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Preface to the New Millennium Edition

Kip Thorne

Nearly fifty years have passed since Richard Feynman taught the introductory physics course at Caltech that gave rise to these three volumes, The Feynman Lectures on Physics. In those fifty years our understanding of the physical world has changed greatly, but The Feynman Lectures on Physics has endured. Feynman’s lectures are as powerful today as when first published, thanks to Feynman’s unique physics insights and pedagogy. They have been studied worldwide by novices and mature physicists alike; they have been translated into at least a dozen languages with more than 1.5 millions copies printed in the English language alone. Perhaps no other set of physics books has had such wide impact, for so long.

This New Millennium Edition ushers in a new era for The Feynman Lectures on Physics (FLP): the twenty-first century era of electronic publishing. FLP has been converted to eFLP, with the text and equations expressed in the LaTeX electronic typesetting language, and all figures redone using modern drawing software.

The consequences for the print version of this edition are not startling; it looks almost the same as the original red books that physics students have known and loved for decades. The main differences are an expanded and improved index, the correction of 885 errata found by readers over the five years since the first printing of the previous edition, and the ease of correcting errata that future readers may find. To this I shall return below.

The eBook Version of this edition, and the Enhanced Electronic Version are electronic innovations. By contrast with most eBook versions of 20th century technical books, whose equations, figures and sometimes even text become pixellated when one tries to enlarge them, the LaTeX manuscript of the New Millennium Edition makes it possible to create eBooks of the highest quality, in which all features on the page (except photographs) can be enlarged without bound and retain their precise shapes and sharpness. And the Enhanced Electronic Version, with its audio and blackboard photos from Feynman’s original lectures, and its links to other resources, is an innovation that would have given Feynman great pleasure.

Memories of Feynman’s Lectures

These three volumes are a self-contained pedagogical treatise. They are also a historical record of Feynman’s 1961–64 undergraduate physics lectures, a course required of all Caltech freshmen and sophomores regardless of their majors.

Readers may wonder, as I have, how Feynman’s lectures impacted the students who attended them. Feynman, in his Preface to these volumes, offered a somewhat negative view.  “I don’t think I did very well by the students,” he wrote. Matthew Sands, in his memoir in Feynman’s Tips on Physics expressed a far more positive view. Out of curiosity, in spring 2005 I emailed or talked to a quasi-random set of 17 students (out of about 150) from Feynman’s 1961–63 class—some who had great difficulty with the class, and some who mastered it with ease; majors in biology, chemistry, engineering, geology, mathematics and astronomy, as well as in physics.

The intervening years might have glazed their memories with a euphoric tint, but about 80 percent recall Feynman’s lectures as highlights of their college years. “It was like going to church.” The lectures were “a transformational experience,” “the experience of a lifetime, probably the most important thing I got from Caltech.” “I was a biology major but Feynman’s lectures stand out as a high point in my undergraduate experience … though I must admit I couldn’t do the homework at the time and I hardly turned any of it in.” “I was among the least promising of students in this course, and I never missed a lecture. … I remember and can still feel Feynman’s joy of discovery. … His lectures had an … emotional impact that was probably lost in the printed Lectures.”

By contrast, several of the students have negative memories due largely to two issues: (i) “You couldn’t learn to work the homework problems by attending the lectures. Feynman was too slick—he knew tricks and what approximations could be made, and had intuition based on experience and genius that a beginning student does not possess.” Feynman and colleagues, aware of this flaw in the course, addressed it in part with materials that have been incorporated into Feynman’s Tips on Physics: three problem-solving lectures by Feynman, and a set of exercises and answers assembled by Robert B. Leighton and Rochus Vogt. (ii) “The insecurity of not knowing what was likely to be discussed in the next lecture, the lack of a text book or reference with any connection to the lecture material, and consequent inability for us to read ahead, were very frustrating. …  I found the lectures exciting and understandable in the hall, but they were Sanskrit outside [when I tried to reconstruct the details].” This problem, of course, was solved by these three volumes, the printed version of The Feynman Lectures on Physics. They became the textbook from which Caltech students studied for many years thereafter, and they live on today as one of Feynman’s greatest legacies.

A History of Errata

The Feynman Lectures on Physics was produced very quickly by Feynman and his co-authors, Robert B. Leighton and Matthew Sands, working from and expanding on tape recordings and blackboard photos of Feynman’s course lectures1 (both of which are incorporated into the Enhanced Electronic Version of this New Millennium Edition). Given the high speed at which Feynman, Leighton and Sands worked, it was inevitable that many errors crept into the first edition. Feynman accumulated long lists of claimed errata over the subsequent years—errata found by students and faculty at Caltech and by readers around the world. In the 1960s and early ’70s, Feynman made time in his intense life to check most but not all of the claimed errata for Volumes I and II, and insert corrections into subsequent printings. But Feynman’s sense of duty never rose high enough above the excitement of discovering new things to make him deal with the errata in Volume III.2 After his untimely death in 1988, lists of errata for all three volumes were deposited in the Caltech Archives, and there they lay forgotten.

