APS News

Westward Ho: April Meeting Descends on Denver


More than 1000 physicists will be on hand for the 2004 APS April meeting, to be held May 1-4 in Denver, Colorado. The April meeting traditionally covers a wide range of physics subfields, including astrophysics, nuclear and particle physics, the physics of beams, plasma physics, computational physics, gravitation, hadronic physics and few-body systems. There will also be numerous sessions on physics education and history. A special public lecture will be offered Saturday evening, May 1, on how the sun shines.

The Case of the Missing Neutrinos. In the mid-19th century, Charles Darwin and Lord Kelvin found themselves on opposite sides of a controversy regarding the age of the sun and the origin of solar energy. It would be over a century before physics had advanced to the point where scientists could postulate the existence of solar neutrinos, and detectors could be built to measure these elusive particles, which scientists believe are produced when the sun burns hydrogen nuclei to supply the sun's radiant energy. But far fewer neutrinos were observed than were predicted by theoretical models. The mystery of the missing neutrinos would not be solved for another three decades, when scientists discovered a dramatic solution in January 2001. The history of the neutrino problem, its solution, and subsequent research will be the topic not only of a special public lecture on Saturday evening by John Bahcall of the Institute for Advanced Study in Princeton, NJ, but will also be discussed by Fermilab's Boris Kayser, who will describe how neutrinos can morph from one "flavor" to another. In addition, a special Town Meeting entitled "Our Neutrino Future" on Sunday evening at 8 pm will feature talks by Stuart Freedman, Michael Turner and others, and provide ample time for audience partici- pation. There is also an invited session on neutrinos on Sunday afternoon at 2:30 pm. [Public lecture and sessions H1, L4 and N1]

Exploring the Solar Corona. Despite being studied by physicists for more than a century, the dynamic microstructure of the sun's corona (usually visible during a solar eclipse) is only beginning to be revealed, according to Eugene Parker of the University of Chicago, who gave a Monday morning plenary lecture on the topic. The quest to glean more information about this mysterious gas is hampered by the limited resolution of existing telescopes. But now there is the proposed Advanced Technology Solar Telescope, a 4m ground-based instrument with adaptive optics capable of providing resolution down to 50 km [the corona has internal scales of 100 km or less], which will be combined with rapid cadence, high-dispersion spectroscopy to follow the action of the sun's corona. [Session Q1]

Good Vibrations. Sand, pharmaceuticals, cereal, cosmetics and asteroids are all examples of granular media, which are involved in many physical processes, although less understood than fluids and solids, according to Harry Swinney, who will give a plenary lecture on the spontaneous emergence of order in vibrated sand on Saturday morning. He conducts experiments using vertically oscillating granular layers, which have revealed a variety of spatial patterns emerging spontaneously as a result of the combination of container acceleration amplitude and frequency: stripes, squares, spirals, and hexagons, to name a few. These results correspond with computer simulations of the molecular dynamics of granular media. [Session A1]

A New Look at Black Holes. Recent discoveries have caused our assumptions about supermassive black holes to undergo a dramatic paradigm shift, according to speakers at a Saturday afternoon session detailing the discovery of these so-called "dark stars". They are notoriously difficult to detect because they emit no light of their own and can only be seen by their influence on nearby stars and gas. Speculations about the existence of black holes date back more than 200 years, but a theory did not appear until 1939. The theory gained wide acceptance with the discovery of quasars in 1963, and Cygnus X-1, the first bona fide black hole, was identified in 1972. Now, scientists believe that these objects may have been critical to the formation of structure in the early universe, spawning bursts of star formation and planets, according to Fulvio Melia of the University of Arizona, who will describe a possible black hole lurking at the center of the Milky Way. The University of Maryland's Cole Miller will speculate on possible new classes of black holes, such as solitary black holes and those with intermediate mass. He will also discuss the possibility of primordial black holes formed in the very early universe, which could be the primary components of the mysterious dark matter. Jeffrey McClintock (Harvard-Smithsonian Center for Astrophysics) will describe black hole x-ray binaries, and Omar Blaes (UC-Santa Barbara) will present the case for supermassive black holes being responsible for the prodigious power output of active galactic nuclei and quasars. [Session D3]

