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How Things Work
Introduction From the touch screens we use at ATMs to the treatments that keep our canine companions flea-free, we often take for granted the science behind everyday technologies.

In this exclusive online issue, Scientific American editor Mark Fischetti explains the inner workings of 20 commonly used technologies. Learn how noise-cancelling headphones silence unwanted background noise and how digital cameras overcome shaky hands. Discover how crude oil is refined and how cochlear implants enable hearing. You'll also find out how radar guns spot speeders, how air traffic control systems minimize accidents in the sky, and how medical patches enable continuous drug delivery.

Steady Cam Image stabilization in digital cameras (originally published October 2006)
Carbon Hooch The sophisticated chemistry of refining crude (originally published June 2006)
Cutting Work How a robot can mow your lawn (originally published May 2006)
Into the Breach How levees hold back rivers (originally published February 2006)
Case Cracked Nuts to you! (originally published November 2005)
Make It Quick Presto! Rapid prototyping (originally published July 2005)
Reducing a Roar How new headphones cancel out unwanted background noise (originally published February 2005)
Crowded Skies How new headphones cancel out unwanted background noise (originally published December 2004)
Keep the Beat How pacemakers keep the beat (originally published November 2004)
Shock Absorbed Making cities earthquake-proof (originally published October 2004)
Clear Favorite Lasik and other laser eye surgeries (originally published May 2004)
Staying Power Seriously, how do nails hold things together? (originally published November 2003)
On the Money How machines recognize dead presidents (originally published September 2003)
To Hear Again Bypassing the ear with implants (originally published June 2003)
Potent Patches Patches that deliver drugs (originally published April 2003)
Current Safety Ground fault circuit interrupters (originally published November 2001)
Flea Treatments Fleas flee from new "spot" treatments used on pets (originally published September 2001)
Tan or Burn Protecting skin from the summer sun (originally published July 2001)
At Your Fingertips A truly touchy interface (originally published April 2001)
Gotcha! How radar guns catch speeders (originally published March 2001)
Uncommon Genius
Introduction Millions of years of evolution have endowed Homo sapiens with remarkable intellect. But not all human brains are created equal. From the great powers of memory seen in savants to the skills of chess grandmasters, unusual talents can offer a unique window on how the mind works. This exclusive online issue examines genius in some of its most intriguing forms.

Meet Kim Peek, whose abilities provided the inspiration for the character Raymond Babbit in the movie Rain Man. Peek's severe developmental disabilities prevent him from managing the chores of daily life, but he has learned 9,000 books by heart so far, among other astonishing feats of memory. Other savants have musical or artistic talents.

Less well known than savant syndrome is Williams syndrome, a disorder in which affected individuals generally score below average on standard IQ tests, but often possess startling language and music skills, as another article in this issue describes. Mood disorders, too, have been linked to genius: it seems that manic-depressive illness and major depression can enhance creativity in some people.

Other articles focus on gifted children. These youngsters fascinate with their precocious intellect, but they often suffer ridicule and neglect. They also tend to be keenly aware of the potential risk of failure, which can prove emotionally paralyzing for them. Studies of such children have provided key insights into brain development--and revealed how best to nurture their extraordinary minds.

Our final article in the issue considers whether some geniuses are made, not born. Dissections of the mental processes of chess grandmasters have shown that their skills arise from years of "effortful study"--continually tackling challenges that lie just beyond their competence. Could comparable training turn any one of us into such an expert? Food for thought.

Islands of Genius Artistic brilliance and a dazzling memory can sometimes accompany autism and other developmental disorders (originally published in Scientific American Mind, January 2004)
Inside the Mind of a Savant Kim Peek possesses one of the most extraordinary memories ever recorded. Until we can explain his abilities, we cannot pretend to understand human cognition (originally published December 2005)
Williams Syndrome and the Brain To gain fresh insights into how the brain is organized, investigators are turning to a little known disorder (originally published December 1997)
Manic-Depressive Illness and Creativity Does some fine madness plague great artists? Several studies now show that creativity and mood disorders are linked (originally published in Mysteries of the Mind)
Uncommon Talents: Gifted Children, Prodigies and Savants Possessing abilities well beyond their years, gifted children inspire admiration, but they also suffer ridicule, neglect and misunderstanding (originally published in Exploring Intelligence)
Watching Prodigies for the Dark Side Gifted children who are not challenged can quickly grow bored with school, but a hidden fear of failure can lead to far greater problems (originally published Scientific American Mind, April 2005)
The Expert Mind The mental processes of chess grandmasters are unlike those of novices, a fact that illuminates the development of expertise in other fields (originally published August 2006)
21st Century Medicine
Introduction The 18th century witnessed the birth of a vaccine for smallpox; the 19th century ushered in the advent of aspirin; penicillin and the pill transformed the medical landscape of the 20th century. What will the history books regard as the medical milestones of the 21st century? It's too soon to say. But already a number of potentially revolutionary treatments have emerged.

In this exclusive online issue, leading experts describe cutting-edge approaches to combating our collective ills. Learn about the gains being made on malaria, advances in pain control and efforts to construct a patch for human hearts. Other articles examine the road to real stem cell therapies, the promise of truly personalized medicine and the use of suspended animation to buy crucial time for patients in need.

Tackling Malaria Interventions available today could lead to decisive gains in prevention and treatment--if only the world would apply them (originally published December 2005)
Virtual-Reality Therapy Patients can get relief from pain or overcome their phobias by immersing themselves in computer-generated worlds (originally published August 2004)
Rebuilding Broken Hearts Biologists and engineers working together in the fledgling field of tissue engineering are within reach of one of their greatest goals: constructing a living human heart patch (originally published November 2004)
Toward Better Pain Control Advances in understanding the cells and molecules that transmit pain signals are providing new targets for drugs that could relieve various kinds of pain--including those poorly controlled by existing therapies (originally published June 2006)
The Stem Cell Challenge What hurdles stand between the promise of human stem cell therapies and real treatments in the clinic? (originally published June 2004)
Genomes for All Next-generation technologies that make reading DNA fast, cheap and widely accessible are coming in less than a decade. Their potential to revolutionize research and bring about the era of truly personalized medicine means the time to start preparing is now (originally published January 2006)
Buying Time in Suspended Animation An ability to put the human body on hold could safeguard the critically injured or preserve donor organs for transport. Does the power to reversibly stop our biological clocks already lie within us? (originally published June 2005)
Extreme Physics II
Introduction Imagine a world in which spacetime is a fluid, the constants of nature change with time, and our universe is but one of a virtually infinite number of universes. Bizarre? Yes. Impossible? Not at all. Indeed, such scenarios reflect the current thinking of some of today's foremost physicists. And they are just some of the cutting edge ideas that leading authorities explore in this, our second exclusive online issue on extreme physics.

In the pages that follow, you'll also learn how researchers are recreating the conditions of the nascent universe; why gravity and mass are still surprising; and how physicists could soon use quantum black holes to probe the extra dimensions of space. So buckle up--you're in for a mind-bending ride.

The First Few Microseconds In recent experiments, physicists have replicated conditions of the infant universe--with startling results (originally published May 2006)
An Echo of Black Holes Sound waves in a fluid behave uncannily like light waves in space. Black holes even have acoustic counterparts. Could spacetime literally be a kind of fluid, like the ether of pre-Einsteinian physics? (originally published December 2005)
The Illusion of Gravity The force of gravity and one of the dimensions of space might be generated out of the peculiar interactions of particles and fields existing in a lower-dimensional realm (originally published November 2005)
The Mysteries of Mass Physicists are hunting for an elusive particle that would reveal the presence of a new kind of field that permeates all of reality. Finding that Higgs field will give us a more complete understanding about how the universe works (originally published July 2005)
Inconstant Constants Do the inner workings of nature change with time? (originally published June 2005)
Quantum Black Holes Physicists could soon be creating black holes in the laboratory (originally published May 2005)
The String Theory Landscape The theory of strings predicts that the universe might occupy one random "valley" out of a virtually infinite selection of valleys in a vast landscape of possibilities (originally published September 2004)
Introduction "Nothing in biology makes sense except in light of evolution." So declared geneticist Theodosius Dobzhansky in 1973. Today's scientists agree: evolution is without a doubt the cornerstone of modern biology. Yet in school districts across the U.S., proponents of creationist ideas such as intelligent design are attempting to introduce their nonscientific alternatives to evolution into curriculums.

Spurred by this worrying state of affairs, we have put together a collection of some of our favorite articles concerning the history of life, starting with a firm refutation of creationist arguments by Scientific American editor-in-chief John Rennie. Riveting accounts of what scientists have pieced together thus far about the evolution of earth's creatures follow. Learn how four-legged land animals evolved from fish, how birds descended from dinosaurs and where whales come from. Explore the origins of early animals, and retrace the steps of paleontologists hot on the fossil trail of the earliest human ancestor. Also, discover how the application of evolutionary biology to medicine is informing medical research.

