No. 13: Winter 1981
A little anomaly may go a long way. Accelerator experiments at Berkeley have again focussed attention on those few fragments from nuclear reactions that have unexpectedly short trajectories. About 6% of these fragments travel only about one tenth as far as prevailing physical laws say they should. These anomalously short mean free paths are not new, having first cropped up in 1954, but they have gone unexplained for 26 years. Current speculation is that the anomalous fragments somehow change their identities, making them more susceptible to collision (i.e., their collision cross sections spontaneously increase by ten times). But no known transformations of matter can do this! Consequently, we are left with the possiblity that some entirely new form of matter exists.
(Robinson, Arthur L.; "A Nuclear Puzzle Emerges at Berkeley," Science, 210:174, 1980.)
Comment. Just a few weeks ago, some nuclear physicists were saying that the advent of quark theory explained everything in their field.