Six Not-So-Easy Pieces: Einstein's Relativity, Symmetry, and Space-Time by Richard P. Feynman

Six Not-So-Easy Pieces: Einstein's Relativity, Symmetry, and Space-Time Reviews

• 
  Bernardo

  This book is supposed to be a follow up of Feynman’s other book, Six Easy Pieces, which was sort of an introduction to physics. Here you will find a slightly more demanding book, as you’ll need some mathematics under your belt (pre-calculus should be fine). As the title says, the objective of this book is to introduce relativity, and Feynman does it in a superb and compelling way.
  
  Special relativity, in particular, gets the most attention. Feynman uses mathematics, analogies and experiments in order to provide an account of special relativity. The relations between relativistic energy and momentum are greatly described in a full chapter. I found it particularly interesting to get a closer look at the Michelson-Morley experiment and how it showed physicists that something was wrong with the existing idea at the time that space was filled with ether. As a bonus, Feynman not only speaks about symmetry in the context of relativity, but later on also relates it to parity, antimatter and symmetry breaking situations.
  
  General relativity is only accounted for in the last chapter of the six total chapters. Feynman does a great job in showing what curved space really means, ultimately getting to the relation between excess radius and mass. The principle of equivalence is very well described, with an experiment involving clocks in a gravitational field being used as an example and equations to complement. Unfortunately, most of general relativity and, as a consequence, Einstein’s field equation and equation of motion are not described mathematically, but only through words. As Feynman says, these are difficult to describe without a higher level of mathematics, usually only taught in later years of physics programmes.
  
  Besides being one of the greatest physicists of his generation, Richard Feynman was also a fantastic educator of science. It’s often uncommon to find scientists with both of these characteristics, as they don’t usually go hand in hand. To anyone who has never watched any of his interviews or lectures, I vividly recommend doing so. Even before reading any of his books. To understand the reasoning and wittiness behind his words it’s essential to imagine Feynman speaking with his New York accent, and his characteristic humor and directness.
  
  Feynman provides a compelling account of relativity. As usual, his clarity is evident, throwing away unnecessary complexities. Featuring experiments, both with and without apparatuses, and then demonstrating the results with equations, Feynman’s style just improves upon everything else. This book is a clear evidence of why the Feynman Lectures became so famous.
  
  Caltech has kindly provided the Feynman Lectures online for free, which you can access here:
  https://www.feynmanlectures.caltech.edu
• 
  Prerna

  I've been binge-studying lately. You know, lose-your-sleep-over-it-and-forget-to-eat kind of binge-studying. I barely even remember that I have a phone anymore because I make sure to keep it out of sight. I'd love to say it's because I'm passionate about physics and that the muses smiled upon me and I've been struck by great inspiration, but frankly it's only because my exams dates have been announced. And now it's like I've consumed mescaline after idling away the past year. I remember someone telling me about the Feynman technique of studying back in undergrad. I also remember being inspired. But now I'm tangled up in physics, and for the life of me I can't detangle, un-entangle, un-intertwine or whatever from it. I even dream of Greek letters even though I can't speak a word of Greek. How am I supposed to explain any of these obscure symbols to anyone? Fortunately, we have Feynman.
  
  This book consists of excerpts from his three-volume lectures on physics. I had no intention of reading it, but a friend lent me his copy a couple of months ago and so I used it as light reading. But it isn't for a layman, not without the previous lectures. I wonder if I'll ever read all the three volumes linearly and at a stretch, instead of just picking out whatever catches my fancy and skimming through it.
• 
  WarpDrive

  
  Let me start with a one-sentence summary: this is a thoroughly enjoyable little book explaining, in a beautifully intuitive and holistic way, the main core features of Einstein's relativity, without getting bogged down into too much mathematical detail.
  
  The target audience of this book is the interested layman with high school mathematics knowledge and a passion for physics: it falls into the particularly tricky (from a pedagogical standpoint) grey territory between popular science and real science. And Feynman manages, almost in a magical way, to strike a reasonable compromise, within so little space, between accuracy and level of detail on one side, and accessibility on the other side.
  
  Now, I have read more comprehensive works on relativity, with much more emphasis on its mathematical foundational underpinnings; and I can tell you that, if you are looking for something significantly beyond the introductory level, you will not learn much from this book. However, having said that, I would still recommend this book even to a more intermediate level reader, as the way how Feynman manages to get to the core of things with lucid rigor, and simplicity, and how he manages to holistically connect all the different aspects of the physics he is explaining, is something magic and a great pleasure to experience.
  
  Feynman is a wonderful teacher, who can get right to the core of topic with amazing clarity, and he has the gift to make even the potentially most complex concepts seem like the most obvious and commonsensical thing. Because of this, this book is highly recommended to whoever has a minimum knowledge of maths and wants to start looking at relativity from a more detailed perspective than what offered by many generic popular science books.
  