15 Answers to Creationist Nonsense Opponents of evolution want to make a place for creationism by tearing down real science, but their arguments don't hold up (originally published July 2002)
The Evolution of Life on Earth The history of life is not necessarily progressive; it is certainly not predictable. The earth's creatures have evolved through a series of contigent and fortuitous events (originally published in Dinosaurs and Other Monsters)
The Early Evolution of Animals Tiny fossils reveal that complex animal life is older than we thought--by at least as much as 50 million years (originally published August 2005)
Getting a Leg Up on Land Recent fossil discoveries cast light on the evolution of four-limbed animals from fish (originally published December 2005)
The Origin of Birds and Their Flight Anatomical and aerodynamic analyses of fossils and living birds show that birds evolved from small, predatory dinosaurs that lived on the ground (originally published February 1998)
The Mammals That Conquered the Seas New fossils and DNA analyses elucidate the remarkable evolutionary history of whales (originally published in Dinosaurs and Other Monsters)
An Ancestor to Call Our Own Controversial new fossils could bring scientists closer than ever to the origin of humanity (originally published in New Look at Human Evolution)
Cichlids of the Rift Lakes The extraordinary diversity of cichlid fishes challenges entrenched ideas of how quickly new species can arise (originally published February 1999)
Evolution and the Origins of Disease The principles of evolution by natural selection are finally beginning to inform medicine (originally published November 1998)
The Child's Mind
Introduction The remarkable physical transformation children undergo as they grow up is matched only by the metamorphosis of their minds. Parents, of course, play a critical role in this aspect of development. But what's really going on in a child's head? Kids can't always tell us what's on their minds. Psychologists, neurobiologists and other scientists can help fill in the blanks, however.

In this exclusive online issue, leading authorities share their insights into the minds of the young. Learn how children develop morals, why they talk to themselves, and what happens to brain development and function in the face of abuse at an early age. Other articles explore how reading should be taught, how attention-deficit hyperactivity disorder arises and what unique challenges gifted children face.

The Moral Development of Children It is not enough for kids to tell right from wrong. They must develop a commitment to acting on their ideals. Enlightened parenting can help (originally published August 1999)
Why Children Talk to Themselves Although children are often rebuked for talking to themselves out loud, doing so helps them control their behavior and master new skills (originally published November 1994)
Scars That Won't Heal: The Neurobiology of Child Abuse Maltreatment at an early age can have enduring negative effects on a child's brain development and function (originally published March 2002)
How Should Reading be Taught? Educators have long argued over the best way to teach reading to children. The research, however, indicates that a highly popular method is inadequate on its own (originally published March 2002)
Uncommon Talents: Gifted Children, Prodigies and Savants Possessing abilities well beyond their years, gifted children inspire admiration, but they also suffer ridicule, neglect and misunderstanding (originally published in Scientific American Presents; Exploring Intelligence)
Attention-Deficit Hyperactivity Disorder A new theory suggests the disorder results from a failure in self-control. ADHD may arise when key brain circuits do not develop properly, perhaps because of an altered gene or genes (originally published September 1998)
The Nanotech Revolution
Introduction Good things come in small packages. That, surely, is the mantra of today's researchers working in the nascent field of nanotechnology. What on earth is nanotech, you ask? Well, simply put, it's the science of the small. And chances are, if it hasn't already found its way into your life, it will in the not-so-distant future.

In this compilation of articles published over the past five years, leading authorities trace the steps scientists have taken in ushering us into the nano age--and make predictions about what is to come. Michael Roukes describes the unique mesoscale realm in which nanotechnological devices exist and contends that engineers will not be able to make reliable nanodevices until they understand the physical principles that govern matter there. Peter Vettiger and Gerd Binnig recount their efforts to build the first "nanodrive"--a micromechanical digital storage device with nano-size components. And Nadrian C. Seeman explains how DNA is an ideal molecule for building nano-scale structures that hold molecule-size electronic devices, or guest molecules for crystallography.

Other articles examine the promise of carbon nanotubes, the prospects for self-assembling nanostructures and ways to circumvent the problems inherent in the nanowires that will form the basis for tomorrow's nanocomputing circuitry. --The Editors

Plenty of Room, Indeed There is plenty of room for practical innovation at the nanoscale. But first, scientists have to understand the unique physics that governs matter there (originally published in The Edge of Physics)
The Nanodrive Project Inventing a nanotechnology device for mass production and consumer use is trickier than it sounds (originally published January 2003)
Innovations: Nano Patterning IBM brings closer to reality chips that put themselves together (originally published March 2004)
The First Nanochips As scientists and engineers continue to push back the limits of chipmaking technology, they have quietly entered into the nanometer realm (originally published April 2004)
Nanotechnology and the Double Helix DNA is more than just the secret of life - it is also a versatile component for making nanoscopic structures and devices (originally published June 2004)
Nanotubes in the Clean Room Talismans of a thousand graduate projects may soon make their way into electronic memories (originally published February 2005)
Crossbar Nanocomputers Crisscrossing assemblies of defect-prone nanowires could succeed today's silicon-based circuits (originally published November 2005)
Best of Ask the Experts
Introduction From why the sky is blue to how Internet search engines work, we're serving up answers to your burning science and technology questions. Over the years, we have invited readers to submit their queries to us. We've then found scientists with the appropriate expertise to offer explanations. This compilation brings together the most fascinating of these exchanges to date.

In this issue, you'll find the answers to more than 80 fascinating questions about every day--and not so everyday--occurrences. Learn how caffeine is removed from coffee, what causes hiccups, why bees buzz and why life expectancy is longer for women than it is for men. Find out how long a person can survive without food, how the abbreviations of the periodic table were determined--or even what would happen if you fell through a hypothetical hole in the earth.

These Q&As are sure to make you the shining star at any cocktail party. And who knows, maybe after reading them, you'll be inspired to send in your own questions. If so, just drop us a line at --The Editors

Ask the Experts What is antimatter?; Why does your stomach growl when you are hungry? (originally published April 2002)
Ask the Experts Why do my eyes tear when I peel an onion? What is the origin of zero? (originally published May 2002)
Ask the Experts Do people lose their senses of smell and taste as they age? What happens when an aircraft breaks the sound barrier? (originally published June 2002)
Ask the Experts How long can humans stay awake? When Tyrannosaurus rex fell, how did it get up, given its tiny arms? (originally published July 2002)
Ask the Experts How can an artificial sweetener contain no calories? What is a blue moon? (originally published August 2002)
Ask the Experts What exactly is déjã vu? How can graphite and diamond be so different if they are both composed of pure carbon? (originally published September 2002)
Ask the Experts How is caffeine removed to produce decaffeinated coffee? Why is spider silk so strong? (originally published October 2002)
Ask the Experts Why do we yawn when we are tired? And why does it seem to be contagious? Why do stars twinkle? (originally published November 2002)
Ask the Experts How does the Venus flytrap digest flies? How do rewritable CDs work? (originally published December 2002)
Ask the Experts How do Internet search engines work? What is quicksand? (originally published January 2003)
Ask the Experts Why do some people get more cavities than others do? Why are snowflakes symmetrical? (originally published February 2003)
Ask the Experts What is the difference between artificial and natural flavors? How long can the average person survive without water? (originally published March 2003)
Ask the Experts Why do computers crash? What causes thunder? (originally published May 2003)
Ask the Experts Why do hangovers occur? Why does shaking a can of coffee cause the larger grains to move to the surface? (originally published June 2003)
Ask the Experts Why does reading in a moving car cause motion sickness? How long do stars usually live? (originally published July 2003)
Ask the Experts Would you fall all the way through a hypothetical hole in the earth? How do manufacturers calculate calories for packages foods? (originally published August 2003)
Ask the Experts I was vaccinated against smallpox 40 years ago. Am I still protected? Why is the South Pole colder than the North Pole? (originally published September 2003)
Ask the Experts What causes insomnia? Why is the sky blue? (originally published October 2003)
Ask the Experts What makes Kansas, Texas and Oklahoma so prone to tornadoes? Are humans the only primates that cry? (originally published November 2003)
Ask the Experts What is game theory and what are some of its applications? Why do we get goose bumps? (originally published December 2003)
Ask the Experts How does spending prolonged time in microgravity affect astronauts? How do geckos' feet unstick from a surface? (originally published January 2004)
Ask the Experts How does exercise make your muscles stronger? What causes a mirage? (originally published February 2004)
Ask the Experts Why are blood transfusions not rejected, as can happen with organs? How can deleted computer files be retrieved at a later date? (originally published March 2004)
Ask the Experts How do dimples on golf balls affect their flight? How does club soda remove red wine stains? (originally published April 2004)
Ask the Experts Do we really use only 10 percent of our brains? How can the weight of Earth be determined? (originally published June 2004)
Ask the Experts What causes hiccups? How do sunless tanners work? (originally published August 2004)
Ask the Experts Why is the fuel economy of a car better in the summer? Why does inhaling helium make one's voice sound strange? (originally published September 2004)
Ask the Experts Why do some expectant fathers experience pregnancy symptoms? Why does a shaken soda fizz more than an unshaken one? (originally published October 2004)
Ask the Experts How do scientists know the composition of the Earth's interior? How does decanting red wine affect its taste? And why not decant white? (originally published November 2004)
Ask the Experts Why is life expectancy longer for women than it is for men? (originally published December 2004)
Ask the Experts How do computer hackers "get inside" a computer? Why do traffic jams sometimes seem to appear out of nowhere? (originally published January 2005)
Ask the Experts Why do bags form below our eyes? How are the abbreviations of the periodic table determined? (originally published February 2005)
Ask the Experts How long can a person survive without food? How do scientists detect new elements that last only milliseconds? (originally published March 2005)
Ask the Experts What is the fastest event that can be measured? Why is normal blood pressure less than 120/80? Why don't these numbers change with height? (originally published April 2005)
Ask the Experts How does anesthesia work? Are one's fingerprints similar to those of his or her parents? (originally published May 2005)
Ask the Experts How are past temperatures determined from an ice core? Why do people have different blood types? (originally published June 2005)
Ask the Experts Why do flowers have scents? How are tattoos removed? (originally published July 2005)
Ask the Experts What causes headaches? How can a poll of only 1,004 Americans represent 260 million people? (originally published August 2005)
Ask the Experts Are food cravings the body's way of telling us that we are lacking nutrients? What causes feedback in a guitar or microphone? (originally published September 2005)
Ask the Experts What causes shin splints? Why do bees buzz? (originally published October 2005)
Extreme Universe
Introduction Looking up at the heavens on a crisp autumn evening, it all seems so peaceful. But the serene beauty of the night sky belies the tumultuous nature of the cosmos. Light-years away, stars are being born, black holes are forming, and even the gas between the stars is a hotbed of activity.

