Richard Feynman: Quantum Mechanical View of Reality 2
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- Опубликовано: 30 янв 2016
- In this series of 4 lectures, Richard Feynman introduces the basic ideas of quantum mechanics. The main topics include: the basics, the Heisenberg’s uncertainty principle, Bell’s theorem and the Einstein-Podolsky-Rosen paradox.
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The sign of a great mind: he does not reject any of the stupid questions asked. Instead, he adjusts or augments them, first to validate the questioners and then to create meaningful answers from which he can continue and develop his arguments. RUclips gives us the opportunity to learn from the best teachers of all ‘recorded’ time. It’s great!
Sign of a great mind is a great big pocket protector…
The only stupid question is the question that isn't asked.
The best question is the question yet to be asked.
@@roadracer1584 there are stupid questions, if you do zero background reading heading into a lecture
Funny reading your reply verbatim .. At least in the context hindsight of the Challenger inquiry. Obviously I never knew him .. but I always liked to presume him a humble and approachable man. I still do. Though you can't help but belly laugh .. you just know he was setting them up as if an evil chess master with a giant fly swatter with that freakin' bit of o-ring and glass of water - not that they didn't entirely deserve it.. best reality .. actual reality .. TV moment ever!
I just enjoy the fact that you can hear in his voice how much passion he has not only for the science, but how much he enjoys teaching.
I don't understand anything he says but I go to sleep listening hoping someday I'll absorb it!
It's 4:00am and I just finished the first lecture and now I'm starting the second one. God I'm glad I'm retired. I'm gonna wake up around 1:30 today...and look for more.
gOD I AM RETARDED , LOOKING FOR more today , photons are big but no one is more surprising than intensity of light
I’m doing this also but due to quarantine!
rovidius2006
What the fuck are you saying?
Just came across a statement a few days ago that *there is no speed of light.* It just *is.* More digging required.
deltavee2
You can watch PBS Spacetime’s video called “The speed of light is not about the speed of light”
It pretty much says that the speed of light isn’t about light but causality. And causality has a maximum speed limit which happens to be what we call the speed of light. I do need to do more digging though since this idea doesn’t sit well with me.
It's wonderful how he continually resists explaining what nature actually is. Our work can describe what will happen in some situation, but it won't tell us actual truth. He was able to live with uncertainty, how very rare.
Physicists don't live with uncertainty as much as they live with ambiguity. That's a much more interesting concept. You have to allow for multiple, sometimes equally good, explanations of the same phenomenon.
I am immensely grateful for these brilliant lectures from the greatest of minds.
You tube is a goldmine of knowledge,history and science podcast etc. happy to be around this amazing concept!.
Thanks for sharing this , I m now binge watching all Feynman lectures I can find !
Feynman was a great scientist and greater teacher !! I learned a lot here. And I am going to finish all of his videos on RUclips .
HI!! I AM so thankful... and so I make this message for You, mrtp:)
ThankYou for propagating this beautiful lecture series! Im not a scientist, but a mere layperson whom is stricken with gratitude & curiosity towards "Reality", whatEver IT IS!!
Years ago, before I'd even known of Mr. Feynman, I had a profound dream. In the dream I saw a written language that was based upon combinations of hexahedron shapes that were interlocked together in a way that I instinctually knew to be some kind of magnificent intelligence! The reason I'm saying all of this is because when I discovered Richard Feynmans diagrams, for whatever reason, they INSTANTLY referred me to the memory of this dream, and also to the inherent beauty of the dream and intelligence involved for this experience of being.
Ah! If only you’d had that dream earlier!!
…we’d be calling them Karlerik diagrams now.
the best teacher I have ever had. Have read all his lectures and still there are a lot to understand. Wish I could be in courses.
I enjoy just listening to him talk. I am not at the level that I fully understand physics but it's my favorite subject and that's almost entirely because of learning from Feynam. Every interview he did was interesting. You can tell he had a love and appreciation for his field and he had a way of explaining complicated topics in ways I can understand.
This man loved physics and teaching it.
Its hard to decide if the study’s of these theorys or the teaching of this weird and cool stuff is making him more fun.
A brilliant scientist and teacher and iam really sad, that i wasn’t alive to hear one of his lectures.
Anyone who can explain the laws of quantum mechanics by using terms like "adding arrows" instead of the 10th grade math term "vector" is truly brilliant.
