The 2013 TVs of CES are bigger and smarter, but what about the picture?

I expect great things out of the Panasonic ZT60 plasma.

(Credit:
Sarah Tew/CNET)

Will flat-panel TV picture quality get even better in 2013?

I'm guessing "Yes" in the case of the Best of CES nominee Panasonic TC-PZT60 and the re-engineered Samsung UNF8500, very likely the two best-performing TVs of 2013 under $10,000.

But those two are hardly the TV hardware poster children of the 2013 Consumer Electronics Show, where all the headlines touted expensive 4K and OLED sets as well as new gadgetry of questionable usefulness. Finger-gesture control, anyone?

I got a chance to see both the Panasonic and the Samsung plasmas in extended private viewing sessions and suffice it to say, I think both will be able to surpass the mind-bogglingly good Panasonic TC-PVT50 of 2012 at doing what TVs are supposed to do best: make beautiful pictures. I can't wait to review them, nor to test a few other TVs that stood out from a picture quality perspective.

Other TVs that piqued my videophile interest

• Panasonic's entire plasma lineup Based on what I saw at the show, last year's reviews and this year's pricing so far, I wouldn't be surprised if the 2013 Best TVs list at CNET looked as top-heavy with Panasonic plasmas as the 2012 list. Each of the company's 2013 plasma series models, with the exception of the lowest-end X60 perhaps, should be among the best-performing in its price class.
  
• Sony KDL-55W900A The successor to our favorite edge-lit LED TV of 2012, the W900A keeps the company's excellent local-dimming scheme but is unfortunately only available in one size: 55 inches.


• Vizio M series Meanwhile our second-favorite edge-lit LED of 2012 has a whole litter of descendants in various sizes, and all of them do local dimming too. The company is proud of its home-grown dimming, and from what I saw on the 2012 M3D0KD series, the M should be a solid performer. It's also noteworthy that select sizes in the very affordable E series will be the first to do dimming from a "direct LED" configuration.


• Samsung UNF8000 series The biggest TV company is pushing its revamped Smart TV suite to the world, but to me its engineers talked up the fact that this flagship finally put real local dimming back into its highest-end LEDs. Both the F8000 and the F7500 can dim the letterbox bars, which leads to big improvements in perceived contrast for ultra-widescreen movies, but only the F8000 gets dimming across the whole screen. From what I saw of an early sample it looked great, and color was also exceedingly accurate.


• Samsung UN85S9 The winner of the TV category for Best of
  CES got there partly with unique style and buzz-worthy 4K resolution, but what put it atop other 4K sets I saw was the inclusion of local dimming from a full-array LED backlight. It's Samsung's first so-equipped TV since the excellent UN55B8500, and my bet for the best-performing 4K TV of 2013. I just hope it doesn't fall over and crush me during the review.


• Sharp Purios The company's first shipping 4K TV will also be the first to receive THX's 4K display certification -- not a guarantee that it'll be a good performer, but still a positive sign. I saw an encouraging demo where the Purios' image processing, dubbed ICC (integrated cognitive creation), seemingly revealed a bit more depth and detail than a comparison model. I also liked the company's new "Moth eye" screen finish, which straddles the line between matte and glossy and in demo form did a great job suppressing reflections. I was told the finish might not make it onto the shipping Purios, but I hope it does.


• LG Hecto laser projector At $10,000 the Hecto has the distinction of being the cheapest 100-inch-or-larger TV shown at CES 2013, trumping the 110-inch
  LEDs by a few hundred thousand dollars. Essentially a deconstructed rear-projection TV, this short-throw laser projector includes its own screen and even has speakers. It's the only product of its kind from a major maker, and I'm excited to see how it competes against similarly-priced 80-inch
  LED TVs.


• LG LA8600 Even LG's best TVs last year had disappointing performance, but the company's engineers promised me they've done better this year. I assume LG's best non-4K 2013 LED, the LA8600, will showcase those improvements.


• LG 55PM9700 After more than 10 years of doing what I do, I'm more excited to review LG's OLED TV than I've ever been to review any product. Ever. Will its color-filter WRGB technology affect the jaw-dropping contrast and color response I expect from OLED? What about off-angle, color accuracy, even passive 3D? I hope to know soon how our third Best of CES nominee fares.

