19 ms·
Probability (1963)
- sillysaurusx 4y agoIt’s worth noting (much to my surprise) that the Feynman lectures on physics weren’t written entirely by Feynman. I’ve often wondered whether the wonderful conversational style I’ve associated with him is actually him, or one of his contemporaries. Either way, this is a great chapter on probability. Thanks to whoever wrote it!
- barrenko 4y agoEvery great man is a Shakespeare.
- sillysaurusx 4y agoI’ll look terribly uncultured for asking this, but was Shakespeare a collection of individuals? That’s very interesting; thanks. EDIT: Aha: https://en.m.wikipedia.org/wiki/Shakespeare_authorship_question https://en.m.wikipedia.org/wiki/Shakespeare_authorship_quest... Well, this is a fascinating rabbit hole. Apparently there’s some question whether Shakespeare himself was literate, since his parents and daughters seemingly weren’t.
- b112 4y agoShakespeare true or not, I have often found that when one excels, others sit on the sidelines, stupefied in disbelief, then shout cries of delusion about the accolades before them. Hence, Shakespeare cannot be real, for he excels you see...
- ageitgey 4y agoJust keep in mind that the Shakespeare authorship conspiracy theory is the is the "the moon landing was fake" of the 1800s. The theory first gained popularly thanks to Delia Bacon in the 1850s, over 200 years after Shakespeare lived. There's no evidence Shakespeare didn't write his plays and a lot of evidence he did (including multiple books and writings published during this life listing him as author or referring to him as an author).
- marcosdumay 4y agoI guess the GP is more about the idea that Shakespeare was just the first one to write all the folkloric ideas of his time in a format that people loved, instead of that unexplainable genius that created all those interesting stories. (Kinda like Disney. But we don't have the originals anymore.) That one is a lot better accepted than the idea that he didn't write his works.
- dredmorbius 4y agoSomewhat related: "Shakespear's plays weren't written by him, but by someone alse of the same name" : an essay on intensionality and frame-based knowledge representation systems by Douglas R. Hofstadter, Gray A. Clossman, Marsha J. Meredith. <https://www.worldcat.org/title/877842789 https://www.worldcat.org/title/877842789> (Yes, that Douglas Hofstadter.)
- stiff 4y agoThe "Feynman lectures on physics" books are based on actual lectures to Caltech students. You can listen to audio tapes of the lectures here: https://www.feynmanlectures.caltech.edu/flptapes.html https://www.feynmanlectures.caltech.edu/flptapes.html
- sillysaurusx 4y agoThanks! Interestingly, the tape for Probability seems to be narrated by someone other than Feynman. I should probably give some evidence to back up my claim that Feynman didn’t write all of the Lectures, but alas, it’s late. I think the credits for the rest of the authors were in the preface, or at the end. I just wish they’d gotten a little more credit.
- vmilner 4y agoThat someone is Matthew Sands: “Early on, though, a small problem surfaced. Feynman had a long-time commitment to be absent from Caltech the third week of the fall semester, and so would miss two class lectures. The problem was easily solved: I would substitute for him on those days. However, to avoid breaking the continuity of his presentation, I would give the two lectures on subsidiary topics that, although useful to the students, would not be related to his main line of development.” https://physicstoday.scitation.org/doi/10.1063/1.1955479 https://physicstoday.scitation.org/doi/10.1063/1.1955479 Later on he writes about the published books: “The next stumbling block was more serious: choosing a title for the book. Visiting Feynman in his office one day to discuss the subject, I proposed that we adopt a simple name like “Physics” or “Physics One” and suggested that the authors be Feynman, Leighton, and Sands. He didn’t particularly like the suggested title and had a rather violent reaction to the proposed authors: “Why should your names be there? You were only doing the work of a stenographer!” I disagreed and pointed out that, without the efforts of Leighton and me, the lectures would never have come to be a book. The disagreement was not immediately resolved. I returned to the discussion some days later and we came up with a compromise: “The Feynman Lectures on Physics by Feynman, Leighton, and Sands.”
