QED: The Strange Theory of Light and Matter by Richard P. Feynman

QED: The Strange Theory of Light and Matter Reviews

• 
  Manny

  Sometimes, it's too late, but that makes you do it better. You probably imagine that this book is a physics text. Well, it is, but that that's not what it really is. Really, it's a love letter to a dead woman. Feynman says in his introduction that his friend Alix Mautner had always wanted him to explain quantum electrodynamics to her so that she could understand it, and he'd never gotten around to doing that. Now it was too late. But, somehow, you can see that that only made him want to do it, not just well (he did everything well), but perfectly. If the book was perfect, that would make up for its appearing after Alix was no longer around to read it. It may seem like an odd formula, but it worked for Dante, and it also worked for Feynman.
  
  The rest of this review is available elsewhere (the location cannot be given for Goodreads policy reasons)
  
  
• 
  Tara

  My reaction upon finishing this book:
  
  
  
  (Any excuse for a Breaking Bad reference.)
  
  Seriously, though, this is one of the best pop science books I’ve yet encountered. I read Surely You're Joking, Mr. Feynman!: Adventures of a Curious Character last year, and was thoroughly impressed by Feynman’s animated personality and his passion for physics. Now I find myself even more impressed by his exceptional teaching ability. QED: The Strange Theory of Light and Matter is a collection of 4 lectures he gave to the general public on the subject of quantum electrodynamics. The book is intended for laypeople, is written in very accessible language, and provides “Feynman diagrams” instead of advanced mathematical formulae. A rather lengthy summary of these fascinating lectures follows. If you don’t want any spoilers, or whatever you want to call them, then skip ahead to the final paragraph.
  
  The first lecture deals with photons, and how light behaves like particles. This is discussed in detail w.r.t. the partial reflection of monochrome light by glass. There’s already some fascinating shit right here, let me tell you! See, physicists can’t predict which photons will get reflected and which will pass through the glass. All they can tell you is the overall probability that it will happen. In other words, “identical photons are always coming down in the same direction to the same piece of glass,” and this somehow winds up “producing different results” each time. Who knew that “partial reflection by a single surface” was a “deep mystery and a difficult problem”?! Bizarre.
  
  Feynman then teaches us how to calculate the probability of photons bouncing off either the front or the back surface of sheets of glass of varying thickness. The lecture concludes with a discussion of iridescence (the colors produced by the reflection of white light by two surfaces). Neat-o.
  
  In the second lecture, Feynman uses QED to explain why, when light reflects off a mirror, the angle of incidence is equal to the angle of reflection. This is weirder than you might assume. (Actually, “weirder than you’d assume” sums up the entire book remarkably well!) The phenomenon discussed here is also the basis for diffraction gratings. Then he covers how light travels from air into water, and what causes mirages.
  
  Feynman goes on to explain why light appears to travel in straight lines. Incredibly, it behaves as such only when you give it enough wiggle room, so to speak. For “when you try to squeeze light [or restrict its path] too much to make sure it’s going in only a straight line, it refuses to cooperate and begins to spread out.” This is not altogether dissimilar to the behavior of surly teenagers. Perhaps we can reasonably refer to them as “little rays of sunshine” in an unironic fashion from now on! :D Bad joke, sorry. Anyway, the manner in which focusing lenses work is next revealed, and the lecture concludes with how quantum theory calculates the probability of compound events.
  
  The third lecture introduces electrons, which behave similarly to photons: somewhat like waves, somewhat like particles. (Feynman jokes about “wavicles,” a term I actually love to death, and will enthusiastically champion from now on!) We learn of the three basic actions from which all the phenomena of light and electrons arise: 1) photons rollicking about, 2) electrons rollicking about, and 3) electrons emitting or absorbing photons. As per the first item, we learn that “light doesn’t go only at the speed of light.” So yeah, that happens. It’s anarchy, I tell you! Madness! And the third action is even stranger. Hint: time travel may or may not be involved. Oh, you beautiful, depraved little positrons, you.
  
  Next, Feynman covers how electrons behave in atoms. He re-examines the partial reflection of light from glass in far greater detail than he did earlier, and we can now see why the former simplification was in fact warranted. (We previously treated light as reflecting from the “front” and ”back” surfaces of a sheet of glass, as opposed to what light actually does, which is to be scattered by the electrons inside the glass.) This scattering is also the reason light appears to move more slowly in glass or water than it does in a vacuum or in air. Also of interest is how lasers work: photons tend to go to the same point in space-time. (These lunatics are predisposed to travel in packs!) It turns out the reverse is true for electrons. Their aversion to one another is known as the “Exclusion Principle,” and helps explain chemical properties of atoms.
  
  Before finishing the lecture by discussing polarization, Feynman examines the complexity of the magnetic moments of electrons. This is fairly bananas, even considering the fact that the entire book is pretty much out to lunch. Here is what can happen: an “electron goes along for a while and suddenly emits a photon; then (horrors!) it absorbs its own photon. Perhaps there’s something ‘immoral’ about that, but the electron does it!” (You really have to love his sense of humor.) I’ve included some Feynman diagrams which depict this wanton immorality:
  
  
  
  The fourth and final lecture deals with some problems associated with quantum theory. It also looks at the relation of QED to the rest of physics, and includes a discussion of fundamental particles such as quarks and gluons, to name but a couple.
  
