August 10–16, 2019 New Scientist

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PALAST CK FE A W BOGES EA OK REMRLY NO A BIR W ININ D G

NE W S C IE N T IS T L I V E

Accommodation package with 4-day pass

10-13 October 2019 Earlybird discount price: $825* per guest

The hassle-free premium experience. Stay close by with like-minded guests and attend an exclusive gala dinner k3 nights at 4-star Crowne Plaza Hotel just minutes from the festival

k4 day All-Access festival ticket

includes entry to all the stages, the Main Stage Hospitality Lounge and fast-track access

kGala dinner

hosted by the New Scientist editor Emily Wilson with two exclusive speakers:

Andy Smith The British Antarctic Survey Steve Haake The Advance Wellbeing Research Centre Sheffield Hallam University

kScience and History of the Docklands guided tour

Earlybird discounted price ends soon: $825* per guest If you have already bought a ticket the Earlybird price for the rest of the package is just $570

To book visit NewScientist.com/hotel Queries email [email protected] *Based on two people sharing. Single rooms are also available

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The 4-star Crowne Plaza Hotel

This week’s issue

On the cover

Coming next week

6 Sailing in space Solar sail passes first major test in orbit 14 Paternal prenatal prep Men need to plan for pregnancy too

42 Does this one microbe cause all these conditions …and does that mean we can beat them?

38 Number hunters Race for the first billion-digit prime

34 Rays of hope How solar power will overtake fossils

Chiller bees The remarkable mellowing of Puerto Rico’s killer bees 8 Supergravity 12 Hairy bee tongues 7 Liquid pipes 24 Icy exoplanets 14 How sex led to feathers 15 Hyper-fast star Vol 243 No 3242 Cover image: Kateryna Kon/Science Photo Library

News

Features

7 Replaced by robots How our new colleagues will affect us psychologically

34 Rays of hope Revolutionary new forms of solar power will help us fight climate change

News

DPA PICTURE ALLIANCE ARCHIVE / ALAMY STOCK PHOTO

13 Gaia’s future We have taken control of the planet. What now? 14 Flights of fancy Birds may have sexually attractive dinosaurs to thank for their feathers

Views 23 Comment Fertility clinics must stop unproven add-on treatments, says Clare Wilson

42 The hidden cause of disease One microbe could be behind a range of conditions

The back pages

12 Organ transplants Stem cells prevent rejection of donor tissue 51 Maker Create a garden intruder alert

Insight 52 Puzzles Cryptic crossword, a clever code and the quick quiz

24 The columnist Chanda Prescod-Weinstein on red dwarf exoplanets

53 Feedback Brexit’s moonshot and worm readers: the week in weird DANIEL HISCHER/PLAINPICTURE

26 Letters Embed data ethics into health DNA projects 28 Aperture Releasing gorillas into Gabon 30 Culture The call of the moon at a new London exhibition

38 Number hunters Inside the hunt for the world’s biggest prime numbers

18 Carbon capture It’ll take more than trees to get us to net zero

54 Almost the last word Hidden in plain sight: readers explain the phenomenon 56 The Q&A Anca Dragan on how to get robots working with humans

10 August 2019 | New Scientist | 1

Discovery Tours

NOR T HE RN S P A IN

Ancient caves, human origins

Departing: 7 days from $2,625 16 May 2020 12 September 2020

Step back more than 10,000 years to discover how our ancestors played, lived and worked. Travellers will go from torchlight tours of several historically renowned caves to admire their astonishing wall paintings, to getting lost in the beauty of northern Spain. These seven days will give you extraordinary insight into our forebears.

Highlights of this historical tour include k Private visit to the caves of Las Monedas and El Castillo to see close-up the cave paintings from up to 40,000 years ago. k Talks and walking seminars from New Scientist editorial staff including

k Tours to El Pindal, Tito Bustillo, El Buxu and La Peña caves. k Visit the beautiful cities of Bilbao and Santander plus historic towns Santillana and Oviedo. k Trips to the Guggenheim Museum

editor Emily Wilson on the May

in Bilbao and the archaeological

departure.

museum in Santander.

Following huge demand for this tour we are running two of them with only 20 spaces available per tour. We advise you to enquire early to ensure you don’t miss out. In partnership with Steppes Travel

To book call +1 516 400 4285 (UK office: Mon-Sun 9am to 5.30pm GMT) Or email [email protected]

newscientist.com/tours

ABTA No.Y0766

The leader

Infectious idea

KATERYNA KON/SCIENCE PHOTO LIBRARY

A cunning bacteria may force a rethink of our most prevalent diseases AS MANY as 35 million people worldwide have Alzheimer’s disease. The financial cost to society is immense; the emotional cost incalculable. Billions of dollars have been poured into studying the lead suspect: the formation of plaques of amyloid protein in the brain. But after decades of research, we still have no idea how to treat the disease. In January, we dropped a bombshell: evidence suggests that, instead of amyloid, the cause of Alzheimer’s could be bacterial infection. If true, the finding would explain years of failed efforts to grapple with the disease and could at last point the way to effective treatments. The shock waves don’t stop at Alzheimer’s. Bacteria have been implicated in a whole host of other major disorders, including diabetes, stroke and heart disease.

The bacteria behind gum disease could cause many “lifestyle” conditions

It may be time to radically rethink our most prevalent diseases. Many are typically blamed on unhealthy lifestyles. As a consequence, living with a chronic disorder, however common, comes with a faint shadow of shame: that you haven’t eaten, exercised or lived well enough to keep morbidity at bay. Now the gum disease-causing organism Porphyromonas gingivalis is moving up the suspect list (see page 42). As a master manipulator of our immune

system, it is a particularly tricky bacterium to treat. The key challenge for researchers is to find a way to stop the organism from wreaking havoc in our bodies through inflammation, without switching off vital defence mechanisms. However, there is much we can do while we await further evidence. Although it is possible that our lifestyles aren’t solely to blame for our most common disorders, they may currently provide our best chance of keeping Alzheimer’s and other diseases at bay. Good oral hygiene is an obvious start, but most of us probably already carry P. gingivalis to some extent. So, for many of us, our best hope is to do everything we can to reduce low-level chronic inflammation. This returns us to a familiar refrain: good diet and plenty of exercise are essential. ❚

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Editor Emily Wilson Executive editor Richard Webb Creative director Craig Mackie News News editor Penny Sarchet Editors Jacob Aron, Timothy Revell Reporters (UK) Jessica Hamzelou, Michael Le Page, Donna Lu, Adam Vaughan, Clare Wilson (US) Leah Crane, Chelsea Whyte (Aus) Alice Klein, Ruby Prosser Scully Digital Digital editor Conrad Quilty-Harper Web team Lilian Anekwe, Anne Marie Conlon, David Stock, Sam Wong Features Head of features Catherine de Lange (parental leave) and Rowan Hooper Acting head of features Tiffany O’Callaghan Editors Gilead Amit, Julia Brown, Kate Douglas, Alison George, Joshua Howgego Feature writers Daniel Cossins, Graham Lawton Culture and Community Editors Liz Else, Mike Holderness, Simon Ings Subeditors Chief subeditor Eleanor Parsons Bethan Ackerley, Tom Campbell, Chris Simms, Jon White Design Art editor Kathryn Brazier Joe Hetzel, Dave Johnston, Ryan Wills Picture desk Chief picture editor Adam Goff Kirstin Kidd Production Production manager Alan Blagrove Robin Burton, Melanie Green

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10 August 2019 | New Scientist | 3

Discovery Tours

MADAGASCAR

Wildlife of Madagascar

Departing: 13 days from $7,490 8 September 2020

This is an opportunity like no other for nature lovers – highly experienced and charismatic super-guide Charles Randrianantenaina will take you on a journey by plane, boat and authentic bush camps to explore the unique and richly diverse ecosystem of Madagascar.

Highlights of this tour include: k Daytime exploration and night walks in the Andasibe-Mantadia, Kirindy Mitea and Amber Mountain national parks plus the Ankarana special reserve. k Talks and walking seminars with experts from local conservation projects such as

k Travel on the iconic Avenue of the Baobabs and onto Tsingy Rouge. k Visit the historic town of Antananarivo and the perfumed island of Nosy Be. k Get up close to an abundance of species including lemurs, indris and fossas.

the Durrell Wildlife Conservation Trust.

No single supplements for the first two solo travellers to book. There are only 12 spaces available on this tour, so please get in touch early to ensure you don’t miss out.

To book call +1 516 400 4721 (UK office: Mon-Fri 9am to 5pm GMT) Or email [email protected]

newscientist.com/tours

In partnership with Steppes Travel

News Space voyage Solar sail successfully steered for the very first time p6

Shrinking wasps Some insects may be getting smaller due to climate change p8

Terrascope We could use Earth as a lens for a giant space telescope p10

Prenatal vitamins Folic acid may be important for both sexes p14

Hypervelocity star Alien sun spotted speeding its way out of our galaxy p15

Deforestation

Bolsonaro hits out over Amazon data

LEON NEAL/GETTY IMAGES

BRAZIL’S president Jair Bolsonaro has fired the director of the nation’s space agency INPE. Ricardo Galvao was sacked after he and his colleagues revealed that deforestation in the Amazon has increased since Bolsonaro took power in January. More than 3700 square kilometres of forest have been cut down so far this year, according to INPE, a figure which is backed up by other countries monitoring the region. But Bolsonaro claimed that the INPE numbers were a “lie” and were released to harm Brazil’s reputation. ❚ Michael Le Page

The trouble with dams A UK town has been evacuated after damage to a dam risked disaster. The likelihood of such events may be rising, reports Michael Le Page DAMS are typically built to cope with once in a century floods. But global warming is raising the odds of extreme events and therefore the chances of dams failing too. “The 1-in-100-year event is perhaps happening every five years,” says Roderick Smith at Imperial College London. “I’m absolutely convinced that it is due to climate change.” On 1 August, 1500 people from the UK town of Whaley Bridge were asked to evacuate after damage to a dam built in 1831 (pictured). Problems began when a section of the spillway slope where water drains out of the reservoir was damaged after heavy rain. The immediate danger has passed as the reservoir behind the dam has

been partly emptied into rivers by using pipes and pumps. The Whaley Bridge incident is similar to that at the Oroville dam in California in February 2017. Both are earthen dams where excess water flows over the top of the dam and down a concretelined spillway. If this concrete is damaged, the water flowing down the spillway can rapidly erode the earth underneath, leading to the entire dam wall collapsing There is a much greater chance of this happening when extreme rainfall or snow melt leads to very high water flows into already full reservoirs. A 2018 study concluded that climate change exacerbated the high water flows that led to the

erosion of the Oroville dam spillway, which resulted in the evacuation of 190,000 people and repairs costing $1.1 billion. The role that climate change may have played at Whaley Bridge isn’t yet clear. There haven’t been any serious dam collapses in the UK since the Eigiau and Coedty dams failed in 1925, killing 16 people. After that, regular inspections by qualified engineers became mandatory. Globally there have been at least 40 dam failures since 2000. The most recent was the Tiware dam breach in India on 2 July after heavy rain. At least 19 people died. The worst disaster was in 1975, when around 170,000 died after China’s Banqiao dam gave way. ❚

Chemistry

Metal tongue has a taste for whisky AN ARTIFICIAL tongue may one day help tackle the counterfeit alcohol trade. Alasdair Clark at the University of Glasgow, UK, and his colleagues built the device using two different types of metal taste buds. To use it, they pour whisky over the metals and measure how light is absorbed (Nanoscale, doi.org/c85z). This allowed them to tell apart samples of the same brand of whisky aged in different barrels with more than 99 per cent accuracy. The tongue could also differentiate whisky samples that had been aged for 12, 15 or 18 years. ❚ Staff and agency 10 August 2019 | New Scientist | 5

News Space flight

Sailing through space A solar sail has been successfully steered for the first time Leah Crane LightSail 2 took this shot as it deployed its sail in Earth orbit

THE PLANETARY SOCIETY

THE sails have been hoisted, the sunlight streamed strong and we have begun to sail through space. The LightSail 2 craft has demonstrated controlled solar sailing in orbit around Earth for the first time, but that isn’t the end of the voyage. The small craft was developed by the Planetary Society, a space advocacy group, and launched aboard a SpaceX Falcon Heavy rocket on 25 June. On 31 July, the society announced that operators had raised the spacecraft’s orbit by about 1.7 kilometres, completing its main mission of demonstrating that solar sails work and can be steered. Its predecessor, LightSail 1, launched in 2015, but only unfolded its sail – it didn’t do any controlled manoeuvring. Solar sails are propelled by sunlight bouncing off lightweight, mirrored sails. As particles of light hit the sails, these photons impart a small amount of energy that pushes the craft forward, like wind in a sail at sea. LightSail 2’s sails are a mere 4.5 micrometres thick – thinner than a human hair – and their total

“The grand dream is that light sails will eventually take us to other solar systems”

craft are set to follow LightSail 2. NASA’s Near-Earth Asteroid Scout mission is planned to launch on the first flight of the Space Launch System rocket, currently scheduled for 2021. Members of that mission have been consulting the LightSail 2 engineers to inform the development and operation of their own solar sail, which will take a craft past a nearby asteroid. The grand dream is for light sails to eventually take us to other solar systems. They don’t carry fuel and aren’t limited by how fast

surface area is 32 square metres. Each photon imparts a minuscule amount of energy to the sails, but over time the momentum adds up, causing the spacecraft, which itself is about the size of a loaf of bread, to continually accelerate. Light sails are an old idea, first dreamed up by astronomer Johannes Kepler in 1608. Other

they can shoot out exhaust like traditional propulsion systems, so light sails could, in theory, accelerate to an appreciable fraction of the speed of light to get us to another star far faster. However, that will take much more technology than LightSail 2 has demonstrated, from larger sails to giant lasers to accelerate them more efficiently than sunlight could. So far, we have taken one baby step on a long journey towards using light sails for interstellar travel, says Avi Loeb of Harvard University. He is chair of the Breakthrough Starshot project’s advisory committee, an initiative that aims to send a fleet of tiny spacecraft to our solar system’s closest star using light sails. “If I’m being realistic, it will be several decades at a minimum.” Craft like LightSail 2 could take us out among the planets, but much more work is needed before we can reach the stars. ❚

Climate change made heatwave more likely IF YOU struggled during last month’s record-smashing heatwave across Europe, there is bad news. Such events are the new normal for countries like the UK, and we can expect even more extreme ones in the next few years. Friederike Otto at the University of Oxford and her colleagues used computer models to assess how global warming has altered the likelihood of events like the July 6 | New Scientist | 10 August 2019

heatwave in Europe. During this, the UK, Germany, Belgium, Luxembourg and the Netherlands experienced all-time highs. Only the UK remained below 40°C. The researchers found that temperatures in all locations would have been 1.5°C to 3°C cooler had this event occurred in pre-industrial times. It is highly unlikely that France and the Netherlands would have seen such a heatwave at all without global warming – it would be expected to happen less than once every 1000 years. For the UK and Germany, the heatwave wasn’t quite as unlikely.

BERTRAND GUAY/AFP/GETTY IMAGES

Extreme weather With the world still warming, heatwaves such as July’s are likely to continue and to get even more extreme

It could have happened around once every 100 years in a pre-industrial climate. In today’s climate, such heatwaves are now expected around once every eight years. “Every heatwave analysed so far in Europe in recent years was found to be made much more likely and

more intense due to humaninduced climate change,” says the study, which was published by the World Weather Attribution initiative. Globally, July equalled or surpassed the hottest recorded month, according to the World Meteorological Organization and the EU’s Copernicus Climate Change Programme. The hot air that caused the European heatwave later moved over Greenland, resulting in record levels of surface melting. Meanwhile, forest fires continue to rage across Greenland, Alaska, Canada and Siberia. ❚ Michael Le Page

Automation

‘Anti-tubes’ for pumping blood are made of liquid

People prefer to lose jobs to robots over humans

Chelsea Whyte

Chelsea Whyte

FLUID travelling through tiny pipes can be damaged or slowed down by the pipe’s walls, a problem that affects some parts of the blood pumps used during heart surgery. A new type of liquid pipe that has no walls could solve this dilemma by allowing fluid to flow with nearly no friction. The pipes were made using a ferrofluid, a liquid containing suspended magnetic particles. Thomas Hermans at the University of Strasbourg in France and his colleagues placed this liquid inside a plastic case lined with magnets, which were used to manipulate the ferrofluid and create a channel where another fluid could flow. “We call them anti-tubes,” says Hermans. In one test, the group found that honey flowed 70 times faster through ferrofluidic channels than through a conventional plastic tube of the same diameter (ChemRxiv, doi.org/c85g). This could help in the study of fluid dynamics or in pharmaceutical processes that involve manipulating small amounts of liquids. By rapidly adding and removing magnets, the fluid inside the liquid tube can be forced to flow, in a similar way to the rollers used in peristaltic pumps commonly used to pump blood through a heart during surgery. “With those, the red blood cells can break and haemoglobin is released into blood plasma, which triggers all kinds of bad things for the patient,” says Hermans. In tests, Hermans and his team found that the breakdown of haemoglobin in human blood was about 11 times lower with their pipe than in a traditional peristaltic pump. Thomas Russell at the University of Massachusetts Amherst says the system may be susceptible to interference from other magnetic fields, but that future tests would have to confirm this.  ❚

IMAGINE you were about to be replaced. Would you prefer to lose your job to a robot or another person? If you said robot, you are in the majority. “Being replaced by modern technology versus being replaced by humans has different psychological consequences,” says Armin Granulo at the Technical University of Munich, Germany. He and his colleagues set out to examine these differences. The team asked 300 people to judge whether they would prefer an existing employee to be replaced by a robot or a human. In that scenario, 62 per cent of people said they would prefer to have a human step in. But when they were asked to shift their perspective and imagine losing their own job, 63 per cent would rather their own job was taken by a robot. In a follow-up, the team

REUTERS/ALY SONG

Fluid dynamics

asked 251 people to indicate the intensity of their negative emotions, such as sadness, anger or frustration, when imagining new employees being replaced by humans or robots. When the questions

63% of people would rather be replaced by a robot than a human

referred to replacing other people’s jobs with robots, the respondents said they had stronger negative emotions than when they considered losing their own job to a robot. The team found that people rated robots as less threatening to their self-identity than human replacements in a job setting. That may be because people don’t feel they can or must compete with a robot or a piece of software in the same

way as they might with another person, says Granulo. The group also surveyed 296 workers from the manufacturing industry. A third of these workers thought their current job could be replaced by technology in the near future and expressed the same pattern of preference for being replaced by robots rather than people (Nature Human Behaviour, doi.org/c85t). In 2013, Carl Frey and Michael Osborne at the University of Oxford categorised jobs by how easily they could be done by machines and found that about half the jobs in the US could be performed by robots in the next 20 years. Other studies have come up with different figures, but most researchers agree that large numbers of jobs will be automated in the near future. “Workers prefer automated plants to non-automated plants because they don’t have to do as much heavy lifting. But people mind the transitions. When something was just being introduced, they did worry about loss of responsibility, that could worry them about their jobs,” says Frey. He says that some jobs may simply shift to adapt to technological advances. For example, a bank teller 40 years ago handled more cash and dealt with transactions that an ATM may take care of today. “But those jobs still exist. Now, a bank teller is more of a relationship manager. The job disappeared, but we don’t think of it that way, because what matters to people is if they are replaced,” says Frey.  ❚ People find robots less threatening to their identity than humans 10 August 2019 | New Scientist | 7

News Interview Peter van Nieuwenhuizen

Entomology

Supergravity takes the prize

Wasps may be shrinking due to climate change

One of the discoverers of the concept that led to string theory discusses his award-winning work with Leah Crane

What is supergravity? Supergravity is a combination of general relativity with the idea of supersymmetry, which is a symmetry between the two kinds of particles we see in nature, bosons and fermions. In supersymmetry, every boson should have a partner particle that is a fermion and every fermion should have a partner boson. General relativity predicts a particle called the graviton, which is a boson, and supergravity adds another particle called the gravitino, a fermion, to be its superpartner. The gravitino has quantum properties that general relativity alone doesn’t have. Where does the idea of supergravity come from? Supergravity is an extension, but not a replacement, of Einstein’s theory of general relativity. A significant outstanding problem in physics has always been to unify quantum mechanics 8 | New Scientist | 10 August 2019

JOHN GRIFFIN/STONY BROOK UNIVERSITY COMMUNICATIONS

SUPERGRAVITY is the idea that launched a thousand theories. It suggests that the particle thought to cause gravity ought to have a partner, and from this concept came a possible way to solve some of the biggest mysteries in physics, from unifying gravity with quantum mechanics to explaining the effects of dark matter. The three people who formulated supergravity – Sergio Ferrara, Daniel Z. Freedman and Peter van Nieuwenhuizen – have now been awarded the $3 million Special Breakthrough Prize in Fundamental Physics in recognition of their work. New Scientist spoke with van Nieuwenhuizen.

