New Scientist

EDITORIAL

Should donated sperm be just another product?

A sperm bank is being sued on the premise that sperm can be guaranteed like anything else

So will Donovan vs Idant Laboratories open the floodgates? It seems unlikely. New York’s product liability laws are highly unusual in that they consider donor sperm to be a product just like any other. Most other US states grant special status to blood products and body parts, including sperm. In these states, donor sperm is not considered a “product” in the usual sense, despite the fact that it is tested, processed, packaged, catalogued, marketed and sold. Similarly, European Union product liability law could not be used in this way.

Even if this lawsuit is an isolated case, it still raises some difficult questions. First,

BRITTANY DONOVAN was born 13 years ago in Pennsylvania. Her biological father was sperm donor G738. Unbeknownst to Brittany’s mother, G738 carried a genetic defect known as fragile X – a mutation that all female children “Nobody would deny that sperm with fragile X should be screened out, but born from his sperm will inherit, and which what about more subtle defects?” causes mental impairment, behavioural problems and atypical social development.

Last week, Brittany was given the green light to what lengths should sperm banks go to to sue the sperm bank, Idant Laboratories of ensure they are supplying defect-free sperm?

New York, under the state’s product liability As we learn more and more about human laws (see page 4). These laws were designed to genetics, there is a growing list of tests that allow consumers to seek compensation from could be performed. Nobody would deny that companies whose products are defective and donor sperm carrying the fragile X mutation cause harm. Nobody expected them to be should be screened out – and there is a test applied to donor sperm. that can do so – but what about more subtle Thousands of people in the US have defects, such as language impairment or a purchased sperm from sperm banks on the susceptibility to early Alzheimer’s? promise that the donor’s history has been Donovan vs Idant Laboratories also serves carefully scrutinised and his sample rigorously as a reminder of the nature of the trade in tested, only for some of them to discover human gametes. Sperm bank catalogues that they have been sold a batch of bad seed. can give the impression that babies are as Some parents learn about genetic anomalies guaranteed as dishwashers. The Donovans after their disabled child is born and they are entitled to their day in court, but in press the sperm bank for more information. allowing the product liability laws to be used Others realise when they contact biological in this way, the legal system is not doing much half-siblings who have the same disorder. to dispel that notion. ■

We mustn’t succumb to climate fatigue THE news on climate change continues to get grimmer. Till now, the official estimates of sea level rise have not included any contribution from the melting of Antarctic ice. It is becoming horribly clear that this is a serious omission.

As we report first-hand from Antarctica on page 34, there are signs that the West Antarctic ice sheet is more vulnerable to climate change than we thought.

It is difficult to translate the findings into a prediction of what will happen over the next century, but a melting Antarctic can only add to the rises in sea level already predicted.

With nothing but bad news around, the message that we need to do something quickly may seem boringly predictable – but that would be the worst possible excuse for ignoring the problem. ■

Watch the watchers THOSE who feel their privacy is being invaded

by CCTV may feel a twinge of sympathy – or perhaps Schadenfreude – for the CCTV operators themselves. There is now a CCTV camera that monitors people who are employed to watch CCTV footage, just to make sure they are doing their job properly.

This, though, raises the question of who is monitoring this extra footage, and how we can be sure they are being vigilant enough.

Clearly what we need is CCTV that watches the CCTV that watches the CCTV… ■

What’s hot on NewScientist.com WILDLIFE International garden photographer of the year See beautiful shots from the finalists, including a close-up of a tiger moth, the sharp spines of an agave, and a butterfly caught in a rain shower...

SPACE CSI: Red Planet? In what is planned to be the first DNA analysis to be done on another planet, Harvard researchers hope to send a DNA sequencer to Mars in the next decade to hunt for signs of alien life.

SOCIETY More scientists who put their lives on the line Our recent article on researchers who became their own test subjects obviously piqued people’s imagination – we had a flood of responses naming others who took their science well beyond the realms of personal safety.

ENVIRONMENT Bug eats electricity, farts biogas Wind and solar energy output is variable and doesn’t match peak demand. Feeding

extra electricity to a microorganism that uses the energy to convert carbon dioxide into methane offers a carbon-neutral way to turn the surplus power into a valuable fuel.

COSMOLOGY What would it look like to fall into a black hole? Plunging into a black hole might not be good for your health, but at least the view would be spectacular. A new simulation not only shows what you might see on your way towards the black hole’s

crushing central singularity – it could also help physicists understand the apparently paradoxical fate of matter and energy in a black hole.

BLOG Make the world a better place by uninventing something If you had a time machine and could visit the past to extinguish a technology before it caught on, which invention would you get rid of?

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11 April 2009 | NewScientist | 3

SUSUMU NISHINAGA/SPL

UPFRONT

Sued over ‘unsafe’ sperm SPERM should be subject to the same product liability laws as car brakes, according to a US judge who has given a teenager with severe learning disabilities the go-ahead to sue the sperm bank that provided her with a biological father.

Brittany Donovan, now 13 years old, was born with fragile X syndrome, a genetic disorder causing mental impairment and carried on the X chromosome. She is now suing the sperm bank, Idant Laboratories of New York, under a product liability law more commonly associated with manufacturing defects, such as faulty car brakes.

Donovan does not have to show that Idant was negligent, only that the sperm it provided was unsafe and caused injury. “It doesn’t matter how

much care was taken,” says Daniel Thistle, the lawyer representing Donovan, based in Philadelphia, Pennsylvania. Genetic tests have revealed that she inherited the disorder from her biological father.

Donovan was conceived in Pennsylvania, where a “blood shield law” protects sellers of human bodily material from product liability suits.

In New York state, however, sellers are not protected by any such law.

On 31 March, federal judge Thomas O’Neill ruled that Donovan’s case should be tried in New York.

Wendy Kramer of the Donor Sibling Registry, which helps people conceived through donor gametes find genetic relatives, suspects other sperm recipients may try to sue. “This could open the floodgates,” she says.

Ebola accident

have killed researchers in the past.

Whether the vaccine worked is still not clear. Although the woman remains healthy, it could be that she never developed an infection in the first place. It should be possible to discover the truth, as an infection would elicit antibodies to many more Ebola proteins than the vaccine alone.

However, Stephan Günther, head of virology at the institute, says its labs do not have the right tests to identify which antibodies the woman has, so the scientists hope to send samples to a US military lab that does.

–Would you buy this sperm sample?–

Mosquito killer

“Insecticides that take weeks to kill may be the only way to successfully wipe out malaria” slow-killing insecticides, which should still stop malaria transmission as mosquitoes can’t pass on the parasite until it has grown inside them for two weeks, 4 | NewScientist | 11 April 2009

NASA

INSECTICIDE resistance in malarial mosquitoes could be wiped out for good, paradoxically by using slow-killing agents.

The World Health Organization recommends fast-acting insecticides for malaria control.

But such agents stop mosquitoes from reproducing, giving any insect that resists them an enormous competitive advantage.

As this drives the evolution of resistance, Andrew Read at Pennsylvania State University in University Park decided to examine what happened if this selection pressure was removed by only killing elderly mosquitoes that had already laid eggs.

This could be achieved using

almost a lifetime to a mosquito.

Crucially, using a model, Read found that such an approach is “evolution proof”: mosquitoes never evolve resistance to slowacting insecticides because both resistant and susceptible insects have the same chance of laying eggs, removing the selection pressure favouring resistant mosquitoes (PLoS Biology, DOI: 10.1371/journal.pbio.1000058).

Some insecticides that take weeks to kill, such as insect-killing fungi, are already being studied.

Read believes these may be the only way to wipe out malaria.

DID an experimental vaccine save a scientist in Germany from Ebola? The lives of other scientists might depend on the answer.

On 12 March a researcher at the Bernhard Nocht Institute for Tropical Medicine in Hamburg accidentally stuck her finger with a needle carrying Ebola virus.

Worried colleagues gave her an experimental Ebola vaccine that had not previously been tested on people. It is being developed mainly to protect lab workers from just such mistakes, which

Space revamp RUSSIA is embarking on its most ambitious space project since the cold war, with plans for a new spaceship and launcher.

Until now, Russia has tweaked rather than upgraded spacecraft.

Soyuz is over 40 years old and on its fifth generation. Now the Russian space agency plans to replace all its launch facilities and rocket designs. “Post-Soviet Russia has never had a massive –Retirement looms for Soyuz– project of this kind,” says Aleksey

For daily news stories, visit www.NewScientist.com/news

60 SECONDS

Make airlines pay

Krasnov, head of the agency’s human space-flight programme.

The company that will build the spaceship has been given until June 2010 to design a 20-tonne reusable craft that can carry six people, twice the capacity of Soyuz. As well as ferrying crew to the International Space Station, it should be able to repair or retrieve satellites. A beefed-up version could reach lunar orbit and perhaps beyond.

The plans are similar to NASA’s Orion programme – earning it the nickname “Orionski” – and could provide back-up for the US spacecraft if needed.

to be signed in December. The move was announced at the close of 10 days of climate negotiations held in Bonn, Germany, this week.

The UN estimates air transport is reponsible for roughly 3 per cent of human greenhouse gas emissions

THEY may be an unlikely green lobby, but four of the world’s largest airline companies have called on governments to be stricter with them.

British Airways, Air France“Four of the world’s largest KLM, Cathay Pacific and Virgin airlines have called on Atlantic have joined forces with governments to be stricter the British Airports Authority with them” and The Climate Group, a policy consultancy, in a proposal for a global cap-and-trade scheme that worldwide. Without action, its share could rise to 15 per cent by would regulate airline emissions.

2050. Yet the industry is not yet They want their proposal to be required to reduce its emissions – included in the next global even under the Kyoto protocol. emissions agreement, scheduled

Obama undermined Collapse imperils Wilkins ice shelf

JIM ELLIOT/POLARIS/EYEVINE

THE US will “lead by example to BREAKING up is getting easier to do, it seems, especially when it comes reduce our carbon footprint”, to the Antarctic Peninsula. On President Barack Obama pledged 3 April, satellite images showed that at the G20 summit in London last week. But back in Washington, an ice bridge which connected two islands to the Wilkins ice shelf had the message from Congress was shattered. This has left the shelf “not so fast”. vulnerable to the ocean and in danger Obama’s plan to reduce US of breaking away from the peninsula. greenhouse gas emissions to Last year, the 13,000-square1990 levels by 2020 relies on a kilometre Wilkins ice shelf released cap-and-trade system, in which huge chunks of ice, leaving a narrow emitters will be charged for the ice bridge as the only connection carbon dioxide they put into between the northern front of the ice the air. The cash raised – tens shelf and the ice surrounding nearby of billions of dollars – will help Charcot and Latady islands. fund “green” jobs to revive the Now that ice bridge has collapsed – US economy by developing leaving an iceberg-filled channel in renewable energy and a smart its wake – the northern front of the grid to deliver that power. shelf is exposed. “We expect in the Last week, when Congress began considering the laws necessary for cap-and-trade, Democrats in coal-mining Midwestern states came out in opposition. “The odds are [the legislation] will slip to 2010,” says Eileen Claussen, president of the Pew Center on Global Climate Change in Arlington, Virginia.

In London, G20 leaders said they would leave a deal on a successor to the Kyoto protocol to December’s Copenhagen talks.

The big question now is what Obama will be able to offer.

Bill Clinton signed at Kyoto, but –Going, going…– Congress blocked the protocol.

next few days and weeks that the northern ice front will lose between 800 and 3700 square kilometres of ice,” says Angelika Humbert of the Institute of Geophysics at Münster University, Germany.

The break-up of the Wilkins ice shelf will not lead to sea-level rise as it is already floating on water, and nor will it speed up the movement of any glaciers into the oceans. Nevertheless, these events serve as a dire warning, says Humbert: “It shows us that ice shelves have the potential to become unstable on very short timescales.”

If other ice shelves in the region start calving, then the glaciers that feed them could slip faster into the ocean, leading to sea-level rise.

Quake foretold The worst earthquake to strike Italy in 30 years seems to have vindicated the controversial predictions of a seismologist. After recording anomalous radon gas emissions, Giampaolo Giuliani warned of a quake weeks before the magnitude 6.2 earthquake struck a region near Rome early on Monday, killing at least 90 people. After his warning, Giuliani was reported to the authorities for “spreading panic”.

Nigerian drug trial deal The drug company Pfizer is close to an out-of-court settlement with the Nigerian state of Kano, which claims that 11 children died after taking part in a trial of the meningitis drug Trovan. Pfizer says meningitis, not Trovan, killed the children. Nigeria’s federal government is also trying to sue Pfizer, although it may withdraw if Kano reaches a firm settlement.

Male pill hopes A male contraceptive drug could be a step closer thanks to the discovery of a gene that controls sperm movement. CATSPER1 allows sperm cells to burrow into the egg and fertilise it. Antibodies against the protein made by CATSPER1 could be used as a contraceptive (American Journal of Human Genetics, DOI: 10.1016/j.ajhg.2009.03.004).

Bonobo epidemic A deadly outbreak of what appears to be flu is threatening a group of endangered bonobos in a sanctuary in the Democratic Republic of the Congo. At least four of the 60 residents have died.

Old plastic, new prints Recycling may be good for the environment, but it is making life difficult for forensic scientists.

Chemists who have developed protocols for identifying fingerprints on different types of plastic surface say the increasing prevalence of recycled plastics is forcing them to rethink their methods.

11 April 2009 | NewScientist | 5

THIS WEEK

What’s happening to dark energy?

Blasts from the past sketch a picture of a universe whose runaway expansion may finally be slowing two teams of astronomers spotted distant supernova explosions that appeared dimmer than expected, and so further away. The find suggested the exploding stars were receding from Earth faster than anticipated, and therefore so was the rest of the universe. “Dark energy” was invoked to explain the apparent anomaly. Since then more supernovae have been catalogued to help build up a picture of how the universe has expanded over time.

The biggest set of supernova data was released earlier this year by the Harvard-Smithsonian

AFTER billions of years of runaway expansion, is the universe starting to slow down? A new analysis of nearby supernovae suggests space might not be expanding as quickly as it once was, a tantalising hint that the source of dark energy may be more exotic than we thought.

For more than a decade, astrophysicists have grappled with evidence of a baffling force that seems to be pushing the universe apart at an ever-increasing rate.

Exactly what constitutes the dark energy responsible for this cosmic speed-up is unknown, says Michael Turner at the University “The effect is slight, but if true it would change our of Chicago. “The simplest ideas about the source of question we can ask is ‘does the dark energy” dark energy change with time?’ ” So far, the evidence has suggested that dark energy is Center for Astrophysics in constant, though its effect on the Cambridge, Massachusetts. It universe has become stronger as includes data on 147 supernovae the universe has expanded and that exploded in the last billion the gravitational force between years, more than half of them objects weakens with distance. newly discovered (www.arxiv.org/ Now an analysis of supernovae abs/0901.4787). The Harvard team suggests dark energy may actually analysed the new supernovae be on the wane. In a paper on the assuming that dark energy has physics preprint website, a team remained unchanged. led by Arman Shafieloo at the Shafieloo, however, dropped University of Oxford examined the requirement that dark energy a newly released catalogue of be constant over the universe’s supernova explosions, including history. Together with Varun Sahni a number of relatively recent of the Inter-University Centre for blasts nearby (www.arxiv.org/ Astronomy and Astrophysics in abs/0903.5141). They found that Pune, India, and Alexei Starobinsky the new data made the best fit of the Landau Institute for with a universe in which dark Theoretical Physics in energy is losing strength. “It Chernogolovka, Russia, seems acceleration is slowing Shafieloo used an approach he down,” says Shafieloo. says is particularly sensitive to The first evidence of dark rapid changes in the universe’s energy emerged in 1998, when rate of expansion.

6 | NewScientist | 11 April 2009

SCIENCE SOURCE/SPL

Rachel Courtland

Beginning with factors like red shift – a measure of how much the expansion of space has stretched the light from each explosion – they calculated a representative number for the epoch in which each supernova occurred. After plotting all of these numbers, they found that the best fit was a scenario in which dark energy has weakened over the last 2 billion years, causing cosmic acceleration to slow down.

Shafieloo cautions that their result is preliminary, but adds that it could be time to begin revisiting other models of dark energy.

“Their approach is reasonable,”

though the effect is slight, says cosmologist Dragan Huterer of the University of Michigan, Ann Arbor. “If that is really the case it would be a tremendous discovery.”

Indeed, it would change our ideas about the source of dark energy. Until now, all signs have pointed to the cosmological constant as the simplest explanation for the accelerating expansion of the universe. This constant is an unchanging energy that arises from quantum fluctuations in the vacuum of space. “The cosmological constant is the only thing that makes any sense to particle physicists

In this section ■ Climate and diseases, page 8 ■ Praying is like talking to a friend, page 9 ■ Space storm early warnings, page 11

WE DON’T NEED THE STUFF Some theories claim to explain the universe’s accelerating expansion without resorting to dark energy.

One has it that cosmic acceleration is the result of the breakdown of general relativity in which space is forced apart at large scales. If that were the case, discrepancies should show up between measurements of the universe’s expansion and the number of galaxy clusters, which is used to gauge how easily the universe can grow large structures.

Such evidence has been lacking.

What’s more, most theories have a hard time explaining the acceleration of the cosmos without introducing other effects, such as instabilities that could preclude the existence of stars and galaxies. “None of the ideas make everything snap into place,” says Sean Carroll of Caltech.

or obscured by dust. Astronomers must correct for the dimming effect of dust and other subtleties in order to estimate a supernova’s true peak brightness. But the team may have overcompensated in this correction, producing a catalogue of nearby supernovae that are slightly too bright for their distance. That would create the illusion that the universe’s acceleration has been slowing.

New observations from other –Objects may appear faster than they are– groups need to be examined to look for the same effect, Kirshner right now,” says Huterer. says, though determining A more likely explanation for Yet if dark energy is changing, whether dark energy really is the team’s result is a slight bias in the cosmological constant could changing could take a while. The the new supernova data, Huterer not be the driver. Instead, it would says. Robert Kirshner, a member fine details of so many supernovae suggest far more exotic physics at of the Harvard team, agrees. have been recorded that the work. It might even mean dark so-called “systematic floor” has “I think these are serious people energy does not exist at all (see been hit – a scenario in which whose analysis should be taken “We don’t need the stuff”). One everything from subtle differences seriously, but there can be more example of an exotic origin is between supernova explosions to than one cause for the apparent “quintessence”, a theoretical the warp of a telescope mirror can effect,” he says. quantum field that permeates skew results, Huterer says.

For example, a potential bias space like the as-yet-unidentified Upcoming “precision projects” could have been introduced field thought to have driven like the Dark Energy Survey, which thanks to dimmer objects being inflation right after the big bang. will mount a supersensitive easier to see if they are nearby.