  Overall, this short book is packed full of mind-blowing information. I really appreciated all of the helpful diagrams that illustrate the very peculiar concepts under discussion. Also, Feynman is an excellent teacher. I just loved his occasional bursts of exuberance and humor. His enthusiasm for his subject is irresistible, his subject itself truly extraordinary.
• 
  Prerna

  Imagine having such a powerfully visual thought process that when you look at complex electrodynamic interactions at the quantum level and all the tedious, long equations that need to be solved to compute the probability of their occurence, you think "Actually, you know what? It's all a bunch of arrows going in and coming out. Some arrows are straight, some of them are wiggly, some of them even travel backwards in time, but they're all arrows nonetheless." Imagine starting with a toy model of this, sketching various quirky almost arts-y diagrams and immeasurably simplifying quantum electrodynamics for generations of physics students to come. Can you? I definitely can't.
  
  Of course this is brilliant, but what stands out and I daresay even more, is the elegance of Feynman's simple writing. There are no grand words here, no pompous pretensions of technical terms but no false modesty either. There are arrows and there are simple everyday words. Reading this book is like a revelation, of understanding how deeply exquisite and how deceptively complex nature is. You also understand how it's all a problem with semantics, we don't have the language to understand nature. But Feynman here has quirky pictures and that makes him a physicist like no other.
  
  This is a must read, if only to feel the satisfaction that you don't need to be a theoretical physicist to understand nature at its simplest. All you need is a pencil, a paper and minimal drawing skills. And every once in a while you need a brilliant theoretical physicist to guide you. Thankfully, we have Feynman.
• 
  Roy Lotz

  I love this area of physics and I think it’s wonderful: it is called quantum electrodynamics, or QED for short.

  
  I love this book and I think it’s wonderful: it is called QED: The Strange Theory of Light and Matter, or QED for short.
  
  I feel as though I’ve been searching for this book for a long time, and now I’ve finally found it. In scarcely 150 pages, Feynman takes you inside the logic of this famously obscure subject. What was before unintelligible is breezy in Feynman’s hands. What had before seemed impossible and bizarre of the physical world—particles behaving like waves, going back in time, eluding measurement—is, in Feynman’s presentation, just Nature being goofy.
  
  So here’s the mystery. Newton proposed, in his Opticks, that light is corpuscular, or comes in little packets like raindrops. But it was later observed that light can interfere with itself, so it must be a wave. (For a while, English physicists were loath to admit that Newton could be wrong.) Then experimenters ran into trouble again when they discovered that if you take an extremely dim light and aim it at a detector, you don’t get one continuous signal, but a series of beeps and pauses like Morse code. So it appears that light comes in packets after all. But wait! In certain circumstances, if you shoot these particles one-by-one, you get an interference pattern like a wave. So light was both a particle and a wave? How was that possible?
  
  Feynman begins by saying that this question—How is this possible?—isn’t the right one to ask. Physics is an experimental science, so its task is to come up with a theory that will make predictions that agree with experiments, not to resolve philosophical paradoxes. In this book, that’s just what he does: he explains what physicists are doing when they are making these predictions. To do this, he must delve into the math. But he does not wish to explain how his graduate students do it (which wouldn’t be feasible in a book of this size, anyway), but to explain what is going on behind the scenes when they do these calculations. It’s like teaching children to add with pebbles rather than on paper.
  
  Feynman begins by telling us that, in quantum physics, we calculate probabilities, not certainties. That’s a bit disappointing, but that’s the way nature is. So when a physicist is calculating the probability that a photon will pass through or reflect off a pane of glass, they use “probability amplitudes,” which can sometimes reinforce and sometimes cancel one another. With this method, we can predict how many photons out of 100 will reflect, and how many will pass through. Not only that, but we can also deduce the wavelike properties of photons interacting with electrons to astounding levels of accuracy—so accurate that if you were measuring the distance from New York to Los Angeles, the uncertainty would be equivalent to the width of a hair. So as far as scientific theories go, QED is pretty dang good.
  
  But what are “probability amplitudes” in reality? It seems a bit cheap at first, like Feynman merely found a clever way to talk about particles as waves without having to use the word “wave.” Feynman describes how to calculate the answer by picturing the particle as having a little clock hand that spins extremely fast, giving you an angle. In the end, two arrows (the amplitudes) are added up, the result is squared, and there’s your answer—a percentage. But what is really going on down there when the photon is traveling from the light source to the detector? What is happening before our measurements? Surely, there are no clock-hands attached to the particles. What's the mechanism behind all this?
  
  Of course, this is the kind of questioning that Feynman discourages. In his words:
  

  So this framework of amplitudes has no experimental doubt about it: you can have all the philosophical worries you want as to what the amplitudes mean (if, indeed, they mean anything at all), but because physics is an experimental science and the framework agrees with experiment, it’s good enough for us so far.

  
  So, really, there’s no way of knowing what’s going on before the particle is detected, since it is, in principle, undetectable. And in science, only things that can be measured are real. All of the stuff used to obtain the answer is just an intellectual apparatus, a tool for calculation.
  