Jake Buehler

and relativity. That happens in supergravity. What does supergravity have to do with string theory? String theory is an extension of supergravity in which the elementary particles aren’t points but little pieces of wire. Supergravity is the low-energy limit of string theory, so if you ever want to do experiments, you have to go back to the real world and low energy, and that’s supergravity. Nowadays, supergravity and string theory are the same thing. Are there any other problems that supergravity could solve? Some people speculate that dark matter may consist of the supersymmetric partners of the graviton, the gravitino. If gravitinos can solve this riddle of dark matter, it would be a great achievement. No one has found any supersymmetric partner particles yet. Does that bother you? My hope is that there will be another larger collider in China and also that the mass of the supersymmetric particles will be in the range that the next

Profile Peter van Nieuwenhuizen at Stony Brook University in New York is a joint winner of the Special Breakthrough Prize 2019

collider is making discoveries. If we don’t find these particles, supergravity will survive as a tool to help with other calculations in physics and mathematics, but what is more important to me is physical reality. If it isn’t a theory of physical reality, I will be very disappointed. Were you excited to find out that you had won the Special Breakthrough Prize? Do you have any plans for the prize money? When Edward Witten [chair of the selection committee] called, I was nervous that he was going to ask me a hard question about supergravity that I couldn’t answer. But instead, he said, “I am happy to inform you that you have won the Breakthrough Prize 2019.” I was speechless. I haven’t thought much about what I’m going to do with it yet. I haven’t had much time. I am 80 years old, I still work, I still teach graduate courses that I love, and that is my life.  ❚

A COMMON species of wasp appears to be becoming smaller as a consequence of the ongoing global rise in temperatures. Warming-driven shrinkage has been documented in vertebrates, such as antelopes and sparrows, but climate change’s impact on insect body size is poorly understood. Carlo Polidori at the University of Castilla-La Mancha, Spain, and his colleagues used many decades of insect samples at Madrid’s National Museum of Natural Sciences to see how they have changed over time. The team measured the body size, head width and wing size of over 200 tree wasp (Dolichovespula sylvestris) specimens from various locations on the Iberian peninsula. Some dated back to 1904. Polidori and his colleagues found that the wasps got smaller over time (Ecological Entomology, doi.org/c85c). Comparing the data with Iberian climate records, they discovered that this decline in size correlated with rising temperatures. The team can’t be sure if climate caused this change, but it is possible that hotter temperatures speed up wasps’ early development, resulting in smaller adults.

“If changes to the wing shape aren’t occurring as well, modern wasps could be less speedy in flight” “Body size shrinking is likely to have some adverse effects on recent and future insects,” says Polidori. “For example, smaller wasps may be able to hunt only smaller prey species compared with past wasps.” Oddly, the wasps’ wings are shrinking faster than the rest of their bodies. If changes to the wing shape aren’t occurring as well, Polidori suspects that modern wasps could be less agile and speedy in flight.  ❚

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Reserve your place today and view our speaker line-up newscientist.com/mindevent-boston

News Military technology

AI-guided submarines UK to use robots to find and destroy mines in the Gulf David Hambling

search more efficiently. RSTA will use artificial intelligence to take all the variables into account and generate search plans rapidly without human intervention. While current systems just record possible mines as dots, with RSTA the entire area will be mapped with high-resolution sonar. This means it will be easy to tell from a distance if an area Remus 600 underwater craft could autonomously search for mines

contains a new and potentially dangerous object. The Royal Navy is already testing robotic submarines including the Remus 600. These are torpedo-like craft that are 3 metres long and able to operate independently for up to 24 hours on battery power, locating mines with sonar. Each one can search several square kilometres a day, depending on the conditions. Once a mine is found, these submarines can destroy it using an explosive charge. Mines may

JOHN WILLIAMS/DOD OFFICE OF NAVAL RESEARCH

THE Royal Navy wants to use artificial intelligence to guide a fleet of robot submarines to find and destroy underwater mines. Mines usually lurk in shallow water until a vessel passes and triggers a sensor, setting off an explosion. Making sure waterways are safe requires regular sweeps. At present, the UK searches for mines in the Persian Gulf using crewed vessels. Tension with Iran has once more highlighted the vulnerability of shipping routes in this region. From 2020, searches there will also be made using uncrewed boats and small robot submarines. Planning minesweeping routes is difficult because there are so many interacting variables. Tides and currents, the weather, seabed contours and the number of wrecks and other metallic objects that may confuse the search all influence how long it will take to survey a given area. So, the Royal Navy and data analytics firm Envitia are developing a system called Route Survey Tasking & Analytics (RSTA) to help minehunting vessels

also be opened up and inspected. RSTA will attempt to find the most efficient minesweeping routes, bypassing difficult areas so that a clear channel can be found

“Each mine-clearing trip will be fed back into the system, allowing it to constantly improve” quickly to ensure shipping isn’t interrupted. Each mine-clearing trip will be fed back into the system, allowing it to constantly improve via machine learning. Progress in AI is making it possible to control large numbers of vehicles and quickly detect mines, says Sidharth Kaushal at London’s Royal United Services Institute, a defence think tank. RSTA should be in service by 2022. The project is part of the UK Ministry of Defence’s “humanmachine teaming” plans, in which increasing amounts of reasoning will be carried out by machines. The next application is likely to be in anti-submarine warfare, says Mark Atkinson of the Royal Navy, but it may spread to other areas. ❚

Astronomy

Earth’s atmosphere could be a giant lens for a space telescope TO TAKE better pictures of exoplanets and seek signs of life, we need to harvest as much light as possible from distant objects. Enter the terrascope. This space telescope would use Earth as a kind of lens, taking advantage of the way light changes direction as it passes through the planet’s atmosphere. “This deflection means that distant light sources behind the Earth will have 10 | New Scientist | 10 August 2019

their rays converge towards a focus point, and that’s where we place our detector,” says David Kipping at Columbia University in New York. Rays of light travelling at higher altitudes deflect less, so they would meet further away from Earth. The different meeting points create a focal line where detectors might go. The closest a detector could be is about 325,000 kilometres away. “But a better choice is at the Earth’s Hill sphere,” says Kipping. The Hill sphere is the region where Earth’s gravity, rather than the sun’s, is the dominant force, extending to around 1.5 million kilometres away.

Kipping says light rays that meet at the edge of the Hill sphere would get no closer to Earth’s surface than 14 kilometres, avoiding mountains, clouds and most of the degrading effects of the lower atmosphere. He estimates a 1-metre detector there would be akin to a 150-metre optical or infrared telescope on Earth (arxiv.org/abs/1908.00490), more than 14 times the size of the biggest optical ground telescope.

325,000 Distance in kilometres from Earth to the closest feasible terrascope detector

There are technical challenges. The terrascope would need a device called a coronagraph to block light from Earth. “Space coronagraphs are expensive and fiddly,” says Benjamin Pope at New York University. He says brief observation periods while objects pass behind Earth might also be an issue. Erika Hamden at the University of Arizona says the terrascope would also be mostly limited to detecting infrared signals and possibly part of the visible spectrum. UV imaging wouldn’t be possible because of light from the sun. ❚ Abigail Beall

Where did we come from? How did it all begin?

And where does belly-button fluff come from? Find the answers in our latest book. On sale now. Introduction by Professor Stephen Hawking

News

Learn how lab-made mini-organs could lead to more personalised medicine at New Scientist Live newscientistlive.com/mini-organs

Medicine

Rejection-free transplants We may be able to train the body not to attack a donated organ Clare Wilson

new organ being rejected. These drugs have serious side effects, such as leaving people more prone to infections and cancer. So a way to force someone’s immune system to accept a donated organ has been sought for decades. Bernhard Hering at the University of Minnesota and his colleagues exploited the way

that our immune systems learn not to attack our own cells. Throughout our lives, cells naturally die through a process called apoptosis and are shed into the bloodstream. Immune cells in the spleen take them in and “remember” that their molecules signify the body’s own cells – not invading microbes – and so should be tolerated. It is possible to mimic this process by treating cells with a chemical called ECDI that triggers apoptosis. Hering and his team induced

“Even when the antirejection drugs were stopped, the transplants stayed healthy”

AGE FOTOSTOCK/ALAMY STOCK PHOTO

PEOPLE having organ transplants in future may not have to take anti-rejection medicines, thanks to a technique that could make their immune system see the donor’s tissue as their own. The method involves giving the recipient an infusion of the donor’s cells a week before the operation, so it wouldn’t work for those getting an organ from someone who has died. But it would be suitable for those with a living donor, such as in some kidney, liver and pancreatic cell transplants. When the technique was tested on five macaque monkeys, the transplanted pancreas cells stayed healthy without being rejected for up to two years. “It’s still very early days, but if it works, it’s a complete game changer,” says Chris Callaghan at Guy’s and St Thomas’ Hospital in London, who wasn’t involved in the study. Transplants of organs such as kidneys, livers and hearts can be life saving, but recipients have to take medicines for the rest of their lives to damp down their immune system and avoid the

a condition similar to type 1 diabetes in five macaques. They then treated these monkeys with pancreatic cell transplants from donor monkeys. A week before the transplant, each sick monkey was given an infusion of ECDI-treated blood cells from a donor. They received another dose a day after the transplant, and they were also given anti-rejection drugs for three weeks. Even after these drugs were stopped, the cell transplants stayed healthy and produced insulin for two years in one animal – the point at which the study ended – and one year in the rest (Nature Communications, doi.org/c82k). The approach could eventually be used in people who receive a kidney or part of a liver from a living donor, says Hering. In the UK, about a third of kidney transplants come from such donors, who are usually relatives or friends. ❚ Recipients of donated organs have to take drugs to avoid rejection

Bees’ hairy tongues help them mop up thick or thin nectar BUMBLEBEES can gorge on gloopy nectar just as easily as they can slurp up the runny kind – and now we know why. It is all down to tiny hairs on their tongues. A close look at a bee’s tongue reveals a long, rod-like stalk that is covered in thin, hair-like protrusions. This makes it look a little like a tiny mop, which the bee dips in and out of a flower to drink sweet nectar. 12 | New Scientist | 10 August 2019

Pascal Damman at the University of Mons in Belgium and his colleagues analysed videos of buff-tailed bumblebees (Bombus terrestris audax) feeding on nectar of different viscosities, and made an unexpected discovery. They found that regardless of the fluid’s thickness, the bees lapped it up at an identical rate, collecting the same volume of liquid each time they inserted their tongue. That is a surprise because, in theory, thicker liquids should be more likely than thin ones to stick to an object dipped into the solution. The researchers 3D printed

NATURE COLLECTION/ALAMY

Zoology This bee (Perdita halictoides) has a hairy tongue that may help it to eat different types of nectar

rods that were either smooth or covered in tiny structures to mimic the bees’ hair-like protrusions. They then dipped the rods into fluids of different viscosities. It turned out that the distance between the microstructures on the rods explained the puzzle. If they

are spaced close enough to one another, then liquid is automatically pulled between them by what is called capillary action. This process is fast enough to fill all the gaps with nectar each time the bee dips its tongue in, and holds the liquid so it doesn’t drip (Soft Matter, doi.org/c82q). This means bees can cope even if the nectar’s viscosity changes. “You don’t want to starve just because your meal has gotten thinner,” says Patrick Spicer at the University of New South Wales, Australia, who wasn’t involved in the study. ❚ Ruby Prosser Scully

Conference James Lovelock Centenary

Humans at the helm of Gaia For the first time in history, Earth’s ecosystems are being shifted by a conscious species. Will they thrive or fall, asks Michael Marshall The Gaia hypothesis says that life on Earth acts to preserve its existence

NASA

EARTH is a complex machine that works to support life – and humans have seized the controls, for better or worse. That was the message of a conference held last week to celebrate the 100th birthday of James Lovelock, who famously came up with the Gaia hypothesis. Lovelock’s idea is that life on Earth acts to preserve its own existence, by stabilising conditions on the planet. Popularised in the 1970s, it inspired a generation of scientists who study Earth’s many systems, from the climate to forests, and how they interact as a whole. Lovelock is famously independent-minded, and his idea has attracted more than its share of eccentrics. This was evident throughout the conference, named The Future of Global Systems Thinking: Celebrating James Lovelock’s Centenary and held at the University of Exeter, UK. At one point, musician Peter Horton of Gaia’s Company – a group that runs workshops and cultural performances that explore the Gaia hypothesis’ themes – sang a bouncy song about how everything about us is made by and part of Gaia, from our bones to our flatulence. This silliness sat alongside a serious message. Humans are now pushing Earth’s systems out of whack, for instance by releasing more greenhouse gases than living organisms can mop up, and so heating up the planet. As a result, July may have been the world’s warmest month in recorded history. Scientists at the conference described the many impacts humans are having on the planet. For the first time in geological history, Gaia has conscious beings at the controls: a situation dubbed “Gaia 2.0” by Tim Lenton

at the University of Exeter and philosopher Bruno Latour of Sciences Po in Paris, France. The evidence that our impact on Gaia is harmful is overwhelming. Ricarda Winkelmann of the Potsdam Institute for Climate Impact Research in Germany described how the warming of the planet, caused by our greenhouse gas emissions, is melting the great ice sheets of Greenland and Antarctica. The two sheets contain enough water to raise the global sea level by 65 metres. The Greenland ice sheet in particular looks very unstable. Melting the top layer of the ice means the new top is at a lower altitude, where temperatures are warmer. “That means there can actually be a critical temperature, associated with a critical elevation, at which there is no other solution

3.8% Proportion of our carbon emissions related to plastics

but for Greenland to become ice-free,” Winkelmann said. The enormous volumes of plastic we produce and (often) immediately throw away was highlighted by Tamara Galloway of the University of Exeter. As plastic waste in the ocean has become a widespread concern, some have argued that this is “a cosmetic issue” and not a fundamental threat. However, Galloway argues that this is a mistake, because plastics are made from petrochemicals, so contribute to climate change. She highlighted a 2019 report by the Center for International Environmental Law, which found

More Gaia hypothesis online Interview: James Lovelock at 100 newscientist.com/lovelock

that the production and use of plastics will emit 0.86 billion tonnes of carbon dioxide equivalent this year. “That equates to 3.8 per cent of total carbon emissions,” said Galloway. So what would it take to repair the damage we have inflicted on Gaia’s self-regulating systems, and begin to live sustainably within them? The solution, many delegates argued, is to redesign society (and our culture) so that it is better suited to Gaia. To avoid dangerous levels of global warming, we urgently need to cut our greenhouse gas emissions. However, we have left it so late to act that many scientists are now also looking at technologies to artificially remove and store atmospheric carbon dioxide (see “Sucking carbon from air”, page 18). One such approach, developed by Tim Flannery of the Australian Museum in Sydney, is a scheme to grow seaweed in the open ocean by pumping nutrient-rich deep water to the surface. Once grown, the seaweed could be sunk, trapping huge amounts of carbon. At the conference, Flannery cited a 2012 study which estimated that covering 9 per cent of the ocean surface with seaweed would remove enough carbon dioxide to restore the atmosphere to a pre-industrial level. However, many speakers raised the spectre of unintended consequences for such geoengineering projects. For example, a huge increase in seaweed could deprive marine animals of oxygen. The fact that such ideas are being considered at all “shows how desperate people are getting”, Lenton told me. ❚ 10 August 2019 | New Scientist | 13

News Evolution

Pregnancy

How birds got their feathers Dinosaurs’ sexual preferences may have driven evolution of flight

Folic acid may help fathers-to-be have healthier babies

Colin Barras

Jessica Hamzelou

COMPLEX feathers might have originally evolved because birds’ dinosaur ancestors found them sexually attractive. Many dinosaurs had simple feathers on at least some parts of their body. Palaeontologists think they know why these first evolved. “Early dinosaur feathers really are very hair-like,” says Scott Persons at the Mace Brown Museum of Natural History in South

MANY women take a folic acid supplement when trying to get pregnant. Now, it seems men hoping to conceive may benefit from taking it too. The vitamin folate plays a role in the healthy division of cells. Women who don’t get enough in early pregnancy are more likely to have babies who have problems with their brain and spinal cord, so many are advised to take supplements of folic acid, a synthetic version of folate, before and during pregnancy. In the US and Canada, folic acid has been added to foods like bread and cereal on a mandatory basis since the 1990s. But mounting evidence suggests folate might also be important for fathers-to-be. Studies in rodents show that the amount of folate males ingest before conception influences their offspring’s health. To explore effects in people, Nerea Martín-Calvo at the University of Navarra, Spain, and her colleagues assessed 108 heterosexual couples undergoing fertility treatment at a clinic in Boston in the US and the resulting 113 pregnancies and births. Participants had to fill out a detailed food questionnaire, so that the team could estimate each person’s levels of dietary folate. After accounting for factors like age and the mother’s folate intake, the group found that men who had more folate in their diets had babies with a longer gestational period. This is generally thought to be beneficial to health (Reproductive BioMedicine Online, doi.org/10/c8zm). But it is too early to encourage men to take folic acid, says Sarah Kimmins at McGill University in Canada. We haven’t yet identified the optimum level of folate to produce the healthiest sperm and consuming too much may be detrimental, she says.  ❚