1:07:16 We've all had this type of fellow student in class😁
Incredibly informative! Thank You.
"Nobody is ever lost....." right about 32:00 .
Got me right in the quantum feels.
Yes, and there are also strange things happening with polarisation. that's another story also
I like how he is humble enough to say that this way of doing it is the one that works with every experiment man has come up with to date (when he answers the student at the 1hr mark). He does not arrogantly say that this is the only way of understanding the concept but rather leaves himself open to the possibility of something else being discovered in the future that could disprove this.
bf
Not like a real polly, that knows it's right now and forever - bsqawk - bsqawk - bsqawk ...
@@fwqkaw are you ok btch?
Interesting how some of the student(s) are in more need of the attention and control of the teachers acknowledgement than others in the group. Feynman, had the patience of a god.
yeh, that guy was a tool
Irving Kurlinski h
He's a passionnate
every class has them.
He was a great guy
I definitely learned something new today
tell me what you learned!
Richard has the patience of a saint. I would have taken that guy who thought he knew everything and kept interrupting and kicked his butt out into the hallway.
Little knowledge is dangerous. That attention-seeking guy was blocking himself from learning. RF was extremely patient and didn't let the focus to be lost.
I could hear myself saying, "shut the f up" or "take him out of here"... what a patient man!
Lol. That's why you aren't Richard Feynman.
you could try. but, students pay to go to classes and students can complain.
Dr. Feynman's capacity for intelligence, explanation of the abstract into concrete examples, his humility, his patience, and his Renaissance variety of interests probably made him the greatest Science teacher of the 2nd half of the 20th Century. Feynman's lectures will be remembered for Centuries in the future while his well deserved Nobel Prize will be a historical blip..
Several times he says 'I should have explained' when he actually has, taking the blame, just to ease his audience. A bit like Columbo.
Are you talking about physics ?
Koen Th you have a rare insight, don't lose that my friend.
lol so true
This man is nothing like the fictional detective. Columbo was not a conman.
@@Chicken_Little_Syndrome are you a flat earther? Why do you say one of the 21st century's most brilliant minds is a con artist?
Even though I,m a high school drop out, and don,t understand much what he says, I get a basic idea and like listening.
You are never incapable of learning more. Never hold back on learning just because you don’t have the same credentials as others.
the last part he explained seemed very doable. is there any videos on youtube about it?
The environment was uber inquisitive but in my opinion in a very positive way. "We never free a mind once it's reached a certain age. It's dangerous, the mind has trouble letting go." -Morpheus (in The Matrix, who knows whether it was positive definite or not...)
I love listening to him so much. I can not explain.
He is a magical communicator, teacher and human being. 🤍
"To light LIGHTS *heh heh*" I love his sense of humor.
Holy hell, he is an excellent teacher.
Fantastic lecture and endlessly funny to watch him struggle with the mic ;D ;D
Take A Moment
This must be The Best episode
Thanks from
Calgary Alberta
Untruedaux Land
Why was the video cut at 7:20 ?
what if the material was the composite, fiber optic i believe, that is made in space to prevent this very thing from happening? its made in space to reduce the "drag" on the light. you may want to look into this material. also, it could possibly be that its lined up exactly and the crystaline structure is responsible for the electron bouncing back? maybe i will think further and more thoroughly about this.
Hi :1) Feynman went along way to helping general understanding of what QM entailed..
Is it possible that when it comes to 1/25 Photons rebounding back up of surface, what we perceive as reflection might not be the result of tiny dot obstructions on the surface (1/25 of its mass) preventing the photons further descent but might infact be that not all photons are exactly the same some have a little mass therefore a cause to rebound.
Mass isn't necessary to treat light like a particle. Photons have momentum and therefore can collide with things normally. The difficulty comes when we realize that removing bits of the mirror can make the photon more likely to rebound.
Richard feynman is considered one of the greatest physicist ever in the history of science.he was a genius.he is called problem solver.he is one of the greatest teacher.!! He is the icon of most theoretical physicist today.!!
My physics professor's teaching style is very similar to fynman. He is a fan ofcourse
just... WOW!
LOVE YOU SIR !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
1:54:00 What kind of image does this make?
Correcting: ‘that can always be deconstructed by knowing at all times where you were and where you’re going’ etc.