  Yet it’s hard to be as content with this as Feynman. If you wanted to learn how a car works, you’d want to know what’s going on in the engine, the transmission, the steering and braking. If somebody told you, “It works by turning the key and stepping on the gas,” you’d feel like you were cheated. But this is what we must do in QED. Nature doesn’t allow us to look under the hood. We can step on the gas and the thing moves; we can come up with an equation that helps us predict how fast the car will go depending on how much we press on the pedal. But what makes it go? Who knows? As Feynman said:
  

  It is my task to convince you not to turn away because you don’t understand it. You see, my physics students don’t understand it either. That is because I don’t understand it. Nobody does.
• 
  Max

  This book contains four lectures given by Nobel Prize winning physicist Richard Feynman at UCLA in 1983. Feynman was a leader in the path integral formulation of quantum electrodynamics (QED) for which he won a Nobel prize. These lectures are intended for the non-scientist, but are best suited to those with a deep interest in the subject and the patience to wrestle with some complex ideas. The introduction to the 2006 edition puts this book of lectures halfway between a popular science book and a textbook. QED is a quantum field theory that describes the interaction of light and matter. To explain this, Feynman begins with the partial reflection of light by glass. Feynman shows us how to determine the probability of each photon being reflected. Rather than take us through complex numbers and integral calculus, he uses a system of arrows. The arrows’ length and direction are summed to provide an answer. While this seems straightforward at first, each ensuing example is more complicated requiring more steps. Along the way we learn about the strange world of photons and electrons and how QED is able to describe their interaction. At the end Feynman gives his takes on related subjects such as quantum chromodynamics. His well noted irreverent manner comes through in all the lectures. Feynman uses plain language that can be entertaining, at times flippant and self-deprecating. Feynman’s arrows accompanied by many illustrations and his famous diagrams make a difficult subject more accessible, but I did not find this to be a light read. Without prior familiarity with the topic, I would have been lost. But I was fascinated by his approach that uniquely complimented other books I have read about quantum field theory.
• 
  Kevin Lopez (on sabbatical)

  Although a bit more conceptually demanding, technically trying and theoretically abstract than some of his other, more widely-read pop-science books (I’m thinking primarily of the bestselling “Six Pieces” duet published in the 1950s—a titularly symmetrical though somewhat uncreatively named duology, comprised of the now-classic tomes, “Six Easy-, and “Six Not-So-Easy Pieces”), “QED: The Strange Theory of Light and Matter” is still an engaging and elegant expostulation of some of the most thorny and mind-bending theories of the twentieth century—and which still challenge the brightest minds of the twenty-first—punctuated by Feynman’s characteristic exuberance, creative outside-of-the-box thinking, and pure, childlike wonder at the mysteries of Nature that always come across so clearly in his prose. Feynman’s unabashed aim of educating the broader public; his very un-professorial tone; his interspersed jokes and common touch; surmounted by his folksy, metaphor-rich explanations may bother the more fastidious and advanced (not to say snooty!) reader who may be looking for and expecting something closer to a post-graduate level seminar from this eternally-adolescent Nobel laureate, but the fact that a minuscule portion of the physics contemporary to Feynman’s writing of “QED” (and, in case you’re wondering, the acronym in the book’s title stands for Quantum Electrodynamics—definitely not for “quod erat demonstrandum,” the better-known, slightly arrogant mic-drop Latin phrase shouted gleefully upon pummeling one’s interlocutor in scientific or philosophical argument) really isn’t much of a strike against the book—especially for anyone interested not only in science, but also in the history (and to a lesser extent the epistemology) of science. “QED” is a unique time-capsule of a book written by one of the most unique and influential geniuses of the 20th century. And of course, it’s also a typically entertaining, informative, and adept piece of Feynmanian explication. As Feynman himself once said, he didn’t believe that he could have fully absorbed and understood a theory until he was able to effectively explain it to a class of undergraduates (Feynman is chock-full of these sorts of casually brilliant and insightful maxims).
  
  The most salient point of all, though, is the inherent value in reading a book like “QED”. I found the experience both deeply fascinating and profoundly informative, which has been my reaction to everything else I’ve ever read by Feynman. And I expect that reading this book will enhance most anyone’s overall understanding not only of 20th, but 21st century physics—in particular quantum electrodynamics. It generously imparts to the reader both the complexity and the innate beauty of our extraordinary cosmos; of the still-mysterious and hotly debated significance of the preternatural success of mathematics, and the superhuman ability it imparts to human scientists who wish to define and delimit, and then structure of the cosmos—to successfully predict the far future, as well as retrodict the distant past; of the epiphanic simplicity and intellectually harmonious perspective that only a mind like Feynman’s (even decades after his death) can still offer any reader with a curious and open mind.
• 
  Matt

  
  
  
  
  I took this photo when I was about half way through the book. It shows a picture of a CD [click to enlarge]. It's been illuminated by an ordinary office lamp and the flashlight from my camera. I knew about this "rainbow" effect for a long time, but I didn't know exactly how it is created. This book gives some answers.
  