This field could be dissipating and It is possible that the Harvard 500-megapixel camera on a losing energy, eventually causing 4-metre telescope at the Cerro team happened to catalogue the universe to decelerate and Tololo Inter-American Observatory a disproportionate number of collapse back on itself. nearby supernovae that were faint in Chile, aim to reduce some of the

Another possibility is that matter is not uniformly distributed over large scales, and that the Earth is inside a vast bubble of space that is relatively devoid of matter. Gravity would have less pull in such a bubble, so it would expand rapidly. This expansion would affect light as it reached us from supernovae, meaning that they only appear to be moving away from us increasingly quickly, and that dark energy need not be invoked.

This scenario seems unlikely, says Alexei Starobinsky of the Landau Institute for Theoretical Physics in Chernogolovka, Russia. But the opposite – a smaller region with a slight excess of matter – could create a tug that would look like dark energy weakening of late. “That could explain this difference,” he says.

sources of uncertainty. One of the project’s aims is to measure some of the universe’s most recent history, by recording about 2000 supernovae that have exploded in the last billion years.

Other probes that will push the limit in sensitivity are still in early planning, including two space probes – the US’s Joint Dark Energy Mission and Europe’s Euclid.

Some astronomers suspect a partnership will be forged between these missions to send up a single international probe instead.

It is practically impossible to definitively discover if dark energy is constant. “There isn’t a target to shoot for,” says cosmologist Sean Carroll of Caltech. “As we narrow down the error bars and get closer and closer to perfectly constant, there’s no point at which you say ‘OK. We’re done. Dark energy is constant.’ ” However, the next burst of effort could reveal in glowing detail if dark energy has been changing.

“It would be a surprise if we found that dark energy were varying with time,” says Carroll, “but it would be so hugely important that it’s still worth looking.” ■ 11 April 2009 | NewScientist | 7

THIS WEEK

SOUNDBITES

Bob Holmes

change could wipe many species off the planet. Infectious pathogens depend on their hosts for survival so they too may become endangered – especially if, like malaria, they rely on more than one host (Ecology, vol 90, p 888).

Lafferty’s paper caused such a furore among its reviewers that the editor handling it, Ken Wilson of Lancaster University in the UK, commissioned a series of

MUD-SLINGING has broken out among ecologists over a study suggesting that climate change might not spread tropical diseases far and wide after all. When the paper triggered an uproar, editors at the journal Ecology decided to publish not one but six responses alongside the original research. The collection appears in the April issue.

Many disease researchers “The potential spread of have warned that rising global infectious diseases should temperatures could lead to more play a critical role in disease, for example by allowing climate change policy” tropical diseases to expand their ranges into what are now temperate regions. This is a responses arguing both sides of particular fear for insect-borne the debate to publish alongside it. diseases such as malaria and “I disagree with the whole line sleeping sickness. of reasoning,” says Mercedes But the reality is more complex, Pascual of the University of argues Kevin Lafferty, a disease Michigan in Ann Arbor. She points ecologist at the US Geological out that there are large human Survey’s Western Ecological populations in the east African Research Center in Santa Barbara, highlands, just outside of the California. He argues that a existing range of malarial warming climate could favour mosquitoes, and as temperatures some diseases in certain regions rise, the mosquitoes will reach while inhibiting them in others.

Lafferty does not deny that climate change might allow malarial mosquitoes to spread to new areas. However, he believes that hotter and drier conditions may also eliminate mosquitoes from areas where they currently thrive, such as the Sahel region in Africa. If this were the case, he says, there would be little if any net increase in the risk of disease.

In addition, many temperate regions such as southern Europe or the southern US have good sanitation and insect control programmes which, Lafferty says, would prevent diseases from becoming prevalent even if climatic conditions were suitable.

Finally, he argues, climate 8 | NewScientist | 11 April 2009

President Barack Obama criticises North Korea’s rocket launch, claiming it violates UN resolutions. He also announced plans for a summit aimed at global reductions in nuclear weapons (The Wall Street Journal, 6 April)

“Why would small island states be happy with a level of ambition that is going to destroy their countries?”

M. J. Mace, a legal adviser to the Federated States of Micronesia, explains why it and 42 other island states requested that developed countries aim to cut their emissions far beyond current goals (Reuters, 6 April)

“All these crimes are driven by money.”

A new “most wanted” list for individuals who violate environmental laws is growing fast as regulations tighten, according to Doug Parker of the US Environmental Protection Agency’s criminal investigation division (The New York Times, 5 April)

STEPHEN MORRISON/EPA/CORBIS

Will climate change spread disease?

“Rules must be binding.

Violations must be punished. Words must mean something.”

these areas. This will more than offset any benefits from decreased risk elsewhere, she says (Ecology, vol 90, p 906).

Richard Ostfeld of the Cary Institute of Ecosystem Studies in Millbrook, New York, says that while better health infrastructure in developed nations “might be heartening to some, it is far from universal”. For instance, several ecologists point out that there is evidence climate change is already increasing the incidence of malaria in the highlands of Ethiopia, where poor health infrastructure will harm any response.

Climate change is probably also causing an increase in non-human diseases. Drew Harvell, an ecologist at Cornell University in Ithaca, New York, says winter warming in the Caribbean is leading to increased rates of disease in corals (Ecology, vol 90, p 912).

Most of the ecologists do, however, seem to agree on one point: predicting where a disease is going to go next involves far more than just climate. No matter how the debate is resolved, they all agree that health concerns should continue to play a critical role in climate policy, and the debate shouldn’t be regarded as weakening the case for action on global warming. ■

“There are cases where children are egged on by people on websites so it is amazing to hear that being on a computer has saved somebody.”

Amanda Miles of charity Papyrus, on how a British teenager’s suicide note on Facebook sparked a rescue mission when it was spotted by a friend in the US. Three hours after posting the message, the boy was found alive (The Times, London, 5 April)

“It’s pretty much the one time of year where you get to see a lot of salamanders and it’s just really cool.”

Kaitlin Friedman of the University of Vermont describes the joys of being part of the “bucket brigade” that carry amphibians across busy roads on their annual journey to mate (AP, 5 April)

–Where will she feed?–

RICHARDS/HULTON/GETTY

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Diseases eat into world chocolate supplies IT’S chocolate egg season again, and sales of the pagan and Christian symbols of rebirth are as strong as ever. But the hunt for Easter eggs may truly be on next year, because chocolate trees are in increasing trouble.

Chocolate is made from the fermented, roasted seeds of the cacao tree. The cacao swollen shoot virus (CSSV) can kill the trees, and threatens to slash this year’s spring crop by a third in the world’s biggest producer, Ivory Coast. Meanwhile a fungus called witches’ broom is doing the same in Brazil. Now researchers are racing to sequence the cacao genome and find genes that can resist CSSV. Cacao trees are native to the Amazon rainforest, but west Africa produces 70 per cent of the world’s cocoa, virtually all on tiny, impoverished farms. In recent years, demand for chocolate has mushroomed. The farmers cannot afford expensive fertiliser so they boost production by planting more cacao trees over a greater area. That means cutting down other trees that normally grow between cacao crops, which

also replicate their rainforest origins and give them the protective shade they prefer.

“Increasingly cacao is grown almost as a monoculture,” says Paul Hadley of the University of Reading, UK. That promotes the spread of disease, as does the trend towards growing the trees in drier regions – water-stressed cacao trees are less able to fight off disease.

In recent years, CSSV has become an increasingly serious problem in Ivory Coast. The virus originated in native African trees, in which it is endemic, and is spread by common mealy bugs, so it can’t be avoided. The only defence until now has been to destroy millions of infected cacao trees to create disease firewalls.

Yaw Adu-Ampomah and colleagues at the Cacao Research Institute of Ghana (CRIG) have found cacao varieties in Africa that partially resist the killer virus, and they are trying to breed more resistant strains.

But progress is slow. New genetic stock brought over from South America must be quarantined for two years before

Praying to God is like talking to a friend

Identical brain areas, typically associated with rehearsal and repetition, were activated.

In the second, they improvised personal prayers before making requests to Santa Claus. Improvised prayers triggered patterns that match those seen when people communicate with each other, and activated circuitry that is linked with the theory of mind – an awareness that other individuals have their own independent motivations and intentions (Social Cognitive and Affective Neuroscience, DOI: 10.1093/scan/nsn050).

Two of the activated regions are thought to process desire and consider how another individual – in this case

IS PRAYER just another kind of friendly conversation? Yes, says Uffe Schjødt, who used MRI to scan the brains of 20 devout Christians. “It’s like talking to another human. We found no evidence of anything mystical.”

Schjødt, of the University of Aarhus, Denmark, and colleagues, asked volunteers to carry out two tasks involving both religious and “secular” activities. In the first task, they silently recited the Lord’s Prayer, then a nursery rhyme.

–Less chocolate might be good for some–

going to Africa, and experimental crosses take three years to grow before researchers can test for CSSV resistance.

Ray Schnell and colleagues at the US Department of Agriculture lab in Miami, Florida, are trying to speed things up. “We’re mapping genes for resistance to CSSV now,” he says. “It will all be a lot easier in a few years when we’ve

sequenced the cacao genome.”

If they can link particular DNA sequences with CSSV resistance, they hope to use them to make a testing kit so researchers in Africa can screen experimental crosses and plant only resistant seedlings. The CRIG is already using such a test to combat a fungal cacao disease called black pod. Debora MacKenzie ■

God – might react. Also activated were part of the prefrontal cortex linked to the consideration of another person’s intentions, and an area thought to help access memories of previous encounters with that person.

The prefrontal cortex is key to theory of mind. Crucially, this area was inactive during the Santa Claus task, suggesting volunteers viewed Santa as fictitious but God as a real individual.

Previous studies have found that the prefrontal cortex is not activated when people interact with inanimate

objects, such as a computer game.

“The brain doesn’t activate these areas because they don’t expect reciprocity, nor find it necessary to think about the computer’s intentions,” says Schjødt.

He says the results show people believe they are talking to someone when they pray, an outcome that pleased both atheists and Christians: “Atheists said it shows that it’s all an illusion,” says Schjødt, while Christians said it was evidence that God is real.

Robin Dunbar at the University of Oxford points out that the study proves neither: “This has nothing to do with whether God exists or not, only with subjects’ beliefs about whether God exists.” Andy Coghlan ■

“Brain scans reveal that people believe they are talking to someone when they pray”

11 April 2009 | NewScientist | 9

THIS WEEK quicker to get this brain space back – and regain movement – than the right. In one patient, the left hand reacquired a “presence” in the brain after 10 months and the right hand took 26 months.

The researchers say this Cognitive Science in Lyon, France, difference may be due to different used magnetic pulses to stimulate brain regions acquiring different these areas in two people who degrees of flexibility. Both patients had undergone double hand used prosthetic hands before the transplants. They found that transplant, using their right muscles in the new hands prosthetic more. As a result, the responded to the stimulation, brain regions that had previously suggesting that the brain had represented their left hands were commandeered faster by other parts of the body, a process that taught these brain regions flexibility. This meant that after the hand transplants, it was easier for these regions to adapt to receiving signals from the transplanted left hand than it was for those regions formerly responsible for the right hand to adapt to receiving signals from the right hand transplant.

This suggestion should not stop amputees waiting for a transplant from using prosthetic limbs, says Sirigu: “A prosthesis reduces the chronic pain experienced by patients so we can’t ask them –Pioneering transplant recipient Denis Chatelier (right)– to go without.” ■

A FINDING that hand transplants are eventually “accepted” by the brain is raising hopes that amputees may be able to recover full movement in their new limbs.

Surprisingly, there are also hints that in right-handed people, the left hand is accepted sooner.

In the brain, particular areas of the motor cortex develop links to different parts of the body.

If sensory input from a limb ceases as a result of amputation, the corresponding part of the brain initially goes unused. To stop prime real estate going to waste, the brain then starts to rewire itself – so that in a region once dominated by an amputated hand, the face and upper arm, say, start to “creep in”.

To find out if a transplanted hand can reclaim these brain regions, Angela Sirigu and colleagues at the Institute for

Risk gene for Alzheimer’s has early effects IS ALZHEIMER’S the result of a burnt-out brain? Healthy young adults carrying a gene variant that is a major risk factor for the disease seem to have extra activity in brain regions related to memory, even when their brains are at rest.

The gene APOE codes for a protein thought to help create, maintain and repair neuronal connections. One variant, epsilon 4, is considered the biggest risk factor for getting Alzheimer’s, increasing your risk by up to four times if you have one copy and up to 12 if you have two. It is not known exactly how epsilon 4 ups the risk, but in people who carry it and 10 | NewScientist | 11 April 2009

ALPHAFRANCE

Brain renews link to transplanted hands Helen Thomson

accepted them (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0809614106) A previous study showed that stroking a transplanted hand triggers brain activity in the same region as in non-amputees, but this is the first demonstration that the new hand muscles are actually represented in the brain.

“We can see the brain directly activating the new transplanted muscles,” says Sirigu.

Though both patients had been right-handed, the left hands were

have developed Alzheimer’s, the hippocampus, which is involved in memory functions, is usually smaller.

To figure out if epsilon 4 influences brain function earlier on in life, Clare Mackay of the University of Oxford and her colleagues scanned the brains of 18 healthy adults with epsilon 4 and 18 controls who did not have the variant. In the scanner, the volunteers spent time performing memory tests and also doing nothing.

During the memory task, the epsilon 4 carriers had more activity in the hippocampus compared with controls, even though there was no difference in their performance on the tests, suggesting that their

“The fact that we found differences in the hippocampus in healthy adults is very exciting”

hippocampi expend more energy to achieve the same result (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0811879106).

For the scans when the volunteers did nothing, the researchers focused on the “default mode network”, a series of connected sites throughout the brain that are active even when the volunteer is resting. Parts of the DMN found in the hippocampus were more active in the at-risk adults than in controls. “The fact that we got differences in the hippocampus is very exciting,” says Mackay.

One way to interpret this is that epsilon 4 causes brain regions responsible for memory to get overworked early in life, prompting them to “burn out” with age, leading to Alzheimer’s. However, it is impossible to tell whether the extra activity contributes to Alzheimer’s

symptoms later on or is just a sign of inefficient brain circuitry in the hippocampus.

Neurologist Michael Griecius of Stanford University in California, who studies the DMN in people with Alzheimer’s, agrees but says the work is a “real tour de force” because it shows differences so early on. “These subjects are several decades away from the point at which we would expect to pick up on the subtlest signs of cognitive difficulty,” he says.

Mackay says the next step is to look for early differences in brain function between those who have the gene variant and go on to suffer from Alzheimer’s, and those who have it and don’t. Such differences might be used to target interventions at certain people before the disease develops. Anil Ananthaswamy ■

CHRIS DAVIS ET AL

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Solar ‘double vision’ aids space weather warnings BURPS of hot ionised gas from the sun can knock out satellites and power grids when they hit Earth (New Scientist, 21 March, p 31). Till now their arrival has been hard to predict, but the first images of an earthbound burst captured by two satellites simultaneously have shown that we could get warnings 24 hours in advance that trouble is heading our way.

These clouds of plasma, called coronal mass ejections (CMEs), reflect sunlight and can sometimes be seen as expanding haloes around the sun. Unfortunately they are often faint, so CMEs travelling towards Earth are easily confused with material flowing out in other directions.

A demonstration using images from a pair of NASA spacecraft called STEREO (Solar Terrestrial Relations Observatory) shows the mission can provide early warnings. Launched in 2006, one of the STEREO craft is travelling ahead of Earth in its orbit while the other is lagging behind.

After a small CME hit Earth on 16 December 2008, Chris Davis of the Rutherford Appleton Laboratory at Harwell, Oxfordshire, UK, and colleagues examined images taken in the preceding few days by wideangle cameras called Heliospheric Imagers on the STEREO spacecraft.

Though the 16 December CME was too small to cause any damage, it appears clearly in

Feel at home when you crawl out of the sea

Hagadorn and Adolf Seilacher of Yale University now report that these tracks are very similar to the distinctive ones left by a hermit crab carrying a coiled shell. They conclude that the unusual tracks must belong to Protichnites that had partly inserted their tails into similar shells in order to carry them on land (Geology, vol 37, p 295).

Hauling shells would have given the critters an advantage. Trapped moisture protected them from drying out and helped keep their gills moist. The shells also shielded the animals from harsh ultraviolet light and protected them from changing temperatures.

Although the behaviour resembles that of a hermit crab, Hagadorn suspects these early explorers were the ancestors of a long-extinct group called sea scorpions, which had 6 to 13 pairs of legs. The tracks suggest the shells probably came from coiled molluscs, but other sources are possible. The hermit-like behaviour obviously had advantages, but the researchers say it is unclear how it came about. “We have no idea how this originated or what led to it,” Hagadorn says. Jeff Hecht ■

IT’S always good to have a bit of help to cross into the unknown. Some of the earliest creatures to crawl out of the ocean onto land half a billion years ago borrowed shells to carry a bit of the sea with them. This allowed them to survive in an otherwise hostile world, much like tanks of compressed air allow people to explore the deep ocean.

Palaeontologist James Hagadorn of Amherst College in Massachusetts has been studying fossilised tracks left in sandstone in central Wisconsin, dating back 490 to 510 million years. At the time, vast sandy tidal flats fluctuated between wet and dry zones, thrusting organisms into new environments.

Hagadorn had determined that several sets of tracks were made by Protichnites, an arthropod with many pairs of legs crawling across the sand and dragging its tail behind. But some of the tracks show odd markings along their left side, as if the animals had bent tails that dragged to one side.

–Trouble in store–

images from each spacecraft (pictured) in the days leading up to its arrival at Earth. “From both spacecraft, we were able to measure an angle which was consistent and showed it was heading towards Earth,” Davis says. With a few upgrades to the imaging software so that relevant data could be analysed in real time, the CME’s impact on Earth could be predicted 24 hours

before its arrival, the team says in a paper to be published in Geophysical Research Letters.

“It’s really quite an advance,” says Howard Singer of the Space Weather Prediction Center in Boulder, Colorado, who was not involved in the study. “We’ll be able to use this data and this technique to give forecasts that are far superior to what we’ve had before.” David Shiga ■

11 April 2009 | NewScientist | 11

HIDEO KURIHARA/ALAMY

IN BRIEF Hurricanes worst a day after lightning

See-through wings need springy scales to stay dry The mystery of how butterflies with translucent wings stay dry has been solved by new high-resolution images – and the trick is bounciness.

Butterfly wings are covered in a dense array of microscopic overlapping scales that give them their remarkable colours and also repel water. But the wings of some species have transparent or translucent panels where there are far fewer scales, with large gaps between them. As well as helping the insects recognise other members of their species, the panels confuse predators that do not recognise the translucent zone

as part of the butterfly. The price the butterflies pay is reduced waterproofing, but now ecologists at Kyoto University in Japan have discovered how they survive.

