nanoquebec 2006-11-13 22:26
纳米科技的开山鼻祖: 物理學家理查德費曼
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[b]Richard Phillips Feynman [/b](May 11, 1918 – February 15, 1988) (surname pronounced FINE-man; /ˈfaɪnmən/ in IPA) was an influential American physicist known for expanding greatly on the theory of quantum electrodynamics, particle theory, and the physics of the superfluidity of supercooled liquid helium. For his work on quantum electrodynamics, Feynman was one of the recipients of the Nobel Prize in Physics in 1965, along with Julian Schwinger and Shin-Ichiro Tomonaga; in this work, he developed a way to understand the behavior of subatomic particles using pictorial tools now called Feynman diagrams.5a)ASH^Fq
He helped in the development of the atomic bomb and was later a member of the panel which investigated the Space Shuttle Challenger disaster. For all his prolific contributions, Feynman wrote only 37 research papers in his career. Apart from pure physics, Feynman is also credited with the revolutionary concept and early exploration of quantum computing, and first publicly envisioning nanotechnology, i.e. the ability to mass produce atomic-scale machines. He held the Richard Chace Tolman professorship in theoretical physics at Caltech.
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Feynman was a keen and influential popularizer of physics in both his books and lectures, notably a seminal 1959 talk on top-down nanotechnology called There's Plenty of Room at the Bottom and The Feynman Lectures on Physics, a three-volume set which has become a classic text. Known for his insatiable curiosity, gentle wit, brilliant mind and playful temperament [1], he is also famous for his many adventures, detailed in the books Surely You're Joking, Mr. Feynman!, What Do You Care What Other People Think? and Tuva or Bust!. As well as being an inspiring lecturer, bongo player, notorious practical joker, and decipherer of Mayan hieroglyphics, Richard Feynman was, in many respects, an eccentric and a free spirit. He liked to pursue many independent paths, such as biology, art, percussion, and lockbreaking. Freeman Dyson once wrote that Feynman was "half-genius, half-buffoon", but later changed this to "all-genius, all-buffoon".8B,W*F-Y"p3tu
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[b]Biography[/b]1zD]0_:T[
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Feynman was born in Far Rockaway, Queens, New York; his parents were Jewish and attended synagogue every Friday, although they were unritualistic in their practice of Judaism as a religion. The young Feynman was heavily influenced by his father, Melville Feynman, who encouraged him to ask questions in order to challenge orthodox thinking. His mother instilled in him a powerful sense of humor which he kept all his life. As a child, he delighted in repairing radios and had a talent for engineering. At school he was bright, but his measured IQ was merely above average at 124, which he would scoff at later. By age 15, he had mastered differential and integral calculus. He kept experimenting on and re-creating mathematical topics, such as the half-derivative (a mathematical operator, which when applied twice in succession, resulted in the derivative of a function), utilizing his own notation, before entering college. Thus, even while in high school, he was developing the mathematical intuition behind his Taylor series of mathematical operators. His habit of direct characterization would sometimes disconcert more conventional thinkers; for example, one of his questions when learning feline anatomy was: "Do you have a map of the cat?" (referring to an anatomical chart). When he spoke, it was with clarity..MZ@d5g!Q
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This was Richard Feynman nearing the crest of his powers. At twenty-three ... there was no physicist on earth who could match his exuberant command over the native materials of theoretical science. It was not just a facility at mathematics (though it had become clear ... that the mathematical machinery emerging from the Wheeler-Feynman collaboration was beyond Wheeler's own ability). Feynman seemed to possess a frightening ease with the substance behind the equations, like Einstein at the same age, like the Soviet physicist Lev Landau - but few others. — Genius : The Life and Science of Richard Feynman