Amazing!
outstanding-----thanks
In that question where you are asked who you would sit with and talk with from the past if it was possible mine would be Feynman. If I was allowed a second it would be Bertrand Russell
I am desperate to find a copy of the audio version (90minutes ) of these 1983 workshops .SoundPhotoSynthesis apparently has gone out of business and I don't know who else would have a copy .
The part at 25mn (reflection on glass depends on its thickness) and especially 28mn (an even surface would reflect some value between 0 and 16%, but in usual every lives the surface is not exactly the same thickness everywhere and we get the expected 8% overall) makes me thing about Hubble and James Webb telescopes: Do they purposely so uneven surfaces to not fall into the trap of maybe having a lower reflection? or on the contrary aim for the double reflection value? (probably can't aim for it as several different incoming wavelengths will need to meet different thickness to be reflected at the maximum value...)
No. :-)
Excellent
How may we claim that one click heard at the output represents precisely to one photon and not avalanche effect to accumulated analog charge?
So is Feynman's ''grating'' a polarizing lens? And are gratings used in night vision goggles to isolate a single wavelength of light for greater reflection?
that's classified
What year was this?
WHEN did professor Feynman conduct this series of lectures?
'mrtp' posted NOTHING about the date or location
I had Physics professors waving Mathematical Physics like a wand making graduate students disappear. Whoever did not run out of fear passed the class. Sad but those were the days when Physics was big. No reason for arrogance. In reality the Physicists plodded through discovery like clods too because most think the universe follows what sense they make. The speed of light a constant? Quantized energies? Why not? You can be famous going the "wrong way". :) Feynman seemed such a modest and pleasant man. Never met him but he was known for it I read.
@Jeffrey Simmons It refers to arrogant Physics professors blowing away students who could not keep up with the math in graduate school. They were arrogant but they discovered nothing because they were blockheads and could not think outside the box. Physics moved ahead because the real thinkers like Einstein accepted what went against common sense: speed of light a constant. Energy quantized. Thinking outside the box all the other Physicists were in made him a superstar. :)
"I don't know but the nature works that way".
Some of these complicated colloquies remind me exactly of my internal dialogue with "myself" except the two "debaters" in my mind are much harder on each "other. "
Wave-particle: if you differentiate the wave function to determine real-time rate of change, then there's the self-defining measuring system of relative sync-duration in terms of AM-FM Communication.
"Make up your mind", space-ing is coordination-identification to/of "empty" point positioning, ie Singularity, and that is why a "Particle" is the functional measure of point positioning Timing-spacing-> sync connection containment states, aka Quantum-fields Mechanism of AM-FM In-form-ation.
?! And the circumstances that lead to "One Electron Theory" or hyper-hypo Superspin-spiral thesis, in which Eternity-now is Functional Unity, AM-FM Universal standing wave-packaging (ancient Greece believed was a kind of temporal jello), elemental connection continuity.., "and so on".
RF Imaginary Thought Experimentalist's practical Intuition=> "space" is continuously created in temporal superposition, of/by spin-spiral logarithmic shaping timing.
The i-reflection universe of QM Mirror, through, back, and eternally contained with "any name we want" in logarithmic spin-spiral condensation modulation interference coordination positioning:- Lewis Carroll and Richard Feynman.., requiring Fine Tuning , "thinking for your actual self".
Or, Temporal Superposition-point Quantum Operator, => no-size one Electron, one photon-phonon universally continuous zero-infinity axial-tangential e-Pi-i sync-duration modulation information-> Singularity-point positioning, NOW.
"I like to use the word Amplitude", because it's analog line-of-sight "Arrow of Time" superposition identification density-intensity, real-numberness in e-Pi-i sync-duration connectivity.., probability resonance-wave functions of re-circulation/evolution.. too.
If we move the dots to fit the curve, this demonstrates how projection-drawing methodology is a Theoretical Calculus, "it's always NOW" least timing incidence and not how in an Experimentalist's practical recognition of Actuality Conception, this is a reversible process of Observation. (Don't do that?)
As demonstrated, the sum-of-all-histories temporal, here-now-forever Arrow-> amplitude, is time difference rates of i-reflection orthogonality, continuously creating the sync-duration probability resonance cavity space/bubble-modes at "flat" ground state, zero-infinity difference->singularity NOW.