Carolina. As such, they were almost certainly for insulation, like mammals’ fur, he says. But that makes it hard to understand why some dinosaurs then developed feathers that were more structurally complex and that eventually became specialised for flight in birds. These later feathers are stiffer and don’t provide much insulation. Persons and his colleague Philip Currie at the University of Alberta, Canada, think it wasn’t natural selection but sexual selection that drove complex feather evolution. If such feathers helped dinosaurs secure more mating opportunities, there would have been a good reason to evolve and retain them, even if those complex feathers no longer provided insulation. Biologists know that sexual selection can shape feathers in dramatic ways. Most famously, many think peacocks evolved their elaborate tail feathers largely to impress peahens. Yet Persons and Currie say we have never considered the possibility that sexual selection could act as a bridge that helps link two episodes of natural selection. In their scenario, dinosaurs 14 | New Scientist | 10 August 2019

TOM BEAN/ALAMY STOCK PHOTO

“If I had to cast my bets, I reckon that wings evolved as sexually selected display structures”

like tyrannosaurs evolved simple feathers through natural selection for insulation. Sexual selection then encouraged some dinosaurs, like oviraptors, to evolve complex feathers for display. Those feathers then became sophisticated enough to allow small dinosaurs to glide. At that stage, natural selection then shaped feathers for flight (Evolution, doi.org/c82d). Persons thinks we might eventually find other situations in which sexual selection serves as a bridge between episodes of natural selection. “The implications may go beyond this example of dinosaurs and feathers,” he says. “It’s possible this process has had a similarly impactful role in the evolution of many other organisms for which we don’t have as clear a fossil record.” Sexual selection bridges might even have had a big impact on biodiversity: today, birds are

Did sexual selection shape the feathers of Archaeopteryx?

more species-rich than any other group of land animals, with about 10,000 recognised species. The idea makes sense, says Steve Brusatte at the University of Edinburgh, UK. “The more feathered dinosaur fossils that are found, the more it becomes clear that feathers and even wings did not evolve for flight,” he says. “If I had to cast my bets, I reckon that wings evolved as sexually selected display structures and then were later repurposed into aerofoils.” To nail the idea down, says Brusatte, we would need to collect more feathered dinosaur fossils. If elaborate feathers were unique to one sex, as they are in bird species like peafowl, it would provide strong evidence that their evolution really was shaped by sexual selection, he says.  ❚

Hear how fossils found in the UK tell the evolutionary story of dinosaurs at New Scientist Live newscientistlive.com/british-dinosaurs

Analysis Machine learning

DeepMind’s medical AI The technology firm’s latest algorithm can detect early signs of kidney injury, but it is too soon to tell if it will save lives, says Donna Lu

patient’s kidney function deteriorated so severely that they eventually required long-term dialysis. It is hard for doctors to anticipate kidney injury, so that level of accuracy is significant, says Eric Topol at Scripps Research in California. “If we knew a patient was going to have a kidney injury, there are many things we can do,” says Topol. These include adjusting the person’s fluid levels, monitoring blood pressure more closely and avoiding medicines that can hamper kidney function. However, the algorithm was far less accurate for all forms of AKI, correctly predicting only 56 per cent of all episodes, with a ratio of two false alerts for each correct prediction (Nature, doi.org/c82m). The AI was trained on more than 700,000 anonymised electronic health records from US military veterans, but only around 6 per cent of these were from women, meaning the AI may be more accurate at predicting the condition in men. The only way to be sure that the technology will be helpful is to test it in a clinical trial, where doctors

ARTIFICIAL intelligence trained on health records can now detect kidney injury up to two days before it occurs. In principle, an advance warning could help doctors intervene earlier to prevent irreversible damage to the kidneys, but this hasn’t yet been confirmed by rigorous tests. Nenad Tomašev at research firm DeepMind and his colleagues trained an algorithm to predict whether a person will develop acute kidney injury (AKI). This results in a drastic drop in the rate at which the kidneys filter blood and can be fatal if untreated. Using blood tests from medical records related to old hospital admissions, the AI predicted whether a kidney injury would occur within the next 48 hours. Its accuracy was determined by comparing the prediction with the actual outcome at the time - whether the records showed the person was later diagnosed with AKI. The algorithm was fairly accurate at predicting the most severe forms of AKI. It correctly predicted 90 per cent of the cases in which the

if they get things wrong. A false negative could mean a missed cancer diagnosis, for example, while a false positive may lead to unnecessary treatment. But the potential consequences are less serious for the AKI-predicting AI, says Topol. A missed prediction will eventually be picked up by a blood test and false alerts aren’t likely to have a negative impact, he says. This is because managing AKI usually involves checking fluid levels and blood pressure. At worst, it may mean temporarily withholding a drug that is toxic to the kidneys, which is unlikely to be catastrophic. But some barriers remain. With

these kinds of algorithms, it is hard to be sure what their predictions are based on. It is possible, for example, that an AI can use its knowledge of lab tests that were ordered to work out what a doctor suspects is wrong. Clinicians might be hesitant to take the advice of such an algorithm if it doesn’t provide clinical reasons for a prediction, says John Prowle at Queen Mary University of London. A further hurdle to developing such technology is that AIs need a lot of data for the initial training, which can be hard to come by. For instance, in 2016, the Royal Free National Health Service Trust in London provided 1.6 million identifiable medical records to DeepMind to test a smartphone app called Streams, which monitors people with kidney disease. The UK data watchdog, the Information Commissioner’s Office, later ruled that the agreement failed to comply with data protection law. Streams is now used by four NHS trusts in the UK. While this app doesn’t currently make use of AI, DeepMind has said it plans to add it to Streams. ❚

the supermassive black hole at the centre of our galaxy, Sagittarius A*. The supercharged star was found by the Southern Stellar Stream Spectroscopic Survey using the Anglo-Australian Telescope in New South Wales, Australia. The team behind the work thinks that the object might once have been one of a pair of stars orbiting each another. When they neared our galaxy’s central black hole, its intense gravity would have ripped them apart, flinging S5-HVS1 onto its current course (arxiv.org/ abs/1907.11725). It is usually hard to trace the origin of hypervelocity stars, but not in this case. “We can calculate quite

precisely where this star is coming from,” says Sergey Koposov at Carnegie Mellon University in Pennsylvania. “It looks like it is coming from a tiny region that includes the galactic centre.” We could learn a lot from objects like this. For example, by tracking the star’s route, we might see how it was affected by the halo of dark matter near our galaxy’s centre. S5-HVS1 is destined for a lonely end. It is on course to spend its final days sailing through intergalactic space. The researchers estimate that it will be several million light years away from our galaxy when it finally burns out and dies. ❚ Will Gater

intervene depending on the advice of the AI. So far, few algorithms have gone through such rigorous tests, but the new system may be well-suited to this step. With many medical AIs, there could be serious consequences

90% The AI’s accuracy at spotting cases of severe kidney injury

Space

WE HAVE seen a star zooming through the Milky Way so fast that it will eventually leave our galaxy. The so-called hypervelocity star, named S5-HVS1, is moving at a blistering pace of more than 1700 kilometres per second. Astronomers have spotted other stars travelling faster than this. But those were dying stars thought to have been blasted outwards by supernova explosions. S5-HVS1 seems to have been set on its way by an encounter with

BABAK TAFRESHI/SCIENCE PHOTO LIBRARY

Supercharged star charts a course for intergalactic void

The Anglo-Australian Telescope was used to spot a speeding star

10 August 2019 | New Scientist | 15

News In brief Marine biology

Turtle embryos may change sex by moving in the egg

MODOKI MASUDA/NATURE PRODUCTION/MINDEN PICTURES

TURTLE embryos seem to influence their eventual sex by shifting around within their eggs and seeking out hot or cool spots. In some turtles, cooler eggs produce males and warmer ones produce females. That is a concern, because climate change could result in one-sided sex ratios. Now work suggests that turtles may have some ability to adapt to this. “Embryos can detect temperature differentials within the egg and move to the optimum position,” says Rick Shine at Macquarie University in Australia. He and his colleagues measured the temperatures of the eggs of a type of freshwater turtle, Mauremys reevesii, in outdoor nests. The temperature was higher at one end of each egg than at the other, with a maximum difference of 4.7°C. Driving

WEARING yellow glasses while driving at night might make you think you are seeing better, but tests in a simulator have shown that drivers wearing them don’t spot pedestrians any faster than those wearing clear glasses. In reality, the yellow glasses reduce the amount of light entering the eye and thus what people can see at night, says Alex Hwang of Harvard Medical School. “It’s like wearing sunglasses during the night-time,” he says. Yellow glasses designed to reduce the glare of the headlights of oncoming vehicles have been sold since the 1950s. The idea behind them is that because blue light gets scattered more, filtering it out reduces glare. Such glasses are often advertised as improving night vision, and eye-care professionals commonly advise their use. 16 | New Scientist | 10 August 2019

Olfaction

To see how these glasses might affect the performance of drivers at night, Hwang’s team kitted out a driving simulator with highintensity LEDs that can match the brightness of vehicle headlights. Twenty-two people aged between 21 and 80 each did eight driving sessions of about 10 minutes in the simulator. They sounded the horn when they saw a pedestrian crossing the road. People wearing yellow glasses – the study used three makes sold commercially – responded a fraction of a second later than those wearing clear spectacles (JAMA Ophthalmology, doi.org/c82j). The difference wasn’t statistically significant, but Hwang thinks it would be if the study were repeated with more participants. The volunteers all thought the glasses did help, though, saying the night scenes looked brighter. That means wearing yellow glasses may make people overconfident, Hwang says. Michael Le Page

Humans are great at smelling cheese SMELL that? If it is cheesy, sweaty or sweet, you might be more likely to sense an odour. Humans have evolved a lot of smell receptors for these scents, probably to help us choose which foods to eat. Luis Saraiva at Sidra Medicine in Doha, Qatar, and his colleagues looked at smell receptors in mice and people. To do this, they analysed a patch of neurons that contain smell receptors. This area

AGE FOTOSTOCK/ALAMY STOCK PHOTO

Yellow glasses don’t improve night vision

“The temperature difference needed to shift from ‘develop as a male’ to ‘develop as a female’ is only about 1°C,” says Shine. There is enough temperature difference within an egg for an embryo to change its temperature that much. Lab tests showed that embryos that couldn’t sense temperature stayed in the middle of the egg and either all males or females hatched, depending on the incubation temperature. Those that could sense it moved up to 6 millimetres, and about half were of each sex (Current Biology, doi.org/c82g). Fredric Janzen at Iowa State University says it is unlikely that embryos move like this. The yolk would be in the way, and embryos would have to move twice a day to cope with temperature fluctuations, he says. Chelsea Whyte

is some 2.5 square centimetres in humans and sits between the eyes at the top of the nasal cavity. The team extracted mRNA from each sample. These molecules help genes to make proteins, so levels of them indicate which genes were “switched on”, as well as their relative abundance. Both species have more receptors for odours that smell like rancid milk or cheese, sulphur or sweat, or are particularly sweet or spicy-smelling, like vanilla or clove than for other smells (Science Advances, doi.org/c82n). These help us make decisions about which foods are safe to eat, says Saraiva. But in mice, the chemicals also act as pheromones that can influence their behaviour, such as scents that attract mates. We have lots of receptors for chemicals also found in bodily fluids like breast milk and vaginal fluid, but there is no evidence these act as pheromones in humans, says Saraiva. Jessica Hamzelou

New Scientist Daily Get the latest scientific discoveries in your inbox newscientist.com/sign-up Robotics

Really brief MINDEN PICTURES/ALAMY STOCK PHOTO

Stamping won’t kill this cockroach robot EVER tried to squash a pesky insect only to see it scuttle off once you raise your shoe? You may soon have the same difficulty eradicating tiny robots, because a simple machine seems to have been given the robustness of a common cockroach. “It looks really like a cockroach moving on the ground,” says Liwei Lin at the University of California, Berkeley. The prototype robots comprise

Small porpoise on brink of extinction There may be only 19 vaquitas left in the wild. Numbers of the small porpoises, found only in Mexico’s Gulf of California, have dwindled in recent years and an assessment using acoustic underwater sensors has estimated just how bad the situation now is (Royal Society Open Science, doi.org/c8zz).

An analysis of Lyme disease incidence in the UK suggests that the infection may be three times as common as previously thought. A team has estimated that there were 7700 cases of Lyme disease in 2012 in the UK. This is far more than the usual estimate of between 2000 and 3000 cases a year (BMJ Open, doi.org/c8zx).

Monkeys show their logical thinking Macaques have passed a test that shows they can use logical reasoning to solve puzzles. The finding adds to growing evidence that animals don’t just make choices purely to maximise the reward they get (Science Advances, doi.org/c8zw).

Public health

a human stepping on them. Lin says that, in experiments, a member of his team tried stamping on one device with as much force as they could muster. Although its speed was roughly halved, the bot still worked. Lin says that twisting one’s foot while stamping would probably destroy the robot, though. More work is needed to control the robots’ movement, says Tim Helps at the University of Bristol, UK. But he thinks they could soon be used in industrial contexts, perhaps for inspecting pipes or sewers. Chris Baraniuk Water purification

Slice of wood makes saltwater drinkable

BEN STANSALL/AFP/GETTY IMAGES

UK Lyme disease cases are rising

a curved rectangle and angled front leg. They are up to 3 centimetres long and weigh less than 0.07 grams. When electricity is applied, the robot body contracts and expands in quick succession. During these motions, the front leg strikes the floor and helps to propel the bot forward at speeds of up to 20 centimetres per second. The devices can carry up to six times their own weight. One successfully transported a single peanut, for example (Science Robotics, doi.org/c82p). The robots easily survive

London’s public spaces rife with drug-resistant bacteria MULTIDRUG-resistant bacteria are dotted throughout London. From swabs taken across the city, nearly half of the samples containing a common type of bacteria had a drug-resistant strain in them. Hermine Mkrtchyan at the University of East London and her colleagues swabbed commonly touched surfaces around the city, including door handles, stair handrails and taps in shopping centres and train stations, and lifts and reception areas in hospitals. They tested the swabs for the presence of staphylococci, a group of bacteria that can cause antibioticresistant infections such as MRSA.

Out of 182 swabs containing staphylococci, 40.7 per cent were resistant to more than one antibiotic. And out of 418 swabs from hospitals containing the bacteria, 49.5 per cent were multidrug-resistant (Scientific Reports, doi.org/c82h). “Finding such high levels of antibiotic-resistant bacteria in the general public settings is a worrisome finding,” says Mkrtchyan. Most of the bacteria identified aren’t usually pathogenic, but some may cause infections in people with weakened immune systems. Sam Wong

FILTERING the salt out of seawater can take a lot of energy. A thin membrane of porous wood may be able to fix that. In membrane distillation, salty water is usually pumped through a plastic film with tiny pores that filter out the salt and allow only water molecules through. “If you think of traditional water filtration, you need very high-pressure pumping to squeeze the water through, so it uses a lot of energy,” says Jason Ren at Princeton University. Ren and his colleagues have made a membrane from a thin piece of American basswood, instead. “This is more energy efficient and it doesn’t use fossil fuel-based materials like many other membranes,” he says. Chemical treatment makes the wood’s surface slippery, and one side is heated so water is vaporised as it flows over it. The vapour then travels through the pores to the colder side and leaves the salt behind, condensing as fresh water (Science Advances, doi.org/c84g). Doing this for a thin layer of water takes less energy than maintaining a high temperature to boil it all, as happens with other approaches, says Ren. Leah Crane 10 August 2019 | New Scientist | 17

News Insight Carbon capture

Sucking carbon from air To avoid dangerous global warming, we need to go carbon negative. Is mass tree planting the answer? Michael Le Page reports HUMANS have now pumped so much carbon dioxide into the atmosphere that the only way to meet our climate goals is to extract a stupendous amount of it. Last month, a headline-grabbing study suggested that we can do this just by planting a vast number of trees. But is it really that easy? We know that we need to employ some form of carbon negative technology for two reasons. First, with emissions still rising, planetary warming is on course to exceed 2°C above pre-industrial temperatures not long after 2050. If we can reduce CO2 levels, we stand a chance of cooling the planet back to safer temperatures. Second, there are some activities – farming, flying, cement production, steel-making – that are really hard to do without emitting lots of carbon. Even if the

world got serious about reducing emissions from these processes, the technology to do it doesn’t necessarily exist. Carbon removal might allow us to keep on flying, making steel and so on, and still get to zero overall emissions. Tree planting for this purpose is a beguiling idea: trees are beautiful, cheap and effective at sucking in carbon. A longerstanding idea is to grow plants, burn them to make electricity and then filter out the carbon released and somehow store it. This is known as bioenergy carbon capture and storage (BECCS). Almost all studies that claim we can limit warming to 2°C assume a massive deployment of BECCS. Yet we don’t know if it would work. No one has shown it can be done affordably on a large scale. Even if it is doable, it would require enormous swathes of land.

How much CO2 can we remove? A range of strategies could be used to suck carbon dioxide from the air. Here are the best estimates of how much they could lock away, if applied sustainably Min

Max

Biochar

This means making plants into charcoal, then digging this into the soil to store the carbon for several hundred years

Afforestation

Planting about a trillion trees, which would cover an area of land roughly the size of the US

Enhanced weathering

Taking rocks that react with CO2 and grinding them up so more of the gas is locked away more quickly

Soil carbon sequestration

Managing soil so that much of the carbon that would naturally be released stays locked away

Direct air capture

This technique separates CO2 from the other gases in the air and stores it away

BECCS

0

1

Bioenergy carbon capture and storage involves producing electricity by burning crops while capturing the carbon emitted 2

3

4

CO2 removal (gigatonnes per year) 18 | New Scientist | 10 August 2019

5 SOURCE: doi.org/c8zq

Around a tenth of all land is already used for growing crops, and another three-quarters is exploited, for instance for grazing. There isn’t space to feed a growing, meat-hungry population, build more cities, conserve wildlife, save forests and also grow crops for bioenergy on a massive scale.

“Some are exploring exotic ideas, like grinding rocks that react with CO2 and spreading them on farms” Ecologists have been saying this all along, and it is expected to be acknowledged by the UN’s Intergovernmental Panel on Climate Change in an 8 August report on land use. Is there a plan B? Ostensibly, yes. The recent tree study suggested that there is enough suitable land to plant a trillion trees, and that these would soak up two-thirds of the extra CO2 in the atmosphere (Science, doi.org/gf4mwk). Trees definitely can help. But many say the study greatly exaggerates their potential. The main reason is that half the CO2 we have pumped out has been absorbed by oceans and plants. If CO2 is removed from the air, much of this will be released. This means that even if we did plant enough trees to remove two-thirds of the extra CO2 , levels would only fall by roughly a third. What’s more, it would take up to a century for these trees to do their work. Afforestation on this scale would also harm biodiversity. For instance, it would require forests to be planted on natural grasslands. “In savannahs and grasslands that are ancient ecosystems with a unique diversity, tree planting is a process of degradation,” says ecologist Caroline Lehmann at the University of Edinburgh, UK.

