Today on New Scientist: 11 January 2013

Largest structure challenges Einstein's smooth cosmos

One-twentieth the diameter of the observable universe, a group of galaxies dents the cherished idea that the cosmos is uniform at large scales

Straitjacket drug halts herpes virus's escape stunt

Herpes infections recur as the virus is adept at evading our defences, but a new drug that suppresses enzymes exploited by the virus seems effective

Zoologger: Mouse eats scorpions and howls at the moon

Super-aggressive grasshopper mice are not put off by the deadly venom of the scorpions they feast on - in fact, nothing much seems to scare them

Sand tsunami pictured striking Australian coast

The spectacular wall of sand and dust appears to block out the sun like a giant wave

Astrophile: Zombie stars feed on Earth-like exoplanets

We can now learn what planets around other stars are made of - by looking at the atmospheres of white dwarfs that have swallowed up their worlds

Life will find a way, even in the midst of a hurricane

Not for the faint-hearted: to sample the microbiome of a hurricane, fly a jetliner through it

Physics not biology may be key to beating cancer

Billions of dollars spent on cancer research have yielded no great breakthrough yet. There are other ways to attack the problem, says physicist Paul Davies

Feedback: Return of nominative determinism

The last nominative determinism stories, salads of gizzards and his chestnuts, Australian graduates in outer space, and more

A comeback for virtual reality? Inside the Oculus Rift

The Oculus Rift promises an immersive gaming experience like no other. Niall Firth gets his head in the game and gives it a try

Is the US facing Flu-maggedon?

The US flu season has come early this winter, leaving many hospitals overwhelmed. But is the situation really any worse than usual?

Your body's insights into life and cosmos

The Universe Within by Neil Shubin tells stories from your body about our species, planet and universe. PLUS: a cautionary tale of inspirational scientists

Hands on with Leap Motion's gestural interface

The makers of the ultra-precise gestural interface talk big about killing off the mouse. But it looks like more than just bluster

Personal assistant for your emails streamlines your life

GmailValet aims to use crowdsourcing to give everyone a personal assistant to help deal with their emails - it could cost as little as $2 a day

DNA 'identichip' gives a detailed picture of a suspect

A new microchip-based DNA tester can identify multiple traits of an individual at a time, even where their DNA is scarce

Most fundamental clock ever could redefine kilogram

Physicists have created the first clock with a tick that depends on the hyper-regular frequency of matter itself

Nanomachine mimics nature's protein factory

An artificial ribosome that assembles proteins and peptides could make it much easier to manufacture antibiotics and exotic new materials

Muscle mimic pulls electricity from wet surface

A plastic film that repeatedly curls up and flips over when wet could power devices in remote areas or sensors embedded in sweaty clothing

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Basketball: Lakers' Bryant and wife Vanessa reconcile

LOS ANGELES: Los Angeles Lakers superstar Kobe Bryant and his wife, Vanessa, confirmed they have reconciled in posts on social media.

Vanessa Bryant, who had filed for divorce from the NBA star in December of 2011, posted a message on Instagram, and Bryant said on his Facebook page that the couple were back together.

"We are pleased to announce that we have reconciled," Vanessa Bryant wrote. "Our divorce action will be dismissed. We are looking forward to our future together. Kobe & Vanessa."

"I am happy to say that Vanessa and I are moving on with our lives together as a family," Bryant posted on Facebook. "When the show ends and the music stops, the journey is made beautiful by having that someone to share it with.

"Thank you all for your support and prayers!" Bryant added.

The Bryants married in 2000. Vanessa stood by her husband after he was charged with sexually assaulting a Colorado woman in 2003, charges that were eventually dropped.

Vanessa Bryant filed papers in Orange County Superior Court in Santa Ana, California, in December of 2011 citing "irreconcilable differences" as the reason for seeking a divorce.

However, the two continued to work together for various charitable causes and the celebrity website TMZ reported last June that they were working towards a reconciliation.

