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GLOBAL BROWNING What’s muddying the world’s waters? FLASH OF INFORMATION Turning light bulbs into superspeed data hubs SMELL ME NOT Plants repel predators with booby-trap stink bombs WEEKLY 9 January 2016

THE MYTH OF BABY BRAIN How pregnancy supercharges a mother’s mind

STRANGERS WITHIN Meet the other humans

9 770262 407268

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who live in your body

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Volume 229 No 3055 This issue online newscientist.com/issue/3055



Black hole bubbles




Cosmic giants concealed entire universes

Double Negative team, TM & © Warner Bros. Ent Inc. (s15)). (CC BY-NC-ND 3.0)

On the cover


34  Global browning Muddying the waters 30  Flash of information Light bulbs to data hubs 12  Smell me not Stink-bombing plants 36  The myth of baby brain Pregnancy mind boost 8  Black hole bubbles Cosmic giants concealed entire universes

Strangers within Meet the other humans who live in your body

Global browning sounds comical but we need to take it seriously

6 UPFRONT  UK plans giant marine reserve in the Atlantic. NASA to build space sleeping module. Four new elements found. US gun crackdown 8 THIS WEEK Take a break, boost your memory. “Grow” your own IVF embryo. Guinea pigs tweak genes to beat climate. Plants’ smelly booby traps. Exomoons eaten by their planets. The young women facing down TB 11 Insight Climate change is behind UK winter flooding 16 IN BRIEF  Falcons imprison small birds. Hormone tames love of sugar. Huge galaxy shreds neighbour.

Technology 18 Microbe-made  ink. Wind power skin for houses. Robot that watches and guides you. Hacked smartwatch monitors for epilepsy

Aperture 22 Night-time mouse ninjas caught mid-fight


Cover image Martin Sati

24 Tipping the scales Paul Zimmet on a rare hopeful sign in a US public health battle 24 Mixing it Diversity in physics may yield our best crack at the cosmos, says Joshua Sokol 25  One minute with… Lukas Brud Why footballers should use wearable tech




The myth of baby brain

26 Strangers within (see above left) 30 Flash of information Turning light bulbs into superfast data hubs 34 Global browning What’s muddying the world’s waters? 36 The myth of baby brain (see left) Brett Ryder

Pregnancy supercharges a mother’s mind


Coming next week… Habits

40 A grown-up quest Did dark matter kill the dinosaurs? Who cares, it’s the tale that counts 41 No place like it Finding home in the brain 42 Close encounters Michael Madsen’s new film explores how aliens get under our skin

How brains make them... and how to break them


Searching for ET

52 letters Accounting for empathy 56 Feedback The protective power of tin foil 57 The Last Word Rumble of doubt

Seven bold ways to look for alien life

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Troubled waters Global browning can only be understood as part of a wider problem ANYONE remember global it might at first sound almost dimming? About 30 years comical – but like global dimming, ago, climatologists noticed it is anything but. All over the a disconcerting trend in the world, increased inflows of dead amount of sunlight reaching organic matter are making lakes Earth’s surface. Measurements and rivers murkier. The full soon confirmed their suspicions: extent of the problem is still across the world from the 1950s being assessed, but it is likely to onwards, sunshine had declined be bad news for wildlife. It is also by about 2 per cent per decade. bad news for humans, because it In some places, it was down by makes water purification more as much as 10 per cent. difficult and expensive. The culprit turned out to be Somewhat predictably, the air pollution – particularly small cause of global browning is also particles of soot and droplets “Even if we do find a way of sulphuric acid. People soon to tackle global browning, raised concerns that dimming who knows what the would hit agricultural yields and exacerbate climate change’s effect knock-on effects will be” on weather patterns. industrial pollution, although Global dimming was a real not in the form of smog. Instead, and serious problem, but smaller it is largely the unanticipated and easier to tackle than global consequence of another clean-up warming. As factories and power success story: the reduction of stations cleaned up their acts – acid rain (see page 34). at least with respect to smog That hangover will eventually and soot – dimming slowed and, dwindle, but browning also seems in some places, reversed. From about the mid 1980s onwards, the to be driven by climate change developed world has experienced itself. If so, it will be harder to tackle than global dimming. And brightening. As a result, little is if we do tackle it successfully, heard of global dimming in the there may be unexpected knockWest these days, although it remains a problem for many parts on effects – as there were with of Asia, Africa and South America. dimming. The pollutants in that case, while generally undesirable, Now there is a new pollution alleviated climate change by problem on the horizon: global reflecting sunlight back into space. browning. Like global dimming,

All of this is a useful reminder that the environment is made up of complex and interconnected systems. We like to put environmental issues into neat silos: global warming, global dimming, global browning, ocean acidification. But they are all manifestations of a single underlying problem: treating the atmosphere as an open sewer. At least countries seem to be belatedly pulling together to do something about the core problem. Last year’s Paris deal on climate change was better than many had hoped, albeit mostly fine words rather than firm actions. And there is now widespread acknowledgement that the record rainfall and unprecedented flooding that have swamped the UK over the past month were exacerbated by climate change (see page 11). There is a huge amount of work still to do and worrying signs of a resumption of business as usual. As always, the scale and complexity of the challenge makes it hard to grasp and harder still to rise to. But if we need a symbol of how urgent and interlinked our environmental problems are, we could do a lot worse than an image of brown floodwater under a leaden sky. n 9 January 2016 | NewScientist | 5

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doug mills/nyt/redux/eyevine


Tighter gun control IT’S been a long time coming. On Monday, US President Barack Obama issued a set of proposals that aim to reduce gun violence in the country. The proposals follow a bloody year that saw 330 mass shootings. Currently, anyone who wants to buy a gun from a licensed store must pass a background check. Their details are run through a national database – if they have a record of domestic violence or some other crimes, or have been involuntarily committed to a mental health institution, they can’t buy the weapon. But loopholes exist: if it takes longer than three days to run the checks, the person is free to purchase the gun, and the federal law doesn’t apply to sales at gun shows or to private sales.

Obama aims to close these loopholes, requiring anyone who sells a gun to carry out checks. He also wants the national database to include more information on mental health. This will probably mean clinicians reporting their patients’ mental health status. Last year, eight health bodies urged lawmakers not to pass such legislation, stating that the move would only stigmatise mental illness for little gain – less than 5 per cent of violent gun crime is committed by people with mental illness. The organisations also called for better mental healthcare, and here, Obama is on the same page – his administration is proposing an investment of $500 million to improve access to treatment.

Exported emissions

DOI: 10.1098/rsif.2015.1001). Soya, cocoa and wheat take up the most foreign land, while fruit and vegetables are increasingly sourced from Spain and other countries. In 2008, 21.9 megatonnes of greenhouse gases were linked to UK food supply. Of this, 18 per cent was emitted in South America, and 15 per cent in the European Union. “If we want to reduce the impact of our food consumption, it’s not enough to only look at domestic production,” says report co-author Henri de Ruiter at the University of Aberdeen.

–Obama is listening–

Four new elements

ununoctium (Uuo). The last time new elements made the grade was in 2011, with the addition of flerovium (114) and livermorium (116) to the periodic table. “The chemistry community is eager to see its most cherished table finally being completed down to the seventh row,” said Jan Reedijk, president of IUPAC’s inorganic chemistry division. The creation of superheavy elements puts theories of atomic structure to the test, and might one day produce stable elements with odd properties.

TIME to rip up those posters of the periodic table. Four new elements now complete its seventh row. The International Union of Pure and Applied Chemistry (IUPAC) and the International Union of

Pure and Applied Physics have recognised the discoveries of elements 113, 115, 117 and 118. They are the handiwork of teams in Japan, Russia and the US, who smashed lighter nuclei together. The resulting superheavy elements exist for only a fraction of a second before decaying into lighter atoms. Their discoverers will be invited to propose names for these elements, based on mythology or the names of minerals, places, properties of the element, or scientists. For now, they have placeholder names and symbols: ununtrium (Uut), ununpentium (Uup), ununseptium (Uus) and


“The creation of superheavy elements puts theories of atomic structure to the test”

NOT much is growing in the UK – except its carbon footprint. The global impact of feeding the country has been estimated for the first time, revealing that 64 per cent of associated greenhouse gases are emitted abroad. The UK now imports over half its food and animal feed. Between 1986 and 2009, the amount of land used to grow the country’s food increased by 23 per cent, with 70 per cent of it located overseas (Journal of the Royal Society Interface,

Loft in space TRIPS to Mars call for a bit of legroom. NASA’s latest budget, passed by US Congress last month, includes $55 million to develop a homely craft suitable for crewed deep-space missions, such as a potential Mars voyage. Congress says that NASA should “develop a prototype deep space habitation module” no later than 2018, for use with the Orion spacecraft and SLS rocket system –Cat-swinging not advised– now being developed. Orion is

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For new stories every day, visit newscientist.com/news

The pill, no problem

designed to carry astronauts into deep space, but it is little bigger than the Apollo capsule in which astronauts spent a week during the moon missions. Its cramped conditions would make an 18month Mars mission hard to bear. Although NASA has, over decades, built up many designs for modules similar to those on the International Space Station, giving astronauts more room, it’s not yet clear if any of these will be dusted off and put to use. NASA has 180 days after the president approves the budget to report back to Congress on its progress.

WOMEN in Oregon can now pick up the pill at their local pharmacy, bypassing their doctor. The state has become the first in the US to provide over-the-counter birth control. California is set to implement a similar law in March. As of 1 January, pharmacists who receive extra training can assess a woman’s suitability for hormonal contraception and supply the pills or patches. The move should make it easier to access contraception, says Jordan Conger, who represents Knute Buehler, the Oregon

60 Seconds

representative who proposed the law. He points to a study by the University of California, San Francisco, which estimated that around a quarter of women who don’t take the pill would start if it were available via pharmacies. When the UK’s National Health Service piloted a similar scheme at London pharmacies in 2012, it found demand for emergency contraception dropped drastically at the pharmacy that provided the most contraception. What’s more, improving access could reduce unintended pregnancies, says Chris Smith at the London School of Hygiene and Tropical Medicine.

Ascension fishing clampdown

All steamed up

Prisma Bildagentur AG / Alamy Stock Photo

“VAPING ‘no better’ than NO FISHING here. The largest marine protected area in the Atlantic Ocean smoking”: headlines last week challenged the idea that electronic might be established around the island of Ascension, a UK territory cigarettes are safer than normal halfway between Brazil and Angola. ones, after findings emerged that Commercial exploitation of their vapour damages and kills Ascension’s waters is carried human cells. out by foreign boats using very Although the study attracted unsustainable methods, says Clare global attention, it has been Brook, head of the Blue Marine criticised for its inability to Foundation, which has been properly compare the damage campaigning to protect the area. caused by smoke and vapour. Following a £300,000 donation to To assess what vaping does fund patrols, half the proposed area to human tissue, a team at the University of California, San Diego, is to be closed to commercial fishing, with the other half seeing strict rules exposed cells to e-cigarette vapour intended to reduce the unwanted every three days for one to eight bycatch of turtles, sharks and weeks, and compared them with dolphins, and banning shark finning. unexposed cells. However, they Sports fishing will still be allowed. were unable to compare the effect of cigarette smoke on cells for the same amount of time because the cells always died after 24 hours (Oral Oncology, doi.org/bbmj). This suggests that the study’s main outcome is actually that cigarette smoke is more toxic than e-cigarette aerosol, says Konstantinos Farsalinos of the University of Patras in Greece. “Those of us reviewing the evidence are saying that when compared with tobacco smoking, e-cigarettes are a safer option, and I don’t think this detracts from that,” says Linda Bauld of –Protected waters?– the University of Stirling, UK.

If successful, it is hoped that the area will become an officially designated marine protected area, spanning as much as 250,000 square kilometres. Whether this goes ahead is likely to depend on whether the island’s economy can benefit more from protecting its waters than from selling fishing licences, says Brook. Besides paying locals to patrol the protected area, she hopes scientific expeditions will provide another source of revenue. “This is a wonderful step forward for conservation of Atlantic marine life,” says marine biologist Callum Roberts at the University of York, UK. “The island is one of the most important remaining strongholds for life in a very intensively fished ocean.”

Storms hit California Here comes the rain. El Niño storms have begun to drench California and are forecast to continue for around two weeks. The deluge should provide some relief from the state’s record-breaking four-year drought.

The apps of war Facebook deliberately broke its Android app this week, to test the dedication of users in preparation for potential war with Google, according to The Information website. Facebook was afraid that Google might gain an advantage by curtailing its app on the Android operating system, says the report. It found that no matter how broken the app, people still came to the site via mobile browsers.

VW up against the wall The lawsuits begin. The US Environmental Protection Agency is suing Volkswagen for fitting some of its cars with software to cheat emissions tests. This was installed in 11 million vehicles worldwide, and the manufacturer is already facing criminal charges and a number of class actions filed by car owners.

UK doctors say no Junior doctors in the UK plan to strike for 24 hours on 12 January, following the collapse of pay negotiations over antisocial hours. It will be the first full walkout in the 68-year history of the National Health Service, and the first industrial action in 40 years by junior doctors, who make up half of NHS doctors.

Mexico’s gains slain The high murder rate in Mexico is taking its toll. In the second half of the decade to 2010, life expectancy for men fell by 6 months, after rising from 72 to 72.5 years in the first. In northern states blighted by gang violence, it dropped by three years, mainly thanks to an uptick in violence after the 2006 government crackdown (Health Affairs, DOI: 10.1377/hitaff.2015.0068).

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This week

The hole wide multiverse BLACK holes may be hiding the smallest particles, played other universes. A quirk of an important role in how all of how space-time behaved in space-time evolved. the early universe could have One of these effects was that a led to short-lived wormholes small patch of space-time within connecting us to a vast multiverse. the larger universe could shift If borne out, the theory may into a different quantum state, help explain how supermassive forming a bubble. Such bubbles black holes at the centres of could form at random throughout galaxies grew so big so fast. our inflating universe. The idea that ours is just That means that even after one of a staggering number of rapid expansion ended in our universes – what cosmologists call cosmos, a number of bubbles the multiverse – is a consequence “Our universe could even of our leading theory of how the look like a black hole to universe grows: eternal inflation. The theory holds that during its physicists in some other early phase, space-time expanded universe” exponentially, doubling in volume every fraction of a second before could keep inflating into their settling into a more sedate rate own baby universes. Each of these of growth. Eternal inflation was would give rise to other bubbles, devised in the 1980s to explain spawning a sprawling multiverse. some puzzling observations “While inflation is going on, about our universe that bubbles can pop out and expand standard big bang theory in this inflating space,” says alone couldn’t handle. cosmologist Alex Vilenkin of But cosmologists soon Tufts University in Medford, realised that the inflationary Massachusetts, one of the pioneers universe came with caveats. of inflationary cosmology. Quantum mechanical effects, But proof has been hard to which normally only influence come by. Cosmologists have

Information lost and found Black holes pose a conundrum: in gobbling up matter, they also gobble the information it encodes. Quantum mechanics says that information cannot be destroyed, but Stephen Hawking famously showed that black holes emit radiation and eventually evaporate. So where does the information go? Hawking and his colleague Jacob Bekenstein suggested that the information comes

out in the radiation. But accepting this idea leads to other problems – such as the formation of a blazing firewall at the horizon of the black hole, something prohibited by Einstein’s general relativity. Now we think black holes may hide entire universes beyond their horizons – worlds away from what we normally assume lurks beneath their surface (see main story). This may drive physicists to revisit the information loss paradox.

suggested that bubbles colliding with our universe could have left imprints in the cosmic microwave background, the leftover radiation of the big bang. However, such a signal would be very faint, and no conclusive evidence has yet been seen. Vilenkin and his colleagues wondered if they could spot signs of the multiverse elsewhere in our universe. To investigate, they did a mathematical analysis of the fate of the bubbles formed during inflation. They found that bubbles that form with an internal inherent energy lower than the inherent energy in our inflating universe will indeed begin to expand: the tension of space-time outside the bubble is greater than that inside, so the bubble walls are pulled outwards. But when inflation ends in our universe, the tension dissipates, and the bubbles appear to start collapsing like deflating balloons.