In this exclusive online issue, leading authorities recount some of the most thrilling and bizarre discoveries about our universe that have been made in recent years. Explore the link between gamma-ray bursts and black holes. Learn how magnetized stars known as magnetars are altering the quantum vacuum. Tour the interstellar medium, with its landscape of gas fountains and bubbles blown by exploding stars. And find out why scientists are saying the cosmos is experiencing a kind of midlife crisis.

Other articles delve into even weirder phenomena. Jacob Beckenstein explains how the universe could be like a giant hologram. Glen Starkman and Dominik Schwarz listen to the "music" of the cosmic microwave background--and find it strangely out of tune. And Max Tegmark explains how cosmological observations imply that parallel universes really do exist. --The Editors

Is the Universe Out of Tune? Like the discord of key instruments in a skillful orchestra quietly playing the wrong piece, mysterious discrepancies have arisen between theory and observations of the "music" of the cosmic microwave background. Either the measurements are wrong or the universe is stranger than we thought (originally published August 2005)
The Midlife Crisis of the Cosmos Although it is not as active as it used to be, the universe is still forming stars and building black holes at an impressive pace (originally published January 2005)
Magnetars Some stars are magnetized so intensely that they emit huge bursts of magnetic energy and alter the very nature of the quantum vacuum (originally published February 2003)
Parallel Universes Not just a staple of science fiction, other universes are a direct implication of cosmological observations (originally published May 2003)
Information in the Holographic Universe Theoretical results about black holes suggest that the universe could be like a gigantic hologram (originally published August 2003)
The Gas between the Stars Filled with colossal fountains of hot gas and vast bubbles blown by exploding stars, the interstellar medium is far more interesting than scientists once thought (originally published January 2002)
The Brightest Explosions in the Universe Every time a gamma-ray burst goes off, a black hole is born (originally published December 2002)
The Human Odyssey
Introduction If you want to know where you come from, those genealogy Web sites will get you only so far. To really plumb your origins, you'll need to look at the fossil record. And what a record it is, documenting millions of years of human and ape evolution.

This exclusive online issue highlights some of the most exciting paleoanthropological discoveries of the past decade. Travel back in time to the Miocene epoch, when Earth was truly a planet of the apes. Explore the intense debate surrounding the emergence of the first hominids in Africa. Discover when our kind started walking upright. Learn how spectacular fossils from the Republic of Georgia have toppled old ideas about when, how and why humans finally left the African motherland to colonize the rest of the world. And get inside the minds of our ancestors as they started thinking like us--much earlier than expected, it turns out.

After millions of years of sharing the landscape with multiple hominid forms, Homo sapiens eventually found itself alone, as one article in this compendium recounts. But the roots of our solitude may be shallower than previously thought: the recent and controversial discovery on Flores of miniature human remains suggests that our species coexisted alongside another human type as recently as 13,000 years ago. --The Editors

Planet of the Apes During the Miocene epoch, as many as 100 species of apes roamed throughout the Old World. New fossils suggest that the ones that gave rise to living great apes and humans evolved not in Africa but Eurasia (originally published August 2003)
An Ancestor to Call Our Own Controversial new fossils could bring scientists closer than ever to the origin of humanity (originally published January 2003)
Early Hominid Fossils from Africa A new species of Australopithecus, the ancestor of Homo, pushes back the origins of bipedalism to some four million years ago (originally published June 1997)
Once We Were Not Alone Today we take for granted that Homo sapiens is the only hominid on earth. Yet for at least four million years many hominid species shared the planet. What makes us different? (originally published in New Look at Human Evolution)
Stranger in a New Land Stunning finds in the Republic of Georgia upend long-standing ideas about the first hominids to journey out of Africa (originally published November 2003)
The Morning of the Modern Mind Controversial discoveries suggest that the roots of our vaunted intellect run far deeper than is commonly believed (originally published June 2005)
The Littlest Human A spectacular find in Indonesia reveals that a strikingly different hominid shared the earth with our kind in the not so distant past (originally published February 2005)
Tackling Major Killers - Infectious Diseases
Introduction Infectious disease remains one of medicine's greatest challenges. Indeed, globalization has rendered the problem more pressing than ever before: viruses and bacteria once relegated to faraway locales can reach the other side of the planet in a day's time--and propagate unchecked in their new environs.

In this exclusive online issue, leading researchers describe their efforts to tame some of the most intractable diseases of our time. Stanley Prusiner explains how new tests are enabling fast detection of prions, the agents that cause mad cow disease. John Young and his colleagues discuss strategies for the prevention and treatment of anthrax. And David Ojcius and his collaborators report on the latest approaches to stemming the spread of chlamydia.

Not all of the news is good. The search for an AIDS vaccine continues a quarter century after the discovery of HIV, as another article in this issue recounts. And terrorism threatens to reintroduce smallpox nearly 30 years after its elimination from the wild. But computer simulations of smallpox and other diseases are revealing how these scourges spread--information that could help halt epidemics. And novel vaccines and antivirals stand poised to pave the way for a healthier humanity. --The Editors

If Smallpox Strikes Portland... EpiSims unleashes virtual plagues in real cities to see how social networks spread disease. That knowledge might help stop epidemics (originally published March 2005)
Can Chlamydia Be Stopped? Chlamydia is a rampant sexually transmitted disease, the world's leading cause of preventable blindness and a possible contributor to heart disease. Recent discoveries are suggesting new ways to curtail its spread (originally published May 2005)
Attacking Anthrax Recent discoveries are suggesting much-needed strategies for improving prevention and treatment. High on the list: ways to neutralize the anthrax bacterium's fiendish toxin (originally published March 2002)
Detecting Mad Cow Disease New tests can rapidly identify the presence of dangerous prions - the agents responsible for the malady - and several compounds offer hope for treatment (originally published July 2004)
Hope in a Vial Will there be an AIDS vaccine anytime soon? (originally published June 2002)
Edible Vaccines One day children may get immunized by munching on foods instead of enduring shots. More important, food vaccines might save millions who now die for lack of access to traditional inoculants (originally published September 2000)
Beyond Chicken Soup The antiviral era is upon us, with an array of virus-fighting drugs on the market and in development. Research into viral genomes is fueling much of this progress (originally published November 2001)
Science and Art
Introduction Scientific American may be best known for its coverage of such disciplines as astronomy and biotechnology, but as longtime readers can attest, the magazine has a tradition of examining cultural phenomena as well. It is in this spirit that we have put together a collection of articles exploring the intersection of science and art.

In this exclusive online issue, leading scientists share their expertise on what science can reveal about art--and vice versa. Discover the rock art of southern Africa, some of which dates back to more than 20,000 years ago, offering archaeologists unique insights into the minds of prehistoric humans. Tour the spectacularly decorated tomb of Nefertari, favorite wife of the Egyptian pharaoh Ramses II, which experts have taken great pains to conserve for future study--and public enjoyment. And learn how beautifully engraved wooden tablets hung under the roofs of religious buildings in Japan record a flourishing of native mathematics during the country's period of seclusion from the West.

