Dear Dibyajyoti Das: I expanded my comment eight days ago into a full paper with six substantial figures and five references. The first figure is your blackboard, and four of the remaining figures are based on it, with increasing levels of modification and adaptation to extend Feynman’s original thought experiment to the issue of precisely what we mean when we say “particle” in quantum mechanics. I do not know if your RU-vid comments permit direct links to non-commercial, strictly CC BY 4.0 websites -- it varies from site to site -- but I’ll try it below [1]. If it doesn’t work, I’ll try adding a non-link comment. Thanks again for this presentation. You may be surprised how much analysis came out of the simple issue of where, precisely, both you and Feynman placed the light relative to the double slits. Sincerely, Terry Bollinger -------------------- [1] T. Bollinger, _The Particle Illusion: A Closer Look at Feynman’s Double-Slit Paradox,_ Apabistia Notes (2023-07-12). sarxiv.org/apa.2023-07-12.1720.pdf
That is a really brilliant paper ,so you think particles interaction with its surroundings is the reason why it behaves like a particle or a more sharper wavefront appearing as particle
@@nuthakantirohan4685thanks. Yes on the earlier question about environments defining particle-like trajectories. On this sevond question, yes again; the location of a motionless particle also follows Schrödinger’s equation, and thus expands in space until “bumped” by some other particle. This is required by special relativity since that same particle behaves like a particle in motion to a moving observer.
Hey bud. I already have a masters degree in Astrophysics but I have some random physics instructional videos playing in the background while I work on this paper just to see if someone has a different perspective that I've never considered, and I have to say you make some of the best physics videos I've seen. It's difficult to find the middle ground between _'I need everyone to know I have a PhD'_ vernacular and going over subjects like you're talking to a child (or an American adult), but you do a great job of that. Your videos make me think of a kid I worked with just before I graduated that was just starting his freshman year as a Physics major. If I knew him now I'd definitely recommend your channel. Keep up the great work!
Thank you! This is a beautiful and scrupulously correct presentation of the same points made by Richard Feynman in his Lectures. One correction, which Feynman seemed to understand but did not emphasize: The particle Case 1 and the watch-the-slit Case 4 do _not_ give identical physics at all, just deceptively similar profiles in the case of a single screen. The difference is that if, in Case 1, if you place you replace the final screen with a diffraction grating, the particles stay particles and randomly bounce off of the grating. In sharp contrast, if you replace the Case 4 screen with a diffraction grating, you get sharp diffraction patterns showing that the electron is even _more_ wave-like -- more coherent -- than before it went through the single slit. In the decades before lasers, that was how they _made_ coherent light: By squeezing them through a narrow hole, photons emerge as hemispherical waves on the other side. The situation is similar for electrons. I wish Feynman had explained this point better. He clearly knew it from his other examples. However, in his effort to make the examples more understandable, he got a bit too casual about mixing up the classical and quantum concepts of randomness. Incredibly massive bullets are never quantum before or after touching the hole. In contrast, the extremely light electrons navigate the hole as waves and stay quantum throughout the journey. The physics is very different in these two cases, and, uncharacteristically, Feynman skipped over explaining the differences. Finally, those sand images, alas, are again mixing issues. _Isolated_ sand grains drop straight through a hole, forming an extremely narrow distribution resembling a Dirac delta function. The smooth piles that mimic normal distributions are due almost entirely to post-fall bouncing and avalanching of colliding sand grains, and that has nothing to do with _either_ particles or waves propagating through a slit. I understand the visual appeal of such piles, but they confuse folks rather than explain the details of what happens in the very-heavy particle cases.
Das' choice of words bothers me. He says that "you look" at a particle when a more realistic description would be "when you TOUCH a particle". You basically smother a small wave with a very big one.
