Physics Today Daily Edition
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Updated: 12 min 11 sec ago
Los Angeles Times: Over the past several years, researchers led by Daniel Nocera of Harvard University have been working on a device that uses sunlight to split water and create fuel. Called the artificial leaf, it consists of a semiconductor wafer coated in a catalyst. When dropped in water and exposed to sunlight, the leaf causes the water molecules to split, creating hydrogen gas. Recently the researchers introduced a new element, bacteria, which draw carbon dioxide from the air and combine it with the hydrogen to generate biomass. Not only does the artificial photosynthetic process create green energy, but it could also help reduce atmospheric carbon dioxide. The researchers say they are next going to use the artificial leaf to try to convert atmospheric nitrogen into fertilizers.
Ars Technica: As the end of President Obama’s term draws near, the US Congress is working to encourage NASA to forgo its proposed 2025 asteroid visit and instead reconsider a human mission to the Moon. A bipartisan effort in the House of Representatives is being led by Mike Honda (D-CA) and Jim Bridenstine (R-OK), who are promoting a lunar mission as the best proving ground for a mid 2030s Mars mission. Because of the ever-increasing costs of the asteroid project, it has had to be scaled back several times—from sending astronauts to visit an asteroid in deep space, to bringing an asteroid to a location near the Moon, and finally to just grabbing a small boulder from an asteroid’s surface and bringing that back near the Moon. Legislators feel that a lunar mission is not only more attainable but also necessary to remain competitive with other nations, such as Russia and China, and to provide opportunities for the nascent commercial space industry.
Science: Because the US conducted extensive nuclear testing there during the 1940s and 1950s, several islands in the Marshall Island chain became highly contaminated and had to be abandoned. Almost 60 years later, researchers have determined that the gamma radiation levels of five of the islands have dropped to less than 40 millirem per year, well below the 100 millirem per year threshold deemed safe for human habitation. Bikini Island, however, still registers 184 millirem per year. Because people can absorb radiation in other ways, such as by consuming contaminated food, more tests will be needed before anyone will be allowed to occupy the islands.
Nature: As of 6 June, the seven underwater instrument arrays that make up the Ocean Observatories Initiative (OOI) are up and running. Nearly 10 years in the making, the NSF-supported project aims to stream information gathered by more than 900 sensors on the ocean’s physical, chemical, geological, and biological properties and processes. About 85% of OOI data are available in real time on the project’s website, and more will be added each week. The array off the US East Coast has already measured the air–sea fluxes caused by a hurricane, and the West Coast array has studied a warm patch of water influencing weather patterns in California. Proposed budget cuts, however, threaten to affect the servicing of the instrument arrays, which have yet to be properly tested. At least a year’s worth of data will be needed to assess their worth and usefulness to the scientific community.
Wall Street Journal: Until now only national governments have undertaken space missions beyond Earth orbit. That may soon change as Moon Express, a private US space company, readies its MX-1 commercial lunar lander for a 2017 launch. Moon Express is competing for the Google Lunar X prize, to be awarded to the first company to land a privately funded robotic spacecraft on the Moon. US launches are regulated by the Federal Aviation Administration, which is currently reviewing the process for granting commercial operations permission to conduct space missions beyond Earth’s gravitational pull. Such permission must take into account international treaty obligations and concerns over public safety, national security, and foreign policy. The FAA is expected to reach a decision within the next few weeks.
New York Times: More than a century ago, the invention of the vacuum tube kicked off an electronics revolution. However, the tubes were big and bulky, and by the 1970s, they were replaced by the transistor. One problem with the transistor design is that the smaller the transistor gets, the more it leaks electrons because of a phenomenon called quantum tunneling. Now Axel Scherer of Caltech and his coworkers are developing a new take on the old vacuum-tube technology. Scherer's team uses the quantum tunneling effect as the switch to control the flow of electrons in tiny metal vacuum tubes. The new tubes use less power and work faster than current transistor-based chips, so they could have many applications, such as in space and aviation.
In a space-based gravitational-wave detector, gravity should be the only force accelerating an interferometer.
Nature: Usually with volcanoes, the surface subsides around them because of the draining of magma-filled chambers in the ground beneath. But magma may pool in chambers far from any active volcano, according to a new study. Using satellite radar data and geodetic surveys, Ian Hamling of GNS Science in New Zealand and his colleagues were able to distinguish an unexpected rise in the ground in the Taupo Volcanic Zone of New Zealand’s North Island. Moreover, the ground appears to have been rising for more than a half century and at an ever-increasing rate—from about 5 mm/year in the 1950s to some 12 mm/year by the mid 2000s. However, the researchers say the magma increase does not necessarily mean an eruption is imminent. Moreover, similar processes have probably been going on all over the world; it is only now that instruments have been developed to detect them.
