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Number 423, April 14, 1999 by Phillip F. Schewe and Ben Stein
THE SCIENCE OF GAMMA RAY BURSTERS has now advanced to the point where a robot optical telescope, responding to signals from orbiting gamma-ray and x-ray telescopes, can within seconds swivel to a spot on the sky and photograph the visible component of the burst. Thus the object GRB990123 (with a redshift of 1.6) was glimpsed at optical wavelengths on January 23, 1999 at the crucial early stage of its eruption. Indeed this was the first time a GRB was detected optically while still belting out gammas. Judging by its gamma emissions it was either the most energetic GRB yet observed (if its energy were being spewed the same in all directions) or the observations constitute the first evidence for a beaming effect in GRB's. The object's afterglow was also watched by radio and infrared telescopes. These prompt measurements are important for understanding the burster's energy engine, which operates at full throttle for only about 100 seconds. (Science, 26 March 1999; Nature, 1 April 1999.)
THE MIGRATION OF PLUTONIUM is one of the gravest concerns for those planning long-term underground storage of nuclear waste. Plutonium, one of most toxic substances known, has a very low solubility in water and so it was once thought that this hazardous material would not move via groundwater. A new Livermore-Los Alamos study, however, suggests that plutonium might be making an aqueous journey aboard colloids (clays and zeolites). This is the chief explanation for the presence of plutonium in groundwater found 1.3 km away from a the scene of a Nevada nuclear test conducted 30 years before. The Department of Energy is now taking colloid transport into account in its formulation of a strategy for permanent waste storage. (Physics Today, April 1999.)
PHYSICS DEPARTMENT RANKINGS are almost always unfair, skewed, out of date, and misleading, but they're fun to look at anyway. US News and World Report recently ranked a multitude of professional schools and graduate departments in US universities. Their top graduate physics departments, in descending order, are Caltech, Stanford, Harvard, MIT, Princeton, Berkeley, Cornell, Chicago, and Illinois. Some subdisciplines are ranked too. In particle physics the top departments are Harvard, Berkeley, Stanford, Caltech, and Princeton. Nuclear physics: MIT, Michigan State, Univ Washington, Indiana, and Caltech. Condensed matter: Illinois, MIT, Stanford, Cornell, and Harvard. Atomic/molecular: MIT, Harvard, Stanford, Colorado, and Michigan. Astrophysics/space: Caltech, Harvard, Berkeley, Princeton, Chicago. Nonlinear/chaos: Maryland, Texas, Cornell, Chicago, and Georgia Tech. (For more rankings and for an explanation of the US News methodology, see this website: http://www.usnews.com/usnews/edu/beyond/gradrank/gbphysic.htm.)
POWDER LASER. Physicists at Northwestern have for the first time observed laser action in zinc oxide and gallium nitride powders (Cao et al., Physical Review Letters, 15 March). Semiconductor powders would normally absorb or even "halt" light (see Update 356), but because in the Northwestern samples the average length between scattering from the tiny (100 nm) grains is less than the light's wavelength, the light can propagate and even augment itself by stimulating further emission from atoms in the powder (Science, 2 April). This is laser action and the powder constitutes a sort of "random laser," one in which light moves not between the fixed mirrors of a cavity but, in random directions, among trillions of grains.
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