String Theory Squares Off Against Newton. Gravitation may be the oldest known interaction in physics, but it is still inspiring small-scale experiments to address such important open issues as why the force of gravity is so much weaker than other interactions, and why the cosmological constant is so small compared to the predictions of quantum mechanics. At a Saturday morning plenary session, Eric Adelberger of the University of Washington will discuss some of the techniques now being employed to test Newton's inverse square law, which some modern string theorists believe may break down at distances less than 1 mm, or even at solar system scales. These techniques include ultracold neutron technology, ultra-precise laser ranging of the moon, and extremely sensitive mechanical experiments with torsion oscillators and microcantilevers. [Session A1]

Dirty Bombs. So-called "dirty bombs"-technically known as radiological dispersion devices (RDDs)- are designed to spread intensely radioactive material with the intent to kill, sicken, or cause economic damage. The risks associated with RDDs have been somewhat overestimated by the government, even as they have been underestimated by physicists. As the tragic accident in Brazil demonstrated [see "The Back Page," APS News, March 2004], people in contaminated regions will inhale or digest dusty or liquid radioactive material in sufficient quantities to cause acute radiation sickness, and sometimes death. Speakers at a Monday morning session will provide a general overview of the nature and use of RDDs, the readily available sources of sufficient quantities of radioactive material, and the need to improve the security surrounding those sources to keep them from falling into the hands of terrorist groups. [Session R8]

Radiation Detection. Countries around the world are deploying radiation detection instrumentation to combat the illegal shipment of radioactive material crossing international borders by land, rail, air and sea. Speakers at a Sunday afternoon session will discuss the role of the physics community and radiation detection in preserving homeland security, as well as a new concept for an active neutron interrogation system that can detect small targets of contraband material even when shielded in thick Intermodal cargo containers.

Also featured in the session will be Yale University's Cornelius Beausang, who will describe his work educating and training first responders in radiation (see APS News, January 2004). [Session L2]

Solar Flares. Solar flares are known to release explosive energy in unconfined, magnetized plasma, and are generally believed to derive their energy from the sun's coronal magnetic field, but scientists are still trying to discover the release mechanism and how the energy is distributed among heating, particle acceleration, and mass motions. NASA's RHESSI mission is designed to study the acceleration and evolution of electrons and ions in solar flares by observing the x-ray and gamma-ray emissions these particles produce. Since its launch in February 2002, RHESSI has observed over 12,000 solar flares, according to NASA's Gordon Holman, who will describe how his team uses the RHESSI spectra to deduce physical properties of accelerated electrons and hot plasmas in flares. Other speakers will discuss high energy flare emissions and the study of solar flares in laboratory plasmas. [Session R3]

All the President's Men. Several former presidential science advisors will speak at a special Tuesday morning session devoted to tracing the history of that position from Franklin Roosevelt to the present. D. Allan Bromley (Yale University), and Jack Gibbons will describe their experiences and the issues that confronted them during their tenure, while Gregg Herken of the University of California will provide an historical perspective. Joel Primack of UC-Santa Cruz will round out the session with a talk on the AAAS Congressional Science Fellowship program and other efforts to engage scientists in informing the public and Congress about science. [Session V8]

Correcting Misconceptions. Among the biggest barriers to physics education is combating student misconceptions and faulty reasoning about basic physics tenets. Speakers at a Saturday morning session will explore such common misconceptions about the first and second laws of thermodynamics and electrical circuits, among other topics, and suggest approaches to combat those misconceptions. For example, students tend to have difficulty lighting a flashlight bulb with a 1.5 volt battery and a single wire, according to researchers at Kansas State University, apparently because they do not understand the bulb's internal wiring. The KSU scientists have designed experiments to alter that false impression. Similarly, David Meltzer of Iowa State University has found that students' difficulties with thermodynamics stem in part from the fact that heat, work and internal energy all share the same units. [Session B14]

Special Events

Saturday, May 1
Welcome Reception
5:30 am - 7:00 pm
Public Lecture
"How Does the Sun Shine?"
John Bahcall, Institute for Advanced Study
7:00 pm - 9:00 pm

Sunday, May 2
Meet the Editors
3:00 pm - 5:00 pm
Prize and Awards Presentations
5:30 pm
COM/CSWP/FIP Reception
7:00 pm - 9:00 pm
Neutrino Town Meeting
8:00 pm - 10:00 pm

Monday, May 3
Student Reception
5:30 pm - 6:30 pm
6:00 pm - 8:00 pm

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Editor: Alan Chodos
Associate Editor: Jennifer Ouellette