Great scientists come in two varieties, which Isaiah Berlin, quoting the seventh-century-BC poet Archilochus, called foxes and hedgehogs. Foxes know many tricks, hedgehogs only one. Foxes are interested in everything, and move easily from one problem to another. Hedgehogs are interested only in a few problems which they consider fundamental, and stick with the same problems for years or decades. Most of the great discoveries are made by hedgehogs, most of the little discoveries by foxes. Science needs both hedgehogs and foxes for its healthy growth, hedgehogs to dig deep into the nature of things, foxes to explore the complicated details of our marvelous universe. Albert Einstein was a hedgehog; Richard Feynman was a fox.
Many readers of The New York Review of Books are more likely to have encountered Feynman as a story-teller, for example in his book Surely You’re Joking, Mr. Feynman!,1 than as a scientist. Not many are likely to have read his great textbook The Feynman Lectures on Physics,2 which was a best seller among physicists but was not intended for the general public. Now we have a collection of his letters, selected and edited by his daughter, Michelle. The letters do not tell us much about his science. For readers who are not scientists, it is important to understand that foxes may be as creative as hedgehogs. Feynman happened to be young at a time when there were great opportunities for foxes. The hedgehogs, Einstein and his followers at the beginning of the twentieth century, had dug deep and found new foundations for physics. When Feynman came onto the scene in the middle of the century, the foundations were firm and the universe was wide open for foxes to explore.
One of the few letters in the collection that discusses Feynman’s science was written to his former student Koichi Mano. It describes the fox’s way of working:
I have worked on innumerable problems that you would call humble, but which I enjoyed and felt very good about because I sometimes could partially succeed…. The development of shock waves in explosions. The design of a neutron counter…. General theory of how to fold paper to make a certain kind of child’s toy (called flexagons). The energy levels in the light nuclei. The theory of turbulence (I have spent several years on it without success). Plus all the “grander” problems of quantum theory.
No problem is too small or too trivial if we can really do something about it.
“The ‘grander’ problems of quantum theory” were only one item in a long list of Feynman’s activities.
The phrase “the ‘grander’ problems of quantum theory” refers to the great work for which he received a Nobel Prize in 1965: inventing the pictorial view of nature which he called “the space-time approach.” This work began in 1947 as a modest enterprise, to calculate accurately the fine details of the hydrogen atom for comparison with the findings of some new experiments that had been done at Columbia University. To do the calculation, Feynman invented a new way of describing quantum processes, using pictorial diagrams instead of equations to represent interacting particles. The “Feynman Diagrams” that he invented for a particular calculation caused a revolution in physics. The diagrams were not only a useful tool for calculation but a new way of understanding nature. Feynman’s basic idea was simple and general. If we want to calculate a quantum process, all we need to do is to draw stylized pictures of all the interactions that can happen, calculate a number corresponding to each picture by following some simple rules, and then add the numbers together. So a quantum process is just a bundle of pictures, each of them describing a possible way in which the process can happen.
Feynman’s diagrams gave us a simple visual representation of quantum processes not only for hydrogen atoms but for everything else in the universe. Within twenty years after they were invented, these diagrams became the working language of particle physicists all over the world. It is difficult now to imagine how we used to think about fields and particles before we had this language. A new book by the MIT historian David Kaiser, Drawing Theories Apart: The Dispersion of Feynman Diagrams in Postwar Physics,3 gives a lively account of the spread of the diagrams, describing how they were transmitted around the world. The diagrams spread like a flu epidemic. Each new generation of young scientists became infected with the Feynman disease and then infected others with whom they came into personal contact. The Feynman epidemic lasted longer than a flu epidemic, because the incubation period was measured in years rather than in days. Many of the older scientists remained immune, but their influence waned as the new language became universal.
After Feynman’s work on the diagrams was done, a year went by before it was published. He was willing and eager to share his ideas in conversation with anyone who would listen, but he found the job of writing a formal paper distasteful and postponed it as long as he could. His seminal paper, “Space-Time Approach to Quantum Electrodynamics,”4 might never have been written if he had not gone to Pittsburgh to stay for a few days with his friends Bert and Mulaika Corben. While he was in the Corbens’ house, they urged him to sit down and write the paper, and he made all kinds of excuses to avoid doing it. Mulaika, who was a liberated woman with a forceful personality, decided that drastic measures were needed. She was one of the few people who could stand up to Feynman in a contest of wills. She locked him in his room and refused to let him out until the paper was finished. That is the story that Mulaika told me afterward. Like other Feynman stories, it may have been embellished in the telling, but to anyone who knew both Mulaika and Feynman it has the ring of truth.