Pablo Goodwyn used electron microscopes to study the wings of the Japanese chestnut tiger butterfly, Parantica sita (pictured), which lives for up to six months and migrates up to 1000 kilometres. He found that scales shaped like flattened needles cover less than half of translucent areas. But because the scales tilt about 30 degrees upwards from the wing surface, they act like springs, bouncing away water droplets that land on them. A similar butterfly from the same area as P. sita does not have springy scales, so water can wet its wings.

It lives less than a month (Naturwissenschaften, DOI: 10.1007/s00114-009-531-z).

Grown ear cells could help restore hearing TWO types of human ear cell have been grown in the lab from fetal stem cells. The initial hope is to use these cells to devise ways to regenerate or repair ear cells and screen for chemicals that cause hearing loss. Further in the future, similar cells might be delivered to damaged ears to restore hearing.

Marcelo Rivolta of the University of Sheffield in the UK and colleagues extracted cochlear 12 | NewScientist | 11 April 2009

stem cells from aborted fetuses, with the consent of the women involved. Such stem cells stop being produced after 11 weeks’ gestation. “That’s why deafness is permanent, because we don’t have the stem cells to replace damaged cells in the ear,” says Rivolta, whose team presented the findings on 6 April at a stem cell conference in Oxford, UK. Rivolta’s team exposed the

stem cells to various nutrients and growth factors, and found one cocktail that produced cells similar to auditory hair cells. When mature, these cells grow hairs that bend in response to sound, generating electrical signals.

A second recipe generated auditory neurons, which receive signals from the hair cells and transmit them to the brain.

The team is now trying to make ear cells from embryonic stem cells, to avoid the need for fetuses.

A GLOBAL analysis of lightning during hurricanes has bolstered observations that the worst winds come a day after the bolts strike.

Forecasters struggle to predict peak hurricane winds. So Colin Price of Tel Aviv University in Israel and colleagues studied all category 4 and 5 hurricanes between 2005 and 2007. Out of 58 hurricanes, 56 showed a significant correlation between lightning activity and wind speed, with peak winds arriving 30 hours after the lightning on average. Price believes the lightning may be caused by a change in wind patterns (Nature Geoscience, DOI: 10.1038/NGEO477).

Previous sightings have hinted at a link, but Price’s work puts this “on a firm statistical foundation”, says Robert Holzworth of the University of Washington, Seattle.

However, Steven Businger of the University of Hawaii argues that Price’s lightning database was not detailed enough.

Slave ants keep a taste for revenge FORGET Spartacus – you need look no further than an ant colony for a slave mutiny.

Some ant species raid colonies of smaller species, killing the queen, scaring away worker ants and stealing larvae. Kidnapped larvae grow up as slaves.

Susanne Foitzik of the LudwigMaximilian University in Munich, Germany, has evidence the slaves have evolved an unusual weapon in the fight for survival: mutiny.

When her team monitored 473 pupae in 88 slave-making colonies, they saw enslaved worker ants destroy two-thirds of newly hatched queens and female workers of their captors. Male pupae, which do not conduct raids, were left alone (Evolution, vol 63, p 1068).

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THERE’S nothing like a good scratch, but how does it take away the itchiness? Researchers have identified the neurons in monkeys that are dampened by scratching, a finding that could lead to new ways of alleviating itching in humans.

In people, a variety of stimuli, including chemicals like histamine, prompt sensory neurons to fire, sending a signal via the spinothalamic tract (STT) to the brain, prompting an itchy feeling.

To find out which of these neurons are suppressed by scratching, Glenn Giesler at the University of Minnesota in Minneapolis and colleagues implanted electrodes into the spinal tract of anaesthetised macaques before injecting histamine into their legs. STT neurons fired in response, but scratching the skin caused the frequency of the firing to drop in some of the neurons, indicating that these are the ones targeted by scratching (Nature Neuroscience, DOI: 10.1038/nn.2292).

The hope is to find the equivalent neurons in people, and then to work out how to suppress them, via drugs or electrical pulses, in order to relieve itchiness caused by skin problems such as scabies, eczema and psoriasis.

Anti-itch medications rarely offer sufficient relief, and scratching can damage skin and cause infections.

Medieval warm period strikes blow to climate change deniers CLIMATE change deniers have been deprived of one of their favourite arguments against human-induced global warming.

During the Medieval Climate Anomaly (MCA), Europe basked in balmy weather, and some claim that whatever natural mechanism caused it is warming the world today. To find out, Valerie Trouet at the Swiss Federal Institute for Forest, Snow and Landscape Research in Birmensdorf and colleagues studied the growth rate of trees in Morocco and a stalagmite in Scotland, both dating

back 1000 years, to determine rainfall levels during the MCA. They found a big difference in rainfall, and hence pressure systems, in each region at this time. This suggests that from 1050 to 1400 the North Atlantic experienced a strongly positive North Atlantic Oscillation (NAO) – the regional climate system that drives winds from the Atlantic over Europe. The more positive the NAO, the more warm air is blown towards the continent.

To investigate why the warm winds were so persistent, lasting

350 years, the team combined their data with information from other regions of the world. It turns out that the El Niño system was in the negative La Niña mode, which, as the two systems are connected by ocean currents, could have reinforced the NAO (Science, vol 324, p 78). A persistently positive NAO is not operating today.

External forces like abrupt changes in solar output or volcanism could have started and stopped the cycle, says Trouet, who hopes to pinpoint the trigger at a climatology workshop in May. JUAN PABLO MILANA

How scratchy beats itchy

Doctors tune in to cause of back pain TUNING forks, brushes and erasers can all help to quickly and cheaply reveal which painkiller to prescribe for back pain.

From a patient’s description, doctors struggle to distinguish between neuropathic pain from nerve damage, such as in sciatica, and pain from inflammation, yet each requires a different painkiller. Only expensive tests such as MRI scans reveal the source precisely, leading Joachim Scholz of Massachusetts General Hospital in Boston and his colleagues to look for a quicker, cheaper way.

The team compiled a list of quick questions and physical tests and assessed the response of patients diagnosed with each type of pain. From this, they whittled the list down to six questions and 10 physical tests that included rubbing brushes, safety pins, tuning forks and pencil erasers on the back.

Together, the tests can show whether or not the pain is neuropathic (PLoS Medicine, DOI: 10.1371/journal.pmed.1000047).

The whole list takes just 15 minutes to complete and also distinguishes between three types of neuropathic pain.

You won’t see a bigger ripple than this THEY may look like low dunes, but the cresting ridges pictured above are the world’s largest “megaripples”, a phenomenon that had been thought impossible on our planet.

Wind-formed ripples are not the same as dunes because they are shaped by the airflow less than 2 metres above the ground. The key factor for dunes is air fluctuations as high as 4 kilometres up.

Most such ripples are no bigger than those created by waves on a beach. Given high winds, light grains and geologic timescales, however, they can grow. Juan Pablo Milana of

the National University of San Juan, Argentina, has found monster ripples of lightweight pumice on the country’s Puna plateau, where winds may exceed 400 kilometres per hour.

The ripples are up to 2.3 metres high and 43 metres between crests – triple the height and double the wavelength of the largest previously known on Earth (Geology, DOI: 10.1130/g25382a.1).

Only Mars might have bigger ripples. However, Jim Zimbelman of the Smithsonian Institution in Washington DC suspects the Puna ripples beat even Martian ones.

11 April 2009 | NewScientist | 13

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TECHNOLOGY

Driving games raise emotions VIDEO games don’t have to be violent to trigger an emotional response.

It turns out that driving games can activate more brain regions involved in emotional processing than shoot ’em ups.

Many studies have suggested that violence in video games could be linked to aggression. To investigate further, Simon Goodson and Sarah Pearson of the University of Huddersfield in the UK recruited 30 adults aged between 18 and 45 to play either a competitive driving game, a shoot ’em up or virtual table tennis against computer-generated competitors. Brain activity, heart rate and breathing were all monitored during the game, and a questionnaire afterwards assessed their levels of anger, hostility and aggression.

The volunteers scored normally for aggression after playing the driving

and shoot ’em up games, while those playing the table tennis game scored as slightly less aggressive than the average for the volunteers. However, when it came to brain activity, the driving game caused a significant increase in the temporal lobe, an area of the brain associated with

“It cannot be assumed that aggression is solely related to the violent content of video games” emotional processing. “It cannot be assumed that aggression is solely related to violent content,” says Goodson, who presented the results at a British Psychological Society meeting in Brighton last week.

Previous research has hinted that playing driving games leads to more risky and aggressive driving.

–Driven to feel–

Flying by the seat of their tanks

Full steam into the record books?

PILOTS are trained how to fly their aircraft if an engine or other flight systems fail, but what if they lose control of the steering?

Now Airbus has come up with a way for pilots to fly a plane to the nearest runway in even these extreme circumstances.

In a US patent filed last week, Airbus says damaged aircraft could be controlled by moving fuel quickly between fuel tanks in the wing, fuselage and tail, shifting the centre of gravity to provide rudimentary steering.

This could easily be achieved, Airbus says, by programming flight management software to include fuel-based steering among its emergency options.

If the pilot needed to roll to the left, the system would pump fuel to the left wing’s tank. To pitch the nose up, fuel could be pumped to the tank in the tail.

THE British Steam Car Challenge team are gearing up for an attempt on the world steam-powered land speed record, following successful tests last week.

The project, which is designed to raise awareness of cleanburning fuels, is aiming to reach 270 kilometres per hour with its steam car later this year. In so doing it would break the world record of 204 kilometres per hour set by the American Stanley Steamer in 1906.

The car itself is 8.5 metres long and weighs 3 tonnes. It is powered by demineralised water, which is

931

The average dollar loss suffered by the 206,884 people who reported internet crimes to the FBI in 2008

pumped into a dozen 250-kilowatt boilers – equivalent to about 1200 electric kettles. These provide steam to a 268-kilowatt turbine that drives the rear wheels.

Following tests at Thorney Island airfield in Hampshire, UK, in which the car reached 130 kilometres per hour, the team is now awaiting final clearance from Edwards Air Force Base in California to use Rogers Dry Lake for the record bid. The advantage of the dry lake is that it is 600 metres lower than Utah’s famous Bonneville Salt Flats, so there is more oxygen available for the boilers, enabling the car to develop much more power.

The team hopes to be on site when the lake dries out in May.

“What’s going on? So far – nothing” Patrik Runald of computer security company F-Secure reports on the puzzling lack of impact of the Conficker virus, which is thought to have infected more than 12 million computers and was expected to activate on 1 April (F-Secure blog, 1 April)

11 April 2009 | NewScientist | 15

TECHNOLOGY

A password in your ear

ALTRENDO/GETTY

Your ears make their own distinctive noises, albeit quietly. Could they be used to prove your identity?

Paul Marks

YOU are the victim of identity theft and the fraudster calls your bank to transfer money into their own account. But instead of asking them for your personal details, the bank assistant simply presses a button that causes the phone to produce a brief series of clicks in the fraudster’s ear.

A message immediately alerts the bank that the person is not who they are claiming to be, and the call is ended.

Such a safeguard could one day be commonplace, if a new biometric technique designed to identify the person on the other end of a phone line proves successful. The concept relies on the fact that the ear not only senses sound but also makes noises of its own, albeit at a level only detectable by supersensitive microphones.

If those noises prove unique to each individual, it could boost the security of call-centre and telephone-banking transactions 16 | NewScientist | 11 April 2009

and reduce the need for people to remember numerous identification codes. Stolen cellphones could also be rendered useless by programming them to disable themselves if they detect that the user of the phone is not the legitimate owner.

Called otoacoustic emissions (OAEs), the ear-generated sounds emanate from within the spiralshaped cochlea in the inner ear.

They are thought to be produced by the motion of hair cells within the outer part of the cochlea.

Typically, sounds entering the ear cause these outer hair cells to vibrate, and these vibrations are converted to electrical signals which are transmitted along the auditory nerve, allowing the sound to be sensed. Crucially, these cells also create their own sounds as they expand and contract.

Ear identification scan A series of clicks played into the ear generates a faint but distinctive sound in return, which varies according to the unique internal shape of the person’s ear SPEAKER AND ULTRASENSITIVE MICROPHONE

MIDDLE EAR

BONE

EAR CANAL

BONE

EARDRUM

COCHLEA

That’s because “hearing is an active process – the ear actually puts energy into the incoming sound waves to replace energy lost as sound is absorbed by the ear’s structure”, says Stephen Beeby, an engineer at the University of Southampton, UK, who is leading the research. “This process helps us hear things we otherwise would not, but as a result some of the energy added by the hair cells escapes as OAEs.” Predicted in the 1940s but not detected until ultralow-noise microphones were developed in the 1970s, OAEs can be provoked when a series of clicks is played into the ear. The returning sound emissions comprise signals of between 0 and 5 kilohertz, and vary in amplitude. Click tests are already used to check newborn babies’ ears for signs of hearing difficulties, since the OAEs are weaker if the inner ear is defective.

What sparked the interest of Beeby and his colleagues is the fact that the power and frequency

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“Whether this is a practical way of telling people apart as a real world biometric still needs a lot of work” Mansfield, head of biometrics assessment at the UK’s National Physical Laboratory in Teddington, says the team will have to prove not only that their technique has a low falsematch rate, but also that a person’s recorded OAE will match their OAEs over the long term. “It has to be able to reliably recognise people over long time periods,” he says. “For example, a fingerprint taken from a 20-year-old is still valid when they are 60.” ■

Adam learned something about the function of the knocked-out gene.

The robot could carry out more than 1000 of these experiments a day.

In all, Adam formulated and tested 20 hypotheses about genes coding cameras, liquid handlers, incubators for 13 enzymes. Twelve hypotheses and other equipment. were confirmed. For instance, Adam The team gave the robot a freezer correctly hypothesised that three containing a library of thousands of genes it identified encode an enzyme mutant strains of yeast with important in producing the amino individual genes deleted. It was also acid lysine. The researchers equipped with a database containing confirmed Adam’s work with their information about yeast genes, own experiments (Science, DOI: 10.1126/science.1165620).

“Adam is moving closer to The team is now working on a new robot, called Eve, which will the goal of an artificially search for new drugs. intelligent machine that Adam, Eve and their ilk could cooperates with humans” soon automate routine and timeenzymes and metabolism, and a consuming scientific chores, leaving supply of hundreds of metabolites. human scientists free to make To discover which genes coded higher-level, creative leaps, says for which enzymes, Adam cultured King. Ultimately the robots may a mutant yeast with a certain gene even be capable of conducting truly knocked out, and monitored how independent research, he says. well the mutant grew without a Will Bridewell, an artificial particular metabolite. If the strain intelligence researcher at Stanford grew poorly without the metabolite, University in California, says Adam is operating only at the level of a graduate student. Still, the robot is moving closer to the goal of an artificially intelligent machine that can cooperate with other scientists and write up their results in natural language, he says. “That’s probably far off, but it seems likely that we will get there. This is yet another step on the way.”

In a further step in this direction, researchers at Cornell University in Ithaca, New York, have developed software that can observe physical systems and independently identify the laws that underlie them.

The software, which was not pre-programmed with any basic rules of physics or geometry, was shown images of moving systems such as a double pendulum. It then used an evolutionary algorithm to generate mathematical equations, and tested them to see if they accurately described the system it had observed. For instance, the computer produced an equation that described conservation of angular momentum (Science, DOI: 10.1126/ –Not your average scientist– science.1165893). Kurt Kleiner ■

My name is Adam and I’m a whizz with baker’s yeast A ROBOT scientist that can generate its own hypotheses and run experiments to test them has made its first real scientific discoveries, according to its developers.

Dubbed Adam, the robot is the handiwork of researchers at Aberystwyth University and the University of Cambridge in the UK. All by itself it discovered new functions for a number of genes in Saccharomyces cerevisiae, better known as baker’s yeast.

Ross King, a computational biologist at Aberystwyth, who leads the project, says that Adam’s achievement is modest, but real.

“It’s certainly a contribution to knowledge. It would be publishable.”

Adam, which actually consists of a small roomful of lab equipment, has four personal computers that act as its brain, and possesses robot arms, JEN ROWLAND

distribution in the OAEs provoked by specific series of clicks seem to be highly distinctive, driven by the internal shape of the person’s ear. “Anecdotally, audiologists say they can tell different people apart – men, women, even people of different ethnic origins – by the profile of the widely varying types of emissions the clicks evoke,” he says.

So with funding from the UK’s Engineering and Physical Sciences Research Council, Beeby’s team is attempting to work out if OAE patterns can be used in biometry, like iris scans or fingerprints. “In the controlled conditions of a lab, everybody’s emissions are indeed different, but whether this is a practical way of telling people apart as a real-world biometric still needs a lot of work,” he admits.

There are a number of problems that must be dealt with, he says.

In subjects that have been drinking alcohol, for example, emissions are deadened. And different drugs alter the amplitude of OAEs, as do ear infections or wax build-up.

If they succeed by the project’s deadline in mid-2010, they hope to interest electronics firms in making headsets or cellphones with a supersensitive microphone in the earpiece. The rest is done with software, says Beeby.

Establishing a new biometric, however, is a huge task. Tony

11 April 2009 | NewScientist | 17

TECHNOLOGY

Battery grown from ‘armour-plated’ viruses GENETICALLY engineered viruses that assemble into electrodes have been used to make complete miniature rechargeable batteries for the first time. The new lithium ion batteries are as powerful as existing devices but smaller and cleaner to make, claim the team behind the work. The technology could improve the performance of hybrid electric cars and electronic gadgets.

Lithium ion batteries exploit the reactivity of lithium to produce a current. Inside the battery, lithium ions move from the anode to the cathode, forcing

“It’s environmentally friendly because much of its materials can be made at room temperature” electrons in the opposite direction around an external circuit. This process is reversed when the battery is recharged.

Making these batteries takes a tough manufacturing process because of the highly reactive components, aggressive solvents and high temperatures used in

construction, as well as the dangers of handling lithium.

Viruses could make this process much safer and cleaner, says Angela Belcher at the Massachusetts Institute of Technology. Her team converted a harmless virus called M13 into a cathode by inserting a gene that causes the virus to produce proteins that bond with iron and phosphate ions in a surrounding solution. As a result, the long, tubular virus particles become sheathed in an “armour plating” of iron phosphate, turning them into nanowires.

The resultant batteries were not as good as commercial models, however – the cathodes turned out to be good at conducting lithium ions but not electrons.

To solve this, the team inserted a second gene that creates a protein at the tip of the virus that bonds to a carbon nanotube. The nanotube increases the electron conductivity of the combined structure (see diagram). “We were basically adding a highway that allows the electrons to move in and out rapidly,” says Belcher.

Eyeball spy turns the tables on Big Brother AN ORWELLIAN nightmare it may be to many of us, but CCTV is a boat full of holes to the organisations that pay for it. That’s because the people watching CCTV images back in the control rooms often have too many screens to monitor at once, and so may miss the criminal or antisocial activities they are there to spot.