We would also have to plant trees in the Arctic on land otherwise covered in sunlightreflecting snow. This would mean more of the sun’s heat being absorbed. Plus, if monocultures of trees are planted, as often happens, that will do wildlife no favours. There needs to be scrutiny around large-scale tree planting, says Lehmann. “What is it really for? Carbon removal, biodiversity or job creation? These do not always align,” she says. Fortunately, there are other ways to remove CO2 from the atmosphere. One little-known method is wetland restoration. When vegetation sinks to the bottom of still water, the carbon it contains is locked up as peat. This dries out and decomposes when marshes are drained to create farmland. “They emit phenomenal amounts of carbon,” says Pete Smith at the University of Aberdeen, UK. Simply re-wetting these lands

Working hypothesis

More Insight online Your guide to a rapidly changing world newscientist.com/insight

Sorting the week’s supernovae from the absolute zeros

Commons and Climate Change in Germany and her team estimated that soil carbon sequestration and BECCS could each remove at most 5 gigatonnes (Gt) of CO2 a year by 2050 if done on a sustainable basis. That exceeds what afforestation could achieve (see graph, left). To put this into context, global CO2 emissions are currently about 40 Gt a year. This is why some people are exploring more exotic methods, such as grinding up rocks that react with CO2 and spreading the powder on farmland – known as enhanced weathering because it speeds up this natural process. However, grinding up so much

MORRIS MACMATZEN/GETTY

would stem the loss of carbon, says Smith. Restore them, and they would start taking it up again. The downside is that the land couldn’t be used for growing food. Another approach is to manage soils so they retain more carbon. So-called soil carbon sequestration can involve a range of measures for maintaining soil’s structure, from tilling less often to growing crops with deeper roots. Then there is heating plant matter in the absence of air to make biochar, which is used to improve soils by trapping nutrients and water. It can take centuries for this charcoal to break down and release its carbon. But there is a limit to how much plant material is available for making it, and growing plants solely to make it would require more land. There are huge uncertainties about the potential of all these methods. A study last year by Sabine Fuss at the Mercator Research Institute on Global

Steel-making is one process with emissions that are very difficult to cut

rock would itself require vast amounts of energy. Others want to remove carbon dioxide directly from the air, then pump it underground or convert it into other materials, like plastics. At first sight, this plan has big advantages. “You don’t need to use large tracts of land and you don’t need lots of water,” says Ajay Gambhir at the Grantham Institute for Climate Change in the UK, who has recently studied the prospects. But no one has got it to work at anything like the required scale. If anyone did, it would still require lots of energy. This strategy makes most sense if that energy comes from renewable sources – but we don’t have plenty of that to spare. According to Fuss’s study, direct air carbon capture and storage could remove 5 Gt of CO2 a year at most by 2050 if done sustainably. Adding up her team’s estimates of the impacts of carbon negative strategies suggests that, if we used them all, we could remove between about 4 and 25 Gt of CO2 a year without damaging the environment. Yet this is still an overestimate, says Fuss, because land used for growing bioenergy crops, say, can’t be turned into forests as well. However, her study didn’t include every known carbon-removing strategy. If you hoped that carbon negative technology would allow us to carry on pumping out CO2 recklessly, these estimates are bad news. On the flip side, they show we really could achieve net zero emissions if we also cut CO2 emissions hard and fast. Just don’t think that planting trees will be enough on its own. ❚

▲

Jousting

In the biggest change to jousting since the switch from chain mail to plate armour, jousts in Cornwall will now be settled using the Hawk-Eye video refereeing system. ▲

Milky Way

Warped world view? More like a warped galaxy view. The largest ever 3D map of the Milky Way has found it is S-shaped. ▼

Greenwashing

An attempt by one factory in China to go green failed after inspectors said that painting nearby rocks to look like vegetation wasn't enough to meet its environmental duties. ▼

Maths

Divisions are spreading online about the equation 8 ÷ 2(2+2). Is the answer 16 or 1? And does it (not) really matter? ▼

DR T. J MARTIN/GETTY. PETER MACDIARMID/GETTY IMAGES

DEEPOL BY PLAINPICTURE

Planting a trillion trees isn’t quite the climate panacea it might seem

Technology

Tweets aren't what they used to be. Just 1 per cent of uses of the word now refer to birdsong. #MakeTweetsChirpsAgain

10 August 2019 | New Scientist | 19

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Views The columnist Chanda PrescodWeinstein on red dwarfs p24

Letters Embed data ethics into health DNA projects p26

Aperture Releasing gorillas into the forests of Gabon p28

Culture The call of the moon at a new London exhibition p30

Culture columnist Simon Ings on electrifying the US in the 19th century p32

Comment

Cease the IVF racket Fertility clinics must stop profiting from expensive, unproven add-on treatments, says Clare Wilson Clare Wilson is a medicine and health reporter for New Scientist. Follow her on Twitter @ClareWilsonMed

JOSIE FORD

T

HE man’s crotch, covered only by his underpants, was level with my head and twice as large as life. Luckily it was only a poster at a trade exhibition for fertility doctors I attended in Vienna. It was advertising supplements claimed to boost sperm counts. Odd, given that a recent review concluded that the evidence for the effectiveness of such pills is inconclusive. It was the first time I had been to this conference, the annual meeting of the European Society of Human Reproduction and Embryology. I was both awed and appalled by what I heard. For all the good that reproductive technologies do, for all the joy they

bring to those who otherwise may have been unwillingly childless, the whole field is also riddled with pseudoscience. Since the birth of the first IVF baby, Louise Brown, 41 years ago, more than 8 million babies have been born after being conceived this way. But many people who have IVF don’t end up with a baby in their arms. Success varies with age, but overall just one in four IVF cycles leads to pregnancy. In the UK and many other countries, couples often have to pay for IVF, as it is seen as optional rather than a life-saving medical treatment. With some able to afford just one or two attempts, there is inevitably a lot of disappointment.

To try to boost pregnancy rates, many clinics offer other options as well as the basic IVF procedure. Sometimes called “add-ons”, these usually add on to the price too. Many were developed on theory alone, without clinical trials to test they truly work. Last year, the UK regulator, the Human Fertilisation and Embryology Authority, developed a traffic light system for IVF addons, giving a red if there is no evidence of an improved chance of conceiving, amber if there is little or conflicting evidence and green if the evidence suggests they could be used routinely. Of the 11 add-ons it has reviewed, none get a green. Some of these procedures are

now belatedly going through trials. During the conference, researchers announced trial results showing that two widely used add-ons gave no benefit for most couples. One is freezing the embryos for a month or two before putting them in the uterus. The other is a technique called ICSI, which involves a sperm being injected into an egg. ICSI was developed to help couples where the man’s sperm cannot swim, but is now offered to anyone. Cycles done this way outnumber those of regular IVF by three to one. When I spoke to attendees at the conference, several agreed that things are bad. Some were insistent their clinic didn’t carry out such practices unnecessarily. Others justified offering these procedures by saying couples are asking for them. That isn’t good enough. Doctors can always refuse any treatment they feel isn’t in someone’s best interests. If there is no good evidence that a procedure boosts pregnancy rates, it shouldn’t be offered commercially. Those clinicians who are genuinely researching new procedures should carry them out only as part of trials where they are provided free of charge, as in most other areas of medicine. Anything else risks exploiting the desperate and the vulnerable. ❚ 10 August 2019 | New Scientist | 23

Views Columnist Field notes from space-time

Star spotting science Exoplanets are abundant near M dwarfs, the galaxy’s smallest stars. Infrared technology may help us learn more about these planets’ surfaces, writes Chanda Prescod-Weinstein

I

Chanda Prescod-Weinstein is an assistant professor of physics and astronomy, and a core faculty member in women’s studies at the University of New Hampshire. Her research in theoretical physics focuses on cosmology, neutron stars and particles beyond the standard model

Chanda’s week What I’m reading A lot about space ethics on the JustSpace Alliance website. What I’m watching I have been enjoying a lot of Women’s National Basketball Association and National Women’s Soccer League games.

This column appears monthly. Up next week: Graham Lawton 24 | New Scientist | 10 August 2019

M. WEISS/CFA

What I’m working on I have been balancing a project on neutrinos with work to support Native Hawaiian sovereignty.

N THE past 100 years, astrophysicists have deduced that space-time is expanding, that this expansion is accelerating, that the universe is about 14 billion years old and that there are at least 4000 planets beyond those in our solar system, called exoplanets. When I wrote my junior undergraduate thesis on exoplanet atmospheres back in 2002, all we knew was that simulations suggested we should see sodium in the atmospheres – and we did, but we saw less of it than expected. Today, our simulations are more sophisticated and we have moved beyond basic details about atmospheres to thinking through how to learn more about exoplanet surfaces. Increasingly, our research on stars has become entangled with research on exoplanets too. In particular, we have become very interested in a type of star known as a red dwarf or M dwarf. These are pretty fun because they are the coolest, smallest stars that exist on the main sequence, which comprises all of the hydrogen-burning stars (as opposed to neutron stars and white dwarfs, which are just compact collections of particles). M dwarfs are totally different from our own sun, with surface temperatures that are often about half that of our star. They also tend to be less than half the mass of the sun, and the smallest ones have masses and radii that are less than 10 per cent of the sun’s. Importantly, simulations show that Earth-sized planets with extensive oceans could be abundant around M dwarfs. For this reason, they have become subjects of intense interest, but observing them isn’t simple. They are also known as red dwarfs for a reason: unlike the sun, M dwarfs

aren’t bright in the visible parts of the spectrum. To get a really good look at them, we must use infrared, the part of the light spectrum on the red side that is just beyond the capacity of the human eye to see. Anyone who has seen action heroes in films use night-vision goggles is familiar with it. Effectively, to study M dwarfs, we must use telescopes that are fitted with technology similar to that of these goggles. In many ways, astronomy is a “wait and see” science – but thanks to advances in physics and centuries of information

“To study M dwarfs, we must use telescopes with technology similar to night-vision goggles”

gathering, we have become extremely good at doing that in an intelligent way. Now, we specifically design instruments that do targeted scans of the sky, surveying with specific objects in mind. Part of our smart searching involves building specific instruments designed to capture information about the kinds of objects we want to see. The Kepler space telescope spent nine years surveying the sky, and the information it collected was photometric in nature, meaning that it measured the brightness of the stars in different parts of the light spectrum. Scientists then

searched these measurements for signs of periodic dimming – evidence of a planet eclipsing the star. More than 2000 confirmed planets were discovered this way. Today, Kepler is retired, but the search from space goes on with NASA’s Transiting Exoplanet Survey Telescope and the European Space Agency’s Gaia observatory. The information collected by these instruments is made all the more interesting by simulation work that is under way. For example, last year Aomawa Shields and Regina Carns published a paper that looked at the presence of sodium chloride dihydrate (hydrohalite) on the surfaces of M dwarforbiting exoplanets. Hydrohalite can condense into sea ice at low temperatures. Unlike salt-free ice, this ice can be highly reflective in the infrared spectrum, which is exactly where we are already looking for M dwarfs. This presents the challenge of telling the difference between light coming directly from the star and starlight being reflected from the planet’s surface, but it also gives us an opportunity. Shields and Carns found that this reflectivity also enhanced the build-up of carbon dioxide, which is a key ingredient for planet habitability. Of course, it is unclear what it means for humanity to find habitable planets. As I mentioned in a previous column, the possibility of long-distance travel to other stars during a single human lifetime is low. At the same time, as we refine data collection mechanisms, we strengthen our ability to stumble across indicators of life in far-flung places. Perhaps, more than knowing how old space-time is, this is the kind of information that could revolutionise humanity’s relationship with the universe.  ❚

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Views Your letters

Editor’s pick Embed data ethics into health DNA projects 20 July, p 12 From Emma Martins, Office of the Data Protection Authority, Bailiwick of Guernsey Adam Vaughan explores plans for genetic testing by England’s National Health Service. Such testing has the potential to offer significant benefits to individuals and to society. But it is misguided and even dangerous to talk of anonymised data in this context. There is much discussion about how easy it is to reidentify supposedly anonymous genetic information. The concern isn’t how specifically the data may be linked to an individual; it is the fact that there is a possibility that it can be. Health secretary Matt Hancock says that individuals will be asked to give their consent to anonymous sharing of their data. But when we talk about consent, we must address the fact that it isn’t possible to unequivocally promise people that their data will remain entirely anonymous. Pretending otherwise risks further eroding the already fragile levels of trust the public has in data handling. Genetic privacy may also be compromised for those who aren’t tested. They can be identified from DNA data provided by others (20 October 2018, p 14). This long-range familial DNA research raises questions about ethics, consent and access by law enforcement and other agencies. Consent is only legitimate when it is given with full knowledge and understanding. So long as companies that profit from our data continue to do so in ways that are far from clear and anything but accountable, the public will be on the back foot. Data privacy advocates are often perceived as being opposed to progress. That is untrue: we seek a future that embeds data ethics into projects like this to ensure that progress builds on human values, rather than trampling on them. 26 | New Scientist | 10 August 2019

Lessons of the moon mission for us on Earth 13 July, p 36 From Frank Dawson, Liverpool, UK The juxtaposition of your articles on the moon landing and news of Arctic wildfires (p 14) was interesting. You imagine a moon base in 2069 producing textiles and art that command high prices back on our planet. And on Earth today, one of the feedback effects of global warming seems to be in full swing – rather sooner than had been predicted – as Arctic peatlands release carbon dioxide. By 2069, we are likely to have a lot more to preoccupy our minds than going back to the moon. The best thing we can take from the story of the first moon landing is that it seemed impossible and was immensely difficult to achieve, and yet it happened. That gives us a flicker of hope. But all those who are aware of the seriousness of the situation need to acknowledge that the future of our species, as well as that of many others being driven to extinction, will be very grim if we carry on as we are or fail to do enough.

13 July, p 42 From Paul Tavener, Waterlooville, Hampshire, UK Given all that SpaceX has done to open up the space frontier by reducing costs and developing reusable rockets, I was surprised to read that the best that could be said about SpaceX were comments about its chief executive’s use of the word “colonising”. If more rockets were reused, as SpaceX’s Falcon 9 can be, unlike NASA’s Space Launch System, that would help protect our environment. Leader, 13 July From Denis Watkins, Felindre Farchog, Pembrokeshire, UK You urge that we return to the moon “for all the right reasons” and say lunar bases will become staging posts for exploring Mars and the rest of the solar system. The “right reasons” probably won’t be a priority unless we first tackle the problem of our ancient hunter-gatherer brains. Humanity is well-practised in making Earth uninhabitable, species extinct and air and water polluted. Climate change deniers count some of the world’s most powerful political leaders among

their ranks. Is there any reason to think that we would behave differently in space?

All is not lost if we fund a hunt for helium 13 July, p 22 From Jon Gluyas, Durham, UK and Chris Ballentine, Oxford, UK Chanda Prescod-Weinstein is correct to highlight the global helium supply crisis. We should worry enormously about the paucity of helium reserves, with production for export as a by-product of natural gas limited to the US, Qatar and Algeria. Each of these has its own quirks that could limit helium production. The problem is that, until now, no one has looked for helium or even known how to look for it. Eight years ago, our team set about developing a strategy for this. With funding from Norwegian energy company Equinor, we considered not just the sources of the helium from radioactive decay, but also how it escapes and is concentrated in Earth’s crust. Four years ago, we tested our strategy in the Tanzanian section of the East African Rift, where gas seeps

Views From the archives from lakes in the Rukwa region (2 July 2016, p 7). Consistent with our geological model, the seeps contained up to 10 per cent helium with 90 per cent nitrogen. Concentrations of helium can be as low as 0.3 per cent in US gases and 0.05 per cent in Qatari gases. We have identified areas on other continents where we could start to look for helium. Government support will be needed to provide the framework for exploration and commercial investment. So far, UK agencies have been unwilling to provide this, yet the UK hosts a huge and at-risk helium industry.

Don’t repeat the climate deniers’ ice age myth 6 July, p 38 From Jon Stern, San Mateo, California, US Graham Lawton helps perpetuate a common climate denier myth by saying that in the 1970s scientists were worried that we were about to plunge into another full-blown icy spell. But a literature review finds that, even then, global warming dominated scientists’ thinking as one of the most important forces shaping climate (doi.org/bfz64r). The editor writes: It would probably have been better to say “a few scientists”.

How convection works outside of textbooks 29 June, p 34 From Keith Ross, Villembits, France Michael Brooks writes that hot liquid iron rises towards the exterior of Earth’s outer core, then cools, becomes more dense and descends. This implies, as do most textbooks, that hot stuff somehow rises spontaneously. It is gravity

pulling harder on the denser material that starts things off, with the hot material, despite being attracted to the centre of Earth by gravity, being pushed up.

Neither finding shows that seals are conscious 13 July, p 16 From Ben Haller, Ithaca, New York, US The ability of seals to recall what they have just done and repeat it on command doesn’t suggest awareness or mean they have “a degree of consciousness”. My computer can remember what it does and undo and redo those actions. But that is no reason to think it is conscious. Seals may or may not be conscious – we don’t know and finding out will be hard. You have also reported that seals show physiological changes up to 45 seconds before they dive and that this suggests their dive response is under conscious control (29 June, p 17). But a study of humans choosing between two buttons to press indicated that a neural signal can be detected up to 7 seconds before they consciously make a choice (19 April 2008, p 14). Why couldn’t the seals’ pre-dive response be unconscious too? Perhaps it would be wise to leave consciousness out of it until we find a way to measure it.

