From: revu@ellis.uchicago.edu (Sendhil Revuluri)
Subject: Physics News Update #111 (1/21)
Summary: Latest Physics News Update
Keywords: physics news interesting banana
Reply-To: revu@midway.uchicago.edu
Organization: University of Chicago
Date: Fri, 22 Jan 1993 05:39:14 GMT

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Sendhil Revuluri (s-revuluri@uchicago.edu)
University of Chicago

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PHYSICS NEWS UPDATE
A digest of physics news items prepared by Phillip F. Schewe, AIP
Public Information
Number 111   January 21, 1993

SQUID DETECTORS OPERATING IN THE
MILLIATTOVOLT range have been able to measure a tiny
resistance in a YBaCuO thin-film superconductor, even in low
magnetic fields and for low currents  (F.C. Wellstood et al., 4 Jan.
1993 Physical Review Letters).  The resistance arises from noise
in magnetic flux lines which do seem to penetrate the sample even
though the external fields used are far below the critical field at
which penetration is supposed to commence.  By the way, although
the scientists in this Maryland-AT&T-Berkeley collaboration use
the prefix milli-atto to denote 10 raised to the -21st power, the
official name for this prefix is "zepto," or just z.  For those who
would go further yet, the name for 10**-24 is "yocto."  (Science
News, 16 Jan. 1993.)

CHANGES IN THE EARTH'S ROTATION RATE occur at the
level of several parts in 10**8.  Using laser ranging (bouncing
radar waves off the Moon or satellites) and very long baseline
interferometry, length-of-day (LOD) measurements can detect 0.03
msec changes.  Jean Dickey, a JPL geophysicist, cites three main
types of LOD change: a linear increase owing to tidal dissipation;
larger, irregular variations, on the scale of decades, owing to core-
mantle interactions; and shorter-term (seasonal) changes from the
angular momentum exchange between crust and atmosphere. 
(Eos, 12 Jan. 1993.)

HOW ELEMENTARY PARTICLES COME TO HAVE THE
MASS THEY DO is "the most important outstanding problem in
particle physics today," says Berkeley scientist Lawrence Hall.  The
standard model is not much help: indeed, certain of the known
particle masses are used as input parameters for the theory.  Hall
and his colleagues Savos Dimopoulos of Stanford and Stuart Raby
of Ohio State have advanced a new model, reworking parts of the
existing theories, which makes six specific testable predictions
(Phys. Rev. Lett., 30 Mar. 1992) on such topics as B-meson decay,
proton decay, and the top quark (their estimate for the mass: 188
GeV).  The top is being pursued at Fermilab and new proton-
decay experiments are being readied in Japan---the Super
Kamiokande detector---and Italy---the Icarus detector.  (Science,
8 Jan. 1993.)

BRIGHTNESS VARIATIONS IN SUN-LIKE STARS were as
large as 2.7% for a sample of 33 stars studied over eight years. 
The average year-to-year brightness variation for those stars
similar to the Sun in age was 0.16% (rms), compared with 0.04%
for the Sun.  The scientists who made the photometry observations
of the stars at the Lowell Observatory conclude (contact Sallie
Baliunas, Smithsonian Astrophysical Observatory, 617-495-7415)
that although the Sun is in an unusually steady phase right now,
eras of larger-amplitude variability, such as the Maunder Minimum
(AD 1645-1715), may occur more often than previously believed
and that reconstructions of past solar brightness should take this
into account.  (Nature, 17 Dec. 1992.)

CORRECTION.  The small galaxy group harboring a dense
concentration of dark matter (Update 109) is called NGC 2300,
not NGC 200.  The article on atomic hydrogen in a magnetic trap
(O.J. Luiten et al., mentioned in Update 110) will appear on 1
February 1993, not Jan. 26.