EVOLUTION

The Human Predator

EXPLORATION

Journey to the Bottom of the Sea

NEUROSCIENCE

The Brains Genetic Geography

of the universe

2014 Scientific American

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SCIENTIFIC AMERICANApril 2014 Volume 310, Number 4

ON THE COVERShortly after the big bang, all w as black. Primordial gas cooled and coalesced for hundreds of millions of years, enshrouding the universe in darkness. W hen the giant first stars eventually did appear, their light w as quickly snuffed out by this fog of gas. Astronom ers are only now piecing together the 13-billion-year-old mystery of how the fog lifted. Im age by Kenn Brown, M ondolith ic Studios.

82

FEATU R ESA S T R O N O M Y38 The First StarlightN ot long after the big bang, all ligh t left the cosmos.How and why did it re tu rn? B y M ichael D. Lem onickE V O L U T IO N

46 Rise of the Human PredatorOur ancient ancestors penchant for m eat could account for m uch of w ho we are today. B y Kate WongT H E F U T U R E O F M E D IC IN E52 The RNA RevolutionLong overlooked as a m ere cellular housekeeper,RNA has em erged as a pa th to a new w orld of m edical treatm ent. B y Christine G orm an a n d D ina Fine M aronM A R IN E E X P L O R A T IO N

60 Journey to the Bottom of the SeaHigh-tech subm ersibles are poised to explore the oceans deepest trenches and to tackle long-standing questions about exotic creatures, the source of tsunam is and the origin of life on earth . B y M ark Schrope

N E U R O S C IE N C E70 The Genetic Geography of the BrainThe first detailed m aps of w hat our genes are doing inside our brains show how very different we are from mice an d challenge a long-held theory of how our gray m atter works.B y E d Lein a n d M ike H aw rylyczC L IM A T E C H A N G E

78 False HopeThe rate at w hich global average tem pera tu re is rising has h it a plateau, b u t a clim ate crisis still loom s in our future. At best, the pause buys the w orld a few extra years to cu t carbon emissions.B y M ichael E. M an nM A T H E M A T IC S

82 The Secret Spiritual History of CalculusArchival records reveal a clash over science and religion in the early h is to ry of in tegral calculus.B y A m ir A lexander

2 Scientific American, April 2014 Photograph by Plamen Petkov 2014 Scientific American

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SCIENTIFIC AMERICAN

DEPA R T M EN TS 6 From the Editor 8 Letters

12 Science AgendaThe E ndangered Species Act is the m ost successful environm ental legislation ever enacted. B y the Editors

14 ForumBig D ata is stalking you. B y Kate Crawford

16 AdvancesStephen Hawking and a black hole mystery. Cholesterol and b reast cancer. Conflict m inerals and microprocessors. M edicine from fungi in sloth hair. Cannibal spiders.

34 The Science of HealthA nesthesia m ay have lingering effects on the brain , even years after an operation. B y Carina Storrs

36 TechnoFilesThe great debate about ne t neutrality. B y D avid Pogue

86 RecommendedThe oldest living things in the world. From the compass to GPS. Rise and fall of the atom ic era. How the hum an body creates itself. B y Clara M oskow itz

87 SkepticThe science of lyingwhy we do it. B y M ichael Sherm er

88 Anti GravityW hen it comes to the baseball sta t rage, quantification doesnt always m ake it science. B y Steve M irsky

90 50, 100 & 150 Years Ago 92 Graphic Science

Am ericans agree on global w arm ing. B y M ark FischettiO N T H E W E B

The Path to a Clean Energy FutureThe U.S. Advanced Research Projects Agency-Energy is seeking the next generation of alternative energy technology. F ind out about the progress in biofuels, hybrid solar power and energy-efficient designs being contem plated and tested.Go to www.ScientificAmerican.com/apr2014/energy

Scientific American (ISSN 0036-8733), Volume 310, Number 4 , April 2014, published monthly by Scientific American, a division of Nature America, Inc., 75 Varick Street, 9th Floor, New York, N.Y. 10013-1917. Periodicals postage paid at New York, N.Y., and at additional mailing offices. Canada Post International Publications Mail (Canadian Distribution) Sales Agreement No. 40012504. Canadian BN No. 127387652RT; TVQ1218059275 TQ0001. Publication Mail Agreement #40012504. Return undeliverable mail to Scientific American, P.O. Box 819, Stn Main, Markham, ON L3P 8A2. Individual Subscription rates: 1 year $39.97 (USD), Canada $49.97 (USD), International $61 (USD). Institutional Subscription rates: Schools and Public Libraries: 1 year $72 (USD), Canada $77 (USD), International $84 (USD). Businesses and Colleges/Universities: 1 year $330 (USD), Canada $335 (USD), International $342 (USD). Postmaster: Send address changes to Scientific American, Box 3187, Harlan, Iowa 51537. Reprints available: write Reprint Department, Scientific American, 75 Varick Street, 9th Floor, New York, N.Y. 10013-1917; fax: 646-563-7138; reprints@SciAm.com. Subscription inquiries: U.S. and Canada (800) 333-1199; other (515) 248-7684. Send e-mail to scacustserv@cdsfulfillment.com. Printed in U .S.A. / f W jPCopyright 2014 by Scientific American, a division of Nature America, Inc. All rights reserved. K

4 Scientific American, April 2014 2014 Scientific American

Scientists have been searching for a cure for cancer for decades. But now synthetic biologists from Boston University are showing the world that maybe it's not a matter of discovery, but creation. With genetic modifications, human bacteria may be modified to have the ability to kill cancer cells. It's approaching age-old problems in new ways like this that has made Boston University one of today's leading centers for discovery and knowledge. And why thinking differently about our world begins with BU. Find out more at bu.edu/discover/cure

The world needs to know.

BOSTONU N I V E R S I T Y

From the Editor

O u t o f D a rk n e ssA b o u t 13.8 b i l l i o n y e a r s a g o , j u s t 400,000 y e a r s o r so

after the big bang, the universe abruptly w ent dark, w rites science jo u rn a list M ichael D. Lemonick in this issues cover story, The F irst S tarlight, s tarting on page 38. So began the m ysteri

ous dark ages of the universe. W hat happen ed next has always in trigued me. How did th a t cosmic fog lift? How did the first stars flare and th en coalesce in to the galaxies we know today? A stronom ers have been gathering clues by looking at some of the oldest objects in the universe.

On our own, w atery p lanet, we have suffered from an inabil-

Mariette DiChristina is editor in chief of Scientific American.Follow her on Twitter @mdichristira

ity to thoroughly penetrate a different k ind of darkness: the w orld below the waves. It is often now said th a t we know the bo ttom of the ocean less well th an we do the surfaces of the m oon and M arsw hich anybody can enjoy via Google maps.