To the rescue of Big Brother’s limited attention capabilities come Ulas Vural and Yusuf Akgul of the Gebze Institute of Technology in Turkey, who have developed a gaze-tracking camera system that 18 | NewScientist | 11 April 2009

watches the eyeballs of CCTV operators as they work. It then automatically produces a summary of the CCTV video sequences they have missed during their shift. “This increases the reliability of the surveillance system by giving a second chance to the operator,” the researchers write in the journal Pattern Recognition Letters (DOI: 10.1016/j.patrec.2009.03.002).

The system uses webcam-style cameras trained on the irises of the CCTV operators. From this, software works out where the operators are

Growing better batteries The M13 virus has been modified to bond with iron and phosphate ions, and with carbon nanotubes M13 virus plated with iron phosphate

Carbon nanotube

When used as a cathode, the armour plated virus conducts lithium ions while the carbon nanotubes improve electron conductance CATHODE

ELECTROLYTE

ANODE

The resulting battery turned out to be as good as the best commercially available that use crystalline lithium iron phosphate materials (Science, DOI: 10.1126/science.1171541). And since the team had previously used the same viral technique to produce anodes (New Scientist

looking as they stare at each monitor – and the areas they have not been paying attention to. From this it creates a video of what they missed, for them and their bosses to watch at the end of their shift .

To make sure the summary can be watched as quickly as possible, Vural and Akgul have developed an

“The gaze-tracking system may well be regarded as intrusive by CCTV controlroom staff” algorithm that discards frames that show only the background with no people or moving vehicles in them, to leave only a few key frames for each scene of interest. Vural says the

online, 6 April 2006), it has now been able to make a full virusbased 3-volt lithium ion battery.

Compared to conventional lithium ion batteries, the biologically grown battery is environmentally friendly because much of the materials can now be made at room temperature or on ice and without harsh solvents. “It’s a pretty simple process that doesn’t require fancy equipment,” says Belcher.

It has potential to be even better, though. This production system could boost battery performance because it uses nanostructured materials that can store and release more power than conventional materials, and also do it faster. Already Belcher’s prototype battery is as powerful as existing technologies, an ability she has shown off by using one to power an LED. Her team is now investigating materials that work at higher voltages and with higher energy-storage capacities.

Joachim Maier, at the Max Planck Institute for Solid State Research in Stuttgart, Germany, reckons using biology is a useful approach. “Not too many people look into biology in this context, so from that point of view it is very interesting,” he says. Catherine Zandonella ■

system runs on a standard PC and processes the images in real time, so the summary frames are ready to browse, like a fast-motion flip book, at the end of the shift.

Privacy campaigners may enjoy the irony if the gaze-tracking system comes to be regarded as intrusive by CCTV operators – who could fear that employers will use it to dispense with their services if they consistently miss too much on-screen skulduggery.

Mike Lynch, chief executive of Autonomy, a smart software company based in the UK that has created its own CCTV analysis algorithms, points out that gaze does not prove that an operator is registering the action.

“They may be looking but not seeing,” he says. Paul Marks ■

OPINION

Battle for Turkey’s soul A Turkish science magazine’s pulling of a cover story on Darwin could be a taste of struggles to come – but it may also be a good sign, says Debora MacKenzie TURKEY is the Islamic world’s leading secular democracy.

It spends a large proportion of its income on scientific research and aims to match that of the European Union by 2013. Turks like science: one of the country’s top-selling magazines is the popular science monthly Bilim ve Teknik (“Science and Technology”), published by the country’s scientific funding agency TÜBITAK. The best-seller is a science monthly for kids.

But Turkey is also a hotbed of creationism. So when a cover feature on Darwin planned for the March issue of Bilim ve Teknik was pulled at the last minute, it caused an uproar. Turkish scientists suspected that pressure from religious politicians had led to censorship. Is Turkey changing course? Does this bode ill for science in the Muslim world?

It depends. Seen in context, the incident could be a good sign, as the inevitable growing pains of a country adapting to a scientific world view. The key question is which way the process goes now.

What happens in Turkey is important because its battles could be the first of many.

First, the basics. In early February the editorial staff of Bilim ve Teknik decided to mark the 200th anniversary of Darwin’s birth with a 15-page cover story on evolution. The issue went to the printer on Saturday 28 February.

The following Monday, editor Çig˘dem Atakuman received a phone call from TÜBITAK vicepresident Ömer Cebeci. The presses were stopped. The issue finally came out a week late with 20 | NewScientist | 11 April 2009

the Darwin article gone and the environment” of Turkey. cover featuring a story on global Whether the cancellation warming. So what happened? was an administrative glitch, It depends on who you ask. censorship, or just an attempt Cebeci maintains that he did not to sidestep controversy, the row order Atakuman to remove the is highly revealing. Evolution is piece. He insists there was no a lightning-rod issue in Turkey. censorship, only that the dropped Every leading newspaper reported article had been “prepared hastily the story. The Turkish Academy without regard to institutional of Sciences called for an procedures”. TÜBITAK says the investigation and for Cebeci magazine will carry a Darwin to resign (neither seems likely, special later this year. although another senior TÜBITAK Atakuman sees it differently. official resigned in protest).

She issued a public statement Scientists, who mostly suspect saying that the pages were “Turkish scientists planned as normal and that suspected that pressure Cebeci had ordered her to cancel from religious politicians the piece as it was deemed led to censorship” inappropriate for the “sensitive

censorship, demonstrated in Ankara; readers returned their March issues of Bilim ve Teknik. New Scientist’s blog raised impassioned comments from Turks.

Those at the centre of the fuss say it portrays Turkey in the wrong light. “I am sad to think that people are seeing my country through this incident. Most people are secular,” says Atakuman. Cebeci adds: “The outside perception of these events as censorship of science has caused great sorrow at TÜBITAK.” In many respects they are right. Incidents like this are, paradoxically, a hallmark of countries that are adapting to secularism, as Turkey appears to be. In surveys, about a quarter of Turks accept evolution – way more than nearly all Muslim countries, though less than any rich, industrialised one. That puts Turkey in the midst of a social transition that can be painful. All over the world, people are leaving the security of religion-dominated societies for the uncertainties of secular ones. The resulting alienation fuels fundamentalist religion, and makes evolution the focus for backlashes against secular society. Some western countries are still in this transition.

Turkey is the Islamic country furthest down this road, so that is where trouble with evolution is flaring, says Salman Hameed of Hampshire College in Massachusetts, who studies Muslim creationism. “Evolution just isn’t an issue elsewhere – yet,” he says. As other Islamic countries modernise, however, it will be.

Comment on these stories at www.NewScientist.com/opinion

Debora MacKenzie is New Scientist’s European correspondant

VIEWFINDER “What kind of doctors will they be, these students who have never experienced human dissection?”

Christine Montross in The New York Times contemplates the effect of a plan to stop medical students dissecting human cadavers

“The Turing test still has not been passed, though there is apparently a human being somewhere who failed it” Susan Greenfield in Wired UK, on attempts to build a conscious machine

“Guy walks into a shrink’s office. Says he’s gay and wants to be straight.

Shrink says, ‘OK, I’ll help.’ Don’t wait for the punch line. There isn’t one, because this isn’t a joke” William Saletan in Slate, commenting on reports that 1 in 6 British psychiatrists admitted to having helped at least one patient attempt to alter their homosexual feelings

“It’s a warning about the pitfalls of our unshakeable belief in the limitless promise of our endeavors, regardless of reality’s constraints. It is a lesson about the dangers of our love affair with progress” Eduardo Porter in The New York Times reflects on the 20th anniversary of claims for cold fusion

Good week for…

Irrawaddy dolphins The Wildlife Conservation Society announced the discovery of around 6000 of the freshwater cetaceans in Bangladesh. Previous estimates put the entire population at a few hundred.

Bad week for…

The afterglow of the big bang A pair of radio telescopes designed to pick out exquisite details in the cosmic microwave background have been axed.

GERARD SOURYSTILL PICTURES

That is not to say that Turkey will necessarily continue down this road. Although the modern Turkish state was secular from its foundation, since a military coup in 1980 secularism has been rolled back by religiously inclined governments, says biologist Can Bilgin of the Middle East Technical University (METU) in Ankara. In 1985, the elected government put creationism into high school biology texts, where it remains.

Turkey is reaping the fruits of that now, Bilgin believes.

The governing party AKP is moderate Islamist, and education minister Hüseyin Çelik has equated Darwinism with atheism and supports intelligent design.

Pressure on scientists is increasing and Bilgin fears more incidents like the one at Bilim ve Teknik. He is not alone. “I believe the situation is getting worse for science and science education than many people in Turkey are aware of,” says Aykut Kence, another biologist at METU and a veteran campaigner for evolution.

Turkish scientists are fighting back. They are pursuing a lawsuit to have creationism removed from textbooks. A group of activist students called Hard Workers of Evolution has translated the University of California’s Understanding Evolution website. In February, Turkish scientists launched the Darwin 2009 Assembly and will hold conferences on evolution across Turkey this year.

If nothing else, the Bilim ve Teknik incident has focused minds.

“Censoring Darwin caused outrage among students and academics,” says Kence. “It may actually make our job easier,” adds Bilgin. Even Cebeci agrees: “The positive side was that it revealed the sensitivity of our scientific community to the autonomy of science.” Let’s hope they will be able to continue using that autonomy to stand up for what matters. ■

Horizon scanner Watch out for acres of coverage about Earth being hit by a slate-wiping space impact. Scientists gather in Granada, Spain, at the end of this month to discuss what could be done if they discovered an asteroid or comet on a collision course with the Earth 11 April 2009 | NewScientist | 21

OPINION LETTERS Red List concerns From Mark Simmonds, Whale and Dolphin Conservation Society Rachel Nowak’s challenging article on the Red List of the International Union for Conservation of Nature (14 March, p 8) raised a number of concerns, but left out one arguably obvious one – the consequences of climate change.

What climate change means for the application of the Red List is not clear. To be fair, the IUCN has recently recognised this and is now progressing the development and application of criteria that will help to access species’ vulnerabilities to climate change itself. They then plan to use this in conjunction with the Red List.

Meanwhile, we are left with Red List assessments that do not take this into account and I feel that this makes them of limited use.

This is the case, for example, with the assessments of whales, dolphins and porpoises concluded in 2008, in which predicted and observed changes in key habitats, notably at the poles, were not taken into account. Consequently, existing assessments may make these animals seem more robust than they really are.

The challenge to many species and populations from climate change will be whether they can adapt to the rate of change, and perhaps this is also now true of the Red List itself: can it adapt to be a useful tool in terms of assessing vulnerability in a rapidly changing world? Will it be swift enough to respond to the sometimes unpredictable, but undoubtedly important, changes that will increasingly affect species, or do we need a new approach?

Chippenham, Wiltshire, UK From Holly Dublin, IUCN Species Survival Commission, African elephant specialist group chair; and Julian Blanc, former African elephant database manager The assessment of African elephants for the Red List did require the pooling of data of varying quality. However, the statement in Rachel Nowak’s article that we “opted to pool all the data [we] had no matter how shaky” is misleading. The listing of the African elephant is highly sensitive, and we take great pains when conducting the assessment to remain consistent by leaving out the most unreliable estimates of population size, such as

Enigma Number 1540

On the run RICHARD ENGLAND On three days in each calendar week (Sunday to Saturday) I go for a run, but I never run on two consecutive days.

In the last 12 years there was (a) a year when I went for two more runs in February than in March, (b) a year when I went for four more runs in March than in February.

Which years were those?

WIN £15 will be awarded to the sender of the first correct answer opened on Wednesday 13 May. The Editor’s decision is final.

Please send entries to Enigma 1540, New Scientist, Lacon House, 84 Theobald’s Road, London WC1X 8NS, or to enigma@newscientist.com (include your postal address).

Answer to 1534 Head start: It is 192 metres from Harey’s house to school The winner Tim Glanvill of Northallerton, North Yorkshire, UK

22 | NewScientist | 11 April 2009

extrapolations of assumed elephant densities over assumed range, while retaining a sufficiently large sample size to avoid spurious conclusions.

A substantial proportion of the first comprehensive continental population estimates, attempted in the 1970s, were known to have been largely speculative.

Therefore, in assessing the African elephant we are left with a choice between pooling spotless and blemished apples together or making no comparison at all, which would lead to a “Data Deficient” listing. The latter would be unacceptable to the global conservation community for a species as relatively well known as the African elephant.

We are aware of the controversy around the Red List: whether it is overly cautious or not precautionary enough in assessing species, in particular for those species that are long-lived, widely distributed and known to have radically different conservation status in different parts of their range. The manner in which the Red List deals with uncertainty is the topic of extensive debate, and the confounding of these healthy, ongoing debates with misleading statements does a major disservice to – and is an unnecessary distraction from – the important work needed to conserve the most vulnerable populations of African elephants.

Cape Town, South Africa

Societal drinking From Munjed Farid Al Qutob Andy Coghlan is to be commended for bringing to our attention the dangers of “passive drinking” and its impact on our environment, economy and society (28 March, p 22). However, the problem has reached such proportions that it cannot be solved simply by increasing the price of alcohol. A multi-pronged approach is urgently needed,

requiring all stakeholders to share responsibility. Parents need to ensure they pay enough attention to their children’s behaviour, the advertising industry should take a key role in highlighting the perilous repercussions of binge drinking, and the government should address the issue by offering better job stability, improved education and healthier places for teenagers to hang out, such as sporting facilities.

London, UK

Astral experience From Eric L. Altschuler, University Hospital, Newark; and Vilayanur Ramachandran, Brain and Perception Laboratory, University of California, San Diego We read your two-part series on out-of-body experiments with interest (14 March, p 33, and 21 March, p 36). We were surprised that you did not mention our method, which uses two mirrors to create within seconds the experience of standing outside oneself (Perception, vol 36, p 632).

This 2007 paper was the first to report a method to perceive being outside of one’s body.

Newark, New Jersey, US, and San Diego, California, US

Specious selection From Jonathan Arch I was pleased to read that the gene-centred view of evolution is increasingly being challenged (7 March, p 36), because for me

For more letters and to join the debate, visit www.NewScientist.com/letters

it has never made sense.

If one wants a reductionist theory of evolution, surely the DNA nucleotide is the basic unit.

By focusing on the gene – a set of imprecisely defined nucleotides, some of which may contribute to more than one gene – Richard Dawkins and others implicitly acknowledge that selection operates at a particular level of interacting units.

If selection can operate at this level, why not at higher levels, such as species or ecosystems?

Buckingham, UK

Skinny-dippers From Francesca Mansfield I was delighted to see that the aquatic ape theory got a small mention in the profile box of Elaine Morgan’s article on the similarities between orang-utans and humans (7 March, p 26). The theory is considered by some to be a non-starter, but if we wait for palaeontologists to procure the fossil evidence of aquatic evolution along ancient, long-lost coastlines, we’ll be waiting longer than Darwin had to wait for the

by aquatic mammals or mammals with some kind of aquatic history.

Finally, perhaps we should consider that the aquatic ape theory may be relevant to more than just our past. If global warming continues to turn most of our habitable zones into desert, we may have no other recourse but to turn, once more, to the sea to survive.

Volos, Greece

Essentials first From Donald Scott Debora MacKenzie advises that “it is not a good idea to be sick in a poor country”, and this is undoubtedly true (28 February, p 22). However, the majority of illness in developing countries has nothing to do with a lack of pharmaceutical availability; medicines don’t make a population healthy. The countries that support UNITAID are lobbied continuously by pharmaceutical companies to ensure they don’t lose their developing markets.

If those countries want to encourage healthy populations, why don’t they allocate more of their budgets for clean water, sanitation, healthy food and the other essentials of life?

Kilmacolm, Renfrewshire, UK

Suicidology

fossil and DNA evidence to support his theories.

There is biological evidence: the “scars of evolution” as Morgan so aptly entitled one of her books.

Our most singular human features, such as hairlessness, bipedalism, language, menopause, tear glands, breath control, obesity and endocrine glands, are features shared only

From Tom Verberne Robert Pool reports a “grand theory” of suicide (28 February, p 37), but his article rather misses the mark. A theory without any reference to what is known about the biology and the epidemiology of suicide is more grandiloquent than grand. Ilkka Henrik Mäkinen’s 1997 statement still stands: “Neither the individuallevel causes nor the general-level correlates of suicide have been clarified to a satisfactory extent” (Social Science and Medicine, vol 44, p 1919).

Rosanna, Victoria, Australia

Evolving backwards?

From Alex Nuan Though I much enjoyed the review of Jack Horner’s new book, How To Build A Dinosaur (28 February, p 44), I have to say I was a little disappointed that the reviewer, Jeff Hecht, continually made the common mistake of referring to a “reversal” or “rewind” of evolution.

Has he forgotten the number of evolutionists who are completely against the idea of evolution going any other way than forwards? Modifying a chicken to become more like a dinosaur would be less like making a traveller go back the way he came, and more like pointing him towards his original destination.

Nailsworth, Gloucestershire, UK

Significant figures From Terry Threlfall Regarding your calculations on the salt content of Walkers crisps, how can the one significant figure in 0.4 grams per pack lead to four significant figures in 4.444 grams per day (Feedback, 14 March)? We spend a lot of time explaining the significance of significant figures to students, and professionals need to set an example. The result of a calculation should not give more significant figures than were included in the input.

Upminster, Essex, UK The editor writes: ■ You’re absolutely correct.

Indeed, numerical accuracy is as important to the well-being of our youth as their salt intake.

Perhaps Walkers’ confounding statistics could be used in schools as an example.

Injelititis From Gerry Lynch Mark Buchanan’s reference to Parkinson’s law (10 January, p 38)

prompted me to read the entirety of C. Northcote Parkinson’s treatise where it originated.

Of particular significance is his ground-breaking discovery of “injelititis” – the chemical reaction within organisations when the concentration of incompetence and jealousy among senior management

reaches such a level that the whole organisation becomes moribund.

The illness seems to have been particularly prevalent among the banking industry’s nonexecutive directors.

Nutbourne, West Sussex, UK

For the record ■ Kairbaan Hodivala-Dilke works at the Institute of Cancer, Queen Mary’s School of Medicine and Dentistry, University of London (28 March, p 12).

■ Phil Rasch works at the Pacific Northwest National Laboratory in Washington state (21 March, p 6).

■ The DOI in our story about “baby butter” should have been 10.1016/j.ijpharm.2009.01.013 (28 March, p 15).

Letters should be sent to: Letters to the Editor, New Scientist, 84 Theobald’s Road, London WC1X 8NS Fax: +44 (0) 20 7611 1280 Email: letters@newscientist.com Include your full postal address and telephone number, and a reference (issue, page number, title) to articles. We reserve the right to edit letters.

