One of the Universe’s most common particles has left physicists completely stumped. The proton, a fundamental constituent of the atomic nucleus, seems to be smaller than thought. And despite three years of careful analysis and reanalysis of numerous experiments, nobody can figure out why.
The most exciting phrase to hear in science, the one that heralds new discoveries, is not “Eureka” but “That’s funny…”
—Isaac Asimov (1920–1992) …