  To make the book perfect, I would have loved to see at least some treatment of the mathematical underpinning of relativity, which would have probably made, in my opinion, some critical parts of the book more clear and rigorous: for example, there is no mention of the 4-dimensional Minkowski vector space, and its tensor (metric) whose expression is represented by equation 3.9 of the book, (which is presented in the book as a "given"). And I would have loved at least a brief introduction to the concept of geodesics and of the stress-energy tensor (and of tensors in general), which would have allowed at least a qualitative treatment of Einstein's Field Equations.
  And, to be honest, I do not see much value in the first two chapters of the book, which are not much more than a very cursory introduction to mathematical objects that anybody should have learned in high school anyway (apart maybe from the concept of "symmetry")- maybe this space could have been used more efficiently by getting into some more detail in other areas.
  
  But I realize that there is a very delicate balance between mathematical complexity and accessibility and clarity, so it must be said that it would be extremely difficult to improve on Feynman's pedagogical approach in his book.
  
  In summary, this is a jewel of a little book that I thoroughly enjoyed and which deserves a full 5-star rating. Highly recommended. I loved it.
  
  
  
  
• 
  Kevin Lopez (on sabbatical)

  Feynman is, as ever, utterly ingenious in his ease of explication here, especially given that the concepts covered in this volume are more advanced than those covered in the previous one, “Six Easy Pieces” (as cheekily indicated by the title, “Six Not-So-Easy Pieces”)
  In this collection of transcribed lectures, once again taken from the fantastically popular series of undergraduate lectures he gave at Caltech in the early ‘60s (just a few years before he won the 1965 Nobel Prize for his work on quantum electrodynamics and path integrals), Feynman focuses almost exclusively on relativity, beginning with Galilean and Newtonian relativity before moving on to Einsteinian relativity—first the special and the then the general theory.
  He covers Special Relativity with brilliance and lucidity, enumerating the history of scientific thought underpinning Einstein’s revolutionary leap—from Galileo and Huygens, to Faraday, Maxwell, Lorentz, and Mach—and then moving on to the contemporaneous experimental results (such as the famous Michelson-Morley experiment) which by the end of the 20th century had revealed serious fissures in the foundations of physics. The most notable of these fissures (for the development of relativity, at least) was the incompatibility between Newtonian mechanics and Maxwell’s electromagnetic field equations, which—unlike Newton’s ideas, enshrined in his “Principia Mathematica,” which had taken on an aura of almost divine infallibility in the roughly two centuries since its publication—had only been completed about fifty years previous. As anyone who reads popular science books know, all of this is extremely well-tread ground in the ever-expanding world of mass-market physics writing—from the bestselling books of Stephen Hawking to the irresistibly fun and witty works of Neil deGrasse Tyson, to the brilliantly evocative, almost poetically imagistic writing of Carlo Rovelli. Where I found Feynman to be refreshingly different, though, is in his willingness to dig into the actual mathematics behind the science, demonstrating, for example, how the formula for Galilean transformations led directly to the far more accurate (both theoretically and experimentally) equation for the Lorentz transformation; or how the formula for Newton’s Second Law (F = d(mv)/dt) was brilliantly tweaked by Einstein, who corrected for Newton’s inaccurate assumption that mass is a constant when he came to the (stunning) conclusion that the mass of a body increases with velocity. Feynman gives us Einstein’s corrected formula, in which m has the value
  m = m[0] ➗ [the square root of] (1 - v^2/c^2),
  “where the ‘rest mass’ m[0] represents the mass of a body that is not moving.”
  In my experience, most contemporary popular science writers are utterly allergic to putting equations in their books—unless they’re buried in the footnotes way in the back (I remember one such writer saying something to the effect that for every equation he put in one of his books, its sales were cut in half). Because Feynman makes a point of using equations, not as off-putting esoterica to be avoided at all costs, but as an essential part of his teaching toolkit, he’s able to show much more clearly the evolution of Einstein’s thinking, presenting it for what is actually was: a meticulously thought-out scientific and mathematical conclusion—one which he drew from centuries of thought about the nature of relativistic motion, as well as the more recent discovery of the electromagnetic field equations and the finite velocity of light—not some sort of divine revelation, as is all-too-frequently implied (and which, I must admit, has an alluring quality to it, as it makes for an easier, neater story). Presenting the reader with the actual mathematics allows Feynman to dispel this myth and to show, step by step, the crucial thought processes that led to the incredible intellectual breakthrough that was Special Relativity. No matter how many clever analogies one is presented with—or, for that matter, illustrations of train cars and light clocks and so forth—one can’t fully grasp the many steps that lead to the real scientific theory until one can understand the equations which underpin it. Which isn’t to say that analogies aren’t useful, necessary tools—they are. Not only when trying to gain an understanding of a concept whose mathematics are utterly beyond one’s ken (the general theory, for example, requires a much higher level of mathematical understanding—or quantum mechanics, which, for most mere mortals, is an area of almost breathtaking abstruseness), but also, crucially, for the many modern scientific theories—including the Special Relativity—that go completely against the grain of our intuition. In terms of the basic formulae, though, with Special Relativity all one needs is an understanding of high school-level math to apprehend the steps that Einstein took to arrive at the conclusions he did. And by giving the actual equations—at least in the case of SR, where the underlying mathematics, if not the fairly mind-boggling conclusions drawn from it, are at least relatively (ha!) simple—Feynman is able to peel away the ornamentation of analogy to reveal the substructure beneath.
  I have to say that as I read this book, I found myself wishing that more of today’s science writers would take Feynman’s approach—forget whatever their publishers might be telling them about their book sales and respect the intellect of their readership. The publishers might just be in for a surprise.
  As brilliant as Feynman’s chapters on Special Relativity are—and they really are quite brilliant—the chapters on General Relativity are truly inspired. As the mathematics are far, far more advanced for the general theory (differential geometry, Riemann curvature, etc.) than for the special theory, and because these lectures were designed for an undergraduate audience, Feynman has to rely much more on analogies than equations here. Regardless of your level of mathematical proficiency, though, the concepts of General Relativity are not ones that human brains are evolved to understand intuitively. Just look at Einstein himself. After discovering the special theory in 1905, it took Einstein a full decade of wrestling with the extreme subtlety of the mathematics and all of its bizarre implications before he was finally able to complete the general theory (and this is Einstein we’re talking about, the guy whose name is a synonym for genius!). And to this day, many still view General Relativity as the single greatest achievement of human creativity and intellect. Needless to say the conclusions of the general theory, far more than those of SR, fly directly in the face of common-sense intuition and everyday experience. And here is where Feynman’s brilliance as a teacher really shines through. His analogies are concise, his explanations sparkling. He reminds me of no one so much as Carlo Rovelli, the Italian physicist whose books (“Seven Brief Lesson on Physics,” “Reality Is Not What it Seems,” “The Order of Time”) are more like Feynman’s than any other contemporary author I’ve come across, including such luminaries as Hawking, Roger Penrose (who, incidentally, wrote the introduction for “Six Not-So-Easy Pieces”), Leonard Susskind, Brian Greene, and Sean Carroll. (I would put Janna Levin in this class, too, though the only book of hers that I’ve read so far is “Black Hole Blues,” which is partly, if not mostly, also a narrative history of LIGO and the search for and ultimate discovery of gravitational waves.) Every science reader, of course, has their own favorite science writers. To me, what writers like Feynman and Rovelli (as well as Einstein himself, for that matter) seem to share that sets them apart is an intense artistic sensibility (for example, Rovelli begins each chapter in “The Order of Time” with a verse from Horace’s “Odes,” and Feynman, well—just read his memoir or one of the many biographies of the guy!), and stylistically a kind of poetic pithiness that makes reading their work such a unique experience. They’re simultaneously brilliantly lucid and poetically succinct; concise, compact, and perfectly cogent, while not avoiding or sacrificing any of the more difficult material or underestimating the intelligence of their readers.
  Feynman was not just a one-of-a-kind physicist, but also a one-of-a-kind person, and I highly recommend his memoir “Surely You’re Joking, Mr. Feynman,” which catalogues his many picaresque adventures, as well as his profound creativity in all areas of life.
  As quoted in the preface, Feynman wonders aloud whether, if he can’t explain a concept to an undergraduate student, he even understands the idea himself. Going by this standard for comprehension—and if his explanations here are any indication—he understood the concepts of modern physics better than almost anyone, before or since.
• 
  Roy Lotz

