Written by | Takeko
Source: Institute of New Principles
In 1958, Freeman Dyson was busy helping with the design of the TRIGA reactor and the Orion project, and for several summers before that, he spent several summers at the University of California, Berkeley, working on the problem of condensed matter with another prominent physicist, Charles Kittel.
That same spring, Philip Anderson got a call from Berkeley, and the other end of the phone said to him, "Here's a funding that Freeman Dyson used a few summers ago, but this year he's going to design a reactor, are you interested in coming here?" Anderson was very surprised, but soon gladly agreed. This summer at Berkeley, Anderson wrote one of the most important papers of his academic career.
Dyson and Anderson are both titans in the physics world, and they seem to have little intersection, but the trajectory of life is vaguely intertwined. The two were born in December 1923, just two days before and after their birthdays, and died in early 2020. They have both traveled between American and British cultures, making groundbreaking contributions to theoretical physics. It wasn't until the first energy crisis that they met at the American Physical Society's Energy Symposium.
In childhood and adolescence, Anderson and Dyson's life trajectories are very similar. They have always been honors students, from the top high schools in the United Kingdom and the United States to the world's top universities, they also showed extraordinary talent and interest in mathematics and physics. The two teenagers are like two parallel lines, growing up on both sides of the Atlantic.
On December 13, 1923, the family of Harry Warren Anderson, a professor of plant pathology at the University of Illinois, ushered in a new life, and they named the child Philip. It was an academic family, and although Philip's grandfather was a farmer, both his father and uncle became professors. Philip's maternal grandfather was a professor of mathematics and his uncle was a professor of English. In Philip's own words, it was a "stable but poor family of Midwest scholars."
Two days later, on December 15, 1923, across the ocean in Crothorne, England, Freeman Dyson was born. Freeman's father, George Dyson, was a famous English musician and composer who was later knighted as the High Lord of Victoria.
Philip Anderson lived in Illinois until he was 17. He once recalled that his parents had a group of warm friends who loved nature and often traveled together, especially on Saturdays. The happiest times of his childhood were hiking with a group of people, picnicking, and singing around a campfire. Among this group, there are also some physicists. They discovered Philip's shown interest in physics and encouraged him to enter the field of physics.
As a child, Freeman may have enjoyed "imaginary adventures" more. In the Dyson family's family file, there is an unfinished novel that Freeman began writing at the age of 8, which tells the story of a lunar expedition to observe the upcoming asteroid impact. He grew up loving reading and computing, and Jules Verne's books have always been on his reading list, which also includes the works of many physicists who are good at popular science and write beautifully.
In 1940, at the age of 16, Anderson entered Harvard university with a full national scholarship from the nation's top college high school. He took many courses in his first semester and soon found himself more comfortable with math and physics. In 1941, Freeman Dyson was admitted to Cambridge University from Winchester College in the United Kingdom to study mathematics.
It was the outbreak of World War II. During the war, the two young men had similar experiences. In 1943, Anderson went to the Naval Research Laboratory to conduct antenna research. Dyson similarly left campus to join RAF Bomber Command as a civilian scientist. He used mathematical knowledge to plan more effective bombing operations. However, the experience also brought him inner condemnation, with Dyson saying in a later interview that he was "calculating how to kill most economically."
In 1945, the man-made disaster that swept through all mankind finally came to an end. At the end of the war, the two young men returned to the peaceful and quiet campus. Anderson stayed at Harvard University to begin his doctoral studies. Some of the theoretical frontiers of nuclear fission that were opened during the war sparked Dyson's interest, and after two years at Trinity College, he went to Cornell University across the ocean in 1947 as a mathematics graduate to begin physics research.
At this point, the trajectory of the two people's lives began to gradually approach. Here, it is necessary to mention another famous theoretical physicist, Julian Schwinger.
At that time, Schwinger had just left Purdue University to teach at Harvard University. During his Ph.D., Anderson chose John van Vleck, whom he had known earlier, as his mentor, rather than Schwenger, who had become an "academic star." Anderson later recalled that it was a "wise" choice, because Schwinger's "office door had to be lined up", while Van Flake, who was already acquainted, had more time and energy to focus on Anderson.
But Anderson still had the opportunity to take some of the advanced courses taught by Schwinger, and he found that the complex mathematical techniques of modern quantum field theory learned in Schwinger's class were very useful in the experimental problem of new RF spectral line widening.
