Science > Physics > PHYSICS NEWS UPDATE Number 749 October 13, 2005 by Phillip F.Schewe and Ben Stein
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PHYSICS NEWS UPDATE Number 749 October 13, 2005 by Phillip F.Schewe and Ben Stein |
PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 749 October 13, 2005 by Phillip F. Schewe and Ben Stein
THE CAREER OF CHARLES TOWNES, filled with outstanding
accomplishments in laser science and radio astronomy, was celebrated
at a meeting held last week at the University of California at
Berkeley. The gathering, called "Amazing Light: Visions of
Discovery," marked Townes's 90th birthday and was the occasion for a
series of talks by distinguished speakers (18 Nobel laureates were
present) on forefront topics in fundamental physics and the
technological innovations that arise from basic research (meeting
website at http://www.foundationalquestions.net/townes/). The
following items represent some of the interesting results and quips
from the meeting.
To start with, this year's physics Nobel Prize (
http://www.aip.org/pnu/2005/split/748-1.html), announced only two
days before the start of the meeting, could not have been better
aligned with Townes's pioneering laser work and with recurrent
themes expressed in several talks, namely the ubiquity, versatility,
and quantum nature of laser light. Two of the 2005 laureates were
actually in attendance: Roy Glauber (Harvard) and Theodor Haensch
(Max Planck Institute, Munich).
Haensch sounded an important precept by quoting Townes' former
colleague, Arthur Schawlow: "Never measure anything but frequency,"
meaning that signal frequency can essentially be measured with
higher precision than any other physical quantity. For example, the
frequency of light cast off by the hydrogen atom in relaxing from
its first excited state to its ground state is known with an
uncertainty of better than one part in 10^14. Haensch said that
this precision will improve further in coming years, with a
corresponding improvement in things like spectroscopy and readouts
from the Global Positioning System, an excellent example of turning
a distance measurement into a frequency measurement.
Who will be the next Charles Townes? We don't know, but to
encourage and recognize newcomers, a young scholars competition was
held at the meeting. In the technological innovation category, the
first place award went to Jun Ye, a JILA/NIST colleague of another
of this year's Nobelists, John Hall. Ye also spoke about the superb
optical precision made possible by the advent of femtosecond laser
pulses. He reported on JILA/NIST's efforts to produce a highly
precise, stable laser output and its applications to various
scientific endeavors. Combining ultracold atoms, stable lasers, and
coherent control techniques, the JILA team is making advances in
several areas including the work on an optical atomic clock, where
measurement precision has reached a level of about 7 x10^-15. The
precise measurement is made possible by a primary frequency
standard, NIST's fountain cesium atomic clock, which is accurate to
7 parts in 10^15.
What will be the next great invention on the order of the laser? We
don't know, but clever new ideas keep coming along. The
second-place award in the technological innovation competition went
to Marin Soljacic (MIT) for his concept of wireless, non-radiative
energy transmission. Just as in the quantum case in which the
Schrodinger equation allows for a wave trapped in a box to tunnel
out, so Maxwell's equations allow for the leakage of electromagnetic
energy from an electromagnetic resonance object. If another such
object were placed not far from the first one, and the resonant
frequencies of both were the same, then the energy could be
transferred between them with very little energy lost to other
objects in the nearby environmental that do not share the same
resonant frequency. The transmitted energy, although
electromagnetic in nature, would not be referred to as "radiation"
since it is bound to the resonant objects. It is rather an example
of "near-field" physics. Soljacic avoids words like "antenna,"
since the process does not involve broadcasts of energy in the usual
sense. In contrast, the vast majority of energy radiated by
antennas is typically wasted and lost into free space, while only a
small portion is picked up by the eventual receivers. Instead,
Soljacic uses terms like "source" and "drain" in analogy with
transistors to describe the movement of energy. An exemplary setup
might consist of a transmitter in a ceiling and devices in that room
(e.g robots, or computers) being powered wirelessly by this energy.
(For a list of other young scholar winners, see
http://www.foundationalquestions.net/townes/pressroom.asp)
Steven Chu (LBL), speaking of measurements made in the biological
physics realm, said that Isaac Newton's worldview applied largely to
a frictionless world. If Newton had been the size of a bacterium,
Chu suggested, the famous force laws would we very different: (1) an
object in motion will very shortly come to a rest; (2) an object
nominally at rest will jiggle around a lot; and (3) the force an
object feels is proportional to surface area and velocity.
Wolfgang Ketterle (MIT), speaking of trapped vapors at nano-kelvin
temperatures, said that unlike the early history of the study of
coherent light in the 1960s, the current study of coherent matter
(atoms held in static BEC clouds or released as "atom laser" beams)
was not a "solution in search of a problem." BEC-based matter-wave
sensors, he said, would most likely find useful applications in
geology (as gravity sensors) and in navigation (rotation sensors).
Furthermore, molecular BECs made from paired fermi atoms and
partaking of strong tunable interactions, would likely serve as an
arena for studying two of the most important issues in all of
condensed matter physics, high-temperature superconductivity and the
quantum properties of spin liquids (ensembles of magnetic
particles).
Anthony Leggett (Univ Illinois) addressed one of the meeting's
principal themes, grappling with quantum reality. We don't really
know the past, Leggett asserted. Our knowledge of macroscopic
matter is "thermodynamic" (meaning that what we know pertains to
averages over large numbers of particles) and not microscopic.
Quantum uncertainty and chaotic dynamics are also often invoked in
denying the realization of longterm predictability. Therefore we
could never, as Pierre-Simon Laplace held, employ deterministic
equations to calculate the subsequent extended history of the
universe. (The issues of causality, the knowability of the past,
and of free will came up in several talks at the meeting.)
Where will science go next? We don't know, but Peter Galison
(Harvard) spoke of the intellectual climate in which past
technological and scientific discoveries have been made. He sees
the historical and philosophical view of physics over the past
century or so as oscillating between two poles---the positivist view
(typified by Ernst Mach), according to which only experimental
observations are considered satisfactory and reliable, and the
anti-positivist view (typified by Thomas Kuhn), which is much more
willing to credit theoretical ideas in advancing and altering the
general consensus. Meanwhile, Freeman Dyson (Institute for Advanced
Study) carved up physics history in a different way. Borrowing
Isaiah Berlin's famous dichotomy between "foxes" (which know many
things) and "hedgehogs" (which know one big thing), Dyson said that
the great hedgehogs and foxes of physics seemed to come in waves.
Einstein and Newton, said Dyson, were hedgehogs; they're the deep
thinkers. Enrico Fermi, and the guest of honor, Charles Townes,
were foxes; with agility they moved from topic to topic. Dyson's
nominal topic was the future of science. He claimed no method for
predicting coming achievements. "The best way to learn about the
future of science," he concluded in his elegantly gruff manner, "is
to stay alive as long as you can and see what happens."
***********
PHYSICS NEWS UPDATE is a digest of physics news items arising
from physics meetings, physics journals, newspapers and
magazines, and other news sources. It is provided free of charge
as a way of broadly disseminating information about physics and
physicists. For that reason, you are free to post it, if you like,
where others can read it, providing only that you credit AIP.
Physics News Update appears approximately once a week.
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