Cover; September 1998; Scientific American Magazine; by Staff Editor; 1 Page(s)

Table of Contents; September 1998; Scientific American Magazine; by Staff Editor; 2 Page(s)

From the Editors, including Masthead; September 1998; Scientific American Magazine; by Rennie; 1 Page(s)

Letters to the Editors; September 1998; Scientific American Magazine; by Staff Editor; 2 Page(s)

50, 100 and 150 Years Ago; September 1998; Scientific American Magazine; by Staff Editor; 1 Page(s)

SEPTEMBER 1948 THE TRANSISTOR APPEARS--Within the past few months a group of physicists at the Bell Telephone Laboratories has made a profound and simple finding. In essence, it is a method of controlling electrons in a solid crystal instead of in a vacuum. This discovery has yielded a device called the transistor (so named because it transfers an electrical signal across a resistor). Not only is the transistor tiny, but it needs so little power, and uses it so efficiently (as a radio amplifier its efficiency is 25 per cent, against a vacuum tube¿s 10 per cent) that the size of batteries needed to operate portable devices can be reduced. In combination with printed circuits it may open up entirely new applications for electronics.

PRIMARY CARE--Primitive medicine men learned long, long ago what modern medicine is just rediscovering--that distinctions between the mind and the body are artificial. The primitive doctor understands well the nature of psychogenic illness. Among pre-literate peoples, as among those in more civilized societies, these emotional discomforts are easily translated into neurotic symptoms. This illustration shows a sand painting made by a Navaho medicine man, designed to treat mind and body in a curing ceremony. The painting is made on the floor of a hut, the patient is laid upon it and paint is rubbed over him.

In Focus: Forestalling Violence; September 1998; Scientific American Magazine; by Nemecek; 2 Page(s)

Heading back to school brings to mind shiny new notebooks, multicolored pens, the latest clothes and some free time for parents. This fall, however, parents, teachers and students have an additional concern: school shootings. Although only 1 percent of all homicides-- and suicides--of school-age children in the U.S. occur on school grounds, this statistic represents a dramatic increase. According to a survey by the National School Safety Center (NSSC), the number of violent deaths in schools rose 60 percent last year to a total of 41, nearly half of which were multiple shootings. Experts worry that an epidemic of school violence is under way. As Ronald D.Stephens, executive director of the NSSC, describes it, there have been attempted cases of "copycat killings," particularly after the shootings in March at a Jonesboro, Ark., middle school that killed four students and a teacher.

Anxious to stop this trend, teachers and administrators around the country have embraced a variety of preventive techniques--everything from metal detectors to daily classes in controlling anger. But in many instances, these programs have not been graded for efficacy. Even more troubling is the fact that, according to recent studies, certain popular methods simply do not work.

Herb Remedy; September 1998; Scientific American Magazine; by Stix; 2 Page(s)

The exact location is a secret. But somewhere between London and Brighton a compound ringed by high fences and razor wire will house the world¿s only pot farm primarily devoted to commercial drug development. In June the British Home Office gave a startup pharmaceutical company a license to grow 20,000 marijuana plants of varied strains.

Geoffrey W. Guy, chairman of GW Pharmaceuticals, intends to proceed to clinical trials with a smokeless, wholeplant extract, while also supplying marijuana to other investigators interested in medical research and pharmaceutical development. The 43-year-old entrepreneur- physician wants to capitalize on what he sees as the unexploited opportunity to legitimize marijuana as medicine. "Cannabis has been much maligned," Guy says. "There are over 10,000 research articles written on the plant, and there¿s something well worth investigating here."

Stalking the Wild Dugong; September 1998; Scientific American Magazine; by Mukerjee; 2 Page(s)

From the porch where I am slumped, exhausted by the heat, I stare in astonishment at a man walking up the forest trail from the beach, snorkel dangling from one hand. I have just arrived at Dugong Creek, a remote corner of Little Andaman Island in the Bay of Bengal, to meet the Onges, a group of hunter-gatherers believed to be descended from Asia¿s first humans. I hadn¿t expected to find other visitors.