In 1947, Dyson, who had just arrived at Cornell University, studied under Hans Bethe. Bate was one of the leaders of the Manhattan Project and, along with Richard Feynman, proposed the Bate-Feynman formula for calculating the efficiency of a nuclear bomb. But for Dyson, what really "changed lives" is still related to Schwenger and quantum electrodynamics (QED).
Feynman was a young and promising professor at Cornell University who had invented a new way to describe the behavior of electrons and photons (and electrons' antiparticles, the positron). But by this time Schwenger and another physicist, Sin-Itiro Tomonaga, had independently proposed a different approach. Each approach seems to satisfy both the dire tests of quantum mechanics and special relativity. These are very individual "academic bigwigs", and even arguably the smartest minds in history, and the cutting-edge research they publish is not an easy task to understand. So the question is – who is right?
Dyson, who was in his early 20s at the time, was particularly interested in these theories. In the spring of 1948, he and Feynman embarked on a fabled road trip. After months of studying Feynman's theory, he spent another 6 weeks in Ann Arbor listening to Schwenger's ideas. After communicating with these "strongest brains", on the Greyhound bus to the Institute for Advanced Study in Princeton, he "had a flash of inspiration" and finally understood that the two theories are mathematically equivalent! That is, they are just talking about the same thing in different ways, and the final answer is actually a QED that describes how light and matter interact. Feynman called QED "a treasure of physics and our proudest asset."
Dyson translated Feynman diagrams into mathematical language.
In 1949, the 26-year-old Dyson published a detailed proof paper in the Physics Review entitled "The Radiation Theories of Tomonaga, Schwinger, and Feynman", which became one of the milestones in the history of modern physics. This central problem in physics is perfectly unified by Dyson with a mathematical solution. And his so-called "flash of inspiration" is actually the result of his solid mathematical skills and training. Dyson's insight gave a more accurate understanding of subatomic particles that conform to quantum mechanics and special relativity, allowed Feynman diagrams to be used for the first time to calculate scattering amplitude, and made perturbation QED logically understandable.
Dyson published the paper "The Radiation Theories of Tomonaga, Schwinger, and Feynman."
After the publication of this heavyweight paper, a Ph.D. seemed superfluous to Dyson. In fact, strictly speaking, Dyson did not get a doctorate, but this did not prevent people from calling him "Dr. Dyson", let alone the recognition of him by the academic community. Two years after the paper was published (1951), Cornell University still hired him as a professor of physics without a ph.D. In 1953, he moved to Princeton as a professor at the Institute for Advanced Study, where he remained until his retirement.
Dyson did not regret the lack of a degree, because he had been very opposed to the current doctoral degree system. In an interview with Quantum magazine, he said bluntly that a doctoral certificate does not say anything now. Dyson called himself "lucky" that in the more chaotic postwar state, he was able to remain in academia, although he did not have a doctorate. He even said: "I am proud that I don't have a PhD, I have 6 children, none of them have a PhD, that's my contribution." ”
He calls himself a "rebel" and enjoys jumping from one problem to another, spanning theory and experimentation. Later, he worked as a consultant for General Atomics and came up with the bold idea of the famous "Dyson Ball" in the 1960s.
Later in the story, Schwenger, Asahine and Feynman shared the 1965 Nobel Prize in Physics for their research. Dyson has also won almost many international academic awards, including the Wolf Prize, but he has never been associated with the Nobel Prize. Many people think that Dyson's contribution to QED is also "Nobel Prize-level", but he himself does not feel jealous of it. In a 2009 interview, he said: "I think that if you want to win the Nobel Prize, you have to focus your attention for a long time, grasp some deep and important questions, and explore them for more than 10 years, almost without exception." And that's not my style. ”
On the other hand, in the same year that Dyson published his QED-related papers, Anderson graduated with a Ph.D. from Harvard University and subsequently entered Bell Labs. In the decades that followed, he delved into a range of issues in the field of condensed matter physics, contributed to the understanding of ferromagnetism and antiferromagnetism, and provided new insights into spontaneous symmetry breaking in physics.
Our understanding of the electronic properties of metals and semiconductors is based on the notion that electrons with a certain momentum can freely pass through one lattice, while other electrons cannot. This is reflected in Felix Bloch's 1928 theory of quantum conduction, which describes the lattice as a periodic electric potential energy through which some electrons (manifested as "waves of matter") can be easily diffracted. Anderson calculated how the system would change if potential energy lost its periodicity. This can happen if the lattice remains periodic, but there are different potential energy values at different lattice sites.