  All of our ideas in physics require a certain amount of common sense in their application; they are not purely mathematical or abstract ideas.

  
  It is difficult to review these books, as their titles are so descriptive. This book, as well as its companion, Six Easy Pieces, is a book that can judged by its cover. But this is a book reviewing site, after all, so review them I must.
  
  As you probably know, this book, like its predecessor, consists of excerpts from Feynman’s legendary Caltech lectures. The first book is aimed at the layperson; this book is aimed at the mathematically inclined layperson. Because the books originated in a serious physics course, but have been selected for accessibility, they fall into that vague territory that lies between popular science and science proper. Owing to their short length and numerous omissions, they are not meant to give the reader a rigorous introduction to the subject; nor are they, on the other hand, mere titillating anecdotes or strained analogies. The best way to think of them are as Feynman samplers; you will not be able to eat your fill, but the books leave a pleasant taste in your mouth.
  
  I don’t mean to suggest that you won’t learn anything from this book; far from it. Feynman is a wonderful teacher. He has no patience for formalisms or conventions; he is anything but pedantic. His mind leaps past all of the inessentials and arrives right to the core of topic; he doesn’t so much simplify, as clarify. Perhaps the best example of this is his explanation of simple machines in the first volume; he jumps past all the rules we learn in grade school, and explains it all in terms of conservation of energy. But even though he often relies on such abstract things as conservation or symmetry laws, he manages to be thoroughly concrete in his explanations. He gives you the general principle, and then walks you through an example. With Feynman, you can always literally ‘see’ the point.
  