"You know there are crocodiles," I say, indicating his snorkel. "A hazard of the trade," he grins. Himansu S. Das of the Salim Ali Center for Ornithology and Natural History in Coimbatore, India, is a sea-grass ecologist. Because dugongs, Old World relatives of the manatee, feed on underwater greenery, he had guessed that Dugong Creek would have beds of sea grass nearby. The animals themselves, though, were likely to be long gone. Once seen in the hundreds or even thousands along the tropical coasts of Africa and Asia, these sea elephants are all but extinct in most of their range and occur in reasonable numbers only in Australia. In five years of exploration, Das has gathered evidence of at most 40 dugongs throughout the Andaman and Nicobar archipelago. To his surprise, he has just learned from the Onges that a family of four still lives in Dugong Creek, down one since their hunt of two weeks ago.

The Flip Side of the Universe; September 1998; Scientific American Magazine; by Musser; 1 Page(s)

Late into the night astronomers Angelica de Oliveira-Costa and Max Tegmark worked to analyze their observations of the cosmic microwave background radiation. The next morning the young wife-and-husband team were due to present what their data revealed about the single most important unknown fact in cosmology: the shape of the universe. Their previous results, from a telescope in Saskatoon, Canada, between 1993 and 1995, had suggested that the universe is flat-- the first observations to substantiate a long-held belief among cosmologists. But intrinsic uncertainties in the measurements made it impossible to be sure.

So in 1996 the QMAP team (de Oliveira- Costa, Tegmark and five colleagues from the Institute for Advanced Study in Princeton, N.J., and the University of Pennsylvania) flew instruments on a balloon 100,000 feet (30 kilometers) above Texas and New Mexico. When they finally processed the data--the night before their announcement at the Fermi National Accelerator Laboratory this past May--the situation looked grim. The Saskatoon and the balloon results were completely different.

In Brief; September 1998; Scientific American Magazine; by Leutwyler; 3 Page(s)

Alexander¿s Fate An ancient conspiracy theory held that rivals poisoned Alexander the Great, who died unexpectedly at the age of 32 in 323 B.C. But a new analysis, published in the New England Journal of Medicine on June 11, finds otherwise: Alexander probably fell victim to typhoid fever. The authors-- including infectious- disease expert David W. Oldach of the University of Maryland and historian Eugene N. Borza of Pennsylvania State University-- were puzzled by historical accounts stating that Alexander¿s body did not begin to decay for days after his death. They believe he most likely succumbed to ascending paralysis, a complication of typhoid fever that can slow down a person¿s breathing and make them look dead.

Science Knowledge Interest in science is at an all-time high, according to a survey of 2,000 U.S. adults that was presented to Congress in July. But basic knowledge remains poor. Jon D. Miller, director of the International Center for the Advancement of Scientific Literacy, conducted the survey for the National Science Foundation last year. Although 70 percent of the subjects said they were curious about science and technology, only 11 percent could define "molecule," half believed that humans and dinosaurs had at one time coexisted, and only 48 percent knew that the earth orbits the sun once every year.

Anti Gravity: Tomorrow, Partly Froggy; September 1998; Scientific American Magazine; by Mirsky; 1 Page(s)

Television evangelist and sometime presidential candidate Pat Robertson recently shocked the world by revealing that a science existed that he knew even less about than paleontology. Delving into the latter discipline, Robertson once contended that "there is no case where we have remains or fossils of an animal that died during the evolutionary process." In fact, every fossil ever found is of an organism that died during the "evolutionary process." But I digress. In June, Robertson added meteorology to the list of sciences about which he has theories-- and few facts.

The self-appointed forecaster took to the airwaves to warn residents of Orlando, Fla., about wicked weather possibly headed in their direction. Orlando stood in the way of some righteous wrath, he maintained, as a result of the city¿s decision to allow gay organizations to fly rainbow flags in a local celebration called Gay Days. "This is not a message of hate; this is a message of redemption," he insisted. "But if a condition like this will bring about the destruction of your nation, if it will bring about terrorist bombs, if it will bring about earthquakes, tornadoes and possibly a meteor, it isn¿t necessarily something we ought to open our arms to. And I would warn Orlando that you¿re right in the way of some serious hurricanes, and I don¿t think I¿d be waving those flags in God¿s face if I were you."

A World Aflame; September 1998; Scientific American Magazine; by Nemecek; 1 Page(s)

Every year fire scorches some 71 million hectares (175 million acres) of forest and grassland. In 1997 drought brought on by El Ni¿o exacerbated fires, many of which were deliberately set, the world over. In Indonesia, for instance, the devastation was particularly extreme because of the worst drought the country had seen in 50 years. According to the World Wildlife Fund¿s 1997 report The Year the World Caught Fire, Indonesia lost two million hectares to flame. A satellite image from last year shows the extent of the damage (red in image at right). A composite of data from 1992 to 1995 (at left) shows fires in the region in red and purple. Fires this year in the Amazon, Mexico, Florida and elsewhere promise to make 1998 another record year

The National Aeronautics and Space Administration has teamed up with the National Oceanic and Atmospheric Administration to provide weekly updates on fires around the world. Information can be found at http:// modarch.gsfc.nasa.gov/fire_ atlas/fires.html on the World Wide Web.