  To write a successful book like QED (short for Quantum Electro-Dynamics) two prerequisites are required: 1) The author must know a great deal about the subject matter, and 2) He must love his work. Only then it is possible to explain the theory of QED to laypersons like me. Richard Feynman obviously fulfilled both of these conditions. For one he virtually "invented" Quantum Electro-Dynamics (and received the Nobel Prize for physics for it in 1940) and secondly you can clearly sense his deep affection for the nature of objects and processes in the realm of the very very very small things, that is the quantum world.
  
  Instead of bothering the reader with mathematical formulas like this...
  
  
  
  ...Feynman developed a rather ingenious way of explaining the interaction of light particles (photons) and electrons (and later other particles too) using diagrams like this:
  
  
  
  All those little arrows are of the utmost importance because they represent what is called "probability amplitudes" for an event. The longer the arrow the more likely the event. In fact all we have to do–in theory–is to draw all possible little arrows on a piece of paper to explain almost any phenomenon concerning light that we can observe in nature. Don't ask me why that is. In fact even Richard Feynman couldn't answer the "why", only the "how". That's the charming thing about quantum theory. It has to be pointed out that this way of dealing with quantum effects is not a deviation from the truth (as far as anyone knows the truth). Other popular science books make things too easy and thereby achieve simplicity only for the price of a somewhat distorted truth. Not so here!
  
  But don't think that this drawing of arrows (and then later in the book what is called the "Feynman diagrams") is very simple. There are quite some things to consider, and the text is pretty dense. Anthony Zee, a Chinese American physicist, wrote in his introduction to QED:

  [...] you must mull over each sentence carefully and try hard to understand what Feynman is saying before moving on. Otherwise, I guarantee that you will be hopelessly lost. It is the physics that is bizarre, not the presentation.

  I have to agree to that. Whenever I came to a point where Feynman lost me I skipped back a few pages and read it again....and again, until I made sense of it (as much sense as was possible for me). I think I understood the majority of this book, I just haven't internalized it. Not yet anyway. Maybe I have to read the whole book again after a couple of weeks. Until then I keep a quantum of solace that we (the humankind) are by now advanced enough to understand what make these cool "rainbow things" on CDs.
  
  I highly recommend this book to anyone interested in the very foundation of what makes the world work the way it does.
  
  
  
  This work is licensed under a
  Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
  
• 
  Vladys Kovsky

  It's amazing what Feynman is attempting here. He tries to fully explain quantum electrodynamics to people with no background in physics. I am not sure he succeeds, I will have to check it by giving this book to someone who fears the subject.
  Even for people like myself, who have been trained in physics, these lectures are useful. The way Feynman clearly communicates the concepts while not diving into mathematics is brilliant. I think these lectures are must read material for aspiring physicists. They show the big picture which is often buried in mathematical detail and remains inaccessible for many students.
• 
  إيمان

  
  
  
  أربعة محاضرات ألقاها فينمان في نيوزيلاندا قصد إيصال مفاهيم الكهروديناميكا الكمية لغير المختصين. و قد تمت طباعة هذه المحاضرات كهدية لروح "أليكس ماوتنر" التي كانت متيمة بالنظرية الكمية و التي كانت تطلب منه تفسيرها لها لكن القدر شاء أن ترحل قبل أن ينفذ طلبها. ينطلق فينمان من التساؤل عن ظاهرة الإنعكاس الجزئي ليتناول في المحاضرة الثانية الطبيعة الإحتمالية لحركات الإلكترونات و علاقة ذلك بالإنعكاس ثم ليتعمق أكثر في الفكرة و يشرح طريقة تفاعل الفوتونات مع الكترونات المادة و ما يتبع ذلك من خصائص هذه النظرية التي كان أحد روادها النظريين (نال جائزة نوبل رفقة جوليان شفينجر وسين توموناجا بسبب إسهاماته فيها).
  
  
  
  و في حال لم تجعلك المفاهيم الموجودة في المحاضرة الثالثة أو ما سبقها (أقول ذلك و أنا المتعودة على ميكانيكا الكم) تعدل جلستك أكثر من مرة و تحدق في الفراغ مشدوها من سحر ما قرأت، فإن المحاضرة الرابعة بكل تأكيد لا تخلو من المتعة المعرفية ففيها بالإضافة إلى نقائص الكهروديناميكا الكمية حتى لحظة إلقاء المحاضرت، مقدمة رائعة سهلة و بسيطة لمجال أراه و يراه الكثيرون مثلي الأكثر تعقيدا في الفيزياء الحديثة و الحديث هنا عن فيزياء الجزئيات.
  
  
  
  يبهرني فينمان مرة أخرى بقدرته الكبيرة على إيصال المفاهيم الفيزيائية دون العودة إلى الرياضيات ما خلا بعض الأمثلة الضرورية و التي لا تتطلب الكثير من المعرفة الرياضية. طبعا أي شخص درس الفيزياء في عالمنا العربي سيعرف أن الإنطلاق غالبا يكون من القاعدة الرياضية للتفسير...شخصيا لا يمكن أن أجد تفسيرا غير كون الأستاذ غير ملم بالمفهوم أصلا و أن واضع المنهج لا يهدف إلى خلق جيل مفكر و أن محاضراتنا الجامعية في غالبها جوفاء تخلو من العمق المعرفي...خمس نجمات و أرغب حقا في إضافة سادسة لو كان ذلك ممكنا ...إلى لقاء آخر سيد فينمان
  
  
  
  
  
  14/09/2020
  
• 
  AnnMarie

  You could call me a science groupie. I put on Cosmos while I clean the house, snatch up Michio Kaku's books like they won't be there tomorrow, know all the words to every Symphony of Science song ever, and follow Neil deGrasse Tyson on Twitter--but that doesn't mean I know the first thing about real science. I couldn't solve a linear algebraic equation even if the world depended on it (sorry, world). Instead, I revere famous physicists from afar while most women my age drool over movie stars like What's-His-Face. You know the one. That really hott one.
  