Today technology and privately funded ventures are com bining to engage in the first system atic exploration of the deepest ocean trenches. In April, as science w riter M ark Schrope details in Journey to the Bottom of the Sea, a new subm ersible will descend to the bo ttom of the Kerm adec Trench, at 10,000 m eters, to collect video of the landscape and its strange creatures. I t will sam ple the w ater and its sedim ents. Of course, robotic explorers are likely to play an even m ore p rom inent role, at least in the next few years. But one th ing is clear: we will finally begin to get a tru e r p ic ture of the dark depths of our ow n planet. Dive to page 60.

Were also shining a light on aspects of our own inn e r w orkings. RNA, less chem ically stable th a n our DNA genetic-infor- m ation repositories, was routinely overlooked as a m ere cellula r housekeeper, w rite staff editors C hristine G orm an an d Dina Fine M aron in The RNA Revolution, a special rep o rt starting on page 52. I t tu rn s out, however, th a t RNA has an astonishing degree of control over the behavior of DNA and proteins, as they describeenough to spaw n a m ultib illion-dollar th e ra peutics stam pede in ven ture capital and research initiatives. As w ith m ost explorations by science th a t push the boundaries of h u m an knowledge, we all s tand to benefit. H

BOARD OF ADVISERS

Leslie C. AielloPresident, Wenner-Gren Foundation for Anthropological Research

Roger BinghamCo-Founder and Director,The Science Network

G. Steven BurrillCEO, Burrill & Company

Arthur CaplanDirector, Division of Medical Ethics, Department of Population Health,NYU Langone Medical Center

George M. ChurchDirector, Center for Computational Genetics, Harvard Medical School

Rita ColwellDistinguished University Professor, University of Maryland College Park and Johns Hopkins Bloomberg School of Public Health

Drew EndyProfessor of Bioengineering,Stanford University

Ed FeltenDirector, Center for Information Technology Policy, Princeton University

Kaigham J. GabrielCorporate Vice President,Motorola Mobility, and Deputy, ATAP

Harold Skip GarnerDirector, Medical Informatics and Systems Division, and Professor, Virginia Bioinformatics Institute, Virginia Tech

Michael S. GazzanigaDirector, Sage Center for the Study of Mind, University of California, Santa Barbara

David J. GrossProfessor of Physics and Permanent Member, Kavli Institute for Theoretical Physics,University of California, Santa Barbara (Nobel Prize in Physics, 2004)

Lene Vestergaard HauMallinckrodt Professor of Physics and of Applied Physics,Harvard University

Danny HillisCo-chairman, Applied Minds, LLC

Daniel M. KammenClass of 1935 Distinguished Professor of Energy, Energy and Resources Group, and Director, Renewable and Appropriate Energy Laboratory, University of California, Berkeley

Vinod KhoslaPartner, Khosla Ventures

Christof KochCSO, Allen Institute for Brain Science

Lawrence M. KraussDirector, Origins Initiative,Arizona State University

Morten L. KringelbachDirector, Hedonia: TrygFonden Research Group, University of Oxford and University of Aarhus

Steven KyleProfessor of Applied Economics and Management, Cornell University

Robert S. LangerDavid H. Koch Institute Professor, Department of Chemical Engineering, M.I.T.

Lawrence LessigProfessor, Harvard Law School

John P. MooreProfessor of Microbiology and Immunology, Weill Medical College of Cornell University

M. Granger MorganProfessor and Head of Engineering and Public Policy,Carnegie Mellon University

Miguel NicolelisCo-director, Center for Neuroengineering, Duke University

Martin A. NowakDirector, Program for Evolutionary Dynamics, and Professor of Biology and of Mathematics, Harvard University

Robert E. PalazzoDean, University of Alabama at Birmingham College of Arts and Sciences

Carolyn PorcoLeader, Cassini Imaging Science Team, and Director, CICLOPS,Space Science Institute

Vilayanur S. RamachandranDirector, Center for Brain and Cognition, University of California, San Diego

Lisa RandallProfessor of Physics, Harvard University

Martin ReesAstronomer Royal and Professor of Cosmology and Astrophysics,Institute of Astronomy, University of Cambridge

John ReganoldRegents Professor of Soil Science and Agroecology, Washington State University

Jeffrey D. SachsDirector, The Earth Institute,Columbia University

Eugenie C. ScottChair, Advisory Council,National Center for Science Education

Terry SejnowskiProfessor and Laboratory Heac of Computational Neurobiology Laboratory, Salk Institute for Biological Studies

Michael ShermerPublisher, Skeptic magazine

Michael SnyderProfessor of Genetics, Stanford University School of Medicine

Michael E. WebberCo-director, Clean Energy Incubator, and Associate Professor,Department of Mechanical Engineering, University of Texas at Austin

Steven WeinbergDirector, Theory Research Group, Department of Physics,University of Texas at Austin (Nobel Prize in Physics, 1979)

George M. WhitesidesProfessor of Chemistry and Chemical Biology, Harvard University

Nathan WolfeDirector, Global Viral Forecasting Initiative

R. James WoolseyChairman, Foundation for the Defense of Democracies, and Venture Partner,Lux Capital Management

Anton ZeilingerProfessor of Quantum Optics,Quantum Nanophysics, Quantum Information, University of Vienna

Jonathan ZittrainProfessor of Law and of Computer Science, Harvard University

Kenn Brown Mondolithic Studios (glowing cosmos),6 S c ie n tif ic A m e ric a n , A p r i l 2014 Illustration by Nick Higgins (DiChristina) 2014 Scientific American

CITIES ARE WARMER AND MORE PLEASANT.

TREES GROW FASTER AND LEAF EARLIER.

AND THAT'S JUST THE BEGINNING OF THE BAD NEWS.

To get a real sense of how global warming is affecting our planet, we just need to look at what's happening on a much smaller scale in the cities where we live. Cities have a metabolism of their own, consuming energy in the form of fuel and resources, and producing waste including carbon dioxide. Our researchers have followed the flow of carbon dioxide through urban areas and have uncovered alarming facts about its impact on climate and vegetation. And while 70 percent of the world's carbon dioxide emissions come from cities, Boston University is one of the few leading research institutions to actively study urban ecosystems. Another example of how thinking differently about our world begins with BU. Find out more at bu.edu/discover/cities

The world needs to know.

BOSTONU N I V E R S I T Y

Letterseditors@sciam.com

December 2013

YOUR BRAIN ON GOOGLEHow Google Is Changing Your Brain, by Daniel M. W egner and A drian F. Ward, discusses studies indicating th a t the In terne t has changed the way hum ans have traditionally allocated rem em bering certa in facts to others and our sense of self.