River of Vitriol; September 1998; Scientific American Magazine; by Ariza; 2 Page(s)

Against the dark stand of pine trees, the waters of the Rio Tinto appear even more vividly red than usual. Here, near its headwaters in southwest Spain, the strong smell of sulfur overwhelms even the fragrance of the dense forest. The crimson river--infamous for its pH of two, about that of sulfuric acid, and for its high concentration of heavy metals--seems dead, a polluted wasteland and a reminder of the ecological devastation mining can entail.

Yet the remarkable Rio Tinto is hardly lifeless, as scientists have discovered in the past several years. Even in parts of the river where the pH falls below two-- and the water is painful to touch--green patches of algae and masses of filamentous fungi abound. "Each time we go there we find something new," says Ricardo Amils, director of the laboratory of applied microbiology at the Center for Molecular Biology at the Autonomous University in Madrid, who discovered the river¿s wild ecosystem in 1990. "We have now collected about 1,300 forms of life living here, including bacteria, yeast, fungi, algae and protists. But the real number is surely much higher."

By the Numbers: Ethnic Groups in the World; September 1998; Scientific American Magazine; by Doyle; 1 Page(s)

Many of the world¿s problems stem from the fact that it has 5,000 ethnic groups but only 190 countries. This situation is illustrated on the map, which shows that few states are ethnically homogeneous and that many, particularly in Africa, have no majority ethnic group. Since 1945 some 15 million people have been killed in conflicts involving ethnic violence, although ethnic tensions have not necessarily been the catalyst. Among the worst incidents were the 1994 civil war in Rwanda, which resulted in more than a million dead and three million refugees, and the 1947 communal riots in India, which left several hundred thousand dead and 12 million refugees.

Why are some multiethnic countries plagued by violent, persistent ethnic conflict and others not? There are no completely satisfactory answers, but it is evident that several factors affect the outcome. One of these is the presence or absence of political institutions that give minorities protection against the tyranny of majority rule. Federal systems, such as the one instituted after 1947 in India, can help dampen ethnic tensions by giving minorities regional autonomy. Intermarriage-- between Thais and Chinese in Thailand, say, or Taiwanese and Mainlanders in Taiwan--erodes ethnic differences. And free-market forces tend to mitigate ethnic tensions. For instance, Russia has not adopted an irredentist policy-- there are nearly 25 million Russians in neighboring republics-- arguably because it would interfere with the goal of achieving a Western-style market economy.

Profile: Riding the Back of Electrons; September 1998; Scientific American Magazine; by Stix; 2 Page(s)

In 1952 a young physicist visited an aging industrial building in Poughkeepsie, N.Y., that its owners called the "pickle works." The trim 25- year-old was looking for a new position after becoming disenchanted with his two-year-old job at the National Advisory Committee for Aeronautics (predecessor of the National Aeronautics and Space Administration), where he had some involvement with a project to build a nuclear-powered jet aircraft.

IBM, the company he was visiting, had just made the onerous transition from computing machines that used electromechanical relays to those that incorporated vacuum tubes. Even then, it was looking warily ahead. The company needed physicists as part of a small semiconductor research team, established to guard against the unlikely possibility that transistor technology would ever amount to anything. "The future of IBM is in semiconductors, and they don¿t even know it," confided the manager who conducted the interview.

The Reinvention of Paper; September 1998; Scientific American Magazine; by Gibbs; 2 Page(s)

Twenty years ago Nicholas K. Sheridon got his big idea, the kind that scientists--if they are talented and fortunate--get just once or twice in a career. Sheridon hit on a way to draw images electronically that would be far more portable than heavy cathode- ray tubes, far cheaper than liquidcrystal panels. In theory, his invention could bring to digital displays many of the advantages of paper. They would be thin and flexible yet durable. They would consume only tiny amounts of power yet would hold images indefi- nitely. They could be used for writing as well as reading, and they could be reused millions of times. Yet they would be as cheap as fine stationery. Sheridon named his idea Gyricon, and he applied for and received a patent on it.