It's gonna be tough to find an OLED TV in stores.

Uh, what about 4K and OLED?
In our preview we called out both of these buzz-grabbing trends as the stars of CES, but it's important to remember that showstopping display technology usually takes years to go mainstream. You'll be hard-pressed to find 4K TVs anywhere on store shelves in 2013, and OLED will be as rare as a Tesla Roadster. The TVs with both, introduced by Sony and Panasonic, were prototypes that are still years away.

TVs with 4K, or Ultra High Definition (UHD) resolution, were front and center in nearly every major maker's booth, and their huge screens and slow-moving, short-looping demo material often looked very good (although often worse than I expected). No pricing was announced for any of the major makers' new 4K sets, however, and product managers I pressed on the question were universally more tight-lipped than usual -- not a good sign.

If Samsung's 85-inch 4K TV costs less than $20K, I'm a monkey's uncle.

Sony mentioned "a cost that is right around that of a premium HDTV" for its smaller XBR-X900 sizes, and I'm guessing that means $5,000 for the 55-incher. While LG's smaller 4K models might cost a bit less than that, I don't think you'll be able to buy a non-Chinese 4K TV for less than $4K this year. I'll be interested to test new sets from Chinese makers like Hisense (its 4K TVs go down to 50 inches) and TCL, but I'm not expecting them to match the picture quality of the established brands.

And then there are OLED TVs, which LG says will finally be shipping in March for $12,000. Even if you have that kind of cash I'm guessing it will be nearly impossible to lay your hands on one -- initial quantities will be extremely limited. The only other TV maker close to production is Samsung, which says "this year" for its KN55F9500. But the company still hasn't released a final design, and I'm still skeptical the TV will ship.

Whizbang doodads, newfangled thingamabobs, miscellaneous frippery
No CES TV wrap-up would be complete without passing mention of all the extra bullet points TV makers will pack onto specification sheets that have nothing to do with the core mission of making great pictures. I'll try to get it all into one paragraph.

The fire hose: Samsung TVs now have more than 2,800 apps.

Samsung, the king of featuritis, has a new Smart TV suite that can control your cable box as well as recommend upcoming shows and consolidate searches of on-demand video sources (just not Amazon). Sony is pushing NFC pairing, a second-screen app, and DirecTV-friendliness. LG also touts NFC, along with improved voice control and a better motion remote. Panasonic wants to entice you with an optional pen accessory for marking up documents onscreen (huh?), voice control, a touch-pad controller, and a pop-up camera on some models. Vizio has M-Go, a studio-sanctioned streaming app, as well as a new streaming-3D service and HTML5 support in higher-end sets. Everybody has dual-core processors, built-in Wi-Fi, and tons of apps that you'll never use. But at least they all have Netflix.

In the preview I wistfully asked for a dumb TV with all the picture quality enhancements of a flagship model for a bit less money. None was announced. Maybe next year.

A look at the exciting new technology of Sony's 4K OLED TV

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Pictures: Civil War Shipwreck Revealed by Sonar

Photograph by Jesse Cancelmo

A fishing net, likely only decades old, drapes over machinery that once connected the Hatteras' pistons to its paddle wheels, said Delgado.

From archived documents, the NOAA archaeologist learned that Blake, the ship's commander, surrendered as his ship was sinking. "It was listing to port, [or the left]," Delgado said. The Alabama took the wounded and the rest of the crew and put them in irons.

The officers were allowed to keep their swords and wander the deck as long as they promised not to lead an uprising against the Alabama's crew, he added.

From there, the Alabama dropped off their captives in Jamaica, leaving them to make their own way back to the U.S.

Delgado wants to dig even further into the crew of the Hatteras. He'd like see if members of the public recognize any of the names on his list of crew members and can give him background on the men.

"That's why I do archaeology," he said.

(Read about other Civil War battlefields in National Geographic magazine.)

Published January 11, 2013

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CDC: Flu Outbreak Could Be Waning

The flu season appears to be waning in some parts of the country, but that doesn't mean it won't make a comeback in the next few weeks, according to the Centers for Disease Control and Prevention.