I worry th a t the Internet-induced high cognitive self-esteemthe sense of being sm art or good at rem em beringthe authors report m ight discourage students from taking the care to patiently learn about profound concepts. Try looking up topological group or chord progression. Some of the m ost interesting subjects cant be understood w ith the touch of a button.

L a n c e W a l t n e r Colorado Springs, Colo.

W egner and W ard m ention, as evidence of a profound psychological change created by the Internet, an experim ent in which subjects rem em bered facts they typed into a com puter m uch worse if they were told th a t the com puter had saved them. But the same would have happened if subjects had w ritten facts on paper, and then some were told tha t the paper had been filed and others that it had been burned.

Guy O t t e w e l lDorset, E ngland

The authors ignored a big difference betw een asking friends and family for inform ation versus looking it up online: you

We need to get these reformers, who have never had a class of 38 students, out of education.A R T AR O N SEN VACAVILLE, CALIF.

dont usually need to w orry tha t the form er have been paid to deceive you using sophisticated m arketing or propaganda.

R. A l l e n G i l l ia mW inter Park, Fla.

DO CETACEANS SPREAD FUNGI?In Fungi on the M arch, Jennifer Frazer discusses the unexpected spread of the airborne, lung-infecting fungus Cryptococcus gattii in Canada and the Pacific N orthwest, w here it was previously unknown.

C. gattii is described as infecting porpoises as well as people and other animals. How better to aerosolize and spread a pulm onary infection than for a sick and dying porpoise to spray fungus from its blowhole just offshore? And if C. gattii infects one cetacean, could it also be infecting others?

J i m S a k l a d Baldw in, Md.

FRAZER REPLIES: According to veterin ary pathologist Stephen R averty o f the A nim a l Health Center a t British Columbias M in is try o f Agriculture, based on extrapolation fro m terrestrial anim als and fro m one case involving dolphins, i t is u n likely tha t C. gattii is spread fro m one in fected an im al to another, ju s t as hum ans cannot spread the disease to each other. Scientists suspect this m a y be because w et fo rm s o f the yeast in anim als m a y no t be infective. So fa r C. gattii has been fo u n d to infect Dalls porpoises, harbor porpoises and Pacific white-sided dolphins. Samples taken fro m killer whales roam ing between northern Vancouver Island in British Colum bia and the Puget Sound have not shown evidence o f C. gattii.

U.S. SCIENCE EDUCATIONIn Brain Exports [Forum], Harold O. Levy expresses alarm at the percentage of graduate and undergraduate degrees in

science and engineering awarded to foreign students in the U.S. He states tha t the U.S. public education system ... does not produce enough high school graduates who are qualified for college work.

The num ber of U.S. students taking Advanced Placem ent exams has increased every year since their inception, and the m ajority of students have been passing them. Last year m ore than two million students took alm ost four million AP exams. The pass rate was generally around 60 percent. I t seems th a t enough students are qualified to pursue higher education in science and technology b u t choose not to do so.

G e o r g e S c h u t t i n g e r M ou n ta in View, Calif.

As a chem istry teacher in high school, I have w atched the standards and testing increase while the breadth of the subjects narrow s because we teach only w hat is on the test. Our school district has not even taught science in elem entary schools for years because it is not tested. The m ore No Child Left Behind in truded into the school system, the less of a priority depth of un derstanding became. We need to get these reformers, who have never had a class of 38 students, out of education.

Furtherm ore, our students do not un derstand tha t education is a valuable commodity. If you w ant better schools, make education priority one at the dinner table.

A r t A r o n s e n Vacaville, Calif.

More Americans dont get Ph.D.s in engineering because it makes no economic sense. An engineer w ith a bachelors can give up, say, one years earnings to get a m asters and expect to m ake th a t back in three to four years from the higher salary An engineer giving up three to five years earnings from a m asters to get a Ph.D. can expect to make the lost income back sometim e between 20 years and never.

R i c h a r d J. W e a d e r II v ia e-mail

INSECT FACIAL RECOGNITIONIn Good with Faces, Elizabeth A. Tibbetts and A drian G. Dyer describe the ir work showing th a t insects such as paper wasps and honeybees are able to recognize individual faces of others in the ir species.

8 Scientific American, April 2014 2014 Scientific American

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Letters

Do these insects show a difference betw een the sexes in this ability?

D e n n i s W e b e r Kalamazoo, M ich.

TIBBETTS AN D DYER REPLY: There are likely to be sex differences in insect-face learning, although careful experim entation w ill be needed. Insects often vary w ith in an d between species in perceptually difficult tasks such as color d iscrim ination. Bees an d wasps are particu larly likely to have cognitive differences across the sexes because the social lives o f males a nd fem ales are so distinct. We are p la n n ing experiments to address this question.

SECULARISM AND SOCIETYIn Is God Dying? [Skeptic], Michael Sherm ers argum ent that religion is declining is short on hard and social science. Sherm er gives one point from a supposedly longitudinal study bu t asserts tim e trend results. Likewise, he surmises tha t because religions help the poor, richer nations become less religious, yet he pronounces the U.S. uber-religious. By the way, nonreligious societies have a pretty bad track record (Soviets, North Koreans, Nazis, etc.).

J. P. H a r r i s o n A tla n ta

SHERMER REPLIES: The U.S. has long been an outlier in religiosity am ong developed democracies, show ing substantia lly higher rates. Recent surveys show th a t we m a y now be sh ifting to be more in line w ith comparable countries. A s fo r the last point: N ationa l socialism was no t an atheistic regime, a n d its exterm inationist policies were clearly m otivated by hegem onic politics a nd racial hygiene, no t religion. The Soviet Union a n d the N orth Korean regime (not to m ention the Peoples Republic o f China) were a nd are officially atheistic, b u t noth ing they d id or are doing had or has religious motives.

ERRATAThe Stuff of Dreams, by G erbrand Ceder and Kristin Persson [World Changing Ideas], incorrectly spelled the nam e of Stefano Curtarolo of Duke University

Ugly Science Pays Off, by Rachel Felt- m an [Advances], refers to screwworms as worms. Screwworms are flies.