QM general logarithmic quantization, instantaneous logical observation, "Nature works that way", in re-view, re-cognize, and re-evolution.., This Time.
Why is the probability proportional to the square of the amplitude? and not just the amplitude itself?
I guess that's a bit of a shallow explanation, but one way to think about it is that intensity is the energy that permeates a surface over time. Now, light wave amplitude tells you about the energy content of the electric and magnetic fields. The square of the amplitude, multiplied by a proportionality constant gives you the intensity of the light. If you think about what intensity means for a stream of particles that travel with wave like properties, then you can imagine the places on an absorbing surface that have the most particles hitting is the place of the greatest probability of finding a particle. I hope this helps, I'm a materials scientist, not a physicist so I might have some things wrong.
The square of the possibility is the probability that the outcome will be that way!
The next time you go to a bank look through the extra thick glass/acrylic panels between the tellers and the lobby, this will make plane the change in photon trajectories that thicker reflective surfaces can have.
Lets not forget the fraternal order is what shaped Richard: Of where I want full membership guys:
if it is possible could you add subtitle please. ps : i am not a native speaker.
22:55 Why would a proton get reflected from the "back surface"? I feel like the "back surface" wouldn't be a surface of glass to a photon that reaches it from *inside* the glass. Wouldn't that be the surface of the *air* below the glass. Otherwise, I feel this would mean that the glass in a window has four surfaces: two outside surfaces and two inside surfaces? Or billions of surfaces - one at every single point in (or layer of) the glass?
The surface is an illusion. It has no thickness, it's just a point in space between two materials. The light particles simply bounce on the irregularities between the two materials at that point.
Proton backscattering occurs when a high-energy proton encounters a surface, such as a solid material, and interacts with the atomic nuclei in the material. The probability of proton backscattering depends on various factors, including the energy of the incoming proton, the angle of incidence, the type of material the proton interacts with, and the atomic composition of the material. This phenomenon is essential in fields such as nuclear physics, materials science, and particle interactions, where the behavior of high-energy particles like protons is studied in detail.
Holy sheep shit.... Now I understand why I have always resisted most of the explanations in mathematics.
Another sign: he recreates the context and thence the questions as great scientists like Newton would have asked them. It might all seem obvious because we have the answers Newton and others gave us. But what if some answers were wrong? Then we live with those mistakes until Feynman types come along, spot them and develop the corrected answers. And these Feynman types are lucid and simple in their delivery of arguments. They’ll tell you that if they can’t do that, then something is probably wrong with their arguments. From this basis, they are able to build up theories of great complexity that can always be deconstructed as long as you , knowing at all times where they were and where they’re going) no matter how complex they become. They never lose sight of those ‘dippy rules’ he refers to.
It didn't take Feynman to point out problems with Einstein's messed up model of light quanta. That had happened much earlier. One can argue that by 1928/1929 the worst cracks had been filled by smart people like Dirac (who was Feynman's advisor, I believe) and Mott. Feynman basically just screwed the lid on Einstein's quantum coffin in 1948. As you can see from the timeline, though, the major insights had been available way before him.
Feynman's advisor was the great John Wheeler. Not Paul dirac.
Dam he is my inspiration
Mine too! Evere since I discovered his participation with the development of the nuclear weapons and the simple test for the unacceptable use of the material used for the caskets in the space shuttle that exploded when launched killing our astronauts!
Man I’m damm sure Feynman is my bestestest chance at understanding this👍🤔😂🙏
I want him talking about bells theorem and epr
Watch the first video.
For the arrows explaining the glass reflection, isn’t it equivalent to the wave explanation?
It's similar, except that he is talking about the quantum mechanical version. Since the result of the quantum mechanical calculation and the classical calculation are identical for this case, there is little that one can learn from his approach.
How exactly is it quantum mechanical about his approach? What is the subtle difference that I’m missing out here? Say if he didn’t mention that it’s quantum mechanical, would anyone be able to tell the difference?
@@jadongao2880 What you are missing here is the proper mathematical expression for the path integral, which is an infinite number of nested integrals. One could look at the Huygens-Fresnel principle as an early precursor of Feynman's path integral, except that it does not contain the complex exponential of the classical action, yet, so it's not a proper quantization procedure. Other than that the basic ideas are similar. And like I said, for non-selfinteracting bosons the classical theory and the quantum mechanical theory are very, very similar, which makes light a very poor system to learn QM on.