A world within That’s how it looks from the outside, from our vantage point, “but there is more to this picture”, says Vilenkin. The bubbles’ true fate depends on their size. Bubbles that formed later would be smaller, and should collapse into standard black holes, with nothing inside apart from an infinitely dense point called a singularity. But earlier bubbles would be bigger and would create larger black holes that conceal their own inflating universes. For the first fractions of a second after inflation ended in our patch of space-time, when the bubbles began

Double Negative team, TM & © Warner Bros. Entertainment Inc. (s15)). (CC BY-NC-ND 3.0)

A quirk of cosmic history could mean that black holes were once portals to other universes, finds Anil Ananthaswamy

collapsing, we would have been connected to their interiors via wormholes. Unfortunately these wormholes would have closed almost immediately, cutting off the inflating universes within. “The opportunity has passed for us to send signals to these other universes,” says co-author Jaume Garriga of the University of Barcelona, Spain. Even after the wormholes close, the space-time inside the black holes keeps inflating (arxiv.org/abs/1512.01819v1). Andrei Linde of Stanford University in California, another pioneer of inflationary cosmology, is impressed. The work builds on ideas that were first thought up nearly 30 years ago, but Vilenkin and his colleagues have carried out the most detailed analysis yet of the bubbles’ fate. “It is beautiful general relativity,” says Linde. “General relativity sometimes

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In this section n Climate change is behind UK winter flooding, page 11 n The young women facing down TB, page 14 n Microbe-made ink for dyeing clothes, page 18

A 10-minute rest can boost memory like sleep

general relativity and black holes at the University of California Santa Barbara, points out that physicists have long wondered whether black holes conceal more than they reveal at their surfaces. “This is essentially an extreme example of an ancient point, that black holes can have enormous interiors,” says Marolf. Our universe could even look like a black hole to physicists in some other universe. “This subject is really, really deep,” says Linde. “We are just starting to touch the surface and discover new things about the multiverse.” n

Ozgur Donmaz/Getty

offers you things that are extremely non-intuitive.” The analysis provides a fresh way to look for signs of the multiverse by suggesting that our universe should have a distinctive distribution of black holes. The higher the mass of the black holes, the more of them there should be up to a critical mass, after which the number should fall. “That critical mass separates ordinary black holes from black holes that contain an inflating multiverse inside of them,” says Garriga. This could help solve a longstanding mystery. Standard astrophysics has a hard time explaining how supermassive black holes became as big as they are today – there hasn’t been time for them to suck up sufficient matter. But in the new theory, the largest of the black holes that hide a universe within them would have started out much bigger than is otherwise possible. These giants could have grown to become the

NEED to remember something? Take a  break. It seems that resting in a quiet room for 10 minutes without distractions can boost our ability to remember new information. “A lot of people think the brain is a muscle that needs to be continually stimulated, but perhaps that’s not the best way,” says Michaela Dewar at Heriot-Watt University in Edinburgh, UK. To store them long-term, new memories must be consolidated, a process thought to happen while we sleep. But at least some consolidation may occur while we’re awake, says Dewar – all you need is time out. In 2012, her team found that people who had a 10-minute rest after hearing a story remembered 10 per cent more of it a week later than those who played a spot-the-difference game immediately afterwards. “We dim the lights and ask them to –Was Interstellar right?– sit in an empty, quiet room, with no mobile phones,” says Dewar. Most supermassive black holes we see volunteers said they let their minds wander during this time. today at the heart of galaxies, Now Dewar and her colleagues have including our own Milky Way. shown that rest can also consolidate The work may also have spatial memories. Volunteers who implications for the black hole rested after exploring a virtual-reality information loss paradox, which environment were 10 per cent more physicists have battled over for accurate at orientating themselves decades (see “Information lost in relation to virtual landmarks and found”, left). (Hippocampus, doi.org/926). Don Marolf, who studies

This is good news for insomniacs, suggesting that simply resting while awake can give us some of the memory benefits of sleep. “As long as you’re reasonably relaxed, you might still be experiencing some of the memoryconsolidation processes,” says Gareth Gaskell at the University of York, UK.

“People with amnesia who could not remember words from a list were able to after a few minutes’ rest” The effect is particularly strong in people with amnesia. In a memory test of a list of words, eight of 12 volunteers with the condition were unable to remember any of them without a break. But after resting for 9 minutes, the same volunteers could recall between 30 and 80 per cent of the list. “Most of them can’t lead a normal life because they can’t remember what they did 10 minutes ago,” says Dewar. The results suggest that people with amnesia may not have completely lost the ability to form new  memories after all. Dewar thinks that overstimulation may be what causes memory problems in amnesia. “If we try to reduce the amount of information going in, people with amnesia can form new memories,” she says. Jessica Hamzelou n

–Relax, then recall– 9 January 2016 | NewScientist | 9

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This week

Women can ‘grow’ own IVF embryos Kevin Doody of the Center for Assisted Reproduction in Bedford, Texas, who carried out the trial. Doody wants to offer the device to women at his clinic, and reckons that it could halve the cost per cycle, typically $16,000

KEEP them close. Women having IVF can now incubate embryos in their own bodies before they are implanted in the womb. Results from a clinical trial suggest the incubation device could work as well as conventional IVF and be far cheaper. Cylindrical in shape, INVOcell is held in the vagina by a flexible diaphragm. The embryos are kept in an inner chamber at body temperature and gases such as carbon dioxide and oxygen diffuse in and out at levels matching natural fertilisation. After five days the embryos will have grown into balls of about 100 cells. The device is then removed and doctors choose the embryo that looks healthiest to implant. In a US trial of 40 women, the device performed almost as well as conventional incubation, with 65 per cent of the women becoming pregnant regardless of the method used. Fifty-five per cent who used in-body incubation went on to give birth compared with 60 per cent who had the standard method. “We were very pleased with the results,” says

Guinea pigs tweak genes to beat heat HOT stuff. For the first time, wild mammals have been seen responding to higher temperatures by altering how their DNA works. These “epigenetic changes” may adjust the activity of specific genes, and some are passed on to offspring. “Global temperatures are rising. It is crucial to understand how wild species are able to cope,” says

Phanie Sarl/Corbis

Andy Coghlan

Alexandra Weyrich of the Leibniz Institute for Zoo and Wildlife Research in Berlin, Germany. Evolution by genetic mutation and natural selection can be slow. But attaching methyl molecules to DNA, affecting how genes are expressed, is much faster. Evidence from lab-bred animals and plants shows that such heat-induced epigenetic responses can even be inherited. To see if this can happen in more genetically diverse animals, Weyrich’s team studied guinea pigs sourced from South America. They allowed five males to mate with females in an

to $20,000 in the US. In conventional IVF, incubators are set up to mimic the body and have to be regularly monitored to ensure early embryos are supplied with the right amounts of gas and that conditions are optimal for five days. Because the woman’s body acts as a natural incubator, such expensive equipment isn’t needed, he argues. Doody sees the device being used for relatively uncomplicated IVF cases in clinics with simpler

equipment, perhaps in countries where many people can’t afford standard IVF. More complex cases, where a sperm has to be injected into an egg, say, would take place in conventional clinics with highly skilled personnel. A trial of the device in Colombia also produced successful pregnancies. “Organising a lab for INVO is very simple and cheap compared to the sophisticated labs for conventional IVF,” says Elkin Lucena at the Center for Fertility and Sterility in Bogotá, who carried out the trial there. “For developing countries that’s really important.” Although the manufacturers of INVO were given permission to sell it in the US in November, not everyone is convinced it has proved its worth. “Those that genuinely cannot afford IVF may well leap to this if it’s substantially cheaper,” says Simon Fishel of the CARE Fertility Group in Nottingham, UK. But he warns that there are “serious attendant risks” that fertility clinics need to decide whether to accept. These include problems that arise from abnormal fertilisation that go unnoticed because the embryo can’t be checked during incubation. Doody counters that any abnormal embryos are likely to die naturally before the device is removed from the woman, leaving only the fittest for –Who needs an incubator?– implantation. n

enclosure at a normal ambient temperature of below 5 °C, and then again with other females after spending two months at 30 °C. There were signs of altered methylation in at least 10 genes that regulate body temperature. “This suggests global changes in the environment like climate change will affect all species through environmental epigenetics,”

“Epigenetic changes might buy a species time to evolve permanent adaptations”

says Michael Skinner at Washington State University in Pullman. There were also differences in the methylation patterns of the offspring conceived before and after heat treatment, suggesting temperature can affect the next generation (Molecular Ecology, doi.org/bbf9). These epigenetic responses may help organisms cope, but they won’t make them adapt, says team member Jörns Fickel, because they don’t affect the DNA sequence. Instead, they might buy a species time to evolve permanent adaptations to a warmer climate. Penny Sarchet n

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INSIGHT Extreme weather

Aviva Rutkin

IT’S an environmental whodunit. Last month, in streets that would normally be bustling with sales shoppers, the only sounds were the thrum of helicopters and the lapping of water against walls. First Desmond, then Eva and Frank: three major storms slammed into the UK and Ireland during December, making it the wettest month ever recorded in the UK and causing flooding misery in northern England and Scotland. Now those affected want to know where to lay the blame. “Rhododendrons flowering in December and a flooded house – any correlation do you think?” asks Selena Whitehead, whose house in York was

“We’re living in a climate that is warmed. All of our weather is affected by climate change” inundated by the river Ouse on 27 December. She’s not the only one who suspects climate change is responsible – but how to prove it? Friederike Otto at the University of Oxford has been studying the relationship between extreme weather and climate change, and has turned to storm Desmond to test her team’s methods. “We saw all the speculation about whether or not climate change played a role. We decided we could do better than speculate – we could find out,” says Otto. To analyse Desmond, her team used three different methods for modelling climate, looking at global, regional and local patterns. All three approaches found that the likelihood of heavy precipitation has increased. Overall, the team found that storms like Desmond are about 40 per cent more likely now than they were in the past.

Desmond isn’t the first weather event linked to climate change. Last October’s hurricane Patricia and flooding in South Carolina were both probably made more likely or more severe by climate change. But coming up with an exact link between climate change and weather events is tricky. We need lots of data to show whether rare, once-in-amillennium events like the South Carolina floods are becoming more common. And in many places, such as southern India, which experienced flooding in November and December, there are no robust climate models for the area that can analyse the flooding. Rainstorms are particularly tough to study, because they are affected by many factors, says Michael Wehner of Lawrence Berkeley National Laboratory in California. In October, he presented initial results from a study of the role climate change played in Colorado’s 2013 floods. By comparing the river basin responsible with the same basin in an imaginary world without anthropogenic climate change, his team found that the real basin received an extra 8 centimetres of rain. Wehner’s results won’t be published until years after that storm ended, but he hopes that, in future, scientists will be able to combine several climate models with expert judgement, so that they can make calls on the role of climate change in extreme weather events as they are happening. But asking if climate change is to blame for an individual event may be the wrong question, says Hayley Fowler at Newcastle University, UK. Such events would probably happen anyway, but can be enhanced or made more frequent by climate change. “We’re living in a climate that is warmed,” she says. “All of our weather is affected by climate change.” n Additional reporting by Kate Ravilious

Jeff J Mitchell/Getty

Pinning UK floods on climate change

–Becoming more frequent?–

Human spaceflight: is it worth the money and risk? 15 January 2015, 7.30pm Science Museum, London, SW7 2DD Join us for a lively debate with the UK’s first astronaut Helen Sharman, Astronomer Royal Martin Rees, space scientist Monica Grady and The Sky at Night’s Chris Lintott. Held in partnership with the Science Museum. Tickets £5 – book now at royalsociety.org/human-spaceflight Image: Ed White performs first U.S. spacewalk, 1965. Credit: NASA.

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Nigel Cattlin / Alamy Stock Photo

This week Giant planets might eat their own moons

Farting plants kick up a stink if irked Michael Le Page

They found that this plant’s roots are also touch-sensitive, releasing the odour when accosted (Plant Physiology, DOI: 10.1104/pp.15.01705). The smell – a cocktail of sulphur compounds – seems to be released from tiny hair-like sacs less than half a millimetre long and dotted along the roots of the plants, which collapse after the odours are released. Even a seedling just a few centimetres high can fill a room with a disgusting smell, says Musah. Seedlings grown in sterile conditions still produce

“OH MY goodness! It smells like someone has broken wind.” So says Rabi Musah of the University at Albany in New York, who has discovered a previously unknown defence mechanism in plants: roots that actively release a nasty smell when they sense the touch of a potential threat. Many plants are famed for their putrid smells, and it has been known for decades that unpleasant sulphurous odours are released when soil is disturbed around the roots of some plants – including members “Even a seedling just a of the Mimosa genus. Until now, few centimetres high it has been assumed that these can fill a room with a odours are released passively as a result of tissue damage, like when disgusting smell” a bay leaf is crushed or onions are cut with a knife. the sulphuric scent, indicating But Musah has found that the that it is a product of the roots roots of some species actively themselves rather than coming release their foul smell. Her from associated bacteria. team made this discovery while Perhaps more astonishing is growing seedlings of Mimosa that the roots seem to distinguish pudica, known for its sensitive between different kinds of touch. leaves that fold up when touched. “The odour response is selective,”

HERE’S to all the moons we’ll never see. Gas giant planets risk wiping out their own satellites, and it’s all down to the steps of a gravitational dance. Exomoons – moons around exoplanets – may be the most likely places to find alien life, but dedicated searches have found none so far. That may be because many don’t survive, suggest Christopher Spalding of the California Institute of Technology in Pasadena and his colleagues. Models and observations indicate –Mimosa : silent but violent- that giant planets usually form far from their stars and then drift Musah says. A single touch with a inwards. As they do so, their orbital period shortens and the orbits of finger is always enough to trigger their moons tend to shift as well. the stench, her team found, but This orbital dance can stretch and the roots never respond to a glass drag a moon’s path. If the planet’s or metal object. Nor do they inward drift continues, it’s only a usually react to a single touch from soil, while dragging the roots matter of time before a moon veers too close to its planet. Eventually, the across soil does trigger the smell. planet’s gravity either tears the moon Just how the plant senses apart or causes the two to collide. This these distinctions is unknown. shrinks the region around a planet This selectiveness presumably where moons can survive. helps the plants differentiate To illustrate the theory, Spalding between the touch of predators modelled what would happen in a and harmless objects. simplified solar system containing just The finding is further the sun and Jupiter, with Jupiter slowly evidence that plants are much migrating inwards from its present better at sensing and responding path at 5.2 times the radius of Earth’s to their environment than orbit. He found that Jupiter’s moon Io generally appreciated. “We still would be destroyed when the planet underestimate plants a lot,” had closed in to 0.6 times Earth’s says Frantisek Baluska of the distance from the sun (arxiv.org/ University of Bonn, Germany. abs/1511.09472). But the smell might not be In a different solar system, this aimed at predators, suggests migration could eliminate moons that Anthony Trewavas of the would have become suitable for life as University of Edinburgh, UK. Instead, it may act to fend off roots their planet closed in on its star. The thought scares David Kipping from other plants that encroach of Harvard University, who is racing to upon its territory. “The fact that they are smelly to us is irrelevant.” discover the first exomoon. “Your first The phenomenon is not limited thought is, oh no – does that mean we’re not going to have any moons to one species. Musah has found left over?” he says. that at least six other Mimosa But he notes that the moons that species produce the smell and are most at risk are also the hardest to now plans to study plants in the see. “Those moons are not really the closely related Acacia genus. The moons we’re looking for,” Kipping phenomenon could turn out to says. Joshua Sokol n be widespread, says Baluska. n

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This week FIELD NOTES Community healthcare in Ethiopia

Linda Geddes

Berkley, CEO of Gavi, a global vaccine initiative. “Ethiopia has established an infrastructure whereby the extension workers could be sentinels for the early detection of disease.” Women make more reliable recruits than men as they are less likely to leave the village to find work. The first graduates of the programme were deployed 10 years ago. Since then they have been credited with improving the health of the population to such an extent that other African countries are taking notice. The increase in life expectancy, for example – from 47 years in 1990 to 64 years in 2013 – can partly be attributed to the scheme, as can