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In his last year at Far Rockaway High School, Feynman won the New York University Math Championship. He applied to Columbia College but was rejected because of its Jewish quota[1]. Instead, he attended the Massachusetts Institute of Technology, where he received a bachelor's degree in 1939, and was named Putnam Fellow that same year. While there, Feynman had taken every physics course offered, and had taken a graduate course on theoretical physics while only in his second year. He obtained a perfect score on the entrance exams to Princeton University in mathematics and physics — an unprecedented feat — but did rather poorly on the history and english portions. Attendees at Feynman's first seminar included the luminaries Albert Einstein, Wolfgang Pauli, and John von Neumann. He received a Ph.D. from Princeton University in 1942; his thesis advisor was John Archibald Wheeler. Feynman's thesis applied the principle of stationary action to problems of quantum mechanics, laying the ground work for the "path integral" approach and Feynman diagrams.)HQ2D F(L6mt.\
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While researching his Ph.D, Feynman married his first wife, Arline Greenbaum. (Arline's first name is often spelled Arlene, as it is in Surely You're Joking, Mr. Feynman and What Do You Care What Other People Think?, two collections of Feynman anecdotes. However, in his own letters, Feynman wrote his wife's name as Arline; some of these letters were later published in the US under the title Perfectly Reasonable Deviations From the Beaten Track and in the UK under the title Don't You Have Time to Think?). Arline was diagnosed with tuberculosis, a terminal illness at that time, but she and Feynman were careful, and he never contracted the disease.oQ/x@PJ
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[b]The Manhattan Project[/b] ^[j/Y9c/lV9b
Feynman (center) with Robert Oppenheimer (right) relaxing at a Los Alamos social function during the top-secret Manhattan Project.!@ hf!vJZu
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Feynman (center) with Robert Oppenheimer (right) relaxing at a Los Alamos social function during the top-secret Manhattan Project.IB5e6alU"Q
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At Princeton, the physicist Robert R. Wilson encouraged Feynman to participate in the Manhattan Project—the wartime U.S. Army project at Los Alamos developing the atomic bomb. Feynman said he was persuaded to join this effort to help make sure that Nazi Germany did not build them first. On weekends, he visited his wife in a sanatorium in Albuquerque, right up until her death on June 16, 1945. He immersed himself in work on the project, and was present at the Trinity bomb test. Feynman claimed to be the only person to see the explosion without the very dark glasses provided, reasoning that it was safe to ignore instructions and look through a truck windshield as it would screen out the harmful ultraviolet radiation.
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As a junior physicist, his work on the project was relatively remote from the major action, consisting mostly of administering the computation group of human computers in the Theoretical division, and then, with Nicholas Metropolis, setting up the system for using IBM punch cards for computation. John G. Kemeny, later president of Dartmouth College, worked for Feynman at this time. Feynman actually succeeded in solving one of the equations for the project which were posted on the blackboards. However, they did not "do the physics right" and Feynman's solution was not used in the project.L|coX(p*~8@)X~
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Feynman's other work at Los Alamos included calculating neutron equations for the Los Alamos "Water Boiler", a small nuclear reactor at the desert lab, in order to measure how close a particular assembly of fissile material was to becoming critical. After this work he was transferred to the Oak Ridge facility, where he aided engineers in calculating safety procedures for material storage (so that inadvertent criticality accidents, e.g. by storing individually subcritical amounts of fissile material in proximity on opposite sides of a wall, could be avoided). He also did crucial theoretical and calculation work on the proposed uranium-hydride bomb, which was later proven to be infeasible.B
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Feynman was also sought out by the famous physicist Niels Bohr for one-on-one discussions. He later found out why. Most physicists were too much in awe of Bohr to argue with him, but Feynman had no such inhibitions, vigorously pointing out anything he considered to be flawed in his thinking. Feynman said he felt just as much respect for Bohr's reputation as anyone else, but that once anyone got him talking about physics, he couldn't help but forget about anything else. z$S!kM$G;z
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Feynman's ID badge photo from Los Alamos.#L[j:_}S
Feynman's ID badge photo from Los Alamos.