In 2002 Ralph Leighton (son of the late Robert Leighton and compatriot of Feynman) informed me of the old errata and a new long list compiled by Ralph’s friend Michael Gottlieb. Leighton proposed that Caltech produce a new edition of The Feynman Lectures with all errata corrected, and publish it alongside a new volume of auxiliary material, Feynman’s Tips on Physics, which he and Gottlieb were preparing.

Feynman was my hero and a close personal friend. When I saw the lists of errata and the content of the proposed new volume, I quickly agreed to oversee this project on behalf of Caltech (Feynman’s long-time academic home, to which he, Leighton and Sands had entrusted all rights and responsibilities for The Feynman Lectures). After a year and a half of meticulous work by Gottlieb, and careful scrutiny by Dr. Michael Hartl (an outstanding Caltech postdoc who vetted all errata plus the new volume), the 2005 Definitive Edition of The Feynman Lectures on Physics was born, with about 200 errata corrected and accompanied by Feynman’s Tips on Physics by Feynman, Gottlieb and Leighton.

I thought that edition was going to be “Definitive”. What I did not anticipate was the enthusiastic response of readers around the world to an appeal from Gottlieb to identify further errata, and submit them via a website that Gottlieb created and continues to maintain, The Feynman Lectures Website, feynmanlectures.caltech.edu.  In the five years since then, 965 new errata have been submitted and survived the meticulous scrutiny of Gottlieb, Hartl, and Nate Bode (an outstanding Caltech physics graduate student, who succeeded Hartl as Caltech’s vetter of errata). Of these, 965 vetted errata, 80 were corrected in the fourth printing of the Definitive Edition (August 2006) and the remaining 885 are corrected in the first printing of this New Millennium Edition (322 in volume I, 363 in volume II, and 200 in volume III). For details of the errata, see feynmanlectures.caltech.edu/info.

Clearly, making The Feynman Lectures on Physics error-free has become a world-wide community enterprise. On behalf of Caltech I thank the 50 readers who have contributed since 2005 and the many more who may contribute over the coming years. The names of all contributors are posted at feynmanlectures.caltech.edu/info/flp_errata.html.

Almost all the errata have been of three types: (i) typographical errors in prose; (ii) typographical and mathematical errors in equations, tables and figures—sign errors, incorrect numbers (e.g., a 5 that should be a 4), and missing subscripts, summation signs, parentheses and terms in equations; (iii) incorrect cross references to chapters, tables and figures. These kinds of errors, though not terribly serious to a mature physicist, can be frustrating and confusing to Feynman’s primary audience: students.

It is remarkable that among the 1165 errata corrected under my auspices, only several do I regard as true errors in physics. An example is Volume II, page 5-9, which now says “…no static distribution of charges inside a closed grounded conductor can produce any [electric] fields outside” (the word grounded was omitted in previous editions). This error was pointed out to Feynman by a number of readers, including Beulah Elizabeth Cox, a student at The College of William and Mary, who had relied on Feynman’s erroneous passage in an exam. To Ms. Cox, Feynman wrote in 1975,3  “Your instructor was right not to give you any points, for your answer was wrong, as he demonstrated using Gauss’s law. You should, in science, believe logic and arguments, carefully drawn, and not authorities. You also read the book correctly and understood it. I made a mistake, so the book is wrong. I probably was thinking of a grounded conducting sphere, or else of the fact that moving the charges around in different places inside does not affect things on the outside. I am not sure how I did it, but I goofed. And you goofed, too, for believing me.”

How this New Millennium Edition Came to Be

Between November 2005 and July 2006, 340 errata were submitted to The Feynman Lectures Website feynmanlectures.caltech.edu. Remarkably, the bulk of these came from one person: Dr. Rudolf Pfeiffer, then a physics postdoctoral fellow at the University of Vienna, Austria. The publisher, Addison Wesley, fixed 80 errata, but balked at fixing more because of cost: the books were being printed by a photo-offset process, working from photographic images of the pages from the 1960s. Correcting an error involved re-typesetting the entire page, and to ensure no new errors crept in, the page was re-typeset twice by two different people, then compared and proofread by several other people—a very costly process indeed, when hundreds of errata are involved.