Five fewer states reported high flu activity levels in the first week of January than the 29 that reported high activity levels in the last week of December, according to the CDC's weekly flu report. This week, 24 states reported high illness levels, 16 reported moderate levels, five reported low levels and one reported minimal levels, suggesting that the flu season peaked in the last week of December.

"It may be decreasing in some areas, but that's hard to predict," CDC Director Dr. Thomas Frieden said in a Friday morning teleconference. "Trends only in the next week or two will show whether we have in fact crossed the peak."

The flu season usually peaks in February or March, not December, said Dr. Jon Abramson, who specializes in pediatric infectious diseases at Wake Forest Baptist Health in North Carolina. He said the season started early with a dominant H3N2 strain, which was last seen a decade ago, in 2002-03. That year, the flu season also ended early.

Click here to see how this flu season stacks up against other years.

Cheryl Evans/The Arizona Republic/AP Photo

Increasing Flu Cases: Best Measures to Ensure Your Family's Health Watch Video

Because of the holiday season, Frieden said the data may have been skewed.

For instance, Connecticut appeared to be having a lighter flu season than other northeastern states at the end of December, but the state said it could have been a result of college winter break. College student health centers account for a large percentage of flu reports in Connecticut, but they've been closed since the fall semester ended, said William Gerrish, a spokesman for the state's department of public health.

The flu season arrived about a month early this year in parts of the South and the East, but it may only just be starting to take hold of states in the West, Frieden said. California is still showing "minimal" flu on the CDC's map, but that doesn't mean it will stay that way.

Click here to read about how flu has little to do with cold weather.

"It's not surprising. Influenza ebbs and flows during the flu season," Frieden said. "The only thing predictable about the flu is that it is unpredictable."

Dr. William Schaffner, chair of preventive medicine at Vanderbilt University Medical Center in Nashville, Tenn., said he was expecting California's seeming good luck with the flu to be over this week.

"Flu is fickle, we say," Schaffner said. "Influenza can be spotty. It can be more severe in one community than another for reasons incompletely understood."

Early CDC estimates indicate that this year's flu vaccine is 62 percent effective, meaning people who have been vaccinated are 62 percent less likely to need to see a doctor for flu treatment, Frieden said.

Although the shot has been generally believed to be more effective for children than adults, there's not enough data this year to draw conclusions yet.

"The flu vaccine is far from perfect, but it's still by far the best tool we have to prevent flu," Frieden said, adding that most of the 130 million vaccine doses have already been administered. "We're hearing of shortages of the vaccine, so if you haven't been vaccinated and want to be, it's better late than never."

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Muscle mimic pulls electricity from wet surface

Electricity has been squeezed from a damp surface for the first time, thanks to a polymer film that curls up and moves – a bit like an artificial muscle – when exposed to moisture. The film could be used to run small, wearable devices on nothing but sweat, or in remote locations where conventional electricity sources aren't available.

When a dry polymer absorbs water, its molecular structure changes. This can, in principle, be converted into larger-scale movement, and in turn electricity. But previous attempts at creating a material powered by a moisture gradient – the difference in chemical potential energy between a wet region and a dry region - failed to produce a useful level of force.

These unsuccessful tries used a polymer called polypyrrole. Now Robert Langer and colleagues at the Massachusetts Institute of Technology have turned to the material again, embedding chains of it within another material, polyol-borate. This more complex arrangement mimics structures found in muscles as well as in plant tissues that bend in response to changes in humidity.

Flipping film

The result looks like an ordinary piece of thin black plastic, but when placed on a wet surface, something extraordinary happens. As the material absorbs water, its end curls away from the surface and the film becomes unstable, so it flips over. The ends have now dried out, so they are ready to absorb more water, and the whole process repeats itself. This continuous flipping motion lets the film travel across a suitably moist surface unaided.

Langer found that a 0.03-millimetre-thick strip, weighing roughly 25 milligrams, could curl up and lift a load 380 times its mass to a height of 2 millimetres. It was also able to move sideways when carrying a load about 10 times its mass.