  Anyway. Richard Feynman is definitely in the top five on my list of favorite physicists. (Yep, I have a list. Expect nothing less from a girl who named her cat Sagan.) I love Feynman's sense of humor and his whimsical world-view. He may be gone, but he's not forgotten. So when I had a stupid question about light, I figured it was high time I read his book on the subject. My stupid question goes like this: Why is it that, when you turn off a light, the room immediately goes dark? Where does the light go? Why doesn't it bounce around the room for a bit before dispersing? If light is everywhere, why is the universe so dark?
  
  Well, this book didn't really help me answer those questions. If Feynman taught me anything here, it's that light is the honey badger of particles: it does what it wants, and leaves tiny arrows in its wake. Or something. I'm not sure.
• 
  Paul

  Richard Feynman's friend Alix had asked him to explain Quantum Electrodynamics (the titular QED) to her in a way a layman could understand many times. Heartbreakingly, it wasn't until her death that he actually found the time to write a series of four lectures that would do just that. This book is a (slightly edited) transcript of those four lectures.
  
  Feynman writes for the layman without ever being condescending and his famous sense of humour shines through. He makes this subject both approachable and fascinating. I've studied much of the content before in physics classes and other books but Feynman has made me look at it in a different way. In fact, I can safely say that this book has significantly changed the way I think about reality.
  
  If that's not worth five stars, nothing is. If you've not read this book before, do yourself a favour and give it a bash.
• 
  Edward

  QED: The Strange Theory of Light and Matter is an outstanding book on a subject that is often overlooked or glossed-over in many popular physics books. Feynman does a deep dive on Quantum Electrodynamics: a theory that deals not only with the various interactions between light and matter, but which can be applied to every area of physics with the exception of gravitation and nuclear physics.
  
  The theory of QED is fascinating, both in its explanatory power and its elegance. Using only a handful of conceptual tools, and working with just two fundamental particles - the photon and electron - it can describe phenomena as varied as reflection and refraction of light, changes in the speed of light through different mediums, quantum interference, lenses (I found the application of QED to this seemingly mundane property of glass to be particularly mind-blowing), and even suggests how all the diverse properties of the elements arise from only three basic actions performed by these two fundamental particles.
  
  To say that this book changed the way I see the world is only a slight overstatement - it has certainly opened my eyes. QED is an absolute must-read for anyone with an interest in physics. Feynman takes great pains to present the theory in a clear and logical way, and while the subject is challenging, it is utterly comprehensible from cover to cover. This is by far the best popular science book I've read in a long time - I cannot recommend it highly enough.
• 
  Jose Moa

  Wonderful,Feynman is a genius of popularization,without a mathematical expression has achieved the goal of give the rigurous quantum electrodinamics fundaments of geometric and physical optics,is to say,refraction,refraction index,reflexion, difraction ,converging lenses,classic Fermats principle of minimun time in path light and so on.
  
  He uses arrows to represent complex numbers in complex plane,with its modules and phases and uses sums and products of histories in the propagation of the photon as sums and products of this arrows to obtain the final amplitude.
  Also he explains the bizarre and incomprehensible behavior of the photon as it explores all ways each one with it own phase and in the sum the major contribution is of similar to classical path of mínimum time.
  Also the strange property of a photon or electron that in the doublé slit experiment is able of have interference with itself.
  
  In the next chapter,explains his diagrams,how to calculate each piece,the propagation piece and the vertex piece,also the radiative serie of corrections,succesful in explanation of the magnetic moment of the electron and also with a diagram explains very well as a positrón can be viewed as a electron going backwards in time.
  
  In the last chapter explains the only ugly aspect of the theory,the problem of the infinities and the renormalization solution,ends with a brief account of the standard model.
  
  He also makes a deep reflection in the sense that the complex amplitudes has no physical meaning and that the deep work of the theory is incomprehensible,the idea is that we dont know the true working of reality,only knows the model we make,the reality has a behavior as the model predicts but no more,our model is a simulation of reality and we only can know that simulation.
  
  A masterpiece of science popularization,strongly recomended to those that want to have a taste of the deep conceps and strangeness of the quantum world reality
  
  
  
  
  
  
• 
  Bernardo

  In the beginning of QED, Richard Feynman says that people are always asking physicists about the new findings of a grand unified theory. He feels they should also be asked about known and confirmed theories instead of undercooked and partially analyzed ones. So he decides to speak about the “well dissected and marvelous” theory of QED. The theory describes the interactions between photos and electrons, space-time and probabilities, among others.
  
