Number 191, August 23, 1994 by Phillip F. Schewe and Ben Stein
ULYSSES NEARS THE ANTIPODES. Like Homer's wayfaring hero, the Ulysses
spacecraft has now gone where others have never gone before, in this case
beneath the Sun's south pole. Ulysses' orbit around the sun (at a radius
of 2.4 astronomical units) should take it over the north pole next summer.
Two discoveries so far: the solar magnetic field strength has not increased
toward the pole as it was supposed to do; and the speed of the solar wind
has been measured to be twice as great at the pole as in the plane of the
solar equator. (Science News, 6 August 1994.)
PLASMA CRYSTALS, macroscopic ensembles of dust particles held in a crystal-like
array by a plasma of weakly ionized argon atoms, have been devised by a
Garching-Cologne-Iowa team of physicists (H. Thomas et al., Physical Review
Letters, 1 August). The dust assembly, consisting of 7-micron plastic balls,
is contained between two electrodes and illuminated by a laser beam. Even
with the unaided eye, one can see that the particles arrange themselves
regularly in as many as 18 planes parallel to the electrodes. Plasma crystals
might be useful in modeling interstellar clouds, which are dusty plasmas,
and in plasma-assisted manufacturing techniques, prominent in the microelectronics
industry. (Science News, 6 August; Nature, 11 August.)
A DIGITAL HOLOGRAPHIC STORAGE SYSTEM , one actually integrated with a
computer hard drive, has been developed by scientists at Stanford. In such
a system data is converted into light patterns. The light waves enter a
photorefractive medium, where they bring about microscopic rearrangements
of electric charge which in turn affect the local index of refraction.
To read out the data, a reference laser beam is sent into the medium; the
refracted beam, bearing the decoded data, is detected with a charge-coupled
device. Data can be stacked up in the hologram by recording at several
angles. By home-computer standards, the Stanford results so far are modest:
total storage capacity of 163 kB and a data transfer rate of 6.3 MB per
second. The researchers believe future hologram performance should be much
better: terabytes of storage and transfers above 1 gigabit per second.
(John F. Heanue, Matthew C. Bashaw, Lambertus Hesselink, Science, 5 August.)
"THE LIFE AND TIMES OF EDWARD LEPTON," by Carl Norman, is
one of the winning entries in the 1994 Science in Print award, sponsored
jointly by Britain's National Physical Laboratory and by the Institute
of Physics in London. Norman, who works at Imperial College, London, tells
the fanciful story of a single electron on its journey through the world.
Starting out as a yeoman outer electron in a silicon atom, Eddie (as the
electron is known) is liberated by the appearance of an impurity phosphorus
atom next door. Thereafter drawn on by electric potential, Eddie does journeyman
work through one circuit after another. He gets the ride of his life when
he is shot at high speed by the gun of a scanning electron microscope into
a specimen, where he frees thousands of brother electrons from surface
atoms. His energy spent, Edward lives out his days in semi-retirement attached
once again, as most terrestrial electrons must be, to an atom. (Physics
World, July 1994.)
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