@@mirceadinu46, unfortunately, the terminology for quantum observation has been vague for over a century. One simple trick is this: Does the interaction create an action-reaction momentum pair - that is, are both the observed wave and the wave of some probe redirected a bit? If so, _both_ will, from that point forward, behave as if they had “planned” that specific encounter at that granularity since the moment they set out on their collision paths. For example, if the sun emits a photon that nominally spreads out over half the solar system but instead encounters a space probe light sail (mirror) covering 10 square meters of space, all of the history data you can collect will tell you the same thing: The photon behaved as if it had aimed directly at the light sail, hitting all of its surface and nothing else, no matter how complex the geometry of the mirror may be. The photon then reflects in the opposite direction, shaped and guided by the form of that mirror. Simultaneously, it generates a tiny burst of momentum - half of an action-reaction momentum pair - deposited smoothly over the entire mirror surface rather than being localized to any one point or atom in the mirror. The reflection event counts as a detection because a photon that would have traveled outward over half the solar system instead lands on an incredibly tiny 10 square meter area from which it then begins its travels anew in the opposite direction. The detection is real because the momentum given to the mirror creates an irreversible historical record that cannot be changed without violating causality. Notice that I never used the phrase “wave collapse.” A better phrase would be “history customization” since once the photon is reflected, it behaves like the wave never had any other intention except to go directly and precisely to the entire mirror. None of this makes sense in terms of our classical concepts of how history works. As I've liked telling folks for many years, quantum mechanics is the physics of histories that have not yet been defined.
I had a similar experience in my youth. My dad (retired EE professor) showed me the time dilation eq and how time slows down as v -> C. My mind was blown, here I thought time was the same for everyone. For a while I couldn’t stop reading about Physics and of course, eventually lead me to Brief History of Time, Modern Physics and even the Philosophical Tao of Physics and a subscription to QM magazine. I ended up in Engineering and part time Flight Instructor, but my wife often asks me “Why didn’t you become a Physicist?” 🤔.
Wow wow wow …. What a lecture ❤️ hats off to you sir. I don’t have words to express what i am feeling for this lecture. Any level of love and respect is not sufficient for this lecture…. I am also a physics teacher. Have taught this topic to students of school and college as well. But your patience and brilliant way of teaching this topic made my day🙏🏻
Professor, I would like to congratulate you and all of India for landing on the moon ! ... And thank you for all the great work, keep it up ! Greetings and Love from Morocco ! ❤🇮🇳❤🇮🇳
As a retired physics teacher I greatly admire your enthusiasm and description of a phenomenon which is baffling the finest scientific minds. The apparatus is deceptively simple and yet the explanation of the results seems to challenge our present ideas of space and time. Just as Einstein shed light on the Photoelectric Effect, so opening our eyes on to the quantum world, hopefully a future genius might clarify the Double Slit experiment to reveal a new level of understanding. Thank you, sir, for your excellent presentation and please accept my very best wishes.
The larger particles like sand grains will also pass through 2 slits at the same time "if" you can design the slits to be the right calculated size apart from each other. Using DeBroglie's equation the wavelength of a comparative large particle like sand grain compared to an electron is calculated to be several orders of magnitude smaller. So small in fact that designing a double slit for a particle with such a small wavelength is physically impossible. The double slit experiment was demonstrated for not just electrons but even for atoms and smaller molecules, but the slit separation for atoms and molecules is very small to match their smaller wavelength and while difficult to fabricate, is doable. Anyone can build and demonstrate the double slit experiment for light, but for the tiny slit separation for electron and atoms will require non-trivial fabrication and setup.
I have no words sir literally awesome video... I wish sir each and every student will know the physics you do explain sir .... The way you teach the way you show the way you express the way you want us to think these all thing are just practical and amazing ❤
Since 2021 there is a way to understand it. The clue is not to think as one entity that develops two antagonist roles; but as two entities that coexist. As the phrase "stuff in a media", in this experiment, the "stuff" is the compact particle, and the "media" is its quantum space. Yes, a wavy space that oscillates between the observable 3D and the 4th dimension. So, the particle will be in 3D meanwhile Its quantum space is in 3D. With this, the experiment is understandable, a space that can be divided and interfere with itself. You can read more about this new interpretation in the book "Can Relativity and quantum mechanics go together?" hope you get inspired, regards
Thankyou so my sir💞it should be watched by more people. Why are everyone not discussing these mindblowing topics, we should popularise it. Sir does the electrons passing through slit interact with electrons inside the slit materials did that can be a reason
I like your videos very much. Can you make videos on operators in quantum physics for first timers and then continue till quantum mechanics of Hydrogen atom please?
Sir,Thank you so much for this Lecture. You are really a super hero who can give pure knowledge of physics for the physics major students. I am Very much greatful you sir, From Bangladesh.