  The book is based on four conferences given by Richard Feynman in the 1980s. These were done in memory of a friend of his who had passed away, Alix Mautner. She had a career in english literature but was curious about physics and often asked him about quantum mechanics. He never had the chance to explain her the theory of quantum electrodynamics (QED), for which he was awarded a Nobel prize (alongside Schwinger and Tomonoga), and which he described as “the jewel of physics”.
  
  It’s remarkable how much content there is in this book, having only 150 pages or so. The explanations are easy, illustrated with a great amount of examples and figures, and may seem too simple at times, until Feynman shows the grand picture and demonstrates how brilliant physics is. He had the ability to make topics which could be seen as too complex become accessible.
  
  I was delighted to read this book, as there aren’t many books for non-physicists that mention QED. Feynman’s mix of humour and humility just improves the experience.
  
  This is a wonderful book and one couldn’t ask for a better teacher than Feynman. He reminds us that physics can be fun and inspiring.
• 
  Yann

  
  
  Ce livre propose de vulgariser la théorie scientifique la plus exacte dont nous disposons avec laquelle il est possible de modéliser la lumière, la matière et leurs interactions réciproques, à savoir la mécanique quantique. Développée au cours du siècle précédent, elle se fonde sur des principes qui brusquent le sens commun, comme la dualité onde-corpuscule ou le principe de superposition, car il n'est plus possible de s'aider d'analogies à partir de notre expérience pour en rendre compte sans prendre le risque de commettre des erreurs, et seul la maîtrise de l'outil mathématique en rend compte fidèlement. C'est donc une gageure que d'expliquer ces mécanismes avec l'aide de petits schémas et dessins, tels que l'entreprend l'auteur.
  
  Il s'y emploie cependant, illustrant par exemple des phénomènes aussi familiers que la réflexion de la lumière dans un miroir, sa réfraction dans l'eau ou le verre, ou encore le fait qu'une partie est transmise et une autre réfléchie. On aborde également la cause des magnifiques irisations diaprées qui ornent la surface des bulles de savons, les ailes des papillons ou la face lisibles des compact-disc. Tout est ramené au calcul d'une somme de probabilités représentée ingénieusement par de petites flèches mises bout-à-bout. Pour autant, je ne suis pas certain qu'il parvienne à rendre tout aussi clair qu'il le souhaite. La durée nécessairement limitée des exposés dont ces textes sont la transcriptions ne permettent pas d'en éclairer toutes les subtilités.
  
  L'humour et la modestie avec laquelle l'auteur traite le sujet rend la lecture agréable, mais il me semble qu'en dépit des immenses efforts déployés par l'auteur pour rendre son sujet accessible, l'essentiel restera obscur pour le plus grand nombre, à moins de nourrir un intérêt particulièrement fort pour le sujet. J'ai néanmoins beaucoup apprécié que ce livre aiguise ma curiosité, et exerce mon émerveillement pour la beauté de la Nature.
• 
  Sebastian

  Throughout the years of reading both popular and less-popular science, I’ve kind of steered clear of Richard Feynman. The main reason is that what others describe as a “larger than life persona” I tend to describe as really bloody annoying, what with his bongos and womanizing and oh-so-clever quips where he always gets the upper hand with the old and rusty physics establishment. Having now fought my way through QED, I can see that this may have been a mistake. My annoyance with his autobiographical works has kept me away from some truly gorgeous scientific writing.
  
  The thing is, I’m not sure if it is even possible to explain quantum mechanics properly without all the higher math, but if it is possible, this is likely the only proper way – with a lot of “this is how it is, and don’t ask why, because even we, physicists, do not know”, and a lot of weird and unexpected analogies, such as his substitution of “little clock hands” for the harmonic oscillator that pops up every which way in QM. The only problem I had was that knowing the “proper” theory it took me a while to fully intuitively accept and adopt his “tiny clocks running” description and match it with the complex numbers/oscillators he is describing in this roundabout fashion. However, once that clicked into place, his descriptions of simple everyday phenomena, such as reflection and diffraction, the two-slit experiment, and later on the interaction of electrons and photons, really popped off of the page and sort of “broadened the groove” wherein all the counter-intuitiveness of QM is trying to get a foothold in my brain.
  
• 
  Quiver

  
  That's my position: I'm going to explain to you what the physicists are doing when they are predicting how Nature will behave, but I'm not going to teach you any tricks so you can do it efficiently.
  

  
  
  Starting from the idea of photons as particles of light, Feynman develops a nontechnical, easily understandable theory of basic quantum electrodynamics, or QED. He uses it to give modern explanations of everyday phenomena such as reflection and refraction, before delving into the basic of electron-photon interactions (the so-called Feynman diagrams) which underly all phenomena except gravity and nuclear physics. No maths is involved, though he uses pictures creatively. In the final lecture, he talks about the experimental aspects and the cutting-edge developments of his time (gluons, quarks, chromodynamics etc).
  
  If all sciences were so well explained in so few words with so much good will and humour, the ideas and intuition behind humanity's greatest achievements would be accessible to a much wider audience.
• 
  Emilio

  Richard Feynman, más allá de haber sido uno de los mejores físicos del siglo XX, y de haber sido premiado con un Nobel por esto, fue un excelente profesor; y el mundo lo conoce muy bien por esto.
  
