Richard Feynman Lecture on Quantum Electrodynamics: QED. 1/8

[PelicanGodOfJupiter]

Anyone know where I could see the whole lecture?

[4kx]

He was great physicist and great speaker

[jamespowell1969]

our not are 

[eatingtacos000]

I've seen this whole lecture 3 times. I just love it. Im so happy Im alive at a time where such amazing things are known!

[DanFrederiksen]

they should really be uploaded as one.

it's fairly decent lectures. but it is disappointing that he doesn't go into more detail like polarization and he fails to answer the question about how lasers work and more importantly fails to realize and admit that he fails.

[Fnordicus]

@DanFrederiksen you should realize this is from 1979

[DanFrederiksen]

@Fnordicus quite irrelevant when he claims to have formalized a theory in the 40s for everything except nuclear workings and gravity

[ckeilah]

Why bother putting this up in HD? The original is from a VHS tape! :-P

[sn1pe352]

"Theres a big difference between knowing something, and knowing the name of something" Dr. Richard Feynman PhD

[kjrunia]

I wish I could go back in time and ask him about life, the universe and everything.

[Lima547]

Amazing piece of science and history!

[bouzaglo3]

video.google.com/videoplay?doc­id=1501838765715417418#

you have all the fuuls kecutre in here in googl video if you want too see

[achintyagopal1486]

so is everyone who watched this video a scientist, went to college, or in college?

[MuonRay]

@achintyagopal1486 Maybe. Though they don't have to be. This is the internet; elitism has no merits here. watch it if you are a scientist, science student or graduate yes, but also if you are intersested in it. anyone can, and should, watch it, just as people should acknowledge the contrabutions that everyone makes each day. we should all realise that those who grow are food and those who keep our cities and planet safe and clean are just as valiant, even more so in my books.

[EquinoxParadox91]

@MuonRay I like what you said about the internet not pertaining to an elitist view. However, sadly that's not the case with most of the videos on YouTube, particularly the specialist ones (ones relating to physics for example). It seems that people like to find ways to make themselves look bigger by leaving comments that make them look superior to the everyday viewer.

[MuonRay]

@EquinoxParadox91 well I am aware of quantum electrodynamics enough to do computer simulations on it-> where you can visualize subtle effects which are, as of yet, undetected by detectors used in partyicle physics but which could be detected, theoretically. So it Iis important to create a beauty in such complicated things, which may be an illusion in some cases, but never to dumb it down. Feynman was good at that. It is the job of a good scientist to make the complicated appear attractive.

[EquinoxParadox91]

@MuonRay Yes, Feynman was incredibly good at that.

[Garrincha2014]

@MuonRay May I ask which program are you using to recreate Quantum electrodynamics interactions?

[MuonRay]

@Garrincha2014 They are C++ codes that I wrote myself to simulate the distribution of photons released by Coulomb scattering of high energy particles. It turns out there are only 3 rules to Quantum Electrodynamics, 2 of which involve mathematical constructs called Propogators(which are a kind of complex number), which are represented by lines in the Feynman diagrams, and the other is a Vertex(given by the square of the electromagnetic coupling constant, ~1/137, which is proportional to the...

[Garrincha2014]

@MuonRay Wow you do know a lot.You seem to really into this field by your description of The Feynman Path integral, wish you the best youll get very far and thanks for the info.

[MuonRay]

@Garrincha2014 no problem. I use computers a lot in my work and although I am primarily an experimentalist I will gladly sit down and read about this area of physics, which is much more advanced and requires greater mathmatical literacy. doing simulations on computers with C++ and Matlab is a rewarding application of this knowledge, as is the mathematics itself. however in this day and age people want graphical results, not just fancy equations, which is kind of sad in a way. math is beautifull.

[MuonRay]

@Garrincha2014 ...probability amplitude of detecting a photon(represented by the angles in the Feynman diagrams). Feynman's theory is based on the Born series of these Vertices, which is proportional to the probability amplitude which is the Feynman path integral; which is the integral of all complex exponentials of the action for different path histories(action is the integral of the Lagrangian for the electrodynamic field which contains the Energy and Coulomb potential.). my program works...

[MuonRay]

@Garrincha2014 ...on the solutions of the Propogators, which are one loop and 2-loop order(3-loop order doesn't exist for Quantum Electrodynamics but does work with Quantum Chromodynamics using quarks and gluons), which encompases the renormalization. the Vertices are merely virtual photons which are the multiples of the number of time slices on the particle's trajectory(I worked an equation for this which involves Log rules), but it can give accurate results of photons released to a detector.

[MuonRay]

@Garrincha2014 There are many high energy examples of Quantum field theory used in simulations involving Lagrangian Mechanics and how different particles can have different distributions from a Vertex(which can be from a particle collision). simulating the polarisation of particles and comparing with experiment allows to detect new forms of symmetry breaking, which gives us more features of the forces involved and may give us information of physics which is beyond the Standard model.

[MuonRay]

@Garrincha2014 Quantum Electrodynmaics is interesting, but it is well tested with the corrections to the atomic energy levels discovered as the Lamb Shift being verified by QED. the one major thing QED has to solve is the Casimer Effect, however it is believed Dark Energy and QCD may have a role in this aswell. Electroweak and QCD are easier to simulate visually but not so much numerically so we can make visual predictions, which I think are much better in terms of simulations.

[polyguo]

@EquinoxParadox91 Education is inherently elitist. The more educated you are, the fewer peers you have. To be educated is to be privy to things about which the vast majority of humanity is ignorant. There will always be those that stress these differences, mainly to make up for being poorly endowed elsewhere. So take a lesson from christianity and turn the other cheek to self-validating elitist assholes.