AT FIRST, Beyera Guta assumed he had a cold. Months passed and the sickness dragged on until he became so weak that he could no longer provide for his family. Tuberculosis was consuming his lungs and slowly killing him. The person who saved his life wasn’t a doctor, or a nurse. It was a 24-year-old woman from his village called Anuma Moreda, who hadn’t completed high school. Alerted to Guta’s symptoms by his cousin, she examined him and sent a sputum sample to the local hospital. When the result came back positive, Moreda (pictured, below left) supervised his treatment and “More than 40,000 women nursed him back to health. This is the future of healthcare, have been recruited to be Ethiopian-style. In a country where sentinels for the early 22 per cent of the population lives detection of disease” below the poverty line, and there are just three doctors for every the reduction in child mortality, 100,000 people – compared deaths related to malaria and new with 30 or 40 in Europe – the HIV infections. government has pioneered a “There are now 11 to 13 African strategy that would be unthinkable countries that are either working in most developed countries. on or thinking about introducing More than 40,000 women – similar programmes,” says some as young as 16 – have Haileyesus Getahun of the been recruited to carry out tasks WHO community engagement normally only done by doctors unit in Geneva, Switzerland. and nurses: give childhood A current focus of the vaccinations, provide antenatal programme is TB, a disease that care, screen for deadly diseases kills an estimated 4400 people and supervise their treatment. around the world every day – In a post-Ebola world, these more than HIV and AIDS. Ethiopia health-extension workers create has the third highest rate of TB a link between the community in Africa. It is tough to treat: and the health service that allows diagnosis takes several weeks, for the quick dissemination of and drugs must be taken for six to information. “The problem with eight months, otherwise you risk Ebola was recognising it. It took the disease coming back, or drugthree months from the first resistant strains emerging. people showing symptoms to a Moreda and her colleague diagnosis being made, says Seth Gobinei Kebede (pictured, far right)

Nahom Tesfaye/WHO

The young women facing down TB

–Treating TB is no easy ride–

work out of a mud and timber hut plastered with immunisation charts and disease prevention posters, in the rural region of Oromia, about 2 hours’ drive from the capital, Addis Ababa. The women serve a community of around 5000, some a 2-hour walk away. Things get particularly tough during the rainy season, when the roads turn to mud. The women screen and test the community for TB, and ensure people take the drugs they receive from the local TB clinic correctly. In serious cases, such as drugresistant TB, patients are moved to the larger hospital in Addis Ababa. When Moreda completed her year-long training at the age of 17, she received a starting salary of around $30 per month. Today she

earns $80 and expects this to rise to $100 – just short of a nurse’s salary – in the near future. The pay and level of training is a key difference from community schemes in other countries, which tend to use volunteers. “Ethiopia has done a number of smart things,” says Mario Raviglione, director of the WHO’s Global TB Programme. “They pay their workers, which means they get status in their community. With this you can actually reach all the people in the community who need treatment.” At the Ministry of Health, there’s talk of training some workers to the equivalent of a family doctor. When I ask Moreda and Kebede about this, they smile and shake their heads. “That would be good, but I don’t think it will happen soon,” Kebede says. Both have young kids, but they continue to work. “We are the only ones who are providing health services for the community,” Moreda says. “Juggling childcare is difficult, but I hope I am being a good role model for my son.” n The WHO paid for Linda Geddes’s trip

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in Brief Memory works faster than blinking

Liver hormone may tame our love of sugary foods LOVE a sugar hit? Your sweet tooth may hail from an unlikely source: a hormone made by the liver appears to control how much carbohydrate and sugar we want to eat. Genetic studies suggest that people with altered levels of FGF21 eat more sugary foods and carbohydrates, which in turn get broken down into sugars. To find out more, a team co-led by Matthew Potthoff at the University of Iowa observed the eating habits of mice with either abnormally high or low levels of the hormone. Mice genetically modified to lack the hormone chose to drink much higher levels of sugar-sweetened drinks than

normal mice. Those given an extra dose of the hormone, on the other hand, reduced their sugar intake (Cell Metabolism, doi.org/bbj9). Similar results were seen by a separate team in monkeys given alcohol. Potthoff’s team also showed that the liver releases more of the hormone in response to high levels of carbohydrate in the gut. The hormone travels to the brain, where it works to suppress sugar intake. This only applied to high levels of simple carbohydrates – those found in cakes and biscuits, for example, that get broken down into sugars quickly. Extra FGF21 wasn’t produced in response to complex carbs that take longer to digest. Potthoff thinks that the hormone might affect the brain’s reward pathways, dialling down the appeal of otherwise enjoyable sweets and alcohol.

Giant galaxy shreds smaller neighbour IF THE Milky Way is ever indicted for gobbling dwarf galaxies, it’s got a defence: other giant galaxies are doing the same thing. Two teams of astronomers spotted a dwarf in distress orbiting NGC 253, a giant spiral galaxy 11 million light years away. The new-found galaxy is a ghostly type known as a dwarf spheroidal, whose stars are widely separated from one another.

Dozens of these galaxies have been spotted orbiting the Milky Way, but they are so dim that until recently no one had seen any beyond the most local collection of galaxies. Unlike most others of its type, the new dwarf is very elongated, with its long axis pointing towards the giant galaxy. This suggests the giant is stretching the dwarf.

“It looks like it’s being ripped apart by the larger galaxy,” says Aaron Romanowsky of San Jose State University in California, who helped discover the new galaxy (arxiv.org/abs/1512.03815). Astronomers caught our galaxy tearing apart a nearby dwarf in 1994. The latest discovery is the first time a giant galaxy outside our local family has been caught disrupting a dwarf spheroidal, whose stars will join the predator galaxy.

IT TAKES just 150 milliseconds to recall something, half the time it takes to blink. Memory recall starts with a cue: a jangly doorbell may remind you of a song, say. Information about the cue travels to the brain’s hippocampus, where a set of cells recognise it. These cells trigger an activity pattern that matches that of the memory. This was thought to take about half a second. Now Simon Hanslmayr at the University of Birmingham, UK, has shown it can happen faster. He monitored brain activity while volunteers recalled the location of an object on a screen. Later, he replayed the objects – but this time at the centre of the screen – and found it took just 150 ms for the memory pattern of the original location to form (Journal of Neuroscience, DOI: 10.1523/ jneurosci.2101-15.2016). This suggests the hippocampus was bypassed somehow, he says.

Polar bear incest and cub adoption INVESTIGATING the family tree can bring surprises. A study of the pedigree of 4449 Canadian polar bears from six generations has uncovered the first reported case of identical twins, one case of sibling incest and six adoptions. Polar bears usually give birth to non-identical twins. Incest is rare, probably because related bears are unlikely to meet each other once they have matured and dispersed. The adoptions could be due to mistaken identities, although it is possible that females do not even notice the addition of an adopted cub into a litter, says René Malenfant at the University of Alberta, Canada, who led the study (bioArxiv, doi.org/bbf4). “We don’t yet know whether polar bears can count.”

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Bertrand Charry/Bruce Head Narwhal Study, courtesy of Baffinland Iron Mines Corporation

Narwhal nurseries Sheep and humans show shoving makes evacuation slower spotted DON’T panic! Experiments with asked them to evacuate in three moving through a doorway on humans and sheep show that when a group has to move through a narrow opening, they take longer if each individual tries to move quickly. The so-called “faster is slower” effect has been cited as a factor in tragedies such as the 1989 Hillsborough Stadium disaster in the UK and the 2003 Station nightclub fire in the US. But until now it hadn’t been fully tested. Iker Zuriguel and colleagues at the University of Navarra, Spain, put 95 volunteers in a room and

different ways: avoiding all physical contact, allowing soft contact, and allowing gentle pushing. More competition meant a slower escape, they found. “People get stuck in the door,” says Zuriguel. “This can be dangerous.” Next they recruited a flock of hungry sheep. “Sheep are useful,” says Zuriguel. “They are used to pushing each other just for food.” Sheep move more quickly in warmer temperatures, so the researchers compared their speed

warm and cool days. As expected, individual sheep moved more quickly when it was warm, but the group as a whole was slower to get through the door. A third experiment showed the same effect with glass beads (Physical Review E, doi.org/bbcq). Previous experiments did not allow people to push each other, says Zuriguel, so simulations based on them and used in emergency planning might be unrealistic. The research could help design better emergency exits. Abdeljebbar Qninba

THEIR bizarre single tusk has earned them the nickname “unicorns of the sea”. Like their mythical counterparts, narwhals are particularly elusive, spending over half the year beneath the ice in deep offshore waters. Not knowing how many of narwhals there are makes protecting them tricky. To better understand them, Bertrand Charry of McGill University in Montreal, Canada, has used aerial shots of the Canadian Arctic – home to three-quarters of the global population – to count baby narwhals. The photographs were taken from a 2013 survey by Fisheries and Oceans Canada. He was surprised by his findings. Among a large population of 35,000 narwhals in the Admiralty Inlet, less than 0.5 per cent were newborns. But in a smaller summer population at Eclipse Sound, newborns made up nearly 5 per cent of the 10,000-strong group. This suggests that Eclipse Sound could be an important calving and nursery habitat, says Charry, who presented his results at the ArcticNet conference in Vancouver in December. He hopes this knowledge will help create effective catch limits, as well as inform plans for scaling up iron-ore shipping from Milne Port on Eclipse Sound.

Where your inhaled bacteria come from THAT’S a relief. Your home is crawling with bacteria – but more of the bugs you breathe in come from tap water than the toilet. Marzia Miletto and Steven Lindow at the University of California, Berkeley, have mapped the microbes circulating in 29 homes in California. Taking samples from kitchen surfaces, shower heads, bathroom tiles, carpets, pets and people, the team found that one of the most common sources of airborne bacteria in these homes was outside air (Microbiome, doi.org/946). “This is a good thing,” says Miletto. The air accounted for 16.5 per cent of the bugs, while floors and carpets contributed nearly 20 per cent – probably because walking across a floor or hoovering stirs up these bacteria into the air. Thankfully, few airborne bacteria seem to be whipped up by flushing the toilet. Only 0.4 per cent of them were traced back to the toilet bowl – far less than the almost 9 per cent that came from tap water. All these bacteria are likely to mostly be beneficial: exposure to a diverse array has been linked to better health.

Falcons imprison birds to eat later RAPUNZEL had it easy. On the barren Moroccan island of Mogador, falcons seem to imprison small birds by plucking out their feathers, or stuffing them in crevasses, so they can eat them later. Eleonora’s falcons hunt larks, warblers, hoopoes and other birds migrating south. But not all captured prey have quick deaths. In a census of the island’s falcons in 2014, Abdeljebbar Qninba of Mohammed V University in Rabat, Morocco, and his colleagues saw small birds missing their flight and tail feathers, trapped in deep

cavities. Other birds were “jammed into a deep and very cramped hole… unable to move their wings or operate their dangling legs”, they wrote in the French journal Alauda. Crippling and imprisoning prey might be a means of keeping fresh food nearby, so parents can stay on the nest or give hungry offspring something to snack on. But Rob Simmons of the University of Cape Town in South Africa suggests another explanation: “The birds’ prey may be simply escaping and finding refuge in holes in the cliffs the falcons nest in.”

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G.M.B. Akash/Panos

Technology In 2013, Johnson was part of a team that genetically engineered E.coli bacteria to produce indigo, the dye used in blue jeans. Like Pili, Johnson’s team was looking for alternatives to synthetic dye, which is energy-intensive to make and relies on raw materials derived from oil. Johnson’s collaborator John Dueber is continuing the work, hoping to turn it into a commercial process. Making a little dye in the lab is a neat trick; producing enough for industrial purposes would be a real feat. The denim industry gets through 40,000 tonnes of synthetic indigo annually. Scaling up bacterial production will mean understanding precisely what resources are needed to feed all the bacteria, and maximising –New hues will alter jean expression– the yield. Pili is also testing how to get its bacterial dyes into clothes. Currently, the company grows the microbes right on the garments themselves. When dyeing is complete, the team kills the bacteria with heat or simply by Microbes can help us make dyes that don’t rely on oil throwing the clothes in the wash. and nasty chemicals, finds Aviva Rutkin “When you’re talking about replacing something made with WHAT puts the colour in your varying the temperature and North Carolina State University in petrochemicals, the production clothes? At present, the answer the time – the team learned to Raleigh, says it’s a fascinating idea. process has to be very efficient in is usually petrochemical dyes. control the ink production and order to compete with the scale Modern dye production often Now a French start-up called Pili even to coax Streptomyces and relies on corrosive substances like and cost of current processes,” is offering a radically different other bacteria into producing says Christina Agapakis, a nitric acid, something that approach: getting bacteria to four other colours: red, yellow, synthetic biologist in Cambridge, synthetic biology could render make dyes in the lab, with sugars orange and violet. Massachusetts. Pili is working unnecessary. “The beauty of the as the only raw material. “We started to wonder if such with the French pen bio approach is the elimination Thomas Landrain and his coa way of producing colours could manufacturer BIC to help answer of harsh chemicals,” he says. founders at Pili hatched the idea become a true alternative for Terry Johnson at the University some of these questions. three years ago at a biohacking lab already existing petrochemical Bacteria’s colourful side has of California, Berkeley, agrees that in Paris called La Paillasse. They dyes,” says Landrain. uses beyond industry. Natsai it holds promise. “You see more wanted to build a pen powered by Many inks are made from a Audrey Chieza, a researcher and “Synthetic biology is bacteria: feed in sugar, get back mixture of petrochemicals and designer in London, has her own getting to the point where project to make patterned silk by ink. Their first lead was a South organic pigments; others involve American strain of Streptomyces compounds of heavy metals such you can compete if you growing pigment-producing bacteria which produces blue as cadmium or lead. The black ink choose products carefully” bacteria on fabric. She wants to pigment. Landrain and his in a ballpoint pen, for example, turn her technique into a craft, colleagues learned to extract the gets its colour from carbon black, transforming her artistic vision and more companies exploring pigment and write with it. made by burning petroleum into a series of scientific steps making commodity chemicals The group tried the bio-ink in products. “We began to imagine with synthetic biology, and I think that anyone can apply. an inkjet printer, and explored a future without that industry,” Producing dye biologically it’s a really big step,” he says. “The what it would take to use it with says Landrain, one in which dyeis still in its infancy. But if it technology is getting to the point textiles. By fiddling with the making has no dependence on oil. where you can potentially works, says Chieza, “this could microbes’ environment – feeding Harold Freeman, who studies revolutionise how we dye in the compete if you’re careful about them different kinds of sugars, organic dyes and pigments at fashion industry.” n choosing your products.”

Tint without taint

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Wind whips plastic grass to produce power Yang worked on the project with Zhong Lin Wang’s group at the Georgia Institute of Technology in Atlanta. The goal was to tap energy not just from steady winds, but from the choppy gusts

Bot that watches while you work can catch slip-ups

work in the office and kitchen, Watch-Bot was about 60 per cent accurate in shining a laser pointer at the missed task, such as returning milk to the fridge. Ashutosh Saxena and Chenxia Wu, at Stanford University in California and Cornell University in New York, built Watch-Bot by mounting a depth-sensing camera on a tripod and connecting it to a computer and a laser pointer. The robot learns unaided, finding patterns in human movements it observes. “The good thing about unsupervised learning is you don’t need to annotate a lot of data, which means it’s cheaper,” says Yezhou Yang at the University of Maryland. Watch-Bot could help people with

ELLIE works on a car engine assembly line. Despite her best efforts, she occasionally forgets to screw in one of the bolts, but a laser beam from the ceiling highlights the loose piece as the engine passes, reminding her to tighten it. This imagined scenario could soon be reality. A robot called Watch-Bot can watch people work, learn the steps that make up the task, then remind people when they forget a step. In 24 trials watching humans at

Oleg Moiseyenko/Getty

THE wind flowing over your roof is packed with energy, if you could only harness it. A new type of wind power generator can do just that, by carpeting a surface with plastic strips that sway in the wind like grass. It produces renewable energy where traditional windmills would be impractical. The generator is made by fixing flexible strips of plastic to a board, so they stand upright like rows of dominoes. The strips have nanowires etched on one side and a coating of indium tin oxide (ITO) on the other. When the strips flail in the wind, the nanowires slap against the ITO surface of neighbouring strips. This temporary contact allows electrons to leap from one material to the other, creating a current through a phenomenon known as the triboelectric effect. Covering a 300-square-metre rooftop with the strips “would be expected to deliver 7.11 kilowatts, which should mostly power a household,” says Weiqing Yang at Southwest Jiaotong University in Chengdu, China.

typical of built-up areas too. “Compared with a wind turbine, our triboelectric nanogenerator (TENG) is effective at harvesting the energy from natural wind blowing in any direction,” says Yang. He adds that the harvesting system is simple to make, and easy to scale up. So far, the generator has only been tested in the lab, aiming an electric fan at a model rooftop

covered with 60 strips. This generated enough electricity to light up 60 LEDs. The strips work at wind speeds as low as 21 kilometres per hour, but the most useful power was generated with direct wind at almost 100 km/h – or storm force 10. That’s neither easily available nor desirable, says Fernando Galembeck, who investigates energy harvesting at the University of Campinas in São Paulo, Brazil. “Significant amounts of power are obtained but we are still far from installing these devices on our rooftops and building walls.” Galembeck says that, as with any energy scavenging technique, energy storage will be crucial for the system’s success, allowing the variable amounts of power generated in gentle winds to be stored until needed. Yang says they are seeking a storage solution, as well as working on integrating the nanogenerator with solar panels to boost output. Galembeck also points out that indium tin oxide isn’t a suitable material, due to its poor mechanical properties, cost and toxicity. “The concept is highly promising but its realisation depends on shifting to other materials,” he says.