  Feynman is also quite a showman. He has a keen sense for the dramatic, and will unveil a physical principle like a magician pulling a dove from a hat. But, unlike the magician, as soon as Feynman reveals the dove, he explains exactly how and why the dove was in the hat in the first place—and he’ll explain it in such a way that it will seem like the most obvious and commonsensical thing in the world that the dove was in the hat. This is beautifully illustrated in this little volume. In just shy of two hundred pages, none of which is particularly hard to read, Feynman will make relativity—one of the oddest theories we’ve ever come up with—seem as plain as the nose on your face. You will by no means be given a rigorous understanding of relativity from this book; but Feynman does, in his inimitable way, give you a “feel” for it. If you know a bit of calculus, and you know what a vector is, then I can’t think of a better place to start learning relativity.
  
  As a parting thought, I’d also like to add that it’s people like Feynman who make me occasionally proud my country. Sure, we produce a lot of duds; but occasionally someone like Feynman will come along that makes it seem all worthwhile. Some American qualities do, it seems, run deep. I can’t help but compare Richard Feynman with two other American greats: William James and Ernest Hemingway. Like those two, Feynman manages to be brilliant in three syllables or less. He is a populist in the best sense of the word, in that he thinks, not that we ought to dumb down our subject to reach as many people as possible, but that people will be interested and understanding if only we stopped putting on airs and spoke clearly. I look forward to spending some more time with him.
• 
  Rama Rao

  Learn Relativity from the maestro Richard Feynman himself
  
  In the introduction to this book, Roger Penrose, another great theoretical physicist of our times, states that "Relativity is not airy-fairy philosophy, nor is space-time mere mathematical formalism. It is a foundational ingredient of the very universe in which we live." On that note, it is encouraging for many readers that this book offers a great opportunity to take that extra step to learn the mathematical constructions for the effects of Lorentz transformations, Einstein's equations, relativistic dynamics; equivalence of mass and energy, Lorentz contraction and transformation of time. It requires undergraduate level physics, but comes with easy to follow instructions from the great maestro himself. Frequent references to his three volume book, Lectures in physics is valuable for readers who are familiar with his work.
  
  Position and time measured in one frame of reference (one observer) is different from another frame of reference (another observer). Therefore Lorentz transformation must be examined to understand physical reality. When we look at an object, we find that it has an apparent width and depth, but they are not fundamental properties of the object, because if we look at it from a different frame of reference it would look different. In Lorentz transformations we see is a mixture of space and time. An event (physical reality) is defined by both space and time because the position of an object is characterized by the time. The description of the object also depends upon the frame of reference (observer). If the observer is travelling at the speed of light, his perception of the object would be different from someone in a stationary state. The difference between spacetime, and space and the interval provides interesting sense of reality. For example, anything happening to Sun "now" will affect earth only after 8 minutes (that is how long light takes to reach us.) Thus an event "right now" can not be defined, it is a mystery, because we are not affected by it right now, but can be affected later after eight minutes. The "now" is an idea or a concept of our mind, it is not physically definable at the moment, and we have to wait to observe it separated by distance in (light) time. The example of page 64 establishes that simultaneity is not a unique thing in the universe, because it means different things to different observers.
  
  Relativistic dynamics; objects moving at high speeds (during forward motion) comparable to the speed of light shortens its physical length, and also time slows down (time-dilation) for the stationary observer, but the time remains the same for the moving astronaut. Thus for an observer moving under uniform velocity will not know he is in motion. The uniform velocity can not be detected without looking from outside, but the uniform rotation about a fixed axis can be detected without looking from outside. As noted earlier, the moving objects become heavier proportional to the speed given by the famous Einstein's equation, and at close to the speed of light the mass becomes enormous, and hence sufficient energy is not available to move anything beyond the speed o light.
  
  There are many websites that explains the transition from Newtonian mechanics to the theory of relativity to explain physical reality. Some of them are referenced below, but is great to read Richard Feynamn, because he did not like scientific ideas without a good physical foundation, and his approach is strikingly original. His efforts are strenuous in teaching and making the reader understand the basic concepts. I especially recommend chapters 3 and 4 for a quick appreciation of the subject: Highly recommended to all readers interested in physics of reality.
  
  
• 
  Utti

  C'è chi ha il dono di rendere facili anche le cose più difficili. Chi è capace di trasmettere poesia tramite le formule di trasformazione. Feynman è capace di tutto questo e anche di più. Un saggio da non perdere se si può contare su solide basi matematiche e fisiche.
• 
  Upom

  Pretty aptly titled book. In contrast to "
  Six Easy Pieces: Essentials of Physics Explained by Its Most Brilliant Teacher", there was a lot more mathematical formalism that was a little tough to follow, but with patience could be understood. The six lectures are put together so you can better understand Einsteins' special and general relativity. The book really made me appreciate the power of mathematics and interpretation to determine the nature of the real world. I actually found out how they determined E=mc^2! The book also had Feynman's characteristic humor and crazy imagination to illustrate really tough physics and mathematics. I really wish Feynman's entire lecture set wasn't so expensive :-(.
• 
  Elliot Evans

  Six not-so-easy introduces 6 topics, each one building on-top of the last, culminating in the final topic of the geometry of spacetime. Discussion includes just enough math as to pass on a real understanding without being overwhelming to someone without much of a background in physics, and to allow you to traverse from the relatively simple initial topic of vector algebra to the advanced final topic of spacetime.
  