They have two daughters, nine-year-old Natalia and six-year-old Gianna.

- AFP/al

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Cameras not entirely out of the picture at CES 2013

The update to the Fujifilm X100, the X100S, was one of the few bright spots in camera announcements.

(Credit:
Sarah Tew/CNET)

LAS VEGAS--It's been an exceptionally busy and newsworthy past 12 months for cameras -- budget full-frame models, 4K action cameras and cinema cameras, full-frame compacts. Unfortunately for CES 2013, most of that happened at Photokina this past Fall. So while this show brought a few nice, potentially ownworthy updates to existing product lines, none of it really stands out as particularly whizzy.

In advanced cameras, the most common update has been to autofocus systems, with combo phase-detection/contrast AF starting to take over in camera lines that have traditionally had rather slow performance -- new models like the Fujifilm X100S and the Samsung NX300. The X100S has the most technologically innovative advancement, debuting a split-screen electronic viewfinder for improved manual focus control. We had a chance to try it and even though we were never fond of that type of viewfinder on film SLRs, it works well in an EVF (because the viewfinder is brighter than on, say, a cheap SLR).

Perhaps the most notable, though notably good or bad we've yet to decide, is Polaroid's entry into the interchangeable-lens camera market with cheap Micro Four Thirds and Nikon CX-size sensors and mounts. The camera's are extremely plasticky and the sensors are built into the lens, but the company will have adapters for other mounts with built-in sensors. We're really curious about the photo quality.

The Olympus Stylus Tough TG-2 iHS, announced at CES 2013, should be a very good camera because it's basically the same as its predecessor.

(Credit:
Joshua Goldman/CNET)

As far as point-and-shoots go,
CES 2013 was a fairly weak show with just one or two interesting cameras launched from each manufacturer. And by interesting we mean that they were mostly refreshes of previously existing cameras with some feature tweaks. Again, that's more an indication of CES' importance as a show for cameras than it is for the state of the category. However, the cameras announced do show where the market is going.

For example, Olympus announced the Stylus Tough TG-2 iHS, an update to itstop-of-the-line rugged compact. It picks up exactly where its predecessor left off, but it can now go 10 feet deeper underwater (up to 50 feet), and it now has aperture priority and enhanced macro modes.

Similarly, Samsung rolled out its second-generation of Smart Cameras loaded with Wi-Fi for fast sharing and backup. But while some of the wireless features are new, such as an option to send every photo directly to a smartphone or
tablet as they're taken, the cameras themselves weren't remarkably different than last year's models. Likewise, Nikon announced the Coolpix S6500, which is basically just a Wi-Fi-enabled version of the Coolpix S6400.

Sony announced nothing but its entry Cyber-shots at CES 2013.

(Credit:
Lori Grunin/CNET)

Sony stuck to entry-level models, though at least it included its entry model with a Sony Exmor R BSI CMOS sensor, the Cyber-shot DSC-WX80, so there's at least some idea of the new features coming to other models this year.

Even Fujifilm backed off on new FinePix models, keeping its typical double-digit list of CES cameras to seven. This included two of the shows point-and-shoot highlights, the hobbyist-targeted HS50EXR and the ultrasupermegazoom SL1000.

Another highlight -- and the only entirely new model announced -- was Canon's PowerShot N. The tiny square camera has a flip-up 2.8-inch touch screen and an 8x wide-angle zoom lens, and does away with a shutter release button and zoom lever, using rings around the lens instead.

The PowerShot N introduces a new Creative Shot mode, too, which will automatically create five different versions of a single shot using different color modes, crops, and styles in addition to saving the original photo. It's an unique option and the camera we tried did the edits fast, so maybe Canon has something here. At least with the mode, I'm not sure about the camera.

So for point-and-shoots this year, it looks like it's just going to be long zooms and rugged cameras from here on out, with a few exceptions like the PowerShot N.