–Wind power without windmills– James Urquhart n

daily activities – not just annoyances like taking your keys with you, but safety issues like turning the stove off. Saxena and Wu see their bot someday helping elderly people live independently. Something like Watch-Bot could even be used in homeland security or the military, says Ronald Arkin at the Georgia Institute of Technology in Atlanta. “One of the problems is recognising hostility or hostile intent. Could these systems recognise what hostile intent was? If they could do

“Watch-Bot could help people remember daily activities like turning the stove off”

this unsupervised, it would be very interesting.” Saxena and Wu are not comfortable trusting their bot with tracking vital safety tasks until they can improve the accuracy. They also want to find out if the robot fills a need and whether people like it. The beauty of Watch-Bot is its simplicity, says Saxena. “A robot with a camera is very easy to manufacture and ship. All a company needs to do is take that robot and let it sit there. Just by doing that, the robot can become useful over time.” After about a week of sitting in a workplace or home, Saxena thinks Watch-Bot will learn enough to give helpful reminders. Anna Nowogrodzki n 9 January 2016 | NewScientist | 19

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Watching out for seizures An ordinary smartwatch can be a lifeline, finds Lisa Grossman

Ryan Clark

frequency range seen during tonic-clonic seizures. He tested that range by watching YouTube videos of people having seizures and mimicking their motions while wearing the watch. He then compared the results against scientific literature. If the watch detects motions that go above a certain threshold, it sends an alarm to the wearer’s phone. The wearer has 15 seconds to turn the alarm off if they are not having a seizure. Ryan warns that the software is vulnerable to false positives. It can also miss real seizures if the arm wearing the watch gets trapped under the person’s body, for instance. “It’s not foolproof,” says Ryan. “It shouldn’t be relied upon, but makes it more likely that a seizure will be detected.” If the alarm is not cancelled, the app automatically sends a text to predetermined numbers – in Kathryn’s case, Ryan and her dad. The text includes the wearer’s last known GPS location so the recipient can come and help. The app also has a “panic” button. If the wearer feels a seizure coming on, they can press it to warn their contacts. It’s the only function Kathryn has had to use in the past year – although thankfully none of her “panics” turned into tonic-clonic seizures. The Clarks say the watch has given them an increased sense of security and peace of mind. “Most people with epilepsy and other chronic conditions will tell you it’s always a struggle to balance freedom with safety, independence with responsibility,” Kathryn says. “Once you get over the shock that you have seizures, you do have to get down to, OK, how am I going to live with them? This has been the answer in a lot –Kathryn Clark has a very smart watch– of ways for us.” n

Driving up the walls Never mind struggling up the stairs a four-wheeled robot developed by Paul Beardsley at Disney Research in Zurich, Switzerland, can drive straight up vertical walls. About 60 centimetres long, the robot has two propellers that provide thrust, allowing it to make the transition from ground to wall. One rotor pushes the robot onto the wall while the other pulls it up. Beardsley next plans to tackle transitions from wall to ceiling.

$500m The amount of money that

General Motors has invested in car-hailing service Lyft to develop self-driving taxis

Zuckerberg’s AI butler Facebook CEO Mark Zuckerberg needs help around the home, and he has turned to artificial intelligence. Dubbing it a “personal challenge for 2016”, Zuckerberg said he would “build a simple AI to run my home and help me with my work”. He wants the system to control music, lights and temperature, as well as recognising his friends’ faces and letting them in when they ring the doorbell. The bot will also keep tabs on his daughter’s bedroom.

Paul Beardsley/Disney research

KATHRYN CLARK’S epilepsy wristbands that do the job by had been under control for years. sensing electrical currents Then, in November 2014, she had travelling across the skin – but a tonic-clonic seizure – the kind Ryan and Kathryn’s system has where abnormal activity spreads an advantage. Ryan chose to work to the entire brain, leaving the with the $100 Pebble, one of the person convulsing on the floor. cheapest smartwatches on the “I haven’t had too many of market. This means the program, those in my life, and that one was called Pebble Seizure Detect, is out of the blue,” she says. She was “If the watch detects worried about looking after her motion above a threshold, children, then aged 2 and 4, if the it sends an alarm to the seizures were coming back. wearer’s phone” Her husband Ryan, an independent game developer, had an idea: program a smartwatch to instantly available to any of the detect movement characteristic of 1.5 million Pebble owners who a seizure and text him a warning. might be living with epilepsy, Now the pair have created with no need to buy anything else. software that does just that, and The Pebble has an accelerometer made it freely available online. that can detect the wearer’s Devices that detect seizures are motion, so Ryan wrote code to not new – researchers have tested spot rhythmic movements in the

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New Scientist is pleased to announce three one-day masterclasses in 2016, letting you go in-depth into some of the most fascinating areas of science: INSTANT EXPERT MYSTERIES OF PARTICLE PHYSICS Saturday 13 February 2016

Has all the excitement about the Higgs boson left you wanting to understand what the fundamentals of our material existence are really all about? Join us as we journey to the frontiers of particle physics with six leading experts.


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Night-time ninjas CAUGHT in the act. These mice probably think nothing can see them. But their late-night capers have been captured by a camera trap. The trap is the work of Eric Médard, a photographer in France who has been shooting animals at night for 25 years. His work isn’t easy, because unsurprisingly, many animals aren’t fans of cameras or photographers. Some, like owls, are sensitive to bright flashes, while others shy away from nearby humans. So Médard rigs infrared cameras and hides them in soundproof boxes in strategic spots around the countryside. There is “no visible light, no noise, no smell”, he says, making the system perfect for capturing animals unaware and undisturbed. The picture below shows him testing one of them. Médard’s photos appear in his book Passeurs de Lunes, published in French. It contains images of European wildlife at night, such as bats flying below an ivy-covered bridge, fire salamanders slithering out from their daytime hiding place and a fox sneaking away with a midnight snack. In the photo on the left, two mice are fighting on Médard’s cellar floor. He was inspired to try shooting after noticing crumbs of dog food in his kitchen drawers. A plate of grains, placed in front of a camera trap, lured the hidden pests for many photos – and this is his favourite. Aviva Rutkin

Photographer Eric Médard NaturePL

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Tipping the scales New diabetes cases are down in the US, a rare hopeful sign in a public health battle that erupted over 25 years ago, says Paul Zimmet DIABETES is one of the biggest global health threats the world faces. It is estimated there are now 415 million adults with the condition and by 2040 there will be 642 million. Most will have type 2 diabetes, the form linked to obesity and sedentary lifestyles. But alongside these gloomy figures comes encouraging news. There has been a decline in new cases of diabetes in US adults at a time when most despaired of a relentless upward trend. According to the US Centers for Disease Control and Prevention, new cases are on a downward slope. They fell from 1.7 million in 2008 to 1.4 million in 2014 – the first consistent drop since 1990. Declines in the prevalence and incidence of this condition are rare. Cuba bucked the trend during an economic crisis between 1991 and 1995, but that was a time of food rationing that saw reductions in

obesity. As the economy picked up, weight regain was associated with a reversal of the effect. So what is behind the US trend? There are possibilities that could, alone or together, explain it. First, there have been changes in the way diabetes is diagnosed. The use of blood sugar levels is gradually being replaced by measuring glycated haemoglobin. However, the criteria used for diagnosis via this metabolite have not been applied consistently across the US, so there may have been some underdiagnosis. Another possibility is that because type 2 diabetes has a strong genetic basis, we are now reaching a saturation point in the number of people in the US who were predestined to develop it in our current “obesogenic” environment. This would seem less likely given the significant migration into the US of people

Mix it up Diverse backgrounds will ensure the blend of creativity vital to physics, says Joshua Sokol WHEN judges in the US Supreme Court openly questioned the value to physics of boosting students who are from minority groups, scientists quickly disagreed. Researchers spoke out not just for the sake of inclusiveness, but because ensuring diversity might be our best chance to crack the biggest questions in the cosmos.

physics class? I’m just wondering what the benefits of diversity are in that situation.” His colleague, Justice Antonin Scalia, added fuel to the fire by suggesting many black students might do better at less prestigious universities. Physicists, astronomers and social scientists beg to differ – and have research backing them up. On the day of the court comments, Meg Urry, president of the American Astronomical Society, released an open letter

The judicial remarks came amid a legal challenge to “affirmative action” at the University of Texas, a widely used practice in which, to increase diversity, ethnic origin is used as a factor in admissions. “Ensuring diversity Chief Justice John Roberts might be our best chance stoked controversy when he to crack the biggest asked: “What unique perspective does a minority student bring to a questions in the cosmos”

questioning the use of the GRE – a standardised test – to decide who gets to do an astronomy PhD. Racial minorities and women tend to do less well in such tests. She cited a study of prizewinning postdoctoral fellows in astrophysics that showed a mismatch between GRE score and later career success. So using these scores alone fails to gauge talent but does decrease diversity. Other astronomers rejected the justices’ questions altogether. “Black students’ responsibility in the classroom is not to serve as ‘seasoning’ to the academic soup,” wrote astrophysicist Jedidah Isler in The New York Times. A letter

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For more opinion articles, visit newscientist.com/opinion

Paul Zimmet is a professor at Monash University and director emeritus of Australia’s Baker IDI Heart & Diabetes Institute, both in Melbourne

signed by 2500 US physicists and astrophysicists agrees. Isler and others say students from minority groups, who are still in the classroom despite whatever pernicious racism they’ve faced, already show grit. Astronomer Sarah Tuttle, of the University of Washington in Seattle, says paradigm shifts in physics come from the kind of creativity engendered by diversity. If we want our understanding of the universe to be free from petty human bias, we need people from all backgrounds involved. n Joshua Sokol is a freelance writer in Boston, Massachusetts

One minute interview

Late equaliser Why is football embracing technology after resisting it for years? We asked Lukas Brud of the sport’s rule-making body to those managers who want to be able to use them to monitor match-day player performance. Are there potential medical benefits to using the devices? You might expect that a player who runs 12 miles in a particular game, despite usually running only 10, to be exhausted and prone to injury. We’re trying to find out whether player-tracking can prevent injuries, but so far that’s just speculation. We need to gather more data. If we find out that access to data throughout games can prevent injuries, we’ll be the last people to oppose it.

Profile Lukas Brud is secretary of the International Football Association Board (IFAB), the body that determines soccer’s rules. Last year it approved the use of electronic performance and tracking systems during competitive matches

During matches, football teams can now use electronic performance and tracking systems. What exactly are these? These are video-based systems that track player position, and wearable devices that can do the same plus gather extra performance and physiology data, such as heart rate. Video-based systems have been providing post-match data to managers to inform tactics, and generating statistical analysis for the media, for some time. Teams have also long used wearables in training. We’re now allowing players to wear them during matches providing the devices are safe and the information isn’t received or used in the “technical area”, where the team staff sit during the game. Why have you decided to allow use of these technologies during games? Some of these devices are tiny and can be sewn into clothing. We don’t want referees to be in the position of having to try to enforce a ban on technology they can’t see. Also, we have listened

Why stop staff seeing the data during play? We want to protect refereeing decisions by preventing managers getting access to broadcast video replays. We don’t want a team with access to live match data to have any advantage over opponents that don’t. Half-time analysis of match stats is, however, allowed. Referees still aren’t allowed to access video replays during games. Will that change? We’ve been discussing that for the last two years, and are now at the stage of developing protocols for potential experiments. The Brazilian Football Confederation and US Major League Soccer are interested in running trials, and the International Football Association Board will decide in March whether to proceed. We’d like to run two years of tests and consultations, so a final decision could come in 2018. Football accepted goal-line technology only years after other sports had similar systems. Why the change of heart? I believe football will become much more technological, but it is a game played all over the world, including in areas where smartphones are not used, so change takes time. Some argue that football should be kept as simple as possible. It’s a valid argument, but at the same time we shouldn’t close the door to technologies that can improve the game. Interview by Nic Fleming


whose ethnic background predisposes them to developing type 2 diabetes. People of Hispanic origin, for example, tend to have a higher risk, with genetics suspected to play a role. It is also unlikely that screening for diabetes has been so effective that new cases have hit a plateau, considering there is still thought to be at least one undiagnosed case for each known one in the US. The most hopeful explanation for the trend is that public health messages aimed at tackling obesity and diabetes and which address food policy and promote healthier environments are beginning to hit home. There is increased recognition in the public health arena that obesity has been driving the diabetes epidemic. Evidence makes it clear that prevention is possible through healthier eating and reducing sedentary behaviour. If such messages are getting through, it would be a triumph for the government and the US public health movement, and would be a milestone in the prevention of a condition with huge personal and national costs. n

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The others inside you Long after birth, your mother’s cells linger in your body. Andy Ridgway finds out what they’re up to

paul tebbott


OW’S this for caring? Without being in the same room, building or even the same city as your mother, you can literally patch up her heart. Or your child can patch up yours. It’s an idea that takes getting used to at first, but hear us out: you probably left tiny little bits of you inside your mother. And you got stuff from her, too: her cells take up residence in most of your organs, perhaps even your brain. They live there for years, decades even, meddling with your biology and your health. Sure, your blood, skin, brain and lungs are made up of your own cells, but not entirely. Most of us are walking, talking patchworks of cells, with emissaries from our mother, children or even our siblings infiltrating every part of our bodies. Welcome to the bizarre world of microchimerism. The idea emerged in the 1970s, when cells with male Y chromosomes were detected in the blood of pregnant women. Until then, we assumed that a mother’s body and her child’s were kept completely separate during pregnancy. Their blood came into close proximity in the placenta – that large, messy bundle of blood vessels connecting mother and child via the umbilical cord – but never actually mixed. Nutrients, oxygen and waste shuttled from one to the other through filters. We now know that’s only part of the story. “The placenta has been described as having a selective immigration policy,” says Lee Nelson at the University of Washington in Seattle. Along with nutrients and waste, cells also move from one bloodstream to the other.

In recent years, we’ve learned that these cells live on for years inside mother and child, as resident aliens. They lodge themselves inside our organs, so that long after birth, a mother’s body is still in some way connected to her child’s. The question is: what are these cells up to? Are they just passengers along for the ride, or do they get actively involved in the life of their host? Spotting these “microchimeric” cells in the midst of billions of your own is a bit like looking for the proverbial needle in a haystack. To make matters worse, their number waxes and wanes in different organs, and they appear to move around the body. Depending on where you look, someone could appear microchimeric one day but not the next.