Art, it is often said, imitates life, and can thus provide a window on society. It can also reveal much about the brain. Studies suggest that a number of great artists have been afflicted with madness and that there exists a link between creativity and mood disorders. Likewise, studies of how the blind sketch their surroundings indicate that touch and vision are closely tied. Two articles in this issue explore those relationships.--The Editors

Rock Art in Southern Africa Paintings and engravings made by ancestors of the San peoples encode the history and culture of a society thousands of years old (originally published November 1996)
Preserving Nefertari's Legacy The tomb of this ancient Egyptian queen is testament to the great love of Pharaoh Ramses II. Its preservation is testament to advances in conservation (originally published October 1999)
Japanese Temple Geometry During Japan's period of national seclusion (1639-1854), native mathematics thrived, as evidenced in "sangaku"-wooden tablets engraved with geometry problems hung under the roofs of shrines and temples (originally published May 1998)
Manic-Depressive Illness and Creativity Does some fine madness plague great artists? Several studies now show that creativity and mood disorders are linked (originally published February 1995)
How the Blind Draw Blind and sighted people use many of the same devices in sketching their surroundings, suggesting that vision and touch are closely linked (originally published January 1997)
Battle of the Sexes
Introduction As any nature lover knows, males and females of the same species commonly diverge in appearance and behavior--a reflection of their differing roles in reproduction. Take, for example, the brilliantly hued male peacock and his relatively drab counterpart, or the promiscuous sage grouse male and discriminating female.

This exclusive online issue explores that divide through a collection of especially fascinating case studies. Uncover the invisible charms of the Little Yellow butterfly, whose males and females are identical in color to the human eye but quite different to that of the insect, thanks to the male's ultraviolet adornments. Learn how a female guppy selects her mate from a school of competing males (hint: copycatting seems to play a role). Consider katydid courtship, unusual in that the male is the choosy one, carefully considering his options before bestowing on his bride a precious nuptial gift. And then there's the prairie vole, whose pheromones appear to orchestrate a reproductive strategy rarely seen in mammals: monogamy.

Eighteenth-century naturalists interpreted plant reproductive biology through the lens of human sexuality and social customs of the day, as an article in this issue recounts. It is surely tempting in our modern era to take the reverse tack: look to other organisms to gain insight into gender differences and social organization in our own species. Studies of the bonobo, for one, raise the possibility that rather than being male-centered, early human societies were female-centered. In any event, men and women almost certainly played different roles in evolutionary history and may thus have been subjected to varying selective pressures. According to our final article, this could help explain alleged cognitive differences between the sexes today.--The Editors

In Brief Wimps Win in Cockroach Romance; Fluorescent Feathers Elicit Parrot Amour; Bile Acid Key to Lamprey Love; Gene Linked to Lasting Love in Voles; Male Songbird Responds to Mate Only When He's the Third Wheel; For Spiders, Familiarity Breeds Love; Fish Study Finds That Male Mate Choice Matters; Female Antelopes Fight for Fine Mates; Birds of Different Feathers Pair Together; Mating Lizards Play a Game of Rock-Paper-Scissors; Wasps Tamper with Plant Chemistry to Woo Mates; Ticking Biological Clock Drives Female Cockroaches to Lower Standards; Male Pregnancy May Spur Seahorse Speciation
Mating Strategies in Butterflies Butterflies meet, woo and win their mates using seductive signals and clever strategies honed by evolution (originally published July 1998)
How Females Choose Their Mates Females often prefer to mate with the most flamboyant males. Their choice may be based on a complex interaction between instinct and imitation (originally published April 1998)
Glandular Gifts The way to a katydid's heart is through her stomach (originally published August 1997)
Monogamy and the Prairie Vole Studies of the prairie vole--a secretive, mouselike animal--have revealed hormones that may be responsible for monogamous behavior (originally published June 1993)
The Loves of the Plants Carl Linnaeus classified plants according to their reproductive parts, endowing them as well with sex lives reflecting 18th-century values and controversies (originally published February 1996)
Bonobo Sex and Society The behavior of a close relative challenges assumptions about male supremacy in human evolution (originally published March 1995)
Sex Differences in the Brain Men and women display patterns of behavioral and cognitive differences that reflect varying hormonal influences on brain development (originally published in The Hidden Mind)
Extreme Engineering
Introduction They are some of the most remarkable achievements of our time: a suspension bridge spanning nearly 4,000 meters, a mouse genetically modified to be smarter than its peers, robots capable of exploring a distant planet. Who would have thought, just decades ago, that such marvelous visions might actually come to pass?

In this exclusive online issue, leading scientists and journalists reflect on those breathtaking feats and others on the horizon. Learn what steps researchers have taken toward growing replacement organs, how aeronautics engineers are taking a cue from our feathered friends, and why nanotechnology might just lay the groundwork for a new industrial revolution. After reading this issue, you might well conclude that the only limitation to what our species can accomplish is the breadth of our imagination.--The Editors

The Longest Suspension Bridge The Akashi Kaikyo Bridge has broken many records and weathered an earthquake--even while it is being completed (originally published December 1997)
Little Big Science Nanotechnology is all the rage. But will it meet its ambitious goals? And what the heck is it? (originally published September 2001)
Growing New Organs Researchers have taken the first steps toward creating semisynthetic, living organs that can be used as human replacement parts (originally published April 1999)
Synthetic Life Biologists are crafting libraries of interchangeable DNA parts and assembling them inside microbes to create programmable, living machines (originally published May 2004)
Electrodynamic Tethers in Space By exploiting fundamental physical laws, tethers may provide low-cost eletrical power, drag, thrust, and artificial gravity for spaceflight (originally published August 2004)
Flying on Flexible Wings Future aircraft may fly more like birds, adapting geometrics of their wings to best suit changing flight conditions (originally published November 2003)
Building a Brainier Mouse By genetically engineering a smarter than average mouse, scientists have assembled some of the central molecular components of learning and memory (originally published April 2000)
The Spirit of Exploration NASA's rover fights the curse of the Angry Red Planet (originally published March 2004)
Great Minds
Introduction The inventor of the the World Wide Web, the biographer of chimpanzees, the father of the hydrogen bomb--Scientific American has a long tradition of profiling those individuals whose work has made an indelible impact on our lives and the way we view the world around us. This exclusive online issue brings together some of our most memorable encounters.

Unravel string theory with physicist Brian Greene. Find out what dinosaur hunter Paul Sereno does in his downtime. (Hint: it's more than many of us do in our uptime.) Learn how a bout with breast cancer helped astronomer Jill Tarter become a team player in the quest to detect signs of extraterrestrial intelligence. Meet maverick medical researcher Peter Duesberg, who has challenged conventional wisdom on HIV and cancer--and been largely shunned by the scientific establishment as a result. In the pages that follow, these scientists and many others share their discoveries, dreams, motivations and fears. Move over, Barbara Walters--here's our list of truly fascinating people.--The Editors

Unearthing History Mary Leakey (originally published October 1994)
Fighting the Darkness in El Dorado Anthropologist Napoleon Chagnon defends himself against Yanomamö charges (originally published March 2001)
Gombe's Famous Primate Jane Goodall (originally published October 1997)
Paleontology's Indiana Jones From digging to designing, Paul S. Sereno has helped map the evolution of dinosaurs (originally published June 2000)
Father of Spirit and Opportunity With the success of twin rovers on the Red Planet, Steven W. Squyres and his team are showing how to conduct robotic missions--and setting the stage for human exploration (originally published October 2004)
An Ear to the Stars Despite long odds, astronomer Jill C. Tarter forges ahead to improve the chances of picking up signs of extraterrestrial intelligence (originally published November 2002)
When the Sky Is Not the Limit In bringing the stars indoors, astrophysicist Neil deGrasse Tyson expands the visitor's universe (originally published February 2000)
Geographer of the Male Genome The notion of the Y sex chomosome as a genetic wasteland still entices biologists. David C. Page has spent a good part of his career knocking down that myth (originally published December 2004)
Revisiting Old Battlefields Edward O. Wilson (originally published April 1994)
Defender of the Plant Kingdom Botanist Peter H. Raven wants the world to save its plant species. All of them (originally published September 1999)
The Billionaire Conservationist Can Ted Turner save threatened species? He is using his private lands and deep pockets to reintroduce animals driven off by development (originally published August 2002)
Dissent in the Maelstrom Maverick meteorologist Richard S. Lindzen keeps right on arguing that human-induced global warming isn't a problem (originally published November 2001)
Save the Muntjacs And warty pigs, saolas, zebra-striped rabbits--helping to discover and preserve new animals is biologist Alan R. Rabinowitz's game (originally published September 2000)
Thawing Scott's Legacy A pioneer in atmospheric ozone studies, Susan Solomon rewrites the history of a fatal expedition (originally published December 2001)
Not Just Fun and Games Best known for inventing the game of Life, John H. Conway is adept at finding the theorems hidden in simple puzzles (originally published April 1999)
Monstrous Moonshine is True Richard Borcherds proved it--and discovered spooky connections between the smallest objects imagined by physics and one of the most complex objects known to mathematics (originally published November 1998)
Molding the Web Its inventor, Tim Berners-Lee, says the World Wide Web hasn't nearly reached its potential (originally published December 1997)
Pinker and the Brain Cognitive scientist Steven Pinker plumbs the evolutionary origins of language and behavior while keeping his detractors at bay (originally published July 1999)
Flynn's Effect Intelligence scores are rising, James R. Flynn discovered--but he remains very sure we're not getting any smarter (originally published January 1999)
Why Machines Should Fear Once a curmudgeonly champion of "usable" design, cognitive scientist Donald A. Norman argues that future machines will need emotions to be truly dependable (originally published January 2004)
A Greene Universe Theoretical physicist Brian Greene has a simple goal--explaining the universe with strings (originally published April 2000)
Throwing Einstein for a Loop Physicist Fotini Markopoulou Kalamara has developed a way to connect relativity with quantum theory - while making sure that cause still precedes effect (originally published December 2002)
Perpendicular to the Mainstream Freeman J. Dyson (originally published August 1993)
Infamy and Honor at the Atomic Café Edward Teller has no regrets about his contentious career (originally published October 1999)
Dissident or Don Quixote? Challenging the HIV theory got virologist Peter H. Duesberg all but excommunicated from the scientific orthodoxy. Now he claims that science has got cancer all wrong (originally published August 2001)
The $13-Billion Man Why Thomas R. Cech--the head of the Howard Hughes Medical Institute--could be the most powerful individual in biomedicine (originally published January 2001)
Starving Tumors of Their Lifeblood No, Judah Folkman probably won't cure cancer in two years. He says he simply hopes to render it a manageable, chronic disease (originally published October 1998)
Where Science and Religion Meet The U.S. head of the human Genome Project, Francis S. Collins, strives to keep his Christianity from interfering with his science and politics (originally published February 1998)
Terms of Engagement Irving Weissman directs a new institute dedicated to the cloning of human embryonic stem cells. Just don't call it cloning (originally published July 2003)
Tackling Major Killers - Cancer
Introduction More than 1.36 million Americans will be diagnosed with cancer in 2004, and 563,700 will succumb to the disease, according to estimates from the American Cancer Society. Accounting for one in four mortalities, cancer is second only to heart disease when it comes to cause of death. These grim statistics notwithstanding, researchers have made great strides in understanding--and combating--the scourge. Thanks to their efforts, a number of new cancer-fighting tactics are on the horizon.

