get students to understand that nature does not consist of phenomena that can be described by commutative algebras alone. It's the big insight of Heisenberg... except that he had to figure it out without help.
So with respect to Linearity discussed in previous lectures, Beam of photon should be described as
Beam |photon_alpha> = a * cos_alpha * |photonX> + a * sin_alpha |photonY>
Where a is some constant
We can write an expression for a wave, psi = exp(ikx-wt), is complex function. That's it . We represent sinusoidal waves by complex function. It's a representation
What are all the physical processes (besides the behavior of polarized photons) that are non-deterministic? Is radioactive decay non-deterministic? Is there a complete list of non-deterministic processes somewhere? Are all non-deterministic processes somehow the same process at their core?
smalin yes as quantum mechanics describes radioactive decay-yes. Same process at their core? Only in the sense that they are part of the class of non-deterministic things. Ah the point behind quantum mechanics and quantum theory is that what we think as determined is at base, not deterministic.
It's not an easy question to answer because what is deterministic (or whether anything is deterministic) depends on which interpretation of quantum mechanics is correct and we don't know which one is correct. For example, everything is deterministic in the Many Worlds interpretation, including radioactive decay, since the wave function describes all possible events. Questions about determinism are usually left to philosophers of physics nowadays so the Stanford encyclopedia of philosophy is a good starting point to read up on some of it.
plato.stanford.edu/entries/determinism-causal/
@@eastwestcoastkid
In my view
It is the instant (now) that determins reality, on the base of what is determined previously. So that the instant is not completely severaged.
By this, I do not means that the instant acts upon reality, but that it is the concrete manifestation of everything that takes place in the instant. Continously. But "free".
francoisdeletaille that is an interesting philosophy-but at base Quantum mechanics and Quantum theory hold that physical reality is not deterministic-hence the uncertainty principle.
@@eastwestcoastkid
I think we agree.
At some point, reality is determined (observed). But it remains open.
He said that hidden variables are not possible, but bells theorem says local hidden variables. Nonlocal ones can exist
Nonlocal hidden variables would not be deterministic, though. If information can travel at infinite speed, then events are determined instantaneously, not by past states.
Grande Zwiebach, recuerdo que nos metiamos unos dotitas en el lab despues de los finales
XD
XD
😂
This professor was a former student of one of the best universities in Latin America, the prestigious National University of Engineering (Peru).
He was not your average student or teacher. He is a living legend, a GENIUS.
Feel privileged to receive their knowledge in your country.
Saludos 🇵🇪
No me di cuenta de que era barton, such a precious gem of our country. It's a delight hearing his class
Si bien la UNI es una de las más díficiles de ingresar en el Perú, no es una de las mejores universidades de Latinoamérica, de hecho, en rankings de universidades, no llega al Top 60 de Latinoamérica. No es por desmerecer nada, pero las cosas como son. Y sí, el profesor es un genio.
JJAJAJAJJ prestigiosa por donde wbonazo
No exageres man, no es de la mejores de Latinoamérica pero si tiene su prestigio
Solo no es de las mejor de LATAM porque no sabe investigar seriamente con metodología real. Pero que cubran este hueco y verás como brillará frente al mundo 😎
11:00- Really true, consistent with the wisdom there are more unknown unknowns than known unknowns.
15:25- This statement makes the superposition concept a bit easier to comprehend.
Nothing he says explains to you where superposition really comes from. If I were to test you orally on that question, I could easily fail you, right now.
This professor is one of the best
just now found this by chance - he is excellent. if they make a movie about him, he would be played by Dustin Hoffman.
Dear Professor, As a prof myself and now your student, I realized there is life into those mathematical equations
Wow !...A professor who writes cursively ! 🎊🎉🎊
Puedes poner subtítulos en español por favor, me interesa mucho el material y quiero aprender.
Saludos
Learn English !
Y lo peor es que el profe es peruano y por lo tanto habla español
Looks like Harisson Ford
After the lecture he's going off to fight Nazis and discover stuff
Thats Harrison ford doing an accent
La leyenda de la UNI-PERU , Barton Zwiebach👏🏻👏🏻👏🏻
thank you MIT, thank you sir, and thanks to whole staff there.