Staying power Still, those who study this phenomenon believe the cells are an inextricable part of us. “If we were able to test lots of samples from multiple points in time and many different sources, we believe we would find microchimerism in most, if not all, individuals,” says Nelson. “I would guess it is ubiquitous.” What is clear is that the cells get everywhere, have staying power and seem to be associated with both good and poor health. Earlier this year, a study of 26 women who died during pregnancy or within a month of giving birth found cells from their children in every organ tested, including the brain (see “Resident aliens”, right). Other research has shown >

Resident aliens Many organs in our bodies contain cells acquired from other people – but what are they doing? Brain Cells from fetuses make their way into the mother’s brain. They have been found in several brain regions and may provide protection against Alzheimer’s disease. They can turn into neurons in mice, but we don’t yet know if the same happens in humans. Lungs This organ holds more foreign cells than any other, possibly because it contains the first bed of capillaries that blood travels through after leaving the placenta. More blood also passes through the lungs than many other tissues. It has been speculated that microchimeric cells could carry out repairs here. Breast Alien cells here have been linked to lower rates of breast cancer. Fetal cells could lengthen lactation and reduce the chances of a mother becoming pregnant again too soon after birth. Think of it as extreme sibling rivalry: the child’s cells are preventing the conception of a new sibling who would sap the mother’s time and energy. Uterus Fetal cells have been found in the endometrium, the inner lining of the uterus, where they could interfere with the implantation of a new embryo. More sibling rivalry. Heart Cells transferred from child to mother can repair her damaged heart tissue. Skin A 2014 study found evidence that microchimeric cells help repair the body after a caesarean section. They are also often found in skin cancers, but further research is needed to discover whether they offer any protection. 9 January 2016 | NewScientist | 27

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Patrick Tourneboeuf/Tendance Floue

Together forever: I am you and you are me

You are multiple, but why? You are more than the sum of your cells. This idea came to prominence in mid-90s, when molecular biologist Richard Jefferson realised that the microbes inside and on us play an integral role in how healthy we are. Jefferson called the sum of our genes and our microbes’ genes the hologenome. He argued that since our microbes influence health, they also influence our survival and therefore our evolution; we evolved together with them, in a kind of symbiosis. Microchimerism adds the other human cells within us to the mix. After all, they influence our fitness too (see main story). But why did this evolve in the first place? Hilary Gammill at the University of Washington in Seattle suggests that microchimerism boosts fitness by linking a mother’s and her child’s ability to fight infections. “It serves both fetal and maternal interests to help mum survive long enough after the birth for the child to

become independent,”she says. Sometimes, the evolutionary interests of mother and child work in opposite directions, says David Haig at Harvard University. In an evolutionary sense, it pays for a mother to have several children – that way, her genes have a greater chance of survival. But from a baby’s point of view, it’s better if mum doesn’t get pregnant again right away. If she does, attention and resources will be divided. Thanks to microchimerism, says Haig, this rivalry between present and future siblings may be played out in the mother’s body, where fetal cells have been found in both breast and uterus. He speculates that in the breast they could prolong lactation, during which a woman is less fertile. And, he says, fetal cells in the inner lining of the uterus could prevent embryos implanting. “I tend to think of the body as a bit of a collective entity, with different agents having different agendas,” says Haig.

that microchimeric cells can survive for 40 years. People who have more of these cells tend to be more prone to certain types of autoimmune disease, but have a lower risk of breast cancer and thyroid cancer, and may even be longer-lived. The trouble is that many of the earlier studies mainly looked at associations between the number of microchimeric cells in people and the incidence of disease. They stopped short of zooming in on what the cells are really up to. That is now changing. At Mount Sinai Hospital in New York City, Hina Chaudhry studies a condition called peripartum cardiomyopathy, in which a pregnant woman’s heart becomes weakened and enlarged. “Fifty per cent of women spontaneously recover, and no one knew why,” says Chaudhry. The condition has the highest recovery rate of any form of heart failure. To see if microchimeric cells from the fetus could be somehow coming to the mother’s rescue, Chaudhry tagged mouse fetal cells with a green fluorescent tracer to track any that crossed into the mother mouse’s bloodstream. Then she induced heart attacks in the pregnant mice. Sure enough, the fetal cells homed in on the damaged heart tissue where they turned into different types of heart cells. “It’s fascinating: they know exactly where to go on their own,” says Chaudhry. Chaudhry’s most recent studies have shown that a fetus provides a reservoir of embryonic stem cells to the mother. Trophoblast stem cells usually sit on the outer layer of the fetus. During pregnancy, they implant into the wall of the uterus and give rise to the placenta. In her pregnant mice, Chaudhry has found that it is these cells that make their way into the mother’s

“Fetal cells race to the mother’s heart and form brand new muscle cells” bloodstream, race to the heart and form brand new beating muscle cells. She believes that the damaged heart tissue may release proteins that act as a beacon to the fetal cells. Her hope is that these studies may one day lead to stem cell therapies that treat different types of heart disease. Nelson is particularly interested in what fetal cells are doing in their mothers’ brains. In 2012, she performed autopsies on the brains of 59 deceased women, and found that 63 per cent of them had signs of alien DNA. A 2005 study in mice found fetal cells turning into

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A family affair Swapping cells isn’t just limited to a mother and her child (see main story). Connections may reach much deeper into your family tree. Take, for example, a woman pregnant with a baby girl, her second child. We know that microchimeric cells can stick around for decades, so it’s easy to imagine cells from her eldest still running around her body. They could get transferred to her new baby. If the eldest was a boy, the daughter now has cells from her brother. These could conceivably be passed on when the daughter has a child of her own – who would therefore have cells from their uncle. David Haig at Harvard University points to this scenario as a hiccup in studies that assume Y chromosomes found in a woman’s bloodstream must have come from her son. “One thing that I think is crying out to be done is to identify exactly who the cells are from,” he says. The odds of carrying your sibling’s cells are probably low, says Lee Nelson

at the University of Washington, Seattle, but studies suggest it does happen. Rather than just one other human, we could have a whole family album’s worth of cells inside us, all exerting an effect on us (see diagram, right). “Another thing to consider,” she says, “is that microchimerism can also occur after a miscarriage.” The same is true for abortions. In both cases, a woman would carry the cells of her unborn child, and any subsequent pregnancies conceivably could pass those cells on to the next generation. It doesn’t stop there. Twins can share cells in the womb, which they then carry out into the world with them. Finally, consider the fact that more pregnancies begin with twins than end with them. In rare cases, one fetus simply vanishes, absorbed by the mother, the placenta or the other twin. These “vanishing twins” may in fact leave traces of themselves, in their mothers and brothers and sisters.

neurons in their mothers’ brains. So could the same thing be happening in humans, helping to form the cells that carry information about your senses, your movement, your thoughts? Nelson and her team are now looking to see if this is the case and are expecting results in the next few months. They are also looking in the opposite direction, to see whether maternal cells reach the brains of their children. “I wouldn’t be surprised if there were maternal cells in the brain,” says Nelson, “and I wouldn’t be surprised if they were an important part of normal development.” How microchimeric cells interact with our immune system is also a key point of interest. After all, the immune system is there to defend our bodies from invaders, yet microchimeric cells seem impervious to it. That’s promising for things like organ transplants, but how do the cells dip below the immune system’s radar? Nelson’s colleague Hillary Gammill points out that microchimeric cells can turn into a type of immune cell: they literally embed themselves into our body’s defences. Chaudhry is currently looking at the molecules on the surface of microchimeric cells to try to get to the bottom of this. The health benefits and downsides may not

Family ties You could have cells from various relatives coursing through your blood A woman can pass cells on to her children and have cells from her children and mother in her body (solid lines). She could theoretically even have cells from older siblings (dotted lines)

DECEASED The cells of a dead child could have transferred in the womb to the mother, so can be passed on to her subsequent children – though this is likely to be rare

be limited to mother and child. Gammill has looked at how a woman’s cells could give a helping hand to the next generation when she becomes a grandmother. Pre-eclampsia is a complication seen in 6 per cent of pregnancies. In a study of women who developed the condition, Gammill found that none of them carried cells from their own mothers. By contrast nearly a third of the women in the study who didn’t get pre-eclampsia did. Intriguingly, in these women, the number of their mother’s cells in the blood got a boost during the pregnancy’s third trimester, when pre-eclampsia is most common.

Protective hand The results raise the intriguing possibility of some kind of protective hand being extended to the fetus from their grandmother, says Gammill. Jen Kotler at Harvard University is using the same green fluorescent tags as Chaudhry to trace cells across generations, and see whether cells from grandparents can end up in the brains of their grandchildren. Why does microchimerism happen at all? Kotler’s colleague David Haig points out that evolutionary pressures may be at play (see “You

Men get cells from their mother and possibly older siblings

are multiple, but why?”). “You might expect that [fetal cells] will be enhancing bonding of the mother to the child,” says Haig – thus increasing the child’s chance of survival. “We know there are changes in the brains of mice after pregnancy that are involved with the delivery of maternal care,” says Haig (see “The real baby brain”, page 36). “We are raising the possibility that offspring cells could be having a say in the matter as well.” For Nelson, the weird world of microchimerism turns our understanding of the “biological self” on its head. “To me, the best working paradigm is that we are an ecosystem,” she says, one made up of a patchwork of humans and which can have both positive and negative effects on our health. “Microchimeric cells are present in fairly low numbers, so that will tend to limit their influence,” says Haig. “But small numbers of cells can have big influences. ” In future, we may be able to invite new helpful humans to join our body’s ecosystem, and encourage less helpful ones to leave. Being human is about to get a whole lot more complicated. n Andy Ridgway is a freelance writer based in Bristol, UK 9 January 2016 | NewScientist | 29


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Light fantastic Radio waves are an ace way of bouncing information through the air. Could light be even better, asks Nicola Jones


LEXANDER GRAHAM BELL was certain his greatest invention would change the world. He was almost right. The telephone was indeed revolutionary, letting people talk to each other across great distances as if they were in the same room. Unfortunately, Bell thought his greatest invention was not the telephone, but the photophone. That was a complete flop. Perhaps it was just ahead of its time. Because the basic idea behind it – using pulses of light to bounce information through free space – is once again set to change the way we communicate. Radio waves have been the medium of choice for sending signals wirelessly for the best part of a century. But we’re rapidly reaching a crunch in how much data we can send. That, with advances in LEDs and lasers, mean light is starting to beat radio hands down, at least for some applications. Using light you could download the equivalent of a DVD box set in the blink of an eye. The ability to send digital signals could also be built into street lights and lighting in homes and offices, giving us internet coverage almost anywhere. And since our walls aren’t generally transparent, light could be ideal for keeping communications secure. Those championing visible light communication, or Li-Fi, envision a bright future. “Everywhere I see a light I see Li-Fi,” says Harald Haas at the University of Edinburgh, UK, one of the technology’s main advocates.

For Haas, light offers an alternative to radio that will let our devices exchange massive data streams without interruption. It opens up new possibilities too. For example, Li-Fi built into traffic lights and car brake lights would allow smart cars to receive traffic updates and exchange dash cam views.

Crunch time But there are big questions. Though demonstration versions of the technology work well, the cost of components remains prohibitively high for most applications. Even when prices fall, as they inevitably will, does it follow that the telecoms industry will switch its allegiance from radio? Mobile communications using lowfrequency electromagnetic waves – radio waves – is a spectacularly successful technology. You might say too successful. If you’re at the airport and can’t make a call or connect to the internet, a spike in newly arrived passengers has probably used up the capacity of the nearby cell towers that provide mobile signals. With more and more people sharing photos and streaming video – not to mention the internet of things, from cars to kettles, starting to talk to each other in the background – the problem is getting worse. “We’re throttling the capacity of our devices,” says Thomas Little at Boston University. There are a bunch of ways to solve this

problem. A lucrative one, for governments at least, is to reallocate slices of the radio spectrum, pinching bits from sectors like the military and auctioning them to the telecoms industry. In January 2014 an aggressive bidding war in the US over a chunk of bandwidth ended with a handful of companies coughing up a record-breaking $45 billion to the US Federal Communication Commission.

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getty images

Alternatively, multiple messages can be encoded in the same bit of radio spectrum. But implementing that requires ever more sensitive and expensive-to-develop devices like 4G phones. In any case, we are already close to the theoretical maximum number of things that can be overlaid in a single signal. Yet another option is to pack the landscape with cellular towers, so that fewer users have to share any one antenna.

For short-range communication, we can shimmy a little way along the electromagnetic spectrum to slightly higher frequencies, in the microwave region (see “Visibly better”, page 32). Wi-Fi is the current king of this arena. But even though it only has a modest range of 50 to 100 metres, you still hit interference problems when there are multiple networks close together, or many users at once. Shift along to still higher frequencies, and

you get to infrared and visible light – a part of  the spectrum that is uncongested and unregulated. “Radio and light are the same stuff,” says Texas-based technologist Kevin Ashton, whose work at the Massachusetts Institute of Technology in the late 1990s drove the widespread adoption of radio-frequency identification (RFID), now used in contactless payment systems, for example. “We’re not saying Li-Fi is a replacement > 9 January 2016 | NewScientist | 31

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for radio,” says Haas. “But this will provide relief elsewhere.” Haas, who coined the term, has been working on the technology at his lab in the Alexander Graham Bell building at the University of Edinburgh – a fitting place for the revival of an old technology (see “Speech by sunlight”, right). He foresees that five or 10 years from now, our devices will not only hook up to cellular towers and Wi-Fi networks, but to light bulbs. He isn’t alone in thinking this way. “We’re already spending all this money to light a room and send photons everywhere, so why not embed data in it?” says Little. Li-Fi works by turning an LED bulb off and on to create a stream of bits for data transmission. The principle is just the same as sending a Morse code signal by flashing a torch – except that it happens billions of times a second. The faster the flicker, the more data you can send, and at the speeds in question there should be no danger of the flashing triggering epilepsy in susceptible people. Although a pioneer of the technology, Haas didn’t invent it. He credits Japanese researchers at Keio University and IBM for laying the groundwork in the 1990s. Haas became involved in 2000, when he was working for Siemens. It was around then that three things happened: the practice of sending and receiving photos and video with our phones started to take off, the prospect of a spectrum crunch raised its head, and white LEDs came on the market. Haas started playing around with those lights. His breakthrough was figuring out how to modulate the output of a single LED so it could carry multiple data streams at once. In 2006, he demonstrated this using an LED bulb fitted to an off-the-shelf desk lamp. He used it to transmit some cartoons, he recalls. Since then, Haas has regularly given talks to

Calling LONG-DISTANCE For fast off-planet conversations, sometimes only light will do. In 2013, NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) demonstrated this by sending a message back to Earth by laser. Using near-infrared rather than visible light, in part to avoid blinding anyone, it was able to transmit data at 600 megabits a second – six times faster than NASA’s Lunar Reconnaissance Orbiter, for example, which relies on radio waves. By the time LADEE’s laser signal arrives from the moon, it only amounts to a few photons per bit of information – but that is enough for NASA to pick up using relatively cheap 40 centimetre optical telescopes . For NASA, laser light communication has been a long time in the making. NASA cancelled projects in this area in the 1970s, 1980s and 1990s, says Don Cornwell, mission manager for LADEE. But advances in telecoms tech

brought fibre-optic cables and better lasers, ones that NASA could repurpose if they proved robust. “We bought them off the shelf and saw which ones survived a shake and bake,” says Cornwell. Radio waves tend to fan out with distance, whereas lasers keep a needle-like focus, making them the better option the further you go, says Cornwell. Plus lasers operate outside of the spectrum crunch (see main story), something even NASA has to contend with when using radio frequencies. Cornwell says firms have been calling NASA for advice on how to make laser communications work – including Facebook, which wants to use laser-equipped drones to beam the internet out of the sky to remote sites in Africa or Asia. “A lot of companies are looking into this Sky-Fi,” says Cornwell.

the public about the technology’s potential, and in 2012 he founded a spin-out company, now called PureLiFi, to develop products for the consumer market. But while PureLifi does have a few niche customers, the tech has yet to make a splash with the public. Ashton for one remains to be convinced that Li-Fi will have the kind of impact Haas and others expect it to. “A new technology with no installed base has to be very, very special to overcome all the advantages of incumbency,” he says. “There

may well be certain conditions under which visible light is a far better solution than any alternative, but it’s not yet clear what they are.” Forging an entirely new kind of connectivity for cellphones and other wireless devices is certainly a tall order. But Haas is undaunted, given the potential pay-off. In a lab test last year, Dominic O’Brien at the University of Oxford and colleagues demonstrated an infrared data link able to carry 224 gigabits a second – fast enough to download several hours’ worth of high-quality video in an

