Wednesday, July 22, 2009

Cartoon-Like Pictures in Particle Physics

The Web site of American Physical Society has the pages entitled Physical Review Focus, on which selections from the journals Physical Review and Physical Review Letters are explained for students and researchers in all fields of physics. Besides such selections, the pages also carry "Landmarks," which introduce important papers from the archives of Physical Review.

A recent article [1] of Physical Review Focus treated Richard Feynman's paper in 1949 [2]. In this paper Feynman used for the first time cartoon-like pictures (examples can be seen in [1]; explanations are given in [3]) of straight and wiggly lines representing real and virtual particles interacting each other ("virtual particles" appear in intermediate, unobservable, stages of a process, and work as the mediators of the forces of interactions). The pictures enabled him to obtain easy answers to difficult problems in quantum electrodynamics. Then these so-called Feynman diagrams quickly became an essential tool for particle physicists, and Feynman shared the Nobel Prize with Sin'itiro Tomonaga and Julian Schwinger in 1965 (the independent work by the latter two physicists were published in [4] and [5]).

Generally, visualizing the images of new concepts often helps one understand those concepts quickly. Feynman diagrams, which translate the essence of complicated mathematical expressions into simple pictures, are therefore a good and indispensable device in studying the mystery of the deep physics in the microscopic world.

  1. Landmarks: Powerful Pictures, Physical Review Focus Vol. 24, Story 3 (July 20, 2009).
  2. R. P. Feynman, "Space-Time Approach to Quantum Electrodynamics," Phys. Rev. Vol. 76, p. 769 (1949).
  3. Feynman Diagrams Virtual Visitor Center, SLAC, Stanford University.
  4. S. Tomonaga and J. R. Oppenheimer, "On Infinite Field Reactions in Quantum Field Theory," Phys. Rev. Vol. 74, p. 224 (1948).
  5. J. Schwinger, "Quantum Electrodynamics. I. A Covariant Formulation," Phys. Rev. Vol. 74, p. 1439 (1948).

Monday, July 20, 2009

Feynman's Lectures on Microsoft Web Site

An article [1] of has reported that Bill Gates has bought the rights to seven lectures by the late Richard Feynman, which were filmed by the BBC in 1964 — a year before Feynman shared the Nobel Prize in Physics [with Sin'itiro Tomonaga and Julian Schwinger] — and that you can watch them for free at [2]. All we need to do is download and install a bit of software from Microsoft, which takes us a minute or two.

Feynman presented these lectures as the Messenger Lectures at Cornell University in the United States. Titles of them are
  1. The Law of Gravitation, an example of Physical Law
  2. The Relation of Mathematics to Physics
  3. The Great Conservation Principles
  4. Symmetry in Physical Law
  5. The Distinction of Past and Future
  6. Probability and Uncertainty the Quantum Mechanical Law of Nature
  7. Seeking New Laws
Under the movie we can read Feynman's words, so that non-native speakers of English who are unaccustomed to listening lectures in English can well enjoy these lectures. The Messenger Series of lectures is also available as a book [3]. In the foreword of the book, we read, to our astonishment, that Feynman delivered these lectures not from a prepared manuscript but extempore from a few notes.

  1. H. Johnston, Watch Richard Feynman’s lectures for free, blog (July 17, 2009).
  3. R. Feynman, The Character of Physical Law (Penguin, 2007).