In this exclusive online issue, comprised of articles published over the past five years, leading scientists and journalists explain recent advances in cancer research. Learn how cells become malignant; how viruses, dendritic cells and light-sensitive pigments are finding work as anti-cancer agents; and how researchers might one day be able to manipulate the formation of new blood vessels to treat the disease. Other reports explain why hormone-replacement therapy may not be such a bad idea--and why alternative medicine is. In addition, two articles sketch Judah Folkman, who discovered that two natural compounds dramatically shrink tumors by cutting off their blood supply, and Peter Duesberg, who has claimed that the scientific establishment has an incorrect theory of how cancer arises. --The Editors

Untangling the Roots of Cancer Recent evidence challenges long-held theories of how cells turn malignant - and suggests new ways to stop tumors before they spread (originally published in The Science of Staying Young)
Vessels of Death or Life Angiogenesis--the formation of new blood vessels--might one day be manipulated to treat disorders from cancer to heart disease. First-generation drugs are now in the final phase of human testing (originally published December 2001)
The Long Arm of the Immune System Dendritic cells catch invaders and tell the immune system when and how to respond. Vaccines depend on them, and scientists are even employing the cells to stir up immunity against cancer (originally published November 2002)
New Light on Medicine Pigments that turn caustic on exposure to light can fight cancer, blindness and heart disease. Their light-induced toxicity may also help explain the origin of vampire tales (originally published January 2003)
Tumor-Busting Viruses A new technique called virotherapy harnesses viruses, those banes of humankind, to stop another scourge--cancer (originally published October 2003)
Hormone Hysteria Hormone replacement therapy may not be so bad (originally published October 2003)
Skeptic: What's the Harm? Alternative medicine is not everything to gain and nothing to lose (originally published December 2003)
Quiet Celebrity: Interview with Judah Folkman The renowned medical researcher reflects on the promise of anti-angiogenesis drugs (originally published November 4, 2002)
Profile: Dissident or Don Quixote? Challenging the HIV theory got virologist Peter H. Duesberg all but excommunicated from the scientific orthodoxy. Now he claims that science has got cancer all wrong (originally published August 2001)
Amazing Animals
Introduction We humans tend to think of ourselves as Nature's ultimate creation. A quick survey of the creatures with which we share the planet suggests that's a myopic view of things. Billions of years of evolution has produced a rich diversity of animals, each exquisitely adapted to its ecological niche. This exclusive online issue celebrates some of the more spectacular results.

In the pages that follow, leading biologists share their insights into beasts both familiar and foreign. Some are remarkable for their physical characteristics. Take, for example, the basilisk lizard, best known for its ability to walk on water. Or the star-nosed mole, whose stellar accessory works uncannily like an eye in its dark, damp environs. And then there's the komodo dragon, a rare reptile whose stealth, power and supersized proportions have earned it a fearsome reputation indeed.

Other creatures amaze with their behavior. Some ants conduct warfare that would have given Genghis Khan pause. Parrots match wits with dolphins and nonhuman primates. Lions cooperate, but only when they stand to benefit. And chimpanzees pass social customs down from generation to generation--in other words, they have culture.

Animals fascinate us with the ways in which they resemble and differ from our kind, yet they are neither mirror nor measuring stick. Perhaps American author Henry Beston put it best: "They are other nations, caught with ourselves in the net of life and time, fellow prisoners of the splendor and travail of the earth." --The Editors

Beasts in Brief Fido Found to Be Wiz with Words; King of Beasts Suffers to Be Beautiful; Crafty Crow Rivals Primates in Toolmaking; How Bears Power-Nap; The Cultured Orangutan; Dolphin Self-Recognition Mirrors Our Own; How Geckos Get a Grip; Brainy Bees Think Abstractly
Running on Water The secret of the basilisk lizard's strategy lies in its stroke (originally published September 1997)
The Nose Takes a Starring Role The star-nosed mole has what is very likely the world's fastest and most fantastic nose (originally published July 2002)
The Komodo Dragon On a few small islands in the Indonesian archipelago, the world's largest lizard reigns supreme (originally published March 1999)
Slave-Making Queens Life in certain corners of the ant world is fraught with invasion, murder and hostage-taking. The battle royal is a form of social parasitism (originally published November 1999)
Divided We Fall: Cooperation among Lions Although they are the most social of all cats, lions cooperate only when it is in their own best interest (originally published May 1997)
Talking with Alex: Logic and Speech in Parrots Parrots were once thought to be no more than excellent mimics, but research is showing that they understand what they say. Intellectually, they rival great apes and marine mammals (originally published in Scientific American Presents: Exploring Intelligence)
The Cultures of Chimpanzees Humankind's nearest relative is even closer than we thought: chimpanzees display remarkable behaviors that can only be described as social customs passed on from generation to generation (originally published January 2001)
Mysteries of the Milky Way
Introduction Viewed from above, it appears as a giant pinwheel of diamond-studded smoke. From Earth, it cuts a pale swath of light across the summer sky. This is the Milky Way, our home galaxy, and it has captivated humankind for millennia. Galileo was the first to formally probe its secrets. Armed with a telescope of his own devising, he determined that the shimmering band was in fact composed of stars. Astronomers have been smitten ever since.

This exclusive online issue brings together stunning Milky Way discoveries from the past decade. Leading scientists explain how our galaxy formed, how it continues to evolve and why only part of it is habitable. Other articles home in on particular Milky Way elements--our paradoxical sun, cosmic dust and the dynamic interstellar medium. Of course, as fascinating as our galactic neighborhood is, astronomers also yearn to peer beyond it. These efforts, too, are summarized here. We hope that after reading this issue, you'll see our spectacular corner of the cosmos in a different light. --The Editors

How the Milky Way Formed Its halo and disk suggest that the collapse of a gas cloud, stellar explosions and the capture of galactic fragments may have all played a role (originally published January 1993)
Our Growing, Breathing Galaxy Long assumed to be a relic of the distant past, the Milky Way turns out to be a dynamic, living object (originally published January 2004)
Refuges for Life in a Hostile Universe Only part of our galaxy is fit for advanced life (originally published October 2001)
The Paradox of the Sun's Hot Corona Like a boiling teakettle atop a cold stove, the sun's hot outer layers sit on the relatively cool surface. And now astronomers are figuring out why (originally published in New Light on the Solar System)
The Gas between the Stars Filled with colossal fountains of hot gas and vast bubbles blown by exploding stars, the interstellar medium is far more interesting than scientists once thought (originally published January 2002)
The Secrets of Stardust Tiny grains of dust floating in interstellar space have radically altered the history of our galaxy (originally published December 2000)
Galaxies behind the Milky Way Over a fifth of the universe is hidden from view, blocked by dust and stars in the disk of our galaxy. But over the past few years, astronomers have found ways to peek through the murk (originally published October 1998)
21st-Century Robotics
Introduction Robotics in the new millennium may not yet have achieved the original goal of freely moving machines with humanlike intellectual capabilities, but it certainly has advanced by leaps and bounds. Today's machines not only aid industrial manufacturing, they can vacuum our homes, stand in as pets, explore other planets and even assist in surgeries.

