Number 38, 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.)
ADDITIONAL DISTANT QUASARS have raised serious questions about the universe's evolution. Reports of 27 more quasars, each ten to twelve billion years old and with redshifts between 4 and 5, provide statistically significant evidence that the universe settled down into lumpy structures earlier than predicted by existing theories. The findings, made by two groups of astronomers at a recent quasar workshop in Victoria, British Columbia, suggest that the distribution of matter in the universe was as inhomogeneous only one billion years after the big bang as it is today. (Science News, 15 June 1991.)
A NEW COPPER-OXIDE SUPERCONDUCTOR with an important structural difference from all other high-temperature superconductors has been discovered. Previous materials had non-superconducting oxide layers accompanying superconducting copper-oxide planes. Scientists at the University of Texas reported the discovery of a Sr-Nd-Cu-O compound lacking non-superconducting oxide layers. The material, with a transition temperature of 40 K, is an electron-doped superconductor. (Nature, 13 June 1991.)
EARTH'S MAGNETOTAIL was studied by the Galileo spacecraft on its sweep past the Earth in December 1990. According to Louis Frank of the University of Iowa, who spoke at the recent meeting of American Geophysical Union in Baltimore, the speed of electrons in the magnetotail plasma was measured by Galileo to be 10 times greater than the velocity measured by the ISEE-3 satellite in 1982, a finding that may necessitate a revision of magnetotail models. (Science News, 8 June 1991.)
THE ULYSSES SPACECRAFT , launched in October 1990 and halfway toward Jupiter, is now making measurements of solar radiation and particles. One of Ulysses's first tasks will be to map the complicated magnetosphere of Jupiter, which it will encounter in February 1992. Jupiter's gravity will hoist Ulysses into an unprecedented elliptical orbit that carries it out of the plane of the ecliptic and over the solar south pole in 1994 and the north pole in 1995. Ulysses will also study the interstellar medium, cosmic rays, and galactic x-ray and gamma-ray sources. (Eos, 28 May 1991.)
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