Physics Today Daily Edition
The Laser Interferometer Gravitational-Wave Observatory contributes a physics sound bite for the ages
Los Angeles Times: Despite the melting of glaciers and ice sheets over the past decade and a half, sea levels have not risen as much as expected. According to scientists at NASA’s Jet Propulsion Laboratory, the difference is due to the amount of moisture being absorbed by the continents. Using the Gravity Recovery and Climate Experiment (GRACE), which comprises two satellites nicknamed Tom and Jerry, John Reager and coworkers studied how the distribution of water causes the force of Earth’s gravity to wax and wane at various points on the planet’s surface. Drought in California, for instance, causes a decrease in gravity; a big flood elsewhere will increase the force of gravity. Because of an increase in rain and snowfall over land during the period 2002–2014, the continents have soaked up more water and thus have caused the rate of sea-level rise to slow. However, land can only absorb so much water. Humans will still need to cut their greenhouse gas emissions to slow glacial melt and concomitant sea-level rise.
Ars Technica: China's Daya Bay neutrino detector analyzes a beam of electron antineutrinos produced by nearby nuclear reactors. The detector counts how many of the particles have experienced flavor oscillation and become either muon or tau antineutrinos. After nearly eight months of operation, the facility has detected more than 300 000 neutrinos. However, the number of flavor oscillations has not matched what scientists predicted, and this is not the first detector to note the discrepancy. But none of the experiments have had a strong enough—5 sigma—signal to conclude outright that the discrepancy is real. One theory suggests that there are flavor-neutral, or "sterile," neutrinos. Perhaps on a related note, Daya Bay also saw an unexpectedly large, though also not quite 5 sigma, signal in the energy level of the neutrinos. If that signal proves to be real, it could mean that nuclear reactors aren't producing as many neutrinos as expected.
Guardian: Construction of the Five Hundred Meter Aperture Spherical Telescope (FAST) started five years ago in the Chinese province of Guizhou and is expected to be completed by September. The telescope's diameter is 200 m larger than that of the Arecibo telescope, which turned 50 in 2013. To ensure minimal signal interference for the 1.2 billion yuan ($184 million) project, the Chinese government has decided to relocate more than 9000 residents from an area within a 5 km radius around the telescope, and it is providing each resident with 12 000 yuan ($1800) in compensation.