SCIENTIFIC AMERICANESTABLISHED 1845

EDITOR IN CHIEF AND SENIOR VICE PRESIDENT Mariette DiChristina

EXECUTIVE EDITORFred Guterl

M ANAGING EDITORRicki L. Rusting

M ANAGING ED ITOR, ONLINEPhilip M . Yam

DESIGN DIRECTORM ichael M rak

NEWS EDITORRobin Lloyd

SEN IOR EDITORSM ark Fischetti e n e r g y / e n v i r o n m e n t

Seth Fletcher t e c h n o l o g y Christine Gorm an b i o l o g y / m e d i c i n e

M ichael M oyer s p a c e / p h y s i c s / s p e c i a l p r o j e c t s G a ry Stix m i n d / b r a i n Kate W ong e v o l u t i o n

A SSOCIATE EDITORSDavid Biello e n e r g y / e n v i r o n m e n t Larry G reenem eier t e c h n o l o g y

Ferris Jab r m i n d / b r a i n Dina Fine Maron b i o l o g y / m e d i c i n e C lara M oskow itz s p a c e / p h y s i c s

p o d c a s t e d i t o r Steve M irsky v id e o e d i t o r Eric R. O lson

CON TRIBU TIN G EDITORSDavide Castelvecchi, Katherine Harm on Courage, Deborah Franklin,

A nna Kuchm ent, M aryn M cKenna, G eorge M usser,Christie Nicholson, John Rennie, Sarah Simpson

a r t d i r e c t o r Jason M ischka a r t d i r e c t o r , in f o r m a t io n g r a p h ic s Jen Christiansen

a r t d i r e c t o r , o n l in e Ryan Reid p h o t o g r a p h y e d i t o r M onica Bradley

p h o t o r e s e a r c h e r Liz Tormes a s s o c ia t e a r t d i r e c t o r , ip a d Jason A rias a s s i s t a n t a r t d i r e c t o r , ip a d Bernard Lee

m a n a g in g p r o d u c t io n e d it o r Richard Hunt s e n io r p r o d u c t io n e d i t o r M ichelle W right

in f o r m a t io n g r a p h ic s c o n s u l t a n t Bryan Christie a r t c o n t r ib u t o r s Edward Bell, Law rence R. Gendron, N ick Higgins

c o p y d i r e c t o r M aria-Christina Keller s e n io r c o p y e d it o r D aniel C . Schlenoff

c o p y e d it o r s M ichael Battaglia, Aaron Shattuck

s e n io r e d i t o r i a l p r o d u c t m a n a g e r A ngela Cesaro w e b p r o d u c t io n e d i t o r Kerrissa lynch

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Science Agenda by the EditorsOpinion and analysis from Scientific Americans Board of Editors

Preserve the Endangered Species ActThe most successful environmental legislation ever enacted faces new threats from CongressA century ago an iconic, keystone speciesthe gray wolfall bu t vanished from the continental U.S. Its loss was no accident. Rather it was the result of an eradication cam paign m ounted by ranchers and the governm ent to protect livestock. H unters shot, trapped or poisoned the wolves and received a bounty for each kill. Not even the national parks, such as Yellowstone, offered safe haven. W ithin decades the apex predator was nearly gone, a decline th a t triggered a cascade of changes dow n the food chain.

Today, however, in the 28,000-square-mile w ilderness of the G reater Yellowstone Ecosystem, 400 gray wolves roam free. The Yellowstone wolves are am ong the 6,000 or so gray wolves tha t now inhabit the lower 48 states thanks to the Endangered Species Act (ESA). The act was signed in to law in 1973 to protect endangered and threatened plants and animals, as well as the habitats critical to their survival. The ESA has prevented the extinction of 99 percent of the 2,000 listed species. It is widely considered the strongest piece of conservation legislation ever im plem ented in the U.S. and perhaps the world.

Yet for years the ESA has endured attacks from politicians who charge th a t it is economically dam aging and ineffectual. Opponents argue tha t environm ental groups use the legislation to file frivolous lawsuits aim ed at blocking development. Moreover, they contend tha t the ESA fails to aid species recovery. As evidence, they note tha t only 1 percent of the species th a t have landed on the protected list have recovered to the poin t where they could be delisted.

The latest assault comes in the form of the Endangered Species M anagem ent Self-Determination Act, a bill introduced by senators Rand Paul of Kentucky and Dean Heller of Nevada and Representative M ark Amodei of Nevada. The bill would, among other things, require state and congressional approval to add new species to the protected listthe U.S. Fish and Wildlife Service and the National M arine Fisheries Service do this now, based on the best scientific data available. It would also automatically delist species after five years and allow governors to decide if and how their states follow ESA regulations.

Senator Paul and others advocating for reform say tha t they w ant to improve the law to better serve im periled species and

local people. But their argum ents are flawed. The reason why few species have recovered to the point where they can be delisted is no t because the ESA is ineffective bu t because species take decades to rebound. In fact, 90 percent of the listed species are on track to m eet the ir recovery goals.

In addition, lawsuits filed by environm ental groups have led to m any of the ESAs accomplishm ents. The ESA m ay require a developm ent project to m ake m odifications to address concerns about listed species, bu t the benefit of the ESA to ecosystems outweighs this inconvenience to developers. The changes critics are lobbying for, while undoubtedly appealing to groups such as farm ers and loggers, would cripple the ESA.

Yet the flaws of this bill do not m ean the ESA cannot be im proved on. For example, Congress should help the private landowners who choose to act as stewards of their land. According to the Fish and Wildlife Service, about ha lf of ESA-listed species have at least 80 percent of their hab itat on private lands. Yet landowners have few incentives to preserve the habitats of threatened species. More financial and technical assistance needs to be made available to landowners who w ant to help protect the species on the ir property, as well as to people such as ranchers whose herds m ay be affected by the re tu rn of a species like the gray wolf.

Perhaps m ost im portant, conservation efforts m ust be updated to reflect w hat scientists now know about climate change and the threats it poses to wildlife. As tem peratures rise, many more species will fall on ha rd times. Policy m akers should thus increase ESA funding to allow more rigorous m onitoring of wildlife and to protect more species.

Against the backdrop of budget cuts, setting aside m ore m oney to save anim als and plants m ight seem like a luxury. Nothing could be further from the tru th . Healthy ecosystems provide a w ealth of essential services to hum ansfrom purifying w ater to supplying food. We m ust preserve them for our own well-being and th a t of future generations. B

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12 Scientific American, April 2014 2014 Scientific American

Illustration by Ross MacDonald

Photonics rewritesour understanding of matter.Have you ever admired the lovely, iridescent light that glows from an opal, or watched a jewel beetle from different angles and seen how the colors change? These mysterious colors are created by something called photonic crystals, which make use of the interaction between light and matter. Photonic crystals are nanostructures that can be made to strongly reflect or close out light at certain wavelengths, by tweaking their structure. The application of these crystals could lead to fascinating possibilities in new optical devices. Photonics technologies are rewriting the way we look at and understand matter, with each discovery adding another hue to the spectrum.

Akira HirCfffafrwPresident and CEO, Hamamatsu Photonics K.K.

HAMAMATSU PHOTONICS K.K.325-6, Sunayama-cho, Naka-ku, Hamamatsu City, Shizuoka Pref., 430-8587, Japan Telephone:(81)53-452-2141, Fax:(81)53-456-7889 www.hamamatsu.com

Forum by Kate CrawfordCommentary on science in the news from the experts Kate Crawford is a principal researcher

at Microsoft Research, a visiting professor at the Massachusetts Institute of Technology Center for Civic Media and a senior fellow at New York Universitys Information Law Institute.

