Metallic Hydrogen, Gravitational Waves, Killer Asteroids, Photosynthesis Seen From Space, the Atypical History of Climate Change Science, and More

Free content from this month's issue of Physics Today now available online


Newswise — WASHINGTON D.C., September 1, 2015 -- The following articles are freely available online from Physics Today (www.physicstoday.org), the world's most influential and closely followed magazine devoted to physics and the physical science community.You are invited to read, share, blog about, link to, or otherwise enjoy:

1) LIQUID DEUTERIUM NEEDS EXTREME PRESSURE TO BECOME A METALEighty years ago, Eugene Wigner and Hillard Huntington predicted that solid hydrogen could be compressed into an atomic metal, given enough pressure. In this Search and Discovery story, Physics Today's Sung Chang reports on efforts to pressurize liquid deuterium, a hydrogen isotope, into a metal phase—a daunting task that employed Sandia National Laboratories' Z machine, the most powerful laboratory radiation source in the world."Now Marcus Knudson and Mike Desjarlais of Sandia National Laboratories and their colleagues at Sandia and the University of Rostock in Germany think they have sighted the elusive transition. The group used Sandia's Z machine to dynamically compress liquid deuterium to pressures greater than 300 GPa at temperatures between 1000 K and 2000 K. Their measurements indicate that the liquid abruptly goes from being an insulator to being a metal at about 300 GPa."MORE: http://bit.ly/1L1a8wJ

2) GRAVITATIONAL WAVES, INCOMING!Although a strong prediction of Einstein's theory of relativity, gravitational waves — which manifest as the stretching and scrunching of spacetime — haven't ever been directly observed. With the activation of second-generation gravitational-wave interferometers — two in the U.S. in the coming months and various others in Italy, Japan and India over the next few years — this may soon change, with significant implications for our understanding of cosmic events. Physics Today's Toni Feder reports."Reconstructing sources of gravitational waves would allow for tests of Einstein's theory of general relativity and open a window for studying neutron stars and other very compact objects... The second-generation detectors will be 10 times as sensitive in amplitude as the first-generation LIGO and VIRGO. That corresponds to a thousandfold increase in cosmic volume that can be probed; the predicted number of potentially observable coalescing binary neutron stars jumps from 1 in a few decades to 10 a year, give or take an order of magnitude."MORE: http://bit.ly/1O5YGmP

3) FINDING ASTEROIDS AMID BUDGETARY CONSTRAINTSThe asteroid that wiped out the dinosaurs was 10 km across; something that big hitting Earth happens only once in tens of millions of years. Astronomers have located more than 90% of estimated asteroids and near-Earth objects (NEOs) larger than 1 km. But fewer than 1% of an estimated 1 million NEOs larger than 20 meters—the size of the Chelyabinsk meteor that exploded over Russia two years ago, damaging thousands of buildings and injuring nearly 1,500 people—have been identified. In this Issues and Events article, David Kramer of Physics Today reports on the efforts of NASA and ESA to identify the potential threats within our solar system and develop methods to prevent them from colliding with Earth."It's no secret that NASA won't be able to meet a 2005 congressional directive to find 90% of NEOs larger than 140m by 2020. The problem, says Green, is that lawmakers have failed to back up their mandate with the necessary appropriations. For years NASA's NEO operations struggled by on budgets in the $4 million to $5 million range. In recent years, though, the budget has risen steadily by $10 million a year, to $40 million for FY 2016. As a result, the number of newly discovered NEOs has gone from 893 in FY 2011 to 1472 last year." MORE: http://bit.ly/1hRzLJF

4) MAXWELL'S DEMON AND SZILARD'S ENGINE 'BROUGHT TO LIFE'In this feature, University of Erlangen-Nuremberg theoretical physics professor Eric Lutz and École Normale Supérieure research director Sergio Ciliberto discuss recent technological progress that has brought thermodynamic thought experiments — Maxwell's Demon, Szilard's engine, and Landauer's erasure principle — into the lab, and their consequent effect on physicist's understanding of the second law of thermodynamics."Some 150 years after its inception, Maxwell's demon is still vibrant. Together with Landauer's principle, it continues to influence modern research. Having only recently become an experimental science, the thermodynamics of information has potential to deliver new insights in physics, chemistry, and biology. Conceivably, it may even be extended to the realm of quantum mechanics, where it could pave the way for a full-fledged thermodynamics of quantum information."MORE: http://bit.ly/1NKQlI1

5) THE POST-PHOTOSYNTHETIC GLOW THAT PLANTS CAN'T HIDE Plants are highly effective at converting captured sunlight into energy, but they don't utilize it all, offloading the excess energy as heat and, to a small extent, fluorescence. In this Quick Study, Massachusetts Institute of Technology assistant professor Gabriela Schlau-Cohen and Carnegie Institution for Science staff member Joe Berry discuss solar-induced fluorescence and how measurements of it, both in the lab and from space, are helping determine the rate of photosynthesis over vast agricultural regions."As with photovoltaic solar cells, the photosynthetic light-harvesting machinery is not perfectly efficient. In the case of photosynthetic systems, one of these inefficiencies — a small amount of fluorescent reemission of absorbed photons — is offering scientists new ways to understand photosynthesis, the power source of the biosphere."MORE: http://bit.ly/1fTrGCi

6) GLOBAL WARMING: AN ATYPICAL SCIENTIFIC HISTORYIn this feature, Spencer Weart, historian emeritus at the American Institute of Physics's Center for History of Physics discusses the history of the scientific community's understanding of global warming’s impacts, from Svante Arrhenius's 1896 estimate of the effect of carbon dioxide levels on global temperatures through the early alarms of the 1950s and 1960s to today's dire forecasts."We need to convince the public of the threats we face; yet how can we convince them if we don't explain how scientists came to know what they know? The history of any scientific development can address general questions of how scientists do their work and reach their conclusions. But the history of climate change impact studies turns out to be a peculiar kind of history, not at all the sort of story that historians of the physical sciences are used to telling."MORE: http://bit.ly/1hvgixK

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