  Este libro es otra gran muestra de ello; es el compendio de una serie de conferencias que estaban destinadas para explicar Física Cuántica a la esposa de un amigo suyo (que, por supuesto, no era física), así que es una obra excelente para introducirse o incluso para profundizar en el mundo de las partículas subatómicas. Las conferencias se enfocan especialmente en los fotones y en los electrones, y en como siguiendo tres simples reglas logran explicar prácticamente todos los sucesos que ocurren a tal escala; y para hacerlo, recurre nada y nada menos que al "simple" proceso a través del cual la luz atraviesa un cristal.
  
  Una lectura para CUALQUIERA que quiera conocer un poco (más) sobre lo que para muchos parece estar fuera de alcance: la Física Cuántica.
• 
  Ami Iida

  、Chapter 3; electrons and their interaction will be a clue to solve all the phenomena for the universe.
  It's the absolutely essential reading physics book for everyone .
• 
  Degenerate Chemist

  This is the last of the books I bought in 2021 that are less than 200 pages long. So I can finally move on to books in the 400 page range.
  
  This is the first Feynman I have ever read and I don't know if I will read him again. I found his style frustrating and I got irritated with the writing, wishing he would just get to the point or at least lead with the point he was trying to make.
  
  I would be halfway through a lecture and realize, oh this is about the wave- particle duality or this is about the uncertainty principle. And I just feel that if someone is new to the topic this style of writing is not going to be in the least bit helpful.
  
  -2 stars for annoying me
• 
  Joshua Nomen-Mutatio

  It's all arrows, man. All about arrows. Physics is not a subject I have a terribly good grasp on mainly because my eyes glaze over at the sight of advanced mathematical equations, however Feynman is a pretty great at making the complex subjects of particle physics and quantum mechanics intelligible to the layest of laypersons. Fortunately I also read this with able-minded people who translated the math into clearer ideas which of course opened things up to broader philosophical speculation--something I am pretty good with. The introduction to the book is also worth reading by itself at the very least.
  
  "I think I can safely say that nobody understands quantum mechanics."
  
  -Richard Feynman
  
  He was also a very funny and clever man who left behind
  a whole host of aphoristic gems, for instance:
  
  "A poet once said, 'The whole universe is in a glass of wine.' We will probably never know in what sense he meant it, for poets do not write to be understood. But it is true that if we look at a glass of wine closely enough we see the entire universe. There are the things of physics: the twisting liquid which evaporates depending on the wind and weather, the reflection in the glass; and our imagination adds atoms. The glass is a distillation of the earth's rocks, and in its composition we see the secrets of the universe's age, and the evolution of stars. What strange array of chemicals are in the wine? How did they come to be? There are the ferments, the enzymes, the substrates, and the products. There in wine is found the great generalization; all life is fermentation. Nobody can discover the chemistry of wine without discovering, as did Louis Pasteur, the cause of much disease. How vivid is the claret, pressing its existence into the consciousness that watches it! If our small minds, for some convenience, divide this glass of wine, this universe, into parts -- physics, biology, geology, astronomy, psychology, and so on -- remember that nature does not know it! So let us put it all back together, not forgetting ultimately what it is for. Let it give us one more final pleasure; drink it and forget it all!"
  
• 
  Dean Hamp

  I visited my brother a long time ago, when he was working on his Ph.D. in Physics. He tossed a small, innocuous-looking book to me and said, "Read this - its a complete brain-f**k. I've been hooked ever since. QED is, by far, the best piece of non-fiction I have ever read. It takes a long time for me to work though the concepts, and, as Feynman points out, nobody (including me) (especially me) truly understands Quantum Electrodynamics. But to begin with adding 'damned little arrows' and take that to an all-encompassing description of atomic theory, accurate to ten decimal places, in about 120 pages, so the likes of me can follow along, is the purest of genius. Bravo!
• 
  Sookie

  Its a subject that got glazed over when I was in Engineering and after that, a wiki entry that I frequented whenever I had questions. Feynman targets this book to, well, everyone. He holds your hand and shows how things work. Its a slow step by step process and if you invest some time, its highly rewarding and quite refreshing to be taught physics by a man who is long dead but doesn't really feel so when you read his words. You get transposed to his classroom as he explains basic concepts and the paradox surrounding the most natural thing in this world: light.
  
  Its a re-read which I enjoyed and will get on to re-reading some of his other famous lectures.
• 
  Bob Nichols

  In this series of short lectures, Feynman reduces (except for gravity and radioactivity) the whole of the universe to quantum electrodynamics or QED.* QED involves the relationship between photons (light) and electrons (matter), or quantum phenomena, the interaction of which (electrons emit/give up and absorb/get photons/particles of light) creates all of the atoms and elements in the universe.
  
  Feynman uses light’s refraction to illustrate the relationship between electrons and photons. To understand light, one has to lose “common sense,” he says. Light does strange things. We understand light not as specifically identified photon movement but in terms of probability. “I am not going to explain how the photons actually ‘decide’ whether to bounce back or go through [an opening]; that is not known,” he writes, and then adds, “(Probably the question has no meaning.)” Light seeks the fastest (shortest) route in its movement from A to B, but it borrows or uses paths that are adjacent. When light moves through a small opening, it also spreads out. In this regard, he writes that “light doesn’t really travel only in a straight line; it ‘smells’ the neighboring paths around it and uses a small core of nearby space.”Electron movement is strange as well. Electrons jump from one path to another and positive electrons (positrons) go backward in time. The book quickly gets technical. It is filled with Feynman diagrams and I can’t say I grasped much.
  