Bots of the near future stand poised to further impress. Think brain-machine interfaces that enable people who have lost a limb to control a robotic replacement with their mind - a feat that has already been demonstrated in rats and monkeys. Imagine a team of tiny robots working together to inspect a collapsed building for trapped victims, or to spy on terrorists holding people hostage and relay critical information back to authorities. Robot designers in several laboratories are in fact developing just such millibot armies.

Leading researchers and journalists explore these developments and more in this exclusive online issue. Scientific American has a long tradition of publishing articles by smart people for smart people. As you ponder the progress of artificial intelligence in the pages that follow, consider the scenario envisioned by robotics pioneer Hans Moravec in his article in this issue: by 2050 machine smarts will rival our own.--The Editors

A New Race of Robots Around the U.S., engineers are finishing one-year crash projects to create robots able to dash 200 miles through the Mojave Desert in a day, unaided by humans. Scientific American tailed the odds-on favorite team for 10 months and found that major innovations in robotics are not enough to win such a contest. Obsession is also required (originally published March 2004)
The Spirit of Exploration NASA's rover fights the curse of the Angry Red Planet (originally published March 2004)
Controlling Robots with the Mind People with nerve or limb injuries may one day be able to command wheelchairs, prosthetics and even paralyzed arms and legs by "thinking them through" the motions (originally published October 2002)
An Army of Small Robots For robot designers these days, small is beautiful (originally published November 2003)
Rise of the Robots By 2050 robot "brains" based on computers that execute 100 trillion instructions per second will start rivaling human intelligence (originally published December 1999)
Plug-and-Play Robots Personal robots may soon be as cheap and customizable as personal computers (originally published April 2004)
Robots That Suck Have they finally come out with a robot for the rest of us? (originally published February 2003)
Long-Distance Robots The technology of telepresence makes the world even smaller (originally published December 2001)
Kibbles and Bytes How much is that robotic doggy in the window? (originally published June 2001)
Endangered Earth
Introduction The climate is warming, species are disappearing and the human population continues to expand. Rarely does a day pass without these and other observations about the state of the planet making headlines. But what does it all really mean? And what, if anything, can be done about it?

In this exclusive online issue, leading experts discuss threats to life on Earth as we know it. Learn how rising temperatures are transforming polar landscapes and global epidemiology, how the current extinction rate compares with past ones and how inadequate access to contraceptives could severely impact environment and health in coming years. Other articles explain how science might help preserve Earth's dwindling biodiversity, perhaps by cloning endangered species or marketing conservation services, for example. Consider this a snapshot of our imperiled planet--with prescriptions for positive change. --The Editors

On the Termination of Species Ecologists' warnings of an ongoing mass extinction are being challenged by skeptics and largely ignored by politicians. In part that is because it is surprisingly hard to know the dimensions of the die-off, why it matters and how it can best be stopped (originally published November 2001)
Cloning Noah's Ark Biotechnology might offer the best way to keep some endangered species from disappearing from the planet (originally published November 2000)
Rethinking Green Consumerism Buying green products won't be enough to save biodiversity in the tropics. A new plan for marketing conservation services may be the answer (originally published May 2002)
The Unmet Need for Family Planning Women and men in many countries still lack adequate access to contraceptives. Unless they are given the option of controlling their fertility, severe environmental and health problems loom in the coming century throughout large parts of the world (originally published January 2000)
Is Global Warming Harmful to Health? Computer models indicate that many diseases will surge as the earth's atmosphere heats up. Signs of the predicted troubles have begun to appear (originally published August 2000)
On Thin Ice How soon humanity will have to move inland to escape rising seas depends in great part on how quickly West Antarctica's massive ice sheet shrinks. Scientists are finally beginning to agree on what controls the size of the sheet and its rate of disintegration (originally published December 2002)
Meltdown in the North Sea ice and glaciers are melting, permafrost is thawing, tundra is yielding to shrubs - and scientists are struggling to understand how these changes will affect not just the Arctic but the entire planet (originally published October 2003)
Extreme Physics
Introduction Time travel, teleportation, parallel universes--in certain sectors of the physics community, notions once relegated to the realm of science fiction are now considered quite plausible. Indeed, by some accounts, the truth may be stranger than fiction. Consider the possibility that the universe is a huge hologram or that matter is composed of tiny, vibrating strings. Perhaps space and time are not continuous but instead come in discrete pieces. These are the wonderfully weird ways in which theorists are beginning to conceive of the world (or worlds!) around us.

In this exclusive online issue, leading authorities share their expertise on these cutting-edge ideas. Brian Greene untangles string theory; Max Tegmark reveals how astronomical observations support the existence of parallel universes; other scholars tackle quantum teleportation, negative energy, the holographic principle and loop quantum gravity; and Gordon Kane ushers in the dawn of physics beyond the Standard Model. --The Editors

Negative Energy, Wormholes and Warp Drive The construction of wormholes and warp drive would require a very unusual form of energy. Unfortunately, the same laws of physics that allow the existence of this "negative energy" also appear to limit its behavior (originally published January 2000)
Quantum Teleportation The science-fiction dream of "beaming" objects from place to place is now a reality - at least for particles of light (originally published April 2000)
Parallel Universes Not just a staple of science fiction, other universes are a direct implication of cosmological observations (originally published May 2003)
Information in the Holographic Universe Theoretical results about black holes suggest that the universe could be like a gigantic hologram (originally published August 2003)
The Future of String Theory: A Conversation with Brian Greene The physicist and best-selling author demystifies the ultimate theories of space and time, the nature of genius, multiple universes, and more (originally published November 2003)
Atoms of Space and Time We perceive space and time to be continuous, but if the amazing theory of loop quantum gravity is correct, they actually come in discrete pieces (originally published January 2004)
The Dawn of Physics beyond the Standard Model The Standard Model of particle physics is at a pivotal moment in its history: it is both at the height of its success and on the verge of being surpassed (originally published June 2003)
Diet and Health
Introduction If you're like many people, your New Year's resolution was to change your diet--whether by cutting back on quantity or improving quality, or both. In our fast-food era it is harder than ever to strike a healthy balance. And with new fad regimens springing up constantly, that balance is increasingly difficult to discern in the first place.

In this issue prominent researchers and journalists examine what we consume and how it affects us. Just how did our species find itself in such a nutritional predicament? Whatever happened to the food pyramid? Is moderate drinking good for you? Does caloric restriction actually promote longevity and youthfulness? Our authors tackle these questions and more. We think their writings will give you something to chew on. --The Editors

Food for Thought Dietary change was a driving force in human evolution (originally published December 2002)
Birth of the Modern Diet Ever wonder why dessert is served after dinner? The origins of modern Western cooking can be traced to ideas about diet and nutrition that arose during the 17th century (originally published August 2000)
Rebuilding the Food Pyramid The dietary guide introduced a decade ago has led people astray. Some fats are healthy for the heart, and many carbohydrates clearly are not (originally published January 2003)
Drink to Your Health? Three decades of research shows that drinking small to moderate amounts of alcohol has cardiovascular benefits. A thorny issue for physicians is whether to recommend drinking to some patients (originally published February 2003)
Gaining on Fat As a costly epidemic of obesity spreads through the industrial world, scientists are uncovering the biological roots of this complex disease. The work offers tantalizing hope for new ways to treat, and prevent, the health risks of excess weight (originally published August 1996)
The Serious Search for an Anti-Aging Pill In government laboratories and elsewhere, scientists are seeking a drug able to prolong life and youthful vigor. Studies of caloric restriction are showing the way (originally published August 2002)
Mathematical American
Introduction "Mathematics, rightly viewed, possesses not only truth, but supreme beauty." So wrote British philosopher and logician Bertrand Russell nearly 100 years ago. He was not alone in this sentiment. French mathematician Henri Poincaré declared that "the mathematician does not study pure mathematics because it is useful; he studies it because he delights in it and he delights in it because it is beautiful." Likewise, Einstein described pure mathematics as "the poetry of logical ideas." Indeed, many a scholar has remarked on the elegance of the science. It is in this spirit that we have put together a collection of Scientific American articles about math.

In this exclusive online issue, Martin Gardner, longtime editor of the magazine's Mathematical Games column, reflects on 25 years of fun puzzles and serious discoveries; other scholars explore the concept of infinity, the fate of mathematical proofs in the age of computers, and the thriving of native mathematics during Japan's period of national seclusion. The anthology also includes articles that trace the long, hard roads to resolving Fermat's Last Theorem and Zeno's paradoxes, two problems that for centuries captivated--and tormented--some of the discipline's most beautiful minds. --The Editors

A Quarter-Century of Recreational Mathematics The author of Scientifc American's column "Mathematical Games" from 1956 to 1981 recounts 25 years of amusing puzzles and serious discoveries (originally published August 1998)
The Death of Proof Computers are transforming the way mathematicians discover, prove and communicate ideas, but is there a place for absolute certainty in this brave new world? (originally published October 1993)
Resolving Zeno's Paradoxes For millenia, mathematicians and philosophers have tried to refute Zeno's paradoxes, a set of riddles suggesting that motion is inherently impossible. At last, a solution has been found (originally published November 1994)
A Brief History of Infinity The infinite has always been a slippery concept. Even the commonly accepted mathematical view, developed by Georg Cantor, may not have truly placed infinity on a rigorous foundation (originally published April 1995)
Fermat's Last Stand His most notorious theorem baffled the greatest minds for more than three centuries. But after 10 years of work, one mathematician cracked it (originally published November 1997)
Japanese Temple Geometry During Japan's period of national seclusion (1639-1854), native mathematics thrived, as evidenced in sangaku - wooden tablets engraved with geometry problems hung under the roofs of shrines and temples (originally published May 1998)
Germ Wars
Introduction The human body has an impressive arsenal of defenses against pathogens. But bacteria and viruses are wily opponents, and tackling the most dangerous ones has become a battle of wits--one in which scientists have had both stunning successes and frustrating defeats. They must remain vigilant: germs have plagued our species since its inception and they are here to stay.