Reed Business Information reserves the right to use any submissions sent to the letters column of New Scientist magazine, in any other format.

11 April 2009 | NewScientist | 23

OPINION INTERVIEW Photography: George Grassie

Journey to the heart of the universe Edward Witten, a leading architect of string theory, works at the cutting edge of mathematics and physics in his quest for a “theory of everything”. Matthew Chalmers met up with him to ask how it feels to work in an area so rarefied that it’s a problem simply conveying to other people what he’s up to LISTENING to Ed Witten talk physics can be a little unsettling. His concise sentences resemble steps in a logical proof: his grammar is flawless and his eyes occasionally close as he translates the great sweep of knowledge that has earned him exospheric academic status. This softly spoken man leaves you in a state of mental disarray.

This year Witten is in Europe, on sabbatical at the CERN particle physics lab near Geneva in Switzerland, where the mathematical foundations of reality are about to be rocked by the Large Hadron Collider (LHC). As it happened, he turned up on the day last September that the LHC switched on. “Ed’s very active, so it’s great to have him around,” says Luis AlvarezGaume, head of CERN’s theory department.

“He’s a genius, it’s as simple as that.”

Such accolades haven’t secured Witten a plush office, as I discovered when I met him in his sparse accommodation at CERN. Nor does he appear comfortable with the effusive descriptions sometimes applied to him – such as the “world’s cleverest man” or “Einstein’s successor”. “Believe me,” he says, “I’m definitely no Einstein.” Yet these monikers are founded in more than mere hyperbole. For the PROFILE Edward Witten has a BA in history from Brandeis University and a PhD in physics from Princeton University. He is now Charles Simonyi Professor of mathematical physics at the Institute for Advanced Study in Princeton. In 1990, Witten was the first physicist to win the International Mathematical Union’s Fields medal, and has won many awards, including the Einstein medal, Poincare prize, Dirac medal, and the Crafoord Prize in Mathematics.

24 | NewScientist | 11 April 2009

past 25 years Witten has been at the forefront of attempts to unify nature’s four fundamental forces in a single framework – a goal pursued for a similar period by Einstein. And he has been credited with writing the largest number of high-impact papers of any living physicist.

Witten’s quest – like Einstein’s – has been undertaken at the Institute for Advanced Study in Princeton. Einstein failed, but Witten has a more sophisticated toolbox at his disposal: string theory, which attempts to explain all the fundamental particles and forces in terms of infinitesimal strings oscillating into six or seven dimensions beyond our familiar four dimensions of space and time. Witten has made numerous major contributions to string theory, most famously in 1995 after coming up with ideas which spawned a more general 11-dimensional framework called M-theory while on a flight from Boston to Princeton.

The 1980s and 90s were dotted with euphoric claims from string theorists. Then in 2006 Peter Woit of Columbia University in New York and Lee Smolin of the Perimeter Institute for Theoretical Physics in Waterloo, Canada, published popular books taking string theory to task for its lack of testability and its dominance of the job market for physicists.

Witten hasn’t read either book, and compares the “string wars” surrounding their publication – which played out largely in the media and on blogs – to the fuss caused by the 1995 book The End of Science, which argued that the era of revolutionary scientific discoveries was over. “Neither the publicity surrounding that book nor the fact that people lost interest in talking about it after a while reflected any change in the intellectual underlying climate.”

Not that Witten would claim string theory to be trouble-free. He has spent much of his career studying the possible solutions that arise when projecting string theory’s 10 or 11 dimensions onto our 4D world. There is a vast number of possible ways to do this – perhaps 10500 by some counts. But a decade ago what seemed like a problem became a virtue in the eyes of many string theorists.

Astronomers discovered that the expansion of the universe is accelerating. This suggests that what appears to us as empty space is in fact pervaded by a mysterious substance characterised by a concept dreamed up by Einstein called the “cosmological constant”.

Witten calls it the most shocking discovery since he’s been in the field. If this cosmological constant – which has a value ridiculously close to zero – was slightly smaller or larger, galaxies

For more interviews and to add your comments, visit www.NewScientist.com/opinion

During his stay at CERN, Ed Witten had hoped to see the first data from the Large Hadron Collider

“Witten fears that humans might not be smart enough to figure string theory out” could never have formed – at least, not as we know them. With so many 4D models generated by string theory, some are bound to have a small but non-zero cosmological constant, just as in our universe – and that, the argument goes, also fits with an idea from cosmology that our universe could be one in an infinite series of universes making up a “multiverse”. Witten is not entirely sold on this interpretation, but he does see it as an interesting one.

This is one issue the LHC won’t shed much light on directly, and Witten is unlikely to see any data at all from the collider during his

stay at CERN. Nine days after he arrived, just as the machine was about to produce its first collisions, an electrical fault closed it down for a year. Witten is clearly annoyed at having missed out.

His dream scenario is for the LHC to discover that the whole of fundamental physics breaks down at the extremely high energies generated in the collider. This would imply that nature is much more interesting than we have hitherto understood it to be, for instance containing large extra dimensions, and may help clear the way for a unified theory of nature’s four fundamental forces. At the very least, he hopes that the LHC will tell us why three out of these forces – described in spectacular detail by the standard model of particle physics – are so much stronger than gravity.

For Witten, the most appealing explanation

for this would be supersymmetry. This pictures each known particle as having a heavier cousin – which the LHC should be able to find. Since supersymmetry is also deeply entwined in string theory, its discovery would also suggest Witten is on the right track in his search for a unified theory of physics.

That’s the optimistic view, though, and Witten seems resigned to the possibility that humans might not be smart enough to figure string theory out. “String theory doesn’t do what people want it to do,” he says. Working at the forefront of high-level mathematics and theoretical physics, Witten sometimes produces results that are difficult to convey to other people. He views some aspects of his work as a labour of love that can’t be appreciated in the near term.

All this from an arts graduate who is not averse to taking a few hours off to watch tennis or the Super Bowl. Witten majored in history and then dabbled in economics before switching to mathematics and physics.

“I realised I had more talent in [maths and physics], but I wasn’t sure I wanted to follow it,” he says. Witten’s thesis adviser, David Gross, who won a share of the 2004 Nobel physics prize, recalls being awed by his student, but, like Witten, dislikes comparisons with Einstein. “Ability space is multidimensional,” Gross says. “Along some axes, such as abstract mathematics, Witten exceeds Einstein while along others Einstein comes out way ahead.”

Chiara Nappi, a theoretical physicist at Princeton University who has been married to Witten for 30 years – and is also on sabbatical at CERN – dismisses the comparison as totally outdated. “Techniques have advanced so much that it’s not conceivable these days to be able to do your work in a patent office in Berne,” she says.

So is Witten within reach of a unified theory? He says the discovery 10 years ago that neutrinos have mass is already possible evidence that three of the standard model forces are described by a “grand unified theory” at high energies. He reckons the most influential insights in string theory will come from the younger generation, but Nappi isn’t so sure. She cites a recent study showing that scientists in their 50s and 60s are at least as productive as those in their 30s, if not more so.

“We are planning to get a lot more work done now that the children have moved out,” she says. It’s a fearsome prospect: Ed Witten might just be entering his prime. ■ 11 April 2009 | NewScientist | 25

Earth calling

JOSEBA ELORZA

We know more about outer space than the planet beneath our feet, but an ambitious seismic project plans to change all that. Rachel Courtland investigates

26 | NewScientist | 11 April 2009

COVER STORY

G

ARY ANDERSON was not around to see a backhoe tear up the buffalo grass at his ranch near Akron, Colorado. But he was watching a few weeks later when the technicians came to dump instruments and insulation into their 2-metre-deep hole.

What they left behind didn’t look like much: an anonymous mound of dirt and, a few paces away, a spindly metal framework supporting a solar panel. All Anderson knew was that he was helping to host some kind of science experiment. It wouldn’t be any trouble, he’d been told, and it wouldn’t disturb the cattle.

After a couple of years the people who installed it would come and take it away again.

He had in fact become part of what is probably the most ambitious seismological project ever conducted. Its name is USArray and its aim is to run what amounts to an ultrasound scan over the 48 contiguous states of the US. Through the seismic shudders and murmurs that rack Earth’s innards, it will build up an unprecedented 3D picture of what lies beneath North America.

It is a mammoth undertaking, during which USArray’s scanner – a set of 400 transportable seismometers – will sweep all the way from the Pacific to the Atlantic. Having started off in California in 2004, it is now just east of the

”It is our Hubble Space Telescope – with it we can view Earth in a fundamentally new way” Rockies, covering a north-south swathe stretching from Montana’s border with Canada down past El Paso on the TexasMexico border. By 2013, it should have reached the north-east coast, and its mission end.

Though not yet at the halfway stage, the project is already bringing the rocky underbelly of the US into unprecedented focus. Geologists are using this rich source of information to gain new understanding of the continent’s tumultuous past – and what its future holds.

For something so fundamental, our idea of what lies beneath our feet is sketchy at best.

It is only half a century since geologists firmed up the now standard theory of plate tectonics.

This is the notion that Earth’s uppermost layers are segmented like a jigsaw puzzle whose pieces – vast “plates” carrying whole continents or chunks of ocean – are constantly on the move. Where two plates collide, we now know, one often dives beneath the other. That process, known as subduction, can create

forces strong enough to build up spectacular mountain ranges such as the still-growing Andes in South America or the Rocky mountains of the western US and Canada.

In the heat and pressure of the mantle beneath Earth’s surface, the subducted rock deforms and slowly flows, circulating on timescales of millions of years. Eventually, it can force its way back to the surface, prising apart two plates at another tectonic weak point. The mid-Atlantic ridge, at the eastern edge of the North American plate, is a classic example of this process in action.

What we don’t yet know is exactly what happens to the rock during its tour of Earth’s interior. How does its path deep underground relate to features we can see on the surface?

Is the diving of plates a smoothly flowing process or a messy, bitty, stop-start affair?

USArray will allow geologists to poke around under the hood, inspecting Earth’s internal workings right down to where the mantle touches the iron-rich core 2900 kilometres below the surface – and perhaps even further down. “It is our version of the Hubble Space Telescope. With it, we’ll be able to view Earth in a fundamentally different way,” says Matthew Fouch, a geophysicist at Arizona State University in Tempe.

The combined effect of USArray’s 400 seismic stations is to measure vertical and horizontal vibrations in the ground more comprehensively than ever before. Each one is housed in a dome-capped steel cylinder, similar in size to a basketball, which is buried sitting atop a 10-centimetre layer of concrete to prevent it floating to the surface in waterlogged ground. Solar panels above ground provide power, and from most sites cellular phone modems relay the seismometer data, which ends up at a coordinating centre in Seattle, Washington.

The stations are spaced roughly 70 kilometres apart in a more or less square grid. Each one remains in place for two years while stations are added further to the east.

When its time is up, technicians dig it up and transport it eastwards to a new location at the front of the array. College students on vacation scout out future sites and contact potential hosts like Anderson. A total of 1624 sites is planned, covering all 48 states, and if you have land you think is suitable, the project even has a website where you can propose it.

Remoteness and seclusion are musts: the seismometers are sensitive enough to pick up the rumble of pumps, wells, passing trucks, hydroelectric turbines and even the wind whipping off hilltop ridges. > 11 April 2009 | NewScientist | 27

Installation work snakes up and down the map with the seasons as technicians follow the best of the weather, installing stations in the colder north in summer and in the south in winter. Where the main array reveals regions of particular interest it can be augmented by a fleeter, more flexible array of over 2000 smaller stations providing shortterm, high-density observations.

Keeping USArray moving is no small operation. “There were quite a few people who said it couldn’t be done,” says Robert Busby, who manages the array for the operating consortium, Incorporated Research Institutions for Seismology (IRIS), from an office in Falmouth, Massachusetts. “A few years ago, I was one of them.” There is still the odd hitch: earlier this year, the solar panels of two stations in Idaho had to be dug out of 6 metres of snow, and on four occasions wayward bulldozers have decapitated the dirtcapped seismometers. Despite these mishaps, the average station is up and transmitting data 99 per cent of the time, Busby says.

Each station generates plots of sound waves arriving from all directions – the acoustic

calling cards of earthquakes, volcanic eruptions and even storms and ocean waves crashing on distant shores. That might not sound like much, but used in combination the plots are a mine of information on what lies beneath Earth’s surface. The way in which sound waves weaken, refract and twist within the Earth varies according to the temperature, pressure and composition of the rocks they pass through.

By assessing how long it takes vibrations to travel from an earthquake or another source to the array’s various seismometers, geophysicists can deduce the properties of the intervening material. If rocks transmit sound at speeds that are unusual for their depth, they immediately become interesting: it suggests that they originated somewhere else.

The kind of insight that this information can bring is illustrated by what we now know of the fate of the Farallon plate. The Farallon once underpinned an ocean to the west of America, but around 150 million years ago basalt bubbling up from the mantle drove a wedge between it and the Pacific plate further west, pushing it eastwards into the North American plate. It did not fare well in this encounter.

A new plume The Yellowstone National Park in the Rockies is one of the favourite US destinations for visitors attracted by its wildlife, majestic scenery – and above all its spectacular geothermal features, such as the Old Faithful geyser. Two-thirds of the world’s geysers lie within the park.

Geologists have known for some time that this unusual activity is the subdued signature of a “supervolcano” underneath Yellowstone, whose last outburst 640,000 years ago produced a crater a kilometre deep and blanketed the surrounding area in more than 2 metres of ash. But the source of that volcano’s heat has remained a mystery.

Now USArray has allowed us to pinpoint it, according to Richard Allen, a geophysicist at the University of California, Berkeley. His analysis of USArray data shows that Yellowstone lies directly above one of the gaps in the descending Farallon plate, allowing hot rock to well up unhindered from at least 1000 kilometres down. The plume probably punched this hole some 17 million years ago, when it lay beneath

28 | NewScientist | 11 April 2009

what is now Oregon. Since then, the plume has stayed anchored deep beneath the surface, while the overlying North American plate has tracked west, pulling Yellowstone into place above it.

Evidence of such plumes of mantle rock are most commonly seen at the ocean floor in places like the mid-Atlantic ridge, where deep material wells up to create rifts that separate plates and give rise to new crust. While hints of plumes have been found beneath Germany and elsewhere, “this is the first time a continuous plume has been shown coming up from great depth beneath Yellowstone”, Allen says.

It is not clear exactly how great that depth might be. But as USArray, which is currently passing over the region, moves on it should reveal more about the plume’s roots and how heat is transported to the surface. That could help us to assess Yellowstone’s past and what it might be capable of in the future – a mission given new impetus by a marked upsurge in seismic activity in Yellowstone in December 2008.

Caught between emerging rock and a hard plate, it was forced underneath North America, raising up the Rockies in the process.

Off the north-west coast of the US, in an area known as the Cascadia subduction zone, a last remnant of the Farallon, the Juan de Fuca plate, is still descending into the maw.

Smashing plates Cool, dense rock transmits sound waves faster than hot material, and small seismic arrays have previously caught glimpses of subducted Farallon material that had yet to reach the temperature of the surrounding mantle. These anomalous sightings appeared at various locations and depths – 400 kilometres below the surface in the western US, and deeper into the mantle near the eastern seaboard – but the connection between these fragments has till now been tenuous.

USArray has helped fill in the gaps. It has revealed new fragments of the Farallon that fit together like pieces of a puzzle (see diagram, opposite) and shown that its death was far from clean (Nature Geoscience, vol 1, p 460). As the plate subducted, it seems to have broken up repeatedly as it encountered a solid wall of old, stable material – the core of the North American continent being pushed in the opposite direction by material welling up far away to the east at the midAtlantic ridge. One fragmented slab of subducted rock slopes from the west coast to a depth of 1500 kilometres beneath the Great Plains of the Midwest. Another remnant descends independently further to the east.

Cracks thousands of kilometres long discernible in this rock are changing geophysicists’ understanding of the entire seismic process. “The Farallon plate has been torn apart along these zones,” says Guust Nolet, one of the authors of the Nature Geoscience paper, now at the University of Nice in France. “It’s very much against the standard textbook image of beautiful oceanic plates going down into the mantle all continuous.”

The finding might also shed light on one of the biggest mysteries of North American geology – the intense geothermal and volcanic activity around the Yellowstone National Park (see “A new plume”, left).

Another surprise is emerging from data being analysed by Fouch at Arizona State University. His number-crunching seems to indicate that a large drip of dense material from the underside of the North American plate is slowly sinking into the mantle beneath Nevada. “We think of subducting plates as >

America’s foundation As the band of seismographic stations making up USArray moves steadily eastwards, details of the underlying geological structures are emerging STUDY AREA

Farallon plate and Yellowstone Tectonic plates

As the descending Farallon plate collides with the westwards-moving mantle, it has broken up into two separate bands, revealed by anomalously cool rock (red areas). The volcanically active Yellowstone area lies directly above a gap in one of these bands that allows a plume of hot material to well up from the deep mantle

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Eastern seaboard - quake threat?

An area of anomalously low seismic velocities stretching parallel to the Appalachians from Georgia towards New England might be caused by a water-saturated weak point under pressure from the east. If it ever cracks, it could cause devastating quakes sometime in the future.

USArray will investigate from 2012

11 April 2009 | NewScientist | 29

”A mystery area on the US eastern seaboard could become a subduction zone, with frequent quakes” are between 25 and 40 per cent. As a result, the immediate region already boasts hundreds of seismometers, but further afield seismometer coverage is much sparser and knowledge of the risks correspondingly hazier.

USArray should change that – and not before time. By 2011, the array will be centred over the fault zone, and its northern end will be at the edge of the Great Lakes. “That should tell us something about how stresses could build up in a craton that looks otherwise stable,” says geophysicist Suzan van der Lee of Northwestern University in Evanston, Illinois. We will then be able to say whether New Madrid is unique, 30 | NewScientist | 11 April 2009

JOSEBA ELORZA

the only things that go down,” says Fouch, but the Nevada finding indicates it’s not that simple. Drips of dense material affect how heat flows in the Earth’s interior, and their presence could help to explain how the locations of seismic faults and volcanic activity have changed over time.

As USArray rolls on from the geologically active western states, it will enter the more stable territory of the North American craton, the ancient core of the continent that has been largely untouched by the convulsions of its peripheries. That could offer a look back further into the continent’s past – as well as a glimpse into its future.

One area of focus will be the Reelfoot rift, a rent in Earth’s fabric that extends some 200 kilometres south-west along the Mississippi valley, from New Madrid, Missouri, towards Memphis, Tennessee. More than 500 million years ago, rock began forcing its way up from the mantle beneath this area.

Had it continued it might have created a new rift valley, and ultimately a new ocean.

