4 | NewScientist | 14 January 2012

WE MAY not know what dark matter is, but we can still put it to work. The largest map of dark matter ever made is one of several new ones that are helping to nail the properties of the equally mysterious dark energy, which drives the universe’s expansion.

A group led by Catherine Heymans of the University of Edinburgh, UK, presented the huge map at the American Astronomical Society (AAS) meeting in Austin, Texas, this week. Dark matter makes up 83 per cent of the universe’s matter, but is invisible, so its presence must be inferred from its gravitational influence.

This works because clumps of

dark matter distort the space-time around them. Light from distant galaxies passing through those regions also gets warped, making the galaxies appear streaked and

Dark mappers smeared in telescope images. Heymans’s team used the

Canada-France-Hawaii Telescope to observe 10 million galaxies and build a map of dark matter spanning 10 billion light years. Meanwhile Melanie Simet at the University of Chicago and colleagues reported at the AAS meeting how they used a similar technique to create a dark matter map that included the absolute distance to the galaxy clusters.

As the features in these maps are shaped by dark energy, they can be used to illuminate its properties too.

Sudoku is solvedSUDOKU’S fiendishness has been tamed. We now know the minimum starting numbers, or clues, needed in a Sudoku puzzle grid for it to have only one solution.

The fewer clues there are in the 9 by 9 starting grid of a puzzle, the harder it is to complete, as there are more squares to fill. But too few clues, and the puzzle no longer has a unique solution. To understand why this is, imagine the extreme – a starting grid with just a single square filled in. This could clearly correspond

to many different answers. To find the minimum number

of starting clues required, a team lead by Gary McGuire at University College Dublin, Ireland, turned to software that checks a completed Sudoku grid, looking for alternative puzzles buried within it. Nearly 50,000 single-solution 17-clue puzzles had already been found, so the researchers focused on finding a 16-clue one. It took the whole of 2011 to test all possibilities, and the team found none with a unique solution. This implies the minimum must be 17.

I’ll drink to thatTOAST your health by not drinking alcohol for two days a week, says a report by British MPs.

“The evidence we received suggests that people should be advised to take at least two drink-free days a week,” said Andrew Miller, chairman of the cross-party House of Commons Science and Technology Committee.

The booze break gives the liver a chance to regenerate, advice echoed in the US by the National

–Wishbones of contention–

–Take a break–

If it ain’t sick, don’t cure itPREVENTION is not always better than cure. The US Food and Drug Administration has finally moved to restrict the farmyard use of antibiotics to prevent livestock illness over concerns that they may generate antibiotic-resistant superbugs. But the announcement covers such a small subset of drugs that campaigners fear the superbug threat will remain.

The FDA’s apparently encouraging announcement last week will lead to severe restrictions on the farmyard use of cephalosporin antibiotics. But campaigners claim that these antibiotics account for only 0.2 per cent of antibiotic use on farms, and have accused the FDA of quietly withdrawing proposals dating from 1977 to tackle the wider use of tetracycline and penicillin antibiotics.

“Numerous organisations have recognised that use of antibiotics in agriculture poses risks to human health,” says Avinash Kar, a San Francisco-based lawyer with the Natural Resources Defense Council, which initiated legal action last year to try to force the FDA to phase out the growth promoters. Europe did so a decade ago. “The cephalosporin announcement is a small step in the right direction, but it’s very far from the finishing line.”

The FDA says it revoked the 1977 proposals to focus on voluntary reforms within the industry. “Our action should not be interpreted as a sign that the FDA no longer has safety concerns about the use of medically important antibiotics in [livestock],” said an FDA spokeswoman.

“The largest map of dark matter ever made is also helping to nail the properties of dark energy”

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Institute on Alcohol Abuse and Alcoholism. The UK government’s current recommendations imply that people can safely drink every day if they remain within recommended limits.

Nick Sheron, a liver specialist at the University of Southampton, UK, supports the idea of giving the liver a weekly break, but says an annual “liver holiday” of four to six weeks is more likely to heal liver damage. He says the benefit of a weekly break is more psychological because it proves to people that they can regularly manage without alcohol, and avoids escalation of intake.

MMR-scare lawsuit ANDREW WAKEFIELD, the doctor who proposed the long-discredited link between autism and the measles, mumps and rubella (MMR) vaccine is to sue for damages following accusations that his research was fraudulent.