  Feynman is describing quantum phenomena but describing is different than understanding. “While I am describing to you how Nature works,” he writes, “you won’t understand why Nature works that way.” “My physics students don’t understand it….That is because I don’t understand it. Nobody does.” This makes his quote above, “Probably the question has no meaning,” particularly interesting as Feynman seems to be saying that, in the end, we can only describe how nature works, but not why it works the way it does. By extension, is Feynman saying that there are no ultimate explanations (e.g., God, Deist design) for the cosmos and how it operates, and that Nature just Is?
  
  *“The theory describes all the phenomena of the physical world except the gravitational effect, the thing that holds you in your seats,..and radioactive phenomena.” QED is “a horrible name,” Feynman concedes. The theory also describes what goes on inside the nucleus itself, which are the quarks and gluons, and involve some 400 (and counting) subparticles.
  
  
  
• 
  Lee

  This weekend just passed my flatmate's boyfriend was visiting. Being the inquisitive sort, at one point he asked me if I could explain the main results of my PhD thesis to him in terms he would understand. To my eternal shame my knee-jerk response was "No." But a few moments later I was to be found scrawling on a napkin, explaining rational points on curves, density arguments, counting functions, and concluding by using the word "generalise" far more times in one sentence than I was comfortable with.
  
  He seemed to follow my haphazard ramblings which is always enough to leave one chuffed. It's no secret to the science community that its biggest failing is an inability to communicate with and engage the public. The more esoteric the science, the trickier it is to convey it in terms that are both accurate and interesting. And, outside of pure mathematics, it doesn't get a great deal more esoteric than quantum mecahnics. So Richard Feynman's QED is laudable for, if nothing else, being about as understandable as is possible with this subject. There were times that the text lost me, but after giving it some thought I realised in each case that it was because I was expecting the quantum world to make sense, and to paraphrase my old Physics teacher: if quantum mechanics starts making sense, then you've stopped understanding it.
  
  Feynman's abilities as a scientific orator are pretty well known—one of my favourite videos on Youtube is a two-and-a-half minute video of Feynman sitting in a chair explaining
  how a train stays on the tracks. Seriously. Feynman's writing skills are apparently just as good, but I've not read any of his other books and this one is actually the edited transcriptions of four of his lectures, so his speaking prowess proves more useful here. And as if being fascinating, self-deprecating, and witty wasn't enough, he also manages to be quite touching. The lectures were the inaugural set in a series dedicated to Alix Mautner, an English major and long time friend of Feynman to whom the physicist had promised to explain quantum electrodynamics in terms she could understand. Sadly she died before he managed to do so, but the lectures here are, as he says, the ones he prepared for Alex, but that he could no longer give just to her.
• 
  Fraser Kinnear

  I think this is my favorite science book. This was in large part due to having Feynman's real voice in my head, as I've heard him often in recorded lectures and documentaries.
  
  The book is transcription of a few lectures Feynman gave on Quantum Electrodynamics (QED), a branch of quantum theory he and Dirac developed. Feynman introduces a few simple rules on how electrons and photons behave (which appear to be easy-to-digest analogs for vector calculus) and then off he goes, explaining the theory and how it describes an enormous amount of phenomena, such as the uncertainty principle, the how lenses and mirages physically work, how light scattering creates particles that travel backwards in time (via an antiparticle), why electrons stay in their orbits, lasers (exclusion principle). The only concept which I felt didn't come across quite so clearly was his discussion of spin.
  
  Once he is satisfied with the level of detail he gave to explaining QED, Feynman quickly runs through the rest of the menagerie of sub atomic particles, doing little more than listing them and noting that the toolkit from QED is useful in describing the interaction of quarks and gluons.
  
• 
  Jimmy Ele

  The particle view of physics and how Richard Feynman was able to explain all of the weird ways that light behaves was a thoroughly engrossing read. The intellectual feat that was performed by this man in creating a workable mathematics for the physics behind the way that light travels, and reflects is truly amazing. Using the simple concepts of rotation, spin, frequency, and depicting it all with some simple calculations involving arrows and simple algebra gave me a sense of awe at the simplicity of such a seemingly complicated subject. Even though I currently side with the field theory of Julian Schwinger, I must say that I can not blame anyone for using Q.E.D. as the model for their calculations.
  Overall, I had to place this on my foundation list, seeing as it gives me inspiration for explaining the seemingly complicated in very simple terms that can be easily understood by many.
• 
  Ivan Vuković

  A masterpiece of popular science. Feynman did what most authors can only dream of... He explained extremely difficult concepts from his path integral formulation of quantum mechanics and he even made renormalization sound intuitive... and he did it all without any equations, but without hand-waving.
  
  I feel like I really understood something... maybe that's because I'm a physicist and I know some of these things, but nevertheless I think Feynman explained everything so clearly that a layman could understand it without any difficulties.
  
  That's what a good popular science book should be like.
  Highly recommended, obviously. Don't you want to understand how our world works?