nanoquebec 2006-11-13 22:27
Due to the top secret nature of the work, Los Alamos was isolated; in his own words, "There wasn't anything to do there". Bored, Feynman claims he indulged his curiosity by learning to pick the combination locks on cabinets and desks used to secure papers. Feynman played many jokes on colleagues; in one case he found the combination to a locked filing cabinet by trying the numbers a physicist would use (it was 27-18-28 after the base of natural logarithms, e=2.71828...), and found that the three filing cabinets in which a colleague kept a comprehensive set of atomic bomb research notes (for his convenience while selecting material for declassification) all had the same combination. He left a series of mischievous notes as a prank, which initially spooked his colleague into thinking a spy or saboteur had actually gained access to atomic bomb secrets. (Coincidentally, Feynman once borrowed the car of physicist Klaus Fuchs in order to visit his sick wife. Fuchs was later discovered to be a spy for the Soviets.) On another occasion, he noted that a captain in his building at Los Alamos had a massive safe, better than anything the bomb scientists had, installed with much ado in his office. Some time after the captain left Los Alamos, Feynman discovered that the captain with the massive safe had (1) never bothered to change the combination from the single generic factory setting, so that even an amateur safecracker could open it, and (2) there was nothing important being kept in the safe anyway, whereas all the secrets of the bomb scientists were mostly kept in relatively insecure locked cabinets. These anecdotes are related by him in the book Surely You're Joking, Mr. Feynman!vm6x{R#d%St,HY
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On occasion, Feynman would find an isolated section of the mesa to drum Indian-style; "and maybe I would dance and chant, a little". These antics did not go unnoticed, and rumors spread about a mysterious Indian drummer called "Injun Joe". He also became a friend of laboratory head J. Robert Oppenheimer, who unsuccessfully tried to court him away from his other commitments to work at the University of California, Berkeley after the war.([
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[b]Early career: Cornell University[/b]
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After the project, Feynman started working as a professor at Cornell University, where Hans Bethe (who proved that the sun's source of energy was nuclear fusion) worked. However he felt uninspired there; despairing that he had burned out, he turned to less useful, but fun problems, such as analyzing the physics of a twirling, nutating dish, as it is being balanced by a juggler. (As it turned out, this work served him well in future research.) He was therefore surprised to be offered professorships from competing universities, eventually choosing to work at the California Institute of Technology at Pasadena, California, despite being offered a position near Princeton, at the Institute for Advanced Study (which included, at that time, such distinguished faculty as Albert Einstein).#S ^IC'T@U^4^4p
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Feynman rejected the Institute on the grounds that there were no teaching duties. Feynman found his students to be a source of inspiration and also, during uncreative times, comfort. He felt that if he could not be creative, at least he could teach. Another major factor in his decision was just a desire to live in a mild climate, a goal he seized on while having to put snow chains on his car's wheels in the middle of a snowstorm in Ithaca, New York.1dKHCRGPn
Feynman is sometimes called the "Great Explainer"; he took great care when explaining topics to his students, making it a moral point not to make a topic arcane, but accessible to others. His principle was that if a topic could not be explained in a freshman lecture, it was not fully understood yet. Feynman gained great pleasure from coming up with such a "freshman level" explanation of the connection between spin and statistics (that groups of particles with spin 1/2 "repel", whereas groups with integer spin "clump"), a question he pondered in his own lectures and which he solved in the 1986 Dirac memorial lecture. He opposed rote learning and other teaching methods that emphasized form over function, everywhere from a conference on education in Brazil to a state commission on school textbook selection. Clear thinking and clear presentation were fundamental prerequisites for his attention. It could be perilous to even approach him when unprepared, and he did not forget who the fools or pretenders were[2].H5S,u(|8XdJ]'`
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On one sabbatical year, he returned to Newton's Principia to study it anew; what he learned from Newton, he also passed along to his students, such as Newton's attempted explanation of diffraction.6le?0s.@i6HM&J:G:R Z
The Caltech years
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Feynman did much of his best work while at Caltech, including research in:Ysq_K#y g,Y L
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* Quantum electrodynamics. The theory for which Feynman won his Nobel Prize is known for its extremely accurate predictions[3],[4]. He helped develop a functional integral formulation of quantum mechanics, in which every possible path from one state to the next is considered, the final path being a sum over the possibilities.[5]
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* Physics of the superfluidity of supercooled liquid helium, where helium seems to display a lack of viscosity when flowing. Applying the Schrödinger equation to the question showed that the superfluid was displaying quantum mechanical behavior observable on a macroscopic scale. This helped enormously with the problem of superconductivity."LJ W E6?AZZ6N
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* A model of weak decay, which showed that the current coupling in the process is a combination of vector and axial. (An example of weak decay is the decay of a neutron into an electron, a proton, and an anti-neutrino.) Although E.C. George Sudharsan and Robert Marshak developed the theory nearly simultaneously, Feynman's collaboration with Murray Gell-Mann was seen as the seminal one, the theory was of massive importance, and the weak interaction was neatly described.
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He also developed Feynman diagrams, a bookkeeping device which helps in conceptualizing and calculating interactions between particles in spacetime, notably the interactions between electrons and their antimatter counterparts, positrons. This device allowed him, and now others, to work with concepts which would have been less approachable without it, such as time reversibility and other fundamental processes. Feynman famously painted Feynman diagrams on the exterior of his van.
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Feynman diagrams are now fundamental for string theory and M-theory, and have even been extended topologically. Feynman's mental picture for these diagrams started with the hard sphere approximation, and the interactions could be thought of as collisions at first. It was not until decades later that physicists thought of analyzing the nodes of the Feynman d
nanoquebec 2006-11-13 22:27
He also developed Feynman diagrams, a bookkeeping device which helps in conceptualizing and calculating interactions between particles in spacetime, notably the interactions between electrons and their antimatter counterparts, positrons. This device allowed him, and now others, to work with concepts which would have been less approachable without it, such as time reversibility and other fundamental processes. Feynman famously painted Feynman diagrams on the exterior of his van.