Big Data StalkingData brokers cannot be trusted to regulate themselves

Many of us now expect our online activities to be recorded and analyzed, b u t we assum e th a t the physical spaces we inhabit are different. The data-broker industry does no t see it th a t way. To it, even the act of w alking dow n the street is a legitim ate da ta set to be captured, catalogued and exploited. This slippage betw een the digital and physical m atters no t only because of privacy concernsit also raises serious questions about ethics and power.

The Wall Street Journal recently published an article about Turnstyle, a com pany th a t has placed hundreds of sensors throughout businesses in dow ntow n Toronto to gather signals from sm artphones as they search for open Wi-Fi networks. The signals are used to uniquely identify phones as they move from street to street, caf to cinema, w ork to hom e. The owner of the phone need not connect to any Wi-Fi netw ork to be tracked; the entire process occurs w ithout the knowledge of m ost phone users. Turnstyle anonymizes the data and tu rns them in to reports tha t it sells back to businesses to help them understand the custom er and better tailor their offers.

Prom inent voices in the public and private sectors are currently prom oting boundless da ta collection as a way of m inim izing threats and maximizing business opportunities. Yet this trend may have unpleasant consequences. Mike Seay, an OfficeMax customer, recently received a letter from the com pany tha t had the words Daughter Killed in Car Crash following his name. He had not shared this inform ation w ith OfficeMax. The company stated

th a t it was an error caused by a m ailing list rented through a third-party provider.

Clearly, this was a mistake, bu t it was a revealing one. W hy was OfficeMax harvesting details about the death of someones child in the first place? W hat limits, if any, will businesses set w ith our data if this was deem ed fair game? OfficeMax has not explained why it bought the m ailing list or how m uch personal data it contains, b u t we know th a t third-party data brokers sell all m anner of inform ation to businessesincluding, as Pam Dixon, executive director of the W orld Privacy Forum, testified before the U.S. Senate last December, police officers hom e addresses, rape sufferers..., genetic disease sufferers, as well as suspected alcoholics and cancer and HIV/AIDS patients.

In the absence of regulation, there have been some attem pts to generate an industry code of practice for location-technology companies. One proposal would have companies de-identify personal data, lim it the am ount of tim e they are retained, and prevent them from being used for employment, health care or insurance purposes. But the code would only require opt-out consentthat is, giving your details to a central Web site to indicate tha t you do not w ant to be trackedw hen the inform ation is not personal.

The trouble is, alm ost everything is personal. Any inform ation tha t distinguishes one person from another can be used for re- identifying anonymous data, wrote com puter scientists Arvind Narayanan, now at Princeton University, and Vitaly Shmatikov of the University of Texas at Austin in a 2010 article in Communications o f the ACM. This includes anonymous reviews of products, search queries, anonymized cell-phone data and commercial transactions. The opt-out-via-our-Web-site model also compels custom ers to volunteer yet more inform ation to marketers. And it is not clear th a t self-regulation will ever be sufficient. Most industry models of privacy assume that individuals should act like businesses, trading their inform ation for the best price in a frictionless m arket where everyone understands how the technology works and the possible ramifications of sharing their data. But these models do not reflect the reality of the deeply unequal situation we now face. Those who wield the tools of data tracking and analytics have far more power th an those who do not.

A narrow focus on individual responsibility is not enough: the problem is systemic. We are now faced w ith large-scale experim ents on city streets in which people are in a state of forced participation, w ithout any real ability to negotiate the term s and often w ithout the knowledge tha t their data are being collected. ffl

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14 Scientific American, April 2014 2014 Scientific American

Illustration by Skip Sterling

P h y s ic s a n d O u r U n i v e r s e : H o w I t A l l W o r k sTaught by Professor Richard WolfsonMIDDLEBURY COLLEGE

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Electromagnetic Induction38. Magnetic Energy39. AC/DC40. Electromagnetic Waves41. Reflection and Refraction42. Imaging43. Wave Optics44. Cracks in the

Classical Picture45. Earth, Ether, Light46. Special Relativity47. Time and Space48. Space-Time and

Mass-Energy49. General Relativity50. Introducing the Quantum51. Atomic Quandaries52. Wave or Particle?53. Quantum Mechanics54. Atoms55. Molecules and Solids56. The Atomic Nucleus57. Energy from the Nucleus58. The Particle Zoo59. An Evolving Universe60. Humble PhysicsWhat

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The New Black Hole BattleA decades-old paradox returns

When Stephen Hawking was quoted earlier this year as saying that there are no black holes, he wasn't really talking about black holes. At least not about black holes as you or I imagine themastrophysical objects that suck in everything, even light. Those, everyone agrees, are just as black as ever.

Hawking's quip instead concerns black holes in a highly theoretical sense. Like many other theorists,Hawking has been trying to understand a paradox eating at the heart of physics. The issueoften referred to as the black hole firewall paradoximplies that physicists might have to abandon (or deeply modify) quantum mechanics or Einstein's general theory of relativity, or both.

The firewall problem is related to a paradox that Hawking first pointed out in the 1970s. It concerns this question: What happens to information that falls into a black hole? The rules of quantum mechanics require that information can never be lost. Even burning a book doesn't destroy the information insideit just scrambles it up. But black holes do seem to destroy information, sucking it past the event horizon, a point of no return.

The black hole information paradox stumped physicists for two decades. It appeared to be solved in the late 1990s, when researchers figured out that information could leak out of a black hole in the form of Hawking radiation. Then, in 2012, physicists at the University of California, Santa Barbara, found flaws in the previous solutions.They concluded that an event horizon is not, as previously thought, an ordinary place. Instead it is a wall of fire that prevents Hawking radiation on the outside from remaining intertwined on a quantum level with material inside.

Hawking's latest work is an attempt to offer an alternative solution. He proposes that a black hole has an apparent horizon in addition to its event horizon. The two are nearly always identical. Information can rise from inside the black hole to the apparent horizon. At that point, quantum effects can blur the boundary between the apparent and event horizons, sometimes allowing information to escape. Hence, black holes would not be strictly black, provided you had hundreds of trillions of years to watch them. But ultimately, what Hawking's paper means is that there is something fundamental about black holes we still do not understand. Michael Moyer

16 Scientific American, April 2014 FURTHER READINGS AND CITATIONS ScientificAmerican.com/apr2014/advances 2014 Scientific American

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Cancer Culprit?A common product of cholesterol may fuel breast tumor growth

Scientists have long struggled to u nd erstand why w om en w ith h e a rt disease risk factors are m ore likely to develop b reast cancer. Now research suggests th a t high cholesterol m ay play an im portan t role.