It didn’t. For reasons unknown, rifting failed, but that ancient drama still left its mark by creating the most seismically active area in the US east of the Rockies. Between December 1811 and February 1812, New Madrid was the scene of a succession of huge earthquakes, one of which was powerful enough to ring church bells in Boston, Massachusetts, more than 1500 kilometres away. The likelihood of a repeat event around New Madrid within the next 50 years has been estimated to be between 7 and 10 per cent; for a lesser, but still significant, quake the chances

or whether other parts of the central US look similar. “That scenario is a bit scarier,” she says.

Nolet agrees that the data could be an eyeopener. “It may very well be possible there are other rift zones that are quiet right now but could come to life again,” he says. USArray will provide only a snapshot in time, so will not predict when earthquakes will occur, but by telling us how the ground beneath us is structured, it might tell us which areas could be under stress, and which areas would be particularly vulnerable to shaking if an earthquake were to occur.

Over the far longer timescales on which geologists are accustomed to thinking, data from USArray may give us a hint of North America’s long-term fate. According to van der Lee, an important clue may lie in a 300-kilometre-wide channel of anomalous material that runs to a depth of at least 660 kilometres along the US eastern seaboard.

“Right now we have a fuzzy picture of this thing,” says van der Lee. “We need USArray to get a sharper image.”

She and her colleagues have raised the intriguing possibility that the mystery area is water-saturated rock that has risen from water-rich minerals held in the leading edge of the Farallon plate (Earth and Planetary Science Letters, vol 273, p 15). If so, it would represent a weak point in the otherwise firm undercarriage of the eastern US. As new material formed in the Mid-Atlantic Ridge continues to exert pressure on the North

American plate from the east, it would be a natural point for a break to occur. Rather than continue to push, material would begin to subduct down along this weak line.

That could be as dramatic an event as the Farallon’s subduction was in the opposite direction, triggering the formation of lava plains and volcanoes, and frequent, violent earthquakes. Within a few tens of millions of years, the relative tranquillity of the eastern US could be history.

Van der Lee speculates that these bursts of tectonic activity might be part of a larger see-saw pattern in the dynamics of some continents. Material subducting on one side of the continent could push watery rock in front of it, creating weak spots that ultimately help to trigger subduction on the opposite side.

No one who takes a long view of Earth’s history would bet against such apocalyptic scenarios. Whether our descendants will be around to witness them is another matter.

USArray’s director, Robert Woodward, has his sights set on more immediate concerns. He wants to build on the array’s success in the contiguous US and take it to Alaska in 2014 for either a five-year sweep of the state or a more focused study of particular areas of interest.

“I think everywhere we take the instruments we’ll learn something,” he says, “Even if we’re not 100 per cent sure what that is.” ■ Rachel Courtland is a reporter for New Scientist based in Boston

Seeing with sound What is it like to “see” the world using sonar?

Daniel Kish, who lost his sight in infancy, reveals all

I

am 6 years old and it’s my first day at school. The bell rings for recess and all my classmates run gleefully away. But unlike them I cannot see. At least, not with my eyes.

Instead, I click my tongue, listening for echoes from the wall to my left. I walk with my hands slightly outstretched to keep me from running into chairs that may have been left askew. I hear kids laughing and shouting through the open door, and by clicking I also hear the presence of the sides of the doorway in front of me. I go through it to the playground for the first time.

After a few steps, I stop to listen. I stand on a crack in the pavement that runs parallel to the building behind me. I click my tongue loudly and turn my head from side to side.

The way is open, shot through with scurrying voices, balls bouncing and shoes scampering to and fro. What is around me? How do I get there? How do I get back?

Clicking my tongue quickly and scanning with my head, I move cautiously forward, catching fleeting images of bodies darting hither and thither. I follow spaces that are clear, avoiding clusters of bodies, keeping my distance from bouncing balls. I am not afraid – to me, this is a puzzle. I turn my head and click over my shoulder. I can still hear the wall of the building. As long as I can hear that, I can find my way back.

The ground slopes downward very gradually. As I continue, the sounds in front of me take on a softer hue, suggesting there’s a big field of grass ahead. Eventually my feet find the grass. I speed up now I’m out of the press of darting bodies and flying projectiles.

Suddenly, there is something in front of me.

I stop. “Hi,” I venture, thinking at first that someone is standing there quietly. But as I click and scan with my head, I work out that the something is too thin to be a person.

I realise it is a pole before I reach out to touch it. I click around me, and just barely hear something else. Leaving the pole, I move toward this next thing. I hear that it is also a pole just like the first. I detect yet another one, and another. There are nine poles all in a line.

I later learn that this is a slalom course, and while I never attempted to run it, I practised my biking skills by slaloming among rows of trees, clicking madly.

At this point a buzzer goes off. I scan around me, clicking my tongue, but I can’t hear the building. I clap my hands. I hear something, from the same direction that all the other kids are running in. Later, as I got to know the playground, I would run, too. As I move forward, clicking and clapping, I can hear a wall in the distance getting nearer, louder.

Kids are lined up in front of the wall, but I don’t know which class is mine. I ask, and > 11 April 2009 | NewScientist | 31

”My way is by clicking my tongue and listening for the patterns of reflections. By doing this, I can get 3D pictures”

someone points me in the right direction.

Clicking and scanning once more, I find the end of my line. As we enter the classroom, I click to make sure I don’t run into anyone.

Sensing I’m the right distance from the wall in front of me, I reach to my left and find a desk with a braille writer on it. I take my seat, wondering just how big the playground is and if it has a slide. I will find that out next recess.

At the time I went to school, blind kids either waited for people to take us around, or we taught ourselves to strike out on our own. My way was by clicking my tongue and listening for the patterns of reflections from objects around me. By doing this, I could get 3D images of my surroundings.

I can’t remember when or how I first started using sonar, because it was when I was very young. I have a memory of climbing over the fence into the neighbour’s yard and clicking to find out what was around me, when I was just 2½ years old.

As a child, while I was pleased to have a guide when someone was willing, I could do a lot by myself. I could ride a bicycle through my neighbourhood in the Los Angeles area, play tag with my friends, find trees to climb, and walk just about anywhere on my own.

For this, I thank my parents. I was presented with most of the opportunities that sighted kids enjoyed, and it was really just 32 | NewScientist | 11 April 2009

assumed that I would work things out.

I am certainly not the first person to teach myself echolocation. In fact, human sonar has probably been around for as long as humans. There are two types of sonar: passive and active. Passive sonar exploits sounds made for other purposes to get a sense of the environment, and everyone does it to some extent. We can hear our voice change depending on the kind of space we are in, for instance.

Humans probably used to rely on echolocation far more in the days before artificial lighting, when we had to find our way round in the dark. The readiness with which people learn sonar suggests to me it may be an inbuilt skill.

The first documented case of a blind

ECHOLOCATION FOR BEGINNERS ■ Close your eyes, and have someone hold a small bowl or open box in front of your face.

Speak. Listen to how your voice sounds hollow.

(You may not be able to tell with a tongue click unless you’ve practised a good deal.) Try it with and without the box.

■ Next, try this with a larger box or a pot. Hear how your voice sounds deeper.

■ Try with a pillow or cushion, and notice how your voice sounds soft instead of hard.

■ Try going to a corner of a room, and hear how your voice sounds hollow when you’re facing the corner. How does the sound change when you face away from it?

person using sonar dates back to the mid-18th century. The French philosopher Denis Diderot wrote in 1749 of a blind friend so sensitive to his surroundings that he could distinguish an open street from a cul-de-sac.

In the 19th century, the famous “Blind Traveller”, James Holman, was reported to sense his surroundings by tapping his stick or listening to hoof beats.

At the time, no one understood the basis of this skill. Some thought it relied on the skin on the face and called it “facial vision”. Only in the 1940s did a series of experiments prove this ability relies on hearing echoes.

Echoes can be used to perceive three characteristics of objects: where they are, their general size and shape and, to some extent, what they are like – solid versus sparse, sound-reflective versus sound-absorbent.

This allows the brain to create an image of the environment.

For example, I perceive a parked car as a large object that starts out low at one end, rises in the middle and drops off again. The difference in the height and slope pitch at either end helps me identify the front from the back end; typically, the front will be lower, with a more gradual slope up to the roof.

Distinguishing between types of vehicles is also possible. A pickup truck, for instance, is usually taller, with a hollow sound reflecting from its bed. An SUV is usually taller and sounds blockier.

A tree has narrow and solid characteristics at the bottom – the trunk – broadening and becoming more sparse towards the top. More specific characteristics, such as the size, leafiness or height of the branches, can also be determined.

Artificial echolocation Human echolocation is limited by our hearing: the detail we can detect depends on the wavelength of sound.

Ultrasound can reveal 10 times as much, which is why many groups over the years have tried to develop echolocation systems for blind people based on ultrasound, such as the UltraCane and the K-sonar.

Ultrasound devices can detect an object as small as a postage stamp from 5 metres away – but they can’t detect the side of a barn from 10 metres, because the range of ultrasound is so limited. Another

problem is conveying the ultrasound images to users, who must learn to interpret some form of coded aural or tactile feedback.

What’s more, these devices tend to be designed by engineers who don’t fully understand the problem they are trying to solve. For instance, blind people need to be able to move their cane around easily – you can’t pack it full of heavy gadgetry. For these reasons and more, artificial echolocation devices have never really caught on; every one has fallen by the wayside.

Passive sonar that relies on incidental noises such as footsteps produces relatively vague images. Active sonar, in which a noise such as a tongue click is produced specifically to generate echoes, is much more precise. My colleagues and I use the term FlashSonar for active sonar, because for us each click is similar to the brief glimpse of the surroundings sighted people get when a camera flash goes off in the dark.

FlashSonar Because an active signal can be produced very consistently, the brain can tune in to this specific signal. Even in complex or noisy environments, this allows for easy recognition of the echoes that are elicited. It’s like recognising a familiar face or voice in a crowd.

The characteristics of an active signal can also be changed to fit the situation.

For instance, I click more rapidly when moving fast, and more quietly in quieter environments so as not to get more information than needed. Large objects like buildings can be detected hundreds of yards away. Up close, objects about the size of a credit card can be detected.

FlashSonar struggles most with figureground distinction – distinguishing one object or feature from others around it. Elements tend to blur together, so it is not possible to recognise faces, for instance. Also, high noise levels or wind can mask echoes, requiring louder clicks and more scanning.

Nowadays, I spend part of my time teaching FlashSonar. I originally trained as a psychologist and later became the first fully blind individual in the US to qualify as an orientation and

mobility specialist, a job that involves teaching blind people how to get around.

After working in this area for several years, however, I felt that blind people were not generally trained to achieve as much as they could.

Instead, I developed my own approaches, helping blind students participate in a wide range of activities including solo bicycling, ball play, solo wilderness hiking – sometimes even competitively – or just to get around their community with greater ease and comfort. In 2001 I quit my job to set up the non-profit organisation World Access for the Blind, to make this approach available to blind people round the world. We work closely with families, helping blind children and adults to achieve everything they could imagine in a manner of their choosing, and also run workshops for instructors.

Although our programme has many facets, we are best known for teaching FlashSonar.

Its ability to give blind people a way to perceive their environment far beyond the reach of an arm or a cane is fast being recognised by people who work with blind people and in other disciplines. We are the first to develop a systematic, comprehensive way of teaching it.

We start by sensitising students to echoes, usually by having them detect and locate easy targets, such as large plastic panels or bowls.

Once they can do this, we move on to learning to recognise more complex echoes by comparing them to familiar ones.

For example, when facing a hedge, a student might say, “It sounds solid?” I might reply, “As solid as the wall to your house?” “No, not that solid,” she might say. “As sparse as the fence of your yard?” “No, more solid than that,”

she might answer. Now we have a range of relativity to work with. “Does it remind you of anything else near your house, maybe in the side yard?” “Bushes?” she might query. “But what seems different from those bushes?”

“These are sort of flat like a fence.” Ultimately, students verify what they hear by touching.

Besides training, we have also created prototypes of a device called SoundFlash. This is a head-mounted unit that produces highfrequency sounds modelled on bat chirps, but within the human audible spectrum. The intention is to produce a better sound for echolocation than we can make with our tongues. The results so far have been encouraging, with students able to detect three times as much detail at three times the distance as they can with a tongue click.

We have also worked with biologists trying to understand animals that perceive the world through echolocation, as well as with robotics researchers teaching robots how to navigate using sonar and with neuroscientists studying the imaging systems of the brain.

Ultimately, we aim to make our approach available to blind people throughout the world, so they can access opportunities and have a quality of life of their own choosing – with freedom and self-direction. By showcasing successful students in the media, we are changing expectations of what a blind person can do. It is our hope that we can help blind people step away from the idea that their perception of the environment need be limited to the length of a stick, or to someone else’s eyes. ■ For more information on echolocation, including videos, visit www.worldaccessfortheblind.org 11 April 2009 | NewScientist | 33

The future of Antarctica’s ice is written in its shocking past.

Douglas Fox meets the geologists drilling into history

Driller thriller 1000 km

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The East and West Antarctic ice sheets are very different in nature. By drilling deep underneath the Ross ice shelf, the Andrill team is reconstructing West Antarctica’s past

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34 | NewScientist | 11 April 2009

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SOURCE: NATURE, VOL 458, P 324

“There seems to be a lot more variability in the ice sheet than anyone pictured,” says Robert DeConto, a glaciologist at the University of Massachusetts Amherst. “That’s what’s so exciting about this. But it’s also kind of scary.”

Other ocean cores have been extracted from hundreds, and thousands, of miles north of here. They trace past changes in sea level by measuring ratios of oxygen isotopes in the layers of the cores. Since the ice sheets preferentially incorporate water molecules containing oxygen-16, spikes in the rock layers’ oxygen-16:oxygen-18 ratio pinpoint episodes when disintegrating ice sheets injected meltwater into the oceans.

Readings of these isotopic tea leaves reveal many spikes in sea level, from 5 to 30 metres.

But no one has figured out where on the meltwater fuelling any given spike came from – whether Antarctica, Greenland, or any of the other ice sheets that have sprawled over parts of Asia, North America and Europe.

That’s why Andrill’s record may be the most convincing. “What’s unique is that we’re drilling right next to the ice sheets,” says David Harwood, a palaeoecologist at the University of Nebraska-Lincoln and a founding member of the Andrill project. “So we can see the sea level come and go and we can see the ice sheets advance and retreat.”

The two Andrill cores come from a pair of holes drilled near the edge of a slab of floating ice called the Ross ice shelf, which hangs off the edge of Antarctica and bobs atop the Southern Ocean (see map).

If you want to reconstruct the history of West Antarctica, then the Ross ice shelf is a good place to start. It is the largest ice shelf on Earth, about the size of Spain and up to 700 metres thick in places. Five massive glaciers that flow off the edge of West Antarctica, 800 kilometres south of here, ooze into the Ross ice shelf, which buttresses the glaciers’ flow and slows their tumble into >

Depth (metres)

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HE midnight sun hangs low in the sky on this November evening. A plain of flat ice sweeps in all directions and mountains rise in the distance. Perched on the sea ice is a massive, teepee-shaped tent.

A mechanised rumble emanates from within.

Inside the tent, men in hard hats tend a rotating shaft of steel. This drill turns day and night through 8 metres of sea ice covering the surface of McMurdo Sound, off the coast of Antarctica, and through 400 metres of water beneath it and into the seabed.

It’s not oil these men are drilling for, but another precious resource – historical perspective that could help us to predict the future of sea level rise. Welcome to the Antarctic Geological Drilling project, or Andrill.

This international team is extracting two columns of stone from the sea floor. A few kilometres away, scientists at McMurdo Station, a US research base, work 24 hours a day to analyse them. The cores of stone are providing them with a record peering 19 million years into Antarctica’s history.

We know that Antarctica froze 35 million years ago, when its detachment from South America unleashed a circumpolar ocean current that isolated it from warmer parts of the world. What we do not know is whether its ice sheets have stayed frozen or melted and reformed many times since then.

It is an urgent question. Understanding how Antarctica’s ice responded to past climate swings will help us to predict how it will react as temperatures rise in the coming decades.

The mighty ice sheet covering West Antarctica could unleash enough water to raise sea levels by 5 metres were it to melt.

Andrill’s results reveal a breathtaking picture. They show how the West Antarctic ice sheet has collapsed and regrown at least 60 times in the past few million years. Andrill predicts that it could once again tip toward collapse by the year 2100.

11 April 2009 | NewScientist | 35

the ocean. West Antarctica’s ice sheet simply could not survive for long without the Ross and several other ice shelves stabilising its edges, says Douglas MacAyeal, a glaciologist at the University of Chicago. By drilling into the seabed here, the Andrill team believes they can reconstruct West Antarctica’s history.

Antarctica’s ice sheet is really two sheets that join together like a giant figure eight.

Glaciologists have good reason to believe that the smaller West Antarctic ice sheet is especially vulnerable to collapse. Most of the ice here slides across land that sits below sea level, at depths of 2000 metres in some locations. Without its ice, West Antarctica would appear on maps not as a substantial body of land but as an archipelago.

The ice sheet’s exposure to warming ocean currents means that parts of West Antarctica are already melting from underneath. Satellite surveys show it sweating 130 cubic kilometres of its ice per year, while East Antarctica’s ice sits high, dry, and largely intact.

”The West Antarctic ice sheet has collapsed and regrown over 60 times in the past few million years” Last year I visited McMurdo Station and dropped in on the stratigraphy lab, where scientists work around the clock analysing the Andrill cores. Sunlight slants in through the windows of the lab at 2 am, creating a false impression of late afternoon. Sections of the core a little narrower than a telegraph pole lie end-to-end on tables and half a dozen scientists are pouring over them.

“We do about 30 metres of core each night,” says Chris Fielding of the University of Nebraska, Lincoln. A new batch of core arrives here every night at 10.30 pm, by helicopter.

36 | NewScientist | 11 April 2009

For the next 2 hours I watch the night shift work. Fielding inches his way along the core, recording in his notebook the alternating layers of gravel conglomerate, mudstone and diatomite, a stone rich in the fossilied shells of marine micro-organisms called diatoms.

Layers of diatomite indicate times when the Ross ice shelf had retreated far away, allowing the ocean to teem with life. Gravelly conglomerates laid down on top of these layers show debris swept in by advancing glaciers, and a higher layer of diatomite shows the Ross ice shelf has once again retreated.

Around 3 am, Fielding looks up from the core, rubs his eyes, and says: “When I close my eyes I see conglomerate. After a long time, everything you see turns to conglomerate.”

At another table Sonia Sandroni, a petrologist with the University of Siena in Italy, sketches pictures in her notebook of marble-sized rocks suspended in the fossilised mud of the core: red pencil for granite, blue pencil for sandstone, and so on.

She has sketched 30,000 rocks this past month. Many are “dropstones”, carried by the ice shelf from hundreds of kilometres away and then plunked on the sea floor as icebergs calve off the ice shelf and melt. Sandroni and her colleagues match the minerals in these rocks to the places in Antarctica where they originated to provide a record of how patterns of glacial flow have changed over time.

