Number 78, May 4, 1992 by Phillip F. Schewe and Ben Stein|
PHYSICISTS CONFIRM BAKED ALASKA MODEL . Helium-3 will often remain in the superfluid A phase even when the temperature drops low enough for the liquid to enter another distinct superfluid state, the "B" phase, characterized by a change in orientation between helium pairs. Eventually, the B phase does grow from the "supercooled" A phase, but it typically develops at highly unpredictable, irreproducible times. In 1984, Anthony Leggett of the University of Illinois proposed that cosmic rays trigger the phase transition. At the recent APS Meeting in Washington, Peter Schiffer of Stanford showed experimental results in which Co-60 gamma rays, simulating the effect of cosmic ray muons, sped up the onset of the A-B phase transition by up to 1600 times. The results of the Stanford team agree closely with Leggett's model, which is named after "Baked Alaska" (in which meringue is baked around ice cream) because the cosmic rays create ionized electrons which can deposit their energies into localized spots in the liquid, creating cold regions surrounded by hot regions. It is in these cold regions that the B phase has a chance to nucleate and grow throughout the liquid.
THE HIGHEST ENERGY COSMIC RAYS arise when charged particles collide with "wandering" magnetic fields in our galaxy, according to scientists at Oxford. Developing a theory first proposed by Enrico Fermi in 1949, the scientists suggest that certain particles, already accelerated to high energies (10**13 to 10**14 eV per nucleon) in supernovas, can be driven to even higher energies (10**18 to 10**20 eV) through numerous interactions with irregular magnetic fields, perhaps those due to shock fronts of other supernova remnants in the galaxy. (Nature, 16 Apr. 1992.)
THE EARLIEST INFORMATION FROM THE BIG BANG may ultimately come not from the cosmic microwave radiation (carefully mapped by COBE) but from gravitational perturbations in the early universe. Although not yet detected directly, gravitational waves are an important ingredient in Einstein's theory of general relativity and several international teams are working to observe them with instruments such as the proposed LIGO interferometer. Unlike electromagnetic waves, gravitational waves, according to Einstein's theory, travel through space without being scattered or absorbed by matter. If sufficiently sensitive detectors are ever built, scientists may be able to detect gravity waves from the early moments after the big bang. Whereas electromagnetic waves (upon which most of our knowledge of the universe is based) did not start travelling freely through the universe until 300,000 years after the big bang, gravitational waves are believed to have started travelling through space as early as 10**-42 seconds after the beginning of the universe. (Scientific American, March 1992.)
50 STARS PACKED IN A REGION LESS THAN A LIGHT YEAR ACROSS were recently discovered by the Hubble Telescope. Sally Heap of NASA-Goddard, in her measurements of the stars, calculated that most of the stars were heavy---up to 100 times more massive than the sun---and therefore young. This finding suggests, contrary to previous assumptions, that it is as easy, if not easier, for heavy stars to form from a cloud of gas than it is for lighter ones. (The Washington Post, 21 April 1992.)