Attractive and Demure; May 1993; Scientific American Magazine; by Russell Ruthen; 1 Page(s)

The devil is in the details. Although for decades physicists have understood how the fundamental forces of nature influence some of the most esoteric elementary particles, they have suddenly realized that they do not know what actually holds the nucleus of an atom together. "For a long time, we have had a very simple picture, but now it seems too simplistic," comments George F. Bertsch, a nuclear theorist at the University of Washington.

Physicists had assumed that the protons and neutrons that make up the core of an atom attract one another by exchanging a particle known as a pi meson, or pion. But recent results from particle accelerators show that the pion is responsible only for conveying the nuclear force over long distances. And no one has figured out what is happening over the short range.