Physics Today Daily Edition
BBC: The Solomon Archipelago is a lightly populated chain of islands in the South Pacific Ocean. A survey of aerial and satellite images collected between 1947 and 2014 has revealed that five of the islands have been swallowed by the ocean through a combination of rising sea levels and erosion. The islands were vegetated reefs that were unpopulated and relatively small—the largest was only 12 acres (0.05 km2). However, larger, populated islands are also being damaged. One of them, Nuatambu, has lost half its inhabitable area and 11 houses since 2011. The study notes that although the islands have seen sea levels rise as much as 10 mm/year over the last two decades, extreme weather events and inappropriate development are also responsible for some of the damage.
Los Angeles Times: On 10 May, the team running NASA's Kepler space telescope announced that the spacecraft had identified another 1284 extrasolar planets, which brings the total number to 2325. The majority of the newly discovered planets are super-Earths or mini-Neptunes—both defined as planets roughly 1.25 to 10 times the mass of Earth. Nine of the planets orbit in the habitable zone of their parent star. The new planet haul resulted not from more data but from a new algorithm that determined how likely a signal detected by Kepler was a planet rather than a false positive. The algorithm was applied to the full dataset of 4302 candidate planets identified by the telescope, including the 984 previously confirmed exoplanets. The algorithm correctly identified the previously confirmed planets and pulled out the 1284 other signals that the team presented.
CNN: India is experiencing its worst drought in decades. Exceptionally high temperatures some 3–5 °C above average over the past year and two years of below-average rainfall have severely reduced groundwater levels. According to India's Central Water Commission, the country's major water reservoirs are 79% empty, and three-quarters of the country's basins have less water than the 10-year average. They are so depleted that the next monsoon season, which begins in June, will likely not be enough to fully replenish them, says Nitya Jacob of WaterAid India.
Mashable: On Friday, researchers from the Johns Hopkins University Applied Physics Laboratory released the first full-planet mapping of elevations on Mercury. The map was produced from data collected by the MESSENGER spacecraft, which finished its mission roughly one year ago. To produce the map, the scientists used more than one-third of the 300 000 images of Mercury taken by MESSENGER. From the images, the researchers calculated the average ground level and then measured the lowest and highest points on the planet, with the lowest point being 5.38 km below the average and the highest point 4.48 km above the average.
New York Times: Generally a postdoctoral position is a stepping stone to a full-time position in academia, but academic positions are hard to come by because of low turnover and high competition. So why do so many doctoral students in the sciences pursue postdocs? In 2010 and again in 2013, Henry Sauermann of Georgia Tech and colleagues surveyed PhD students studying biological and life sciences, physics, chemistry, engineering, or computer science at 39 universities across the US. They found that more than three-quarters of the biological and life sciences students believed at least one year of postdoctoral research was necessary to apply for a faculty position, and by 2013, 74% had taken a postdoc position. In the other fields, 42% thought a postdoc was necessary for a faculty position, and 46% took a postdoc by 2013. The most common reason cited by students for taking a postdoc was to increase their chances of getting a desired job.
Science: For several decades, unusual radar signals have been spotted that appear at dawn at an altitude of 150 km, grow stronger as they descend to 20 km, and then rise back to 150 km before disappearing at sunset. Because the signals get weaker during solar eclipses and stronger during solar flares, the Sun may be the source of the effect. But what causes it has not been clear. Now Meers Oppenheim and Yakov Dimant of Boston University suggest that extremely high-energy solar UV radiation could be ionizing gas molecules in a thin band of the upper atmosphere at an altitude of 150 km. Earth's magnetic field would then cause the freed electrons and the ionized molecules to rearrange themselves into areas of varying density, which can be detected by radar.