And remember: "He who knows does not speak, he who speaks does not know"

[funkit22]

@MuonRay well said

[terriblefez]

@achintyagopal1486 I'm none of those, but I study, and I can watch Feynman. It means he really understands what he's speaking about, that he could explain it to me without losing the purpose. Maybe I'm just clever, but I'll put the merit on him.

[temporaldisplacement]

@achintyagopal1486 I went to college, but to us (in england) university is college and college would be the last years of your high school. (we end compulsory school aged 16) .....essentially I'm just some interested guy.

[mightyafrowhitey]

@achintyagopal1486 To put my two cents in... I guess I came to this video because I've always had a real interest in science (among many other things), and I find Richard Feynman to be an extremely interesting character. I'm 32 and have had some college though not very much at all. I guess I just have an insatiable appetite for knowledge and love learning new things. Math however, is one field that I'm not very good at whatsoever so a lot of this will surely go way over my head.

[HORRORTV1]

@achintyagopal1486 I'm still in highschool, but I'm interested this.

[muzammilali007]

Thank you for posting these amazing lectures. A few years ago I became avid about astronomy which also made be eager about cosmology and particle physics but by then I already was in my final year of electronic engineering. I wish I'd developed this interest a little earlier :,( changing the field seems too risky now and all I can do is keep learning more and more by watching these lectures on youtube.

Thanks again

[dreaminglucidly139]

I'm a biologist and I treasure this too. Feynman is incredible: he makes me want to go back to undergrad, learn physics, and apply what I learn to bio.

[MuonRay]

@dreaminglucidly139 yeah, its probably better to study physics in undergraduate school and then make it applicable to biology. Physics is the hardest of the sciences in terms of actual problem solving, so its better to train your mind to it the minute you start college; where you are around 16-30 say or it may become difficult to pick it up as apostgraduate doing a masters or PhD. studying biology in courses in a degree program is geared towards a less applicable approach.

[x1x2x3ct]

@MuonRay its mathematics

[MuonRay]

This is physics, specifically- Feynman was a Theoretical physicist, he was'nt a mathematician. mathematical science streches across a wide range of subjects. pure mathematics is much more rigorous than this- you would know a mathmatical scientist if you saw one, they are more often than not very abstract-minded- they don't have ideas, like Feynman would, they have hunches about everything. mathematics is 50% assumption even in the best case scenario. Feynman was very much trial and error.

[x1x2x3ct]

@MuonRay indeed, its a lecture on physics, but at any rate, it was referring to 'Physics is the hardest of the sciences in terms of actual problem solving,' Mathematics is, of course, also a science

[MuonRay]

@x1x2x3ct Well there is mathematical science, but its not really a science because mathematics itself does not exist in nature; there are no fossils of mathmatics, mathematics has been something, in terms of human civilization, which humans developed themselves; like a language. for the same reason computer science is not really a science, nor is social science- they are products of our interpretation. if anything they are an abstract form of mental engineering and conditioning.

[x1x2x3ct]

@MuonRay it's a science, and that's evident. it's not a natural science though. for otherwise you can't call the theories of QED, QCD, QTF scientific either, since they use mathematical reasoning. without mathematics we wouldn't even have newtonian mechanics. as far as the nature of mathematics is concerned, G.H. Hardy once wrote: 'For me, and I suppose for most mathematicians,

there is another reality, which I will call ‘mathematical reality’

[MuonRay]

@x1x2x3ct They are scientific theories because they allow for predictions which can be replicated in experiment. the hyperfine structure of hydrogen can be found using QED calculations and allowed the fine structure constant to be determined, which can be related exactly to the Lamb-Shift of hydrogen, which can be found using a device called a maser to precise acccuracy. the point is these quantities exist in nature, for any theory to be a scientific one it must have experimental evidence.

[x1x2x3ct]

@MuonRay ''for any theory to be a scientific one it must have experimental evidence.' obviously one might also in practice observe that a^2+b^2 = c^2 for any triangle containing a right angle. but experimental science is for second-rate minds, for any experiment will never reveal deep insight into nature, but merely evidence. it is absolutely absurd to have empirical equations; for no truly scientific law is based merely on experiments (in particular in the field of theoretical physics).

[x1x2x3ct]

@MuonRay Feynman himself writes in 'the character of physical law': How can you guess the right

answer if, when you calculate the result, it disagrees with the experiment? You need courage to say the experiments must be wrong.

[x1x2x3ct]

@MuonRay but I absolutely have to disagree with 'they don't have ideas', for it is evident that mathematics, as a whole, is built on nothing but ideas

[MuonRay]

@x1x2x3ct Perhaps I got science and matehmatics mixed up; a scientist is more like a detective- educated geuss( a hunch essentially) is what scientists have to go on, rather than true, spontaneous ideas which would be what an engineer would have. mathematics is a mixture of the 2: mathematics would be somewhere in the middle trying to tie science and engineering together. mathematicians prove, scientists solve, engineers ask- a bit more dynamic than most systems in terms of overall production.

[culanza]

@dreaminglucidly139

and why don't you do that? biophysics is pretty well an advanced field of research

[JayMark2049]

@dreaminglucidly139 You don't need to go to school to learn physics.

[cxaxnxexs]

@dreaminglucidly139 Haha so funny. I am a engineer/physicist & watching his "The Character of Physical Law" lecture on symmetry in physical law he makes me want to study biology! Biological systems are so beautiflly complex it is like perfect engineering at work. In fact, many engineering & physics breakthroughs (feeback control theory, fluid modeling, etc.) came from some biological principle (Fibinacci sequences in nature, bumble bee flight, etc. etc.). VERY cool stuff!

[prime301088]

A true treasure for us physicists! He was indeed a great scientist and teacher. Thank you for your upload!

[ferkinskin]

great

[maulcs]

THANK YOU