Doesn't Bell's inequality say that no LOCAL hidden variables can satisfy quantum physics meaning that NON-LOCAL hidden variables could satisfy it?
Polarizers are not filters, they are re-radiators. Imagine two antennas connected by a coaxial cable. The interfaces between glass and air are the antennas and the glass is the coax. Light impinges the front face, just as an antenna. If the antenna's polarization matches, the light enters the glass, propagates and exits according to the polarization of the back face (antenna) of the glass. Using this correct model of a polarizer explains polarization completely and without mystery. Bell's Theorem is not required, only Maxwell's equations.
Can you give me any reference (book or article) that supports your re-radiator model of polarization. Many thanks for your insight.
Prof. Zwiebach is actually very good, but for any "not perfect English speakers", it was absolutely necessary the presence of subtitles....in English! Anyway, thank you for the lesson and greetings from Athens, Greece.
The figure in this explanation would be better if shown in three dimensions. The professor’s explanation describes a plane wave oscillating in a plane parallel to the z-axis at an angle alpha to x--z plane. Then the closer the plane of the wave gets to the x-z plane, the greater the transmission of the wave through the polarizer.
2.40??
V velocity x wavelegth = C speed of light.
F frequenxy x wavelength = v velocity.
Barton Zwiebach the genius from Perú.
14:22 Explain these sentence_ "And linearity means that if those photos can exist, the superposition can exist." And "those" stands for what?
It stands for the photons polarized along x or y.
Wow. Light starts waving at what point? My theory, however so humbled, is that light wont wave until it runs through its variance of color, atmosphere layers and was used different to assert waves. Like the energy collects some seeing alternating current but has proven its not the only current.
15:41 but it is wrong only with LOCAL HV!!! 16:11 classical = non-contextual, with the 3 components of spin pre-fixed, that is clearly wrong, knowing how spin experiments results are
Bell just showed that a HVT is non local and, if the formalism of spin is correct, that it is also contextual. Look at the interpretation of spin in the works of David Hestenes and other physicists, and contextuality desappares
Good and clear teacher. Good tempo and very to the point.. Absolutely well done and definitely keep it up!!! .
The funniest lie ever; if they cannot determine it, then the determinism is lost. The amount of grandiosity of the title of this video is ultimate; despite it appears to be super humble.
Our ability to determine is irrelevant if there are no local hidden variables. Bell's experiments prove that particles literally do not inherently contain the values needed to predict their behavior.
@@eoinlanier5508 There are no particles in nature. There are only quanta of energy. That there can be no local hidden variables follows directly from relativity. We never needed Bell for that. I would advise you to read Bell's paper. He says so himself at the end of it. ;-)
Wow, clearly explained and at a pace I can work with. Gonna be watching more of these.
What a lovely man. So calm and precise.
I remember being introduced to Imaginary numbers at school. POW. Mind blown.
Two years later in college, they're vectors. Oh. Why didn't they say that ?
On a par with year 2 maths class. Ok. Let's consider n. n is any number ! Pow. n is clearly a letter. Dropped out of the top maths class soon after.
Got back in again though. Just the whole year missed and forever holding on by my finger nails since.
Good and clear teacher. Good tempo and very to the point.
1:17 the classical notion of particle has zero size? I thought the classical notion of particle is defined as having absolute physicality hence having aspect of substance and dimension i
.e. size. This is why it is deterministic. Phenomena of light break down the classical notion of particle with its fundamental state of duality of wave n particle
So... does that mean photons are constantly changing states, (polarization but not frequency?), before they are measured, because they exist as a wave function?
Is that why when sent through one at a time all go through or none do?
Moreover, why is it that when polarized light is sent through three polarizers, at right angles to each other... some light gets through? Is it because since it is not measured, some photons in the wave state change polarization between polarizers? Then why do three allow passage but two block all light?
Plus why is it a wave function rather than a matrix of possibilities?
As far as photon/polarizer debacle: could it be that the photons are entangled in opposite spins and the spin is the deciding factor as to whether the photons goes through.
If all my teachers are this good at explain8ng, I might have turned into a professional student.
