I first heard of Richard Feynman and Ralph Leighton in 1986, through their entertaining book Surely You’re Joking, Mr. Feynman! Thirteen years later I met Ralph at a party. We became friends, and over the next year we worked together on the design of a fantasy stamp honoring Feynman.¹ All the while Ralph was giving me books to read, by or about Feynman, including (since I am a computer programmer) Feynman Lectures on Computation.² The discussion of quantum mechanical computation in this fascinating book intrigued me, but without having studied quantum mechanics, I had difficulty following the arguments. Ralph recommended I read The Feynman Lectures on Physics Volume III: Quantum Mechanics, which I began, but Chapters 1 and 2 of Volume III are reproduced from Chapters 37 and 38 of Volume I, so I found myself backtracking through references in Volume I rather than progressing through Volume III. I therefore decided to read all The Feynman Lectures from beginning to end—I was determined to learn some quantum mechanics! However, that goal became secondary as time went on and I became increasingly absorbed in Feynman’s fascinating world. The joy of learning physics, simply for the pleasure of it, became my highest priority. I was hooked! About halfway through Volume I, I took a break from programming and spent six months in rural Costa Rica studying The Lectures full-time.

Every afternoon I studied a new lecture and worked on physics problems; in the mornings I reviewed and proofread yesterday’s lecture. I was in e-mail contact with Ralph, and he encouraged me to keep track of errors I mentioned encountering in Volume I. It was not much of a burden, because there were very few errors in that volume. However, as I progressed through Volumes II and III, I was dismayed to discover increasingly more errors. In the end I had compiled a total of more than 170 errors in The Lectures. Ralph and I were surprised: how could so many errors have been overlooked for so long? We decided to see what could be done about getting them corrected in the next edition.

Then I noticed some intriguing sentences in Feynman’s preface:

“The reason there are no lectures on how to solve problems is because there were recitation sections. Although I did put in three lectures in the first year on how to solve problems, they are not included here. Also there was a lecture on inertial guidance which certainly belongs after the lecture on rotating systems, but which was, unfortunately, omitted.”

This suggested the idea of reconstructing the missing lectures and, if they proved interesting, offering them to Caltech and Addison-Wesley for inclusion in a more complete and error-corrected edition of The Lectures. But first I had to find the missing lectures, and I was still in Costa Rica! Through a bit of deductive logic and investigation, Ralph was able to locate the lecture notes, which were previously hidden away somewhere between his father’s office and the Caltech Archives. Ralph also obtained tape recordings of the missing lectures, and while researching errata in the Archives after my return to California, I fortuitously discovered the blackboard photos (long believed lost) in a box of miscellaneous negatives. The Feynman heirs generously gave us permission to use these materials, and so, with some useful critiques from Matt Sands, now the only surviving member of the Feynman-Leighton-Sands trio, Ralph and I reconstructed Review B as a sample, and presented it with the errata for The Lectures to Caltech and Addison-Wesley.

Addison-Wesley received our ideas enthusiastically, but Caltech was initially skeptical. Ralph therefore appealed to Kip Thorne, the Richard Feynman Professor of Theoretical Physics at Caltech, who eventually managed to achieve a mutual understanding among all involved, and who generously volunteered his time to oversee our work. Since Caltech did not want to amend the existing volumes of The Lectures for historical reasons, Ralph proposed putting the missing lectures in a separate book. That is the origin of this supplementary volume. It is being published in parallel with a new Definitive Edition of The Feynman Lectures on Physics, in which the errors I found are corrected, as are other errors found by a number of other readers.

In our quest to reconstruct the four lectures, Ralph and I had many questions. We felt very fortunate to be able to get answers from Professor Matt Sands, the man whose idea it was to embark on the ambitious project that produced The Feynman Lectures on Physics. We were surprised that the story of their genesis was not widely known, and realizing that this project offered an opportunity to remedy that deficit, Professor Sands kindly agreed to write a memoir on the origins of The Feynman Lectures for inclusion in this supplement.

From Matt Sands we learned that in December 1961, toward the end of the first term³ of Feynman’s Caltech freshman physics course, it was decided that it would be unfair to introduce new material to the students just a few days before the final exam. So, for the week preceding the test, Feynman gave three optional review lectures, in which no new material was introduced. The review lectures were intended for students having difficulties in the class, and emphasized techniques for understanding and solving physics problems. Some of the example problems were of historical interest, including the discovery of the atomic nucleus by Rutherford, and the determination of the mass of the pi meson. With characteristic human insight, Feynman also discussed the solution to another kind of problem, equally important to at least half the students in his freshman class: the emotional problem of finding oneself below average.

The fourth lecture, Dynamical Effects and Their Applications, was given early in the second term of the freshman class, shortly after the students returned from winter break. Originally, it was to be Lecture 21, and the idea behind it was to take a rest from the difficult theoretical discussion of rotations presented in Chapters 18 through 20 and show the students some interesting applications and phenomena that arise from rotations, “just for entertainment.” Most of the lecture was devoted to a discussion of technology that was relatively new in 1962: practical inertial guidance. The remainder of the lecture discussed natural phenomena that arise from rotations, and also offered a clue as to why Feynman described the omission of this lecture from The Feynman Lectures on Physics as “unfortunate.”

After ending a lecture Feynman often left his microphone on. This has provided us with the unique opportunity of witnessing how Feynman interacted with his undergraduate students. The example given here, recorded after Dynamical Effects and Their Applications, is particularly noteworthy for its discussion of the incipient transition in real-time computing from analog to digital methods in 1962.

In the course of this project Ralph reestablished contact with his father’s good friend and colleague Rochus Vogt, who graciously gave his permission to republish exercises and solutions from Exercises in Introductory Physics, the collection that Robert Leighton and he had created especially for The Lectures back in the 1960s. Due to space limitations I chose only exercises for Volume I, Chapters 1 through 20 (the material covered before Dynamical Effects and Their Applications), preferring problems that, to quote Robert Leighton, “are numerically or analytically simple, yet incisive and illuminating in content.”

Readers are invited to visit feynmanlectures.caltech.edu for more information on this volume and The Feynman Lectures on Physics.