By Peter Weiss
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.
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2005/07/5118.jpg?resize=150%2C102&ssl=1)
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2005/07/5119.jpg?resize=150%2C138&ssl=1)
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2005/07/5121.jpg?resize=150%2C105&ssl=1)
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.