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- เผยแพร่เมื่อ 30 ก.ย. 2024
- All parts of the lectures can be found in this playlist
• Quantum Mechanical Vie...
Richard Feynman discusses Quantum Mechanics in a workshop at Esalen. Topics are: Heisenberg's uncertainty principle, Bell's theorem and the Einstein-Podolsky-Rosen paradox.
I decided to upload this workshop, because I could not find it youtube. I think everybody should have the pleasure of experiencing Feynman's teaching, even if you cannot afford the DVDs.
I DO NOT OWN THIS MATERIAL. IF IT VIOLATES COPYRIGHT OR SOMETHING LIKE THAT, I WILL REMOVE IT IF I AM NOTIFIED OF SUCH A VIOLATION.
As I listen to these talks, it becomes very apparent as to how hard Feynman worked to teach and how big the gap was between his knowledge and the students knowledge of that era. I sometimes forget how new all of this was back in the day to those students.
Really it's amazing that a layman can actually watch this and know what he's talking about because of all the cool TH-cam videos he's watched on the subject. At least from a basic view. Wish I had TH-cam when I was in school.
Quantum effects are on such a small scale that the energy transfer when making a measurement changes the state of the thing being measured . Like if there were some plastic ducks on water and you measured their position by throwing tennis balls at them, after you took the measurement the position of the duck would change or the speed would also be different. This is why you cannot measure the speed and position at the same time. Hope this helps.
indeed, but why did this take so long for the hearing crowd to get it, cause they were thinking in different perspectives , what if CHAOS
This seems almost true, but you could accurately measure the distance to an arbitrary degree of precision. You could measure the position over and over again, and always, at every point in time be very sure of the positions. But what you can not be sure of is the trajectory. Because each time you measure the position of the system, say at every instance, you are, at every instance, changing its momentum. So the positions that you measure at each point in the system are going to appear very arbitrary, even though you are allowed to know them with perfect precision. So you could throw tennis balls at the ducks, and for each tennis ball that is deflected to you, you could be very sure, that, ah! there is a duck there. But ask me where the duck will be during the next measurement, and I'm quite lost, as whatever direction the duck was swimming is now certainly not what it was when I hit it with a tennis ball.
@@sancrtr ⁹
Another "chicken in the ice box" example is a refrigerator light.
As a kid I wondered why the light was always on. Every time I opened the door to "check the light" it was on. It was only after getting curious and fiddling with the fridge I discovered there was a spring-mounted switch and that the light was actually off when the door was closed. I was the one turning the light on by "observing" it! My observation was altering the state of the light.
act of checking or the act of measurement :P
18:00 audio edit...I bet Richard's response to the rude interrupter was not "fit for our ears"
its painful to see the guys don't seem to get what he is trying say but I like their persistence and the patience of Feynman. Gives a great insight in to his teaching style and teaching in general in older times. Classic!
It's like they are frustrated about the assumptions they have about the implications of a simple logic circuit presented as a stepping stone to the a difficult concept without even trying to understand the logic of the basic teaching analog.
I love Feynman, but his simplification was unnecessarily contrived. Not very explanatory.
Anyone who argues with Feynman about QM is going to have a bad day.
Thus, you experiment that measures the two/five die sides "reset" the one/six side. This process is essentially what is going on. The result comes out of the mathematical structure in quantum mechanics and is independent of how the measurement is done.
I can understand how particular, physical methods of measurement could effect the results of other measurements. What I'm having a hard time understanding is how measurement in the *abstract* could possible influence other measurements. Are we saying that no matter the physical method of taking a measurement, we will always have this uncertainty? If so, then I really don't understand.
Some aspects of a system can be successively measured without screwing up the preceding measurement of other aspects, then you could say they are compatible. But the pair of velocity and position don’t belong in this category. There you really can’t avoid screwing things up. Your trial at acquiring the Position Information gives the system an unpredictable kick. And this kick is the stronger, the more precise you are trying to nail the position of the particle down (measure it).
Yes, no matter the method of taking the measurement, you will have the uncertainty. It is abstract/intrinsic.
Thank you so much for sharing these wonderful lectures, helberg. It's like manna from heaven.
That was a sneaky watch check 24:29
I love him.....he's so great!
Only u divert the measure ,measurement😊
The way I see Feynman is he is the best vehicle for dummies like me to see how the smartest guys on the planet work and think about things. A great communicator and original thinker.