Stones from far away indicate a robust Ross ice shelf channelling the flow of distant glaciers toward the drill sites. Stones from nearby indicate an absence of the Ross ice shelf. And a total absence of dropstones reveals times when the glaciers retreated so far they no longer calved icebergs into the ocean.

Other scientists in the room catalogue fossils of shells, worms, and tiny amoeboid creatures called foraminifers. Identifying the species reveals not only the prevailing climates when the critters lived, but also

PTER DUNBAR/NSF

PETER WEST/NSF

The Andrill team can tell how the Ross ice shelf (left) once looked by analysing ancient rock cores drilled from deep underneath (right)

how much sea ice covered the ocean.

The scientists work till morning. At 8.30 am, Fielding presents a slide show of photographed fossils and stripy sediment layers from last night’s core to two dozen freshly awakened scientists. He departs for dinner and bed, leaving the day shift to examine the core until evening. At 10.30 pm another 30 metres of core will arrive and the cycle will begin anew until the team has examined all 1100 metres.

Shape of things to come The Andrill team has focused on a period of time called the Pliocene, from 5 million to 2 million years ago. The 2007 report from the Intergovernmental Panel on Climate Change cites the Pliocene as an important analogue to climates that Earth might see as it warms in the coming decades. Global temperatures during that time peaked at 3 0C to 5 0C warmer than today – temperatures that the IPCC predicts could return by the year 2100. That warmth was driven by higher levels of carbon dioxide in the atmosphere.

Harwood, Fielding and 50 other scientists have detailed their findings from this critical period in a paper in Nature last month (vol 458, p 322). The cores show at least 60 cycles of glacial collapse, retreat, and re-advance during the last 14 million years, with 40 of them occurring during the early Pliocene. “It was spectacular,” says Timothy Naish of Victoria University of Wellington in New Zealand and Andrill’s scientific director. “To see the physical evidence for what we had suspected from other information was pretty exciting.”

The big deglaciations seen by Andrill also line up with rises and falls in sea level read from ocean cores drilled in other parts of the world.

Together the results show that expansions and collapses of the West Antarctic ice sheet really were helping to drive changes in sea level.

But most striking of all is a 60-metre

High, dry and cold At first glance, Andrill’s results would seem to contradict some climate observations taken nearby. Take the Olympus mountain range, located in a frigid corner of East Antarctica just 100 kilometres from the Andrill sites.

Some of the glaciers buried beneath rocks here are more than 7 million years of age – dated from the ages of the volcanic ash lying on top of them – making this the oldest known ice on Earth. So cold is the ice here that it never melts, though it does gradually evaporate.

Freeze-dried bits of tundra protruding from the gravel are dated at 14 million years. None of these features would have survived had summer temperatures consistently warmed

segment of deep green diatomite in the core, laid down 4 million years ago. This shows the Ross sea continuously free of an ice shelf and brimming with life for 200,000 years.

Compare the climate conditions of the Pliocene with those predicted for the next few decades and the implications are unmistakable.

“We know that CO2 was around 400 or 450 parts per million in the atmosphere, and there was no ice sheet on West Antarctica,” says Naish. “That’s where we’re almost at now. So it’s a really important window into what we’ll be facing in the next 100 years.”

The results are significant when you consider the IPCC’s latest report, published in 2007. Depending on the future climate scenario, the IPCC predicted sea level rises between 18 and 59 centimetres by 2100 – with Antarctic melting contributing little or nothing to those amounts. But these estimates omit some huge factors. While they predict increased snowfall in Antarctica, they fail to account for an opposing effect: the increased

above freezing in the last few million years.

So what gives? According to Boston University geologist David Marchant, East Antarctica need not contradict Andrill’s findings. The Olympus range sits high, dry, and inland, next to a plateau of bedrock that has almost certainly huddled beneath kilometres of ice for millions of years. The environment here is a world apart from that of the Ross ice shelf. “They’re both reflecting processes that are very different,” says Marchant. The key processes in the East Antarctic ice sheet and the Olympus range are atmospheric, he says, whereas changes in the West Antarctic ice sheet are largely down to the ocean.

loss of ice that could result from glaciers accelerating as their ice-shelf buffers around the edges of West Antarctica collapse.

The panel sidestepped these issues because the ice sheet models they would have used to calculate such effects had proved unreliable.

They successfully predicted snow fall and surface melting on ice sheets. However, they failed to predict factors such as warming ocean currents, thought to underlie the recent thinning of ice shelves and accelerations in ice loss observed since about 2000 in parts of Greenland and parts of West Antarctica.

Richard Alley is a glaciologist at Pennsylvania State University in University Park who helped write the IPCC section on sea level rise. Those older models’ biggest weakness, he says, “is this business of warm water getting at the edge of the ice sheet and triggering changes that propagate inward”.

Andrill will help fill this gap, says Alley.

Climate scientists validate their models by showing that they can reproduce what’s seen

A brief history of Antarctic ice 1,084,000 years ago

1,082,000 years ago

1,080,000 years ago

1,079,000 years ago

1,076,000 years ago

1,072,000 years ago

4000 3500 3000 2500 2000 1500 1000 500 0

1000 600 500 400 300 200 100 0

Metres

SOURCE: DAVID POLLARD AND ROBERT DE CONTO

Ice shelves

Ice above sea level

Improved computer models of the Antarctic ice shelves show how sea levels changed during a spell of warming about 1 million years ago

in palaeo-records drilled from sea floors and ice sheets. DeConto and David Pollard of Pennsylvania State University are now using Andrill’s record to do the same with a model that predicts ice sheet changes.

Their model of Antarctica’s ice sheets includes forces that most other models leave out, such as underside melting by ocean currents and rapid acceleration and thinning of glaciers when ice shelves collapse. In a Nature paper last month, they show that their model successfully reproduces the sequence of ice sheet collapses and expansions seen over the last 5 million years in the Andrill cores (vol 458, p 332).

They’ll soon run their model into the future and they expect it to predict more rapid ice loss than previous models have. “I think that the numbers over the next 100 years or so are going to raise a few eyebrows,” DeConto warns.

According to the Andrill cores, each collapse of the West Antarctic ice sheet happened over 1000 to 3000 years, seemingly placing any crisis far into the future. But even that slow collapse could translate into 10 to 50 centimetres of sea level rise per century.

Combine that with increased ice loss from Greenland and the sea level could rise to 50 or 100 centimetres by 2100 – the same amount predicted by another group at a climate change conference in Copenhagen last month.

To someone standing atop an ice shelf, the mischief that ocean currents are inflicting on its underside seems a world away. One day during my McMurdo Station stay, a group of us drives far out onto the Ross ice shelf for an overnight survival course. The ice shelf that we eat, sleep, and wield our ice axes upon seems as sturdy as bedrock. But if Andrill is right, the Ross ice shelf and West Antarctic’s ice sheet are nowhere near as timeless as they seem. ■ Douglas Fox is a writer based in San Francisco (www. douglasfox.org). His trip to Antarctica was funded by a US National Science Foundation grant 11 April 2009 | NewScientist | 37

A new generation of lasers could mean cheaper gadgets for all – if we can tame the weird cross-breed particles that power them, says Richard Webb

Loopy laser 38 | NewScientist | 11 April 2009

JOHN RENSTEN/GETTY

L

asers might be pushing 50, but they are still the youthful pin-ups of fundamental physics.

Since the first one was unveiled in 1960, the more apocalyptic predictions of how they might be used – as death rays, for example – have proved to be overblown. Their peaceful application, on the other hand, can be seen everywhere from cutting and welding to combating cancer and cataracts, to powering telecoms and consumer electronics, and has mushroomed into an industry worth $6 billion in 2007. Advances in the laser lab translate into gadgets in our homes at astonishing speed: think of the progression from CD to DVD and now Blu-ray technology in just a few decades.

So here’s a heads-up for you: we could be about to witness the next stage in the laser’s evolution, a sea change in how laser light is produced. A new wave of devices looks likely to exploit particle-like packets of energy to produce their light – packets that are neither light, nor matter, but both. It’s early days, but advances in taming these exotic beasts are proceeding apace. “I keep expecting progress to end,” says physicist Jeremy Baumberg at the University of Cambridge, one of the pioneers. “But it just keeps going.” The pay-offs could be immense: not just lasers that use less juice than ever before

and new low-power lighting technology but maybe even a way to make the semi-mythical, superpowerful quantum computer.

What is this new item in the physicist’s armoury?

The polariton, or exciton polariton, to give it its full name. How can such a particle be light and matter simultaneously? As is so often the case, the secret lies in the weirdness of quantum physics. Polaritons are not the kind of beasts you can expect to see in the wild. First bred in 1991 by researchers at the University of Tokyo, Japan, they spend the entirety of their short lives in tiny mirrored cages known as semiconductor microcavities.

The gestation of polaritons is a complex process.

It begins in a sandwich of semiconducting materials known as a quantum well. Electrons are jammed tightly into the thin, sheet-like filling of this sandwich – typically less than a micrometre thick – and so are particularly excitable. Add a little drop of energy, in the form of light or a voltage, and some of the electrons absorb it and jump to a higher energy level, leaving behind an absence of electrons – positively-charged “holes”. An electron-and-hole pairing is called an exciton, and is usually a short-lived affair: the energised electron soon gives up its extra energy and plonks itself back into the hole. At the same time it releases the energy it had taken on board, in the form of a photon of light.

This is where the cunning physics comes in. Place the quantum well between a pair of highly polished mirrors to create a cavity about 1 micrometre long, and now the photon will ping back into the

system to create another exciton, which in turn emits its energy as another photon. By carefully controlling the distance between the mirrors, the photons or light waves being emitted by many excitons can be made to build in intensity and resonate with one another, like the vibrations of a vigorously bowed violin string. This creates yet more excitons which produce more resonant light waves and so on, until energy begins to cycle between light and matter so fast – in just a few trillionths of a second – that according to the rules of quantum physics it becomes impossible to tell in which of the two states it is stored. And that is a polariton. Matter in the form of electrons and photons come together to make it, but its precise identity remains unclear. “You really get into a twist if you try to think of polaritons as half matter and half light,” says Baumberg. “They’re something completely different.”

And very odd characters they turn out to be. Take their mass, for example. Electrons are hardly the most heavyweight of particles, but compared with massless photons they are distinctly beefy. As a polariton contains a whole electron, you might expect its mass to be pretty close to the electron’s.

Not so. In fact, it seems to be only about one ten-thousandth the mass of the electron.

Or take the way polaritons behave in a group.

While electrons repulse their own kind, declining to exist in the same quantum energy states, polaritons are quite the reverse, liking nothing better than to get up close and personal by adopting a common, or “coherent”, quantum state. As a result, polaritons have proved themselves supremely adept at generating coherent laser light.

To a physicist, expecting polaritons to be able to generate laser light is an obvious leap of faith: the lasers in consumer electronic devices use similar >

COVER STORY

> 11 April 2009 | NewScientist | 39

materials and processes to those used to produce polaritons. Laser light is produced in a semiconductor quantum well by kicking electrons up into an energised state so that more of them are excited than not. The excited electrons then fall back down again, emitting photons of identical frequency and phase which can be focused into a coherent light beam.

This process is not helped by the electrons’ stand-offishness, which means that no two electrons will share the same quantum state.

So electrical engineers resort to brute force and pump in a substantial amount of energy – in the form of light or electric current – to force electrons upwards and thus kick-start the lasing process.

By comparison, lasing with polaritons may be a piece of cake. Just a small amount of energy should be capable of initiating a resonant transition between light and

So the search was on for an alternative semiconductor in which polaritons might feel more at home. It was soon found in a semiconductor based on gallium nitride, a material that has been used to make very bright blue laser diodes since the 1990s. The relatively small wavelength of blue light means it can etch information on a storage medium and then read it back again on much smaller scales than the infrared lasers used in CD and DVD technologies can. This is the secret behind the high-definition storage capabilities of Blu-ray discs.

In gallium nitride-based quantum wells, polaritons could be held stable even at room temperature. The problems were not solved yet, however. “Gallium nitride’s structure is far more disordered than gallium arsenide’s,” explains Jacqueline Bloch, who leads a group developing polariton lasers at the Laboratory of Photonics and Nanostructures in Marcoussis near Paris, France. That disorder makes it far more difficult to get light rattling around in the mirrored cage in the resonant way needed to induce polariton lasing. It sparked a major Europe-wide initiative to design semiconductor cavities that could confine photons better.

This finally paid off in 2007, when researchers at the University of Southampton and at the Swiss Federal Polytechnic Institute in Lausanne (EPFL) announced that they had induced polariton lasing in gallium nitride at room temperature – at a threshold energy just one-tenth of that needed in a conventional laser (Physical Review Letters, vol 98, p 126405).

This could be the breakthrough that industry is waiting for, Baumberg reckons. “Blu-ray

”Proof that polariton lasers work at room temperature could be the breakthrough industry is waiting for”

40 | NewScientist | 11 April 2009

Batteries are better Savvidis, now based in Greece at the University of Crete in Heraklion, has not given up on gallium arsenide in the meantime. He and his colleagues announced in May 2008 that they had produced an electrically driven polariton light-emitting diode (LED) in gallium arsenide that worked at a comparatively balmy temperature of 235 kelvin (-38 °C) (Nature, vol 453, p 372). A demonstration at room temperature followed in February 2009 (Applied Physics Letters, vol 94, p 071109). An LED is an intermediate step on the way to a laser, a low-intensity light source that does not demand the kind of coherent emission that lasers do. Once restricted to the standby indicators on televisions, LEDs are technologically important in their own right, however. As the intensities and range of

Polariton-based lasers may help reduce the cost of Blu-ray players

PAUL-WESLEY-GRIGGS/UNTITLED

matter. The polaritons created are only too happy to crowd into the same quantum state, emitting coherent laser light when they decay.

Experiments have not disappointed.

Baumberg led a group from the universities of Sheffield and Southampton, both in the UK, that in 2000 first demonstrated the promise of lasers using polaritons. By shining laser light into a quantum well at an angle carefully chosen to hit the confined electrons’ sweet spot, they found they could amplify the light and that this amplification increased exponentially as the power of the input laser was increased, reaching a factor close to 100 (Physical Review Letters, vol 84, p 1547). “It was a bigger light gain than in any known material,” says Baumberg.

Despite this spectacular start, the race towards practical polariton lasers has since encountered a few hurdles. Gallium arsenide was an obvious choice of material for the first experiments because it forms the basis of one of the best-developed families of semiconductor lasers, whose infrared light is used in hundreds of millions of CD and DVD players (see chart). Unfortunately, it turned out to be anything but ideal as an environment in which to nurture polaritons. The initial research of Baumberg and colleagues was done at ultralow temperatures of between 10 and 50 kelvin, but as soon as the thermostat was raised to anything approaching room temperature, increased thermal jiggling caused the polaritons to break up. “They were simply too delicate to survive,” says Pavlos Savvidis, who was a research student at the University of Southampton at the time.

technology is expensive because the gallium nitride lasers in it often fail,” he says. With a lower power threshold, polariton lasers promise better reliability, at a lower price.

Yet there is still a crucial hurdle to overcome before polariton lasers can break into the mainstream. All successful polariton lasing experiments so far have used light from another laser to kick-start the process. For consumer electronics, an electrical current is the preferred method. Working out how to build current-triggered polariton devices will be a fiddly business, says Bloch, as it will place even higher demands on the design of the microcavity. Nevertheless, her group and others tackling this challenge are optimistic of success within the next few years.

A rainbow of laser diodes

By carefully selecting the chemical elements used to make a laser diode, as well as their relative proportions, engineers can construct semiconductor lasers that emit at wavelengths from the blue to the infrared part of the spectrum, making them suitable for a variety of applications

Nanometres 405 nm – indium gallium nitrogen

Blu-ray disc systems and high-definition DVD drives

532 nm - aluminium gallium arsenic

Green laser pointers

635 nm - aluminium gallium indium phosphorous 650 nm - aluminium gallium indium phosphorous 670 nm - aluminium gallium indium phosphorous 780 nm - gallium aluminium arsenic 808 nm - gallium aluminium arsenic 980 nm - indium gallium arsenic 1064 nm - aluminium gallium arsenic

Red laser pointers DVD drives, laser pointers Red laser pointers Compact disc drives Compact disc drives Medical treatment Fibre-optic communication

1310 nm - indium gallium arsenic phosphorus 1480 nm -indium gallium arsenic phosphorus 1550 nm - indium gallium arsenic phosphorus 1625 nm - indium gallium arsenic phosphorus

colours available increase, they are rapidly Letters, vol 101, p 016402). In December spreading to all sorts of lighting applications 2008, Bloch’s group reported the first as a super-efficient alternative to traditional demonstration of polariton switching in incandescent bulbs. a gallium arsenide diode cooled to 10 kelvin The promise of polaritons does not end (Physical Review Letters, vol 101, p 266402). in power-saving light sources. According to A similar device could form the building block physicist Leonid Butov at the University of of a polariton transistor.

California, San Diego, they could be ideal In his lab at EPFL, Benoît Deveaud-Plédran candidates to take the place of electron is looking even further ahead. He thinks currents in a future generation of superpolaritons might point the way towards efficient computers. Conventional computers a workable quantum computer. Such a are adept at processing information but not computer would work by manipulating not so good at moving it about, he says. The currents of particles, but the properties of the pliability of electrons comes in handy when particles themselves. In particular, they would manipulating data on a silicon chip, but use quantum sorcery to entangle the states of transporting this data increasingly exploits the particles and transport information the zippiness of photons in optical fibres, between particles. rather than electrons in copper wires.

One scheme for creating these entangled Switching the information between electron particles involves the use of an exotic state of and photons and back again is a messy and matter called a Bose-Einstein condensate. time-consuming business – not helped by the Neither solid, liquid or gas, such a collection fact that it is difficult to make silicon emit of atoms behaves in the same weird quantum light. Here, the hybrid nature of polaritons ways as a single atom but on a larger scale, could come to the rescue. “Because you have making those properties much easier to a real particle in there with mass, you can observe. Unfortunately, such atomic Boseapply logic gates and actually control Einstein condensates only form within a polaritons,” says Butov. It would then be fraction of a degree of absolute zero, which relatively straightforward to extract the light makes probing their properties a tough ask, from the polaritons and use that to transport never mind harnessing them as a computer. the stored information. In July 2008, Butov In 2006, however, a team of British, French and colleagues published details of a and Swiss researchers announced something transistor – the basic switching element of a logic circuit – that uses excitons, the matter ”Polaritons could provide precursors of polaritons (Science, vol 321, a source of identical p 229). That same month, a theory paper photons, essential for detailed how something similar might be achieved with polaritons (Physical Review quantum cryptography”

Fibre-optic communication Pump for optical amplifiers Fibre-optic communication Fibre-optic communication

that mimicked the behaviour of a BoseEinstein condensate in a semiconductor cavity containing polaritons cooled to a slightly less frigid 19 kelvin (Nature, vol 443, p 409).