De los mejores profesores de física.
Wow, this takes me back to undergrad QM. Sets good foundation for QED. Well done professor!
Now I know what good teaching is.
This is a strange world where we know so much but are somehow missing the point completely.
Wow. The universe it truly random. Thank you.
Glad you figured out that determinism is voluntary.
Hello Dr. I am 12 years and this video was great , and I wish to be more specification and harder. Thank you
10:00 When considering a scale of the atoms, each photon incident on the polarizer seems to be a unique experiment. On that level of detail it is not a billion of equivalent experiments.
Each photon has a different path. Leading to different sequence of interactions in the material.
What do you think? Are they equivalent?
Eric Fay that’s why it’s a wave
@@elck3 localized waves, like wavelets?
Surely - when we observe light as a wave, it behaves as a wave (Polarization, diffraction, superposition), and when we observe as a particle, it behaves as such. (Photoelectric effect).
I get the feeling that you are asking the light to behave like (Commit to being) a wave and then questioning what happened to its particles...
When he says the energy is proportional to E squared, isn't there a magnetic term "B squared" to take into account ?
Brilliant and passionate exposition. His mannerisms remind me of Saul from Pi
12:46 strange gesticulations associated with wave function
Even Bell himself didn’t think that he proved the impossibility of hidden variables. Travis Norsen: in his book (titled ‘Foundations of Quantum Mechanics’) says:
“There is a kind of rich and tragic irony here, in citing Bell as having supposedly refuted hidden variables theories …, Bell’s theorem was actually inspired by Bohm’s 1952 pilot-wave theory papers, and indeed Bell remained far and away the pilot-wave theory’s greatest champion until his death in 1990.”
the clue is in the title guys - Open Course. For anyone who wants to watch. And you've got to be pretty good at your subject to explain quantum physics so that anyone can even approach understanding that!
Does anyone know what experiments he is referring to when he mentions people have ruled out the argument "It is the unknown subatomic structure of the polarizer that determines which photos pass vs are absorbed?"
quanta was energy unit measurement. if we can program photon in twisted wave guide. is there two type of frequencies minum to have light so should it be Frequency**2 ) * wavelength= speed
What if _i_ - the imaginary component of the wavefunction - is the "hidden variable" that Einstein theorized might be present for photons? I mean, it isn't unreasonable to expect the _i_ component to have _some_ physical manifestation, is it?
Now I understand
What entanglement actually means !
Extraordinary explaination
The dynamics are when photons change.. Photo..photons..reflection of crystal or diamonds...photo..is it graphic like measure? Memory or weight divided by size of reflection times exponential aspect of ...so measure the remember..no measure the distance real..by the compared carbon measure..thanks for ?? All this.
During the introduction of the polarizer on the x-axis, energy is incident on the polarizer and this energy is lets just say fractional. Remember we have already assumed em waves here. I am failing to understand the subtle transition when the professor says energy but talks about the number of photons. How does one total the energy of the field which is proportional to the square of the electric field quantified as the number of photons? If we are indeed talking about the energy of one photon itself, and that energy should be a fraction of what was incident, aren't we forgetting that this was the case with the assumption that the energy was of an em wave? In short, I guess I am having a difficulty understanding when it is the energy of the em wave and when the energy of a photon.
The total energy is just the sum of individual photon energies. The classical wave, on the other hand, is an approximation that is valid for large numbers of photons. Think if it this way: dice rolls can have outcomes 1, 2, 3, 4, 5, 6. The average of many dice rolls will be a number close to 3.5, which is not a possible outcome. Same here. The smallest individual measurements will reveal photons with discrete amounts of energy. The time averaged sum of all these measurements behaves like a classical wave.
@@lepidoptera9337 so the average energy is proportional to the square of electric field here? Also, in the Young's experiment, while sending individual photons, we observe that it is as if photons have interfered with themselves creating the interference pattern. I understand this is what we "observe". But my classical mind wants to know just why?
@@chaoticlue What we are measuring are energy, momentum, angular momentum and charge. The averages of these measurements can be described with abstract quantities like electric and magnetic field.