Just so we’re clear, the double slit experiment preceded Heisenberg’s uncertainty principle and everything else you mentioned because it is all based on this result rather than preceding it or independent of it. For all the hem-hawing over it, physicists still have yet to quantify the effect. Without quantifying it, it has no different classification than sorcery and rainbow unicorns (in the sense of having no scientific explanation). We don’t understand it, so instead of treating it like wizardry, gawking at it in awe, we should be viewing it like an as yet unopened black box that needs a proper mathematical explanation.
I think the electron is not necessary a wave but is so lite that wen is fired through the slits is not going straight. It interferes with the air particles before the slit , in a way that it hit the inside soffit of the slit multiple times and pass through to make what is so called wave pattern.
quantum phenomena behave between classical system,let take example that when electron reach near slits then these slits and electron behave as a quantum system like same concept of schrodingers cat experiement,so there is a possiblity that electron will pass 50% from slit one and 50% from slit number two but when you put detector it behave classical just like when you open box to see if cat is alive or dead.Amazing how you explaining complex stuff👍👏.
I'm in class 11, I just love physics I want to give physics olympiad next year and I found the questions in it are though difficult and also from modern physics ( Quantum mechanics ) so I also want to understand it so what should my road map for learning quantum mechanics along with classical mechanics syllabus?
Please continue your series sir you are going very slow please try to cover the syllabus to intermediate level in this year By the way lectures are very interesting and useful ❤️
Your good teaching could include another point (better you have escape) that is with mass and massless particle . That is equations are for mass less identity no gravity in action. This is the problem of Physics in advance. Thank you for good video.
32:48 - If the source can emit exactly 1 photon/electron at a time, then if we replace s1, s2 with 2 in-sync sources.. wonder what pattern forms on screen. vis a vis when you observe the electron's trajectories
How we can find trajectory of single elctron (path S1 or S2 )with disturbing interference patterns?? And how we can disturb interference patterns?? Dir please explain...
When you try to detect the slit through which the electron passes through (thereby knowing it's trajectory) the interference pattern vanishes, & vice versa.
Sir in case 3 koi na koi tho researcher hoga jisne ye experiment perform kia hoga then unki eyes ne detector ka kaam ku nhi kia fir interference patterns observe hi nhi hoga??
Oh, you said that a single electron "goes through ONE OF THE SLITS." That's not right - that implies the electron followed a well-defined trajectory. You can't think of it as having a well-defined position vs. time at that state - you have to just consider it's wave function, which obviously goes through both slits. Note - it's not THE ELECTRON going through both slits - it's an electron's WAVE FUNCTION. You don't have a well-defined electron at a precise position until you see that spot on the screen. The single electron at a time version of the experiment isn't mind blowing at all once you accept the above. You just have to stop thinking of the electron as something that is always a "small little pellet." That just turns out not to be how nature works. It can SOMETIMES BEHAVE like a small little pellet, but most of the time it doesn't. In particular, it does when it makes a flash on the screen. That's really the "weird" part of the experiment, if anything is - up to then you just have a wave being a wave, but somehow it instantaneously transforms into a small little pellet and gives us a flash. That's the almost magical part.
Sir I have one confusion When we got band like pattren from electron ( without detector) how can we conclude from that, the electron passes through both of the slits at the same time??? Sir please can you re-explain this briefly
when u r bombarding one electron at a time the experimental setup remains the same for each of the electrons...but we get the interference pattern...so it means that the electron might get passed through both of the slits... otherwise if u think classically each electron should hit the same spot and there will be no interference pattern..u will then find a dark spot at a particular place..but it's not like that..u get interference pattern....please rectify if I'm wrong...
The duality is real and mysterious. Completely illogical on its own. But that's where we start to question logic. A+B=C. Not always. Always has lent to the question of what are the unknown unknowns? Kindly, the universe makes it particularly hard to even try to answer that question. What really bakes my noodle is just how fast particles are going. Even air at normal temperature and pressure. The molecules around us are racing at over 700km/h all the time.
If we know, how general relativity work at quantum level, we can explain interference phenomenon for single electron. And also we can prove electron is exactly particle without confusion. But problem is that,we don't know how general relativity work at quantum level. And thanks sir,for your dedication towards physics ,it inspired me lot of. One day I want to become lecture like you sir thank you.