44:40 the guy in the audience says 'like a big bean' for Venus and quick as flash Feynman says "maybe you'll figure out it's a big arrow'. This works on multiple levels and took me like a minute to think through and Feynman took like 1 second. The man was a genius
I don't get it.
Every physics teacher or youtuber should be required to watch and understand this (and other similar) Feynman video before they go off trying to use waves to explain these phenomena
No mistaking it, the man was definitely from New Yawk.
Raised in Far Rockaway, Queens. Ya can't get more than that.
@@deltavee2 a great safecracker
@@badmintongo4832 A very intelligent man of many talents. Personally, I hold him above Einstein because quantum physics.
He was one of our best, yes.
What happens at 1:16? I don't hear the question from the audience.
Feynman says “in real nature” . An eager lady from the crowd jumps too soon to ask “what is real nature ? “ Feynman doesn’t get it , then the lady says “what is unreal ? “ and not letting the confusion go further Feynman says he just made a mistake elaborating the phrase. He goes on making reference to this impasse later on . Smiling and saying “real nature”
He his a great teacher. My teacher when I took classes about that just vomited formulas on the board, did some manipulations to them and claimed that was it. No explanation whatsoever.
How is this mirror called with removed parts?
en.wikipedia.org/wiki/Diffraction_grating
When these lectures were recorded. Would be intersting to know. Somewhere in 80s probably..?
He passed away in 1988
Yes, same year as my mother. These vids are made some time before. He doesn 't seem sick at all.
@@sekoivu True he doesn't seem to be sick at all but you can't always tell if someone is ill! You can fight cancer for a long time!
Time seems to be a factor in reflection of light. Hear me out.
Is it possible that if time is in fact a factor, could it be that the atoms in the material do something a x time that causes collision and thus "reflection"?
Photons have no charge AND they have no mass, however when they slam into your skin you can feel the transfer of energy that happens on this collision.
Is it possible that the jiggling of the atom stops or harmonizes for a billionith of a second and when this occurs the photon slams into the atom and is either rebound OR obsorbed and a new photon is created and shoots of in the direction of the source of the first photon..
1:07:08 ......."these are irrelevancies" and "if you try to make the model too correct, it isn't gonna be right for some other question". and that's why it's a theory with strong competitors. but the competing theories don't have 90 years of the world's smartest people having worked on them.
If we as spectator physicists like us have spent so much time considering alternative theories and interpretations, how much time must the world's smartest people, who devoted their entire lives to physics, have spent puzzling over them, especially knowing that with their clout and mathematical backgrounds, they could piece together something worthy of a Nobel? The marginalized theories haven't been ignored, they've just consistently refused to bear more fruit than standard QM, QED, and QCD.
In the example around 1hr 38 min, why do we assume that light travels only in straight lines?
There's a case to be made for curves???
It doesn't. Ray optics is an approximation of wave optics, which is a limiting case of quantum optics.
He was a brilliant man
Brilliant? Richard feynman is considered one of the greatest physicist ever in the history of science.he was a genius,problem solver.!! He is the icon most of the theoretical physicist today.!!
Bongo Feynman is the best Feynman.
instictive thought, if gravity effects how the material settles and the crystalline structure, than it would have somethign to with not just the composition but the way gravity effects the material.
that's classified
Watts said something along the lines of what is form is precisely emptiness and vice versa...form being the inner workings rather than substance. So yes, cool train of thought.
13:30, 27:28, 30:22, 33:12, 42:28, 1:14:55, 1:29:58, 1:45:23, 1:54:07, 1:54:54, 1:55:30, 1:55:57, 1:57:54
i wonder if rappers take inspiration from this. his talk was so good he dropped the mic 10 times
45:25 - explanation start
Finally since the beginning i was bothered with this part 1:30:00 , how the hell Feynman disregarded the multiple reflections?
Most thought of internal reflections occurs to most people, but the best way to explain something complex is still one step at a time, especially when it's something so counter to the macroscopic scale of our everyday experiences and intuition.
Commentors - please time stamp your examples to clarify. It's, well, a bit more "scientific" that way.