  By the end of the book I had learned about the appearance of asymmetry of left and right in living things, how to figure out how much energy is released when an atom splits, and how your clock will run fast if you live higher up. Along with the fun and interesting examples, there is a deep underlying framework of understanding for modern physics.
• 
  Sato

  The principle of Conservation of Momentum, to me, is the most stunning nature of physics, and I guess the way Feynman understands and explains physical principles is the next stunning nature of physics!

  
  

  Having a high school knowledge of physics and mathematics can give you a delightful time through the pages of this book and give you the chance to cherish understanding Einstein’s relativity in six-not-so-easy pieces.
• 
  Rami

  I really loved this book.
  
  I have studied relativity in university, and afterwards, read several books on the subject, including Hawking books, but I have not really felt that I have started to grasp what general relativity's consequences are, until I read this book.
  
  The meticulously crafted analogies and examples gave a new meaning to symmetry in physical laws, the physical consequences of relativity, and the geometry of space-time when it comes to how I think of them.
  
  There were a few locations where I felt sudden jumps over ideas, but I guess that is natural, as this book is selected chapters from the complete Feynman Lectures, which I am hoping to go through in whole someday.
  
• 
  Utsob Roy

  আসলেই নট সো ইজি। একটু সময় লাগলো বেশি। ফাইনম্যান বরাবরের মতই ফাইন যদিও।
• 
  Blair

  This book is aimed at teaching Special Relativity to students who have high school algebra (thus can handle a co-ordinate transform) and Newtonian mechanics. The introduction promises us an innovative approach to understanding physics. The first innovation appears to be the concept of relativistic mass. OK, this was written in 1963, and maybe before that students were simply told to memorize the Lorentz transformation matrix. If you have just learned Newton’s Laws, you can use the same equations with mass increasing as velocity approaches the speed of light. Simple enough, but almost every physicist today says relativistic mass is misleading, and he himself admits that it “surprisingly enough, is rarely used.”
  
  For example, he tells us that the Caltech synchrotron requires a magnetic field 2,000 times stronger than would be expected on the basis of Newton’s laws to deflect the increased mass of a rapidly moving proton. Well, the strength of a magnetic field depends on its frame of reference, and the field the proton feels is much weaker. Really, the only value of this part of the book for me was the challenge of reformulating his explanations in more modern terms.
  
  However, the chapter on Curved Space was superb. I found it interesting that the curvature of a sphere is the same as for a disk with a temperature that gradually increases out from the centre, which causes anything on it to expand accordingly. Later, he considers the best path to move a projectile between two points in a fixed amount of time, using only relativity theory. The rate of time flow in a gravitational field increases, so we should send the projectile as high as possible. But to do that we need to move the projectile up quickly, which slows down its time. Calculating the optimum rate generates the Lagrangian for the difference between kinetic and potential energy, from which we can derive the laws of classical mechanics.
  
  Oops, now we are supposed to know what a Lagrangian is to understand the significance of what he has done, generating classical mechanics purely from optimizing proper time in relativity.
  
  I generally suggest avoiding this book and its outdated approach to Special Relativity. However, the last chapter made the time spent well worthwhile for me.
• 
  Dileep N

  This has a few marked differences in comparison with its sister volume, The Six Easy Pieces. It's at a higher level than a pop-sci intro and so it expects its readers to have seen some physics before and it has quite a few equations which means you will need some knowledge of vector algebra along with basic integral and differential calculus to fully appreciate the content.
  
  This book deals exclusively with Einstein's theory of relativity (both special and general) along with a brief detour into the topic of symmetry of physical laws. Although Feynman does a brilliant job of explaining this unintuitive and fairly involved topic with the aid of helpful albeit quirky examples and analogies, I only got a vague sense of Relativity and its consequences. I felt the book was too short to include all of the 'whys' and 'hows', which made things a tad confusing for me. This is after all bits and pieces of Feynman Lectures strung together to introduce a wide audience to Einstein's groundbreaking ideas, so don't expect to understand the topic well enough to be able to explain it to someone else.
  