But there his good fortune failed him. Twenty years ago Sheridon¿s managers at the Xerox Palo Alto Research Center were sitting on many of the inventions that would eventually propel the personal computing revolution: the windows and mouse interface, the laser printer, Ethernet. Like those innovations, Gyricon drew only yawns from Xerox¿s blinkered managers. "The boss said, ¿Xerox really isn¿t interested in displays. Why don¿t you work on printing technologies?¿ So I did," Sheridon recalls.

Healing Cancer; September 1998; Scientific American Magazine; by Gibbs; 2 Page(s)

If all goes as expected, the first vaccine against cancer will be approved for sale before the end of September. The vaccine will neither prevent cancer nor cure it, and it would first be sold in Canada, not the U.S. It will be a significant event nonetheless, because it will demonstrate that a longheld dream--of attacking cancer by guile from within, rather than assaulting the body by brute force from without-- is beginning to come true.

More than half a dozen large-scale tests of cancer vaccines are under way in clinics around the world. Most aim at the same malignancy as this first drug: melanoma, a fast-spreading skin cancer that strikes about one person in 100. Ribi ImmunoChem Research, a biotech firm in Hamilton, Mont., was simply the first to file for market approval. European regulators are also evaluating the company¿s clinical results, and Ribi plans to put its new medicine, Melacine, before U.S. Food and Drug Administration reviewers later this year.

The Dope on Holography; September 1998; Scientific American Magazine; by Beardsley; 1 Page(s)

The burgeoning demand for storing colossal amounts of digital data has spurred academic and industrial researchers to seek new memory technologies. One promising idea, dating from the 1970s, is to use holograms: "frozen" interference patterns created by lasers. A thumb-tipsize block of the right material can potentially store holograms representing thousands of billions of data bits, thereby offering a much greater density of information than do today¿s data storage devices. Moreover, holograms can be read very quickly. So far, though, holographic memory has not become commercially viable. But recent efforts by a group at the California Institute of Technology may soon change all that.

Until now, the technology has been dogged by a key disadvantage: holograms tend to be "volatile." In other words, reading them quickly degrades their content. A hologram is created when two laser beams--one of which encodes data--interfere with each other. The interference pattern created by the beams is captured as electric fields in a susceptible material--for example, lithium niobate that has been doped with a tiny amount of some other metal. To read the hologram, a single laser beam is shone at it; the hologram then diffracts the light in a pattern that holds the stored data. But the laser light also "washes out" the hologram as it illuminates it.

Cyber View; September 1998; Scientific American Magazine; by Grossman; 1 Page(s)

If the frustrations of all the world¿s computer users were brought together, the resulting explosion would make the big bang look like a Roman candle. This is true even though computers have come a long way in the decade since the industry pronounced "usability" a necessity. Nevertheless, we still have a plethora of frustrating functions: inconsistent commands (drag a file in Windows, for instance, and you could end up moving it, copying it or perhaps even creating a link back to it from another directory--who knows?), programs that rename files according to their tastes instead of yours, "help" screens that explain options but not what they mean or what their consequences are, and inscrutable error messages. Home systems--such as Windows 95 or 98--hide their inner workings from users, whereas professional systems--such as Windows NT--keep those inner workings accessible but design them only for experts.

Nowhere, it seems, is there a system designed for people who know how to use a computer but aren¿t techies. I fall in that category, and the upshot is that I spend some part of every day in an absolute rage at the bozos who designed the computer I live with, which is refusing to let me do one or another simple thing.

Preserving the Laetoli Footprints (Part 1); September 1998; Scientific American Magazine; by Agnew, Demas; 6 Page(s)

One of the most remarkable events in the annals of anthropology occurred 20 years ago in an area of northern Tanzania called Laetoli. A team led by famed archaeologist Mary D. Leakey was searching for fossils of the early hominids that ranged through East Africa millions of years ago. In the summer of 1976, after a long day in the field, three visitors to Leakey¿s camp engaged in some horseplay, tossing chunks of dried elephant dung at one another. When paleontologist Andrew Hill dropped to the ground to avoid getting hit, he noticed what seemed to be animal tracks in a layer of exposed tuff--a sedimentary rock created by deposits of volcanic ash. On closer inspection of the area, the scientists found thousands of fossilized tracks, including the footprints of elephants, giraffes, rhinoceroses and several extinct mammal species. But the most extraordinary find came two years later, when Paul I. Abell, a geochemist who had joined Leakey¿s team, found what appeared to be a human footprint at the edge of a gully eroded by the Ngarusi River.

