Physics Today’s online staff summarize the most important and interesting news about science from the world's top media outlets.
There are 19 posts for the selected month (February 2016).
Nature: From 1750 to 1850, nearly 200 000 km2 of forest were cut down in Europe. In the 160 years since, forests have reclaimed an area more than twice as large and now cover 10% more land than they did in 1750. However, the amount of carbon stored in those forests is 3.1 billion tons lower than what was stored in 1750. According to Kim Naudts of the Max Planck Institute for Meteorology in Hamburg, Germany, and her colleagues, it appears that the difference is likely due to the shift from deciduous trees to conifers in an area covering 633 000 km2. Naudt's team says that the shift was caused by timber harvesting and replanting, which favors conifers because of their fast rate of growth.
Ars Technica: For the past five years, NASA has stated that one of its primary goals is crewed missions to Mars. On Wednesday, a House space subcommittee heard comments from three outside experts about NASA's plans. John Sommerer, who was the chair of a National Research Council panel that reviewed NASA's human spaceflight programs in a 2014 report, indicated that to meet the agency's goals would require roughly $500 billion over the next 20 to 40 years. In contrast, NASA director Charles Bolden and other agency officials have said that they are comfortable with the agency's current budget for human exploration, plus increases for inflation, which only totals to $180 billion over 20 years. However, that amount would not allow for continued support of the International Space Station. Tom Young, former director of NASA's Goddard Space Flight Center, agreed with Sommerer that NASA does not have a clearly defined plan for reaching Mars. Young and Sommerer said that NASA would need to either receive a significant budget boost or narrow its focus and shift funds away from other programs.
New Scientist: In 2008, Eleftherios Goulielmakis of the Max Planck Institute of Quantum Optics in Garching, Germany, and his colleagues created the shortest ever pulses of light, with a duration of just 80 attoseconds (10−18 s). However, they used extreme UV (EUV) light, which is so energetic that it can strip electrons away from an atom entirely, rendering it useless for measuring the responses of electrons to outside stimuli. Now, Goulielmakis's team has created the shortest ever pulses of visible light, with a duration of 380 attoseconds. Visible light does not strip electrons from around an atom; rather, it excites them just enough that they emit their own photons. The attosecond flashes were created by merging light pulses that were the same wavelength but slightly out of phase. Their interference cancels out all but small parts of the pulses. The 380-attosecond pulse was short enough to act like a camera flash, which allowed the researchers to catch the emission of UV photons from electrons orbiting krypton atoms. That emission took place just 115 attoseconds after the electrons were excited. It is the first time that researchers have been able to both excite an electron to emit a photon and directly measure the time it takes.
Guardian: Forty years ago a theory was proposed that the wrinkles on the outer layer, or cortex, of the human brain formed during fetal development because of differential growth rates and the constraints of the size and shape of the skull. A team led by Tuomos Tallinen of the University of Jyväskylä, Finland, has tested the theory for the first time. The researchers used a 3D printed model of a 22-week-old fetal brain before any wrinkling had occurred. The model was made of a soft polymer core coated with an absorbent elastomer gel that represented the cortex. When placed in a solvent, the elastomer swelled and buckled because of its attachment to the core, which restrains the expansion. The result was short furrows that elongated and then formed into the characteristic junctions and bends seen in real brains. When Tallinen and his team members modelled the process mathematically and compared the model with images of different stages of fetal brain development, they saw a distinct similarity. Although the process doesn't match the volume or surface-area increases seen in real brains and doesn't account for the external limitations imposed by the skull, it does provide potential insight into the mechanics of brain growth.
BBC: The supermassive black hole at the center of galaxy Pictor A produces two jets of extremely bright x rays that extend three times the width of the Milky Way. The jets were originally revealed by the Chandra X-Ray Observatory, but what made them so bright could not be determined because the pictures of the galaxy were not of high-enough resolution. Now Martin Hardcastle of the University of Hertfordshire, UK, and his colleagues have combined 15 years of x-ray data from Chandra with radio images created by the Australia Telescope Compact Array. The resulting images, whose resolution is five or six times better than that of the best previous images of Pictor A, reveal new details and allow a better examination of the physics at play in the jets. Based on the images, Hardcastle's team believes that the light being emitted from the jets is caused by electrons that are being accelerated in very tight circles similar to the way they are in synchrotrons on Earth. However, what is causing the electrons to be reaccelerated along the full length of the jets isn't clear.
BBC: Volcanoes are always leaking gas, but a specific change in the composition of the gas could provide an early warning sign that an eruption is imminent. David Pyle of Oxford University and his colleagues examined the dormant Campi Flegrei volcano near Naples, Italy, which last erupted in 1538. They were looking for bubbles of gas that were trapped in molten rock shortly before the eruption. By comparing the composition of the gas in those bubbles with that of gases trapped at other times, the researchers reconstructed the magma's evolution leading up to the eruption. The models revealed that the composition of the gas changed significantly in a relatively short period of time before the eruption. Finding similar evidence at other volcanoes will be necessary to support the theory. If fluctuating gas compositions are a common pattern, monitoring volcanic gas could prove useful for identifying potential eruptions ahead of time.
New Scientist: Coating water droplets with hydrophobic powder creates opaque, liquid marbles. Now a team led by Xiaoguang Li of Tongji University in Shanghai, China, has extended that technique by replacing the hydrophobic powder with 20-nm silica particles. Because of the thinness of the silica layer, the water droplets remain transparent. And unexpectedly, the silica particles have the ability to jam together, which allows the researchers to mold the water droplets into almost any shape. They have demonstrated how the new material can be sliced like Play-Doh, formed into words, and even used as a convex lens. Further, the researchers discovered that chemicals added to the water diffused slower than normal, suggesting that the droplets might server as miniature test tubes.