To extract energy from this effect, Langer's team added a layer of piezoelectric material – one which produces electricity when squeezed. When this enhanced film, weighing about 100 milligrams, flipped over, it generated an output of 5.6 nanowatts – enough to power a microchip in sleep mode.

Electricity from sweat

Though the output is small, it is proof that electricity can be extracted from a water gradient. "To the extent of our knowledge, we are the first to utilise a water gradient, without a pressure gradient, to generate electricity," says Langer.

Large-scale energy harvesting is unlikely as the size of the device needed would be impractical, but it could be used to power small devices such as environmental monitoring systems in remote locations. "It will be interesting for applications where the amount of energy needed may be low but where access to energy may be difficult," says Peter Fratzl at the Max-Planck Institute of Colloids and Interfaces in Potsdam, Germany, who was not involved in the work.

Another application, Langer suggests, would be to place the film inside the clothing of joggers or athletes. The evaporation of sweat could generate enough electricity to power sensors monitoring blood pressure and heart rate.

Journal reference: Science, DOI 10.1126/science.1230262

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.

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Python clings to Qantas wing on two-hour flight

SYDNEY: It was not quite a "Snakes on a Plane" scenario, but passengers on a Qantas jet watched in amazement as a three-metre (nine feet) python clung to the outside of their aircraft during a flight.

The Australian carrier said the flight from the Queensland city of Cairns to Port Moresby, capital of the Pacific island nation of Papua New Guinea, took off early Thursday morning with the unintended passenger tucked into its wing.

"The snake was seen by passengers once (the plane) reached cruising altitude," a Qantas spokesman told AFP.

"It was still on the aircraft when it arrived in Port Moresby but it had died by that stage."

Once they spotted it on the wing, passengers watched as the reptile engaged in a life-and-death struggle to maintain its grip on the plane despite the winds and chilly altitude temperatures for the two-hour journey.

Passenger Robert Weber told Fairfax Media Friday that while people at the front of the plane were unaware of the python, those at the back were "all totally focused on the snake and how it might have got onto the aircraft".

Unlike the 2006 "Snakes on a Plane" movie starring Samuel L. Jackson, this reptile did not affect the flight.

"There was no panic. At no time did anyone stop to consider that there might be others on board," Weber said.

He added that the snake had been nestled neatly at first, but once the wind caught the end of its tail, it was "pulling him straight out" and from then on it became a hopeless "life-and-death struggle".

"I felt quite sad for it, really," he said.

An expert said the snake was probably a scrub python, Australia's longest snake and one common in northern Queensland.

Qantas said it had never heard of anything similar happening before, adding that there was no way the reptile could have accessed the cabin.

- AFP/ck

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Uh-oh, Windows RT. Samsung's got second thoughts

Samsung's Ativ Tab runs Windows RT, shown here with the mandatory new Metro interface by Damien Cusick, general manager of Samsung Electronics UK, at a press conference at IFA.

(Credit:
Stephen Shankland/CNET)

LAS VEGAS--Microsoft launched Windows RT with grand ambitions only a few months ago, but CNET has learned the operating system is facing yet another setback.

This time it's Samsung having second thoughts about the computer software that runs on cellphone chips.

Mike Abary, the Samsung senior vice president who oversees the company's PC and
tablet businesses in the U.S., told CNET today at the Consumer Electronics Show that the Korean electronics giant won't be launching its Qualcomm-powered Windows RT device in the U.S. It's unclear what the company's plans are for the non-U.S. markets.

Abary noted Samsung reached its decision about he device, dubbed the Ativ Tab, for two main reasons. First, feedback from its retail partners indicated demand for such products is only modest. Second, Samsung determined it would take a lot of investment to inform consumers about the benefits of Windows RT. Here's what he told CNET:

There wasn't really a very clear positioning of what Windows RT meant in the marketplace, what it stood for relative to Windows 8, that was being done in an effective manner to the consumer. When we did some tests and studies on how we could go to market with a Windows RT device, we determined there was a lot of heavy lifting we still needed to do to educate the customer on what Windows RT was. And that heavy lifting was going to require pretty heavy investment. When we added those two things up, the investments necessary to educate the consumer on the difference between RT and Windows 8, plus the modest feedback that we got regarding how successful could this be at retail from our retail partners, we decided maybe we ought to wait.

