1887

News Picks

Physics Today’s online staff summarize the most important and interesting news about science from the world's top media outlets.

There are 9 posts for the selected month (July 2015).
July 6, 2015 1:30 PM

Universe’s Big Bang may end with a Big Rip

Guardian: Most scientists agree that the universe began with a Big Bang, but how it will end continues to be a matter of discussion. Various scenarios have been proposed, among them the Big Crunch, in which the universe’s expansion slows and gravity causes the universe to collapse in on itself, and the Big Freeze, in which the universe continues to expand to the point where matter becomes so spread out and cold that all movement ceases. The latest theory is the Big Rip, in which the universe’s ever-accelerating expansion results in the explosive tearing apart of all matter. In their paper in Physical Review D, Marcelo Disconzi of Vanderbilt University in Tennessee and colleagues reexamine the concept of cosmological bulk viscosity, or the ability of a fluid-like universe to expand or contract. They put forth the idea that the expansion of the universe could continue to accelerate until it reaches some critical point—the Big Rip—at which everything, even the constituents of matter, will be annihilated. Fortunately, that won’t happen for at least another 22 billion years.
July 2, 2015 2:10 PM

Celestial sleuths pinpoint exact moment iconic VJ-day photo was taken

Los Angeles Times: It has long been assumed that the famous VJ-day photo of a US Navy sailor and a woman in white kissing in Times Square was taken just after 7:00pm on 14 August 1945—when the end of World War II was officially announced. Now a team of astronomers has used a distinctive shadow to determine that the iconic photo by Life magazine photographer Alfred Eisenstaedt was actually taken earlier that day. Donald Olson of Texas State University and colleagues studied hundreds of vintage photos, maps, and building blueprints to discover what cast the shadow: an L-shaped sign on the roof of the Hotel Astor. Using trigonometry and geometry, they then figured out where in the sky the Sun had to have been to cast the shadow. From that they were able to pinpoint the exact moment the photo was taken: 5:51pm. The researchers' findings have been published in the August 2015 issue of Sky & Telescope.
July 2, 2015 2:00 PM

Solar Impulse breaks record for longest solo flight

BBC: Andre Borschberg, who is piloting the long-range solar-powered aircraft Solar Impulse 2, has broken the record for the longest nonstop solo flight without refueling. Traveling from Japan to Hawaii on the seventh leg of an around-the-world tour, Borschberg surpassed the previous record of 76 hours in the air—set by Steve Fossett in 2006—and still has at least another 40 hours to go. Borschberg has been tag-teaming with copilot Bertrand Piccard, who will take over in Hawaii to fly the next leg of the journey to Phoenix, Arizona. Once they complete their circumnavigation of the globe, which began and will end in Abu Dhabi, United Arab Emirates, the aircraft will have flown a total of 35 000 km. Solar Impulse 2 runs entirely on solar power, and its average speed is just 50–100 km/hr, much slower than that of liquid-fueled aircraft.
July 2, 2015 1:57 PM

Comet 67/P covered in sinkholes and caves

Ars Technica: The European Space Agency's Rosetta spacecraft, which is in orbit around comet 67P/Churyumov-Gerasimenko, has been supplying astronomers with highly detailed pictures of the comet's surface. Many of those pictures have revealed sinkholes as wide as 200 m and as deep as 180 m. At first it was thought that the sinkholes could be the result of outgassing—as the comet approaches the Sun, frozen gases warm and explode—but the amount of material in outgassing events didn't match the size of any of the sinkholes. Instead, Dennis Bodewits of the University of Maryland, College Park, and his colleagues say it appears to be the other way around—the outgassing results from the formation of the sinkholes. The holes themselves form as surface ice sublimates and dust fills the depression until it collapses, creating a deeper hole. Bodewits's team believes that the comet's nucleus is 75–80% empty space, which is what allows so many sinkholes to form.