Estrogen drives the m ajority of breast cancers in women. The horm one binds to proteins know n as receptors inside the tum or, help ing it grow. So w hen Philip Shaul, a ped iatric ian and biologist at the University of Texas Southw estern M edical Center, and his colleagues lea rned th a t a com m on breakdow n p roduct of cholesterol also activates estrogen receptors, they though t they m ight be on to som ething. Team ing up w ith Duke University cancer biologist D onald M cDonnell, they showed in 2008 th a t the cholesterol product, know n as 27HC, spurs tum or grow th in hum an b reast cancer cells.

B uilding on the ir work, Shaul and M cDonnell showed, in independent studies published in Novem ber 2013 in Cell Reports and Science, respectively, th a t 27HC drives cancer grow th in mice harbo rin g estrogen receptor-positive h um an breast tum ors. Using samples from patien ts a t his hospital, Shaul also found th a t 27HC levels w ere th ree times h igher in the healthy b reast tissue of w om en w ith b reast cancer com pared

w ith th a t of cancer-free wom en; 27HC levels w ere 2.3 tim es h igh er still in tum or cells. Furtherm ore, cancer patients w ho had low er levels of an enzyme th a t breaks dow n 27HC in tum ors w ere less likely to survive. W hen M cDonnells team fed m ice high-choles- terol or high-fat diets, they w ere m ore likely th a n anim als w ith norm al diets to develop b reast cancer, too. The two papers b ring 27HC to the lim elight of b reast cancer research , says Sergio Dias, a biologist at the In stitu te of M olecular M edicine in Lisbon.

It is still unclear, however, how blood cholesterol levels m ight affect breast cancer risk because Shaul found no consistent link betw een 27HC levels in h u m an tum ors and blood cholesterol levels. But there m ay be subsets of w om en with high cholesterol at greater risk, he says.

The findings could have im portant treatm ent implications. They bolster the idea, backed already by one study, that cholesterol-lowering statin drugs may slow the progression of some breast cancers. And because between 30 and 65 percent of wom en w ith estrogen-fueled breast cancers do not respond to drugs that thw art estrogen production, the studies suggest tha t in some wom en theres simply an entirely different driver of the cancer, Shaul says. M elinda Wenner M oyer

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BEFORE YOU START VIAGRA Tell your doctor if you have or ever had: Heart attack, abnormal heartbeats, or stroke Heart problems, such as heart failure, chest pain, angina, or aortic valve narrowing Low or high blood pressure Severe vision loss An eye condition called retinitis pigmentosa Kidney or liver problems Blood problems, such as sickle cell anemia or leukemia A deformed penis, Peyronies disease, or an erection that lasted

more than 4 hours Stomach ulcers or any kind of bleeding problemsTell your doctor about all your medicines. Include over-the-countermedicines, vitamins, and herbal products. Tell your doctor if youtake or use: Medicines called alpha-blockers to treat high blood pressure or

prostate problems. Your blood pressure could suddenly get too low. You could get dizzy or faint. Your doctor may start you on a lower dose of VIAGRA. Medicines called protease inhibitors for HIV. Your doctor may prescribe a 25 mg dose. Your doctor may limit VIAGRA to 25 mg in a 48-hour period. Other methods to cause erections. These include pills, injections, implants, or pumps. A medicine called REVATIO. VIAGRA should not be used with REVATIO as REVATIO contains sildenafil, the same medicine found in VIAGRA.

POSSIBLE SIDE EFFECTS OF VIAGRASide effects are mostly mild to moderate. They usually go away after a few hours. Some of these are more likely to happen with higher doses.The most common side effects are: Headache Feeling flushed Upset stomach Less common side effects are: Trouble telling blue and green apart or seeing a blue tinge on things Eyes being more sensitive to light Blurred vision Rarely, a small number of men taking VIAGRA have reported these serious events: Having an erection that lasts more than 4 hours. If the erection is

not treated right away, long-term loss of potency could occur. Sudden decrease or loss of sight in one or both eyes. We do not know if these events are caused by VIAGRA and medicines like it or caused by other factors. They may be caused by conditions

like high blood pressure or diabetes. If you have sudden vision changes, stop using VIAGRA and all medicines like it. Call your doctor right away. Sudden decrease or loss of hearing. We do not know if these events are caused by VIAGRA and medicines like it or caused

by other factors. If you have sudden hearing changes, stop using VIAGRA and all medicines like it. Call your doctor right away. Heart attack, stroke, irregular heartbeats, and death. We do not know whether these events are caused by VIAGRA or caused

by other factors. Most of these happened in men who already had heart problems.If you have any of these problems, stop VIAGRA. Call your doctor right away.

HOW TO TAKE VIAGRADo: Take VIAGRA only the way your doctor tells you. VIAGRA comes in 25 mg, 50 mg, and 100 mg tablets. Your doctor will

tell you how much to take. If you are over 65 or have serious liver or kidney problems,

your doctor may start you at the lowest dose (25 mg). Take VIAGRA about 1 hour before you want to have sex. VIAGRA starts to work in about 30 minutes when you are sexually excited. VIAGRA lasts up to 4 hours.Dont: Do not take VIAGRA more than once a day. Do not take more VIAGRA than your doctor tells you.If you think you need more VIAGRA, talk with your doctor. Do not start or stop any other medicines before checking with

your doctor.

NEED MORE INFORMATION? This is only a summary of important information. Ask your doctor or pharmacist for complete product information OR Go to www.viagra.com or call (888) 4-VIAGRA (484-2472).

c=> Pfizer Helpful Answers'"j' Filling a need for prescription assistance

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Cockroach HomecomingOnce thought to be invasive, a bug reveals its American roots

In 1951 scientists though t they had found a new invader on A m erican soil. Ectobius, a cockroach found throughout Europe and Africa, h ad begun tu rn ing up in hom es in M assachusetts. Three decades la te r an o ther Ectobius species, com m only know n as the dusky cockroach, m ade an appearance in New H am pshire an d then in Vermont. Eventually four Ectobius species were being tallied in the n o rtheaste rn U.S.

But Ectobius, it tu rns out, is no t really a stranger to N orth Am erica at all. It has ju s t re tu rn ed hom e after an absence of 49 m illion years.

Entom ologists got the m istaken im pression th a t Ectobius was an Old W orld species back in 1856, w hen they found the first specimens in 44-million- year-old Baltic amber. Thats how the m atter sat for m ore than 150 years. Then, in 2010, Conrad Labandeira, a research scientist and curator of fossil arthropods at the Sm ithsonian National Museum of Natural History, invited Peter Vrsansky a cockroach specialist at the Slovak Academy of Sciences, to examine some fossils tha t had been gathering dust for years in the Sm ithsonian Institutions collection. They had been taken from the Green River Formation in Colorado. Lo and behold, [Vrsansky] said, This is Ecto- bius! Labandeira recalls.

