I will briefly review the creation and properties of Bose-Einstein condensation in a gas, and will then turn to recent research. Bose-Einstein condensation in a gas has made possible many novel capabilities for the manipulation and study of the behavior of quantum wave functions. One of these is the recently demonstrated ability to adjust the self-interaction of the wave function. In contrast to rubidium 87, for most values of magnetic field, rubidium 85 has a large negative scattering length, which means its Bose-Einstein condensate (BEC) will have a large attractive self-interaction. This limits the size of a stable ⁸⁵Rb condensate at zero Gauss to less than 100 atoms. However, there is a Feshbach resonance at 155 G that allows one to change the magnitude and sign of the self-interaction by adjusting the magnetic field. We have used this resonance to obtain a positive self-interaction and created condensates of ten thousand ⁸⁵Rb atoms. We can then change the magnetic field to produce attractive or repulsive interactions of almost any size and study the resulting dynamics and loss. We see a wide variety of behaviors including dramatic explosions and implosions of the condensate, with much of it as yet unexplained. Most striking is the "Bosenova" in which the condensate collapses in and then explodes out in a manner quite reminiscent of a supernova.

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