Physics Today Daily Edition
Nature: Online preprint servers, such as arXiv, allow researchers to publicly share their papers prior to peer review. The sites are growing in popularity because they provide free access to cutting-edge research, albeit in draft form. Journal publisher Elsevier, which has tried unsuccessfully to establish its own preprint server, has now purchased the Social Science Research Network, one of the most popular preprint servers for economics, law, and the social sciences. The move appears to be part of the publisher's larger effort to broaden its services in order to increase web traffic and protect its subscription-based journals.
Gizmodo: Aside from their wavelength, photons also have a measurable angular momentum that characterizes their rotation along their axis of travel. That value has always been observed to be some integer multiple of Planck's constant. Now Paul Eastham of Trinity College Dublin and his colleagues have manipulated photons so they have half-integer angular momentum. To do that, the researchers made use of a phenomenon first discovered in the 1830s: When light is passed through certain crystals, it creates a cylinder-like structure. Theoretical analysis of the system suggested that the resulting photons had half-integer angular momentum, and measurements proved the predictions correct. The team thinks that such photons could be used for encrypted light-based communications.
Science: The carbon dioxide monitoring station at Cape Grim, on the northwestern tip of Tasmania, recorded readings above 400 ppm for four consecutive days last week, according to Paul Krummel of Australia's Commonwealth Scientific and Industrial Research Organisation. That level stands in stark contrast to the baseline of 280 ppm for atmospheric CO2, the level at the beginning of the industrial age 200 years ago. Scientists estimate that a level of 450 ppm would correspond to a global temperature increase of 2 °C, the maximum increase allowable to avoid the most devastating consequences of global warming. Cape Grim isn't the first monitoring station to pass 400 ppm; an outpost on Mauna Loa in Hawaii reached that mark in 2013 and has occasionally done so ever since. Unlike the Mauna Loa station, the Cape Grim station is not as significantly affected by seasonal changes that cause regular rises and falls in CO2 levels. Cape Grim is also located at a latitude where strong winds perpetually blow, which prevents localized buildups of pollution. As such, measurements taken at the station are used as a proxy for global CO2 levels.
Space.com: A magnetic reconnection is an explosive release of protons and electrons that occurs when plasma from the Sun collides with a region of Earth's magnetosphere that has an oppositely directed magnetic field. The radiation released poses a threat to astronauts and satellites in orbit and to electrical systems and nuclear fusion experiments on the ground. But until recently, magnetic reconnection was studied only via theory and in laboratories. NASA's Magnetospheric Multiscale (MMS) mission—a set of four satellites in orbit around Earth—has now provided the first direct observations of those events. The satellites, which are each equipped with 25 of the fastest sensors NASA has put into orbit, take readings every 30 ms to track the motion of electrons. On 16 October 2015 MMS passed directly through a magnetic reconnection region, where the local magnetic field dropped to nearly zero, ions traveled in opposite directions, and electrons got accelerated by a strong electric field. The satellites detected a spike in the electric power generated by the electrons, a predicted behavior that had not been seen before. The mission research team next plans to move the satellites closer together so they can all enter a magnetic reconnection region simultaneously.
Nature: Upon taking over for Brazil's impeached president Dilma Rousseff, interim leader Michel Temer quickly acted to combine the ministry that deals with science and technology with the ministry that oversees telecommunications and internet regulations. The new "superministry" is subdivided into divisions, of which science is now one of the main offices. Many Brazilian scientists are unhappy with the move, which they say will further erode the ministry's authority and ability to support and fund research. The reorganization comes after several years of extreme cuts to science funding, with 2016's proposed budget cutting science funding by 37%. Three ministers had been appointed to run the science ministry in the past 16 months.
The Economist: Predicting sea-level rise due to melting ice sheets is complicated because of the difficulty in measuring the changing masses of the ice. Currently the mass is measured with laser topography and gravitational fluctuations, but those methods are limited by cost and resolution. Now Aurélien Mordret of MIT and his colleagues have developed a technique that uses seismometers to measure the vibrations created by ocean waves striking near ice sheets. The vibrations travel at different speeds depending on the compression of the rocky crust from the ice above. Mordret and his team predicted that the vibration speeds they would measure during the winter, when Greenland's ice sheet is largest, would be different from those measured in the summer, when the sheet is smallest. Using seven monitoring stations throughout 2012 and 2013, the researchers found that their calculations were in line with measurements made using other techniques. Mordret says that expanding the network of seismometer stations in Greenland and elsewhere could give a much clearer picture of changes in ice-sheet mass.
New Scientist: A collection of 60 micrometeorites found in Australia reached Earth 2.7 billion years ago, which makes them the oldest known surviving meteorites. Andrew Tomkins of Monash University and his colleagues were surprised to find the micrometeorites to begin with; the fact that the rocks contain iron oxides is rewriting part of Earth's early history. The oxides most likely formed as the meteorites passed through Earth's upper atmosphere. The meteorites landed in a highly alkaline lake, which was completely anoxic at the bottom, and got preserved in layers of limestone. Scientists believe Earth's atmosphere at that time had very low levels of oxygen, but all the supporting evidence is limited to the lower atmosphere. Several theories suggest that the upper atmosphere may have been oxygen-rich due to solar radiation splitting molecules of water, carbon dioxide, and sulfur dioxide.