The 21 fossils had revealed four species of Ectobius dating back to the Eocenepredating the E uropean specimens by some five m illion years. I ts

amazing, Labandeira says, how one little discovery can change the entire understanding of the history of this particular lineage of cockroaches.

Most likely, Ectobius w ent extinct in N orth Am erica as a result of increasingly h arsh conditions as the glaciers crept

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south. W hen tha t extinction occurred, exactly, is unknow n, bu t before it h ap pened, Labandeira says, some of the insects m ade a b reak for Europe, either traveling through Greenland or else scuttling across the Bering land bridge.

Recently announcing the news in the A n na ls o f the Entom ological Society o f Am erica, L abandeira and Vrsansky nam ed one of the new cockroaches Ectobius ko h lsia h a t tip to the fossils original discoverer, David Kohls, an am ateur collector in Colorado who has am assed hundreds of thousands of fossil insects. The th ree o ther new Ectobius species, though prelim inarily identified, did no t possess enough detail for the researchers to nam e them.

There are so m any am azing, beautiful fossils, and so few people have had the chance to work on them , says Dena Sm ith, an associate professor of geological sciences at the University of Colorado Boulder. I th in k there will be a lo t m ore of th is k ind of exciting w orkto come. Rachel N uw er

April 2014, ScientiflcAmerican.com 21 2014 Scientific American

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Hobby Lobby'sowner claims that, because of his religious beliefs, his corporation may deny women workers contraceptive insurance coverage, in defiance of US healthcare law.What's next? Jehovah's Witnesses denying workers insurance coverage for blood transfusions?RELIGIOUS DOGMA MUST NOT DICTATE HEALTHCARE.

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War Funding Inside?Intel and other tech companies crack down on conflict minerals

It is hard to believe th a t our m undane social m edia ban ter could have an im pact on the civil w ar th a t has been raging in the Democratic Republic of the Congo for m ore th an a decade. The problem is not the content of these messages; it is the devices used to send them. Smartphones, tablets, PCs and other gadgets often have electronic com ponents m ade from so- called conflict m ineralsgold, tantalum , tin and tungstentaken from specific

mines in the D.R.C. th a t give a cut of their profits to arm ed groups.

Chipmaker Intel used the Consumer Electronic Associations International CES trade show in January to spotlight this problem and declare tha t its microprocessors are now free of conflict minerals. The company says it has taken steps to have its suppliersin particular, the smelters that extract metals from m ined oreaudited by third-party companies and to certify that they are not cooperating w ith extortion efforts tha t funnel money to local warlords.

The idea of conflict minerals was relatively obscure four years ago, w hen the

Enough Project, a W ashington, D.C.- based nongovernm ental organization, brought the issue to Intels attention. Intels w ork has encouraged other companies to examine the sources of their products raw m aterials, Enough Project senior policy analyst Sasha Lezhnev said at the International CES.

Tech com panies do no t use as m uch of these m inerals as o ther industries, such as jew elry m akers. Yet gold, tan ta

lum , tung sten and tin play an im po rtan t role in our gadgets. Like m any device m anufactu rers, In tel relies on highly conductive gold in circuit cards, connectors and sem iconductor packaging. The com pany uses tan ta lu m in some of its capacitors and in the sputtering deposition process used to m ake its sem iconductors. Tungsten also plays a lim ited role in the sem iconductor fabrication process. Tin, m ean

while, is a key com ponent in the silver- tin solder th a t attaches electronic com ponents to the ir circuit boards.

Soon all companies will have to scrutinize their supply chains. In August 2012 the Securities and Exchange Commission began requiring firms to annually disclose the sources of the gold, tin, tungsten and tan talum used in their products. The U.S. Chamber of Commerce and the National Association of M anufacturers have filed a law suit against the sec in response to its new rules, b u t companies will still have to get the ir first disclosure reports to the agency by May 31. Larry Greenemeier

B Y T H E N U M B E R S

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developed by researchers at the National Institute of Standards and Technology and the University of Colorado Boulder, could tick away without gaining or losing one second.FFRF.ORG/reasonmustprevail

FFRF is a 501(c)(3) educational charity

2 2 Scientific American, April 2014 2014 Scientific American

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YOUR HEALTH HIJACKEDCan we trust a test that is almost 80% false-positive?

From the scientist who first discovered the prostate-specific antigen (PSA) comes the shocking story o f how a multi-billion dollar industry rose out o f a widely-accepted test that has disastrous consequences.

Boldly exposes the profit, politics and fraud behind PSA screening, and the serious harm done to countless men.Ih is is a must-read for e v e ry man, and the women who care about them. MARGARET I. CUOMO, M.D., AUTHOR OF A WORLD WITHOUT CANCER

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FuzzyDiscoveryResearchers find potential cures on the backs of sloths

Treatments for human diseases often come from unexpected places. Several years ago microbiologist Sarah Higginbotham was talking with an ecologist colleague about how she looks for bioactive organisms those that produce substances that inhibit the growth of other organisms. When I told him I look for places where lots of organisms live together, he said, Sloths sound perfect, she says.

Sloths are microbial jackpots because they move so slowly and infrequently and because their fur contains microscopic grooves that create a perfect breeding ground for algae, fungi, bacteria, cockroaches and caterpillars.

Interest piqued, Higginbotham, during

j

a temporaiy research stay at the Smithsonian Tropical Research Institute in Panama, obtained hair samples from nine three-toed slothsthe famously sedentaiy, tree-dwelling mammals from Central and South America. From the samples, she identified 28 different fungal strains, several of which might represent new species. (Chemical testing could help determine whether they are in fact new species.) Higginbotham, now at Queens U niversity Belfast, and her colleagues published a paper in PLOS ONE confirming bioactivhy in some of their fungal strains against the parasites that cause malaria and Chagas disease, a breast cancer cell line and several types of harmful bacteria. I n all, they discovered two dozen drug leads hiding in the fur of sloths. Rachel Nuwer

ADDICTION IS HOPELESS WITHOUT YOUShare your story of recovery or message of hope with someone who needs to hear it. Visit drugfree.org and join The Hope Share.

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Illustrations by Thomas Fuchs 2014 Scientific American

April 2014, ScientificAmerican.com 23

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Love Him or Eat Him?Some female wolf spiders prioritize food over sex

Spider courtship is a risky business. In some species, females routinely decide th a t they would rather eat a male than m ate with him , and researchers have struggled for decades to understand why. A recent experim ent w ith a type of Spanish wolf spider suggests th a t the reason m ay depend on the spiders personality.

