Dreams of Earth and Sky

by Freeman Dyson

  To Feynman’s dismay, Tomonaga failed to appear in Stockholm. The Ottaviani-Myrick book has Tomonaga explaining what happened:

  Although I sent a letter saying that I would be “pleased to attend,” I loathed the thought of going, thinking that the cold would be severe, as the ceremony was to be held in December, and that the inevitable formalities would be tiresome. After I was named a Nobel Prize awardee, many people came to visit, bringing liquor. I had barrels of it. One day, my father’s younger brother, who loved whiskey, happened to stop by and we both began drinking gleefully. We drank a little too much, and then, seizing the opportunity that my wife had gone out shopping, I entered the bathroom to take a bath. There I slipped and fell down, breaking six of my ribs.… It was a piece of good luck in that unhappy incident.

  After Tomonaga recovered from his injuries, he was invited to England to receive another high honor requiring a formal meeting with royalty. This time he did not slip in the bathtub. He duly appeared at Buckingham Palace to shake hands with the English queen. The queen did not know that he had failed to travel to Stockholm. She innocently asked him whether he had enjoyed his meeting with the king of Sweden. Tomonaga was totally flummoxed. He could not bring himself to confess to the queen that he had gotten drunk and broken his ribs. He said that he had enjoyed his conversation with the king very much. He remarked afterward that for the rest of his life he would be carrying a double burden of guilt: first for getting drunk, and second for telling a lie to the queen of England.

  Twenty years later, when Feynman was mortally ill with cancer, he served on the NASA commission investigating the Challenger disaster of 1986. He undertook this job reluctantly, knowing that it would use up most of the time and strength that he had left. He undertook it because he felt an obligation to find the root causes of the disaster and to speak plainly to the public about his findings. He went to Washington and found what he had expected at the heart of the tragedy: a bureaucratic hierarchy with two groups of people, the engineers and the managers, who lived in separate worlds and did not communicate with each other. The engineers lived in the world of technical facts; the managers lived in the world of political dogmas.

  He asked members of both groups to tell him their estimates of the risk of disastrous failure in each Space Shuttle mission. The engineers estimated the risk to be of the order of one disaster in a hundred missions. The managers estimated the risk to be of the order of one disaster in a hundred thousand missions. The difference, a factor of a thousand between the two estimates, was never reconciled and never openly discussed. The managers were in charge of the operations and made the decisions to fly or not to fly, based on their own estimates of the risk. But the technical facts that Feynman uncovered proved that the managers were wrong and the engineers were right.

  Feynman had two opportunities to educate the public about the causes of the disaster. The first opportunity concerned the technical facts. An open meeting of the commission was held with newspaper and television reporters present. Feynman was prepared with a glass of ice water and a sample of a rubber O-ring seal from a shuttle solid-fuel booster rocket. He dipped the piece of rubber into the ice water, pulled it out, and demonstrated the fact that the cold rubber was stiff. The cold rubber would not function as a gas-tight seal to keep the hot rocket exhaust away from the structure. Since the Challenger launch had occurred on January 28 in unusually cold weather, Feynman’s little demonstration pointed to the stiffening of the O-ring seal as a probable technical cause of the disaster.

  The second opportunity to educate the public concerned the culture of NASA. Feynman wrote an account of the cultural situation as he saw it, with the fatal division of the NASA administration into two noncommunicating cultures: engineers and managers. The political dogma of the managers, declaring risks to be a thousand times smaller than the technical facts would indicate, was the cultural cause of the disaster. The political dogma arose from a long history of public statements by political leaders that the shuttle was safe and reliable. Feynman ended his account with the famous declaration: “For a successful technology, reality must take precedence over public relations, for nature cannot be fooled.”

  Feynman fought hard to have his statement of conclusions incorporated in the official report of the commission. The chairman of the commission, William Rogers, was a professional politician with long experience in government. Rogers wished the public to believe that the Challenger disaster was a highly unlikely accident for which NASA was not to blame. He fought hard to exclude Feynman’s statement from the report. In the end a compromise was reached. Feynman’s statement was not included in the report but was added as an appendix at the end, with a note saying that it was Feynman’s personal statement and not agreed to by the commission. This compromise worked to Feynman’s advantage. As he remarked at the time, the appendix standing at the end got much more public attention than it would have if it had been part of the official report.

  Feynman’s dramatic exposure of NASA incompetence and his O-ring demonstrations made him a hero to the general public. The event was the beginning of his rise to the status of superstar. Before his service on the Challenger commission, he was widely admired by knowledgeable people as a scientist and a colorful character. Afterward, he was admired by a much wider public, as a crusader for honesty and plain speaking in government. Anyone fighting secrecy and corruption in any part of the government could look to Feynman as a leader.