- triknomeister 4y ago
- darkerside 4y agoHave you watched any of his videos? I don't know the exact style you're thinking of, but wonderful and conversational match what I've seen from him.
- mananaysiempre 4y agoThere’s an unpleasant point in the history of the Feynman lectures: them coming out as “The Feynman Lectures on Physics by Feyman, Leighton, and Sands” is a compromise solution for a dispute where Leighton and Sands wanted to be credited for editing the transcript into readable prose and Feynman considered that work to be purely mechanical and not worth any credit at all[1]. (There is apparently more uncredited work in there as well[2].) “Feynman didn’t understand editing is an art” is not much of a headline, but the compromise is still there, in huge letters right on the cover. [1] https://doi.org/10.1063/1.1955479 https://doi.org/10.1063/1.1955479 [2] https://doi.org/10.1063/PT.6.3.20211209a https://doi.org/10.1063/PT.6.3.20211209a
- sylware 4y agoWhat's astonishing: many laws of physics emerge from statistical approximations of quantum mechanics. One day, if I really get into quantum mechanics, I will try to understand how they rebuilt maxwell equations from QED.
- programmer_dude 4y agoI think you mean "ab initio".
- killjoywashere 4y agoQED = Quantum electrodynamics, for which Feynman won the Nobel Prize.
- sylware 4y agoYeah, I meant the latest QED based on the lastest QFT.
- programmer_dude 4y agoMy bad.
- mfn 4y agoRegarding how to derive Maxwell’s equations from QED, I’d recommend this lecture: https://theoreticalminimum.com/courses/special-relativity-and-classical-field-theory/2012/spring/lecture-9 https://theoreticalminimum.com/courses/special-relativity-an... This derivation is in the context of classical field theory, but QED is only a short hop away through path integrals. It’s quite remarkable how the complexity of Maxwell’s equations can be reduced to a single term in the Lagrangian - (F_uv)(F^uv), assuming no charges. That’s really it!
- mhh__ 4y agoRead Quantum field theory for the gifted amateur
- ThomPete 4y ago
- deltasevennine 4y agoI have a related question to this topic. Is probability axiomatic to reality? Does it exist on the same level as logic where logic is axiomatic to reality and just assumed to be true? Or is it simply a phenomenon arising from logic? It seems like probability just happens to work without explanation? Intuitively this seems a bit strange since it feels as though probability should be derived from something else. Not sure if I'm correct here. What confuses me even more is that I do know logic can be defined in terms of probability. Causal connections can be probabilistic. If A then 25% chance of B and so on.
- BOOSTERHIDROGEN 4y agoAlso in relation to reductionism.
- quickthrower2 4y agoA lot of what probability is, is the extent of lack of information. The Monty Hall Problem is a great example of this. So I would say the more fundamental thing might be information theory. This my layman view. Not an expert.
- lupire 4y agoProbability is weight/count of cases of interest divided by weight/count of all possible cases.
- quickthrower2 4y agoI just rolled a 6 sided die here and looked at the outcome. For you the probability it is a 6 is 1/6. For me is isn’t 1/6. Same object!
- deltasevennine 4y agoFor you it isn't 1/6 but for him it is. From your perspective can you derive from the knowledge you have why that for him the probability is 1/6? And I mean derive as in derive the mathematical probability from all your knowledge about physics and the dice to explain why the lack of knowledge appears to him as a probability. This is the essence of my question. We assume it. Probability is taken to be true for no reason, similar to how we just assume logic to be true.
- BOOSTERHIDROGEN 4y agoAny statistics book that have similar approach like this ?
- kqr 4y agoThis was much more common in the first 2/3 of the 20th century than it is today. I can strongly recommend Theory of Probability (de Finetti, compiled 1970 based on work de Finetti did as early as 1930s) and Foundations of Statistics (Savage, 1972) – the latter leans a bit on the former but expands on it with useful perspectives. I recommend you start with these basic theoretical books to get a sense of what it's all built on. But then if you want more practical advice about how to handle things, books on sampling theory tend to hit a sweetspot between theory and practise, in my experience. I like Sampling Techniques (Cochran, 1953) and Sampling of Populations (Levy & Lemeshow, 2013).