By "simultaneously" he meant you can't determine (back to back) the position of a particle and its momentum because if you keep on doing so, you'll always get your previous calculation disturbed.
By the time i'am reading your comment y'ure not the same
I am all for asking questions, but after the lecture. As you see on the tapes, he tells 2 people that he will get to those subjects. As a professor, I have found it very frustrating and distracting when people ask questions during a lecture. There is always a discussion and question/ answer time. All I'm trying to say.
true, but we tend to forget or get to think on something else, hence the tendency to ask in the middle
I believe the issue is more of an etiquette issue than just asking questions. I have had concepts clarified by a question asked during a lecture, whether from me or another audience member. However, there has to be a balance and there is a better way to go about asking questions during a lecture than other ways. Perhaps lecture etiquette should be taught. For instance, ask a question as succinctly as possible, pose it only in 2 ways, if the presenter can not answer or you are still confused tell the lecturer you will think about and ask after. Per sub topic during the lecture, perhaps only 1 or 2 are allowed to ask unless the presenter finds that further questioning will enhance comprehension. Thus if you are not first or second to ask a question at a particular moment then you should wait till the end. Being aware of the type of question you have is also important. Many people ask questions not to get clarification but perhaps to contest the lecturer or demonstrate personal knowledge. This is abhorrent behavior and I believe lecturers have the right to say to the person, no more comments of this nature, talk to me after if you want. I think quick questions regarding simple clarification can be helpful, but must only be posed once the lecturer has finished the sub topic and is moving on. Lecture etiquette is important and surprisingly it is something never mentioned or taught.
Excellent comment.
9:40 -- Many comments drawing attention to Feynman's feet, but none talking about how they give away how much or how little he's agitated, I think...
ahahahahahahah so true i love that
No it can be undone
he has wrong example. not light becomes red, but finger. And then you press next button with that red finger.
We could have done without the questions. The added nothing but interruptions.
It does, actually, in my opinion, add something. None of those who attend "speak" the same language. They all think differently, all have different backgrounds. And Feynman, as any teacher would do, is attempting to find a common language to them all. That never works as well as expected, not matter how hard you try and refine your method. Some things are said too fast for some, too slow for others, for instance. And their questions give some insight on what kind of software their brain run when attempting to understand these new and mysterious concepts. It tells us where the edges of Feynman's explanations were too rough for some.
I have come to despise teachers who say "please keep your questions until the end". Because someone who would have required, at some specific point, a small precision, who may even unknowingly have intervened not only for himself but for all the silent ones who dared not ask the same question, well... that someone, along with all the silent ones, had he not been allowed to ask, would have, from that point of the presentation onwards, been utteryly lost in a growing fog of confusion. That fog is always an unknowable quantity when you perform such a lecture. Now, if you could see this fog grow as you talk, as you struggle to unfold difficult concepts, you would attempt to minimize its grasp on your audience. Only through such questions can you make a rough measurement of it, and that measurement is a better tool than just looking at their faces and try guessing whether they are thinking, confused or lost. A participating audience is, in my opinion, much better that a quiet one.
"Whatever." -Richard Feynman LOL
Wow he really is barefoot...
What a fucking legend
I wonder why
One should never argue with a barefoot Nobeloriate
your saying cause hes barefoot we need to listen to him? no thank you that leaves back kaos or live
its called grounding , your body exchanges with the huge neutral energy body EARTH ,nothing is of no importance
He is lecturing in a jumpsuit with no shoes or socks!
9:56 - Good grief; there always has to be people who think they're seeing some light that's been overlooked by the whole scientific community for decades. 😐
These boxes are more confusing than the og example.
Robyn Highart that's what I thought too, I'm guessing that means I don't really understand the implications of the original.
Binary
priceless content !!
sweet sweat suite!!!
Fine, but asking questions while Feynman is talking is blasphemy. Wait until the end... or go to school. He deserves a Nobel Prize in patience (not that he would have accepted it)...
Which makes plank constant a programme of the cloud computing
Why isn't this taught in church?
We cant even know what it is... until we know what it is :D
We can't even know what it could be, before we know what it is :)
Paul Higgins the quantum world is weird :D and I love it.