A virgin spider cannot be sure how m any chances she will have to mate.Every male could be her last, and if she eats all of them , she will never reproduce. W hy would a spider take this risk? One possibility is th a t females are choosy, holding out for large, healthy males with good genes and devouring the rest. Another possibility is the aggressive spillover hypothesis, which suggests th a t some females have strong predatory instincts th a t spill over into aggression toward potential mates. These females m ight eat males even w hen they would be better off m ating w ith them.

To learn more about cannibalistic spiders, researchers at the Experimental Station of Arid Zones in Spain and their colleagues caught 80 juvenile females of the

species Lycosa hispanicaa type of wolf spiderand fed them as m uch as they w anted while they m atured. Some females p u t on weight more quickly than others. Since all females had sim ilar prey availability, we estim ated th a t female growth rate would be the result of female voraciousness, says Rubn Rabaneda- Bueno, the studys lead author.

After each female m olted to adulthood, the researchers placed a male in her enclosure. Females th a t ate their suitors were offered additional chances w ith new males. Most of the cannibal females were choosy. They ate males tha t were in poor condition and m ated w ith males that were of high quality. But we found that there were a few females tha t would consistently get a male and kill it and get another male and kill itso they were really aggressive, says Jordi Moya-Lara- o, the studys senior author.

The m ost aggressive females killed big, healthy males as often as they killed scrawny ones. The same females also had the highest growth rates, indicating that they were the m ost aggressive toward prey. In this study, a female personality tra ither voracity tow ard preywas correlated w ith her aggressiveness toward males, Rabaneda-Bueno says. Our results provide evidence th a t different female personalities can lead to different outcomes in the interactions between males and females in a sexual cannibal.

N ala Rogers

2 4 Scientific American, April 2014 ScientificAmerican.com/apr2014 2014 Scientific American

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Where Farmers and Birds AgreeSome species adapt well to no-till fields

As grassland has m orphed into farm land across the Am erican M idwest, wildlife diversity and abundance have declined. But for some birds things m ight no t be so grim. Some grassland species appear to have adapted particularly well to no-till soybean fields, according to research published in M arch in the journal Agriculture, Ecosystems, a nd Environm ent.

Tilling is a process in which farm ers rem ove weeds and loosen soil before seeding the ground, but no-till farm ing eschews th a t prac-

tice. D etritus from the previous seasons harvest is left covering the ground, w here it provides a nice foundation for nesting birds.

T hat birds were m ore likely to nest in no-till fields than in tilled ones was no t terribly surprising. R ather it was the extent th a t birds used no-till [fields], the species of birds we found nesting, and their nest success relative to w hat we consider quality habitat, says Kelly R. VanBeek, who conducted the study for a m asters thesis a t the University of Illinois at Urbana-Champaign.

Jam es Herkert, director of the Office of Resource Conservation at the Illinois D epartm en t of N atural Resources, was also surprised by the species diversity in no-till fields, including several th a t are of conservation in te rest such as eastern meadow lark, dickcissel [and] up lan d sandpiper. Am erican robin nests were the m ost com m on found in bo th field types, w hich was also

unexpected because robins tend to prefer nesting in trees and shrubs.I t shows ju s t how adaptable they are, he says.

N est loss was high in both types of fields, though. The birds whose nests were destroyed by m achinery would have been spared if planting w ere delayed until June 1. But in the past 10 years farm ers have planted, on average, 66 percent of soybeans by May 30, in pa rt because soybeans have better yields if p lanted earlier.

The conflicting needs of farm ers and wildlife m ake finding win-win solutions challenging, Herkert says. Still, the researchers suggest th a t ra ther th an buying small tracts of land to set aside as wildlife reserves, conservationists should w ork w ith farm ers to im plem ent m ore ecologically sustainable stra tegies, such as no-till farming.

Jason G. Goldman

26 Scientific American, April 2014 2014 Scientific American

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Solar Times TwoA hybrid approach combines the benefits of photovoltaic and solar-thermal technologies into a device the size of a fingernail

The two most common ways of generating power from the sun both have their drawbacks. Photovoltaic cells, which absorb photons from sunlight and convert them to electricity, operate with only 20 percent efficiency. That is because they can use only photons within a certain range of wavelengths to excite electrons. Solarthermal systems, which turn sunlight into heat and then into electricity, are more efficient than photovoltaicsbecause they can use the entire solar spectrum, they can reach efficiencies of 30 percent but they are impossible to scale down to rooftop size. The usual solar-thermal setup involves vast mirror arrays that concentrate sunlight, heating liquid that eventually powers an electricity-generating turbine.

To overcome the limitations of the two approaches, researchers at the Massachusetts Institute of Technology have created a device that combines elements of both, which they described in a February study in Nature Nanotechnology. (ScientificAmerican is part of Nature Publishing Group.)

Their fingernail-size invention is known as a solar-thermophotovoltaic device. The first thing

it does is produce heat from sunlight. Carbon nanotubesextremely efficient absorbers of sunlight, which convert nearly the entire solar spectrum into heattake care of that step. The heat then flows into a photonic crystal, which is composed of layers of silicon and silicon dioxide. Once the photonic crystal reaches approximately 1,000 degrees Celsius, it begins to glow, emitting mostly photons of a wavelength well matched to the photovoltaic cell below. When those photons strike the photovoltaic cell, they generate electricity.

The process of transforming light into heat and then back into lightand, finally, into elec- tricityis not simple. So far the thermophoto- voltaic device has achieved only 3 percent efficiency. But this is just a starting point, says senior author Evelyn Wang. The key will be making it work on a larger scale. If we can scale up, then we can get over 20 percent efficiencies, Wang says. Geoffrey Giller

2014 S cien tific A m erican

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W A R FA R E

When Cars FlyMilitary Transformer vehicles move closer to takeoffThe idea of a car taking off like a helicopter sounds like science fiction. But four years after the Pentagon funded its vision for a Transform er m ilitary flying m achine, the project has found solid footing. Two prototype designs, one by aerospace and defense giant Lockheed M artin and one by aerospace start-up Advanced Tactics, offer possible paths for the au tom ated flying car to become a reality on future battlefields ruled by robots.

A flying car or similar vehicle could be useful in inserting U.S. Navy SEALs into enemy territory, evacuating w ounded soldiers from urban locations inaccessible to helicopters or resupplying spread-out military units. The U.S. Defense Advanced Research Projects Agency also w anted a vehicle th a t an ordinary soldier could operate w ithout pilot train inga crucial specification th a t highlights the need for

an autonom ous brain similar to those th a t m ay one day operate battlefield drones and robots.

d a r pa recently gave the go-ahead for Lockheed M artin to build and fly a Transform er prototype, now know