Since researchers first produced Bose-Einstein condensates in the lab in 1995, the ultracold collections of atoms, produced with laser and magnetic cooling and trapping, have exposed quantum phenomena in matter, such as the ability to generate coherent matter waves. Teams at JILA, a joint research institute of the National Institute of Standards and Technology and the University of Colorado, both in Boulder, have reported that the condensates are even weirder than they expected. Carl E. Wieman's group discovered that tuning the interaction of rubidium atoms in a condensate from repulsive to attractive with a magnetic field caused the condensate to explode. The researchers call the effect a "Bosenova." (In the March 12 issue of Physical Review Letters, a team at the University of Utrecht in the Netherlands attributed the phenomenon to elastic collisions between the atoms.) Researchers led by Eric Cornell and Charles Clark monitored the decay of a dark soliton -- a soliton defining the absence of matter or energy -- that they created in a rubidium condensate with microwaves and laser light. When they turned off the magnetic field trapping the atoms, the soliton wave in the condensate collapsed into a series of concentric vortex rings.