3:57 Phenomena of light
28:47
Feynman was a fine man.
To think we’re watching feyman right now via photons from a screen of some sort? that’s pretty cool ?😎
A single photon reflects with a chance determined by the added amplitude arrows of each surface it encounters. I'd still like to know how that is determined if the photon is already on its way back before it would reach the last surface.
Richard was full of it.
صورة بتذكرنى بالشاعر الاستاذ جمال بخيت
مش باقى منى .........
Some people said that he talks like a bum, he sure showed them. It is what you know and how you convey what you know in simpler to understand ways, not how a person's voice sounds.
1/2 the lecture was the rules....just give'em a handout sheet with the rules.....and explain the bare feet at the bottom.
Thank you for making me feel more stupid. Legend.
When you feel stupid it means that youve already taken your first step towards becoming smart :)
Basically the same response Teller had to an Einstein lecture.
Einstein, seeing Teller upset after, asked him why. Teller felt stupid, and told this to Einstein. Einstein told Teller: Stupidity is the human condition.
(Edwin Teller went on to become a giant among giants)
@@jacobcastro1885 Okay then I'm in good company hahahahaha
1:06:22 I thought he was going to take off his belt a few times in this video.
Imgonnagogetthepapers getthepapers hahahaha
Why does light only bounce off of the SURFACE of glass? What property does the surface have that the rest of the substance doesn't?
reflectivity, that and the ability of our eyes to see reflective light, in a way that we can mentally picture as a reflection of another image
also photons, are absorbed by atoms and then emitted with the same energy. rather its the electron field that does it. and they emit the energy at the opposite direction of that which it the received the photon. which is amazing due to seeing things from angular direction..
Usually, in the classical wave optics, the reflection happens when there is a change of refraction index, that happens on a so called "separation surface" between two different materials. The problem can also become more complicated if the refraction index of the material is not constant, but changes with position in a "continuous" manner.
no
what do you mean, no?
How does light pass into water and appear to slow down but then exit and appear to speed back up? This would violate the law of conservation of energy. Notice how he says wave theory was invented and not discovered, imo a critical point being made.
Where is the violation of energy supposed to be here? The electromagnetic field changes the state of the water molecules, which takes energy.
At 1:14 he says if we get there, unsaid if that guy shuts up.
1:57:17 WHAT DID HE SAY???
What happen if it hits a sphere
He was a Feyn man.
great video but i would have learned more if there was an eng subtitle.
He’s very Colombo-esque
I really wish that this video was audible. I am not deaf. and I can't read lips.
yes, questions are good, but heckling is rude. i'm building a time machine so i can travel to 1983 and walk over and fucking *slap* that guy off to the left who keeps harrassing feynman (aka the guy who won the nobel prize for figuring out quantum electrodynamics). sheesh!
1:16:00 in and in one of the infinite realities of existence this video is interrupted again, amidst a trail of plastic chairs I`ve already steamed across the room, past a man in a dodgy looking time machine, and I`ve retarded to mans` earliest behaviour and I`m bludgeoning that ignorant fucking shithead with a fire extinguisher. Behind me there is an Airplane~esque queue of weapon wielding folks with the same intent. Enquiries to the lecturer should only really be to request further explanation (if possible) of something you can`t quite grasp, raise one`s hand and wait to be addressed, What a fucking ignoramus to shout out opinions. To challenge Mr. F., in such a manner highlights this persons hideous nature and also indicates that his potential will never be achieved, listen, digest, investigate, try to understand first and then if necessary, enquire at the end of the lecture as to why nobody has heard your ground breaking theories. Mr. F. shows that intelligence also includes a huge dose of restraint and manners, he possesses these and all the other ingredients that go to make up a decent human being.That guy probably went into politics.
looking for a ride back to 2017.
2:13 "We really don't understand it very well..." This was Feynman being charmingly self-deprecating to an audience he assumed was generally well-educated and take the understanding of classical physics as assumed. This recording played for a generally ignorant audience will have the unintended effect of giving them the idea that reality isn't well understood. This is generally false. Or rather, our profound ignorance kicks in well below the threshold of our senses, and at the extreme boundaries of our instruments - at the scale of individual atoms, and smaller. So when Feynman speaks with humility here, he's not speaking in general about physics, he's speaking specifically of the tiniest scales we can do experiments with.