People who knew Feynman as a friend and colleague were astonished when this collection of his letters appeared. We never thought of him as a letter writer. He was famous as a great scientist and a great communicator, but his way of communicating with the public was by talking rather than writing. He talked in a racy and informal style, and claimed to be incapable of writing grammatical English. His many books were not written by him but transcribed and edited by others from recordings of his talks. The technical books were records of his classroom lectures, and the popular books were records of his stories. He preferred to publish his scientific discoveries in lectures rather than in papers.
This book now reveals that Feynman was, like that other great communicator Ronald Reagan, secretly writing personal letters to a great variety of people. Few of the letters are to his professional colleagues. Many of them are to his family, and many are to people he did not know and never met, answering letters that they wrote to him with questions about science. In spite of his pretense of being illiterate, the letters are written in lucid and grammatical English. They rarely mention his work as a creative scientist. They say nothing about his current research. In these letters we see Feynman as a teacher. He spent much of his life teaching, and he threw himself into teaching as passionately as he threw himself into research. He wrote these letters because he wanted to help anyone who sincerely tried to understand. The letters that he preferred to answer were those which posed problems that he could explain in simple language. The problems were usually elementary, and Feynman’s answers were pitched at a level that his correspondent could understand. He was not trying to be clever. His purpose was to be clear.
Every one of the letters is personal. He responded to people’s personal needs as well as to their questions. As an example of his personal response, here is the last paragraph of the letter to Koichi Mano which I have already quoted. Koichi was unhappy with his life as a scientist because he was not working on fundamental problems. Feynman replies:
You say you are a nameless man. You are not to your wife and to your child. You will not long remain so to your immediate colleagues if you can answer their simple questions when they come into your office. You are not nameless to me. Do not remain nameless to yourself—it is too sad a way to be. Know your place in the world and evaluate yourself fairly, not in terms of the naïve ideals of your own youth, nor in terms of what you erroneously imagine your teacher’s ideals are.
Best of luck and happiness.
Richard P. Feynman
Michelle Feynman added some brief comments to the letters and an introduction describing what it was like to be Feynman’s daughter. She was as surprised as everyone else when she discovered the letters and started to read them sixteen years after his death. For sixteen years they had remained hidden in filing cabinets in the archives of the California Institute of Technology, interspersed with masses of technical papers and lecture notes. As soon as she had read them, she decided that they should be shared with the world. They show a new side of Feynman. The public had seen him before as a great scientist and as a famous clown. A week after I first met him at Cornell University in 1947, I described him in a letter to my parents as “half genius and half buffoon.” Here in the letters he is neither genius nor buffoon, but a wise counselor, interested in all kinds of people, answering their questions, and trying to help them as best he can.
Michelle’s introduction ends with a note that she found with the letters in the archive. Feynman wrote it for his acceptance speech at the Nobel Prize banquet in Stockholm. Before he went to Sweden, when the award of his Nobel Prize was first announced, he made disparaging remarks about the prize and about the formal ceremonies that he would have to endure in Stockholm. He said that he had made up his mind to refuse the prize, until his wife told him that refusing it would bring him even more unwelcome publicity than accepting it. He detested formal ceremonies, and he especially detested the snobbery associated with kings and queens and royal palaces. But then, after he went to Stockholm and experienced the warmth of a Swedish welcome, he wrote a note that is as close as he ever came to expressing his emotions in public. He describes how the prize had led to a deluge of messages:
Reports of fathers turning excitedly with newspapers in hand to wives; of daughters running up and down the apartment house ringing neighbors’ door bells with news; victorious cries of “I told you so” by those having no technical knowledge—their successful prediction being based on faith alone; from friends, from relatives, from students, from former teachers, from scientific colleagues, from total strangers….
In each I saw the same two common elements. I saw in each, joy; and I saw affection (you see, whatever modesty I may have had has been completely swept away in recent days).
The Prize was a signal to permit them to express, and me to learn about, their feelings….
For this, I thank Alfred Nobel and the many who worked so hard to carry out his wishes in this particular way.
And so, you Swedish people, with your honors, and your trumpets, and your king—forgive me. For I understand at last—such things provide entrance to the heart. Used by a wise and peaceful people they can generate good feeling, even love, among men, even in lands far beyond your own. For that lesson, I thank you.
Addison-Wesley, 1963–1965 (three volumes).↩
University of Chicago Press, 2005.↩
Physical Review, Vol. 76, No. 6 (September 15, 1949).↩