  In the final scene of the comic book, Feynman is walking on a mountain trail with his friend Danny Hillis. Hillis says, “I’m sad because you’re going to die.” Feynman replies, “Yeah, that bugs me sometimes too. But not as much as you think. See, when you get as old as I am, you start to realize that you’ve told most of the good stuff you know to other people anyway. Hey! I bet I can show you a better way home.” And Hillis is left alone on the mountain. These images capture with remarkable sensitivity the essence of Feynman’s character. The comic-book picture somehow comes to life and speaks with the voice of the real Feynman.

  Twenty years ago, when I was traveling on commuter trains in the suburbs of Tokyo, I was astonished to see that a large fraction of the Japanese commuters were reading books, and that a large fraction of the books were comic books. The genre of serious comic-book literature was highly developed in Japan long before it appeared in the West. The Ottaviani-Myrick book is the best example of this genre that I have yet seen with text in English. Some Western readers commonly use the Japanese word manga to mean serious comic-book literature. According to one of my Japanese friends, this usage is wrong. The word manga means “idle picture” and is used in Japan to describe collections of trivial comic-book stories. The correct word for serious comic-book literature is gekiga, meaning “dramatic picture.” The Feynman picture book is a fine example of gekiga for Western readers.

  The title of Krauss’s book, Quantum Man, is well chosen. The central theme of Feynman’s work as a scientist was to explore a new way of thinking and working with quantum mechanics. The book succeeds in explaining without any mathematical jargon how Feynman thought and worked. This is possible because he visualized the world with pictures rather than with equations. Other physicists in the past and present describe the laws of nature with equations and then solve the equations to find out what happens. Feynman skipped the equations and wrote down the solutions directly, using his pictures as a guide. Skipping the equations was his greatest contribution to science. By skipping the equations, he created the language that a majority of modern physicists speak. Incidentally, he created a language that ordinary people without mathematical training can understand. To use the language to do quantitative calculations requires training, but untrained people can use it to describe qualitatively how nature behaves.

  Feynman’s picture of the world starts from the idea that the world has two layers: a classical layer and a quantum layer. Classical means that things are ordinary. Quantum means that things are weird. We live in the classical layer. All
the things that we can see and touch and measure, such as bricks and people and energies, are classical. We see them with classical devices such as eyes and cameras, and we measure them with classical instruments such as thermometers and clocks. The pictures that Feynman invented to describe the world are classical pictures of objects moving in the classical layer. Each picture represents a possible history of the classical layer. But the real world of atoms and particles is not classical. Atoms and particles appear in Feynman’s pictures as classical objects, but they actually obey quite different laws. They obey the quantum laws that Feynman showed us how to describe by using his pictures. The world of atoms belongs to the quantum layer, which we cannot touch directly.

  The primary difference between the classical layer and the quantum layer is that the classical layer deals with facts and the quantum layer deals with probabilities. In situations where classical laws are valid, we can predict the future by observing the past. In situations where quantum laws are valid, we can observe the past but we cannot predict the future. In the quantum layer, events are unpredictable. The Feynman pictures only allow us to calculate the probabilities that various alternative futures may happen.

  The quantum layer is related to the classical layer in two ways. First, the state of the quantum layer is what is called “a sum over histories,” that is, a combination of every possible history of the classical layer leading up to that state. Each possible classical history is given a quantum amplitude. The quantum amplitude, otherwise known as a wave function, is a number defining the contribution of that classical history to that quantum state. Second, the quantum amplitude is obtained from the picture of that classical history by following a simple set of rules. The rules are pictorial, translating the picture directly into a number. The difficult part of the calculation is to add up the sum over histories correctly. The great achievement of Feynman was to show that this sum-over-histories view of the quantum world reproduces all the known results of quantum theory and allows an exact description of quantum processes in situations where earlier versions of quantum theory had broken down.

  Feynman was radical in his disrespect for authority but conservative in his science. When he was young he had hoped to start a revolution in science, but nature said no. Nature told him that the existing jungle of scientific ideas, with the classical world and the quantum world described by very different laws, was basically correct. He tried to find new laws of nature, but the result of his efforts was in the end to consolidate the existing laws in a new structure. He hoped to find discrepancies that would prove the old theories wrong, but nature stubbornly persisted in proving them right. However disrespectful he might be to famous old scientists, he was never disrespectful to nature.

  Toward the end of Feynman’s life, his conservative view of quantum science became unfashionable. The fashionable theorists reject his dualistic picture of nature, with the classical world and the quantum world existing side by side. They believe that only the quantum world is real, and the classical world must be explained as some kind of illusion arising out of quantum processes. They disagree about the way in which quantum laws should be interpreted. Their basic problem is to explain how a world of quantum probabilities can generate the illusions of classical certainty that we experience in our daily lives. Their various interpretations of quantum theory lead to competing philosophical speculations about the role of the observer in the description of nature.