  That being said, I do think reading this book will stand you in good stead when you move onto more technical and thorough (including the complete Feynman Lectures themselves) books on the topic. Recommended for Physics enthusiasts.
• 
  Kerem Cankocak

  Feynman olağanüstü etkili bir eğitimciydi. Sayısız ödülleri arasında, 1972'de kazandığı Örsted Öğretim Madalyası'yla özellikle gurur duyardı. Özgün olarak 1963'te basılmış olan Feynman'ın Fizik Dersleri'ni, Scientific American dergisinde bir eleştirmen şöyle betimliyordu: “Çetin, ama besleyici ve leziz. 25 yıl sonra öğretmenler için yol gösterici ve yeni başlayan öğrenciler içinse en iyisi.” Bu kitabın içeriğini oluşturan konular Feynman’ın fizik derslerinin popülerleştirilmiş özetleridir. Altı Kolay Parça’dan farklı olarak bir parça daha fazla matematik içeren Altı Zor Parça, kara deliklerden solucan deliklerine, atom enerjisinden zaman bükülmelerine kadar Einstein göreliliği, simetri ve uzayzaman konularını Feynman’ın usta anlatımıyla sunmaktadır.
  
  “Richard Feynman'ın neden böylesine büyük bir öğretmen olduğunu anlamak için, onun bir bilim insanı olarak olağanüstü niteliğini takdir etmek önemlidir.”
  Roger Penrose
  “Feynman büyük bir öğretmenden daha büyüktü. Onun yeteneği, onu öğretmenlerin olağanüstü öğretmeni yapıyordu”
  David L. Goodstein
  “Bu derslerde, Feynman'ın zekâsı ve dehası hakkında duyup durduğunuz her şey ortaya çıkıyor.”
  John Horgan Bilimin Sonu’nun yazarı
• 
  Navid Asmari Saadabad

  For sure, one can find quite more helpful resources to learn about special and general theory of relativity, but with this book, you can follow these topics without having to hold a pen and paper next to you. He narrates it as a story and keeps the subjects simple enough such that one would not let go of the book.
  This way, there will be a lot of open questions and proofs that are not touched in the book. I can say that the book is good enough to give you a glimpse of the main ideas in special and general theory of relativity, similar to a guidebook. It is on you to resolve the annoying gaps that are shaped in your mind afterwards; it is not Feynman's fault that you end up having a more chaotic mind on physics. The book brings chaos and order to the mind, simultaneously.
• 
  Eric Layton

  Whew! This one was not-so-easy. My Algebra, Trigonometry, and Vector Analysis skills are very rusty. However, that being said... the ONLY way to see the ultimate beauty of Einstein's theories is to "do the math."
  
  Feynman is awesome.
• 
  Haaris Mateen

  A beautiful book. This is a selection from Feynman's lectures specifically covering Einstein's Special and General Theories of Relativity. The treatment is involved; not at an unreachable technical level but one needs to take some paper with pencil to enjoy the content as Feynman explains some profound and extraordinary physics.
  
  In a time of excessive work, night reads like this give a glimpse of something far more eternal and magnificent than what can be seen in normal life. And I am grateful for it.
  
  (Last read this book in 2005)
• 
  Elizabeth Horton

  Not a hard read because it's broken up into small chunks, but hard to absorb--heavy on derivations which are sometimes interesting but require a lot of brainpower. Hopefully though continued exposure I absorb just a little at a time. Did have some fun re-revelations about relativity.
• 
  Stefano Lusoli

  "Non ridete delle notazioni, inventatene: esse sono potenti."
• 
  Alex Salo

  A solid continuation of the Six Easy Pieces. Very similar wry and exciting style, but with quite a bit more math and complexity. Still reads easily - you can even just skip the notations, though is Feynman points out lots of progress in physics comes from using better notations. Great book to expand your horizons and question the assumed notions.
• 
  Dennis Leth

  Another great read. A bit more difficult to understand than the 'Six easy pieces'. Which was hard enough for a layman. I truly enjoyed getting behind some of the reasonings for:
  - Vectors
  - Symmetri in physical law
  - The special theory of relativity
  - Relativistic energy and momentum
  - Space-Time
  - Curved space
  
  The lectures are part of a bigger collection of lectures called: 'The Feynman Lectures'. The Feynman lectures was a freshman and sophomore class for students at CalTech where they would get insight into the marbles of physics.
  
  I enjoyed taking a soft dive into the twelve chapters presented in the 2 short books: 'Six easy pieces' and 'Six not-so-easy pieces'. It gave me some insight and curiosity. But also an understanding of the need to look into and get updated on mathematics before going any deeper. I would think that a great understanding of mathematics would give much more insight than I got. It's been almost 30 years since I had advanced math and psychics in high school.
  
  Great book which I can highly recommend. And I would also use the opportunity to advertise for the 2 great semi biographies of Richard Feynman in form of transcripts of conversations he has had with Ralph Leighton: 'Surely, you're joking Mr. Feynman' and 'What do you care What other people think?'.
  