Gottlieb, Pfeiffer and Ralph Leighton were very unhappy about this, so they formulated a plan aimed at facilitating the repair of all errata, and also aimed at producing eBook and enhanced electronic versions of The Feynman Lectures on Physics. They proposed their plan to me, as Caltech’s representative, in 2007. I was enthusiastic but cautious. After seeing further details, including a one-chapter demonstration of the Enhanced Electronic Version, I recommended that Caltech cooperate with Gottlieb, Pfeiffer and Leighton in the execution of their plan. The plan was approved by three successive chairs of Caltech’s Division of Physics, Mathematics and Astronomy—Tom Tombrello, Andrew Lange, and Tom Soifer—and the complex legal and contractual details were worked out by Caltech’s Intellectual Property Counsel, Adam Cochran. With the publication of this New Millennium Edition, the plan has been executed successfully, despite its complexity. Specifically:

Pfeiffer and Gottlieb have converted into LaTeX all three volumes of FLP (and also more than 1000 exercises from the Feynman course for incorporation into Feynman’s Tips on Physics). The FLP figures were redrawn in modern electronic form in India, under guidance of the FLP German translator, Henning Heinze, for use in the German edition. Gottlieb and Pfeiffer traded non-exclusive use of their LaTeX equations in the German edition (published by Oldenbourg) for non-exclusive use of Heinze’s figures in this New Millennium English edition. Pfeiffer and Gottlieb have meticulously checked all the LaTeX text and equations and all the redrawn figures, and made corrections as needed. Nate Bode and I, on behalf of Caltech, have done spot checks of text, equations, and figures; and remarkably, we have found no errors. Pfeiffer and Gottlieb are unbelievably meticulous and accurate. Gottlieb and Pfeiffer arranged for John Sullivan at the Huntington Library to digitize the photos of Feynman’s 1962–64 blackboards, and for George Blood Audio to digitize the lecture tapes—with financial support and encouragement from Caltech Professor Carver Mead, logistical support from Caltech Archivist Shelley Erwin, and legal support from Cochran.

The legal issues were serious: In the 1960s, Caltech licensed to Addison Wesley rights to publish the print edition, and in the 1990s, rights to distribute the audio of Feynman’s lectures and a variant of an electronic edition. In the 2000s, through a sequence of acquisitions of those licenses, the print rights were transferred to the Pearson publishing group, while rights to the audio and the electronic version were transferred to the Perseus publishing group. Cochran, with the aid of Ike Williams, an attorney who specializes in publishing, succeeded in uniting all of these rights with Perseus (Basic Books), making possible this New Millennium Edition.


On behalf of Caltech, I thank the many people who have made this New Millennium Edition possible. Specifically, I thank the key people mentioned above: Ralph Leighton, Michael Gottlieb, Tom Tombrello, Michael Hartl, Rudolf Pfeiffer, Henning Heinze, Adam Cochran, Carver Mead, Nate Bode, Shelley Erwin,  Andrew Lange, Tom Soifer, Ike Williams, and the 50 people who submitted errata (listed at feynmanlectures.caltech.edu/info). And I also thank Michelle Feynman (daughter of Richard Feynman) for her continuing support and advice, Alan Rice for behind-the-scenes assistance and advice at Caltech, Stephan Puchegger and Calvin Jackson for assistance and advice to Pfeiffer about conversion of FLP to LaTeX, Michael Figl, Manfred Smolik, and Andreas Stangl for discussions about corrections of errata; and the Staff of Perseus/Basic Books, and (for previous editions) the staff of Addison Wesley.

Note added 13 May, 2022: In addition to Caltech professors who contributed to the making of FLP, a number of graduate students and staff helped with the technical details of its preparation. The Forewords written by Feynman's coauthors Leighton and Sands acknowledge these helpers, but while Volumes II and III give lists, Volume I includes only a general acknowledgment. After consulting knowledgeable colleagues I have constructed the following, likely incomplete, list of people who, I believe, deserve credit for their help with the technical details of preparing Volume I: Alan Title, Marylou Clayton, Julie Curcio, Don Groom, James Hartle, Tom Harvey, Fanny Warren, Clyde Zaidins, and Barbara Zimmerman. (I would welcome suggestions for additions or corrections to this list; please send them to me at Caltech.)

Kip S. Thorne
The Feynman Professor of Theoretical Physics, Emeritus
California Institute of TechnologyOctober 2010
(Photograph by Jon Rou)
  1. For descriptions of the genesis of Feynman’s lectures and of these volumes, see Feynman’s Preface and the Forewords to each of the three volumes, and also Matt Sands’ Memoir in Feynman’s Tips on Physics, and the Special Preface to the Commemorative Edition of FLP, written in 1989 by David Goodstein and Gerry Neugebauer, which also appears in the 2005 Definitive Edition.
  2. In 1975, he started checking errata for Volume III but got distracted by other things and never finished the task, so no corrections were made.
  3. Pages 288–289 of Perfectly Reasonable Deviations from the Beaten Track, The Letters of Richard P. Feynman, ed. Michelle Feynman (Basic Books, New York, 2005).