Hello Sir, in experiment 4, with the detector, 1) do we see two Lines I1 and I2 or one line I? Most double slit videos shows two lines as if each slit corresponds/collapse into its own one line on the wall. Can you clarify this point. 2) Also what is the distance between the slits? Will the distance between the slits make any difference. Say we start with a experiment where we see interference pattern and then we move the slits slowly apart, at what point the interference will disappear and you now end up seeings two separate lines on the wall.
It will depend on the distance between both slits. In Exp 4, if both slits are sufficient distance apart, we get two lines, (ideally speaking it should be two lines) but I assumed sand/grain particles initially so both merge into one if slits are close enough (which is what I assumed)
In general, for there to be no interference, the individual single slit spread of each slit must be distinct (happens at large distance between slits) for waves
@@FortheLoveofPhysics Dude... interference is the absence of self-interaction in linear systems. That doesn't depend on the slit size. At most the necessary coherence conditions for distinct maxima and minima are not met.
The problem here is that we insist on starting our kids out by teaching them that subatomic entities are PARTICLES. Then it's no wonder their "minds are blown" when the eventually get to this. We should teach them RIGHT FROM THE START that how subatomic entities behave depends on how we interact with them. We don't have to teach them quantum theory, but we still could "prepare them properly," and then when it came time to learn quantum theory they wouldn't be shocked and surprised. This is the fault of our teaching program.
@@lepidoptera9337 I think the implications of it should be underscored, though - it should be said explicitly and out loud that as a consequence of this, all of the equations that the students are about to learn are approximations only. Very good ones, but approximations nonetheless riding on top of a non-deterministic froth of quantum uncertainty. That nature IS NON-DETERMINISTIC. And if they say that and people still don't get it, well, I guess you're right.
@@KipIngram That is exactly right. Non-determinism is not an approximation. It is an actual hard feature of relativistic spacetime. It's that already in the classical approach to the question. Why? Because in a relativistic universe energy always comes at us at the speed of light, which means that nature can not and will not give us a "Heads up, there is a gamma ray coming!". The moment that gamma ray registers in our Geiger-Mueller counter is the first moment that we and the universe can possibly know about it. It is locally completely unpredictable. That is also the reason why there can be no local hidden variables. The energy of future detection events won't come from anything local. It will come from sources that are currently residing in spacelike-separated regions of the universe. No, in my experience people, including many physicists, really don't get this. The learning units about energy, the definition of quanta and an introduction to special relativity have to be included in the high school curriculum way, way earlier, before students' minds are settling on a non-existent deterministic universe that was nothing other than a failed idea of the 18th and 19th centuries.
@@lepidoptera9337 That's quite interesting; things for me to think about. On a different but related note, what is your opinion of geometric algebra / Clifford algebra? I only discovered it a couple of years ago, and actually felt anger that it wasn't taught to me very early on - it seems thoroughly superior to the traditional approach to so many things, and it "unifies" those things under a common umbrella, which is always a good thing if your goal is to learn a lot. I think it's basic "rules" are simple enough that you could begin that training as soon as kids had algebra under their belt. It also completely dodges the restriction of the cross product to three dimensions (we fudge and use it in 2D problems too, but that really is kind of a cheat mathematically).
