April Meeting Features Fundamental Science and Societal Issues

The latest research results in particle, nuclear, plasma, and astrophysics will be featured at the 2008 APS April Meeting, to be held April 12-15, 2008 in St. Louis, MO. In addition, there will be a wide variety of sessions devoted to education, national security, energy research, and other social issues.

The meeting will be held in conjunction with an international conference sponsored by High Energy Density Physics (HEDP) and High Energy Density Laboratory Astrophysics (HEDLA). HEDP/HEDLA sessions begin on Friday, April 11 and cover such topics as supernovae, high-energy jets emerging from active galaxies and from stars, stellar cores, shock waves and turbulence in the universe, planetary interiors (including those of extra-large sized “super-earths”), heavy ion beams, laser-driven proton beams, wakefield accelerators, quark-gluon plasmas, and laboratory-produced high energy densities at facilities such as Livermore’s National Ignition Facility (scheduled for completion in March 2009) and Sandia’s Z Machine.

Detecting Dark Matter. Observational evidence to date indicates that most of the matter in the universe consists of non-baryonic particle dark matter, and the race is on to detect this mysterious matter both through direct and indirect means. Stanford University’s Jodi Cooley will review the evidence for weakly interacting massive particles (WIMPs) as candidates for dark matter, as well as current cryogenic techniques being used to detect dark matter directly, including the latest results from the Cryogenic Dark Matter Search in the Soudan Mine in Minnesota. Tom Shutt of Case University will describe new detectors based on liquified noble elements and next-generation experiments, such as the proposed DUSEL laboratory in South Dakota. Elliott Bloom (SLAC/Stanford) will review new experimental methods for the indirect detection of dark matter, including space-based satellites, ground-based gamma-ray telescopes, and neutrino telescopes. Leslie Rosenberg of the University of Washington will discuss the possible role of axions as dark matter. (Sessions B5.3 and M2)

Space Junk. The space age has brought many benefits, but also new problems, including the increasing amount of space debris: defunct satellites, discarded equipment, satellite fragments, and the remains of rocket stages. Even small pieces can damage or destroy operational satellites should they collide. There are currently 860 active satellites in orbit but more than half a million pieces of orbiting debris larger than one centimeter in size. David Wright of the Union of Concerned Scientists will discuss what we can do to stem the growth of space debris and reduce the threat to orbiting satellites. Caroline Reilly of RAND Corporation will demonstrate why space-based warfare is a bad idea within this context. And MIT’s Geoffrey Forden will focus on China’s January 2007 test of an anti-satellite weapon (ASAT) and the impact it and similar weapons could have on the amount of orbiting space debris. (Session X6)

Physicists Going Underground. Three sessions at this year’s meeting focus on the advantages of setting up experiments in the depths of Earth. John Wilkerson (Center for Experimental Nuclear Physics and Astrophysics, University of Washington) begins the first session by describing some of the things we can learn from underground experiments, including discovering the nature of neutrinos; detecting dark matter; determining the origins of the elements; explaining why the universe is mostly made of matter rather than antimatter; and much more. Other talks in the session identify the challenges of going underground, the technologies necessary to make the experiments work, and the sorts of data that experiments placed far underground might provide. (Sessions B13, D13, and E13)

Return of the Bubble Chamber. A venerable, but nearly forgotten, particle detector known as the bubble chamber is making a comeback as it breaks new ground in the search for dark matter. A small bubble chamber was at the heart of the Chicagoland Observatory for Underground Particle Physics (COUPP) that recently contradicted claims that dark matter had been detected in an Italian experiment. Andrew Sonnenschein (Fermilab) will describe the goals and capabilities of a new version of the COUPP experiment, which will be scaled up from the initial 2 kilogram chamber to a 60 kilogram version. By expanding the size of the experiment, the researchers increase their chances of finding a dark matter particle or, if they fail to find one, narrow down the range of the forms dark matter might take on. In either case, COUPP will offer insight into the elusive material that makes up the bulk of the matter in our universe. (E13.9)

APS Energy Efficiency Study. Nobel laureate Burton Richter (Stanford Linear Accelerator Center) will preview the APS Energy Efficiency Study that is currently underway. The study focuses on energy efficiency in buildings and transportation, which together consume 70% of the energy in the US. The study will identify immediate actions that could reduce energy use, the possibility of new energy-conserving devices emerging in the next five years, and revolutionary advances that could lead to long-term reductions in energy waste. The full report is due out in the early summer of this year. (G1.1)

Pioneer Anomaly Update. NASA recently revealed that the unexplained deviations in the paths of the Pioneer 10 and 11 spacecraft may occur with several other space probes as well. The cause, and even the existence, of the trajectory anomalies has long been the source of heated scientific debate. Slava Turyshev (Jet Propulsion Laboratory and California Institute of Technology) will update the status of the Pioneer Anomaly investigation now that more trajectory data is available. Turyshev will also address research into one possible cause of the anomalies–the tiny forces arising from the uneven emission of heat from the spacecraft (aka thermal recoil). (H7.1)