Interference is the absence of self-interaction. We are desperately trying to teach this in high school using wave pools and wave machines. 99.99% of all kids misunderstand the actual goal of that lesson. It is NOT trying to demonstrate interference as some "active physical mechanism". It tries to demonstrate that individual waves DO NOT interact with each other. At the photon level that means that photons do NOT interact with either each other or themselves. That's why the number of photons doesn't matter. Every photographer knows this, by the way. A scene captured on film or with a digital camera looks exactly the same, no matter if it was taken with a high intensity light source in a short amount of time or a low intensity light source during a long exposure.
@@lepidoptera9337 I was merely stating what was said in the video about "it is as if the photons have interfered with themselves" Of course the diffraction helps with the interference. And I am not disapproving of photons' absence of interaction with others (but why actually). My doubt is how to justify my classical mind that the "interference pattern" of a series of photons spewed back to back were able to give out the same pattern of a wave interference or rather wavelets interference?
I guess I am confused to the core and hence am trying to look for resources that could give me actual meaningful insights into this field instead of talking about the prestige or the magic of this science.
The method of teaching this field should also be unique is what I feel, because we've been hard wired to think classically. And even abstract examples from classical world seem highly misleading atleast to me.
@@chaoticlue The reason for the patterns is purely geometric. There is no physics in the bulk (that's what "self-interaction free" means) and therefor effects on the boundaries can only depend on the conditions on the remaining boundaries and the relative distance of boundary points from each other. We can eliminate the first dependency by using a single point source. That means that now the only "physical observable" that is left are geometric distances between the source and the detector. Because of relativity there can also be no absolute dependence, so we are basically down to geometric path differences (phase differences). I don't know if there is an easy handwaving argument to develop a good intuition for this. If there is, then I haven't heard about it.
You can learn to "see this" by staring long enough at the integrals that form the solutions in the theory. It's readily visible in the general form of Lie-groups representations (exponentials of the generators). Is that real understanding? You decide. The physics of empty space is counterintuitive because we are used to think in terms of "contact physics" where nothing happens unless some thing touches some other thing. This is the exact opposite. Whatever happens happens because absolutely nothing touches anything.
Maravilha de aula! Eu diria um pacote de fótons de aula! Parabéns!!
Just because you need a certain amount of energy to achieve a result. Does it necessarily mean that the energy is parcelled in that amount?
Energy is not quantized. Angular momentum is.
The problem is that the photon is an absorbed or bound quantity, when it's free you cannot count the bosons, so saying things like ''perhaps billions of them" is referring to a certain energy or intensity, and is still a classical line of reasoning. Yes, you can count what you can catch, but the wave function occupies the whole Hamiltonian state space between t0 and t1. Indeed when a radiation source emits at a given frequency and amplitude, everything is determined, N bosons doesn't factor anywhere. When you divide up the radiation's amplitude by Planck's constant, you regain your frequency, not N ''photons''.
is water also a wave-particle duality?
water in Sea and ocens is wave , water coming out of Tap in form of droplets is particle
There is no wave-particle duality. That's just a nonsensical term from the great confusion phase of quantum mechanics. There are uncertainty relations and they also apply to waves on the ocean. They simply have nothing to do with quantum mechanics. They are properties of certain linear operators over function spaces... every theoretical description that has them has uncertainty. Acoustics, seismology, water waves... doesn't matter.
@@schmetterling4477 ..😀. then the question comes, what are subatomic particles made of? are "electrons", "protons", "neutrons" , solids, liquids, gases or what state they are?
@@nickharrison3748 There are no subatomic particles. We are teaching in high school that a photon is the amount of energy that gets emitted into or absorbed from the electromagnetic field. Energy is not a thing. It's a property. Every time somebody talks about "particles", all they really mean is energy flow from one system to another. This is simply a matter of poor language choices that have been confusing minds for the last 100 years.
@@schmetterling4477 ..sure..I try to understand what you are meaning. yes, photons are just energy or forces or disturbances in EM field. so, you mean, all subatomic particles are just disturbances in their respective "fields". every particle has its own "field". field is the medium. so water is in its own "ocean" or sea field.
