Number 38 (Story #1), June 21, 1991 by Phillip F. Schewe and Ben Stein RECORD LOW TEMPERATURES HAVE BEEN ACHIEVED with a new laser technique. Steven Chu (415-723-3571) and his colleagues at Stanford University first lowered the temperature of a sample of sodium atoms using a system of lasers known as "optical molasses." The atoms were then pushed upwards (by another laser) into a cavity where a further selection of atoms by velocity could be accomplished. In this way, a secondary beam of atoms with a velocity spread (in one dimension) of only 270 microns/sec---or an equivalent "one-dimensional temperature" of 24 pK---was created (Physical Review Letters, 6 May 1991). Chu has devised an atom interferometer based on this cooling process. (Nature, 13 June 1991.)