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Feynman diagrams are now fundamental for string theory and M-theory, and have even been extended topologically. Feynman's mental picture for these diagrams started with the hard sphere approximation, and the interactions could be thought of as collisions at first. It was not until decades later that physicists thought of analyzing the nodes of the Feynman diagrams more closely. The world-lines of the diagrams have become tubes to better model the more complicated objects such as strings and M-branes.9\q4T*mZfnHp
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From his diagrams of a small number of particles interacting in spacetime, Feynman could then model all of physics[6] in terms of those particles' spins and the range of coupling of the fundamental forces. Feynman attempted an explanation of the strong interactions governing nucleons scattering called the partonmodel. The parton model emerged as a rival to the quark model developed by his Caltech colleague Murray Gell-Mann. The relationship between the two models was murky; Gell-Mann refered to Feynman's partons derisively as "put-ons". Feynman did not dispute the quark model; for example, when the 5th quark was discovered, Feynman immediately pointed out to his students that the discovery implied the existence of a 6th quark, which was duly discovered in the decade after his death.
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After the success of quantum electrodynamics, Feynman turned to quantum gravity. By analogy with the photon, which has spin 1, he investigated the consequences of a free massless spin 2 field, and was able to derive the Einstein field equation of general relativity, but little more[7]. However, a calculational technique that Feynman developed for gravity in 1962- "ghosts" later proved invaluable in 1967 when Fadeev and Popov quantized i.e. understood the particle behaviour of the spin 1 theories of Yang-Mills -Shaw -Pauli, that are now seen to describe the weak and strong interactions, using Feynman's path integral technique. A "ghost" is a field which is spin-0 and so should be a boson but which is a fermion -disobeying the spin-statistics theorem. Because it does not propogate externally no effects of this are seen. Unfortunately, at this time he became exhausted by working on multiple major projects at the same time, including his Lectures in Physics.xnsXN
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While at Caltech, Feynman was asked to "spruce up" the teaching of undergraduates. After three years devoted to the task, a series of lectures was produced, eventually becoming the famous Feynman Lectures on Physics, which are a major reason that Feynman is still regarded by most physicists as one of the greatest teachers of physics ever. He wanted a picture of a drumhead sprinkled with powder to show the modes of vibration at the beginning of the book; the publishers misunderstood him, and the books carry a picture of him playing drums. Feynman later won the Oersted Medal for teaching, of which he seemed especially proud. His students competed keenly for his attention; once he was awakened when a student solved a problem and dropped it in his mailbox at home; glimpsing the student sneaking across his lawn, he could not go back to sleep, and he read the student's solution. That morning his breakfast was interrupted by another triumphant student, but Feynman informed this student that he was too late.
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Partly as a way to bring publicity to progress in physics, Feynman offered $1000 prizes for two of his challenges in nanotechnology. He was also one of the first scientists to conceive the possibility of quantum computers. Many of his lectures and other miscellaneous talks were turned into books such as The Character of Physical Law and QED: The Strange Theory of Light and Matter. He gave lectures which his students annotated into books, such as Statistical Mechanics and Lectures on Gravity. The Feynman Lectures on Physics required two physicists, Robert B. Leighton and Matthew Sands as full-time editors for several years. Even though they were not adopted by the universities as textbooks, the books continue to be bestsellers because they provide a deep understanding of physics. As of 2005, The Feynman Lectures on Physics have sold over 1.5 million copies in English, an estimated 1 million copies in Russian, and an estimated half million copies in other languages.
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In 1974 Feynman delivered the Caltech commencement address on the topic of cargo cult science, which has the semblance of science but is only pseudoscience due to a lack of integrity on the part of the scientist. He instructed the graduating class that "The first principle is that you must not fool yourself—and you are the easiest person to fool. So you have to be very careful about that. After you've not fooled yourself, it's easy not to fool other scientists. You just have to be honest in a conventional way after that."
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In the late 1970's, according to "Richard Feynman and the Connection Machine" [2], Richard Feynman played a critical role in developing the first parallel-processing computer and finding innovative uses for it in numerical computing and building neural networks as well as physical simulation with cellular automata (such as turbulent fluid flow), working with Stephen Wolfram at Caltech.
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[b]Personal life[/b]