Visibly better The radio bands we rely on for commercial wireless communication are now highly congested. Switching to Visible Light Communication (VLC), also called Li-Fi, leaves the problem behind and can offer even faster data transfers Radio

Frequency (Hz)





700-2600 MHz






Visible light


2.4-5 GHz



Laser light communication



Range 1000-10,000m

Range 30m

Range 500,000+ km

Range 10m





Up to 100 Mb/s

Up to 7 Gb/s

The most common form of short-range wireless communication


~300-700 THz

Mobile 4G (LTE)

Highly regulated, crowded part of the spectrum


Up to 600 Mb/s

Used by NASA and ESA to communicate with spacecraft

Up to 200+ Gb/s

Uses near-infrared and visible light – unregulated parts of the spectrum. Blocked by walls

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Ear this: Bell‘s photophone transmitted voices wirelessly using light

Mary Evans Picture Library

Speech by sunlight

instant. In principle, visible light should give similar results. The researchers think that the technology could theoretically transmit at 3 terabits – trillions of bits – a second. Using standard LEDs, Haas has built relatively cheap devices that transmit at rates similar to existing home Wi-Fi. For applications such as streaming video to multiple users, however, their performance can be significantly better because, rather than sharing a Wi-Fi router, each user can connect to their own light source. A dedicated streaming box could then talk to each light via the electrical cabling, sending video streams to every user simultaneously at rates equal to what a single user hogging a Wi-Fi router would enjoy. “That capability has been shown, and now it’s about making applications,” says Haas. One of these is a Li-Fi demo Haas is building for the San Francisco basketball team Golden State Warriors, who are planning a new stadium for 2018. By harnessing the thousands of light bulbs in a stadium, you would get far better performance than Wi-Fi, he says: everyone could connect to the lights to watch instant video playbacks on their phone, for example. Indoor location-tracking is another promising application. GPS does not work well indoors, and its error margin can be too big for practical purposes in any case. But the lights above your head can “see” exactly where you are. If you are in a supermarket, say, they could talk to your phone and send coupons to it for products on the shelf that you happen to be passing. Since little data needs to be

transmitted, such systems can be set up relatively cheaply. Philips is testing one at a Carrefour department store in France. If you don’t like that idea, Li-Fi could also boost privacy. Wi-Fi leaks through walls, letting people easily hijack or eavesdrop on signals. But light cannot escape a windowless room, making Li-Fi a straightforward way to keep wireless communication secure. Some companies are already using it for this reason, says Little. The technology would suit places like hospitals or airplanes, where privacy is key and radio interference can be a problem. Haas adds that certain intelligence services are also interested.

Traffic signals The killer app, however, may be smart cars and roads. Almost every car-maker now has a division trying to beef up vehicle-to-vehicle communication, which will allow cars to share info about busy routes or dangerous road conditions. With Li-Fi, brake lights could notify the computer in the car behind that they are braking, for example. And LED traffic lights could broadcast details of congestion or roadworks ahead. Since Li-Fi relies on the user being able to see the light source directly, it is less prone than radio to interference in crowded areas. “It’s likely that cars are in a congested area, and that’s where you get a problem with interfering radio signals,” says Little. In the meantime, the first mass market Li-Fi products are already on the market: toys and games. Hasbro sells an electronic Scrabble-

Having invented the telephone, Alexander Graham Bell moved on to something even better – or so he thought. In 1880, Bell showed off his photophone for the first time. It sent his voice through the air to a colleague 200 metres away who was holding a telephone connected to a big dish – the first wireless phone call. The photophone worked by turning speech into vibrations in a diaphragm, then bouncing light off it. A receiving diaphragm caught the reflected beam, which contained subtle variations encoding the vibrations, and converted it back into the sound of the speaker’s voice. Bell thought the photophone could replace expensive telephone cables. But since the electric light had only just been invented and domestic lighting was still some years away, he had to rely on sunlight to make the system work. “I have heard articulate speech by sunlight! I have heard a ray of the sun laugh and cough and sing!” he wrote at the time. “I have been able to hear a shadow and I have even perceived by ear the passage of a cloud across the sun’s disk.” But clouds were also the photophone’s downfall. It couldn’t be used when the sun was obscured. Still, Bell was so proud of the photophone that he wanted to name his second daughter after it. Luckily for her, Bell’s wife thought otherwise and they named her Marian instead.

style game, in which the tiles have small LED lights that let them talk to each other to determine if they are in a sequence that spells a word, or not. Disney has a small team working out ways to use LED lights in their parks to send videos and games to the phones of people waiting in lines to keep them entertained. They are also developing table lamps that talk to toy cars with headlights that in turn talk to your computer. These few examples aside, it will be a year or two at least before the costs of LEDs and Li-Fi chips come down enough to make mass adoption viable. Even Haas doesn’t yet have a Li-Fi network, or even a Li-Fi enabled desk lamp, at home. But he’s thinking about it. “The kids would love it,” he says. n Nicola Jones is a writer based in British Columbia 9 January 2016 | NewScientist | 33

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AGGIE XENOPOULOS straps on a pair of hip-waders, grabs a 1-litre plastic bottle from her truck and wades into Ontario’s Nottawasaga river. “See this brown colour?” she says, scooping up water the colour of weak tea. “That’s dissolved organic carbon. It blocks UV rays. It’s a bit like SPF for aquatic life.” That’s not all it’s good for; this murk is also a basic food source in rivers and lakes. Unfortunately, it is possible to have too much of a good thing. Dissolved organic carbon, or DOC, naturally leaches into waterways from surrounding soil as dead plants decompose. But in recent years,

the process has gone into overdrive. Xenopoulos, an aquatic ecologist at Trent University in Ontario, has been sampling rivers throughout the province for the past 12 years and has documented a steady rise. So too have scientists in other parts of North America and Europe. The consequences could be far reaching. As well as damaging aquatic ecosystems, it is likely to increase the cost of water treatment, and could even contribute to global warming. The irony is that this so-called “browning” is in large part the result of an environmental success story: the reduction of acid rain.

Acid rain began increasing in the mid-1800s as the Industrial Revolution took off, powered by fossil fuels. Burning these hydrocarbons, especially coal, produces sulphur dioxide and nitrogen oxides, which react with water in the atmosphere to produce acids. By the 1970s, it was apparent that this was damaging trees and aquatic ecosystems, and governments started enacting legislation to clean up smokestacks. Acid rain began to decrease. But there was an unforeseen consequence. In many temperate Rivers and lakes started to become browner when we cracked the problem of acid rain

Murky waters

Vincent J Musi/National Geographic Creative

Why is the world’s fresh water getting less clear? Sharon Oosthoek fishes for answers

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Vicious circle: global warming makes rivers dirtier and this in turn increases warming

Todd Korol/Aurora Photos

and subarctic areas, deposits of sulphur had changed the chemistry of soils, making them “stickier”, says Chris Evans, a biogeochemist at the UK’s Natural Environment Research Council. This meant most DOC stayed put, and didn’t run off into surrounding rivers and lakes. But as soil sulphur concentrations dropped, DOC became unstuck. In the mid 1990s, Evans and two colleagues were among the first to notice rising DOC levels. A decade ago, their research revealed that concentrations in 22 rivers in the UK had increased by an average of 91 per cent over the preceding 15 years. Two years later, Evans collaborated with a larger group to reveal that rising DOC wasn’t restricted to the UK. Their results, published in Nature in 2007, showed that 522 remote lakes and streams in North America and northern Europe had seen nearly a doubling of DOC concentrations between the 1990s and 2004. They also firmly tied the trend to decreased sulphur deposition, which had halved during the same period. You might think that browning would abate once the excess DOC had been flushed out of the soil, but that hasn’t been the case. Instead, climate change is thought to have continued the effect. Increased growth in vegetation due to greater availability of carbon dioxide, longer growing seasons and heavier rains could all be behind excess DOC flushing into rivers and lakes. “Anything that causes DOC production to go up will have a greater effect as soil stickiness is gone,” says Evans, who likens it to widening the drain in a bathtub.

no food at the base of the food web. The opacity of the water causes another problem: it narrows the warm, oxygenated top layer of a lake – prime fish habitat (see diagram, below). “It’s sort of a double whammy,” says Stuart Jones at Notre Dame University in Indiana. “Lack of light means [photosynthesising] phytoplankton can’t grow, so they make less food and they also can’t make oxygen, so there is less suitable habitat for fish.” No one yet knows what the threshold

Deep trouble Lakes and rivers are becoming browner as more dissolved organic carbon (DOC) enters them. This stops warming sunlight penetrating as deeply, shrinking the upper layer where aquatic life flourishes Light


Global browning The link between browning and climate change is yet to be confirmed, but one thing is clear: more browning is bad news. One survey of 168 lakes in Norway found that while initial increases in DOC were linked to increases in brown trout numbers, continued rises caused the population to steadily drop. The initial benefits were probably due to DOC’s ability to block UV rays and the fact that when it drains into watercourses it often brings phosphorus and nitrogen too, key nutrients that fuel the growth of organisms at the bottom of the food chain. However, DOC levels reach a tipping point when the water turns a deep brown, says Anders Finstad at the Norwegian University of Science and Technology in Trondheim, who led the study. This prevents sunlight from reaching bottom-dwelling algae and, if the water is dark enough, free-floating plankton. No sunlight means no photosynthesis, and

Warm Thermocline Cold


High DOC

Warm Thermocline Cold

for this switch from positive to negative effects is, although scientists expect it will be different for each ecosystem. Finstad, for example, found that shallow lakes switch at higher DOC loads than deeper lakes, probably because light doesn’t have to travel so far to reach the bottom. And aquatic life isn’t the only thing to suffer as a consequence of browning. With less light penetrating the water, phytoplankton die and non-photosynthesising aquatic bacteria start to dominate. These gorge on a banquet of DOC, producing carbon dioxide as waste, which enters the atmosphere where it can contribute to global warming. In other words, climate change seems to be increasing browning and browning, in turn, increases climate change. That’s not all. Rising DOC levels will raise the cost of making water safe to drink. Chlorine – a common disinfectant – reacts with DOC, leaving toxic by-products. To prevent this happening, iron and aluminium sulphate are added to the water, forcing DOC to clump together and drop to the bottom. Surface water can then be safely treated with chlorine. More will be needed if browning intensifies, and that will be expensive. So what can we do, given that increasing acid rain isn’t an option? Some scientists suggest that we should restrict development in sensitive watersheds as digging tends to hasten the release of DOC. Others say we need to reduce fishing quotas in freshwater fisheries to avoid crashes in populations. All agree we need to pay closer attention to browning. “If this continues, we’re going to have dramatically different lakes and rivers,” says Xenopoulos as she sloshes her way up the bank of the Nottawasaga. “This is going to be a big story.” n Sharon Oosthoek is based in Toronto, Canada 9 January 2016 | NewScientist | 35

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The real baby brain Motherhood messes with your mind – but not in the ways you might think, says Emma Young


HE was still a fairly new graduate student at Tulane University in New Orleans, Louisiana, when her mentor handed her a paper. “As I skimmed it, I realised it was about cognitive impairment associated with pregnancy and motherhood,” she says. “I also realised no one else had been given the paper.” Katherine Tombeau Cost was several months pregnant at the time, so her mentor intended the paper to be a joke between friends – but it got her thinking. It’s widely assumed that pregnancy and motherhood turns women into sieve-brained shadows of their former selves: the condition variously called “mummy brain” or “baby brain” is a familiar staple of popular culture. But when Tombeau Cost started digging through the scientific literature, she found little evidence to support it. Indeed, she found evidence to the contrary – at least in rats, which become mentally sharper after giving birth. “There had to be another side of the story,” she says. So she set out to find it. The picture that is emerging tells a very different story about “baby brain”. The research also holds promise for understanding postnatal depression, and even factors that contribute to healthy brain ageing in all women. Busting the myth, then, could advance society in more ways than one. It’s true that pregnant women and new mothers often report cognitive problems. In surveys, up to four-fifths of pregnant women report that they have more trouble remembering phone numbers or stringing a complex sentence together than before they got pregnant. Those results appeared to be bolstered by a widely cited 1997 study revealing that women’s brains shrink by up to

7 per cent over the course of a pregnancy. All this would have been news to Craig Kinsley. It was watching his wife and newborn daughter that started Kinsley, a neuroscientist at the University of Richmond in Virginia wondering about cognitive improvements brought on by motherhood. “I watched her with the baby, and she knew almost instinctively what to do. And I watched her doing everything she did before – working and now also taking care of the baby,” he says. “It got me thinking: from a rat standpoint, what changes would benefit a mother rat?” That was what led Kinsley to do the research that later attracted Tombeau Cost’s interest. In his years of studying the neurobiology underlying social behaviours in rats, his animals had never shown any evidence of baby brain. Quite the opposite, actually. Although rats in the final phase of their pregnancy show a slight dip in spatial ability, after their pups are born they surpass nonmothers at remembering the location of food in complex mazes. Mother rats are also much faster at catching prey. In one study in Kinsley’s lab, the non-mothers took nearly 270 seconds on average to hunt down a cricket hidden in an enclosure, whereas the mothers took just over 50 seconds. A new wave of research, by Kinsley’s team and others, is now also showing that mother rats are bolder. Placed in a stressful situation, they show less fear and anxiety, have lower levels of stress hormones in their blood, and display less activity in brain regions that regulate fear and anxiety, such as the amygdala. What underpins these dramatic changes? Kinsley and his colleague Kelly Lambert at >

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Brett Ryder

9 January 2016 | NewScientist | 37

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Baby-proof A woman's brain shrinks slightly during pregnancy but soon bounces back, better than ever

Final trimester Brain loses 7% of its volume on average relative to before pregnancy

Six months after birth Brain regains its original volume, and areas involved in cognitive and processing emotion have formed dense new neural connections Reasoning, judgement and emotion regulation Ventrolateral Dorsolateral prefrontal prefrontal cortex cortex

Emotion recognition and empathy Insula Superior temporal gyrus Thalamus

Emotion regulation Hypothalamus Amygdala

Learning Substantia nigra

end of the story. Between about three weeks and four months after birth, some regions bulk up: including those that play a role in reasoning and judgement, empathy and regulating emotions (see diagram, below left). In adults, such rapid changes in grey matter normally occur only as a result of major events like illness or brain injury. It just goes to show that “pregnancy is not just some minor event”, as Kinsley puts it. “These changes represent a separate developmental period every bit as important as sexual differentiation or puberty.” But do they lead to the same kinds of emotional and cognitive improvements found in rats? Laura Glynn at Chapman University in Orange, California, has found that, as in rats, women in the last trimester of pregnancy tend designed to replicate the rat work. For example, to emulate the maze task, Tombeau to be much less stressed. This is down to a Cost put women into a virtual pool of water dampening of the hypothalamic-pituitaryto find a hidden platform on which to rest. adrenal axis, the system responsible for the flight-or-fight response. These changes appear She painstakingly measured the distance the women travelled, the time it took them to find to last beyond pregnancy, although for precisely how long remains unclear. Intriguingly, human mothers also become “Women became bolder more aggressive than non-mothers when and more emotionally provoked (Psychological Science, vol 22, resilient after giving birth” p 1288).They also become bolder and more emotionally resilient. This all makes the platform, and a host of other factors. evolutionary sense, says Lambert, because a Her results, not yet published, were tough mother would better protect her offspring, and a blunted stress response would consistent with all the earlier work on humans: no matter how she did the make her more resilient and able to cope with experiment, she found neither impairments the many demands of her baby. This benefits nor improvements in the women’s spatial her child in more ways than one, as severe ability. maternal stress during and after pregnancy The reason, when she finally saw it, has been shown to harm the baby’s physical was blindingly simple: of course the skills and mental health. motherhood boosts in women won’t be the same ones it boosts in rats. Female rats raise Brain boost pups alone, without help from the fathers or However, the similarities with rats end there. other rats. Boosts in spatial awareness and Lab experiments generally have not found memory help her find food and get back to women’s cognitive performance to be either her pups speedily. Humans evolved to live in impaired or improved during pregnancy or groups, so mothers don’t face the same early motherhood, either in spatial reasoning evolutionary pressures. or memory. The few reliable results that do So what brain changes would help a human show a dip relate to verbal memory, in the mother raise her infant? It’s early days, but third trimester and in the few months after experiments are yielding clues. Starting in late giving birth, but it is as slight as it is pregnancy, women get better at detecting fear, temporary. This is probably a consequence anger and disgust in computer-generated of the major brain changes that takes place faces, though their ability to detect surprise during pregnancy, says Glynn. and positive emotions such as happiness So, intrigued by Kinsley’s rat research, doesn’t change. This makes sense, says Glynn: Tombeau Cost set out to discover whether “If you’re trying to protect your infant, you maternity might improve women’s spatial want to be able to detect a threat.” ability. She gave pregnant women, Motherhood may also make women more breastfeeding mothers and women who had strategic, helping them take the demands of never been pregnant a host of challenges having a baby in their stride with little or no Denis Bourges/Tendance Floue

