ONE OF THE MOST CONVECTIVE FLUIDS EVER OBSERVED IN THE LABORATORY has been created by researchers in France (Bernard Castaing, CNRS, hydrodyn@labs.polycnrs-gre.fr). Convection is the process in which heat is carried by parcels of moving fluid. For example, heating a pan of water causes the lowermost layer of fluid to expand and become less dense, making it rise and carry its heat upward. Convection is characterized by the Rayleigh number (Ra), the ratio of the buoyant force of rising fluid to the product of viscosity (resistance to motion in the fluid) and the thermal diffusivity (how quickly temperature differences in the fluid get smoothed out). Heating a container of cold helium gas (4-5 Kelvins in temperature) from the bottom, the researchers measured Ra numbers in excess of 10¹⁴, a record matched only by a group at Chicago (X.-Z. Wu et al., Phys. Rev. Lett., 30 April 1990). However, when Ra exceeded 10¹¹, the researchers identified for the first time a transition in the fluid layers near the container's boundaries, from a laminar (streamline) flow of heated material to the "ultimate" regime of convection (beyond which no new regime exists) in which the whole fluid becomes turbulent and consequently transports heat more efficiently. Rayleigh-Bernard (RB) convection, as it is known, is important in many natural processes, such as the movement of air around the globe. (X. Chavanne et al., Upcoming article in Physical Review Letters., tent. 27 Oct.)

HIGH-PRECISION COSMOLOGY will be possible in the next few years through new measurements of the cosmic microwave background (CMB)---with NASA's MAP satellite and the European's Planck satellites---and expanded catalogs of galaxy locations with the Sloan Digital Sky Survey (a million redshifts to be recorded in 5 years). Several years ago the COBE satellite took the temperature of the universe; the new CMB and galaxy studies should go far to "weigh" the universe and determine whether it will expand forever or collapse. Actually, the universe's vitae are expressed more scientifically in terms of parameters such as omega (energy density), lambda (cosmological constant), and H (Hubble constant). Max Tegmark of the Institute for Advanced Study (max@ias.edu) has estimated the effect of the new data on each of these parameters. For example, big blobs in the CMB map imply a large value for omega, which in turn suggests the universe will collapse. Small blobs imply a smaller omega and an expanding universe. Higher resolution samplings of tiny portions of the CMB, such as that made with the Saskatoon detector in northern Canada, observe blobs at a size that stands midway between that corresponding to an open and shut universe. The new data should settle the matter. (Tegmark,in Physical Review Letters, tent. 3 Nov.; see figure at Physics News Graphics)

SEVEN YEARS OF PHYSICS--the entire run of Physics News Updates---is now available in searchable form on the AIP Website at this address: www.aip.org/physnews/update. Just type in a term or expression and up come references to items in past Updates. For example: searching for "leptoquark" hauls up 2 items; "steven chu" finds 3 hits; "DNA" results in 13. All past Updates can be viewed by going to the archives. See also Physics News Graphics, our growing archive of physics figures, most of which accompany Update items. Subscription reminder: to add or delete your name from the distribution list, follow these steps---send a message to listserv@aip.org, leave the "subject" blank, and in the letter itself specify either the expression add physnews or delete physnews.