Deconverted Man Feynman as much, on both counts! :)
Jones Deborah Clark Barbara Lewis Maria
Richard Feynman starts explaining the meaning to life and how to become immortal at 18:01
The Heisenburg Uncertainty Principle may be demonstrated by this analogy. Take a sheet of paper. Write the number "one" on one side of the paper, and write the number "two" on the other. Due to the optical limitations of humans, we are only able to view one piece of the paper at a time. When viewing one side of the paper, you will either see a "one" or a "two" depending on the side you are viewing it from. Now, ask yourself this. How can I be certain that the other side of the paper will contain the number not depicted on the one I am currently viewing? That is, if I see a "one" on the side I am viewing, what assures me that the other side will display a "two?" This is the epitmoe of the Uncertainty Principle. You will never know the status of what you cannot view, as one may only account for only a single "constant" measurement at a time.
unfortunately, this is a misleading analogy, that oversimplifies quantum uncertainty. it is good to try to make sense of quantum craziness, but relying on classical intuitions more often than not leads to misconceptions. the first rule is to not confuse yourself.
your example demonstrates epistemic uncertainty, i.e. the notion that uncertainty arises from incomplete information available to us due to limitations of our measurement device. the limitations of our perception is a fundamental phenomenological condition that applies to everything (Husserl describes this in detail, we always already project properties behind the 'horizons' presented to us by our perception), while the Heisenberg uncertainty is specific to quantum phenomena.
your example implies that the particle is always either in state 1 or state 2, which is true for a piece of paper, but not for a particle, which is in a superposition of some linear combination of states 1 and 2. the uncertainty is ontological (i.e. it comes from the fundamental properties of the universe) and not due to measurement limitations.
my explanation is probably also not entirely correct (by no means an expert) - i have my own epistemic limitations =)
1:00 what if you continue to take measurements of the speed and position? Could you then measure the difference between the data points to atleast learn more about why the speed and position changed? I think that you could also then use those data points to calculate path and trajectory and even though you may lose the position, you can still predict where it will be in the future.
you can take as many position and speed measurements as you want, but you can never take them simultaneously. your data points would therefore only represent the speed OR the position at the given time, which means the trajectory will be fuzzy, as *you cannot just assume that the position barely changed at the time of your subsequent velocity measurement*. quantum dynamics does allow for calculations of "trajectories" and predictions of states in the future, but such trajectories are necessarily probabilistic and do not represent anything like a continuous path of a particle.
These trajectories furthermore only make sense if understood as the dynamics of the state of the particle (represented by its wavefunction) and NOT A DISTINCT PATH OF A SINGULAR PARTICLES MOVEMENT that we just have trouble narrowing down. such a classical picture of a point particle moving through space with a clear path simply does not make sense in QM, as the particle does not "have" a position or velocity essentially. this becomes more clear when we remember that it is not even essentially particle, since our setup of measurements could have the same "thing" appear as a wave (which we never would expect to have a predictable path).
All this to say: this quantum business gets endlessly confusing to the point of vexation if we think about it in terms of particles and trajectories instead of as quantum mechanical states that show up as different pictures according to what questions we ask about them.
anyway, hope this was helpful. sorry for wall of text and thank you for your curiosity =)
These are supposedly physics students but cannot understand a simple example.Physics is doomed
First of all, these lectures were given to a lay audience. Second, the most important quality a student of physics (or anyone who is interested in learning for that matter) can have is to be honest about what they don't understand and to keep asking questions. Feynman has said this many times.
The kind of elitism comments like yours convey would be the real reason that "physics is doomed".
Why is the audience asking such stupid questions
The disrespect of these pple... Speaking to him like he's just a normal person or professor... He was one of the greatest minds in human history!!!
Man if this had been school for me I'd have slept there
Consider what happens when you roll a die. For simplicity, assume you experiment is such that it only recognizes the one-side and the six-side. So you roll your die and it has a 50-50 chance of being a one or a six. After rolling the die, you look and see that it is a six. So, you say then that the die is now definitely a six with 100% chance of being a six. That is, the die is in a state purely with the six facing "up". (continued on next post)
Now, you do another experiment but this time you can only see the two-side and the five-side. So, there is a 50-50 chance of observing a two or a five. You roll the observe a two. So (if you didn't know this object was a die) you would say then that the die is the six AND two state. But no! Because now that you rolled a two, the die is no longer in the six state. In fact, it now again has a 50-50 chance of being a one or a six. (continued on next post)
My favorite physicist all the time 2023 January
Would like to hear people , who have disliked this , you dont like simple analogy's so be it, if and only if more minds tinker around the quantum subject, will their be more breakthroughs
To say more minds tinkering Will result in more breakthroughs is untrue. It makes it more probable but not certain
The system is behaving in a way dependent on what happened in the past.