• 
  Martti

  "Suhteellisen helppoa - seitsemän lukua fysiikkaa" on suomennos luennoista, jotka laadittiin teoreettisen fysiikan professorin ja nobelistin Richard Feynmanin California Institute of Technologyssa vuosina 1961-1963 pitämästä maailmankuulusta fysiikan alkeiskurssista. Vaikka kurssista on tullut fysiikan klassikko, niin omasta mielestään Feynman ei onnistunut opetuksessaan erityisen hyvin. Kun hänelle huomautettiin, että sentään noin 20 oppilasta kurssin 180 oppilaasta oli ymmärtänyt melkein kaiken luennoilla käsitellyn, hän totesi kuuluisaa historioitsijaa Edward Gibbonia lainaten, että "opetuksen voima tehoaa harvoin lukuun ottamatta onnellisia poikkeuksia, joiden kohdalla se on miltei tarpeetonta".
  
  Feynman oli tunnetusti loistava ja pidetty opettaja, jonka läsnäolo sähköisti opetustilanteen. Kirjan esipuheessa professori Kari Enqvist mainitsee, että eräs hänen haastattelemansa Feynmanin oppilas oli todennut, että Feynmanin saapuessa tuntui kuin Kristus olisi tullut paikalle.
  
  Kirjasta ilmenee hyvin Feynmanin laaja-alaisuus ja valtava tietomäärä. Hänen yksinkertaistuksensa ja pelkistyksensä fysiikan ilmiöistä ja teorioista ovat yksinkertaisesti loistavia. Mieleen jäivät erityisesti kappaleiden liikettä ja avaruudellista kaarevuutta koskevien ilmiöiden havainnolliset tarkastelut. Fysiikan lainalaisuuksien matemaattinen esittely ja niiden kaavojen johtaminen oli kyllä selkeää, mutta siinä määrin vaativaa, että harvalla lukijalla on niiden omaksumiseen riittäviä taustatietoja.
  
  Merkittävä osuus kirjassa omistetaan Einsteinin suhteellisuusteorian ja sen merkityksen tarkastelulle. Vuodelta 1905 peräisin olevasta suppeasta suhteellisuusteoriasta Feynman toteaa, että siinä kumotaan yli 200 vuotta menestyksellisesti sovellettu Newtonin liikelaki, jossa mm. oletetaan liikkuvan kappaleen massan pysyvän vakiona. Feynmanin mukaan Einstein osoitti, että nopeuden kasvaessa massa ei pysykään vakiona vaan kasvaa. Feynmanin muotoilu liikkuvan kappaleen massan muuttumisesta on vähintäänkin kyseenalainen tai ainakin huonosti onnistunut.
  
  Lopuksi: kirjan lukijalle selviää Feynmanin käsitys siitä, mikä on koko ihmiskunnan tärkein yksittäinen lause. Se on itse asiassa hyvinkin lähellä samaa ajatusta, jonka jo kreikkalaiset filosofit olivat esittäneet maailmankaikkeudesta noin 2500 vuotta aiemmin.
• 
  Ben

  For all of those who took introductory college level physics courses once upon a time, and wish to know more about the development of the science during the 20th century, this is a very authentic introduction. A basic understanding of calculus is important, even if it was acquired some years ago and partially forgotten, to comprehend the various mathematical explanations that go along with any serious study of physics. If that doesn't scare you, or if you have the will and the patience to give it a try anyway, Feynmann's presentation is imaginative, entertaining, and for the most part accessible.
  Part of his original "Lectures on Physics," written and delivered for an audience of undergraduate college students, this shorter work covers some of the most important ideas and discoveries of modern physics including Einstein's special theory of relativity, space time, and gravitational equivalence. Persistent references to other parts of the original work sometimes leave information wanting, but generally the concepts covered are well explained in a creative but direct manner intended to shed light on difficult ideas without being convoluted or contradictory. Despite it's small size, not many would consider it light reading, however, if one is genuinely looking to learn something about the wonders and intricacies of our universe and how it operates, Feynmann remains an excellent teacher.
• 
  April

  Minus two stars for my own mathematical and equation lack of knowledge. So many equations and symbols! I don't remember the names for most of the Greek symbols/letters used. But I did enjoy reading about the different laws and what happens in curved space-time.
  
  "Another example in which the laws are not symmetrical, that we know quite well, is this: a system in rotation at a uniform angular velocity does not give the same apparent laws as one that is not rotating. If we make an experiment and then put everything in a spaceship and have the spaceship spinning in empty space all alone at a constant angular velocity, the apparatus will not work the same way because, as we know, things inside the equipment will be thrown to the outside, and so on, by the centrifugal or Coriolis forces, etc. In fact, we can tell that the earth is rotating by using a so-called Foucault pendulum, without looking inside." pg. 28 [The Coriolis effect/force was also mentioned in To Sleep in a Sea of Stars, which I'm currently also reading, so this was more of a book coincidence, but I wanted to gather the context around the Coriolis effect/force to better understand it. Also is this the same Foucault who talked about surveillance?]
  