  Feynman had no patience for such speculations. He said that nature tells us that both the quantum world and the classical world exist and are real. We do not understand precisely how they fit together. According to Feynman, the road to understanding is not to argue about philosophy but to continue exploring the facts of nature. In recent years, a new generation of experimenters has been advancing along Feynman’s road with great success, moving into the new worlds of quantum computing and quantum cryptography.

  Krauss shows us a portrait of a scientist who was unusually unselfish. His disdain for honors and rewards was genuine. After he was elected to membership of the National Academy of Sciences, he resigned his membership because the members of the academy spent too much of their time debating who was worthy of admission in the next academy election. He considered the academy to be more concerned with self-glorification than with public service. He hated all hierarchies, and wanted no badge of superior academic status to come between him and his younger friends. He considered science to be a collective enterprise in which educating the young was as important as making personal discoveries. He put as much effort into his teaching as into his thinking.

  He never showed the slightest resentment when I published some of his ideas before he did. He told me that he avoided disputes about priority in science by following a simple rule: “Always give the bastards more credit than they deserve.” I have followed this rule myself. I find it remarkably effective for avoiding quarrels and making friends. A generous sharing of credit is the quickest way to build a healthy scientific community. In the end, Feynman’s greatest contribution to science was not any particular discovery. His contribution was the creation of a new way of thinking that enabled a great multitude of students and colleagues, including me, to make their own discoveries.

  *Quantum Man: Richard Feynman’s Life in Science (Norton, 2011).

  †First Second, 2011.

  16

  HOW TO DISPEL YOUR ILLUSIONS

  IN 1955, WHEN Daniel Kahneman was twenty-one years old, he was a lieutenant in the Israel Defense Forces. He was given the job of setting up a new interview system for the entire army. The purpose was to evaluate each freshly drafted recruit and put him or her into the appropriate slot in the war machine. The interviewers were supposed to predict who would do well in the infantry or the artillery or the tank corps or the various other branches of the army. The old interview system, before Kahneman arrived, was informal. The interviewers chatted with the recruit for fifteen minutes and then came to a decision based on the conversation. The system had failed miserably. When the actual performance of the recruit a few months later was compared with the performance predicted by the interviewers, the correlation between actual and predicted performance was zero.

  Kahneman had a bachelor’s degree in psychology and had read Clinical vs. Statistical Prediction: A Theoretical Analysis and a Review of the Evidence by Paul Meehl, published only a year earlier. Meehl was an American psychologist who studied the successes and failures of predictions in many different settings. He found overwhelming evidence for a disturbing conclusion. Predictions based on simple statistical scoring were generally more accurate than predictions based on expert judgment.

  A famous example confirming Meehl’s conclusion is the Apgar score, invented by the anesthesiologist Virginia Apgar in 1953 to guide the treatment of newborn babies. The Apgar score is a simple formula based on five vital signs that can be measured quickly: heart rate, breathing, reflexes, muscle tone, and color. It does better than the average doctor in deciding whether the baby needs immediate help. It is now used everywhere and saves the lives of thousands of babies. Another famous example of statistical prediction is the Dawes formula for the durability of marriage. The formula is “frequency of love-making minus frequency of quarrels.” Robyn Dawes was a psychologist who worked with Kahneman later. His formula does better than the average marriage counselor in predicting whether a marriage will last.

  Having read the Meehl book, Kahneman knew how to improve the Israeli army interviewing system. His new system did not allow the interviewers the luxury of free-ranging conversations. Instead, they were required to ask a standard list of factual questions about the life and work of each recruit. The answers were then converted into numerical scores, and the scores were inserted into formulas measuring the aptitude of the recruit for the various army jobs. When the predictions of the new system were compared to performances several months later, the results showed the new system to be much better than the old. Statistics and simple arithmetic tell us
more about ourselves than expert intuition.

  Reflecting fifty years later on his experience in the Israeli army, Kahneman remarks in Thinking, Fast and Slow* that it was not unusual in those days for young people to be given big responsibilities. The country itself was only seven years old. “All its institutions were under construction,” he says, “and someone had to build them.” He was lucky to be given this chance to share in the building of a country, and at the same time to achieve an intellectual insight into human nature. He understood that the failure of the old interview system was a special case of a general phenomenon that he called “the illusion of validity.” At this point, he says, “I had discovered my first cognitive illusion.”

  Cognitive illusions are the main theme of his book. A cognitive illusion is a false belief that we intuitively accept as true. The illusion of validity is a false belief in the reliability of our own judgment. The interviewers sincerely believed that they could predict the performance of recruits after talking with them for fifteen minutes. Even after the interviewers had seen the statistical evidence that their belief was an illusion, they still could not help believing it. Kahneman confesses that he himself still experiences the illusion of validity, after fifty years of warning other people against it. He cannot escape the illusion that his own intuitive judgments are trustworthy.