SOUND WAVES AND SUPERNOVAS IN BOSE-EINSTEIN CONDENSATES (BECs). Since 1995, scientists have been creating the BEC state, in which a cloud of atoms is cooled to near-absolute-zero temperatures, falling into the same quantum state and acting as a single entity (Update 233). At this month's APS/AAPT meeting in Washington, three researchers spoke on this subject. (1) Randy Hulet of Rice University reported that BECs of lithium atoms--different from other BECs in that the lithium atoms attract rather than repel each other--are limited to a size of approximately 1500 atoms. According to some predictions, adding more atoms than this would cause the BEC to undergo a "macroscopic quantum tunneling" in which the condensate would collectively transform from a low-density to a high-density state, forming molecules which would then release excess heat and cause the BEC to blow apart like a supernova. (2) Studying BECs of rubidium atoms, Eric Cornell of NIST and the University of Colorado discussed experiments confirming that BECs are significantly more uniform in density than comparable clouds of cold atoms in a non-BEC state. (3) Using laser light to excite a specific spot on his cigar-shaped BEC of sodium atoms, Wolfgang Ketterle of MIT described how the resulting disturbance in a typical condensate propagates at about 5 millimeters per second, roughly 70,000 times slower than the speed of sound in air. (Writeup and figure from Hulet's group at APS Virtual Pressroom)