Physics Today Daily Edition

Subscribe to Physics Today Daily Edition feed
Please follow the links to view the content.
Updated: 1 hour 6 min ago

Coral bleaching affects northern half of Great Barrier Reef

29 March 2016

Wall Street Journal: Over the past six months, 95% of the northern section of Australia's Great Barrier Reef has been affected by coral bleaching. Bleaching occurs when ocean temperatures increase, killing the algae that inhabit coral and give the reefs their color. Without the algae, the coral starve and eventually die. The damage was assessed by an aerial survey, which is now examining the southern part of the reef. The bleaching event isn't localized to the Great Barrier Reef; it is the third global event since 1998. All have been tied to the occurrence of an El Niño system in the southern Pacific.

Arctic sea ice at record winter low for third consecutive month

29 March 2016

Guardian: During the winter of 2015–16, the average sea ice cover in the Arctic never exceeded 14.52 million km2, a record low winter maximum for the region. According to the US National Snow and Ice Data Center, March was the third straight month in which sea-ice levels reached a new low. Winter is usually the period when sea-ice extent increases, but unusually high temperatures in January and February significantly stunted its growth. Many Arctic researchers suggest that the record low increase in ice coverage could signal the beginning of an irreversible trend of continually shrinking sea ice. Recent summers have seen extreme lows in sea ice as well. Because dark water absorbs more solar energy than does bright white, snow-covered ice, the growing areas of open water have contributed to the increased temperatures year round. Within 20 to 25 years, it is likely the Arctic will be completely ice-free during summer months.

Paul R. Chagnon

29 March 2016

Pacific water temperatures could foretell heat waves in the US

29 March 2016
Associated Press: Weather forecasters in the US may soon be able to predict heat waves as much as 50 days in advance. Based on weather data from 1982 to 2015, Karen McKinnon of the National Center for Atmospheric Research and colleagues have found a strong correlation between periods of extremely dry, hot weather in the Eastern US and a system of sea-surface temperature anomalies, called the Pacific Extreme Pattern (PEP), in the Pacific Ocean. During a PEP event, a large area of the Pacific north of Hawaii experiences unusual temperature extremes: The southern part gets much hotter than normal, and the northern part gets much colder. The unusual temperature patterns appear to generate a train of atmospheric weather waves that travel across the US to the humid East Coast, where they get stopped and create a sustained high-pressure zone. Better understanding of the physical mechanisms underlying such weather anomalies could allow forecasters to improve predictions of extreme weather events. The ability to forecast a heat wave could allow time for farmers to plan irrigation efforts, city governments to set up cooling centers for the poor and elderly, and utilities to anticipate additional electrical power needs.

Turbulent dissipation sustains eruptions on Enceladus

28 March 2016
Tidal forces on the icy Saturnian moon continuously drive subsurface ocean water into and out of volcanic fissures, according to a new model.

Some of Saturn’s moons may be much younger than previously thought

28 March 2016
Ars Technica: The Saturn system is complex, comprising a gas giant surrounded by a series of planetary rings and some 62 moons. To study how the system evolved over time, Matija Ćuk of the SETI Institute in Mountain View, California, and colleagues modeled the movements of the planet and its moons. They found that the orbits of several of Saturn’s inner moons—those traveling inside the orbit of Saturn’s largest moon, Titan—have not changed as much as would be expected had the moons been in existence for billions of years. Rather, Enceladus and other moons appear to be much younger, perhaps just 100 million years old. If so, they would have formed at the same time dinosaurs were roaming Earth. If the theory is verified by future observations, it is unlikely that Enceladus, which appears to have abundant water, would be old enough for life to have started developing in the warm, interior oceans.

Nanocones increase photovoltaic light absorption

28 March 2016
IEEE Spectrum: One of the limits of solar cell technology is the amount of light that the photoreceptors can absorb. Min Gu of the Royal Melbourne Institute of Technology in Australia and his colleagues have developed a new nanostructure they think can increase that limit by up to 15% in the UV and visible ranges. The "nanocones" that Gu's team developed are topological insulators—they behave as insulators internally but have a conductive surface. The cones also take advantage of plasmonics, the generation of oscillations in the density of the material's electrons when photons hit the surface. Due to those combined effects, an array of the cones positioned over a photoelectric cell focuses incident light on the cell.