Anderson found that the electron might not be able to move through such a "disordered" lattice, but instead would be trapped by specific atoms. If the disorder is strong enough, electrons cannot form an electric current due to destructive interference between different scattering paths. Instead, they are localized and cannot be propagated in space. This prediction came to be known as Anderson localization.
Anderson's groundbreaking research on the electronic structure of magnetic and disordered systems not only became the cornerstone of this field, but also profoundly influenced the development of applications such as electronic exchange and memory storage devices in computers. In 1977, with these findings, he shared the Nobel Prize in Physics with his doctoral supervisors, Van Flake, and Nevill Mott.
In addition to this, in 1962, Anderson published a paper on how photons obtain quality. Two years later, Anderson's paper was also cited in Peter Higgs' paper on the most important mechanism of quality sources.
Anderson also contributed to the philosophy of science. In 1972, he published a famous article in the journal Science, "More is different," which expounded the limitations of reductionism. Reductionism holds that, theoretically, all science can be derived from a few basic principles, and Anderson believes more in emergence, that is, our observations at one level follow a law at a higher source level, but those observations are not necessarily inferred at that more fundamental level.
Anderson published the famous paper "More is different".
Although Anderson has been with Bell Labs since his Ph.D. graduation, he has also worked part-time at various institutions. Anderson mentioned the importance of friends and the environment in his speech. He is more than happy to spark with different thinkers in top academic institutions.
For eight years from 1967, Anderson was a professor of physics at Dyson's alma mater, the University of Cambridge in the United Kingdom, and was hired as a fellow at Jesus College. In his own words, it's a shuttle between two cultures. In 1975, Anderson returned to the United States and his job at Cambridge university was replaced by a part-time job at Princeton University. It was not until his retirement from Bell Labs in 1984 that he became a full professor at Princeton University.
Dyson retired from the Institute for Advanced Study in Princeton in 1994. In 1996, Anderson became a Professor Emeritus at Princeton University. But for those who need to take pleasure from relentless exploration, "retirement" is only a formal concept.
Since the 1970s, Dyson has focused on writing, publishing several popular science books. Even in 2012, at the age of 88, he collaborated with physicist William Press to publish a paper on the prisoner's dilemma. In Dyson's words, retirement "the only change is that there is no pay anymore." I still have an office, I have secretarial help with what I need to do, and I have my seat at the lunch table. Another benefit is that you don't have to attend teacher meetings anymore. ”
Anderson was still active in physics during his old age. Even after becoming an emeritus professor, he still appears regularly at Princeton University. In 2006, he was named "the world's most creative physicist."
Anderson has also been publishing book reviews and other works. In 2013, he published a book review in Physical World titled "An iconoclast's career"—a review of Dyson's biography by Phillip Schewe.
At the beginning of 2020, we lost two masters of physics. Freeman Dyson died in Princeton on Feb. 28 at the age of 96. A month later, on March 29, Philip Anderson also passed away at Princeton. Although they rarely intersect in life, physics binds their names together.
Image design: Yue Yue; Source: Wikicommons
Reference Sources
[1]http://www.sns.ias.edu/sites/default/files/files/Dyson_Biography_detailed(1).pdf
[2]https://www.aip.org/history-programs/niels-bohr-library/oral-histories/23362-2
[3]https://physicsworld.com/a/an-iconoclasts-career/
[4]https://www.nobelprize.org/prizes/physics/1977/anderson/biographical/
[5]https://www.nytimes.com/2020/02/28/science/freeman-dyson-dead.html
[6]https://www.aip.org/history-programs/niels-bohr-library/oral-histories/24312-1
[7]https://www.ias.edu/press-releases/2020/freeman-j-dyson-1923%E2%80%932020
[8] The Conspiracy of Prime Numbers, ed. Thomas Lin, CITIC Publishing Group Nautilus, March 2020
[9]https://www.nytimes.com/2009/03/29/magazine/29Dyson-t.html
[10]https://www.princeton.edu/news/2020/03/30/nobel-laureate-and-princeton-physicist-philip-anderson-dies-age-96
[11]https://physicsworld.com/a/condensed-matter-physics-pioneer-philip-anderson-dies-aged-96/
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