An extended chain of the most complex objects Leader, 22 June From Guy Cox, St Albans, New South Wales, Australia You say that the human brain is the most complex object in the known universe. But it is part of the human body, which is an object, and so must be the most complex. But humans are parts of societies, which could be called “objects”, and… ❚

20 years ago, New Scientist was celebrating a genetically engineered solution to hunger RICE was on the menu in our 14 August 1999 issue – specifically, the problems with the staple food crop of half the world. “Rice contains the least iron of any cereal grain. In addition, it is rich in a compound called phytate, which can prevent the uptake of up to 98 per cent of iron from other dietary sources by binding to it in the gut,” wrote our correspondent Bob Holmes. The result was widespread anaemia in ricedependent areas. “You will not find any illness worldwide which is so widely distributed,” Ingo Potrykus, a plant scientist at the Swiss Federal Institute of Technology in Zurich, told Holmes, reporting from the International Botanical Congress in St Louis, Missouri. That wasn’t the only problem. “Rice also lacks vitamin A, leading to blindness and reduced disease resistance in about 400 million children worldwide,” Holmes said. Potrykus had solutions. His team had genetically engineered rice strains to contain genes for an enzyme that destroys phytate, for an iron-storage compound called ferritin and for a protein containing the amino acid cysteine, which helps the gut absorb iron. Alongside Peter Beyer at the University of Freiburg in Germany, he had also inserted three genes promoting the production of beta-carotene, which makes vitamin A in the body. “The result,” Holmes wrote, “is ‘golden rice’ – yellow grains that contain enough beta-carotene to supply all of a person’s vitamin A needs.” The researchers had modified short-grain rice and breeders still had to cross the genes into the more common staple long-grain varieties. But, Holmes confidently predicted, “that, together with field trials of the new varieties, should take about three years”. That proved optimistic. Golden rice became a totem of resistance to genetically modified food. Why not cure deficiencies by instead ensuring that people in developing countries have a balanced diet with plenty of greens, critics such as the activist Vandana Shiva argued. Golden rice was, she wrote in 2000, “a very effective strategy for corporate takeover of rice production, using the public sector as a Trojan horse”. Environmental groups such as Greenpeace have also remained implacably opposed. It was only in 2018 that golden rice received its first approvals – ironically, in the relatively well-fed nations of Australia, New Zealand, Canada and the US. Simon Ings

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To find more from the archives, visit newscientist.com/old-scientist

10 August 2019 | New Scientist | 27

Views Aperture

28 | New Scientist | 10 August 2019

Can’t get enough of gorillas? Learn to speak gorilla with Michael Leach newscientistlive.com/gorilla

Into Africa Photographer Eric Baccega Agency naturepl.com

SAVING gorillas takes serious jetsetting these days, as two female western lowland gorillas have just discovered. In June, Kuimba (main image) and Mayombe were flown from Beauval zoo in France, where they were born, to Gabon’s Batéké Plateau National Park (top right) and released on an island (middle right). The big move was organised by Beauval and the Aspinall Foundation, a UK-based conservation charity that has reintroduced over 70 gorillas to the wild. Kuimba and Mayombe have already started exploring the island, but it will take them up to 12 months to adjust to their new climate and diet. Reintroduced gorillas are fed until they are selfsufficient (bottom right) and are tracked using camera traps. Western lowland gorillas are considered critically endangered by the International Union for Conservation of Nature. Their numbers have fallen by 60 per cent over the past 25 years, says the foundation, as a result of deforestation, Ebola and the bushmeat trade. Reintroducing gorillas to the wild isn’t simple, especially if they have been mistreated and have fractures, bullet wounds or ligature marks from being tied up, says Amos Courage, director of the foundation’s overseas projects. Then there is emotional trauma: “Gorillas are very sensitive. If they are neglected, the lights go out.” Mixing Kuimba and Mayombe with other gorillas is vital, he says. A 12-year-old male from Howletts Wildlife Park in the UK will soon join the females on the island. Once the gorillas are independent, they will be released into the rest of the national park. ❚ Bethan Ackerley 10 August 2019 | New Scientist | 29

Views Culture

The call of the moon From beautiful Japanese prints to Buzz Aldrin’s “Snoopy cap”, the UK’s biggest lunar exhibition is bound to please, writes Shaoni Bhattacharya Yearning for the moon culminated in crewed missions like Apollo 11

Exhibition

The Moon

WHEN Apollo 8 astronaut Bill Anders returned to Earth after orbiting the moon in 1968, he came back with a new perspective. The newspapers were full of the eerily beautiful colour photograph we now know as Earthrise. Taken by Anders on Christmas Eve, the image shows a fragile and lonely Earth rising above the horizon of the moon’s pocked surface. Almost as iconic was his remark at the time: “We came all this way to explore the moon, and the most important thing is that we discovered the Earth.” Perspective is key to a new exhibition, The Moon, at London’s National Maritime Museum (NMM), the biggest of its kind in the UK during the anniversary year of the first moon landing. As its lead curator Melanie Vandenbrouck says, the moon is “a mirror for humanity. When we look at the moon, we are really looking at ourselves.” She is right in a literal sense, given prevailing theories about the moon’s origins as a piece of Earth that broke off in a collision some 4.5 billion years ago. But Vandenbrouck means more than that. The landing anniversary provides the occasion, but the remit is wider, offering an aesthetic, cultural, artistic and scientific exploration of our relationship with our neighbour. Organised in four parts, ranging from the ancient to the modern and beyond, it starts aptly with a delightful image from Romantic artist and poet William Blake. In a black and white illustration, a figure stands on the first rung of 30 | New Scientist | 10 August 2019

NASA

National Maritime Museum, London, to 5 January 2020

a ladder to the moon, reaching up, with the words “I want! I want!” underneath – a yearning that runs throughout the exhibition. The first section concentrates on the historical, emotional, spiritual and practical ties with

“The moon is a great unifier. Everyone who has ever been born will live under the moon” the moon. Researching the context makes you appreciate the moon’s universality, says Louise Devoy, a senior curator at the Royal Observatory Greenwich, the NMM’s partner museum. That ubiquity is clear in many artefacts, from a Babylonian cuneiform tablet dated to 172 BC,

which recorded rituals associated with lunar eclipses, to moon masks worn by First Nations peoples of Canada. It has permeated our belief systems, says Devoy, while gods appear and disappear like the waxing of lunar phases. The Hindu moon god Chandra and China’s moon goddess Chang’e both have space missions named after them. With the advent of telescopes, our relationship with the moon started to change. The earliest surviving drawing of the moon made using a telescope is on display: Thomas Harriot’s 1609 sketch relied on a telescope with just 6× magnification. While Harriot may not be well known now, Galileo Galilei is, and his book Sidereus Nuncius (Starry Messenger) is on show. His telescope viewings caused a

sensation in 1610 when they were published with his recording of surface features: craters, valleys and hills. This contradicted the idea that the stars, the moon and planets were unchanging bodies. In everyday life, the moon was at the heart of all sorts of things, from the annual harvest to medicine, literature and art. There is a very effective “moon walk” of paintings, prints and photographs from different cultures and times. Prints from Japan and Korea of the harvest moon sit alongside small, beautiful paintings by J. M. W. Turner and John Constable. Of course, an exhibition like this must offer the full space race and Apollo 11 experience. The NMM has managed to get hold of key artefacts. There is a portrait of Neil Armstrong by Paul Calle, who had special access to the astronauts on the morning of Apollo 11’s launch. It captures Armstrong’s famous cool. There is also Buzz Aldrin’s “Snoopy cap”, or communications headset; the Apollo 11 flight plan; and the magazine that held the film used to take the iconic photo of Aldrin on the moon with Armstrong reflected in the visor of his helmet. Oh, and there are pieces of moon rock. Space enthusiasts may well get goosebumps, but this exhibition will please others too, with its thoughtful, multi-faceted exploration. As Vandenbrouck says: “The moon is a great unifier. Whenever you are on Earth, you will look at the moon – everyone who has ever been born will live under the moon.” ❚ Shaoni Bhattacharya is a consultant for New Scientist based in London, UK

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How mozzies made us From Roman sieges to the Vietnam war, mosquitoes have shaped human history more than any weapon, finds Adrian Barnett

Timothy C. Winegard Allen Lane

HOW many summers have been made excruciating by the whine of mosquitoes? Sleepless nights, frantic scratching and painful swellings – no wonder mosquito hieroglyphs were included in Egyptian curses, and Assyrians and Babylonians had devil gods associated with buzzing insects. But this is as nothing compared with the death and destruction wrought by humanity’s greatest predator, an insect that can drink three times its body weight of blood in one meal and collectively kill more people than any weapon. Five hundred people a year die from attacks by hippopotamuses, crocodiles claim a thousand, and 25,000 are killed by dogs. But mosquitoes kill hundreds of thousands annually through malaria. Collectively, mosquitoes transmit 15 diseases, including five forms of malaria, yellow fever, zika and West Nile virus, and elephantiasisproducing worms. This is despite us having the chemicals to help keep such scourges at bay. In the past, these weren't available. Of the 100 billion or so Homo sapiens who ever lived, half may have been killed by malaria. With the sheer Malthusian impact of malaria established early in The Mosquito, its author Timothy Winegard, a professor of history at Colorado Mesa University, shows how much of the human story was shaped by the mosquito. The mosquito can drink up to 5 milligrams of human blood in a single meal

Mindhunter, a gripping drama about the creation of the FBI’s criminal profiling programme, returns to Netflix (16 August) with Jonathan Groff and Holt McCallany as pioneering detectives fronting the Behavioral Sciences Unit.

Visit

Below the Blanket at the Royal Botanic Garden Edinburgh is filling summer evenings (until 25 August) with visual, sonic and kinetic installations inspired by the extraordinary blanket bog ecosystem in northern Scotland.

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

Listen

Breaking Convention 2019 brings psychedelic research to the University of Greenwich, UK, from 16 to 18 August with a full programme of events. Tune in to the conference and you won't want to drop out.

10 August 2019 | New Scientist | 31

NETFLIX; NEIL JARVIE; JONATHAN GREET

The Mosquito: A human history of our deadliest predator

Watch

unavailability of some American football players for games at Denver Broncos’s stadium? (Spoiler alert, sickle-cell anaemia is involved.) There is no end of fascinating details: elephants wrinkle their skin to crush mosquitoes; young reindeer get bitten 9000 times a minute in peak season; and the word “abracadabra” was used by early Christians on anti-malarial amulets. It is all written with great brio, allowing readers to relish the connections between the collapse of societies, the failure of grand invasion plans and the rise and demise of insecticide DDT, while keeping the sheer destructive power of the tiny creature in mind. Winegard’s final chapters deal with the likely responses of Aedes and Anopheles mosquitoes to the changing climate. To animals that began by parasitising dinosaurs and then jumped to birds and mammals, the warmer future looks rosy indeed. ❚

PERNSANITFOTO/GETTY

Book

Forget generals and armies, politicians and plots – in much of the world, at some time or other, people were just too enervated by the fevers of malaria to make history. The list of malaria's military victories is long, from centuries of defeating attacks on Rome to the faltering of Kublai Khan’s invasion of the Khmer civilisation, through the Crusades and the glacial progress of British Imperial forces in Southern Africa, to more recent conflicts such as the Vietnam war. Then there are historical figures whose careers were brought to a febrile close. Tutankhamun, Alexander the Great and Ghengis Khan are among the famous dead that Winegard documents, along with an unsung 95 million indigenous people in Central and South America who died after European colonists brought malarial mosquitoes with them. The historical reach of malaria is with us still and makes for some strange connections. For example, what is the link between the domestication of the yam some 8000 years ago and the annual

Views Culture The film column

Looking for another charge The Current War is an epic tale of the fight between Thomas Edison and George Westinghouse to electrify late 19th-century America. But the real story of electricity and invention is far more gripping, says Simon Ings

Simon Ings is a novelist and science writer and a culture editor at New Scientist. Follow him on Instagram at @simon_ings

Film

The Current War Directed by Alfonso Gomez-Rejon

Simon also recommends... Film The Prestige Directed by Christopher Nolan

Based on a story by Christopher Priest, this is another fine example of an imaginative intellectual recreation of the fin de siècle’s ferment around energy and transmission. Forbidden Planet Directed by Fred M. Wilcox

A delirious interstellar fantasy about energy and the imagination.

32 | New Scientist | 10 August 2019

D ROGERS/THE WEINSTEIN CO/KOBAL/SHUTTERSTOCK

Thomas Edison (Benedict Cumberbatch) with his son Dash

LET’S begin by being boorish. Thomas Edison didn’t invent the light bulb. German-born precision mechanic Heinrich Göbel demonstrated a prototype in 1854. Joseph Wilson Swan filed a patent for a light bulb in 1879, which Edison promptly purchased. And so on: you can play this game with most inventions. The correct response to such nitpicking is given by Edison himself (inventor of the phonograph and motion pictures; holder of 2332 patents) in the movie The Current War, which lays out the battle between Edison and George Westinghouse to bring electric light to late 19th-century America. Salt. Fat. Flour. Water. Edison explains that it is only when you put all the ingredients together, in the right proportions, using the right method, that you get bread that people will buy. Priority – being first to file a patent – isn’t won by dreaming alone. Edison (Benedict Cumberbatch) teaches this hard lesson to his secretary Samuel Insull, an entertainingly exasperated Tom Holland. Originally planned for release

back in November 2017 by the Weinstein Company, the film was quietly shelved as allegations about Harvey Weinstein spread. It doesn’t feel like an old movie, but it does feel like an odd one. Big, bold, none-too-subtle speeches by the scriptwriter and playwright Michael Mitnick are directed by

“Edison executes dogs, sheep and horses with AC to prove his point about Westinghouse’s ‘lethal tech’” Alfonso Gomez-Rejon as though they were set pieces by Martin Scorsese, for whom he once worked as a personal assistant. Inventor George Westinghouse (Michael Shannon in a sensitive, understated performance that rather puts Cumberbatch’s shtick to shame) has developed a system of electrification using alternating current. For cost and efficiency, it has Edison’s direct current beat. Westinghouse offers a partnership, but Edison behaves like a cad, disparaging Westinghouse’s

“lethal” tech, and executes dogs, sheep and horses with AC to prove his point. Ironies pile up as Edison edges inevitably towards designing, against his moral judgement, the first electric chair. The real “war of the currents” isn’t done. DC lost at that time because long-distance transmission required high voltages, while the public needed safer, lower voltages. That took transformers, available for AC but not for DC. For transmitting a lot of electricity over long distances, high-voltage direct current (HVDC) is far more efficient than conventional AC. The length and capacity of HVDC has risen fast; calculations suggest continentwide HVDC “supergrids” may smooth out the variable power created by renewables. In 2009, a study by German researcher Gregor Czisch proposed a supergrid to link some European countries, and bordering regions, at a cost that virtually guarantees cheap, green electricity for all. No one has heard of Czisch, even though his work may save us from global warming. It was ever thus: we remember Nikola Tesla (The Current War’s peculiar third wheel, an AC pioneer and inventor of fluorescent lighting) only because David Bowie played him in Christopher Nolan’s magical puzzler The Prestige. Priority is a twisty business, and fame is twistier. Westinghouse so despised the whole business that he burned his papers. “If you want to be remembered,” he says, “it’s simple: shoot a president. But if you prefer to have what I call a legacy, you leave the world a better place than you found it.” ❚

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Features

Rays of hope

MICHAEL FRIBERG

The arrival of revolutionary new forms of solar power will be a major factor in the fight against climate change, says Tom Chivers

34 | New Scientist | 10 August 2019

“Solar power will overtake fossil fuels as the world’s preferred form of electricity”

“

W

HEN I was a student in the mid1980s,” says Harry Atwater, “there were only a few megawatts of solar deployed worldwide. Enough to power a supermarket or something. Now, solar technology has a global output of about 500 gigawatts.” That is enough to provide Manhattan with all the electricity it needs about 50 times over. And solar power is only just getting going. Atwater, who is director of the Joint Center for Artificial Photosynthesis at the California Institute of Technology, has been working on photovoltaic technology for his entire career. He has seen it grow from a novelty found in only a few labs into a giant industry bigger than the flat-screen TV market. Some $131 billion was invested in solar in 2018 alone. But Atwater reckons the advances set to arrive in the next few years could leave that progress in the shade. Solar power has become so cheap that before long, it will overtake fossil fuels as the world’s preferred source of electricity. And a lot of lowcost solar power will be crucial if we are to have any chance of limiting global warming to 1.5°C. “It’s an incredibly exciting time,” says Jenny Chase, an analyst with Bloomberg NEF, which looks at the costs of clean energy. “I’ve been astonished by the progress solar has made.” Financial company Lazard releases an annual report into the “levelised” cost of different energy sources – that is, the cost once you take into account the whole life cycle of a power plant, including manufacture and disposal, and disregard government subsidies. Its 2018 report showed that large-scale solar power and onshore wind were, on average, the cheapest forms of energy. Sometimes, gas could be

Ivanpah in California is one of the world’s largest solar sites

cheaper, but more often it wasn’t. Lazard found that between 2017 and 2018, the cost of solar energy fell from around $50 per megawatthour to around $43, a drop of 14 per cent in a single year. Since 1976, its cost has plummeted by about 99.9 per cent. This has led to remarkable growth in its use. “I’ve been an analyst for 13 years,” says Chase. “When I started, I thought that solar could only ever be at most 1 per cent of global electricity generation. In 2018, it was around 2.3 per cent. In China, it’s 2.5 per cent, which doesn’t sound like a lot, but China uses a lot of electricity. And in places like California, they already have 8 per cent from solar.” Last year, a Bloomberg NEF report estimated that the cost of photovoltaic cells will fall by a further two-thirds by 2050, at which time photovoltaic solar will make up 24 per cent of global energy generation. It is astonishing progress – and it can’t come too fast, with soaring carbon emissions heating the world to temperatures not seen for 125,000 years. Solar energy, through the venerable but reliable technology of silicon photovoltaic cells, will be a major part of efforts to avoid the worst of climate change. So too will new technologies that we can expect in coming years and decades. First will be improvements to photovoltaic technologies, followed by changes in the storage of solar energy that could start to have an impact within the next decade or two. Finally, we may see much more speculative, long-term ideas, such as harvesting sunlight from space and beaming it down to Earth, come to fruition. These latter developments could revolutionise the energy economy. The near-term technologies rely on new forms of solar panel. At the moment, most photovoltaic cells are built from silicon. The first practical photovoltaic cell, made by Bell Labs in 1954, turned just 6 per cent of the

solar energy that struck it into usable electricity. By 1959, a rival firm had achieved 10 per cent. A quarter of a century later, in 1985, an Australian team reached 20 per cent efficiency. And in 2016, a group at the University of New South Wales achieved almost 35 per cent, the current world record. Most commercially available solar cells peak at about 20 per cent efficiency.