- BOOSTERHIDROGEN 4y agoThanks for the sampling techniques.
- graycat 4y agoSorry, Feynman, whatever else he did, on probability he gets a grade of flat F. Here is why: In his book Lectures on Physics he states that a particle of unknown location has a probability density uniform over all of space. No it doesn't. No such density can exist. Done. Grade flat F. I tried to be a physics major but could not swallow all the daily really stupid mistakes such as this one by Feynman I got each physics lecture and I didn't have time both to learn the physics AND to clean up the sloppy math. So, I majored in math. As I learned the math, from some of the best sources, I came to understand just how just plain awful the math of the physics community is. Then in one of the Adams lectures on quantum mechanics at MIT I saw some of the reason: The physics community takes pride in doing junk math. They get by with it because they won't take the math seriously anyway, that is, they insist on experimental evidence. So, to them, the math can be just a heuristic, a hint for some guessing. Students need to be told this, in clear terms, early on. It went on this way: In one of the lectures from MIT a statement was that the wave functions were differentiable and also continuous. Of COURSE they are continuous -- every differentiable function is continuous. The lectures made a total mess out of correlation and independence. It looks like Adams does not understand the two or their difference clearly. There was more really sloppy stuff around Fourier theory. I got my Fourier theory from three of W. Rudin's books. It looks like at MIT they get Fourier theory from a comic book. I got sick, really sick, of the math in physics. Feynman on probability is just one example.
- clircle 4y agoWhat is the problem with density on space?
- graycat 4y agoTake one cubic inch. Let the probability the particle is in that cubic inch be p. Then take integer n >= 2 / p cubic inches. Then the probability that the particle is in those n cubic inches is np >= 2 > 1 greater than 1, a contradiction. Done. One well considered and informed explanation is that the physics community abuses its students.
- 4y ago
- hackandthink 4y agoEverybody knows Feynman, who knows Jaynes? https://quantumfrontiers.com/2018/12/23/chasing-ed-jayness-ghost/ https://quantumfrontiers.com/2018/12/23/chasing-ed-jayness-g... Jaynes about Probability in Science: https://www.cambridge.org/gb/academic/subjects/physics/theoretical-physics-and-mathematical-physics/probability-theory-logic-science https://www.cambridge.org/gb/academic/subjects/physics/theor...
- vmilner 4y agoWell, I do... :-) Less facetiously, I think Jaynes is becoming better known as Bayesian techniques have become more mainstream.
- mananaysiempre 4y agoJaynes is brilliant, but you ought to take care when reading him. For example, AFAICT his digression on Gödel’s theorem in Logic of science is complete nonsense, and the rant against Kolmogorov-style axiomatization of infinite probability spaces in same isn’t much better.
- kgwgk 4y ago“From many years of experience with its applications in hundreds of real problems, our views on the foundations of probability theory have evolved into something quite complex, which cannot be described in any such simplistic terms as ‘pro-this' or ‘anti-that'. For example, our system of probability could hardly be more different from that of Kolmogorov, in style, philosophy, and purpose. What we consider to be fully half of probability theory as it is needed in current applications – the principles for assigning probabilities by logical analysis of incomplete information – is not present at all in the Kolmogorov system. “Yet, when all is said and done, we find ourselves, to our own surprise, in agreement with Kolmogorov and in disagreement with his critics, on nearly all technical issues. As noted in Appendix A, each of his axioms turns out to be, for all practical purposes, derivable from the Polya–Cox desiderata of rationality and consistency. In short, we regard our system of probability as not contradicting Kolmogorov's; but rather seeking a deeper logical foundation that permits its extension in the directions that are needed for modern applications.”
- wodenokoto 4y agoIf you scroll to the top there's a camera icon. If you click, you can view photos from the actual lecture