UAE chooses Japanese rocket to launch first Arab spacecraft to Mars

28 March 2016
The National (Abu Dhabi, UAE): On 22 March, the United Arab Emirates Space Agency and the Mohammed bin Rashid Space Center (MBRSC) announced that they had chosen a Mitsubishi Heavy Industries rocket to launch their first spacecraft to Mars. Named Al-Amal, or Hope, the probe is scheduled for launch in July 2020 so that its Mars arrival will coincide with the UAE's 50th anniversary in 2021. The 1.5-tonne spacecraft is the fifth built by the MBRSC but the first slated to leave Earth orbit. Designed to study the Martian atmosphere and climate, Hope is the first space mission destined for Mars developed by an Arab nation.

Asteroid bombardment may have brought water to Mars

28 March 2016
New Scientist: Cracks and other geological features on Mars’s surface indicate it once had extensive reservoirs of liquid water. Yet according to models of the Red Planet's ancient climate, the atmosphere would have been too thin to allow liquid water to remain on the surface for long. Now Tim Parker of NASA’s Jet Propulsion Laboratory says that rather than having a primordial ocean, Mars may have imported its water from asteroids that struck the planet during the Late Heavy Bombardment some 4 billion years ago. The asteroid barrage would also have heated the planet’s surface, which would have allowed the water to remain for a few hundred million years—long enough to carve up the surface, but probably not long enough for life to evolve. Parker presented his findings at the Lunar and Planetary Science Conference held last week in The Woodlands, Texas.

Renewable energy investments hit record high in 2015

25 March 2016
New Scientist: Last year $286 billion was invested in renewables, according to a study by the Frankfurt School of Finance and Management. That was 3% more than the previous record, set in 2011. The reason is twofold: cheaper solar panels and wind turbines, combined with greater investment by developing countries. China, the world's leading renewables investor, spent $102.9 billion to build some of the world’s largest solar and wind farms. The International Energy Agency credits the growth in renewables with the leveling off of global carbon dioxide emissions. Despite their record growth, however, clean technologies still provide just 10% of total generated electricity because of their inherent intermittency and the fact that most electricity-generating plants are still powered by fossil fuels.

<em>Cassini</em> finds tallest mountain on Saturn's moon Titan

25 March 2016 On Thursday at the annual Lunar and Planetary Science Conference in The Woodlands, Texas, NASA's Cassini team announced that it had identified a 3337-m-high mountain on the surface of Titan, one of the moons of Saturn. Images from Cassini have revealed a number of 3000-m-plus mountains on the moon, mostly in equatorial regions, but the team believes this mountain will prove to be the tallest. The presence of such tall mountains suggests that the moon is tectonically active. That activity could be caused by the pull of Saturn's gravity, the cooling of Titan's crust, or variations in the moon's rotation.

Organic molecules help larger water droplets form

25 March 2016

Science News: Accurately predicting cloud formation is a difficult but important element of climate models. According to Kevin Wilson of Lawrence Berkeley National Laboratory and his colleagues, the current models have not been completely successful. Water droplets form when water vapor condenses onto airborne particulate matter called aerosols. Current models assume that water-soluble molecules alter the chemistry of the droplets, which allows them to grow larger. Wilson's team tested that idea by filling a large tube with humid air and organic aerosols. Using lasers to measure the size of the water droplets that formed, the researchers found that the resulting droplets were 40% to 60% larger than expected if the organic molecules were simply dissolving. The scientists believe that a different mechanism is at work: Instead of dissolving, the organic molecules coat the exterior of the droplet, which lowers the surface tension of the water and makes it easier for additional water to condense and join the droplet.