Abary added that one of the big selling points for Windows RT is the devices should be less expensive than those using
Windows 8. However, Samsung found that it would have had to make tradeoffs -- like including less memory -- to bring down the price, and that wasn't something it was willing to do.

"We didn't necessarily attain the price point that we hoped to attain," Abary said. "It's not an issue on Microsoft's side. It's more an issue of how the product was built and some of the tradeoffs we had to incorporate in it."

Check out CNET's in-depth report on how Microsoft became a control freak with tablet makers.

The comments from Abary come only a few days after Microsoft CEO Steve Ballmer joined Qualcomm Chief Executive Paul Jacobs onstage during his keynote address at the Consumer Electronics Show in Las Vegas. The two talked up their partnership on Windows RT devices and touted the devices from Dell and Samsung.

"The new Windows PCs, tablets, and phones, I think are stunning," Ballmer said. "Windows RT devices are the new addition to the family."

Samsung's move to hold off on Windows RT, at least in the U.S., raises concerns about the operating system and deals a blow to Microsoft's efforts to gain a bigger footprint in mobile devices. Samsung is one of the world's top provider of smartphones and tablets, and while it's relatively new to the U.S. PC market, those operations have been experiencing double-digit sales growth on a percentage basis. That means Samsung is a key partner for any software maker to have.

Qualcomm CEO Paul Jacobs is joined on stage at CES 2013 by Microsoft CEO Steve Ballmer.

(Credit:
James Martin/CNET)

While Samsung isn't releasing the initial product it developed with Qualcomm in the U.S., Abary said the company may consider Windows RT devices in the future.

"We want to see how the market develops for RT," Abary said. "It's not something we're shelving permanently. It's still a viable option for us in the future, but now might not be the right time."

We've contacted Microsoft and will update the report when we hear back.

Meanwhile, Rob Chandhok, president of the Qualcomm's Internet services division, told CNET today at
CES that while the company cares that Samsung won't be launching its product in the U.S., "there are a bunch of devices in the pipeline."

"These first rounds of devices are going to be followed by other rounds of devices," he said.

Microsoft has tightly controlled the development process for Windows RT devices, limiting the number of companies the chipmakers could work with, in order to make better products. That's meant that few products have hit the market, and some companies in the initial development program ultimately decided to abandon Windows RT.

Even before Microsoft's Surface RT tablet hit the market, Hewlett-Packard said in June that it had scuttled its immediate plans for a Windows RT device after receiving feedback from customers that they preferred Intel-powered tablets for business use. And Toshiba in August said it canceled its initial RT products because of development problems that would have delayed launch. The company believed its devices would be handicapped if they weren't introduced with the first wave of Windows RT products.

Samsung unveiled its Windows RT device at IFA in August. However, around the time Windows 8 and RT launched in October, it said it was still trying to formulate its strategy for Windows RT.

Meanwhile, Abary said Samsung saw "exponential" growth in its tablet business in the fourth quarter, with seven-inch devices experiencing the strongest demand.

"We saw significant growth in every category," Abary said. "There's now way we could keep up with all the demand."

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Google and Twitter Help Track Influenza Outbreaks

This flu season could be the longest and worst in years. So far 18 children have died from flu-related symptoms, and 2,257 people have been hospitalized.

Yesterday Boston Mayor Thomas Menino declared a citywide public health emergency, with roughly 700 confirmed flu cases—ten times the number the city saw last year.

"It arrived five weeks early, and it's shaping up to be a pretty bad flu season," said Lyn Finelli, who heads the Influenza Outbreak Response Team at the Centers for Disease Control and Prevention (CDC).

Boston isn't alone. According to the CDC, 41 states have reported widespread influenza activity, and in the last week of 2012, 5.6 percent of doctor's office visits across the country were for influenza-like illnesses. The severity likely stems from this year's predominant virus: H3N2, a strain known to severely affect children and the elderly. Finelli notes that the 2003-2004 flu season, also dominated by H3N2, produced similar numbers. (See "Are You Prepped? The Influenza Roundup.")