Randolph-Macon College in Ashland, Virginia, believe it is the tide of hormones unleashed during pregnancy, including oestradiol, which soars to levels hundreds of times higher than normal. Then there’s oxytocin, which primes the brain to transform rapidly in response to sensory stimulus from the pups: areas involved in memory and cognition undergo major changes in rat mothers, forging more connections between neurons. Pregnancy and motherhood prompt a number of changes in women’s brains, according to recent MRI studies. Quite why the brain shrinks during late pregnancy isn’t well understood, but this shrinkage is now known to be temporary. By about six months after a woman gives birth, her brain will have regained its original size. But that’s not the

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Contrary to popular opinion, it won’t scramble your brain

Jean-Luc Bertini

impact on the way they cope with existing pressures in their lives. As yet, there are no studies probing this, but Lambert and her colleague Massimo Bardi are designing new experiments. They are intrigued by research on owl monkeys, showing that mothers are better than non-mothers at identifying big stores of food and devising effective strategies to get them. There’s a good chance that this research will generalise to humans, not just because we are primates too: unlike rat dads, owl monkey fathers contribute equally to the raising of the offspring. Glynn is also leading work to fill in some of these gaps. For example, she is giving a group of pregnant women a battery of tasks designed to investigate abilities such as strategic planning and multitasking, and will follow their performance for at least a year after birth. Our lack of understanding of the full impacts of motherhood on the brain is a sore point for her. “In my opinion it’s almost a crisis in women’s health,” she says. “How can we not know the answers?” That’s because the implications of baby brain go far beyond a bit of fuzzy thinking. Around a fifth of women experience postnatal depression within three months of giving birth. In the UK, suicide is one of the leading causes of death in new mothers. Abnormal levels of hormones associated with pregnancy may be to blame. In proper amounts, these are critical for fetal development and other aspects of the pregnancy. For example, corticotropinreleasing hormone – secreted by the hypothalamus – rises dramatically during pregnancy, which seems to play a role in making the mother-to-be feel less stressed. But an abnormal spike in its levels is associated with postnatal depression, Glynn has found. A better understanding of the

maternal brain and of what hormone levels are beneficial could improve our strategies to prevent the condition. It could also augment our understanding of the factors that contribute to healthy brain ageing. Research on the impacts of pregnancy on a woman’s health later in life is just beginning, but Liisa Galea at the University of British Columbia in Vancouver, Canada, has found evidence that having children alters women’s hormone levels for years. “It shouldn’t be surprising that researchers are seeing long-lasting effects of motherhood,” she says. For Kinsley’s rats, the cognitive improvements lasted well into old age. “We’ve looked at animals up to 2 years of age, which for rats is equivalent to a woman in her mid-80s,” he says. “They still learn more quickly, they’re faster on their feet, and their brains are healthier than in a virgin animal at that age.” Neuroscience backs up these behavioural findings: the brains of older rat mums look healthier than those of nonmothers, containing fewer deposits of amyloid precursor protein, which in humans is linked to Alzheimer’s. However, the evidence from work in humans is contradictory. One study finds a correlation between the number of children a woman has and her Alzheimer’s risk. Other work, by Glynn and collaborator Molly Fox, suggests that breastfeeding may protect against Alzheimer’s – as could more pregnancies. Future studies can unpick these contradictions, says Fox, if they look specifically at the role of maternity hormones on Alzheimer’s. There may be more than just hormones involved – a baby’s cells could be invading the mother’s brain to grow new

neurons (see “The others inside you”, page 26). Either way, a better understanding of pregnancy’s effects on women throughout their lives could unlock new strategies to reduce the risk of the disease. A better grasp of exactly what changes occur with motherhood could even improve our understanding of human evolution, says Glynn. “A reptile that lays eggs and leaves them – you don’t see a lot of complexity in that brain,” she says. Evolving new ways of raising offspring required more neural energy and behavioural changes. Did this new repertoire of behaviours increase the complexity of the animals, or vice versa? “This is profoundly important stuff,” she says.

Myth-busting Busting the myth of baby brain once and for all might also have practical consequences. Plenty of policies are in place to prevent discrimination in hiring practices and protect a woman’s right to return to work after having a baby. However, they don’t address underlying prejudices. “The idea of ‘baby brain’ seems to be prevalent,” says Tombeau Cost. For example, she has found that women who have never been pregnant rate their own spatial ability more highly than pregnant women or those who have had children. How much of this is a consequence of cultural priming and stereotypes that influence women’s perceptions of their own brainpower? And what about the chronic sleep deprivation that accompanies the earliest stages of parenthood? This has been shown to have similar effects on brain functioning as drinking alcohol. Tombeau Cost hopes the new research will assure women – and their employers – that underneath it all, their brains are just fine. Maybe better than fine. The research into the cognitive benefits of motherhood could make women of childbearing age an attractive hiring prospect for employers, rather than a potential liability. For example, the improved threat detection would offer particular advantages in some types of jobs, says Kinsley: “consider fighter pilots and astronauts.” Lambert is uniformly positive. “Being able to be more efficient in your decision-making, being emotionally resilient, maybe being able to engage in different strategies to solve a problem: that sounds like a wonderful executive or manager to me,” she says. n Emma Young is a writer based in Sheffield, UK 9 January 2016 | NewScientist | 39

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Down a very dark rabbit hole Did dark matter kill the dinosaurs? Who cares? This is the grown-up version of science we need to see, says Michael Brooks

HOW do you know if you’re onto something in science? According to University of Manchester physicist Andre Geim, it starts with a feeling: a nagging pull in your gut tells you that your crazy idea is worth exploring. So, with bated breath, you give it a try. The result is usually failure – whether or not the idea has merit. “Then, you may or may not try again,” says Geim in his autobiography. Throughout his career, Geim has tried again with many different projects. Just occasionally, he says, “failures sometimes failed to materialise”. And if you are far enough out from the mainstream when your project fails to fail, it’s far more likely that your surprise success will have some significance – hence Geim’s Nobel for the discovery of graphene. Lisa Randall is certainly far from the mainstream in Dark Matter and the Dinosaurs. She has an as-yet unproven idea about the nature of the as-yet undetected dark matter that may (or may not) make up 80 per cent of the universe’s mass. Then physicist Paul Davies at the University of Arizona suggested this idea might

account for the demise of the dinosaurs. Should that have been the point where she walked away? “Meteoroid hits are challenging enough to investigate,” Randall says. “Coupling them with uncertainties about extinction events is bound to go down a convoluted rabbit hole of trouble.” But she went down the rabbit hole anyway. And, thanks to this fascinating account of the story so far, we can too. It takes a particular kind of nerve to expose your research before it is shown to be right. That’s doubly true when the ideas seem ridiculously implausible at Were dinosaurs wiped out by a first glance. Perhaps Dark Matter comet triggered by dark matter? and the Dinosaurs is a sign that readers of popular science have finally grown up and no longer “the postures we choose to be need pureed “triumph” narratives seen in when the curtain goes up”. of science. Randall has invited us to the After all, it is easy to digest process, not the performance. happy-ending stories of derided We can see the script, the dress speculations that turned out to be rehearsals, the rewrites, the right all along. The uncompleted fluffed lines. And this idea may not even make it to opening night. “Randall has invited us to Randall’s proposal is that our the process... We see the galaxy contains a disc of dark script, dress rehearsals, matter with unusual properties. rewrites, fluffed lines” Instead of interacting solely through gravity, as dark matter is stories are more demanding. thought to, the dark matter in the However, as Randall ably disc has its own set of interactions. demonstrates here, they are Occasionally, the disc exerts a pull ultimately more satisfying: on some of the rocky inhabitants there is something to chew on. of the Oort cloud beyond the Biologist Peter Medawar once solar system’s planets – perhaps ticked off scientists for giving the enough to dislodge a rock and impression that research is always send it hurtling towards a neat by adopting what he called cataclysmic collision with Earth. James Thew/Alamy Stock Photo

Dark Matter and the Dinosaurs: The astounding interconnectedness of the universe by Lisa Randall, Bodley Head/Harper Collins, £25/$29.99

Clearly the idea is not without merit, because it has now been published in what might be the most prestigious journal in physics, Physical Review Letters (although without mention of dinosaurs). The idea that dark matter did for the dinosaurs is “speculative”, Randall admits, but in a good way. After all, if every idea in science were sensible, we would be without quantum physics and relativity. Randall even questions the value of sticking with Occam’s razor, the principle that the simplest explanation is usually the best. “Although scientists tend to prefer simple ideas, they are rarely the whole story,” she says. That said, to her credit she doesn’t fall into the trope of painting herself as a maverick fighting the mainstream. Nowhere in these pages does she

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that was three days after Davies’s question about dark matter and the dinosaurs. And then there’s the simple joy of the idea: “dark matter (yay!), meteoroids (yay!), dinosaurs (yay!). The five-year-old in all of us was intrigued,” she says. In the end, it has turned out to be a very grown-up quest. To answer the central question, we must learn the science of the entire universe: its origins in the big bang, the structure and origins of the solar system, the geology of our planet, the nature of biological evolution, the perils of extinction – and, of course, the biggest mystery in cosmology – dark matter. As Randall puts it, “the physics of

Where the heart is Smart brain imaging is helping unravel the importance of home, finds Adrian Barnett Home: How habitat made us human by John S. Allen, Basic Books, $26.99

HOME. Without doubt, it’s one of the most evocative words in any language. Whether it’s a suburban semi, igloo, yurt or a particular patch of desert, the familiarity and domesticity of home usually provokes relief when you arrive. But why? What is it about being in a specific place that makes us feel so good? Why is being away from home so stressful for some that US psychologists once recognised homesickness as a potent progenitor of mental illness in recent immigrants? All this, and much more, is explained in John S. Allen’s book Home. Allen is a proponent of and researcher in the newish field of neuroanthropology – the study of the relationships between culture and the brain – a science that owes its quantitative existence to

“If every idea in science were sensible, we would be without quantum physics and relativity”

Michael Brooks is a consultant for New Scientist

The familiarity of home often provokes relief when you return

Adrian Barnett is a rainforest ecologist at Brazil’s National Institute of Amazonian Research, Manaus

Owen Newman/Getty

give the impression she thinks she and her colleagues are right – except in pursuing something that is both intriguing and (so far) plausible. As a world-renowned theoretical physicist and her own harshest critic, she has the selfconfidence to lay out the ideas without being overly defensive of the argument. She happily pokes fun at herself, in fact. The stars aligned for this project, she says, and just before it began, a fortune cookie asked her: “What is the speed of dark?” As she says: “I didn’t know then that the words were indeed a sort of fortune, in that they more or less prophesied the research project I was about to commence.” The day she asked her collaborator Matthew Reece if he wanted in on the project was the day the Chelyabinsk meteor entered Earth’s atmosphere – and

elementary particles, the physics of the cosmos, and the biology of life itself all connect – not in some New-Age sense, but in remarkable ways that are well worth understanding”. Randall’s writing is as laid back and unfussy as ever. If you appreciated her clear, straightforward style in Warped Passages and Knocking on Heaven’s Door, you won’t be disappointed by Dark Matter and the Dinosaurs. In fact, she seems to have pared down the flourishes to a minimum. We occasionally see glimpses of her life – her “very messy office” or an intriguing conversation with a taxi driver – but for the most part this is a straightforward primer: an introduction to each of the arguments that makes up her thesis, all tied together with an honest look at the plausibility of the whole. Maybe there’ll be no deep impact in the end, but it’s certainly worth the journey. n

technological advances in brain imaging. Without the ability to localise what, where and by how much, the study of emotional responses lay forever in the qualitative realm. Techniques like MRI, fMRI and arterial spin labelling all allow cunning investigators to start teasing out long inaccessible answers about what it is to be human, how we got this way, and the links to our animal antecedents. Allen uses these tools to explore the privileged place of home in our cognition, while introducing us to as many as 17 emotions, Neanderthal homemaking and five psychological roots of economic cycles. More than anything, research by Allen and his colleagues shows that notions of sanctuary, certainty and the consequent capacity to relax are key to our concept of home, how we identify it and why we need it. An affirming read for the commute home. n

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The meaning of aliens Film-maker Michael Madsen reveals what will happen when aliens finally arrive Who is looking into what will happen when aliens land?

PROFILE Michael Madsen is a Danish conceptual artist and film-maker best known for Into Eternity: A Film for the Future (2010), a portrait of the Onkalo nuclear waste repository in Finland. The Visit: An Alien Encounter is released in UK cinemas on Friday 22 January

An extraordinary number of people have considered this seriously: staff at the UN Office for Outer Space Affairs, legal sources, NASA personnel, space scientists, former military representatives, and experts in space communications and engineering.

Why do aliens so disturb our reality?

Because there’s this gulf between a scientific understanding of life and the way we experience it. In the film I asked Christopher McKay, an astrobiologist with the NASA Ames Research Center, if life was blind to everything beyond its own survival. He said yes, life just wants to live. A human being, in trying to extract amazing knowledge from the universe, is just doing what living things do. It’s investing in its future. It’s expanding.

To be frank, I found it strangely reassuring to find such highly professional people in charge of the political machinery. Politicians may come and go, but civil servants are around forever. They seemed to have a very clear idea of what would happen if we were visited by aliens and how to handle them. How did that make you feel?

The most frightening aspect for me was Beaver's sense of how public panic would cause society to break down. I thought panic leading to Armageddon was just a Hollywood cliché, but the MoD officials I spoke to had seen this process under way during the Bosnian conflicts of the mid1990s. Their assumption – that society tips into anarchy very quickly – was deadly serious and sincere. Beaver and Sheriff told me, more or less, that the varnish of society is very thin: fear cuts through it quickly. So was Sheriff more worried by people than by extraterrestrials?

She knows how to balance risks.


In your new film The Visit: An Alien Encounter, I was most struck by the to-camera contributions of Paul Beaver and Vickie Sheriff, former Ministry of Defence personnel in London.

What's wrong with that? Exercise in the fantastic: real soldiers prepare to meet aliens

If such advanced beings meant us harm, they would have harmed us by now. She’s much more worried that we would harm peaceable aliens by making mistakes. One of your interviewees, Jacques Arnould, a French theologian, said  that when we’re confronted with something alien we need to treat it like a human. Do  you agree?

Why can’t we be objective?

That’s the promise scientific thinking has been holding out to us since the Renaissance: that the world can be understood, and that we can command the world through our understanding of it. In this, our present way of thinking is perhaps just as dogmatic as religious thinking in the Middle Ages, which only permitted certain ways of perceiving and thinking about reality. Meeting a true alien would challenge our assumptions. Before us would be a dynamic agency utterly unknown to us.

I think he was getting at something deeper. Society’s varnish is our willingness to treat each other as beings like ourselves. If you want to communicate with aliens, you have to invest them with “Our way of thinking is human characteristics, because perhaps just as dogmatic where else do you even begin? as religious thinking in The same applies to how you the Middle Ages" treat other people.