Power up But silicon, although widely available, is hard to work with. “Silicon cells are made by taking sand, heating it up to thousands of degrees, and reducing it from silicon oxide to pure silicon,” says Lance Wheeler, a materials scientist at the National Renewable Energy Laboratory (NREL) in Colorado. “It’s energyintensive and a very sensitive process – you have to do it in perfect conditions.” That means it is prohibitively expensive to produce in the West. Most photovoltaic cells are built in China, backed by large amounts of government subsidy and where lower-wage skilled labour also helps the economics. Manufacturing costs have fallen as the industry has grown, but there is a limit to the energy savings possible. In recent years, however, a new form of photovoltaic cell has become increasingly attractive. Instead of silicon, this type uses various kinds of minerals called perovskites. The first perovskite cell was developed in 2009. It had an unpromising efficiency of 3.8 per cent, lower than that of the first silicon cell in 1954. But whereas it took silicon cells 30 years to get to 20 per cent efficiency even in the lab, perovskite-based photovoltaic cells took less than 10, reaching over 23 per cent last year. “They’re still something like 2 to 4 per cent less efficient than [regular] solar,” says Wheeler. “But it’s gone from mediocre to fantastic in a decade.” > 10 August 2019 | New Scientist | 35

Orbiting power plants At New Scientist, writers are steered away from comparing new developments to science fiction because this can become a prop that is reached for too readily. But here, we can’t avoid it. Harry Atwater at the California Institute of Technology is working on a project that is literally the stuff of science fiction: space solar. “This is an idea that was first floated in 1941 in an Isaac Asimov short story,” says Richard Madonna, a consultant on the project. “He envisaged sending sunlight from space to Earth via electromagnetic energy.” In the 1960s, scientists started to look seriously at the idea. But launching things into space was expensive and the components – solar panels, solar reflectors and radio transmitters – were all heavy, bulky and inflexible. So it was economically infeasible. But the Caltech group, including Atwater and a colleague called Sergio Pellegrino, recently revisited the idea. The resulting plan was for carbon booms that could be wrapped up and would spring back into shape to provide structure, as well as flexible perovskite photovoltaic cells that would be just a micrometre thick. “The whole thing could be rolled into a cylinder for launch,” says

More importantly, perovskite is just as abundant and cheap as silicon, and much easier to work with. “You can start with a jar of liquid and print it, with any kind of printing press you can think of, at room temperature,” says Wheeler. He mentions one company that has bought an old Kodak factory in New York and repurposed its printers to deposit thin layers of perovskite onto plastic film for use in photovoltaic cells. “An old newspaper printing press could be retrofitted too,” says Wheeler. There is a problem, though. Silicon photovoltaic cells are incredibly durable. If you install some on your roof, you can confidently bet that they will work for 25 years. Until recently, perovskite cells were only stable for a few hours. But NREL now has cells in its lab that work at 90 per cent of their starting efficiency for 250 days. “It turns out that perovskite is not inherently unstable,” says Wheeler. “It’s the materials next to it that have been the problem. If you can engineer them, you get good stability.” Chase warns against premature excitement. “There’s no commercial product yet,” she says. But she says that longer term, perovskite could be an interesting possibility. She and Wheeler both have hopes for hybrid cells, with a layer of perovskite sitting under one made of silicon, because they absorb different wavelengths and so would push efficiency even higher. Another fundamental problem with solar energy is that the sun doesn’t shine over an area all the time. You get more sun at noon than at midnight and at higher latitudes you get more in midsummer than in midwinter. But you need energy all day and all year. So other researchers are working to harness the sun’s energy in a more storable way.

Madonna. He envisages 60-square metre structures that would be linked to form a superstructure in orbit. SpaceX’s Falcon Heavy rocket, “which is now becoming a feasible space vehicle”, could carry about 10 of them in a launch, says Madonna. Instead of having a single, central radio transmitter, which would have needed lots of copper wire to transport the electricity, each cell would act as its own transmitter, beaming radio frequency energy down to Earth out of the side facing away from the sun. Diffraction effects mean that the larger the structure, the more tightly focused the beam could be, and the more efficient the transmission. These structures would have to be large. “It depends on how efficient it is,” says Madonna. “But to power a city, it would have to be kilometres across.” This technology isn’t imminent. The Caltech group hopes to have a small-scale test in low orbit in the next 10 years, but it could be decades before it is really possible, if it happens at all. Madonna says it won’t be like nuclear fusion though: always the next big thing but never quite arriving. “It’ll either happen or it won’t,” he says. “It won’t be 20 years away for the next 50 years.”

The storage problem

JAXA

An orbiting array could one day beam electricity to Earth 36 | New Scientist | 10 August 2019

“In the coming world of sustainable energy – with high levels of electrification – we’re going to have a serious storage issue,” says Atwater. “Batteries will be part of the solution, but imagine you’re in Norway or Sweden where they have 10 times as much sun in summer as winter. You won’t be able to store energy for six months in a battery.” He contrasts this with fossil fuels, which have stored solar energy for millions of years. “We use them every day because they’re amazingly energy-dense, storing them is inexpensive and they’re portable. Chemicals represent the ultimate form of energy storage,” he says The goal is to use sunlight to create chemical fuels. Atwater’s lab is working on artificial photosynthesis: harnessing the sun’s energy to

JAMEY STILLINGS

“Artificial photosynthesis will allow solar energy to be stored through the winter”

Solar has become a priority in Japan

turn inert chemicals into energy-filled ones. The most basic version of this splits water to produce hydrogen. A photovoltaic cell creates a current that passes through water via a positively charged anode and a negative cathode. Oxygen ions gather at the anode and hydrogen ions at the cathode. “A lab prototype here reported a world record of 19.3 per cent efficiency,” says Atwater: that is, nearly 20 per cent of the solar energy hitting the photovoltaic cell was stored in usable hydrogen fuel. “It’s an expensive device, but it’s a demonstration of what’s possible.” It is relatively easy to make hydrogen from water. “We did it as high school students with a copper wire and a platinum wire,” says Atwater. “Your feedstock is inexpensive.” One complication is that pure water is needed to avoid the cathode becoming fouled by impurities, but it is straightforward to produce very pure hydrogen that can be used in fuel cells. A bigger hurdle is making hydrocarbon fuels from atmospheric carbon dioxide, says Atwater. “It’s more difficult for fundamental reasons. The chemistry of carbon is very rich: diamond, graphite, polymers, methane – all are based on carbon.” Carbon dioxide can be turned into many different forms, he says. “The challenge is designing a process where if you want to make one thing, you get exclusively that. If you want to make ethanol, you don’t want to end up with carbon monoxide.” But although it is harder, it has two advantages over watersplitting: it strips a greenhouse gas from the atmosphere and, alongside the fuel, it results in forms of carbon that can be used to make

many complex molecules, including plastics. At the moment, Atwater’s lab is able to turn atmospheric CO2 into a combination of about 70 per cent ethanol, a fuel, and ethene, the basis for many plastics. The other 30 per cent is mainly hydrogen, which is itself useful. It is a far less efficient process than water-splitting, but progress is being made.

Copying nature The difficulty is that artificial photosynthesis relies on catalysts, but existing ones rely on external energy and are often toxic. So some other groups are looking to nature for alternatives. Erwin Reisner and his team at the University of Cambridge have made progress with “semi-artificial” photosynthesis, using natural enzymes as the catalysts. These proteins are much more effective catalysts and are better at creating precisely the products you want with no extra energy push. The downside is that they break down in a few hours or days. “In organisms, they are constantly repaired and replaced,” says Reisner. He has two hopes: that this semi-artificial technology can be harnessed to improve fully artificial catalysts or, further in the future, that bioengineered algae could create the required hydrocarbons, using natural enzymes that they repair in the traditional way. Artificial photosynthesis will allow solar energy to be stored through the winter and make it easier to power systems that are hard to electrify, such as heavy vehicles and air transport, says Atwater. And although the technology is still new, he believes it could improve rapidly. When talking to his grad students, he tells them about the photovoltaic sector when he started out. “Now it’s a

mature, fully integrated industry,” he says. “I think artificial photosynthesis is at the same stage the photovoltaic industry was at when I was a student.” As well as artificial photosynthesis, scientists at Chalmers University of Technology in Sweden are working on a liquid that traps solar energy and releases it as heat. It can already store energy about as effectively, in terms of joules per kilogram, as a lithium-ion battery, and for months at a time. It is less efficient than a solar panel, but team leader Kasper Moth-Poulsen is hopeful it will improve. “For it to absorb energy, all you need do is put it in the sun,” he says. Then, when you need to release the heat, you just add a catalyst. An efficient solar heating system that works all year round could have a huge impact on emissions. With luck, commercial artificial photosynthesis and solar liquids could be with us in a couple of decades. Beyond that, Atwater is imagining the ultimate form of energy from the sun: space-based solar panels (see “Orbiting power plants”, left). As exciting as such developments could be, on its own, solar won’t be enough. “We need to be more efficient,” says Chase. “We need to use more public transport, more cycling.” Still, though, the growth of solar is a reason for cautious optimism. “The progress has made me start to think that we can maintain some sort of developed-world lifestyle using solar,” she says.   ❚

Tom Chivers (@TomChivers) is a science journalist based in London. His book The AI Does Not Hate You is out now 10 August 2019 | New Scientist | 37

CORY BRICKLY

Features

38 | New Scientist | 10 August 2019

The call of the primes Across the planet, a handful of number hunters have an extraordinary goal: to find the biggest primes. Daniel Cossins meets them

J

ON PACE had spent 14 years searching for a monster. A finance manager at FedEx in Memphis, Tennessee, he was more comfortable trawling through spreadsheets than hunting exotic beasts. He also happened to be one of the least well-equipped in the game, so he knew the odds were stacked against him. “I probably had a better chance of being struck by lightning,” he says. But on 26 December 2017, Pace finally laid eyes on the object of his desire: the largest prime number then known, running to a whopping 23 million digits. It was so long that, printed out in two-point font, it could have easily filled a book. In some ways, he needn’t have bothered. His discovery has virtually no practical value. So what has inspired Pace and hundreds of others to devote themselves to the Great Internet Mersenne Prime Search (GIMPS), in which people scour the furthest reaches of the number line in search of enormous primes? There is no one single answer. Not all the volunteers are numberphiles. Some get into it for the prize money offered for innovations in computing: $150,000 for the first 100-million digit prime. Others join the hunt to put their latest souped-up computer through its paces. For the most devoted, though, it is above all about the thrill of discovering something rare and beautiful, something nobody has ever seen before. Primes, for those in need of a quick primer, are the numbers greater than 1 that are

divisible only by 1 and themselves. The sequence begins 2, 3, 5, 7, 11, 13, 17 and goes on infinitely, as ancient Greek mathematician Euclid showed in a beautiful proof in around 300 BC. They are cherished as the fundamental building blocks from which all numbers are made, because any number that isn’t prime can be made by multiplying primes together. What Pace found is not just any prime. It is in a special class known as the Mersenne primes, named after Marin Mersenne, a 17th-century French friar. Mersenne numbers are 1 less than a power of 2. They can be written in the form of 2n-1, which means the number is equal to

HOW TO BECOME A NUMBER HUNTER To join the hunt for Mersenne primes, go to mersenne.org and set up an account. There, you can download a program called Prime95. It has versions for most types of computer. Once installed, it will run in the background, using any spare processing power. You won’t notice it. If your computer finds anything, you will get an email letting you know — and asking you to keep it under your hat until it is publicly announced.

n 2s multiplied together (where n can be any whole number), minus 1. Mersenne primes are Mersenne numbers that are also prime. So, for example, the number 3 is a Mersenne prime because it is 1 less than 22, which is 4. Seven is another because it is 1 less than 23. The next few are 31, 127, 8191 and 131071, but they quickly get much rarer. We had found only 49 Mersenne primes before Pace snared the 50th, most succinctly written as 277232917-1. People call it M77232917 for short. “When I first found out, I thought it was a joke,” says Pace. The computer that discovered it isn’t a powerful one. Pace built it himself for his local church, primarily for word processing, using a mid-market processor. But once the discovery was announced, even Pace’s children were impressed. “At first my kids were like ‘OK, dad’,” says Pace. “But when my son found out National Public Radio wanted to interview me, he suddenly thought it was cool.” Part of the reason Mersenne primes are considered sufficiently beguiling to pique media interest is that they are closely related to perfect numbers: those numbers that are equal to the sum of all the positive numbers you can multiply together to produce them (excluding the number itself). The number 6, for example, is a perfect number because it is a product of 1 × 6 and 2 × 3, and 1 + 2 + 3 = 6. So is 28, because 1 + 2 + 4 + 7 + 14 = 28. Because every even perfect number can be generated from a Mersenne prime, the two sets of numbers are intimately connected. > 10 August 2019 | New Scientist | 39

We’re all mathematicians Bobby Seagull explains everyday maths at New Scientist Live newscientistlive.com/maths

M77232917 is only the 50th Mersenne prime ever found

SPL

There is also prize money at stake. Pace received $3000 for his discovery, which he gave to his church. But future prime hunters could earn a lot more. The Electronic Frontier Foundation, a technology-focused non-profit, is behind the $150,000 prize for anyone who discovers a prime with at least 100 million digits. It has also pledged $250,000 for a prime with over a billion digits. The main reason Mersenne primes are attractive, however, is that they tend to be the largest primes we can find. That is because there is a particularly efficient way to test if a Mersenne number is prime. It was devised by French mathematician Édouard Lucas, who in 1857, at the age of 15, used it to test whether the Mersenne number 2127-1 was prime. If you have a number like 7, the obvious way to check if it is prime is to look at whether it can be divided by the numbers below it. With huge numbers, however, that is a ridiculously laborious process. Lucas flipped it on its head. He identified a sequence of numbers with a remarkable property: if a Mersenne number can divide into another, larger number in that sequence, then the Mersenne is prime. This means you have one long calculation to make, instead of lots and lots of them. Even so, the task was far from trivial. Lucas pulled it off by representing the Mersenne number in binary form on a 127 by 127 chessboard, with pawns for the 1s and empty squares for the 0s. By moving the pawns

around, he could painstakingly carry out the division. It took him 19 years, presumably not full time. But eventually, Lucas had his result: M127 is indeed prime. No one ever reproduced Lucas’s efforts. Indeed, he himself only performed the entire operation once. But US mathematician Derrick Henry Lehmer refined the method in the 1930s to create the Lucas-Lehmer test. It remains the simplest way to test if a Mersenne number is prime, and it formed the basis of the algorithms that brought the search for primes into the computer age. As

CONSTANT CRAVINGS In November 2016, after 105 days of furious computation, Peter Trueb’s machine spat out a gigantic number. It was pi, the famous mathematical constant that roughly equals 3.14, but here it had been calculated to record-breaking precision: some 22.4 trillion digits after the decimal point. A software developer in Zurich, Switzerland, Trueb is one of hundreds of people across the world who use a freely available computer program called y-cruncher to find record numbers of digits for

40 | New Scientist | 10 August 2019

various mathematical constants, from pi and Euler’s number to the golden ratio. This form of number exploration relies heavily on computer power. Trueb, a lifelong pi enthusiast who is also interested in the philosophy of numbers, used his company’s resources to build a computer with 24 hard drives. Each contained 6 terabytes of memory, to store the whopping quantity of data generated by the calculations. He was always likely to be outgunned eventually,

however. Sure enough, his record was smashed this year by a Google developer from Japan, Emma Haruka Iwao, who used the tech giant’s cloud computing services to calculate pi to 31.4 trillion digits. There is more serendipity involved in other forms of number exploration. Rather than pinning down the digits of a special number to extreme precision, these involve interrogating figures lurking in the furthest reaches of the number line to find those that are the rarest and most beautiful (see main story).

computers grew faster and more powerful, the primes we discovered grew longer (see “Prime targets”, right). It wasn’t until George Woltman launched the collaborative GIMPS project in 1996 that the general public could get involved. A programmer and prime lover, Woltman wanted everyone to have a chance at discovering giant primes. He rendered the algorithm so fast and efficient that it can run in the background on any relatively modern household computer with an internet connection. Then he worked with others to automate the selection and allocation of numbers to test, and the checking and reporting of results. The fruit of this is a program so easy to use that hundreds of people have signed up for a stab at finding a record-breaking prime (see “How to become a number hunter”, page 39). “From the 1950s through to ’96, you had to own a supercomputer to have a chance to play the game,” says Woltman. “Not anymore.” The only thing you need, beyond a computer, is patience. The software will run on most machines, but on a typical home computer it takes roughly 14 days to test a potential Mersenne prime.

Number crunchers Among the first to sign up to GIMPS was Curtis Cooper, a mathematician at the University of Central Missouri, who has been fascinated by primes since childhood. He wasn’t messing about. While many volunteers donate the spare processing power of their own computer, as the administrator for a whole campus, Cooper was able to recruit some 600 machines. That gave him a better chance than most. Sure

Prime targets Very small prime numbers have been known since antiquity, but as computing has developed we have found much larger ones

2018 Patrick Laroche discovered the longest prime number, which has

107

24,862,048 digits 1996

106

The Great Internet Mersenne Prime Search was launched. Most of the largest primes known today are Mersenne primes

105

1951

104

At the dawn of the computer age, much larger primes began to be identified

103

18th century Leonhard Euler found several new primes

102

1588

101

The Italian mathematician Pietro Cataldi discovered that the number

524,287 was prime.

It would remain the largest known prime for nearly two centuries

Length in digits (log scale)

enough, in 2005, after eight years of number crunching, Cooper’s army of machines discovered the 43rd Mersenne prime. Cooper has since found another three of them, the latest confirmed in 2016. The last of these had been calculated in 2013, but the automated system used by GIMPs to alert its volunteers failed so the discovery only came to light three years later, when the server’s administrator came across it during routine maintenance. “It was almost the lost prime,” says Cooper. For him, each discovery is a moment to savour his place in the long tradition of prime hunters, from Euclid and Euler through to Lucas, whom he regards as an idol. “The fact that we do it on computers rather than by hand, as Lucas did, does sort of take the romance out of it,” he says. “But I figure there is a romance in the fact that pretty much anybody can do this now.” Pace, who took the record for the largest prime from Cooper in 2018, echoes the sentiment. “I don’t have a huge amount of computing power,” he says. “Most of the computers I’ve volunteered are just ordinary desktop PCs. My mother is running this program on hers. She has no idea.” It seems a good way to use otherwise wasted computing power. Considering that RSA encryption – one of the standard ways to keep your data safe online – requires your bank to come up with two big primes and multiply them together, finding new numbers for this might appear useful. Especially because it is the difficulty of factoring the resulting product that keeps hackers at bay. But the primes we already know are plenty big enough for the job, so the ones GIMPS is finding aren’t needed. You might also think that identifying new, giant Mersenne primes could help us solve some perplexing mathematical riddles. But here too, a new prime is no help. It won’t weigh in on the twin primes conjecture, for example, which ventures that there are an infinite number of primes separated by 2, like 11 and 13. Nor will it prove the most famous conjecture associated with Mersenne primes, namely that there are infinitely many of them too. “It doesn’t answer the question ‘but is there another, even larger, Mersenne prime?’,” says Vicky Neale, a mathematician at the University of Oxford. In maths, proof comes not from observations but self-contained explanations based on mathematical logic, like the one Euclid devised for infinite primes. GIMPS has thrown up one curiosity, though. The formula used to work out the distribution

1600

1700

1800 Year

1900

2000

100

SOURCE: PRIMES.UTM.EDU

of primes along the number line predicted that there would be just three between 220,000,000 and 285,000,00. But GIMPS has turned up 12. “Theoretically, life can be different the further out you go,” says Chris Caldwell, a mathematician at the University of Tennessee and long-time GIMPS volunteer. The implication is that we might find new mathematical patterns.

“It took me 14 years and he found one in just four months. Can you believe it!” And the GIMPS software itself also happens to have its uses for people with no interest in numbers. It is sufficiently demanding that many volunteers use it to stress test their custom-built computers. Indeed, that is exactly what Patrick Laroche of Ocala, Florida, was doing late last year when one of his souped-up machines discovered the 51st Mersenne prime – the biggest yet. Laroche didn’t want to generate interest in the search for primes, preferring to keep a low profile.