New York Times: Smart materials and technologies are enabling the construction of zero-energy homes, which generate as much energy as they consume over the course of a year. The energy efficiency comes from a renewable energy system, such as solar panels, combined with improved building materials, including spray-foam insulation, dual-pane windows, and LED lighting. Smart thermostats and remotely controlled water heaters help regulate the flow of energy. Since 2013 the US Department of Energy has certified about 700 such homes, and it estimates it will certify another 1000 this year and 3000 in 2017.
New Scientist: A new study reveals a disparity between the two leading methods for calculating the rate of expansion of the universe. Adam Riess of the Space Telescope Science Institute in Baltimore, Maryland, and his colleagues compared the two best techniques—looking at the size of the temperature fluctuations in the cosmic microwave background (CMB) and measuring the rate at which distant galaxies are receding. The receding galaxies method, which Riess pioneered in the 1990s, implies that the universe is expanding 9% faster than theoretical estimates based on CMB data suggest. The researchers say that discrepancies in the CMB data may be to blame. If so, newer equipment and measuring techniques should resolve the problem. If the models prove to be accurate, however, the discrepancy could indicate that changes need to be made to our understanding of the laws of physics; for example, dark energy may be growing denser.
NPR: Complaints regarding the new types of brooms available in the sport of curling prompted the World Curling Federation to organize a summit to test brushes and sweeping techniques. Traditionally, the game hinges on the skill of the thrower, who slides the stone down a sheet of ice toward a target called the house. To help direct it toward the house, two sweepers use brooms to sweep the ice in front of the stone. However, some of the new brooms actually scratch the ice, which gives the sweepers much more control over the stone than they have had traditionally. To formulate new rules and equipment standards to ensure that the spirit of the game is maintained, top-level athletes and curling experts gathered at the summit to test more than 50 brush constructions and various sweeping techniques.
Developments in snapshot imaging and computational processing improve resolution at unprecedented frame rates.
Scientific American: The 2017 spending bill passed last week by the US House Appropriations Committee calls for a 20% cut from last year’s spending for climate science research by the National Oceanic and Atmospheric Administration. Among the programs affected are carbon-monitoring stations from the 1950s that are in dire need of updating, a proposed facility to verify fossil fuel emissions by nations that signed last year’s Paris climate agreement, and a proposal to expand NOAA’s ocean acidification monitoring program. The bill would also impose a 12% cut from 2016 funding levels for NASA’s earth sciences division.
New York Times: On 2 June the Norwegian Academy of Science and Letters announced the recipients of this year’s Kavli Prizes. The astrophysics prize went to Ronald Drever and Kip Thorne of Caltech and Rainer Weiss of MIT for their role in the detection of gravitational waves. The nanoscience prize was shared among Gerd Binnig (formerly of IBM Zurich Research Laboratory), Christoph Gerber of the University of Basel in Switzerland, and Calvin Quate of Stanford University for the invention of atomic force microscopy. The neuroscience prize was given to Eve Marder of Brandeis University; Michael Merzenich of the University of California, San Francisco; and Carla Shatz of Stanford for their discoveries concerning the flexibility of the nervous system and the brain. The recipients of each prize split $1 million.
New Scientist: Although curved optical lenses are ubiquitous in telescopes, microscopes, and cell phone cameras, the size of those devices is limited by the thickness and weight of the glass. Now researchers have used metamaterials to create a lens that is thinner than the wavelengths of the light waves it focuses. The scientists carved tiny blocks of titanium dioxide, rotated them at different angles, and mounted them on a thin piece of glass. Each 600-nm-thick lens, which was tuned to either red, green, or violet light, achieved sharper focus than a 55-mm-thick Nikon lens, with minimal loss of light. Next the research team plans to expand the range of color the lenses can detect.
Economist: In the mid 1970s, physicist Stephen Hawking challenged the theory of causal determinism by proposing that information could be lost forever if matter were sucked into a black hole because the black hole would eventually disintegrate. Now, however, he has revised that idea and shows how the evaporation of black holes does not necessarily mean that all the information contained in the swallowed matter will be destroyed. Hawking instead proposes that when matter falls into a black hole, it leaves traces of the information it contained in the form of the number and position of two soft particles, photons and gravitons. The informational record remains even after the black hole has disappeared. Although the explanation is incomplete because it accounts for only one property of matter—its electric charge—the principle supports the established laws of physics and could lead to a more complete understanding of black holes and the universe.
Measurements of iron's thermal conductivity hint that the planet's solid center is relatively young—and not responsible for Earth's dynamo long ago.
Washington Post: As the world’s population grows and countries’ economies improve, more people are purchasing air conditioning units for their homes and businesses. According to a study published last year, as many as 1.6 billion new air conditioners could be installed by 2050. To discuss the global impact on climate those installations will have, representatives from around the world are meeting in San Francisco this week at the seventh Clean Energy Ministerial. They will consider ways to lessen the environmental impact, such as by designing air conditioners to be more energy efficient and by finding alternative coolants to hydrofluorocarbons, which contribute to global warming.