Nothing. But it’s not enough. It doesn’t include the fact that we experience life through emotions, dreams and feelings. Towards the end of the film, Chris Welch, of France’s International Space University, imagines entering an alien craft. His thought experiment expresses extraordinary courage and openmindedness. I hope we can bring such an attitude to an alien encounter if it happens for real. And there’s hope in the fact that we conjure up aliens in the first place. We long to be seen by something other than ourselves, because then our own existence is strengthened. Alongside it is this suspicion that perhaps the alien is resting inside ourselves: that while we’re alone in the universe, we don’t truly know who we are. n Interview by Simon Ings

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LETTERS editor’s pick

Accounting for empathy From Jan Karpinski Pat Kane writes that empathy “is one of the few aspects of professional roles that… might survive incremental transformation by information technology” (21 November 2015, p 42). Perhaps the premise is that empathy is an insignificant aspect of what professionals do, hence the prediction that the work of lawyers, doctors, teachers, accountants, architects, engineers and so on will be “decomposed” by information technology (IT). I suspect many readers will be sad to see this happen to doctors and teachers. I also suspect that some will be buoyed up by the thought of decomposing lawyers and accountants. But this reaction might be premature, for a reason that may be rather unexpected. An article by Ian Robinson for the professional body Chartered Accountants Australia and New Zealand tells its members how to spot something amiss. “The first lesson is that it’s not just about the numbers – it’s about the people… Engage your soft side… If something doesn’t feel right in the way people respond to you, note the signals and see where it leads you in your investigations.” If empathy is so important in forensic accounting, might the same be true of other professions? Could IT’s impact be to enhance professionalism rather than decompose it? Shepton Mallet, Somerset, UK

[email protected]

What scientists can say without doubt From Chris Ford Do scientists need training in talking to the media? As a scientist I understand why experts who are asked, “Was Storm Desmond caused by climate change?” answer: “It’s impossible to say whether a particular flood event is or isn’t caused by climate change” (12 December 2015, p 6). But it really doesn’t help. Most people are not trained in scientists’ ways, but are all too well aware of the workings of politicians’ prevarications, and interpret them as a lack of conviction (or even lying). We scientists must wise up. The overwhelming majority of us accept the reality of humanmade climate change, and our communication with the public must reflect this. For example, an answer like “climate change will bring more storms like this” is equally honest but more helpful. Walsall, West Midland, UK

Making labels with simple words From Brian King You interviewed Randall Munroe about his effort to describe things in simple language (28 November 2015, p 32). Languages with smaller vocabularies have long described items that their speakers have not encountered before with constructions such as “iron bird” for aeroplane. Larger languages also use this method: consider the French chemin de fer (iron way), the British-English “railway” and the American “railroad”. “Technical languages” have been developed for rapid communication, such as those used in mines in southern Africa, where safety had to be taught to new recruits who spoke many different languages. Instructors

used mainly local language words, and consequently the terms now used in South Africa are different to those in Zambia. Barton on Sea, Hampshire, UK

What do you call a modified salmon? From Michael A. Crawford The US Food and Drug Administration has ruled that a fast-growing genetically modified Atlantic salmon is safe to eat (28 November 2015, p 9). That may be so. But if it grows so quickly, will it provide the health benefits of Atlantic salmon to those who consume it? Will it have the same proportions of omega-3 fatty acids? Will it have the same amount of trace elements such as iodine, selenium and zinc? If not, should it even be called salmon? Eating fish and seafood is generally recognised as being important for brain development and function because of the nutrients they contain. Unless the modified salmon can match its Atlantic cousins on the brainhealth scale, it should be called something else to inform the consumer. Perhaps “nomlas”? London, UK

On prostitution and the law From Helen Gough I was disappointed that your article “Safer sex work” (12 December 2015, p 26) did not consider the harm prostitution causes. History shows that people will do anything if they need the money: in the past, parents sent their children to work down coal mines or risked life and limb working long hours in dangerous and unhealthy factories. Health and safety laws now protect many of us from such exploitation, but society still needs to answer the question as to



whether it is acceptable to be able to purchase another human being as an object to sexually abuse. I would hope the answer to this would be a categorical “no”. In that case it is appropriate to adopt the “Swedish model”, in which the purchase of sex is a criminal offence – but not its sale. The aim is to reduce demand, discourage sex trafficking and, with funding, enable women to exit the trade. Those who wish to fully legalise prostitution often claim that it is a job like any other. This is simply not the case, since it requires submission to being physically violated, which is why a high proportion of women prostitutes suffer from post-traumatic stress disorder. Those behind the plan to legalise prostitution in Scotland seem to have forgotten that laws are meant to protect the vulnerable, not enable the strong to do whatever they like. Cheltenham, Gloucestershire, UK

Concorde wasn’t quite the cash sink From Brian Clegg As the person who wrote the costing model used by British Airways in the days of Concorde, could I point out that Joshua Howgego got the wrong end of the stick in calling Concorde the classic example of the sunk-cost fallacy (12 December 2015, p 31)? While it is true that the governments and aircraft manufacturers made a loss, it’s not true that Concorde “never made any money in all the decades it was flying”. Swindon, Berkshire, UK

Just a Neolithic street plan, surely From Bryn Glover Your news item on Late Stone Age rock etchings (5 December 2015, p 17) called to mind the “cup-and-

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“Maybe it’s already happened and they’re just allowing us to discover it for ourselves now”  erry Braine suggests that the idea of implanting T memories may be disquieting (19 December 2015, p 28)

ring” stone markings which are common here in the north of England and elsewhere. These are typically a circular groove 60 to 100 millimetres in diameter, with a small break where the groove has not been cut. They can appear singly on stones in isolation, or in groups. My personal theory is that they are Neolithic “street maps”. Could they have been carved to be placed near the tracks into settlements, with each cup-and-ring mark representing a typical hut of the era, and its entrance? If the Barcelona finds date from 13,800 years ago, they will just predate any such UK carvings, as these can only have followed the retreat of the ice sheet. Kirkby Malzeard, North Yorkshire, UK

We’ve seen that Moho before From David Rubin I cheer the crew of the JOIDES Resolution and hope their drill makes it through the Earth’s Tom Gauld

mantle (5 December 2015, p 7). They are not, however, the first geologists to try to drill through the Mohorovicic boundary. From 1958 to 1966 the American Miscellaneous Society ran the Moho project to achieve this. In 1970 the Kola Superdeep Borehole project gave it a shot, only to abandon it in 2006 for lack of funds. Ballston, New York, US The editor writes: n There was no space in that small column to allude to our previous coverage of Moho – for example, (27 February 1964, p 534) – and of the Kola project (5 October 1991, p 15).

Around the world in longer than that From Simon Humphrey The headline “Around the world in 80 microseconds”, which appeared in your story on internet architecture, was somewhat optimistic – to say the least (12 December 2015, p 38).

Take Earth’s circumference to be 40,000 kilometres: covering it in 80 microseconds would require travelling at approximately 1700 times the speed of light in a vacuum (300,000 km/second). The data packets actually take indirect paths through complex fibre-optic infrastructure, so would be travelling even further and at speeds much slower than that of light. An email would be lucky to circumnavigate the world in 0.8 seconds. Wetton, Staffordshire, UK

Dragnet invention: just the facts From James Watt David Hambling’s discussion of less-lethal weapons was interesting and enjoyable (28 November 2015, p 30). It inspired me to make a tongue-incheeky “safe-ish” suggestion: why not a net-firing gun? A net projectile attached to pull cords would cover the culprit when fired. The cords would tighten the net in such a

way as to prevent the individual moving arms or legs. Correct me if I’m wrong (and I’m not often wrong) but the above system ought to be safe for police and security personnel to deploy, and for the general public. Discuss. At my age patenting a device is hardly worthwhile, so regard this idea as a gift… assuming it works. Market Deeping, Lincolnshire, UK The editor writes: n It has been tried, for example by the New York Police Department (3 May 1997, p 7). We note, however, the lack of triumphant updates.

Who or what makes that luck? From Brian Tagg Steve Tunn discusses computer algorithms selecting job applicants (Letters, 12 December 2015). This reminds me of the human resources person who would randomly consign half the CVs they received to the wastebasket, with the explanation “who would want to employ anyone that unlucky?” Maybe the same applies in the algorithmic era too? Taunton, Somerset, UK

For the record n The Autism Sisters Project wants to contact families, initially in New Jersey, New York and Connecticut, that have a son or daughter with autism and an unaffected sister (12 December 2015, p 27).

Letters should be sent to: Letters to the Editor, New Scientist, 110 High Holborn, London WC1V 6EU Email: [email protected] 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.

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more pragmatic concerns about the impact on the local economy. The voice of unreason was indeed loud and clear, however, in a public meeting about the plan. The Roanoke-Chowan News-Herald confirms that one local resident was concerned about draining the sun, while another – a retired science teacher – claimed the panels could interrupt photosynthesis. She “also questioned the high number of cancer deaths in the area, saying no one could tell her that solar panels didn’t cause cancer” – although it seems that beleaguered representatives of the Strata Solar Company did try.

Paul McDevitt

TIN foil hats may have a popular following, but they have struggled to overcome their sartorial inelegance. Kathleen James points us towards a brand that may change that: Shield, which boasts that it has created “the world’s first signal-proof headwear”. The founders of Shield, which has raised over £8000 on Kickstarter, claim that their silver-laced cotton beanies and baseball caps will “reliably reflect signals from cell phones, wi-fi routers, microwaves and it generally blocks all waves transmitted from electric devices”. The headwear is also radar-invisible, which should be useful for people worried that their head is being tracked from military airfields. Any health benefit conferred by the hats is only vaguely hinted at, with the promotional copy optimistically stating that “maybe once it will pay off”. Before we stump up our cash, Feedback has to know: does it also protect against fruitloopery?

THERE’S no shortage of incredible claims in the beauty industry, but even so, credit must go to the

magazine Tatler for finding so many to place on a single page. A spread in their December issue features not only a £28 facial roller made of jade that promises to “expel toxins” and “wake up sluggish skin”, but also a £60 love potion and a chemical-free candle (£60) that looks surprisingly solid. Meanwhile, we are told a £205 “bio-regeneratif serum” is “infused with energy through precious minerals … said to stimulate cell turnover”. Let’s hope that’s a good thing, then. However, Tatler’s tongue may be firmly in its well-polished cheek, because the whole collection appears under the knowing headline “Magic formulas”. WILLIAM F. FAGAN writes – as many of you did – to relay news that a North Carolina town has rejected a solar farm due to fears that it would “suck up all the energy from the sun”. Sadly, the story is too good to be true. The Woodland Town Council did veto the creation of a new solar farm (it has three already), but it was for

Stefan Lorett’s online bank offers a drop-down menu for birth year that starts in 1865. “Thank you, Lloyds,” says Stefan. “I feel young again”

A CASE of counting your eggs – badly. Kevon Kenna relays news from the Melbourne Herald Sun that a faulty test for the number of eggs that a woman produces underestimated the number by “up to 283 per cent”. Were some women told they were producing anti-eggs, Kevon wonders. ECONOMICS may be the dismal science, but John Leaver forwards evidence that it is at least willing to incorporate concepts from the others. Attendees at the Qual360 innovation hub can learn how “consumers are not irrational but quantum probabilistic”. The session promises “ground-breaking advances in understanding complex consumer behaviour through quantum physics!” Feedback is undecided about whether or not to attend – though perhaps we’ll do both.

THE maker of Nurofen painkillers, Reckitt Benckiser, has felt the sting of Australia’s regulators. A range of pills marketed as targeting specific pains all contained identical medication – 342 milligrams of ibuprofen – a practice the Australian consumer protection authorities ruled was misleading. The specific-pain range cost markedly more than Nurofen’s standard pill, leading Feedback to wonder exactly how much it costs to print the word “migraine” on the packet.

THANKS to all of you who wrote in to draw our attention to an outstanding example of nominative determinism: a urologist at the Erasmus Medical Centre in Rotterdam named Dik Kok.

IT IS often quipped that Christmas comes earlier every year, but what of other holidays? Flavio Antonietti tells us that Gold, the UK television channel specialising in rebroadcasting old programmes, has changed its name to Christmas Gold, “where you would expect all the old favourite repeats of various Christmas shows”. Imagine his surprise, then, when he saw the French and Saunders Easter Special scheduled for mid-December. “I know Easter moves around,” says Flavio, “but have never known it to fall in December.”

FEEDBACK wonders what David Taub unwrapped over the holiday period, because he asks: “Is there a word for when you accidentally discover a web page about a topic you really wish you didn’t know existed? For that matter, is there a word for thinking or seeing something you wish you could unthink or unsee?” Feedback needs to know, if only to express how we felt on reading Ray Thomson’s description of intestinal ischaemia in The Last Word – still giving us nightmares (25 April 2015).

You can send stories to Feedback by email at [email protected]. Please include your home address. This week’s and past Feedbacks can be seen on our website.

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Last words past and present at newscientist.com/lastword

THE LAST WORD Rumble of doubt

normally, or is there some scientific method that ensures the youngster doesn’t feel pain? Ken Lee Hervey Bay, Queensland, Australia

How are internal body noises such as stomach rumbles produced, and why can we hear them?

n There is always gas in the human gut, mostly hydrogen, nitrogen, carbon dioxide and methane. This gurgles about in a semi-liquid substrate. Vibrations in our gut generate audible sounds just like the skin of a drum does. Central-heating systems also produce gurgling noises, which are caused by trapped gases. The noises go away after “bleeding” the radiators to release them. We bleed our stomach and bowels by burping and farting. Hugh Hunt Cambridge, UK

Sunshine down under I read in New Scientist that exposure to the sun in winter at latitudes higher than about 35° results in negligible vitamin D production (9 August 2014, p 34). For many years here in Tasmania (40° south) I have been exercising naked in the sun just after midday to dose up on vitamin D. But have I been wasting my time in winter?

Lake shawls

While walking around Lake Matheson in New Zealand, I came across many of these cocoon-like structures in a field of shrubs (see photo). What exactly are these? Rhea Tan London, UK Big bug zoo

angles above a latitude of 35°, it is possible for UVB to penetrate the atmosphere. I live in Oregon (45° north) and have been measuring ultraviolet radiation for several years. During the winter months, a clear day can have as much UVB radiation as 100 microwatts per square centimetre at sea level. This is between 25 and 30 per cent of the UVB we receive in midsummer and about 20 per cent of the levels seen in the tropics. For a person with fair skin, adequate vitamin D is produced by 15 minutes of summer exposure, or an hour during midwinter. Those with

n Contrary to what many experts report, anyone exercising naked at midday during the Tasmanian winter may well be receiving enough ultraviolet radiation to “Anyone exercising naked produce adequate vitamin D. Only ultraviolet-B (UVB) radiation at midday in Tasmania may receive enough UV to make is used for the production of adequate vitamin D” vitamin D, and at low winter sun

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submitted by readers in any medium or in any format and at any time in the future. Send questions and answers to The Last Word, New Scientist, 110 High Holborn, London WC1V 6EU, UK, by email to [email protected] or visit www.newscientist.com/topic/lastword (please include a postal address in order to receive payment for answers). Unanswered questions can also be found at this URL.

more melanin in their skin need more sun exposure. However, the questioner should make sure he continues his exposure at midday because UVB levels drop off within two hours on either side of the highest sun angle. Of course, cloud cover, rain and snow all severely reduce or eliminate UVB – but then, they also make it hard to exercise naked. Stephen Johnson Eugene, Oregon, US

This week’s questions Crying foul

Babies in TV or films are frequently depicted crying. How are they made to do this? Does the director wait for the child to cry

If insects grew to large sizes because of higher oxygen levels in the past, could we selectively breed insects in an oxygen-rich environment and create a Jurassic Park of insects? Sam Scott By email, no address supplied Terracotta solder

I put a piece of damp terracotta into my brown sugar to keep it crumbly. Why does the same process make icing sugar fuse into a solid brick? Kerry Graf Florey, ACT, Australia Ocean dwellers

Has any thought been given to the idea of building cities on the sea? Surely the technologies exist to make this a realistic alternative to destroying more agricultural land, and potentially even allowing us to benefit from sea level rises. Peter Hoare Ashwicken, Norfolk, UK

Question Everything The latest book of science questions: unpredictable and entertaining. Expect the unexpected Available from booksellers and at newscientist.com/questioneverything

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