July 2, 2015 11:55 AM

Potential dark-matter signal likely just undiscovered pulsars

New Scientist: In 2009, NASA's Fermi satellite began detecting an apparent excess concentration of gamma rays that appeared to come from the Milky Way's central region. According to some theories, the signal could be the result of dark-matter collisions in the dense core region of the galaxy. Now, two independent teams analyzing the data argue that the signal did not account for thousands of previously undiscovered pulsars, which are rapidly rotating neutron stars that emit bright pulses of radiation. The finding is significant not just for potentially eliminating a sign of dark-matter collisions but for massively increasing the number of known pulsars in the Milky Way. More data will soon be available from Fermi that is expected to clarify the situation even further.
July 1, 2015 3:00 PM

Low-dose radiation has small but measureable long-term risk

Nature: A study of 300 000 nuclear-industry employees from France, the UK, and the US has provided the first clear look at the risks of low-dose ionizing radiation. The researchers obtained exposure records dating back 60 years for employees who worked in the industry for at least one year while wearing a dosimeter. The researchers then followed up to track mortality from leukemia, lymphoma, and multiple myeloma. The study revealed that on average the workers received 1.1 mSv per year above the average yearly background radiation, which is about 2–3 mSv. As the amount of radiation exposure increased, there was a linear increase in the rate of leukemia as well. Similar patterns for other cancers were not statistically significant. Instead of the 134 deaths expected from leukemia, the researchers found there were 531. And while none of those deaths occurred in any employee who received less than 50 mSv of radiation, the linear extrapolations suggest that every 10 mSv of radiation exposure increases the risk of leukemia by 0.002%.

July 1, 2015 2:30 PM

European Space Agency gets new director general

BBC: As of today the European Space Agency (ESA) has a new director general—Johann-Dietrich Woerner. He replaces Jean-Jacques Dordain, who had held the position since 2003. Besides continuing ESA’s ongoing programs and projects, such as the Rosetta mission, Woerner says he wants to plan for ESA's future, what he terms Space 4.0. That future includes the commercialization of space and increased interaction with society. Before assuming the ESA directorship, Woerner served as chief of the executive board of the German Aerospace Center.
July 1, 2015 1:54 PM

Hubble suggests quasars are driven by galactic collisions

Ars Technica: Quasi-stellar radio sources, or "quasars," are supermassive black holes, found at the center of galaxies, that produce extreme amounts of light as they pull material into themselves. The material swirling around the black holes is much brighter than the starlight of their host galaxies and can be up to 100 times brighter than all the stars in the Milky Way put together. That brightness disparity makes it hard to study quasars and to look past them to study their host galaxies. However, the difference in brightness is much less in certain areas of the spectrum. C. Megan Urry of Yale University and her colleagues used a near-IR camera on the Hubble Space Telescope to examine 11 quasars, all roughly 12 billion light-years away. They were selected because each is partially obscured by dust, which further reduces the brightness disparity. Urry's team found that all 11 of the host galaxies were undergoing collisions with other galaxies. That discovery supports the theory that galactic collisions drive the feeding of the black holes by disrupting the material surrounding them.

July 1, 2015 12:30 PM

Muon tomography used to inspect industrial equipment

Science: A new technique to scan equipment for problems or to look for nuclear material and other contraband uses the scattering of muons created when cosmic rays collide with molecules in Earth’s upper atmosphere. Able to penetrate matter more deeply than some other particles, muons have been used to image concrete degradation, valve conditions, and pipe-wall thickness at nuclear plants, according to a study published in AIP Advances. Imaging muons requires two sets of detectors to map the muons' trajectories before and after they pass through the object being studied. The denser the object, the more the muons are deflected. That information is then used to create a three-dimensional image of the mass distribution. Because muon radiation is ubiquitous on Earth and nonharmful to humans, muon tomography poses fewer problems and requires fewer safety measures than x-ray imaging. However, it takes longer to create an image, so it is better suited for routine inspections and monitoring.
No further posts for this month
This is a required field
Please enter a valid email address

Oops! This section does not exist...

Use the links on this page to find existing content.

24f368529419bb89b4d14b71017867b2 weblog.blogzxybnytfddd
Scitation: News Picks - Blog
http://aip.metastore.ingenta.com/content/aip/magazine/physicstoday/news/news-picks