In tracking the flu, physicians and public health officials have a host of new surveillance tools at their disposal thanks to crowdsourcing and social media. Such tools let them get a sense of the flu's reach in real time rather than wait weeks for doctor's offices and state health departments to report in.

Pulling data from online sources "is no different than getting information on over-the-counter medication or thermometer purchases [to track against an outbreak]," said Philip Polgreen, an epidemiologist at the University of Iowa.

The most successful of these endeavors, Google Flu Trends, analyzes flu-related Internet search terms like "flu symptoms" or "flu medication" to estimate flu activity in different areas. It tracks flu outbreaks globally.

Another tool, HealthMap, which is sponsored by Boston Children's Hospital, mines online news reports to track outbreaks in real time. Sickweather draws from posts on Twitter and Facebook that mention the flu for its data.

People can be flu-hunters themselves with Flu Near You, a project that asks people to report their symptoms once a week. So far more than 38,000 people have signed up for this crowdsourced virus tracker. And of course, there's an app for that.

Both Finelli, a Flu Near You user, and Polgreen find the new tools exciting but agree that they have limits. "It's not as if we can replace traditional surveillance. It's really just a supplement, but it's timely," said Polgreen.

When people have timely warning that there's flu in the community, they can get vaccinated, and hospitals can plan ahead. According to a 2012 study in Clinical Infectious Diseases, Google Flu Trends has shown promise predicting emergency room flu traffic. Some researchers are even using a combination of the web database and weather data to predict when outbreaks will peak.

As for the current flu season, it's still impossible to predict week-to-week peaks and troughs. "We expect that it will last a few more weeks, but we can never tell how bad it's going to get," said Finelli.

Hospitals are already taking precautionary measures. One Pennsylvania hospital erected a separate emergency room tent for additional flu patients. This week, several Illinois hospitals went on "bypass," alerting local first responders that they're at capacity—due to an uptick in both flu and non-flu cases—so that patients will be taken to alternative facilities, if possible.

In the meantime, the CDC advises vaccination, first and foremost. On the bright side, the flu vaccine being used this year is a good match for the H3N2 strain. Though Finelli cautions, "Sometimes drifted strains pop up toward the end of the season."

It looks like there won't be shortages of seasonal flu vaccine like there have been in past years. HealthMap sports a Flu Vaccine Finder to make it a snap to find a dose nearby. And if the flu-shot line at the neighborhood pharmacy seems overwhelming, more health departments and clinics are offering drive-through options.

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Judge: Holmes Can Face Trial for Aurora Shooting

Jan 10, 2013 8:45pm

(Arapahoe County Sheriff/AP Photo)

In a ruling that comes as little surprise, the judge overseeing the Aurora, Colo., theater massacre has ordered that there is enough evidence against James Holmes to proceed to a trial.

In an order posted late Thursday, Judge William Sylvester wrote that “the People have carried their burden of proof and have established that there is probable cause to believe that Defendant committed the crimes charged.”

The ruling came after a three-day preliminary hearing this week that revealed new details about how Holmes allegedly planned for and carried out the movie theater shooting, including how investigators say he amassed an arsenal of guns and ammunition, how he booby-trapped his apartment to explode, and his bizarre behavior after his arrest.

PHOTOS: Colorado ‘Dark Knight Rises’ Theater Shooting

Holmes is charged with 166 counts, including murder, attempted murder and other charges related to the July 20 shooting that left 12 people dead and 58 wounded by gunfire. An additional 12 people suffered non-gunshot injuries.

One of the next legal steps is an arraignment, at which Holmes will enter a plea. The arraignment was originally expected to take place Friday morning.

Judge Sylvester indicated through a court spokesman that he would allow television and still cameras into the courtroom, providing the outside world the first images of Holmes since a July 23 hearing. Plans for cameras in court, however, were put on hold Thursday afternoon.

“The defense has notified the district attorney that it is not prepared to proceed to arraignment in this case by Friday,” wrote public defenders Daniel King, Tamara Brady and Kristen Nelson Thursday afternoon in a document objecting to cameras in court.

A hearing in the case will still take place Friday morning. In his order, Judge Sylvester said it should technically be considered an arraignment, but noted the defense has requested a continuance.  Legal experts expect the judge will grant the continuance, delaying the arraignment and keeping cameras out of court for now.