However, Woltman says Laroche had tested just four numbers before he struck gold. But when it comes to the allure of giant primes, practical value is beside the point. Mathematicians treasure them because they are exquisite. Caldwell likes to compare Mersenne primes to giant diamonds. “Probably the most practical use for diamonds is diamond dust on blades and drills,” he says. “The same is true of primes. The small ones are used everywhere in encryption. But the really big ones, they’re museum pieces.” The most devoted prime hunters see themselves as part of a collective enterprise, pushing out to the furthest reaches of the number line in search of these rare gems. Which probably explains why Pace is anything but exasperated by Laroche’s lucky break. “I was happy for him,” he says. “OK, it took me 14 years and he found one in just four months. Can you believe that! But I have tested thousands of candidates over the years, so every time a new prime is discovered I always feel I had a hand in it.” ❚ Daniel Cossins is a staff features writer at New Scientist. His favourite prime number is 7 10 August 2019 | New Scientist | 41

Features Cover story

The hidden cause of disease Everything from heart disease to Alzheimer’s has been blamed on unhealthy lifestyles. But could pervasive bacteria be the true culprits, asks Debora MacKenzie

F

OR decades, health experts have been lecturing us about our bad habits, blaming them for the surge in “lifestyle diseases”. These often come on as we age and include heart disease, Alzheimer’s, type 2 diabetes and some cancers. Worldwide, 70 per cent of all deaths  are now attributed to these conditions. In the UK, it is a whopping 90 per cent. Too much red meat, too little fruit and veg, smoking, drinking, obesity and not enough exercise appear to make all these diseases more likely – and having any of them makes getting the others more likely. But no one really knows why, and we still haven’t worked out what causes any of them. Alzheimer’s is now one of the UK’s biggest killers, yet the main hypothesis for how it originates imploded this year after drugs based on it repeatedly failed. High blood cholesterol is blamed for heart attacks, except most people who have heart attacks don’t have it. What we do know is that these conditions usually start causing symptoms later in life, and their prevalence is skyrocketing as we live longer. They all turn inflammation, the method our immune system uses to kill

42 | New Scientist | 10 August 2019

invaders, against us. And, by definition, these diseases aren’t communicable. They are down to bad habits and unlucky genes, not germs. Right? Not necessarily. In disease after disease, we are finding that bacteria are covertly involved, invading organs, co-opting our immune systems to boost their own survival and slowly making bits of us break down. The implication is that we may eventually be able to defeat heart attacks or Alzheimer’s just by stopping these microbes. Until now, bacteria’s involvement

“The main hypothesis for how Alzheimer’s originates imploded this year”

completely eluded us. That’s because they tend to work very slowly, stay dormant for long periods or hide inside cells. That makes them difficult to grow in culture, once the gold standard for linking bacteria to disease. But now DNA sequencing has revealed bacteria in places they were never supposed to be, manipulating inflammation in just the ways observed in these diseases. The findings are so contrary to received wisdom and emerging in so many diseases, each with its own separate research community, that awareness of all this is only starting to hit the mainstream (See “Germ theory”, page 46). And predictably, as with any paradigm shift, there is resistance. But some researchers, frustrated by years of failure to find causes, and therefore real treatments, for the diseases of ageing, are cautiously excited. And with reason: this could change everything. The worst culprits, which seem to play a role in the widest range of ailments, are the bacteria that cause gum disease. This is the most widespread disease of ageing – in fact, “the most prevalent disease of mankind”, says Maurizio Tonetti at the University of

MATT CHASE

Hong Kong. In the US, 42 per cent of those aged 30 or above have gum disease, but that rises to 60 per cent in those 65 and older. It has been measured at 88 per cent in Germany. Strikingly, many of the afflictions of ageing – from rheumatoid arthritis to Parkinson’s – are more likely, more severe, or both, in people with gum disease. It is possible that some third thing goes wrong, leading to both gum disease and the other maladies. But there is increasing evidence that the relationship is direct: the bacteria behind gum disease help cause the others. Circumstantial evidence is certainly damning. In the US, states that put federal

Medicaid funds towards people’s dental costs, including those related to preventing or treating gum disease, ultimately pay between 31 and 67 per cent less than states that don’t, to help those people later with heart attacks, diabetes, strokes and cancer. Private insurance companies report similar patterns, says David Ojcius at the University of the Pacific in San Francisco. But how can the bacteria that cause gum disease play a role in all these conditions? To answer that, we have to look at how they turn the immune system against us. Your mouth hosts more than 1000 species of bacteria, in a stable community where

potential bad actors are kept in check by peaceful bacteria around them. Elsewhere in the body, including on the skin or the lining of the gut, communities of bacteria live on a continuous sheet of cells, where the outermost layer is constantly shed, getting rid of invasive bacteria. But your teeth can’t cast off a layer like that, says Tonetti. There, the bacteria live on a hard surface, which pierces through the protective outer sheet of cells. When the plaque the bacteria on your teeth live in builds up enough to harden and spread under the gum, it triggers inflammation: immune cells flood in and destroy both microbes and our own infected cells > 10 August 2019 | New Scientist | 43

Master of concealment If the bacterium Porphyromonas gingivalis is partly to blame for a wide range of inflammatory diseases such as Alzheimer’s and heart disease (see main story), why not just kill it? Unfortunately, it is brilliant at dodging our defences: lurking inside cells where antibodies can’t reach it, and often lying dormant, making it invisible to antibiotics, which mostly attack bacteria as they divide. We could vaccinate against P. gingivalis, but vaccines work by inducing antibodies. People with gum disease already make antibodies against the bacteria, but these seem to do little to stop it. It may be better to have the antibodies early and stop P. gingivalis invading our mouths when we are young. Eric Reynolds at the University of Melbourne is running a clinical trial of a vaccine that targets gingipains, the protein-digesting enzymes that P. gingivalis makes. Caroline Genco of Tufts University in Massachusetts is also working on an anti-gingipain vaccine. “The key is to prevent it ever colonising,” she says. The trouble is, many of us already host the bacteria. Routine gum abrasion, through eating or brushing your teeth, can release the microbes into your bloodstream, even if you don’t have gum disease. There it can spread throughout the body and promote inflammation. In studies by the company Cortexyme, antibiotics killed P. gingivalis in mice, but it rapidly became resistant. To limit resistance, instead of trying to kill the bacteria, it may be better to block its ability to cause disease. Cortexyme has a drug that does this by blocking gingipains. In mice, it reversed Alzheimer’s-like brain damage without driving resistance in P. gingivalis, and in a small trial in humans it improved inflammation and some measures of cognition. A large trial is now under way. But as all these diseases involve inflammation, why not just block that? If we did, it could leave you open to the germs that this immune response does fight off or block other vital things that immune signals do. That’s why some companies are working on drugs to block only specific inflammatory signals. But tampering with our complex immune systems without doing damage – as P. gingivalis shows – will be a significant challenge.

44 | New Scientist | 10 August 2019

(see diagram, page 45). If this goes on too long, an oxygen-poor pocket develops between gum and tooth. A handful of bacteria take advantage of this and multiply. One of them, Porphyromonas gingivalis, is especially insidious, disrupting the stable bacterial community and prolonging inflammation. This might seem a strange thing to do. Most pathogens try to block or avoid inflammation, which normally kills them before it shuts down again. Starting in our 30s and 40s, this shutdown begins failing, leading to the chronic inflammation involved in diseases of ageing. No one knows why. P. gingivalis may have a hand in it. It actually perpetuates inflammation by producing molecules that block some inflammatory processes, but not all of them, says Caroline Genco of Tufts University in Massachusetts. The resulting weakened inflammation never quite destroys the bacteria, but keeps trying, killing your own cells in the process. The debris is a feast for P. gingivalis, which, unlike most bacteria, needs to eat protein. The destruction also liberates the iron that bacteria need and which the body therefore normally keeps locked up. “These bacteria manipulate their interaction with the host immune response to enhance their own survival,” says George Hajishengallis at the University of Pennsylvania.

Gum control Eventually, the infected tooth falls out – but long before that P. gingivalis escapes into the bloodstream. There your immune system makes antibodies against it, which usually defend us from germs. But P. gingivalis antibodies seem to be more a mark of its passing than protection. People with these antibodies are actually more likely to die in the next decade than those with none, and more likely to get rheumatoid arthritis or have a heart attack or stroke. This could be because, once in the blood, P. gingivalis changes its surface proteins so it can hide inside white blood cells of the immune system, says Genco. It also enters cells lining arteries. It remains dormant in these locations, occasionally waking to invade a new cell, but otherwise remaining hidden from antibiotics and immune defences. However, even hunkered down within our cells, P. gingivalis continues to activate or block different immune signals, even changing a blood cell’s gene expression to make it migrate to other sites of inflammation, where the bacteria can hop out and feast again.

“A bacterial cause could explain the genetic risk for Alzheimer’s”

One explanation for why gum disease makes you more likely to get conditions like diabetes and Alzheimer’s disease is that it adds to your general “inflammatory load”. But P. gingivalis may act more directly too: the bacteria have been detected in inflamed tissue in the brain, aorta, heart, liver, spleen, kidneys, joints and pancreas in mice and, in many cases, humans. The strongest case against P. gingivalis is as a cause of Alzheimer’s disease. This constitutes more than two-thirds of all dementia, now the fifth largest cause of death worldwide. It was long blamed on the build-up of two brain proteins, amyloid and tau. But that hypothesis is crumbling: people with dementia may lack this build-up, while people with lots of the proteins may have no dementia – and most damningly, no treatments reducing either have improved symptoms. Then, in January, teams at eight universities and the San Francisco company Cortexyme found a protein-digesting enzyme called gingipain, produced only by P. gingivalis, in 99 per cent of brain samples from people who died with Alzheimer’s, at levels corresponding to the severity of the condition. They also found the bacteria in spinal fluid. Giving mice the bacteria caused symptoms of Alzheimer’s, and blocking gingipains reversed the damage. Moreover, half of the brain samples from people without Alzheimer’s also had gingipain and amyloid, but at lower levels. That is as you would expect if P. gingivalis causes Alzheimer’s, because damage can accumulate for 20 years before symptoms start. People who develop symptoms may be those who accumulate enough gingipain damage during their

Linking dementia and gum disease Hear Sim Singrao discuss oral health and Alzheimer’s risk newscientistlive.com/gum-disease

Porphyromomas gingivalis evades our defences and drives inflammation

A.B. DOWSETT/SPL

lifetimes, says Casey Lynch at Cortexyme. Still, dementia researchers have questioned how a bacterial cause can account for genetic risk factors for Alzheimer’s. But it may actually explain them, according to a team in Sweden. The people with the highest genetic risk produce a particular form of an immune protein called ApoE that is destroyed in the disease. Last year, Swedish researchers discovered that gingipains are better at destroying that particular ApoE than other forms. P. gingivalis may literally break our hearts too. There is growing evidence for a causal link to atherosclerosis, or “hardening of the arteries”. Researchers have found P. gingivalis in the fatty deposits that line arterial walls and cause blood clots. When bits of clots clog blood vessels in hearts or brains, they cause heart attack and stroke. The bacteria trigger the molecular changes in artery linings that are typical of atherosclerosis, says Genco. We have also found that P. gingivalis creates the lipoproteins thought to trigger atherosclerosis, causes it in pigs and affects arteries much like high fat diets. Lakshmyya Kesavalu at the University of Florida, who has cultured viable P. gingivalis from the atherosclerotic aortas of mice, calls the bacteria “causal”. The American Heart Association agrees that gum disease is an “independent” risk factor for cardiovascular disease, but doesn’t call it causal. It argues that although treating gum disease improves hardened arteries, no studies have found that it reduces heart attacks

or strokes. But, according to Steve Dominy at Cortexyme, that could be because, while gum treatment helps arteries by easing inflammatory load, it doesn’t eradicate the P. gingivalis already in the blood vessels. Clinical trials are needed to firm up the connection, but these are expensive and difficult – especially when the bacterial hypothesis is still in its early days. The link is clearer for type 2 diabetes, in which people lose sensitivity to insulin and eventually can’t make enough to control blood sugar. It is currently a pandemic, blamed on the usual lifestyle suspects.

Down in the mouth A new hypothesis suggests that the bacteria behind gum disease may also cause many more serious conditions Healthy teeth and gums

Advanced gum disease

Alzheimer’s disease Bacteria including Porphyromonas gingivalis live in plaque on teeth Plaque builds up, causing inflammation that creates a pocket between gum and tooth

P. gingivalis bacteria promote and feed off inflammation Bacteria get into the bloodstream

Inflammation caused by gum disease may worsen symptoms, but the bacteria may also be a direct cause

Atherosclerosis

Growing evidence shows that P. gingivalis can contribute to the hardening of the arteries that leads to stroke and heart attack

Diabetes

Treating gum disease can improve diabetic symptoms

Diabetes worsens gum disease, because high blood sugar levels hurt immune cells. But gum disease also worsens diabetes, and treating it helps as much as adding a second drug to the regimen taken by someone with the condition, according to the American Academy of Periodontology. Treatment is now recommended by diabetes associations, yet none of them list gum disease as a risk factor. As with other conditions, there is evidence that P. gingivalis isn’t promoting diabetes just by adding to the body’s inflammatory load, but may also be acting directly in the liver and pancreas to cut insulin sensitivity. “It is very hard to prove causation in a complex disease,” says Genco. We know that mice given a mouthful of P. gingivalis get gum disease – and diabetes, rheumatoid arthritis, atherosclerosis, fatty liver disease and Alzheimer’s-like symptoms. We know that, in humans, gum disease makes the other diseases more likely, and that P. gingivalis lurks in the affected tissues and makes the precise cellular changes typical of these conditions. If these diseases actually share a more direct cause, it might finally suggest cures (see “Master of concealment”, far left) – as well as explaining just how the same bad habits bring them all on. People who drink more alcohol tend to have more P. gingivalis and are more susceptible to gum disease. Tobacco smoke helps the bacteria to invade gum cells. Exercise, the only known way to lower your risk of Alzheimer’s, improves gum disease by damping inflammation and ending P. gingivalis’s feast. > 10 August 2019 | New Scientist | 45

Germ theory

RHEUMATOID ARTHRITIS P. gingivalis is present in the joints of people who get this condition before symptoms appear and is the only bacterium known to make a chemical involved in the disease.

PARKINSON’S DISEASE P. gingivalis and its protein-munching enzymes, gingipains, are found in the blood of people with Parkinson’s disease, and promote the inflammation and abnormal clotting seen in the condition.

KIDNEY DISEASE Gum disease is associated with chronic kidney disease and gum treatment seems to help the kidneys.

FATTY LIVER DISEASE There is far more P. gingivalis in affected livers than in healthy ones, and it worsens the disease in mice. Treating the gums helps.

CANCER The bacteria has been found in early-stage cancers of the mouth, oesophagus, stomach and pancreas, and changes cell functions in ways typical of these cancers.

MACULAR DEGENERATION Injecting the bacteria into the retina seems to damage eyesight by producing age-related macular degeneration in mouse studies.

PRETERM BIRTH Gum disease, caused by P. gingivalis, has been established as a risk for premature birth.

46 | New Scientist | 10 August 2019

If gum disease bacteria drive many other conditions, we could stop them early

DEEPOL/PLAINPICTURE

A range of bacteria may play a role in supposedly non-communicable diseases. Propionibacterium acnes, for instance, is best known for causing acne, but also seems to damage the discs that cushion your spinal vertebrae, a common cause of severe back pain, says Ondrej Slabý of Masaryk University in the Czech Republic. It has also been implicated in prostate cancer. But it is Porphyromonas gingivalis that has been linked to the widest array of conditions:

“It’s too easy to mock the notion that flossing may contribute to brain health” Then there is diet. Douglas Kell at the University of Manchester, UK, believes our blood contains many dormant bacteria, needing only a dose of free iron to awaken and cause disease. That could be why eating too much red meat and sugar or too little fruit and veg lead to these diseases: all increase your blood iron.

The long haul No official medical advice for warding off these diseases includes “see your dentist”, at least not yet. “Periodontal disease should be better recognised by the community as a clearly established risk factor,” says Dominy. One of the clearest risks is for Alzheimer’s. But guidelines for avoiding Alzheimer’s published in May by the World Health Organization (WHO) say nothing about preventing gum disease. “There is insufficient evidence to suggest that treating gum disease reduces the risk of dementia,” says Benoit Varenne at the WHO, echoing the verdict on heart disease, even though the same caveats probably apply. The guidelines recommend avoiding diabetes and high blood pressure, despite stating that there is little or no evidence that this stops Alzheimer’s. “It’s perhaps too easy to mock the notion that flossing your teeth may contribute to

good brain health,” says Margaret Gatz at the University of Southern California. And that may be part of why this idea hasn’t yet taken off in mainstream medicine. “There is a history of dental and medical doctors working apart and not cooperating,” says Thomas Kocher at the University of Greifswald, Germany. But it also reflects the long-held belief that heart attacks and the other conditions are primarily the result of bad lifestyle, not bacteria. Such underlying paradigms in science can take decades to change. That happened when bacteria, not stress and stomach acid, were shown to cause stomach ulcers. After decades pursuing these explanations, many medical experts are reluctant to admit that amyloid may not cause Alzheimer’s and high cholesterol may not lead to heart disease. With the world’s population ageing, we don’t have decades before these diseases become a health crisis severe enough to break health systems and societies. We need a new paradigm. That means facing the possibility that it may all be down to germs, after all. ❚

Debora MacKenzie is a New Scientist consultant based in Geneva, Switzerland. She reports on biomedical sciences

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NRC Research Associateship Programs

The National Academy of Sciences, Engineering, and Medicine offers postdoctoral and senior research awards on behalf of 23 U.S. federal research agencies and affiliated institutions with facilities at over 100 locations throughout the U.S. and abroad. We are actively seeking highly qualified candidates including recent doctoral recipients and senior researchers. Applications are accepted during 4 annual review cycles (with deadlines of February 1, May 1, August 1, November 1).

Interested candidates should apply online http://sites.nationalacademies.org/PGA/RAP/PGA_046398 Awardees have the opportunity to: • • • •

conduct independent research in an area compatible with the interests of the sponsoring laboratory devote full-time effort to research and publication access the excellent and often unique facilities of the federal research enterprise collaborate with leading scientists and engineers at the sponsoring laboratories

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Applicants should hold, or anticipate receiving, an earned doctorate in science or engineering. Degrees from universities abroad should be equivalent in training and research experience to a degree from a U.S. institution. Some awards are open to foreign nationals as well as to U.S. citizens and permanent residents.

