Yup, it’s time for those “top 10” lists for 2008. I don’t generally post other peoples’ lists here, but heck, this is one area where I know that I haven’t been paying close enough attention to know what’s important. So here is an edited version of the Physics Findings for 2008 from Physics News. Phil Schewe does such a great job with these, they’re a delight to read. You can read the whole thing at Physics News Update (and subscribe to their e-newsletter).
TOP TEN PHYSICS STORIES OF THE YEAR
The following list was chosen by editors and science
writers at the American Institute of Physics and the American Physical
Society. It winnows a wealth of discoveries into the following ten
topic areas, which are listed in no particular order.
What’s new-discovery of an unusual class of materials made from iron
and arsenic. Superconductors don’t lose any energy when electricity
runs through them, providing they’re chilled to very low temperatures.
Superconductors are used in specialty applications where high
electrical currents are needed, such as in MRI scanners at hospitals or
in the magnets used to steer particles at atom smashers. …
The new iron-arsenic materials are the first relatively
high-temperature materials that remain superconducting above a
temperature of 50 K that don’t contain copper; the copper materials are
brittle. Researchers hope that the iron-arsenic version might lead to
the more practical manufacture of superconducting wire. Furthermore,
having a new class of materials to study should help theorists
understand how high-temperature superconductors work in the first
Background: A summary of work in this area can be found at Physics
Today, May 2008; APS survey of topic.
LARGE HADRON COLLIDER
What’s new—the LHC, the world’s largest scientific instrument,
started operations in September. At this huge particle accelerator,
located underground near Geneva, Switzerland, two beams of protons, each
traveling at unprecedented speeds will be smashed together. The goal is
to create exotic new particles that can’t be observed in any other way
except in the tiny fireball created by such violent collisions. ….
Problems with some of the apparatus forced a premature shutdown
… General operations should resume in summer 2009.
Background: a summary of the magnet malfunction which brought testing to
a halt in September and a timetable for operations are available here.
What’s new-planets orbiting distant stars have been imaged directly, and a host of interesting results have come back from spacecraft hovering near the planets in our own solar system. Extrasolar planets, planets orbiting far-away stars, had been detected indirectly by watching what happens to the light coming from the star. But now the glare of the star has been blocked sufficiently that the extrasolar planet itself could be imaged. The Gemini, Keck, and Hubble telescopes provided pictures. Background summary here.
In our own solar system, at Mercury, the Messenger spacecraft made first-ever maps of large portions of the surface. At Saturn, the Cassini craft found geysers near the south end of the moon Enceladus. At Mars, measurements made by several craft strengthened evidence in favor of sub-surface glaciers outside the polar regions. Meanwhile, the Venus Express craft recorded pictures at several wavelengths, facilitating, among other things, a better knowledge of clouds on Venus.
What’s new-unusual combinations of quarks were observed for the first time. Physicists believe that an atom consists of one or more electrons orbiting a central nucleus. The nucleus, in turn, is made of protons and neutrons, and these particles are made of something still more elementary-quarks held together by gluons. … One discovery consists of the sighting of nuclear particles containing rare “bottom” quarks. Background here.
[See the full article at Physics News Update for more on these experiments -geekgirl]
FARTHEST SEEABLE THING
What’s new-seeing a flash of light from 7 billion light years away.
One of the brightest of all celestial objects is gamma-ray bursters,
objects that emit immense amounts of gamma radiation, the highest-energy
form of light. The brightest-ever gamma ray burster was observed by the
Swift satellite. Since looking out into space is equivalent
to looking back in time, this flash would have been coming from a moment
when the universe was only half its present age. Publication in Nature.
What’s new-first ever accumulation of molecules in large numbers and
at a temperature near absolute zero. Using lasers to slow a gas of
particles down to near stillness is by now a standard method for
measuring the subtle properties of atoms. Steven Chu, nominated to be
the Secretary of Energy, won a Nobel Prize for pioneering this subject.
Cooling molecules in this same way is difficult since molecules, made of
two or more atoms, have complicated internal motions. But this year
several labs succeeded in first cooling atoms and then, at a temperature
close to absolute zero, getting them to combine into molecules. …
Background at http://www.aip.org/pnu/2008/split/875-1.html; figure
http://www.aip.org/png/2008/306.htm; PRL text and overview at
What’s new-getting little imperfections in diamond to tell us about
how atoms behave like tiny magnets. Diamond is made of a cross-linking of carbon atoms. If one
carbon atom is missing from this network, the empty hole, in combination
with a stray nitrogen atom, acts as a sort of strange molecule in the
middle of all those carbon atoms. This “molecule” can light up like a
little LED when you shine laser light in. This in turn, can be used to
measure extremely weak magnetism. Possible applications include data
storage for computers or high-sensitivity detectors. … See news summary at
What’s new-experiments settle one mystery and uncover others. Cosmic
rays are super-high-energy particles whizzing through the cosmos. When
they smash into our atmosphere the rays turn out mostly to be ordinary
particles, such as protons or electrons, but with energies thousands or
millions of times higher than particles speeded up at accelerators on
Earth. [See full Physics News Update article for new results — there are many! -geekgirl]
LIGHT PASSES THROUGH OPAQUE MATTER
What’s new—getting light to behave in a new way. When light strikes
an opaque material like milk most of the radiation is scattered; little
of it passes through the sample. But in an experiment at the University
of Twente in the Netherlands, much more of the light can be made to
traverse the scattering material if beforehand the wavefront of the
incoming light is shaped by special filters. Background summary.
MACROSCOPIC FEEDBACK COOLING
What’s new—Scientists at the AURIGA lab in Padova, Italy have cooled
a one-ton aluminum bar to a temperature below 1 milli-kelvin using
special electrical circuits. The bar is part of a detector designed to
measure passing gravity waves from space. Using sensitive magnetic
sensors and feedback coils, the ringing of the bar (which is essentially
a large tuning fork) at one characteristic frequency was cooled from an
equivalent temperature of 4 K (the temperature of the bath of liquid
helium in which the bar sits) to a temperature of about 0.17 mK. Lower
temperatures than this have been achieved with this feedback cooling
technique but only with much smaller masses. Background: essay and PRL
article at http://physics.aps.org/articles/v1/3
Phillip F. Schewe