Number 50, October 3, 1991 by Phillip F. Schewe and Ben Stein CRITICAL CURRENT DENSITIES IN SUPERCONDUCTORS can be influenced with electric fields. Alex Müller, Georg Bednorz, and their colleagues at the IBM research center in Zurich incorporated a thin (70 angstroms) YBaCuO superconductor into a heterostructure transistor. This scheme provided electric fields as high as 2 x 105 V/cm; the presence of the fields modified critical current densities in the superconductor by as much as 50%. The researchers are also hoping to understand what effect the electric fields have on the movement of magnetic vortex lines inside superconductors. (Upcoming article in Physical Review Letters.) LIGHTNING ON VENUS may have been observed in a recent flyby by the Galileo spacecraft. Because of the qualities connected with Venus's thick atmosphere, most planetary scientists never considered Venus a prime candidate for lightning. However, Galileo's detection of 6 lightning-like bursts of electrical energy have jolted investigators to search for explanations. One possibility is that lightning on Venus may arise from volcanoes, specifically from particles rubbing against each other in the flows of hot rock rising to the surface. Such volcanic plumes have been known to cause lightning on Earth. Indeed the Magellan spacecraft has detected (and continues to look for) signs of volcanic ash on Venus, although active volcanoes are believed to be rare on the planet. (Science, 27 Sept. 1991.) THE TAU NEUTRINO MASS must be less than 35 MeV, according to scientists using the ARGUS detector at the DESY electron-positron collider in Hamburg. One hears about the search for neutrino mass, but that usually refers to the electron neutrino or muon neutrino. The tau (a heavy cousin of electrons and muons) and its associated neutrino are harder to produce and hence harder to study. Besides putting a limit on the tau neutrino's mass, the ARGUS group also measured its helicity; like the other neutrinos, the tau neutrino is left-handed. That is, the spin of the tau neutrino points in a direction opposite to its direction of motion. (CERN Courier, Sept. 1991.) BLUE LIGHT FROM A ZINC SELENIDE LASER DIODE , the shortest-wavelength light (490 nm) yet produced by a solid-state structure, has been demonstrated by scientists at 3M Company (Applied Physics Letters, 9 Sept. 1991). Before blue/green lasers can be used commercially, several technical problems must be overcome, in this case a low energy-into-light conversion efficiency and overheating. (Science News, 21 Sept. 1991.) SS433 IS NOT A BLACK HOLE , but rather a neutron star, assert scientists at the European Southern Observatory. First discovered in 1977, SS433 has been of great astronomical interest since its optical spectrum indicated the presence of hydrogen atoms moving at extremely high velocities. Some astronomers hypothesized that SS433 was a miniature version (right here in our galaxy) of the sort of energy engine---possibly a black hole---thought to drive active galaxies and quasars. The new ESO measurements indicate that SS433's mass is less than that of our sun and that therefore it cannot be a black hole. (ESO news release, 24 Sept. 1991.)