Physics Today Daily Edition
Los Angeles Times: In the early 1980s the Voyager spacecraft measured the length of Saturn's day to be 10.6 hours based on the planet's magnetic field. But when Cassini reached the planet in 2004, it obtained a different result. Subsequent measurements revealed that the planet's magnetic field, unlike Earth's, is aligned with the axis of rotation; it cannot, therefore, be used for an accurate measurement. Other techniques that attempted to use the planet's wind patterns proved even less accurate. Ravit Helled of Tel Aviv University and his colleagues have now used Saturn's gravitational field to measure the length of the day, which they found to be 6 minutes shorter than the original Voyager measurement. The technique uses the periodic changes in pull that Cassini feels as Saturn rotates as well as measurements of the planet's oblateness. The researchers confirmed the accuracy of the technique by testing it against Jupiter, whose day has a well-known length.
Nature: The oxygen atom in a water molecule is tightly bound to the two hydrogen atoms, but it also experiences a slight connection with the hydrogen in neighboring molecules. Because of this, as water freezes, the molecules arrange themselves into three dimensional tetrahedral shapes. Now, Andre Geim of the University of Manchester, UK and his colleagues have discovered that water pressed between sheets of graphene freezes into an ice in which the molecules form two-dimensional layers of square shapes. The structure could be the 18th different type of water ice discovered. Geim's team calculated that the pressure exerted on the water by the graphene sheets exceeds 10 000 atm or 1 gigapascal.
Nature: On 24 March Department of Energy (DOE) secretary Ernest Moniz announced that the agency was looking for a variety of temporary localized sites for nuclear waste storage. The agency will also continue its search for a permanent, geologically stable location for long-term storage of nuclear weapons waste. Moniz says that the key to the localized sites is that the agency will be seeking consent-based locations instead of attempting to force storage sites into areas where the local population does not want them. The DOE's new plan, with President Barack Obama's approval, also frees commercial and military waste to be stored in separate locations. Thanks to the policy change, waste repositories will no longer have to be equipped to store waste that has different requirements and risks. The DOE's 2016 budget proposal includes funding for an experimental borehole for long-term storage. The agency also plans to begin evaluating potential storage sites for commercial waste, but construction of such facilities would require approval from Congress.
Science: The Large Hadron Collider (LHC) at CERN was planned to begin circulating beams of particles the entire way around the accelerator's 27-km circumference this week. However, an electrical short discovered over the weekend has delayed the full restart while the short is repaired. That task could take as little as a few days or as long as several weeks. Shorts are not uncommon as the LHC is slowly ramped up, but the time it takes to repair them can be significantly increased if supercooled electronics first have to be warmed up. The scientists working at the accelerator plan to use x-ray imaging to examine the area to determine if they can remove the metallic source of the short by melting it or blowing it away with helium.
New York Times: Getting the last of anything out of a bottle usually involves scraping the inside. Depending on the viscosity of the substance, up to a quarter of the contents of a bottle may end up being thrown out. Now, Kripa K. Varanasi of MIT and graduate student J. David Smith have created a startup, called LiquiGlide, to market a coating they developed that allows a bottle's contents to easily slide out, regardless of the viscosity. Thanks to its porous surface, their material traps a lubricant that can be customized to best match the properties of the intended contents of the bottle. The lubricant makes the inner surface of the container superhydrophobic, which prevents the contents from binding to the container's interior.
New Scientist: Last week's solar eclipse was visible across much of Europe. That meant that the solar generating capacity of many countries was reduced briefly and other energy sources needed to be deployed. Since 2006, the European Union has spent €3 billion ($3.28 billion) on developing smart-grid technologies to help balance the distribution of energy in response to fluctuations in demand or production. In Germany, for instance, which gets 26% of its power from solar and wind, last week's eclipse provided an important test of the grid's ability to handle sudden changes. To be on the safe side, the country doubled its network staff for the day and also turned off four aluminum plants that draw a lot of power. During the eclipse, Germany's solar energy production dropped from 38.2 GW to 23.2 GW. No problems were reported, however, in either Germany or any of the countries that contribute the other 51 GW of solar power in the EU.