Physics Today News Picks

Secrets hidden in the Earth's oldest crusts

2009-07-02T13:35:54Z

Nature: Cratons are the oldest, most stable parts of Earth's crust, and as such hold clues to Earth's early evolution.

Dewashish Upadhyay, a geochemist now at the Indian Institute of Technology in Kharagpur, analyzed the make-up of isotopes in rocks from India's Bastar craton and found that some of the rocks carry the signature of a differentiation event—the separation of materials with different geochemical properties.

This event must have taken place during the first 400 million years of Earth's history, possibly when a magma "ocean" covering the planet solidified.

Iron nuclei, not protons, appear to be the most energetic cosmic rays

2009-07-02T13:29:35Z

Science News: Scientists have generally assumed that the most energetic cosmic rays are primarily protons. That’s true even though heavier nuclei such as iron are more easily accelerated to high energies because of their greater electric charge.

Heavy nuclei, however, are also more fragile and the extraordinarily violent processes that rev them up to enormous energies can also cause these nuclei to fragment.

“Ask anybody what are the highest-energy [cosmic ray] particles, and they’d say ‘protons,’ ” says physics Nobel laureate James W. Cronin of the University of Chicago. But, as he announced 22 June at the Windows on the Universe meeting, the Pierre Auger Observatory in Malargüe, Argentina, has identified an abundance of iron nuclei at some of the highest energies its cosmic ray detectors can record.

Shifting nanoparticles cause creep

2009-07-02T13:26:42Z

Science News: Concrete creeps. And now scientists think they know why.

New measurements suggest that the rearrangement of nano-sized concrete particles is responsible for the way buildings, bridges, and other load-bearing concrete structures deform over time, a process technically known as “creep.” The new insight could allow engineers to make stronger and longer-lasting concrete, researchers report in a study to be published online in the Proceedings of the National Academy of Sciences.

Related Link
Nanogranular origin of concrete creep

The weirdest dwarf planet in the solar system?

2009-07-02T13:25:06Z

SPACE.com: The dwarf planets and other objects that litter the Kuiper belt in the far reaches of our solar system are a strange bunch, but astronomers have found what they think might be the weirdest one.

Haumea looks and spins approximately like the image above (Photo credit: Caltech)

Discovered on Dec. 28, 2004 (cataloged as 2003 EL61 and nicknamed "Santa" for a time), the minor planet now known as the dwarf planet Haumea, to honor its Hawaiian discovery, is as big across as Pluto and one-third of its mass, but shaped something "like a big squashed cigar," said one of the astronomers who studies the object, Mike Brown of Caltech.

Haumea—which has a satellite moon named Namaka—is currently undergoing a series of mutual occultations and eclipses with Namaka. "Study of these events will allow us to study this system with unprecedented detail," says Brown.

Related Link
Mutual events of Haumea and Namaka

Reviewing science in the movies

2009-07-01T14:07:22Z

NPR: From sci-fi to documentaries, good science films tell the human story behind scientific ideas. Which films get the science right, and which don't? Physicist and movie critic Sidney Perkowitz runs through some of this summer's top science flicks.

Climate burden of HFCs

2009-07-01T14:06:38Z

Nature News: Modern refrigerants designed to protect the ozone layer are poised to become a major contributor to global warming because of their future explosive growth in the developing world.

Hydrofluorocarbon chemicals (HFCs) were developed to phase out ozone-depleting gases, in response to the Montreal Protocol. But they can be hundreds or thousands of times more powerful than carbon dioxide as greenhouse gases in trapping heat.

In the new study, a team led by Guus Velders at the Netherlands Environmental Assessment Agency in Bilthoven analyzed the latest industry trends and then modeled HFC production to 2050. Their results suggest that HFC emissions could be the equivalent of between 5.5 billion and 8.8 billion tonnes of carbon dioxide annually by 2010—roughly 19% of the projected CO₂ emissions if greenhouse gases continue to rise unchecked.

Beads of innovation

2009-07-01T14:01:29Z

The Economist: A few years ago Yadong Yin was experimenting with tiny beads that changed color when a magnetic field was applied to them. This was interesting but there was no obvious way to turn them into a product

Now Yin and his colleagues at the University of California, Riverside, have come up with possible applications that range from a new type of paint to lipsticks and giant advertising billboards.

Yin’s beads are magnetochromatic microspheres. They are made from tiny blobs of polymer that contain particles of iron oxide. The structure of these particles changes in a magnetic field in a way that produces “interference” colors when light is shone on them.

It is the rearrangement of the particles’ microstructures that produces the pertinent detail.

The new research appears in the 15 June Journal of the American Chemical Society.

Future of the pebble bed modular reactor uncertain

2009-07-01T13:51:14Z

Bulletin of the Atomic Scientists: After years of investment, South Africa has abandoned its plan to develop a fleet of electricity-generating pebble bed modular reactors (PBMR), once hyped as the future of nuclear power.

Problems with the PBMR aren't new; a 2008 German report chronicles Germany's own problems developing the reactor since 1967.

China, the only other country still developing PBMR-based power reactor designs, has taken a slower approach, and it is unclear if they have run into problems as well.

CT scan nearly as good as a colonoscopy

2009-06-30T14:38:36Z

Science News: Undergoing a virtual colonoscopy might be just the ticket for people at high risk of colorectal cancer who need screening every few years, a new study finds. By spotting 85 percent of polyps, computed tomography scans offer a way to detect the precancerous growths in a way that is less invasive than a conventional colonoscopy, a European team of researchers reports in the 17 June Journal of the American Medical Association.

The beauty of Mars

2009-06-30T14:37:22Z

The Independent: The most powerful camera that has ever been used to survey another planet is capturing spectacular pictures of the surface of Mars to reveal a rich tapestry of geological features.