Sylvester also ordered that Holmes be held without bail.

Holmes’ attorneys have said in court that the former University of Colorado neuroscience student is mentally ill. The district attorney overseeing the case has not yet announced whether Holmes, now 25, can face the death penalty.

SHOWS: World News

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Hints of new dark force seen in galactic smash-ups

Colliding clusters of galaxies may hold clues to a mysterious dark force at work in the universe. This force would act only on invisible dark matter, the enigmatic stuff that makes up 86 per cent of the mass in the universe.

Dark matter famously refuses to interact with ordinary matter except via gravity, so theorists had assumed that its particles would be just as aloof with each other. But new observations suggest that dark matter interacts significantly with itself, while leaving regular matter out of the conversation.

"There could be a whole class of dark particles that don't interact with normal matter but do interact with themselves," says James Bullock of the University of California, Irvine. "Dark matter could be doing all sorts of interesting things, and we'd never know."

Some of the best evidence for dark matter's existence came from the Bullet cluster, a smash-up in which a small galaxy cluster plunged through a larger one about 100 million years ago. Separated by hundreds of light years, the individual galaxies sailed right past each other, and the two clusters parted ways. But intergalactic gas collided and pooled on the trailing ends of each cluster.

Mass maps of the Bullet cluster showed that dark matter stayed in line with the galaxies instead of pooling with the gas, proving that it can separate from ordinary matter. This also hinted that dark matter wasn't interacting with itself, and was affected by gravity alone.

Musket shot

Last year William Dawson of the University of California, Davis and colleagues found an older set of clusters seen about 700 million years after their collision. Nicknamed the Musket Ball cluster, this smash-up told a different tale. When Dawson's team analysed the concentration of matter in the Musket Ball, they found that galaxies are separated from dark matter by about 19,000 light years.

"The galaxies outrun the dark matter. That's what creates the offset," Dawson said. "This is fitting that picture of self-interacting dark matter." If dark matter particles do interact, perhaps via a dark force, they would slow down like the gas.

This new picture could solve some outstanding mysteries in cosmology, Dawson said this week during a meeting of the American Astronomical Society in Long Beach, California. Non-interacting dark matter should sink to the cores of star clusters and dwarf galaxies, but observations show that it is more evenly distributed. If it interacts with itself, it could puff up and spread outward like a gas.

So why doesn't the Bullet cluster show the same separation between dark matter and galaxies? Dawson thinks it's a question of age – dark matter in the younger Bullet simply hasn't had time to separate.

New window

The idea complements a previous study that saw evidence for dark forces at work in the Bullet cluster. In 2007 Glennys Farrar of New York University and colleagues said that the smaller cluster was moving too fast for gravity alone to be responsible. They suggested that some mysterious force related to dark matter might be hurrying it along.

Still, two clusters is not a lot to go on. Dawson, Bullock and colleagues are following up with about 20 more galactic collisions to see if they show any unusual behaviours. "I really think that we're almost to the point where we have enough observational data in hand," Dawson said. "We could close the book on self-interacting dark matter."

If the new force does exist, we might soon be able to see its effects on things influenced by dark matter, such as the behavior of black holes or the masses of the first stars, says Douglas Finkbeiner of Harvard University in Cambridge, Massachusetts, who was not involved in the new study.

"The simple thing isn't always the right thing, so I really appreciate that Will is trying to look into these other possibilities," he says.

Louis Strigari of Stanford University in California agrees. "Self-interacting dark matter is worth pursuing because we're still very ignorant," he said. "We're desperate to understand what dark matter is, so any new window is welcome."

If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.

All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.

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NEL service delayed due to power fault

SINGAPORE: Train services in both directions on the North East Line (NEL) are delayed due to a power fault.

Train operator SBS Transit alerted commuters at 10:18am on Twitter of a delay of 15 minutes.

It said free bus rides are available at designated bus stops.

SBS Transit first alerted commuters via SMS at about 10am, saying there had been a delay of 15 minutes due to a power fault.

It said at about 10:30am that shuttle services were activated at designated bus stops to provide free bus rides.

- CNA/ck

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