Talk about doing as you're told. Physicists now have made rubidium atoms act contrary to their nature. The atoms intrinsically attract each other, but new experiments near absolute zero have induced the atoms to repel one another instead.
In those experiments, Carl E. Wieman, Eric A. Cornell, and their colleagues observed surprising rubidium explosions that have yet to be explained. The small bursts are faintly akin to supernovas, say the researchers, who are at JILA, an institute in Boulder, Colo., jointly run by the University of Colorado and the National Institute of Standards and Technology (NIST).