Crucially, calculations showed that because polaritons are much lighter than atoms, such condensation should also be possible at much higher temperatures – even at room temperature. “Bose-Einstein condensation is an extraordinary phenomenon with all sorts of crazy properties, such as superfluidity,” says Deveaud-Plédran, who was one of the team. “Doing that at room temperature would be something special.”

Deveaud-Plédran suspects that polariton condensates could offer some other useful advantages. With polaritons, you could produce entangled states in a solid material such as a semiconductor, manipulate the states – do computing – and then break them up and have the results of the calculation encoded in the light, he suggests. At the very least, Bloch says, polaritons should eventually provide a room-temperature source of identical photons – an essential resource for anyone developing encoding schemes for use in quantum cryptography.

Such suggestions are for the future, of course. Having witnessed how fast things have developed so far, no one is excluding any possibility. Baumberg certainly isn’t. “The polariton laser was the first thing I started working on as an academic, and it is the one thing I didn’t patent,” he says. “Now I’m thinking I should have done.” ■ Richard Webb is a features editor at New Scientist 11 April 2009 | NewScientist | 41

BOOKS & ARTS

Around the sun and back Using stunning artefacts, artwork and technology, two new exhibitions illuminate Galileo’s legacy references in the works of art on moon, the epicycles of the five view – notably the astronomical known planets, and eclipses. tapestry from Toledo cathedral In a particularly inventive touch, in Spain and the Linder Gallery many of the visual aids encourage Interior, a painting attributed to visitors to gaze upwards, where the studio of Jan Breughel the projections on the ceilings help Elder – are every bit as impressive them make sense of, for example, as their aesthetic qualities. the Babylonian and Assyrian views “Galileo” is an unapologetically “Visitors are encouraged didactic show, and makes to gaze upwards, to see profitable use of interactive the Babylonian and technology. For example, there is Assyrian views of the sky” a full reconstruction of the Greek Antikythera mechanism, the oldest complex astronomical instrument, of the sky, the medieval conception constructed in the 1st or 2nd of the zodiac and the differences century BC. It is accompanied between polar, equatorial and by a video showing the gearing gnonomic views of the sky. that allowed the display of the The impressive section on Islamic cosmology includes a small, Egyptian calendar, solstices and stunning 15th-century spherical equinoxes, phases of the sun and

Galileo: Images of the universe from antiquity to the telescope, Palazzo Strozzi, Florence, 13 March-30 August

WITH all the attention on Darwin this year, one could almost overlook the 400th anniversary of one of the most significant events in the history of science: the first time Galileo peered through his telescope and provided conclusive evidence that the Earth circles the sun. Two exhibitions are marking the occasion, though, both in conjunction with the Institute and Museum of the History of Science (IMSS) in Florence, Italy.

“Galileo, Medici and the Age of Astronomy” opens next month at the Franklin Institute in Philadelphia, Pennsylvania, featuring one of Galileo’s two surviving telescopes. Meanwhile, an expansive exhibition has just opened at the Palazzo Strozzi in Florence. “Galileo: Images of the universe from antiquity to the telescope” details the development of astronomy from ancient Egypt and Mesopotamia to Galileo’s new universe.

IMSS director Paolo Galluzzi has assembled a comprehensive visual guide to humanity’s notions of the heavens, drawing on clay tablets, frescoes, manuscripts, paintings and maps, as well as a remarkable range of scientific instruments, including Galileo’s other telescope. The sundials, astrolabes, armillary and celestial spheres and other devices on display are extraordinarily beautiful objects. For these alone, the show is a success. Meanwhile, the ingenuity of the cosmological The universe Galileo wrought infused the arts as well as the sciences 42 | NewScientist | 11 April 2009

BIBLIOTECA MARUCELLIANA/FIRENZE

Reviewed by Andrew McKie

astrolabe – the only known example of its kind. From there we see the Christianisation of astronomy: the addition of more complex epicycles to the Ptolemaic system in order to maintain Earth’s centrality and regular, circular movements of the heavens.

All that changed with Galileo.

His watercolours of the phases of the moon , a letter pointing out that Saturn appeared to have two small satellites, and his later diary observations of the satellites of Jupiter, testify to his empirical confirmation of Copernicus’s theories and the demolition of the geocentric universe.

Galileo famously came into conflict with the Church: his Dialogo was placed on the Vatican’s Index of Prohibited Books and he was called before the Inquisition and forced to abjure his views – a scene depicted in Cristiano Banti’s 1857 painting Galileo Before the Inquisition.

Whether Galileo ever uttered the apocryphal E pur si muove (“And yet it moves”), he was, of course, proved right. The power of his observations in supplanting religious ideology is best captured in a single arresting image: Galileo’s finger, detached from his remains in 1737, encased in glass and gilt and pointing heavenward. It is a scientific reliquary for a secular saint. ■ Andrew McKie is a freelance writer.

He was formerly the obituaries editor of The Daily Telegraph in London and is writing a history of death

MORE ONLINE For images from the exhibit, visit www.newscientist.com/topic/ books-art

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No contest

TATIANA KARAPANAGIOTI/MILLENIUM

Blogs bring a lively, personal feel to science, but they won’t replace journalism just yet

The Open Laboratory: The best science writing on blogs 2008 edited

by Jennifer Rohn, Lulu.com, $15.50 Reviewed by Michael Le Page

IS BLOGGING replacing the oldfashioned science journalism found in newspapers and magazines? Can science blogs do a better job than mainstream media? These questions have been much discussed recently, and a few bloggers are convinced the answer is yes and yes.

It was with these questions in the back of my mind that I read The Open Laboratory ,a collection of 50 blog posts chosen by a panel of judges from 520 submissions.

Series editor Bora Zivkovic seems to have no doubt that blogging is ultimately a force for good. “Small groups of people peddling misinformation are capable of… temporarily gaining

online prominence, but over time, the larger groups tend to prevail and ensure that true quality wins the day,” he writes. Really?

Take the most important scientific issue of our time, climate change. For the last two years, the “Best Science Blog” in the Weblogs Awards, which are based on readers’ votes, has gone to blogs by climate change deniers. Such blogs may be having an influence: polls show more and more Americans now think the threat posed by climate change is exaggerated even though denialism has become rarer in the mainstream media, with even Fox News finally embracing the truth.

While newspapers may indeed have an abysmal track record when it comes to reporting on science, many blogs out there are far worse. And people are generally drawn to blogs that reinforce their own views, not ones that challenge them. Overall, I suspect that the rise of blogging, far from improving people’s

knowledge and understanding of science, has made matters worse.

This, however, is not true of the blog posts selected for this book, which represent the cream of the crop. In this collection, there is no shortage of diverse and fascinating essays. Did you know that part of a late draft of On the Origin of Species was lost when the children of botanist Joseph Hooker scribbled over it? Or that spider monkeys have a “fingerprint” on the tip of their prehensile tail? And would you be prepared to live-blog your own vasectomy?

There are many highly entertaining pieces here, but also some less than engaging ones. Too many are mini-lectures, with no narrative or personal angle to sustain your attention. This kind of writing works for readers interested in specific areas, but will never draw a wider audience.

If these pieces really do represent the very best science writing on blogs, I’m afraid I have to agree with science blogger John Hawks: “If we’re going to compare the entire blogosphere with The New York Times, in terms of how much is worth reading for the average non-professional interested in science, the blogosphere is worse by an order of magnitude.”

Hellish times The End is Nigh: A history of natural disasters by Henrik Svensen, Reaktion Books, £16.95/$30 Reviewed by Catherine Brahic

NOT so much “The end is nigh”, more “The end has been nigh many times”.

Henrik Svensen tackles the topic of how natural disasters shape human society. Understandably, the interplay between religion and science is a prominent theme.

He describes, for instance, how 18th-century philosophers used

the destruction of Lisbon by an earthquake and tsunami in 1755 to debunk divine providence; yet the 1906 San Francisco quake is presented as a catalyst for Pentecostal revival in Los Angeles.

In fact, he says, the catholic church came up with the concept of natural disasters to describe the problems humanity faced as a result of original sin.

The book’s strength is its wealth of examples, some as recent as hurricane Katrina. But jumps in time and space are confusing. The most gripping parts are when geologist Svensen relates his own experience finding spontaneous subterranean fires in Mali.

Blasting the past Invented Knowledge: False history, fake science and pseudo-religions

by Ronald Fritze, Reaktion Books, £19.95/$29.95 Reviewed by Alison George

THE lost island of Atlantis, the discovery of America by a Chinese fleet in 1421 and the intelligent aliens who brought civilisation to Earth. How did these ideas enter the public consciousness, and why are so many people convinced they are true? In Invented Knowledge, Ronald Fritze makes a levelheaded and well-researched investigation into pseudoknowledge, revealing the tricks used by purveyors of false and sensational ideas. He also shows how attempts to debunk the myths can add fuel to the fire.

Fritze also relates how relatively benign ideas about lost continents mingle with more sinister racist ideologies and Nazi beliefs in a bogus version of European history. His main focus is false history and pseudo-religions, so I hope he will next turn his sharp gaze on homeopathy, the “detox” industry and pseudo-science.

11 April 2009 | NewScientist | 43

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BOOKS & ARTS

Photography: Heather Angel

Hot monkey heaven This photograph of Japanese macaques relaxing in a hot bath was taken on a winter morning by wildlife photographer and zoologist Heather Angel. The pool is in the Joshinetsu Kogen National Park, Nagano, Japan, in a place known as Hell’s valley because of its steep cliffs, dense forests and the boiling water that spurts from the frozen ground. It was built 30 years ago when it was discovered that the monkeys, like us, like to bathe in hot water.

44 | NewScientist | 11 April 2009

Japanese macaques – also known as snow monkeys – live further north than any other non-human primate.

Snow covers the ground in Hell’s Valley for four months of the year and temperatures often drop to -20 °C .

Thermal pools – both natural and man-made – help the monkeys survive the harsh climate.

Snow monkeys are not only renowned for their love of hot baths, but for using tools and washing their food. In 1953, an 18-month-old female called Imo was spotted

washing sweet potatoes to remove the mud before eating them. Ten years later the rest of the troop were also doing this, and had passed on the skill to the next generation. It was the first report of a learned tradition in a non-human species.

Angel has spent many hours observing snow monkeys and has noticed some other interesting habits. Like human children, the juveniles tend to leap straight into the water, submerging their heads, while the older ones climb in

sedately, keeping their heads dry.

If you want to see this for yourself, the best time to visit is early June when the mothers are with their newborn babies. Lucy Dodwell ■ You can find this and other photographs in Snow Monkeys by Heather Angel, Evans Mitchell Books

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FEEDBACK

recall an earlier unit of belief.

Apparently, colleagues of the physicist Robert Millikan – he of the classic oil-drop experiment to measure the charge on the electron – were inspired to create a unit to measure self-belief. Observing Millikan’s robust sense of his own worth, they concluded that the fundamental unit should be called the Kan. But since this is too large for computations involving more modest mortals, the practical unit we would measure our sense of our importance with would be the milliKan.

IF YOU want to buy some “liquid” zeolite, the place to look, David Compton discovered, is www. liquid-zeolite.eu, where bottles of the stuff can be bought for as little as €20 each.

Zeolite, the website tells us, is “nature’s detoxifier [which] protects you by actively removing the heavy metals and toxins from your body!” And it’s “100 per cent organic and natural”.

This all sounds a bit unlikely to us, and sure enough the word “quantum” – one of our surefire indicators of fruitloopery – pops up in the “What is Zeolite?” section: “Through a natural, proprietary process, concentrated quantum humic acid molecules have ‘naturally digested’ the zeolite, holding it in permanent suspension… Because the humic acid in liquid zeolite is in quantum, interdimensional form, and because the zeolite is actually suspended in the humic molecules, 100 per cent of liquid zeolite is carried into the cells…” And so on – there’s lots more. Hands up anyone who

can tell us what “quantum, interdimensional form” is.

David is unimpressed. He points out that none of the many zeolite minerals known are organic and that they are all solids, not liquids – and will remain so even if they are held in suspension. “How they could remove heavy metals from the body when consumed is a mystery,” he says. “The zeolite will stay in the gut and be excreted, so will have no contact with the bloodstream.”

To which we can’t help but add: if, by some route hitherto unknown to science, the zeolite does get “into the cells”, it will release toxic aluminium ions there. This can hardly be described as detoxifying.

FEEDBACK’s reference to the kiloSteve, a proposed unit in the sociology of science prompted by the news that 1000 scientists called Steve, or variations thereof, had declared their support for evolution (28 February 2009) led Hal Kouns to

The scissors Richard Briggs bought from Amazon came in a pack carrying the message: “To remove scissors from pack, carefully cut cable tie using scissors” 64 | NewScientist | 11 April 2009

ESCAPING from an electronics show in Las Vegas recently, a colleague of ours was able to explore one of the world’s biggest eco-mistakes. The Salton Sea is 1000 square kilometres of inland lake, created when the Colorado river flooded a southern Californian desert valley in 1905. In the 1950s, the “sea” was promoted as a Riviera-type resort, close to the luxurious golf courses of Palm Springs and an ideal

weekend escape from Hollywood.

In addition, thanks to lobbying by the late pop star-turnedpolitician Sonny Bono, the sea was made a nature reserve for huge flocks of migrating ducks and geese.

Unfortunately, evaporation and fertiliser run-off from the surrounding farmland have made the Salton Sea far more salty than the Pacific Ocean. On top of that, algal blooms periodically cause oxygen levels in the lake to plummet, leading to the mass deaths of huge numbers of tilapia fish that breed there. Soon after,

the shore stinks to high heaven, which drives people out of the decaying holiday towns built by “Riviera” speculators.

Politicians are now engaged in fierce debate over whether the federal government should spend a fortune on freshwater irrigation to save the sea and its ghost towns, or cut its losses and let the desert reclaim the valley.

Linda York, who runs a local wildfowl rescue centre, has an uncomfortable thought about the latter option. She told our colleague that it would cause the birds to fly on to Palm Springs, where they would spot the lovely green golf courses there and bury them under a mountain of droppings after eating all the grass. “And because most of the birds are protected species, no one will be able to do a darn thing to stop the destruction.”

A LIFE insurance advertisement that Elizabeth Cox came across in the UK magazine Radio Times extolled the policy it was promoting thus: “The full death benefit is payable after just one year. If you pass away within the first 12 months you may only get back the premiums you paid.”

“And there was I thinking my relatives would get it,” says Elizabeth sadly.

HOLIDAYING in Sarawak, Borneo, Jenny Narraway was puzzled by a sign announcing: “Amateur fatalist centre”. Her mental picture of a group of gloomy people sitting around sighing in an unprofessional manner was only partly dispelled when enquiries among Chinese acquaintances produced the information that it was “something to do with feng shui and fortune-telling”.

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THE LAST WORD Down in one Why is it so much easier to down, say, a whole pint of beer or orange squash in one go, compared with a pint of water?

■ Is it fair to suggest that the questioner’s preference for downing a pint of beer rather than a pint of water is dependent on individual taste?

I have never been able to down a whole pint of beer, much to my dismay – and not for want of trying! But I am able to drink a whole pint of water or more in one go, even if I do feel quite sick afterwards. I much prefer the taste of water to beer and I find it difficult to consume any fizzy liquids in large quantities.

I assumed that this was the case for most people, but obviously not.

Jayne Staines Eastbourne, East Sussex, UK ■ Is this just hearsay or is it the result of a well-designed experiment? I suspect the former.

Even so, a possible explanation could be that orange squash and beer have strong and pleasant flavours while water is bland, and that there is more motivation in a pub to persist with beer or orange squash than with water.

But surely it depends on context: if I were seriously dehydrated after some time in a desert, say, I would certainly prefer a pint of water to a pint of beer. In a pub, where one is not dehydrated, beer would be my preference.

So we need to establish whether

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the questioner’s proposition is really true (the clincher would be for non-drinkers to compare beer with another carbonated drink, such as cola) and whether it is true in a variety of contexts. If there is experimental evidence, then we can examine it and see if it was well designed and worth believing. Then we would need to find out why. This is the correct scientific response.

Mike O’Mahony Professor and sensory scientist Department of Food Science and Technology University of California, Davis, US

Clear waters After an electrical storm, the water in my father’s small fish pond is crystal clear, having previously been full of green algae. Similarly, my parents’ drinking water comes straight from a nearby reservoir and often contains organic matter, but a storm also appears to clean it up.

What could cause this?

ratio of algae to water would also decrease in this case.

Dan Mikos Cooperative Institute for Research in the Atmosphere Colorado State University Fort Collins, US

Think hard What is the storage capacity of the human brain in gigabytes? If we were to construct a PC with similar computational power to our brain, what would its technical specifications need to be?

■ We can only answer this question if we assume the human brain is like a computer. For example, if each neuron holds 1 bit of information then the brain could hold about 4 terabytes (4000 gigabytes).

However, each neuron might hold more than 1 bit if we consider that information could be held at the level of the synapses through which one neuron connects to another. There are about 50,000 synapses per neuron. On this basis, the storage capacity could be 500 terabytes or more. But these are perhaps misleading

■ Electrical storms are generally associated with heavy rain – this is where the answer lies. The additional rain adds water to the pond, giving a smaller ratio of “The human brain can algae to the amount of water. create more storage This will make it appear as if capacity by generating new there is less algae, even though synapses and neurons” the absolute amount of algae is probably constant.

Drinking water, too, commonly answers because the human brain contains organic matter when it is not like a standard computer. hasn’t rained for a long time.

First, it operates in parallel rather Following a heavy rainfall there than serially. Second, it uses all is a higher volume of water, so the sorts of data-compression

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routines. And third, it can create more storage capacity by generating new synapses and even new neurons.

The brain has many limitations, but storage capacity is not one.

The problem is getting the stuff in and, even more problematic, getting the stuff out again. We can demonstrate that storage capacity is not the problem if we consider the technique experts use to remember the order of a shuffled pack of cards. This technique, called the “method of loci”, goes back to classical antiquity. It involves imagining a journey in which each card appears at a certain location.

Here is an example that I found on the internet: the first card is an 8 of clubs. To memorise this you imagine going out of your front door, the first step on the journey, and finding your path blocked by a person smashing an egg timer (which is shaped like an 8) to pieces with a mallet (a club). The next card is then placed on the next step of the journey with an equally vivid image.

What is striking about this technique is that the story you create to remember the order of the pack of cards contains much more information than the simple pack of cards you are trying to remember. The vivid images are necessary to get the information into our brain and to get it out again later.

Chris Frith Wellcome Trust Centre for Neuroimaging University College London, UK