Peter Weiss in Science News Online:
The next time you get a letter, its stamp might have printed on it examples of one the greatest conceptual tools of modern physics. The tool is a kind of line drawing, and a bunch of those drawings appear on the face of a new U.S. postage stamp honoring a legendary physicist, the late Richard P. Feynman.
Those drawings are ubiquitous in physics today. “If you walk into a physics building anywhere in the world, you see those [drawings] on the blackboards,” says David I. Kaiser, a physicist and historian at the Massachusetts Institute of Technology (MIT) who recently wrote a book about the sketches.
Created by Feynman in the 1940s to solve one of the most vexing puzzles of theoretical physics at the time—a feat for which he would share the 1965 Nobel Prize in Physics—the drawings give physicists a quick, intuitive way to organize and understand difficult calculations. As scientists were uncovering droves of new subatomic particles in the 1950s and 1960s, Feynman diagrams—as the drawings came to be known—offered a means for visualizing the unfamiliar entities and their interactions.
More here.