Exoplanets. More than 200 extrasolar planets have been discovered to date, mostly gas giants composed primarily of dense fluid hydrogen and helium at pressures millions of times greater than our atmosphere and at very high temperatures. Burkhard Militzer of UC Berkeley will discuss the challenges of characterizing such extreme systems, and some recent success with shock wave experiments. Diana Valencia of Harvard University will discuss ongoing investigations into the composition and structure of Super-Earths. LLNL’s Jon Eggert will talk about reproducing planetary cores in the laboratory. (11HE)

The Most Extreme Environments in the Universe. The universe looks very different when viewed in gamma rays, with remarkable features and large variations on all timescales. Generally, gamma rays are emitted from the most extreme environments, such as supermassive black hole systems and neutron stars. In the next few months, the Gamma-ray Large Area Space Telescope (GLAST) will be launched into orbit, where it will survey the sky from outside Earth’s atmosphere, which absorbs gamma rays. With its large leap in all key capabilities, the novel telescope will allow astrophysicists to observe this almost completely unexplored part of the electromagnetic spectrum over the entire sky every few hours. At the April Meeting, Steven Ritz (NASA GSFC and U. Maryland) will discuss the GLAST mission and its scheduled May 16 launch. (M5.2)

Highest Energy Gamma Rays Ever Detected. In the mountains just above Los Alamos, NM lies the Milagro Gamma-Ray Observatory, a large manmade pond filled with water and lined with photodetectors. Whenever gamma rays hit Earth’s atmosphere, they create showers of cosmic rays that hit the pool and produce a detectable blue light. As Earth rotates on its axis, the observatory continually turns and maps out high-energy sources in northern sky. Jordan Goodman (University of Maryland) will describe how the observatory recently identified a source of the highest-energy gamma rays ever seen. At the April Meeting, he will describe the Milagro results along with observations from the HESS telescope, a powerful gamma ray detector in the southern African country of Namibia. Together these observatories mapped and measured this significant source, which as yet has not been identified. (M5.3)

High Energy Physics. Dozens of sessions report on the latest news from accelerator labs for experiments happening right now. Prominent coverage is also being given to the testing of the Large Hadron Collider (LHC) and planning of the International Linear Collider (ILC)(sessions WS2, S2, R2, and others).

Gender Equity in Physics. In session R4, Nora Berrah of Western Michigan University will report on the Committee on the Status of Women in Physics (CSWP) May 2007 workshop titled “Gender Equity: Strengthening the Physics Enterprise in Universities and National Laboratories.” Other speakers in the session will discuss recommendations on how to make physics more attractive to women, and how to retain female physicists. In session D6, a panel discussion on international gender issues in physics focuses on policies of the European Union, and why there are so few female physicists in Latin America. Session W16 focuses on data from a survey of high school students in New Mexico.

Putting Gravity to the Test. Gravity is perhaps the most familiar force, but it’s also one of the weakest, which makes it difficult to test. Session T10 features a number of talks focusing on new ways to test the limits of gravity. Quentin Bailey (Embry-Riddle Aeronautical University) looks at the ways that measurements of the Earth-moon distance could be used to check gravity at long ranges, in view of recent proposals of modifications of the Standard Model of physics. Josh Long (Indiana University) describes tests at the other end of the size scale with flat, vibrating surfaces that check on gravity at a range of 50 millionths of a meter. Nicolas Yunes (Penn State) discusses the possibility that gravitational probes could be used to check string theory and quantum gravity, which is important because researchers have yet to find another feasible way to test the theories. (Session T10)

Mergers and Acquisitions. Physicists believe that mergers between two black holes could be a key source of gravitational waves strong enough to be detected by both ground-based (LIGO) and space-based (LISA) detectors, depending on their masses. Michael Coleman Miller of the University of Maryland and Scott Hughes of MIT will discuss how detection and characterization of such systems can yield unique information about stellar evolution, dynamics at many scales, and even help map the large structure of the universe. (Session T6)

Movies of the Universe in Three Billion Pixels. High atop Cerro Pachon, a remote mountain in Chile, in the next decade the large synoptic survey telescope (LSST) should come online and begin continuously imaging more of the universe than all the telescopes in history combined. The LSST will image the entire visible sky, taking fast, high-resolution snapshots of large patches in 15-second exposures and mapping out the entire sky every three days. LSST will do this continuously for ten years and will generate the largest astronomical data set ever assembled–about 30 terabytes a day, the equivalent of 100 million CDs over ten years. Ian Shipsey (Purdue) will discuss aspects of the telescope design and mission, including how it will examine the visible universe and address fundamental questions about the nature of dark matter, dark energy and the expansion of the universe. (W7.3)

International Year of Astronomy 2009. 2009 marks 400 years since Galileo turned his telescopes skyward, and the United Nations is celebrating with the World Year of Astronomy. Kala Perkins will share some of the new ideas for how to communicate astrophysics concepts to students and the public, and how to engage them in a cross-cultural event. (Session J16)