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Join our Assessment Associate Team Pearson have exciting opportunities for Science Teachers to become H[DPLQHUVIRURXU*&6(*&(TXDOLȴFDWLRQV:HDUHNHHQWRUHFUXLW WHDFKHUVDFURVVWKH8.ZKRDUHFXUUHQWO\WHDFKLQJRUUHFHQWO\UHWLUHG This is an excellent opportunity to: • Develop your understanding of assessment • Interact with fellow educational professionals • Inspire fresh ideas and approaches to teaching your subject • Boost your income )RUPRUHLQIRUPDWLRQDQGKRZWRDSSO\SOHDVHYLVLWRXUZHEVLWH WLQ\XUOFRP\MUWWRILQGWKHUROHIRU\RX$OWHUQDWLYHO\UDLVHDTXHU\DW DVVRFLDWHSHDUVRQFRP

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The back pages Puzzles Cryptic crossword, a clever code and the quick quiz p52

Feedback Brexit’s moonshot and worm readers: the week in weird p53

Almost the last word Hidden in plain sight: readers explain the phenomenon p54

Liana Finck for New Scientist A cartoonist’s take on the world p53

The Q&A Anca Dragan on how to get robots working with humans p56

How to be a maker 2 Week 5

Intruder alert Some animals are less welcome in the garden than others, says Hannah Joshua. This device will help keep them away

New stuff you need Kitchen foil Soft sponges Plastic document folder Piezo buzzer Electrical wire Waterproof container

For next week DS18B20 waterproof temperature probe Resistors: 1x4.7 kohm and 1x470 ohm 5mm red LED Old wire coat hanger

Next in the series 1 Moisture-sensing plant 2 Moisture and temperaturesensing plant 3 Plant auto-waterer 4 Tweeting wildlife cam 5 Pest scarer 6 BBQ thermometer Perfectly cooked food while you relax 7 Rain alarm 8 Mini weather station 9 &10 Remote controlled pest-proof bird feeder parts 1&2

"PEST"

DAVID STOCK FOR NEW SCIENTIST

Hannah Joshua is a science writer and maker based in London. You can follow her on Twitter @hannahmakes

WHAT did your motion-sensitive wildlife camera spot last week? Perhaps you saw beautiful birds, or hedgehogs snuffling around at twilight. Or perhaps you snapped a photo of the neighbourhood cats digging up your plants, or foxes menacing your bins. If it was either of this second pair, this week’s project will help protect your petunias and keep a lid on your garbage by surprising any creatures that stray where they aren’t welcome. To detect the intruders, we are going to make a simple pressure plate switch that will trigger when stepped on. Take the plastic folder and cut along the spine so you have two similarly sized sheets of plastic. Wrap each with kitchen foil so one side is totally covered and secure the foil with tape or glue. Next, take two lengths of wire and strip a few centimetres of the plastic insulation off both ends. Tape one piece of wire to each plastic sheet so the bare end is in contact with the foil. Ordinary tape is fine, but for a more reliable connection you could use copper tape, which conducts electricity. Cut your sponge into pieces a few centimetres across and arrange them around the edge of one of the sheets on the foilcovered side. Place the other sheet on top so the foil sides are facing and secure the sponges in place. When something presses on top, the sponges will compress, bringing the foils into contact, completing a circuit. Now connect the other ends of the wires to your BBC micro:bit.

SPONGES

FOIL PLATES

Make online Projects so far and a full list of kit required are at newscientist.com/maker Email: [email protected]

Use crocodile clips to attach one to pin 1 and the other to ground. That is the switch done. Now we need a noise maker to deter whatever steps on the device. Connect the red wire of your piezo buzzer to pin 0 and the black wire to ground. Moving on to the MakeCode editor, grab an “if then” block from “Logic” and snap it into “forever”. Take “pin 0 is pressed” from “Input” and use the drop-down to change it to “p1”, then slot this over the default “true” in your “if” block. Now, from the “Music” menu, take a “start melody” block and nestle it into your “if”. Use the drop-down to choose a melody – the default

“dadadum” is suitably scary. You are now ready to go outside. Put the micro:bit, battery and piezo in a weatherproof container and cover the foil plates with something light and rainproof – perhaps a plastic bag. This will prevent rainwater getting in and causing erroneous connections between the sheets, as well as disguising your device. You can customise the scarer as well, changing the tune in case wildlife gets wise to it. Or find another way to spook them: flashing lights, or a waving flag or scarecrow attached to a mini motor. Just be sure to warn any guests that step into your garden. ❚ 10 August 2019 | New Scientist | 51

The back pages Puzzles Quick quiz #15

Cryptic crossword #12 Set by Wingding 











 





 













ACROSS 1 Mammal’s first to consume flesh (4) 3 After card game, Leslie makes high-pitched noises (8) 9 Singing lady visiting Royal Institution with new astronaut (7) 10 “Criminals!” – I start to libel oil company (5) 11 Breaking up over thin zone, point of no return? (5,7) 14 22 down cycling in a curved line (3)

DOWN 1 Puzzled at German astronomical object (8) 2 May be right to use a hook (5) 4/7 Resistance fighter from Chinese ethnic group on his own (3,4) 5 Heartless snail and mosquito disturbed by sound source at night (12) 6 Safety gear made of dog hair? (3,4) 7 See 4 down

3 If you douse yourself in beta-ionone, you are liable to come up smelling of what? 4 Amphibians, reptiles and most birds use a single orifice for urination, defecation and sexual reproduction. What is it called?





16 Relation has allocation reduced (5) 17 Connect time, current and energy (3) 18 Athlete’s cups smashed in defunct vehicle (5,7) 21 Tesla and one relative travelling west in circular route (5) 22 Pain is sacred, though some rejected probe (7) 23 Reward almost certain to constitute a valuable discovery (8) 24 Spoils neighbour (4)

8 After losing son, the oysters cry, sadly – they are in your blood (12) 12 Sounds like cereal may be some time (5) 13 Green newt winces every now and then – she gets it from her parents (8) 15 Efficient wire wrapped around sound system (7) 19 Big cat heard in forest (5) 20 Distant cloud obscured by Io or Titan (4) 22 Fish has tail cut off in transport (3)

Answers and the next quick crossword next week.

52 | New Scientist | 10 August 2019

2 In 2015 to 2016, Mark stayed on the ground while Scott orbited Earth on the International Space Station. What were they up to?







1 The area around Solnhofen in Bavaria, Germany, is the source of all 12 fossil specimens of which pioneering flying creature?

5 Underlying Fort Worth and surrounding areas of Texas, which geological formation is thought to contain the largest reserves of any onshore natural gas field in the US?

#16 Clever code Rashmi told us that she had to make up some codes, ones that preferably have a unique quality to them. “For a four-digit code, I chose 2020, because it has two 0s, zero 1s, two 2s and zero 3s. I chose 3211000 for a seven-digit code.” She then told us that she used the same idea for a 10-digit code. What was this code? Answer next week

#15 Lines through the chessboard Solution

Answers below

Quick Crossword #37 Answers ACROSS 1 Nymph, 4 Logic bomb, 9 Walkman, 10 Medulla, 11 Orange, 15 Ice, 16 Exxon, 18 Radii, 20 Nappa, 22 Rayon, 23 Phi, 24 Teletext, 26 Unplug, 28 Eardrum, 30 Anaemia, 32 Messenger, 33 Torus DOWN 1 Newtonian, 2 Malware, 3 Hum, 4 Lung, 5 Gem, 6 Codon, 7 Oilseed, 8 Bragg, 12/13 Greta Thunberg, 14 Henry, 17 Xerox, 18 Renin, 19 Isinglass, 21 Pylorus, 23 Polymer, 24 Therm, 25 Three, 27 Pair, 29 Meg, 31 Ant

It is possible to cut through all 64 squares with seven lines. There are several ways to do it, but here is one approach. In fact, it is always possible to draw lines through an NxN grid with no more than N-1 lines.

Quick quiz #15 Answers 1 Archaeopteryx 2 Investigating the effect of space flight on the body – the Kelly brothers are identical twins and are both astronauts 3 Roses 4 The cloaca. Some male birds also have a penis to aid the reproductive process 5 The Barnett Shale



Puzzle set by Paul Tissier

Get in touch Email us at [email protected] [email protected]

The back pages Feedback Crash landing “We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organise and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone and one which we intend to win, and the others, too.” President John F. Kennedy’s words to a packed stadium at Rice University, Texas, in September 1962 ring down the ages – perhaps more so than those of the UK’s new prime minister, Boris Johnson. During the recent 50th anniversary celebrations of the Apollo 11 moon landing, he was keen to invoke the spirit of Kennedy for his own moonshot: avoiding a “hard” Irish border in the event of the UK leaving the European Union. “It is absurd that we have even allowed ourselves to be momentarily delayed by these technical issues,” he averred. “If they could use hand-knitted computer code to make a frictionless re-entry to the Earth’s atmosphere in 1969, we can solve the problem of frictionless trade at the Northern Irish border.” Alwyne Kennedy – no relation to JFK, we presume – is keen to point out one technical issue: “Apollo 11’s re-entry into Earth’s atmosphere was far from frictionless. If it wasn’t for friction with the atmosphere, the returning Apollo capsule would never have slowed down and would have smashed to Earth at tens of thousands of miles per hour.” True, thinks Feedback, but it is a vastly different kettle of fish when, like the UK, you are attempting to achieve escape velocity. Or is it? We bury our head in our hands.

Rocket man Feedback’s desire to pretend politics isn’t happening is disturbed by the plop of post on the mat. “I thought you might like this new unit of measurement,” writes Barry Cash. Always! He goes on to relay news from

political writer Mark Pack that NASA’s Saturn V rocket weighed roughly “the equivalent of 31,000 Boris Johnsons”. Sigh. Johnson is certainly known for his ability to expel great volumes of hot air. But as for Barry’s speculation that “he’ll be more use as a unit of weight than he will be as prime minister”, you might very well think that – but we couldn’t possibly comment.

Liana Finck for New Scientist

Give them an inch While we are waiting for the Johnson to catch on, we might as well turn to Edwardian cosplayer and arch-Brexiteer Jacob ReesMogg. As the newly installed leader of the UK House of Commons, he has started his own campaign to bring down the metric system. He has issued his staff with a style guide demanding that untitled men be labelled “Esq.”, that double spaces follow a full stop and that all measures be given in imperial units. Feedback notes that the UK’s switch to (mostly) metric was formalised in 1965, four years before Rees-Mogg was born, so he may be protesting a little too much. Should he find himself struggling to fathom the furlong and the fluid scruple, we have a slide rule he can borrow.

The worm’s turn Enough of these high matters of state. “The 6 July issue notes that the worm community is pleased with the recent neural map of the nematode,” writes Sylvia Potter. “I remarked to my son my surprise that worms read New Scientist; he thought it was probably read to them. Could you settle the argument please?” Delighted to, Sylvia. We can confirm that the magazine is read to them by researchers who have subscriptions, as nematodes are notoriously slippery customers when it comes to payment. We also have a strong following among budgerigars, thanks to owners lining their cages with old issues of this fine magazine.

Brassed off Barry Cash writes: “I’m listening to The Art and Science of Blending on BBC Radio 4 and they have just introduced Dr Jim Beveridge, who has been the master blender at Johnnie Walker for nearly four decades.” A fine case of nominative determinism. Yet in all Feedback’s years of publishing these instances, Barry points out, we have never quite deduced how the process works. “For example, my name is Cash. Why do I never have any?”

Bloody stupid You really won’t give up, will you, dear readers? “It’s strange how fact can sometimes echo fiction,” writes Richard Green. Watching Boris Johnson enter Downing Street, he is reminded of B. S.  Johnson, an infamous character from Terry

Pratchett’s Discworld series. He sends in this description from a Discworld fan page: “Although evidently able in certain fields, Johnson is notorious for his complete inability to produce anything according to specification or common sense, or (sometimes) even the laws of physics. This fact never stopped him from trying, however. He is also known as Bloody Stupid ‘It Might Look A Bit Messy Now But Just You Come Back In Five Hundred Years’ Time’ Johnson and Bloody Stupid ‘Look, The Plans Were The Right Way Round When I Drew Them’ Johnson.” Feedback merely forwards this on.

Signs of the times Spotted by David Martin in Bookends Bookshop, Cornwall: “Post-apocalyptical science fiction has been moved. It may now be found in Current Affairs.”  ❚

Got a story for Feedback? Send it to New Scientist, 25 Bedford Street, London WC2E 9ES or you can email us at [email protected] 10 August 2019 | New Scientist | 53

The back pages Almost the last word Why does a lightning strike make the air sizzle and light bulbs glow?

Schrödinger’s scissors

Stephen Mitroff, professor of cognitive neuroscience George Washington University, Washington DC There is no single answer to this question. A visual search can fail for any number of reasons. If the person had a different picture in their mind of the item while searching, that could interfere with finding it. For example, they might be thinking of an older or different version of an object. Other items that were recently looked at but weren’t the desired object can also interfere with finding an item. Stress can affect performance, and just being tired can also make searches hard. Janet Mackenzie Thurso, Highland, UK Once when I was looking frantically for something, my daughter came in and said: “Don’t look for, mum, look at”. I did this, and it worked. Maybe this is what happened with your reader. He was looking for, his wife came in and looked at.

Future fossils If, some day, our civilisation fries itself out of existence, will new reservoirs of fossil fuels eventually accumulate, and could they power some future industrial revolution?

Tony Power Sydney, New South Wales, Australia Coal is the remains of plants, collected long ago in slowly sinking basins. The northern hemisphere coal deposits built up in the Carboniferous period, between about 360 and 300 million years ago. In the southern hemisphere, coal was mostly deposited in the Permian (some 54 | New Scientist | 10 August 2019

ALEXEYS/GETTY

I was once looking for nail scissors but couldn’t see them. My wife then entered the room and immediately saw the scissors in plain view, exactly where I had been looking. Why couldn’t I see them until she found them?

This week’s new questions Lightning bulb A summer storm woke me around 2 am. I heard a sizzling sound before lightning struck about 100 metres away. Then I saw a 1.5-volt solar-powered outside light glowing like a 50-watt bulb. It faded after a few minutes. What caused the sizzling sound and made the light glow so brightly? Douglas Fairchild, Two Harbors, Minnesota, US Battery power Why has there never been an international standard requiring manufacturers to display the capacity of alkaline batteries? All we have to go on is words such as “super power” or “long life” on the packaging. I want a number! Stephen Brown, Girona, Spain Time and tide What is the smallest body of water that is influenced by the moon’s gravitational pull? Hilary Perry, Dinas Powys, Vale of Glamorgan, UK

300 to 250 million years ago). Around 290 million years ago, several species of fungi evolved that could digest the main components of wood: cellulose, lignin and hemicellulose. One theory suggests that fossil fuels formed before these fungi evolved, but afterwards, plant material rotted and was returned to the carbon cycle. Deposits known as brown coal formed more recently, but they are relatively uncommon and low quality. So if the fungus theory is correct, unless the fungi get fried before the trees, not much coal will form in the future. Jeff Dickens Strachan, Aberdeenshire, UK Assuming we don’t completely sterilise the planet in frying our

civilisation, the answer is almost certainly yes. All it takes is time and the continued tectonic development of the planet. Plate tectonics continuously pushes and pulls Earth’s crust in different directions. If a basin forms, it could be filled by sediment eroded off uplifted areas. To form a fossil fuel accumulation, certain conditions are required. Swampy delta regions are good for coal. For oil and gas, there needs to be a substantial influx of organic material. Marine microorganisms do nicely; the process will then

work even if we trash the rest of the biosphere. The present day Black Sea is a good example, where a deep water basin has become anoxic. This lack of oxygen has resulted in the preservation of the organic material falling into the basin. On top of that, we need suitable temperatures and pressures, and a geological event that results in the surrounding rocks forming effective traps for the petroleum fluids. This process can happen surprisingly quickly, geologically speaking. A lot of the action described above is ongoing, and has only recently generated some oil and gas fields, in basins like the Gulf of Mexico and the Caspian Sea. You could get your first new accumulations in as little as a couple of million years. Finally, there are some schools of thought that postulate an abiogenic origin for some fossil fuel accumulations. In other words that natural gas develops from methane deep in the mantle, for example, without the input of living organisms. So you might not even need the biosphere, although you might expect the resulting volumes would be much lower. Douglas Thompson Whitford, Flintshire, UK Of course new reservoirs of hydrocarbons will accumulate after humanity has shuffled off its mortal coil. Whether they power a future industrial revolution is another matter and could depend on whether a future intelligent community had access to information about the disastrous way we exploited our own reserves. ❚

Want to send us a question or answer? Email us at [email protected] Questions should be about everyday science phenomena Full terms and conditions at newscientist.com/lw-terms

The back pages The Q&A

Computer scientist Anca Dragan devotes her life to helping robots work out just how weird and unpredictable humans really are

As a child, what did you want to do when you grew up? I got interested in computer science at an early age, but before then, it mostly depended on which movie last inspired me.

Explain what you do in one easy paragraph. I get robots to account for humans when deciding on their actions. On the one hand, this means giving them the ability to make predictions about what we will do next and make sure they can coordinate with us, like when autonomous cars negotiate for their turn during a merge in traffic. On the other hand, this means giving them the ability to infer what it is that we want them to do. How do I want my car to drive? What help do I need from my personal home robot?

What do you love most about what you do? I love that I get to focus on problems that I believe will be relevant to us in the long term, like how to define what we want machines to do or how to get machines to better understand us.

What’s the most exciting thing you’re working on right now? We’re working on making machines more adaptable to the wrong model of human behaviour. For instance, we can get robots to figure out where you’re heading by assuming your actions are relatively rational. But what if you’re avoiding something the robot doesn’t know about? Or what if the robot assumes you’re thinking many more steps ahead than you actually are? Or maybe the robot assumes you’re trying to teach it something, but you’re really just doing your own thing. Can robots be more robust to such misspecification of human behaviour?

Were you good at science at school? I was OK at physics and pretty terrible at the rest. Let me put it this way: I don’t think you would have looked at me in school and anticipated that I’d become a professor at one of the top universities worldwide. In the end, I clicked very well with research, I took as much initiative as I could and I got very lucky. 56 | New Scientist | 10 August 2019

If you could send a message back to yourself as a kid, what would you say? I definitely wouldn’t say, “Don’t worry, everything will be great”, because I think the worrying is what made me ambitious. Growing up in Romania, my dad told me that if I didn’t do exceptionally well in school, I’d have to go work on the farm – and I believed him!

If you could have a long conversation with any scientist, living or dead, who would it be? I’d really love to talk to Alan Turing.

How useful will your skills be after the apocalypse? Not at all useful. Unless our problem is that AI systems don’t know what we want, I’ve got nothing.

Do you have an unexpected hobby, and if so, please will you tell us about it?

I love sailing because I get to take advantage of living by the water, despite the fact that the San Francisco Bay is so cold. I really need to focus to make sure I don’t do anything bad to the boat, so it’s almost like a way of meditating.

OK, one last thing: tell us something that will blow our minds… Imagine you are learning to do a task and a robot is trying to help you. You would think that the better you are at the task, the better the outcome for you and the robot. It turns out that isn’t true: success relies a lot on whether what you do and what the robot does gel together. This is one aspect that makes assisting people hard.  ❚ Anca Dragan is a professor in computer science at the University of California, Berkeley, where she runs the InterACT lab and is a co-principal investigator in the Center for Human-Compatible AI. ANDREY BAYDA/SHUTTERSTOCK

“My dad told me that if I didn’t do exceptionally well in school, I’d have to work on the farm – and I believed him!”