Wakefield’s MMR-autism claims were undermined in 2010 when The Lancet retracted his original study. He was banned from practising as a doctor by the UK General Medical Council.

Wakefield is now suing journalist Brian Deer for articles he wrote in the BMJ last year claiming that Wakefield manipulated and falsified data and diagnoses. He is also suing the journal’s editor, the journal itself and its publishers.

Wakefield’s suit challenges Deer’s allegations that in some children, symptoms of autism began before they had their MMR shots. It also states that allegations that three of nine children reported as having regressive autism didn’t actually have autism, are false.

Finally, the suit challenges statements by Deer in interviews, in which the journalist accused Wakefield of embarking on a “campaign of lies” and of trying to “work out a nice little living… at the expense of autistic children”.

Carry on frackingTHERE’S no reason to stop. Two of the objections to “fracking” for shale gas have been blown out of proportion, say British geologists.

Hydraulic fracturing involves pumping water, chemicals and sand into shale deposits 2 kilometres underground to release natural gas. It has been accused of contaminating water and causing minor earthquakes.

“We think the risk is pretty low,” said Mike Stephenson of the British Geological Survey on Tuesday. Research on contamination is scarce but what

little there is suggests fracking is not to blame. There is little reason to believe gas liberated 2 kilometres down could work its way into water deposits that are less than 50 metres deep. Likewise for the chemicals. Fracking does cause

minor quakes but they are comparable to those caused by coal mining, and originate much deeper so have all but dissipated by the time they reach the surface.

“There is little reason to believe gas liberated 2 kilometres down can get into water deposits”

$380 billion. That’s how much natural disasters cost the global economy in 2011, making it the costliest year on record. The toll was driven by the earthquakes that struck New Zealand in February and Japan in March.

Munich Re, one of the world’s biggest reinsurance companies, has compiled data on the cost of natural disasters since 1980. It shows that the Japanese quake was the costliest disaster of all time, with losses of $210 billion – not including the nuclear incident at Fukushima.

More broadly, the figures reveal a clear rise in the financial losses associated with natural disasters over the past 30 years (see graph).

The number of earthquakes has remained stable since 1980 but their economic cost is rising – a reminder that quake risk should be recognised by town planners, say Munich Re.

In contrast, the number of weather-related events like floods and drought is rising. Evidence suggests this is linked to climate change, particularly in the case of extreme temperatures and rainfall, says Peter Stott of the UK Met Office in Exeter.

The cost of extreme temperatures, fires and droughts has remained stable, the Munich Re findings show, but floods and storms cost us more today than they did 30 years ago.

Spiralling cost of natural disaster

60 SeCondS

Life in the deepThe deepest hydrothermal vents yet found have been discovered in a rift in the Caribbean seafloor. At a depth of 5000 metres, they are 800 metres deeper than any vents found so far. They are home to a new species of shrimp (Nature Communications, DOI: 10.1038/ncomms1636).

Probe’s downfallAs New Scientist went to press, Russia’s hobbled Phobos-Grunt Mars probe – marooned in Earth orbit since November – looked destined to fall back to Earth on 15 January. Where was not clear but fragments totalling 200 kilograms could survive to reach the surface. Mission controllers think the craft’s toxic fuels will burn up safely since they are contained in easily melted aluminium tanks.

Patchy memoryAdults aged 76 on average with mild cognitive impairment performed better on memory tests after wearing nicotine patches for six months. Such patches can have side effects, says Paul Newman at Vanderbilt University in Nashville, Tennessee, so should only be used for cognitive purposes with medical supervision (Neurology, DOI: 10.1212/WNL.0b013e31823efcbb).

Baby’s wake-up callHearing a baby cry makes adults more alert than hearing distressed grown-ups. Forty volunteers playing a fast-reaction game called “Whack- a-mole” scored highest on the game if they had heard babies crying beforehand (Acta Paediatrica, DOI: 10.1111/j.1651-2227.2011.02554.x).

Quake acceleratorA Japanese particle accelerator damaged in the March 2011 earthquake is set to resume operation after extensive repairs. The accelerator, part of the Japan Proton Accelerator Research Complex in Tokai, is used to generate neutrinos and might one day probe faster-than-light physics.

For daily news stories, visit newscientist.com/news

Natural disasters are more frequent than 30 years ago – and are costing us more

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