As for camcorders, Sony made the most interesting updates to its lineup, though that's not saying much. And while most manufacturers have cut back on the number of models announced for 2013, Sony still blanketed us with 10 versions.

The POV action camcorder market grew by at least three more as well with two good-looking new models from iON, the Air Pro 2 and Adventure, and the HX-100D from Panasonic, which kind of misses the point of the small action cam market.

Perhaps more interesting was the growing number of accessories for turning an iPhone into more of a point-and-shoot camera, such as the Kickstarter project Snappgrip (available for Galaxy S3, too), Will.i.am's pricey foto.sosho cases, and Olloclip's upcoming case/lens combo.

In the end, CES 2013 wasn't so much a bust for the category, just that it's still not the place camera manufacturers are making huge announcements. But, with CP+ in Japan just weeks away, maybe we'll get some real treats then.

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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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At CES, two HP laptops do Windows 8 right

HP Spectre XT TouchSmart ultrabook makes Windows 8 a pleasure to use.

(Credit:
Brooke Crothers)

LAS VEGAS--At CES this week, Hewlett-Packard hardware got my attention.

Though the company has been savaged in the media because of dubious acquisition decisions and a falling stock price, its brief exhibition of new
Windows 8 laptops and hybrids at
CES was impressive.

I'll focus on two, the EliteBook Revolve and Spectre XT TouchSmart ultrabook-- both touch-capable Windows 8 laptops. The systems were fleetingly exhibited at CES by HP during an event at the MGM Grand event on Monday night.

I'll start with the Spectre XT TouchSmart because it was also at Intel's CES booth all week -- and available for any attendee to use. For me, it was my go-to laptop when I needed to escape the 11.6-inch screen constraints of my
MacBook Air.

HP calls it an ultrabook, but by ultrabook standards it's palatial, sporting a large 15.6-inch 1,920x1,080 resolution display. Other salient specs include an Intel Core i7-3517U 1.9GHz processor, 8GB DDR3 1600 MHz memory, and a 500 GB HDD with a 32GB solid-state drive cache.

The display is gorgeous -- and made it really hard for me to go back to the Air's cramped 1,366x768 display. The Spectre XT's 1,920x1080 resolution is perfect for a 15-inch class display running Window 8. Windows 8 fonts look smooth, well-resolved but not so small that you can't see them.

And speaking of Windows 8. I've tried my share of Windows 8 touch-screen laptops and this is hands-down the best experience I've had: fluid, fast, fun. No lag here.

And one final thought: though it weighs just under five pounds, I found the weight distribution excellent. That is, it feels lighter than a traditional, thick 5-pound laptop.

HP's 3-pound, 11.6-inch EliteBook Revolve seemed well-built, well-conceived and comes packed with impressive features, like a touch screen, integrated 4G connectivity, and Intel's Ivy Bridge processors.

I spent considerably less time with the EliteBook Revolve but walked away feeling it had a lot potential (it won't ship until March). In fact, if I was to design a Windows 8 road-warrior laptop, it would be pretty much what HP has delivered.

The Revolve is a convertible. That is, it has a touch display that rotates but doesn't detach from the base. But what I like about it is the practicality: it's only a little heavier than my Air but has a touch display and the option for built-in 4G.

I can't overstate the importance of integrated 4G. With my Air, it's more-often-than-not a hassle to connect to my Verizon Mi-Fi or my iPhone 5's hotspot. I'm not going to go into all of the reasons why it's a hassle here but suffice to say it would be nice to have 4G built into the MBA. If Apple can provide an iPad 4 with 4G, why not an 11.6-inch MacBook Air?

But getting back to the Revolve. The other big draw for me is the option for an HP docking station, allowing you to pop the laptop into a dock and instantly connect to all the ports of a typical desktop PC.

If HP can deliver consistent quality on these two laptops, I would say there's still plenty of hope for the world's largest PC company.

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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.

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