Computer algorithm developed to read lips

25 March 2016
IEEE Spectrum: Lip-reading is a difficult task. Spoken language involves some 50 different sounds, called phonemes, yet the face presents just 10 or so different configurations, called visemes. Even for people with normal hearing, most speech is best understood through the use of both aural and visual cues. Now, Helen Bear and Richard Harvey of the University of East Anglia have improved computer lip-reading software by introducing a two-step algorithm. First, the researchers had the computer map a given viseme to the multiple phonemes it can represent; then, an analysis of video recordings of humans speaking different phonemes allowed the program to zero in on the minute visual clues that differentiate one word from another. Lip-reading software could have many uses, from helping hearing-impaired people to aiding in criminal investigations that involve recorded film footage.

Reductions in aerosol emissions may have exacerbated global warming

24 March 2016
Ars Technica: Toward the end of the 20th century, most developed countries were taking steps to reduce their aerosol emissions. Although intended to protect the environment, the action may have actually caused more harm than good when it comes to climate change, according to a study published in Nature Geoscience. The researchers looked at greenhouse gas concentrations and temperatures recorded for the years 1964 to 2010. They then projected what temperatures would have been if emissions had remained at 1964 levels. They found that aerosols’ cooling effects masked about one-third of the continental warming caused by greenhouse gas. Moreover, warming in the Arctic, which has been more accelerated than elsewhere on the planet, has been associated with sulfate aerosol reductions in Europe since 1980.

Belgium drops request for US bomb-grade uranium

24 March 2016
To reduce the risk of the material falling into terrorist hands, a US company will convert the uranium to fuel for Belgium's research reactor.

New detectors will hunt for primordial gravitational waves in Chile and Antarctica

24 March 2016
IEEE Spectrum: In 2014, before the Laser Interferometer Gravitational-Wave Observatory detected its first gravitational waves, the BICEP2 team claimed to find evidence of primordial gravitational waves embedded in the universe's oldest light. Those results did not hold up. Now scientists are building several bigger and better superconducting receivers to detect multiple frequencies of that ancient light (the cosmic microwave background, or CMB) and hopefully isolate a gravitational-wave signal. In Chile’s Atacama Desert, two new telescopes will join the Huan Tran Telescope as part of the Polarization of Background Radiation experiment. The new telescopes will house a series of “sinuous” antenna detector arrays, each consisting of four zigzagging niobium arms covered with silicon lenses. Because of their repeating structure, the arrays will be able to pick up a wider range of CMB frequencies, depending on the orientation of the arms. A similar design will be used to upgrade the sensor array on the South Pole Telescope. Work to install the new arrays is scheduled to begin later this year at both locations.

Turning atmospheric carbon into building materials

24 March 2016
New Scientist: Several proposed projects would work to alleviate climate change by removing carbon dioxide from Earth’s atmosphere. One research group in Australia is combining CO2 with calcium- or magnesium-containing minerals to create inert carbonates similar to baking soda. That material can then be used to create construction materials, such as cement and drywall. The process, called mineral carbonation, already takes place naturally on Earth in the form of weathering. A pilot plant has been built at the University of Newcastle near Sydney to see whether the process can be scaled up enough to be commercially viable.

Polar hydrogen deposits indicate Moon’s spin axis has shifted

24 March 2016
Guardian: The orientation of the Moon has changed from what it was several billion years ago, according to James Keane of the University of Arizona and his colleagues. The researchers base their finding on a reexamination of data collected in the late 1990s by NASA’s Lunar Prospector. They found that hydrogen deposits in both the north and south polar regions are displaced from the Moon’s current axis by about 5.5 degrees, which indicates that true polar wander has occurred. The researchers attribute the Moon’s shift to volcanic activity more than 3.5 billion years ago. The extreme heat could have affected the Moon's density structure in the deep mantle and caused perturbations that altered its spin. Further, the scientists propose that residual heat from that thermal anomaly continues to affect the Moon’s orientation.

The new case of missing antineutrinos

24 March 2016
A reactor antineutrino experiment highlights puzzling discrepancies between measurements and theoretical models.

Global carbon dioxide emissions decline for a second year

23 March 2016
Despite the falling price of crude oil, a changing energy landscape has had an encouraging effect on emissions.