@@KipIngram I am a retired experimentalist and my math is, at this point, non-existent. I would agree, though, that the way we are approaching math in school, even at the middle school level, is outdated. We are still teaching a 19th century "Euclid is one thing-algebra another" program. Geometry and algebra are obviously not separate. They seem to be extremely close, actually, and the mathematicians are fully embracing that (partly thanks to modern physics, I believe). I never understood why we are doing the symmetry/dimensionality thing in baby steps in the physics curriculum. The theory is fully developed and tensors/linear forms/matrices can be taught in the two and three dimensional example in high school, already. What stops a high school student from learning about the concept of a determinant in the two dimensional case and three dimensional case while also understanding that a matrix has a geometric meaning as a rotation/scaling operation? Is it that hard to remember the cross product as a skew-symmetric matrix? And, yes, since we are at it, we might as well discuss complex number and quaternions and show students how to use them in physics and how all of this is organically related. The entire first semester math catch-up thing in university has to move down to the last year in high school, maybe even earlier. I am not an educator, but it seems to me that we are probably also wasting one of the best learning years of a kid by taking them to elementary school too late. Most children (of parents who can afford it) can be (and now are being) taught basic math, simple geometry, reading etc. in kindergarten. My understanding is that a playful approach to these things will work for most kids, at least if we go by early learning programs in the mold of Sesame Street and its many international equivalents. I even learned my calculus at home from a tv program for adults who wanted to get a high school diploma three years before it was taught to me in high school. I basically had to sit through two years of boredom in math class because I knew all the material already. I really didn't hit my mathematical limits until third year in university (and I really, really suck at higher math), which means that most people who are taking science could easily deal with an accelerated program. There are, of course, kids who are not going to do well with these accelerated study programs. The challenge is to give those kids an education that makes better use of their talents, whether that's art, sports or hands-on work like machining. A kid doesn't really care about what it is that they are good at (and neither should parents). What kids suffer from is being forced to do things they are not good at and then being told that they are losers if they don't succeed in front of the entire class. That is psychological abuse, but that is exactly what the one size fits all education model does. No, one size doesn't fit all. Some kids are good at one thing, some are good at something else and those who aren't good at anything or just need a little longer still deserve an education that doesn't rub it into their faces all day long.
String Theory was not a waste of time. Geometry is the key to Math and Physics. What if we describe subatomic particles as spatial curvature, instead of trying to describe General Relativity as being mediated by particles? Quantum Entangled Twisted Tubules: "A theory that you can't explain to a bartender is probably no damn good." Ernest Rutherford The following is meant to be a generalized framework for an extension of Kaluza-Klein Theory. Does it agree with the “Twistor Theory” of Roger Penrose? During the early history of mankind, the twisting of fibers was used to produce thread, and this thread was used to produce fabrics. The twist of the thread is locked up within these fabrics. Is matter made up of twisted 3D-4D structures which store spatial curvature that we describe as “particles"? Are the twist cycles the "quanta" of Quantum Mechanics? When we draw a sine wave on a blackboard, we are representing spatial curvature. Does a photon transfer spatial curvature from one location to another? Wrap a piece of wire around a pencil and it can produce a 3D coil of wire, much like a spring. When viewed from the side it can look like a two-dimensional sine wave. You could coil the wire with either a right-hand twist, or with a left-hand twist. Could Planck's Constant be proportional to the twist cycles. A photon with a higher frequency has more energy. ( E=hf, More spatial curvature as the frequency increases = more Energy ). What if gluons are actually made up of these twisted tubes which become entangled with other tubes to produce quarks. (In the same way twisted electrical extension cords can become entangled.) Therefore, the gluons are a part of the quarks. Quarks cannot exist without gluons, and vice-versa. Mesons are made up of two entangled tubes (Quarks/Gluons), while protons and neutrons would be made up of three entangled tubes. (Quarks/Gluons) The "Color Force" would be related to the XYZ coordinates (orientation) of entanglement. "Asymptotic Freedom", and "flux tubes" are logically based on this concept. The Dirac “belt trick” also reveals the concept of twist in the ½ spin of subatomic particles. If each twist cycle is proportional to h, we have identified the source of Quantum Mechanics as a consequence twist cycle geometry. Modern physicists say the Strong Force is mediated by a constant exchange of Mesons. The diagrams produced by some modern physicists actually represent the Strong Force like a spring connecting the two quarks. Asymptotic Freedom acts like real springs. Their drawing is actually more correct than their theory and matches perfectly to what I am saying in this model. You cannot separate the Gluons from the Quarks because they are a part of the same thing. The Quarks are the places where the Gluons are entangled with each other. Neutrinos would be made up