Scientific American has long covered developments in the war on germs. In this exclusive online issue, prominent researchers and journalists discuss the new weapons of this war, such as virus-fighting drugs, edible vaccines and novel antibiotics; emerging enemies, such as anthrax and chronic wasting disease; and the all-too familiar foes HIV and hepatitis C. --The Editors

Beyond Chicken Soup The antiviral era is upon us, with an array of virus-fighting drugs on the market and in development. Research into viral genomes is fueling much of this progress (originally published November 2001)
Behind Enemy Lines A close look at the inner workings of microbes in this era of escalating antibiotic resistance is offering new strategies for designing drugs (originally published May 2001)
Edible Vaccines One day children may get immunized by munching on foods instead of enduring shots. More important, food vaccines might save millions who now die for lack of access to traditional inoculants (originally published September 2000)
The Unmet Challenges of Hepatitis C Some 1.8 percent of the U.S. adult population are infected with the hepatitis C virus, most without knowing it (originally published October 1999)
Attacking Anthrax Recent discoveries are suggesting much-needed strategies for improving prevention and treatment. High on the list: ways to neutralize the anthrax bacterium's fiendish toxin (originally published March 2002)
Shoot This Deer Chronic wasting disease, a cousin of mad cow disease, is spreading among wild deer in parts of the U.S. Left unchecked, the fatal sickness could threaten North American deer populations - and maybe livestock and humans (originally published June 2003)
Hope in a Vial Will there be an AIDS vaccine anytime soon? (originally published June 2002)
Forces of Nature
Introduction Earthquakes, volcanoes, tornadoes, hurricanes. For all the control humankind holds over its environment, sometimes Nature just can't be contained. Life on Earth has endured the mighty sting of these events since time immemorial but not without suffering devastating losses: the planet is rife with battle scars old and new telling tales of mass destruction.

Scientists may never be able to tame these thrilling and terrifying forces, but advances in understanding them are leading to ways to save lives. In this exclusive online issue, experts share their insights into asteroid impacts, tornado and hurricane formation, and earthquake prediction. Other articles probe the mysteries of lightning and contemplate the future of an increasingly menacing volcano.--The Editors

Repeated Blows Did extraterrestrial collisions capable of causing widespread extinctions pound the earth not once, but twice - or even several times? (originally published March 2002)
Mount Etna's Ferocious Future Europe's biggest and most active volcano is growing more dangerous. Luckily, the transformation is happening slowly (originally published April 2003)
Earthquake Conversations Contrary to prevailing wisdom, large earthquakes can interact in unexpected ways. This exciting discovery could dramatically improve scientists' ability to pinpoint future shocks (originally published January 2003)
Lightning Control with Lasers Scientists seek to deflect damaging lightning strikes using specially engineered lasers (originally published August 1997)
Lightning between Earth and Space Scientists discover a curious variety of electrical activity going on above thunderstorms (originally published August 1997)
Tornadoes The storms that spawn twisters are now largely understood, but mysteries still remain about how these violent vortices form (originally published August 1995)
Dissecting a Hurricane Flying into the raging tumult of Dennis, scientists suspected that the storm might transform into a monster - if they were lucky (originally published March 2000)
HIV: 20 Years of Research
Introduction Nearly 20 years ago researchers first identified HIV, the virus responsible for AIDS. Since then, scientists have made great strides in understanding how the virus operates and developing effective therapies. But vexing challenges to better treatment and prevention remain. And with 42 million people on the planet infected with HIV (more than three million died from it last year alone), fresh insights can't come fast enough.

Scientific American has regularly covered advances in HIV research. In this anthology of articles published over the past decade, leading authorities share their expertise on how HIV wreaks havoc on the body, how the government might stem the HIV epidemic among drug users who inject, and what sorts of treatments the future might bring. Other articles discuss the hunt for HIV-resistance genes and ponder the development of an HIV vaccine. --The Editors

AIDS and the Use of Injected Drugs The AIDS epidemic continues to grow among drug users who inject. It could be curbed if governments more readily adopted effective prevention programs (originally published February 1994)
How HIV Defeats the Immune System A plausible hypothesis suggests the immune devastation that underlies AIDS stems from continuous-and dangerous-evolution of the human immunodeficiency virus in the body (originally published August 1995)
The African AIDS Epidemic In parts of sub-Saharan Africa, nearly 25 percent of the population is HIV-positive as a result of heterosexual transmission of the virus. Could lack of circumcision make men in this region particularly susceptible? (originally published March 1996)
In Search of AIDS-Resistance Genes A genetic trait that protects against AIDS has now been uncovered, and others are emerging. The findings open entirely new avenues for developing preventives and therapies (originally published September 1997)
Improving HIV Therapy Today's optimal treatments can work magic, but they are costly and onerous and do not work for everyone. What might the future bring? (originally published July 1998)
Hope in a Vial Will there be an AIDS vaccine anytime soon? (originally published June 2002)
Prehistoric Beasts
Introduction Feathered dinosaurs, walking whales, killer kangaroos--these are but a few of the fantastic creatures that roamed the planet before the dawn of humans. For more than 200 years, scientists have studied fossil remnants of eons past, painstakingly piecing together the history of life on earth. Through their efforts, not only have long-extinct beasts come to light, but the origins of many modern animals have been revealed.

In this exclusive online issue, Scientific American authors ponder some of the most exciting paleontological discoveries made in recent years. Gregory Erickson reexamines T. rex and reconstructs how the monster lived. Ryosuke Motani describes the reign of fishlike reptiles known as ichthyosaurs. Kevin Padian and Luis Chiappe trace today's birds back to their carnivorous, bipedal dinosaur forebears. And Stephen Wroe presents the menacing relatives of Australia's beloved pouched mammals. Other articles document the descent of whales from four-legged landlubbers and recount the challenges and rewards of leading fossil-collecting expeditions to uncharted locales. --The Editors

Breathing Life into Tyrannosaurus rex By analyzing previously overlooked fossils and by taking a second look at some old finds, paleontologists are providing the first glimpses of the actual behavior of the tyrannosaurs (originally published September 1999)
The Teeth of the Tyrannosaurs Their teeth reveal aspects of their hunting and feeding habits (originally published September 1999)
Madagascar's Mesozoic Secrets The world's fourth-largest island divulges fossils that could revolutionize scientific views on the origins of dinosaurs and mammals (originally published February 2002)
Rulers of the Jurassic Seas Fish-shaped reptiles called ichthyosaurs reigned over the oceans for as long as dinosaurs roamed the land, but only recently have paleontologists discovered why these creatures were so successful (originally published December 2000)
The Origin of Birds and Their Flight Anatomical and aerodynamic analyses of fossils and living birds show that birds evolved from small, predatory dinosaurs that lived on the ground (originally published February 1998)
The Mammals That Conquered the Seas New fossils and DNA analyses elucidate the remarkable evolutionary history of whales (originally published May 2002)
Killer Kangaroos and Other Murderous Marsupials Australian mammals were not all as cute as koalas. Some were as ferocious as they were bizarre (originally published May 1999)
Tackling Major Killers - Heart Disease
Introduction How are your New Year's resolutions holding up? Make sure that moderating your drinking, quitting smoking and getting more exercise top the list. Such lifestyle changes go a long way towards warding off heart disease, one of the leading causes of death among adults around the world. In the meantime, medical researchers continue to gain more insight into what directly causes heart disease--discoveries that are helping them develop more effective treatments.