Sup? Here, have some Wonder Showzen:
th-cam.com/video/Hf-xePlM-zg/w-d-xo.html
The simple simon game profited from this!
yes, but not with arbitrary precision on both of them.
Some people just need to be heard
@ 24:30 : Is he talking about the many-worlds interpretation?
9:12 sounds like Ed Witten.
I had always thought that the measuring means disturbing explanation of The Uncertainty Principle, was to give the layman some idea of what was happening, but that, in reality, there can never be both a position and a momentum of a particle and you had to choose which one you wanted to obtain, causing the other not to exist. Have I got it wrong?
The uncertainty principle has nothing to do with measurement. Measurement is simply irreversible energy transfer. The uncertainty principle is a general mathematical property of linear spaces and linear operators acting on those spaces. It applies to wavelike classical systems as well. You can, for instance, find it in functions and their Fourier transforms. If the function is "narrow", then it has a wide frequency response and if we want a function to occupy a narrow interval in Fourier space, then it necessarily has to have a broad envelope.
I think you are right. However, I don't think it is so that the momentum doesn't exist if you calculate the position. I understand it more like: you cannot have BOTH with high precision simultainously. So if you measure position, you get a smeared momentum, if you measure momentum the position is smeared.
@@gxfprtorius4815 Momentum exists. What doesn't exist in quantum mechanics is the equivalent of classical position measurements, hence we can not define velocity the way we used to. Position and velocity only make sense in the classical limit.
Can we agree this was an accuarte test?
Obvious troll is obvious.
Iv'e been a world renown physicist for 27 years and even I am confused by these damned boxes. He wasted 40 minutes (2 episodes) when he could have just stuck with electron momentum & position examples.
captions are wrong too
World renown huh?
wtf is with all the questions?
you should talk, question asker
the jiggle!!! lol
I expected a better lecture
:)
This is a truly great lecture! Probability math and Quantum mechanics forever entwined!
so new information is created?
what if the new information means something? like, can we read what has been allocated into memory from past allocations? im not a physicist, im a programmer. but wouldnt you belive in randomness if there was nothing to extract from the randomness?
@@Z3r0XoL randomness means substance exists of some sort, in a zero substance state there cannot be any randomness
Describing the quantum world in terms of classical examples like a cat or something, always seemed to me to be a bit odd. Quantum puzzles are puzzles because we try to view them from the classical level. Absence of an electron means presence of a positron, can never be understood in terms of the absence of a male meaning the presence of a female. What uncertainty are we introducing as a result?
Erwin Schrodinger and the Quantum Revolution (ISBN-10: 1118299264) touches on the development of the uncertainty principle and wave mechanics. I understood it when I read it at the time but I'd have to read it again to answer the question for you. Hey, I finally got to understand Relativity after years of trying, wave mechanics is my next hurdle, just so I can understand quantum computing, which is only years away). As a kid I grew happy in the knowledge that whatever I threw up would come back down. Physics made sense back then.
in the quantum world, these absurd scenario's are a reality, the same particle changes states
hence the possibility in parallel computing QUANTUM computers, different states may exist for the same, hence more possibilities than a mere 1 and zero
I love the socks :-)
this is how science progresses, for the public scientists win awards, for science they all try to prove each other wrong. If Scientists accepted authorities then Einstein may as well have left Newtonian physics alone.
I understand what you are saying. However, I still have the philosophical/practical/"definitional" problem of understanding how you could possibly know and say categorically that the two parameters have been measured "at the same time". If you show me an example that goes "do this and you will have measured these two different things at once", I will automatically retort: "How do you know that one wasn't measured just a moment before the other?"
Have...you ever -been- to college? He's teaching a lecture. People are asking questions to improve their understanding. That's called LEARNING. That's what Feynman did to get where he was when he was giving this lecture. I hate to break this to you, but Richard Feynman was -one- of those "neanderthals" at one point. He's a human being, who became brilliant through being inquisitive.
Teaching is not about geniuses imparting their great wisdom on the silent masses.
"TREAD-SOFTLY-MAN"..?...."SOLE-TRADER-MAN"..?..."PLANCK-WALKER-MAN"..?.. ...wow, bad puns galore there. apologies.
He talks just like Ed Norton. The one who goes, "Hey Roulphy boy!"
Yo! I totally agree!!!! Just don't put down Neanderthals. They had the good grace to become extinct!!! At least they would have shut up.