of a twisted torus (like a twisted donut) within this model. Gravity is a result of a very small curvature imbalance within atoms. (This is why the force of gravity is so small.) Instead of attempting to explain matter as "particles", this concept attempts to explain matter more in the manner of our current understanding of the space-time curvature of gravity. If an electron has qualities of both a particle and a wave, it cannot be either one. It must be something else. Therefore, a "particle" is actually a structure which stores spatial curvature. Can an electron-positron pair (which are made up of opposite directions of twist) annihilate each other by unwinding into each other producing Gamma Ray photons? Does an electron travel through space like a threaded nut traveling down a threaded rod, with each twist cycle proportional to Planck’s Constant? Does it wind up on one end, while unwinding on the other end? Is this related to the Higgs field? Does this help explain the strange ½ spin of many subatomic particles? Does the 720 degree rotation of a 1/2 spin particle require at least one extra dimension? Alpha decay occurs when the two protons and two neutrons (which are bound together by entangled tubes), become un-entangled from the rest of the nucleons . Beta decay occurs when the tube of a down quark/gluon in a neutron becomes overtwisted and breaks producing a twisted torus (neutrino) and an up quark, and the ejected electron. The phenomenon of Supercoiling involving twist and writhe cycles may reveal how overtwisted quarks can produce these new particles. The conversion of twists into writhes, and vice-versa, is an interesting process. Gamma photons are produced when a tube unwinds producing electromagnetic waves. >>>>>>>>>>>>>>>>>>>>>> Within this model a black hole could represent a quantum of gravity, because it is one cycle of spatial gravitational curvature. Therefore, instead of a graviton being a subatomic particle it could be considered to be a black hole. The overall gravitational attraction would be caused by a very tiny curvature imbalance within atoms. We know there is an unequal distribution of electrical charge within each atom because the positive charge is concentrated within the nucleus, even though the overall electrical charge of the atom is balanced by equal positive and negative charge. >>>>>>>>>>>>>>>>>>>>>> In this model Alpha equals the compactification ratio of approximately 1/137 within the twistor cone. 1= Hypertubule diameter at 4D interface 137= Cone’s larger end diameter at 3D interface where the photons are absorbed or emitted. The 4D twisted Hypertubule gets longer or shorter as twisting or untwisting occurs. (720 degrees per twist cycle.) >>>>>>>>>>>>>>>>>>>>>>> How many neutrinos are left over from the Big Bang? They have a small mass, but they could be very large in number. Could this help explain Dark Matter?
You've used the phrase "amplitudes get added up" a couple of times - I think that's potentially misleading - most people think of the "amplitude" as the coefficient out before the sin() or cos() term. Of course you are probably meaning "probability amplitude," but some people might still be confused. The only thing you can add as real numbers is the instantaneous value of the waves, with the sin() or cos() factor evaluated at that time and place. The probability amplitudes, on the other hand, are complex numbers rather similar to the "phasors" studied in electrical engineering, and you can add them so long as you add them as complex numbers.
Feynman wasn't ENTIRELY right - the double slit experiment doesn't give us anything to do with entanglement, and that is a fundamental important part of quantum theory too.
@@FortheLoveofPhysics Thank you and please remain patient Mr Das. This is turning out to be the best and most complete lecture series on QM. We don't need another 13 minute video trying to explain all the complexities of quantum entanglement in one go on youtube. We need a quality and robust QM series and this is shaping up to be just that
The project of understanding the double slit and quantum mechanics, has virtually been given up on. Science might need to cross pollinate with theological understanding to resolve their dilemma. Hand in hand, religion and science must possibly walk. The understanding of reality & the double slit has been stagnant now for 100 years, Solving the riddle of the double slit will likely need the assistance of Theology and Philosophy. Strict science will possibly never break open the understanding alone. Could if be a need to involve the Priest-scientists who can help access Tesla type knowledge, and the harvesting energy from zero point. with ignorance to solve the puzzle. We only have 5 physical senses with which to observe this 3 dimensional realty we live in. 1) sight, 2) smell, 3) taste, 4) hearing, and 5) touch. With our eyes open, we immediately observe the visible spectrum, and the 3 dimensional world in which we find ourselves, manifesting the single particle reality. With our eyes closed, the invisible spectrum of potentiality (interference pattern) possibly exists. This is much like the meditative state that monks seek. They are seemingly seeking connection with the (Ultimate) unified field. There are multiple realities possible, when we are not observing the play of existence. So why do we humans argue about veracity? Which possibility is the most true, or are all equal depending on ones belief system or vantage point? How many realities are there. The wisdom traditions from across the planet suggest there are more than one. Science would benefit by allowing such thought to be considered. If consciousness is truly vital to manifestation, all doors should be opened. Lets collaborate folks!!!
If you love physic . You are a prisoner of uncertainties and unexplained phonemons of quantum physic. Your brain 🧠 runs out of fuel often. You feel yourself lost while everyone lives their life around you.