In this exclusive online issue, Peter Libby explains the latest ideas about how blood vessels deteriorate in the case of atherosclerosis, and Rakesh K. Jain and Peter F. Carmeliet describe how, by manipulating angiogenesis, or the formation of new blood vessels, researchers may find drugs to treat the condition. Alternatively, other authors explore the history of defibrillation; operations to treat cardiac arrhythmias; new procedures for coronary bypass surgery; and, when all other interventions have failed, the use of artificial hearts.--The Editors

The Trials of an Artificial Heart A year after doctors began implanting the AbioCor in dying patients, the prospects of the device are uncertain (originally published July 2002)
Operating on a Beating Heart Coronary bypass surgery can be a lifesaving operation. Two new surgical techniques should make the procedure safer and less expensive (originally published October 2000)
Surgical Treatment of Cardiac Arrhythmias To save the life of a doomed patient, the author and his colleagues developed a now standard surgical procedure for correcting lethally fast heartbeats in many people susceptible to them (originally published July 1993)
Defibrillation: The Spark of Life In the 50 years since doctors first used electricity to restart the human heart, we have learned much about defibrillators and little about fibrillation (originally published June 1998)
Atherosclerosis: The New View It causes chest pain, heart attack and stroke, leading to more deaths every year than cancer. The long-held conception of how the disease develops turns out to be wrong (originally published May 2002)
Vessels of Death or Life Angiogenesis - the formation of new blood vessels - might one day be manipulated to treat disorders from cancer to heart disease. First-generation drugs are now in the final phase of human testing (originally published December 2001)
The Search for Alien Life
Introduction Are we alone in the universe? It's a question that every school kid has probably asked at some time-and scientists in particular want an answer. In their quest after alien beings, astronomers have scanned the heavens for radio signals from another technologically advanced civilization; they've sent probes to all but one of the planets around our Sun; they've studied extreme life forms on Earth to better understand the conditions under which life can take root; and they've scrutinized the neighborhoods around distant stars.

We may never discover whether or not extraterrestrials exist-at least not until they contact us. But researchers continue to refine their search. Discoveries that water likely flowed on Mars at one time and that Jupiter's moon Europa may house a subterranean sea have intensified the hunt for alien organisms in our own solar system. And the identification of approximately 100 extrasolar planets in recent years has raised hopes of finding inhabited worlds similar to Earth elsewhere in our galaxy.

In this exclusive online issue, Scientific American authors review the evidence for and against the existence of ETs. In Where Are They?, Ian Crawford ponders what it means that all of our surveys so far have come up empty handed. In Is There Life Elsewhere in the Universe?, Jill C. Tarter, director of research for the Search for Extraterrestrial Intelligence (SETI) Institute, and her colleague Christopher F. Chyba assert that the search has only just begun. Other articles examine the cases to be made for relic life on Mars and other bodies in our solar system, as well as the plans to launch a new space telescope for spying on distant worlds. Buy the issue, read the articles and, the next time you gaze up at the night sky, make up your own mind. --The Editors

Where Are They? Maybe we are alone in the galaxy after all (originally published July 2000)
Is There Life Elsewhere in the Universe? The answer is: nobody knows. Scientists' search for life beyond Earth has been less thorough than commonly thought. But that is about to change (originally published December 1999)
Profile: Jill C. Tarter, An Ear to the Stars Despite long odds, astronomer Jill C. Tarter forges ahead to improve the chances of picking up signs of extraterrestrial intelligence (originally published November 2002)
Searching for Life in Our Solar System If life evolved independently on our neighboring planets or moons, then where are the most likely places to look for evidence of extraterrestrial organisms? (originally published in Magnificent Cosmos-Spring 1998)
Searching for Life on Other Planets Life remains a phenomenon we know only on Earth. But an innovative telescope in space could change that by detecting signs of life on distant planets (originally published April 1996)
The Case for Relic Life on Mars A meteorite found in Antarctica offers strong evidence that Mars has had - and may still have - microbial life (originally published December 1997)
The Science of War: Nuclear History
Introduction "The unleashed power of the atom has changed everything save our modes of thinking, and thus we drift toward unparalleled catastrophes," Albert Einstein wrote in 1946. Indeed, the development of nuclear weapons utterly transformed human warfare, as the mass destruction wreaked by bombs dropped on Japan a year earlier made chillingly clear. Yet devastating though the outcomes often were, this was a time of extraordinary discoveries in the field of physics. Scientific American has long covered the science of war. Our first exclusive online issue housed a collection of articles about weapons. Now part two of our war anthology brings together recent contributions from experts on nuclear history.

In this issue, leading authorities discuss the science--and the scientists--that delivered us into the nuclear age, from Lise Meitner's long-overlooked contributions to the discovery of nuclear fission to Manhattan Project member Philip Morrison's reflections on the first nuclear war and how a second must be avoided. Other articles probe such topics as the contentious relationship between atomic bomb collaborators Enrico Fermi and Leo Szilard, a mysterious meeting between Werner Heisenberg and Niels Bohr, and the unlikely achievements of physicists in wartime Japan. --The Editors

Physicists in Wartime Japan During the most trying years of Japan's history, two brilliant schools of theoretical physics flourished (Originally published December 1998)
Recollections of a Nuclear War Two nuclear bombs were dropped on Japan 50 years ago this month. The author, a member of the Manhattan Project, reflects on how the nuclear age began and what the post-cold war future might hold (Originally published August 1995)
What Did Heisenberg Tell Bohr about the Bomb? In 1941 Werner Heisenberg and Niels Bohr met privately in Copenhagen. Almost two years later at Los Alamos, Bohr showed a sketch of what he believed was Heisenberg's design for a nuclear weapon (Originally published May 1995)
Lise Meitner and the Discovery of Nuclear Fission One of the discoverers of fission in 1938, Meitner was at the time overlooked by the Nobel judges. Racial persecution, fear and opportunism combined to obscure her contributions (Originally published January 1998)
The Odd Couple and the Bomb Like a story by Victor Hugo as told to Neil Simon, the events leading up to the first controlled nuclear chain reaction involved accidental encounters among larger-than-life figures, especially two who did not exactly get along - but had to (Originally published November 2000)
J. Robert Oppenheimer: Before the War Although Oppenheimer is now best remembered for his influence during World War II, he made many important contributions to theoretical physics in the 1930s (Originally published July 1995)
The Metamorphosis of Andrei Sakharov The inventor of the Soviet hydrogen bomb became an advocate of peace and human rights. What led him to his fateful decisions? (Originally published March 1999)
The Future of the Web
Introduction The dotcom bubble may have finally burst but there can be no doubt that the Internet has forever changed the way we communicate, do business and find information of all kinds. Scientific American has regularly covered the advances making this transformation possible. And during the past five years alone, many leading researchers and computer scientists have aired their views on the Web in our pages. Now you can access the majority of those contributions in a single place--our second exclusive online issue entitled The Future of the Web.

In this collection, expert authors discuss a range of topics--from XML and hypersearching the web to filtering information and preserving the Internet in one vast archive. Other articles cover more recent ideas, including ways to make Web content more meaningful to machines and plans to create an operating system that would span the Internet as a whole. --the Editors

Filtering Information on the Internet Look for the labels to decide if unknown software and World Wide Web sites are safe and interesting (Originally published in the March 1997 issue.)
Preserving the Internet An archive of the Internet may prove to be a vital record for historians, businesses and governments (Originally published in the March 1997 issue.)
Searching the Internet Combining the skills of the librarian and the computer scientist may help organize the anarchy of the Internet (Originally published in the March 1997 issue.)
XML and the Second-Generation Web The combination of hypertext and a global Internet started a revolution. A new ingredient, XML, is poised to finish the job (Originally published in the May 1999 issue.)
Hypersearching the Web With the volume of on-line information in cyberspace growing at a breakneck pace, more effective search tools are desperately needed. A new technique analyzes how Web pages are linked together (Originally published in the June 1999 issue.)
The Semantic Web A new form of Web content that is meaningful to computers will unleash a revolution of new possibilities (Originally published in the May 2001 issue.)
The Worldwide Computer An operating system spanning the Internet would bring the power of millions of the world's Internet-connected PCs to everyone's fingertips (Originally published in the March 2002 issue.)
The Science of War: Weapons
Introduction The art of war, according to Sun Tzu's 2,000-year-old text of the same name, is largely a matter of strategy, but the science of war begins squarely with weapons. Physics and engineering--and more often today, chemistry and biology--drive the creation of new military tools, from smart bombs and stealth aircraft to nerve gases and plastic explosives. Thus it is with a collection of articles about weapons that we are launching online a special anthology of Scientific American's recent coverage on war. In the Weapons issue, scientists share their expertise on one terror of the ancient battlefield, the trebuchet, as well as several modern-day scourges, including land mines, third world submarines and biological arms. Additional articles feature in-depth research by staff editors on more futuristic threats--in the form of swift subsea systems and so-called non-lethal weapons.
The Trebuchet Recent reconstructions and computer simulations reveal the operating principles of the most powerful weapon of its time (Originally published in the July 1995 issue)
Third World Submarines The proliferation of submarines may be a threat to established navies and regional stability, but to arms manufacturers it is a market opportunity (Originally published in the August 1994 issue)
The Horror of Land Mines Land mines kill or maim more than 15,000 people each year. Most victims are innocent civilians. Many are children. Still, mines are planted by the thousands every day (Originally published in the May 1996 issue)
The Specter of Biological Weapons States and terrorists alike have shown a growing interest in germ warfare. More stringent arms-control efforts are needed to discourage attacks (Originally published in the December 1996 issue)
Fighting Future Wars U.S. military planners hope to rely on improved versions of the technologies tested in the Gulf War to help fight the next Saddam Hussein. They may be preparing for the wrong conflict (Originally published in the December 1996 issue)
Warp Drive Underwater Traveling inside drag-cutting bubbles, secret torpedoes and other subsea naval systems can move hundreds of miles per hour (Originally published in the May 2001 issue)

Compiled by Dave Lo, article summaries © Scientific American