@@nickharrison3748 There is not even a disturbance. That's just your mind hanging on to classical concepts that don't exist on the quantum level. Take a piece of spacetime. Divide into two sections. On has more energy than the other, then that energy can flow from one to the other. The smallest possible energy flow of that kind is a quantum. That's it.
How would polarizer work on the moon... example... Why astronauts didn't see their own foot in the shadow area?how light can be curved by gravity. photons don't have mass( just energy)? Influence of atmosphere?? Complex....
12:35 If its probability then we should get the random result every time. How we get the fixed outcome every time ((cos alpha)^2) ?
It's random which photon will get passed through, the total percentage of photons passing is not random
The notion of photons and their relationship to determinism invites intriguing questions about the fundamental nature of reality. Photons, as quanta of light, exhibit behaviors that can appear inherently probabilistic, particularly when analyzed through the lens of quantum mechanics. The famous double-slit experiment demonstrates that photons can behave as both particles and waves, exhibiting interference patterns that suggest an underlying randomness to their behavior. This challenges classical notions of determinism, which hold that future states of a system can be precisely predicted given complete knowledge of its initial conditions. Instead, the behavior of photons often embodies unpredictability, highlighting a universe where inherent uncertainty reigns, thereby prompting deeper philosophical inquiries into the fabric of reality and whether determinism can truly coexist with the principles governing quantum mechanics.
Photons aren't probabilistic and they are neither waves nor particles. These are all just nonsensical statements that are caused by shoddy thinking.
But what if the polarizer inside has some frequency of reaction states to light going through? In some states it allows the photon go through, in another doesn't. No need in probability.
"frequency of interaction " same as probability
Increíble un ilustre Peruano haciendo patria en el extranjero.
From Rene (Decartes)'s Materialism to Russell (Bertrand)'s Mechanicalism..our view on the Materialistic world was profound and set forth every Rational Aspect of our understanding. So we call the elementary ingredients study, the PARTICLEs Physics, due to Democritus 's undividable Atoms (though later we found many "p" are much smaller than 'P'). Light is particle called Photon, electric is classified as lepton, 900 times smaller than Proton (Neutron). Even binding Energy we considered them as Gluons-exchanged ? And same as gravity, forcefully we try to MAKE such Interaction as GRAVITON exchange process, another kind of tiny(minute) PARTICLE as well. All were found by materialistic view of the universe, Interacted together with some deterministic MECHANISM, either exact or by STATISTICS (that You consider it UNdeterministic.)
I don't buy the particle simply moving in wave
It's an estimation of a particle Thet is light weight...gets hit all over the place...
Looks like a wave as an average.
We have to find the particle where how it exists
Oh but what Happened to the Particle at Polisation ?.
Particles have Mass ?.
Tricky ?.
Not all classical hidden variables lead to a non violation of the Bell Inequality--just the very limited and narrow set considered by Bell.
I would suggest you actually read Bell's paper. All of it. The kicker is at the very end. ;-)
@@lepidoptera9337 i read it. It's garbage and really has no value whatsoever. It's incomplete and not accurate.
@@bustercam199 So what does it say at the end? ;-)
@@lepidoptera9337 it does not matter as the Bell inequality is both incomplete and inaccurate. Bell was more of a philosopher and not so much a physicist.
@@bustercam199 Reading the original publication that you are talking about does matter, because if you didn't actually read it then I won't take you seriously. I will instead treat you like a troll. Would you like some more attention with that? ;-)
Why do light waves pass through glass window but not a wall, does wall behave like polarizer. And sound waves penetrate everything?
Sound penetrates a vacuum? Somebody didn't pay attention in high school. ;-)
Perhaps A new type of individual “determinism” emerges as an observer concentrates with dedication and energy, and on a result, turning a probability into a specific intentional personal outcome. Focused Thought with passion and energy, eventually creates through photons, light, what the observer concentrates on, with energy. Perhaps this points to the possibility of the hidden variable theory harmonizing with our participation making a phenomenon complete …with a result we intentionally zero in on.
Merveilleux cours de physique ! Merci de partager toutes ces explications si claires 👍
I want everyone to pronounce photons as he does.