  "The symmetries of the physical laws are very interesting at this level, but they turn out, in the end, to be even more interesting and exciting when we come to quantum mechanics. For a reason which we cannot make clear at the level of the present discussion--a fact that most physicists still find somewhat staggering, a most profound and beautiful thing, is that, in quantum mechanics, for each of the rules of symmetry there is a corresponding conservation law; there is a definite connection between the laws of the conservation and the symmetries of physical laws. We can only state this at present, without any attempt at explanation.
  The fact, for example, that the laws are symmetrical for translation in space when we add the principles of quantum mechanics turns out to mean that momentum is conserved.
  That the laws are symmetrical under translation in time means, in quantum mechanics, that energy is conserved.
  Invariance under rotation through a fixed angle in space corresponds to the conservation of angular momentum. These connections are very interesting and beautiful things, among the most beautiful and profound things in physics." pg. 29
  
  "The principle of relativity was first stated by Newton, in one of his corollaries to the laws of motion: 'The motions of bodies included in a given space are the same among themselves, whether that space is at rest or moves uniformly forward in a straight line.' This means, for example, that if a spaceship is drifting along at a uniform speed, all experiments performed in the spaceship and all the phenomena in the spaceship will appear the same as if the ship were not moving, provided, of course, that one does not look outside. That is the meaning of the principle of relativity. This is a simple enough idea, and the only question is whether it is true that in all experiments performed inside a moving system the laws of physics will appear the same as they would if the system were standing still." pg. 50-51
  
  "Given the fact that the velocity of light is 186,000 mi/sec, one will find few philosophers who will calmly state that it is self-evident that if light goes 186,000 mi/sec inside a car, and the car is going 100,000 mi/sec, that the light also goes 186,000 mi/sec past an observer on the ground. That is a shocking fact to them; the very ones who claim it is obvious find, when you give them a specific fact, that it is not obvious." pg. 75
  
  "The mass of the object which is formed when two equal objects collide must be twice the mass of the objects which come together. You might say, 'Yes, of course, that is the conservation of mass.' But not 'Yes, of course,' so easily, because these masses have been enhanced over the masses that they would be if they were standing still, yet they still contribute, to the total M, not the mass they have when standing still, but more. Astonishing as that may seem, in order for the conservation of momentum to work when two objects come together, the mass that they form must be greater than the rest masses of the objects, even though the objects are at rest after the collision!" pg. 88
  
  "Now the interesting thing about all the rest of space-time, i.e. region 1, is that we can neither affect it now from O, nor can it affect us now at O, because nothing can go faster than the speed of light. Of course, what happens at R can affect us later; that is, if the sun is exploding 'right now,' it takes eight minutes before we know about it, and it cannot possibly affect us before then.
  What we mean by 'right now' is a mysterious thing which we cannot define and we cannot affect, but it can affect us later, or we could have affected it if we had done something far enough in the past. When we look at the star Alpha Centauri, we see it as it was four years ago; we might wonder what it is like 'now.' 'Now' means at the same time from our special coordinate system. We can only see Alpha Centauri by the light that has come from our past, up to four years ago, but we do not know what it is doing 'now'; it will take four years before what it is doing 'now' can affect us. Alpha Centauri 'now' is an idea or concept of our mind; it is not something that is really definable physically at the moment, because we have to wait to observe it; we cannot even define it right 'now.' Furthermore, the 'now' depends on the coordinate system. If, for example, Alpha Centauri were moving, an observer there would not agree with us because he would put his axes at an angle, and his 'now' would be a different time. We have already talked about the fact that simultaneity is not a unique thing." pg. 100-101
  
  Book: borrowed from SSF Main Library.
• 
  Prooost Davis

  "Not so easy" is right! Feynman designed these lectures so that, he hoped, physics non-majors would be able to grasp the concepts, while majors would get a sense of the excitement of physics and maintain their interest.
  
  There is a lot of math in the book, but one can ignore most of it (as I did), and try to understand the ideas from Feynman's very clear and simple language. But, simple as Feynman's language is, these concepts are hard for even a smart person to get his or her head around. We have grown up in a 3-dimensional world that we understand somewhat, and it's not easy to grasp relativity, curved space, of space-time, let alone curved space-time. I did my best, and Feynman is always a joy to read, but I probably won't remember much about these topics tomorrow.
• 
  Utsav

  Essential reading for relativity enthusiasts (of the weekend variety, I might add- the more academic ones might be better served by lectures given by the wild-haired maestro himself). Requires, and assumes, knowledge of Std XII Maths and Physics- you'll be pretty lost if you don't know what the hell differentials and integrals are. Though written in Feynman's casual, conversational style, the book never fails to make your head spin, and it's fun to put the book down on your chest in the middle of a chapter and think about how your reality ain't so real after all, dude...
  I swear, science is drugs!
• 
  CV Rick

  Richard Feynman was a brilliant, creative teacher. In this volume he tackles some of the trickier subjects in physics. He starts slowly, even simplistically with a discussion of symmetry and builds one upon the other taking the reader through some relativistic topics and finally concluding with a fantastic description of space-time geometry. In a few short lessons, he showed me what had taken months at university to understand. I wish there were more teachers like him today.