When you wrote "experiment" did you mean "measurement"?
- If yes: I don't understand how you could measure position and momentum with a single measurement. Maybe you could use the same apparatus for both measurements "at once", but the way the apparatus works probably makes two separate measurements.
- If no: I would guess that two separate measurements can be part of one experiment, and so your definition of simultaneous is satisfied by what he said.
this is in probable terms, if your goal is to check only of one particle, it may hold true, cause the next instance you want to check again, the very measurement act would have changed its state and momentum, SO we need some radical way to measure these delicate things
Interesting video...But the comment posted from "Spinpolarized" says it all!! :-)
Three quarters though this lecture...And it took a six pack of Leffe Belgium Beer to make this all clear. :-) Why is he barefoot?
Frustrating watching a smart man trying to describe something that doesn’t conform to normal logic. Human dynamics is painful to watch sometimes.
If you've ever done standard calibration, you will understand the light boxes and uncertainty. An example is calibrating a voltage standard or a voltmeter. The main laboratory standard has three sources, that each are measured. The standard or voltmeter being calibrated is set at the mean average value of the three sources. The three are are measured, then the reading divided to get the mean value, and that is the setting of the calibrated instrument, due to uncertainty.
I am confused by the box analogy. I don't know much about quantum mechanics, but I have heard of the Heisenberg's uncertainty principle. I'm hoping someone who knows about this won't mind answering this question: If you have a mechanical series of boxes, designed to simply change color on some simple principle of the first time you press it you get one color, the second time you get the other color. How does this principle work in that case? Or does it work in that case? Thanks!
nidurnevets you can in principle design boxes to do anything you want. For example, you could have a human being hiding inside the boxes who the controls the lights being produced to encode the complete works of Shakespeare in binary. Heisenberg's principle does not say anything about such a scenario, and it probably not interest physicists very much that a human hiding inside a box could reliably produce the works of Shakespeare. The reason that this is interesting is that these boxes have not being intentionally designed to give any particular behavior. They simply find these naturally occurring boxes that have certain behaviors, and they tried to form theories about how the boxes work, and ran into the troubles that Feynman mentions in this video.
In other words, the interesting thing is not that it's possible to construct boxes (mechanical or otherwise) that behave in a particular way; the interesting thing is that something as simple as a naturally occurring particle exhibits this behavior. It would be just as interesting if a naturally occurring particle emitted a binary encoding of the works of Shakespeare, even though nobody would be impressed if you could artificially construct a box that emits a binary encoding of the works of Shakespeare.
it is hypothetical situation analogy, to better imagine and grasp the subject
Annoying people in the public....
He looks like a barefoot superhero in that tracksuit.
is it possible to measure momentum and position simultaneously?
If you compare analog to digital gages on your cars dashboard it gives some insight to the difficulty in doing simultanious measurements that give meaningful data. When you watch digital gages they give you snapshots in time which become meaningless the moment new numbers appear. When you watch analog gages you get much more info because you get to see the rate of sweep and your mind can use this info to fill in data not given by digital.
Because shoes aren't necessary.
Uncertainty principle is based upon the fact that the universe is expanding is therefore another way we need to measure the rate in someway that the universe is expanding
Why is he barefoot? lol That's one weird lecture.
This guy is really arguing with a nobeloriate.
18:00 proof of aliens >.
No shit, Sherlock.
this is a classical example of why nothing will ever work or be good. too bad!
Logic and reason . He ain't got .
Strait up nonsense .
Nice one! LOL
Goddamn angry nerd disturbing the lecture...hope wherever he is now feels bad about this.
How did he disturb it? Richard even thanked him for his questions because they led him to describe the principle in more detail. I personally think the to and fro between Richard and the questioner was a lovely demonstration of the uncertainty principle itself, if you think about it. Or maybe I'm wrong.
+John Foster Hey, have confidence in your view. Don't end it with "maybe I'm wrong". Imagine Hitler ending all of his speeches with it.. he would have gotten nowhere.
+John Foster Hey, have confidence in your view. Don't end it with "maybe I'm wrong". Imagine Hitler ending all of his speeches with it.. he would have gotten nowhere.
+John Peters heard ya the first time
Feynman seconds later after the question said "I see what you're trying to say" but the guy does keep on going though, Feynman was very patient, he said he was speaking historically.
What does "simultaneous" mean in that context?
Different scenarios in same time