Located on board the Mars Reconnaissance Orbiter, a Nasa probe launched in 2005, the HiRise camera has already taken detailed images of the outlines of ancient extra-terrestrial seas and rivers—the first unambiguous evidence that shorelines once existed on the Red Planet.

Credit: NASA/JPL/University of Arizona

The camera has also witnessed in high-resolution detail the moment when the warmth of the Martian spring forced puffs of dust through the thin polar caps of dry ice—solid carbon dioxide—to form weird "starburst" patterns on the surface of the planet.

Photo: Sulfate and Clay Strata in Gale Crater Credit: NASA/JPL/University of Arizona

"Spring on Mars is quite different from spring on Earth because Mars has not just permanent ice caps, but also seasonal polar caps of carbon dioxide," said Candice Hansen-Koharcheck, of Nasa's Jet Propulsion Laboratory in Pasadena, California.

Astrophysical phenomena and mass extinctions

2009-06-30T14:28:43Z

Various: Cosmologist Adrian Melott has been researching for some time mass extinctions in the Earth's fossil records and linking them to astrophysical events.

Recently, Melott and Brian Thomas looked at the Ordovician extinction, which occurred 450 million years ago and resulted in the loss of 60% of marine invertebrates.

According to computer simulations and matched with the fossil record, they find that their data suggests that photons from a gamma-ray burst approximately over the South Pole (and no further than -75 degrees) caused the atmosphere's chemistry to change, doubling the level of ultraviolet-B solar radiation reaching the surface.

In this scenario parts of north China, Laurentia, and New Guinea—which lay north of the equator—should be a refuge from the ultraviolet effects, and show a different pattern of extinction in the "first strike" of the end-Ordovician extinction, if it was induced by such a radiation event.

Melott cautions that astrophysical phenomena may not be the main cause for extinction events but could be the trigger for tipping an already stressed environment into a catastrophic event.

In a broader article in SEED magazine Melott talks about his earlier research on cyclic mass extinctions.

There are at least 20 mass extinctions throughout the fossil record that fit a 62-million year cycle. Sometime ago Melott suggested that the solar-system's orbit around the Milky Way's center—which oscillates through the galactic plane with a period of around 65 million years, is the key—the galactic magnetic field protects the solar-system from extragalactic cosmic rays.

As the solar system "bobs" out of the galactic plane it becomes exposed to these cosmic rays which can cause enhanced cloud formation and depletion of the ozone layer, killing off many small organisms at the base of the food chain and potentially leading to a population crash.

Related Physics Today article
Recent Nearby Supernovae May Have Left Their Marks on Earth May 2002

Artifical sunscreen won’t save corals

2009-06-30T12:49:05Z

Carnegie Institution for Science: Emergency plans to counteract global warming by artificially shading the Earth from incoming sunlight might lower the planet’s temperature a few degrees, but such “geoengineering” solutions would do little to stop the acidification of the world oceans that threatens coral reefs and other marine life, report the authors of a new study in the journal Geophysical Research Letters. The culprit is atmospheric carbon dioxide, which even in a cooler globe will continue to be absorbed by seawater, creating acidic conditions.

Observing quantum phenomena at the near macro scale

2009-06-29T13:28:12Z

Nature: LaHaye and colleagues have taken an important step towards the observation of quantum phenomena in nearly macroscopic moving objects.

They report experimental evidence of an intriguing interplay between a superconducting artificial atom and a micrometre-size mechanical resonator. Remarkably, their findings can be described using the 'language' of radiation–matter interactions, which has also been successful in explaining the coupling of a superconducting artificial atom to microwave photon.

Millisecond pulsars' age reassessed

2009-06-29T13:25:54Z

UC Santa Cruz: Astronomers Bülent Kiziltan and Stephen Thorsett of the University of California, Santa Cruz, have come up with a more accurate way to peg the ages of millisecond pulsars.

The standard method for estimating pulsar ages is known to yield unreliable results, especially for the fast-spinning millisecond pulsars, says Kiziltan.

"An accurate determination of pulsar ages is of fundamental importance, because it has ramifications for understanding the formation and evolution of pulsars, the physics of neutron stars, and other areas," he adds.

The standard approach to determine the "characteristic" or "spin-down" age of a pulsar is based on two parameters: the period between pulses and the rate at which they slow down. Kiziltan and Thorsett showed that this method may over- or under-estimate the age of a pulsar by a factor of 10 when applied to millisecond pulsars.

To improve the accuracy of the standard technique, they incorporated additional constraints that arise from the spin-up process and physical limits on the maximum spin period. "We modified the age calculations to be consistent with these constraints and showed that this approach can achieve estimates closer to the true age of the pulsar," Kiziltan says.

By including in their model previously ignored features such as the maximum possible rate of rotation and subtle shifts in the observed radio frequency due to a pulsar’s motion across the sky, the team finds that some millisecond pulsars are up to 10 times younger or 10 times older than earlier estimates suggest.

GAO report queries new radiation detectors

2009-06-29T13:17:13Z

Washington Post: Federal investigators at the GAO say the next generation radiation detectors—that are scheduled to be bought by the Department of Homeland Security—are only marginally better at detecting hidden nuclear material in cargo containers than monitors already at US ports, but would cost more than twice as much.

The monitors now in use can detect the presence of radiation, but they cannot distinguish between threatening and nonthreatening material. Radioactive material can be found naturally in ceramics and kitty litter, but would be of no use in making a bomb, for instance.

The DHS has said the new machines it is developing can distinguish between kitty litter and dangerous radioactive material and produce fewer false alarms than the current ones.

The new one are also better at detecting lightly shielded material. But the machines perform at about the same level when detecting radiological and nuclear materials hidden in a lead box or casing, the most likely way a terrorist would try to sneak the materials into this country.