Number 716, January 19, 2005
by Phil Schewe and Ben Stein
The Most Distant Craft Landing in the Solar System
The Huygens probe, given long passage by the Cassini spacecraft into
the middle of Saturn's minor planetary system, has successfully parachuted
onto the surface of Titan, the only moon with a considerable atmosphere.
Pictures taken from miles above the surface during the descent and pictures
taken on the surface itself suggest the presence of boulders or ice
chunks and some kind of shoreline, perhaps of a hydrocarbon lake or
sea. The data gained so far include a sort of acoustic sampling of the
atmosphere during the descent and some color photographs. The Titan
probe is named for Christaan Huygens, who first spotted Titan and who
also was the first to provide the proper interpretation of Saturn’s
ring system. (http://www.esa.int/SPECIALS/Cassini-Huygens/)
The Sound of the Early Universe
New published surveys of distant galaxies are in accord with what you’d
expect from standard big bang cosmology. Precise measurements of the
cosmic microwave background provide in effect an image of the cosmos
just as the first atoms were forming about 400,000 years after the big
bang. The lumpiness of this background testifies to the shepherding
role of gravity in establishing primitive structures.
Statistical studies
of the distribution of the tiny surpluses or deficits across the microwave
sky suggest that at this point in the early universe (corresponding
to a redshift of 1000) colossal sound waves were propagating through
the primordial plasma. Evidence for these acoustic ripples moving through
early matter has now been seen, again in a statistical analysis, in
the distribution of galaxies occurring billions of years later.
Two
large astronomical collaborations, the Two Degree Field Galaxy Redshift
Survey (2dF) and the Sloan Digital Sky Survey (SDSS), both using automated
telescopes dedicated to measuring lots of galaxy redshifts, reported
at last week’s meeting of the American Astronomical Society in San Diego
that the present population of observed galaxies seems to have grown
steadily and consistently, through the agency of gravitational interactions,
out of the lumpy terrain of the earlier microwave background era. The
2dF catalog contains 221,000 galaxies, while SDSS’s catalog has almost
47,000. (Online papers, astro-ph/0501171, astro-ph/0501174; www.sdss.org,
www.aao.gov.au/2df/ )
Electron Clouds Can Freeze Into an "Orbital Glass"
Electron clouds can freeze into an "Orbital Glass" at low temperatures.
In the modern picture of quantum mechanics, electrons take the form
of "clouds" within the atoms and molecules in which they inhabit. The
clouds, which have various shapes such as spheres or dumbbells, represent
the general boundaries within which one may find an electron at any
one measurement in time. Typically, processes involving electron clouds
(more formally known as "orbitals") are blazingly fast. In the order
of a femtosecond (10^-15 s), for example, an electron orbital can make
transitions between degenerate states (those containing the same amount
of energy), transforming from a vertical dumbbell to a horizontal one
with respect to some axis.
Now, scientists have found evidence that
these and other orbital processes can slow down dramatically--to as
long as 0.1 seconds, a slowing by 14 orders of magnitude--for electrons
in low-temperature FeCr2S4, a spinel (class of mineral) with a relatively
simple crystalline structure. The researchers, who hail from the Center
for Electronic Correlations and Magnetism at the University of Augsburg
in Germany (Peter Lunkenheimer, Peter.Lunkenheimer@Physik.Uni-Augsburg.de)
and the Academy of Sciences of Moldova (a former Soviet republic), consider
these frozen electron orbitals in spinels to constitute a new class
of material which they have dubbed an orbital glass. By measuring the
response of the material to alternating-current electric fields in the
audio- to radio-frequency range, they found that processes involving
non-spherical orbitals dramatically slow down at low temperatures to
form a glass-like state, in a manner very similar to the arrest of molecular
motion that occurs when glass blowers perform their craft.
It's not
just the orbitals that slow down; the neighboring atomic nuclei that
surround the electrons also distort more slowly in response to the glacially
changing orbitals. In contrast to conventional glasses, a complete "freeze"
of the electron clouds does not occur at the lowest temperatures. Completely
frozen orbitals are prevented by quantum-mechanical tunneling: the clouds
keep themselves moving by making transitions between different low-energy
cloud configurations even without the energy they normally require.
(Fichtlet
al., Physical Review Letters, 21 January 2005
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