Excavations of the Footprint Tuff-- as it came to be known--in 1978 and 1979 revealed two parallel trails of hominid footprints extending some 27 meters (89 feet). The volcanic sediments were dated radiometrically to be between 3.4 million and 3.8 million years old. The discovery settled a long-standing scientific debate: the Laetoli footprints proved that early hominids were fully bipedal--they had an erect posture and walked on two feet--long before the advent of stone toolmaking or the expansion in size of the human brain. What is more, the trackway provided information about the soft tissue of the hominids¿ feet and the length of their strides--information that cannot be ascertained from fossil bones. For these reasons, the Laetoli footprints attracted a huge amount of attention from scientists and the general public. Leakey, who died in 1996, regarded the discovery as the crowning achievement of her six decades of work in East Africa.

Preserving the Laetoli Footprints (Part 2); September 1998; Scientific American Magazine; by Agnew, Demas; 6 Page(s)

Fieldwork on the Laetoli footprints ended with the 1979 season, and Leakey¿s team used local river sand to rebury the site. Because the tuff is soft and easily damaged, the mound of sand was covered with volcanic boulders to armor it against erosion and the animals that sometimes roam across the site--particularly elephants and the cattle of the Masai people living in the area. We now know that seeds of Acacia seyal, a large, vigorously growing tree species, were inadvertently introduced with the reburial fill. The loose fill and the physical protection and moisture retention provided by the boulders created a microenvironment conducive to germination and rapid plant growth. Over the following decade, the acacias and other trees grew to heights of over two meters. Scientists who occasionally visited the Laetoli site began to voice concern that the roots from these trees would penetrate and eventually destroy the hominid footprints.

In 1992 the Antiquities Department of the Tanzanian government approached the Getty Conservation Institute, which has extensive experience in preserving archaeological sites, to consider how the trackway might be saved. The following year a joint team from the institute and the Antiquities Department excavated a sample trench in the reburial mound to assess the condition of the hominid footprints. The assessment revealed that tree roots had indeed penetrated some of the tracks. But in the areas where no root damage had occurred, the preservation of the prints was excellent. Leakey¿s intuitive decision to rebury the site had been the right one. With hindsight we can now say that perhaps greater care should have been taken in how the site was buried. Also, periodic monitoring and maintenance--including the removal of tree seedlings before they became established--would have avoided the need for a long and costly conservation effort.

The Footprint Makers: An Early View; September 1998; Scientific American Magazine; by Matternes; 1 Page(s)

Iworked on my painting of the Laetoli footprint makers during the early fall of 1978, shortly after the discovery of the hominid trackway. As part of my research, I flew to Africa to confer with Mary Leakey and her associates at their base camp in Tanzania¿s Olduvai Gorge. When I boarded the plane, the only information I had on the project consisted of a few photographs of the footprints and the surrounding area, along with a report on the geology of the Laetoli site and a list of the animal tracks found there.

While at the base camp, I consulted with Leakey and made a number of drawings of proposed layouts. She drove me to Laetoli so I could familiarize myself with the main features of the terrain. The analysis of the Laetoli sediments indicated that there had been several types of volcanic ashfalls in the area--some settling undisturbed on the ground, some redeposited by wind--but all the ash had come from the Sadiman volcano. Geologists believe the color of this ash was light gray, not very different from the color of the hardened tuff in which the footprints were discovered.

The Laetoli Diorama; September 1998; Scientific American Magazine; by Tattersall; 1 Page(s)

Only very rarely does the fossil record provide evidence of an actual event in human prehistory. So in the late 1980s, when we were considering subjects for presentation in diorama form in the American Museum of Natural History¿s Hall of Human Biology and Evolution, the making of the Laetoli footprints seemed an obvious choice. Constructing lifelike sculptures of extinct humans involves many tricky decisions [see "Evolution Comes to Life," by Ian Tattersall; SCIENTIFIC AMERICAN, August 1992]. The decisions involving the Laetoli hominids were particularly difficult because the 3.6-million-year-old creatures are so remote from modern-day humans. Our Laetoli diorama posed an additional problem: it was designed to represent a specific event--the journey of the hominids across a plain of volcanic ash--but the evidence from that event is a little ambiguous.

Willard Whitson, the museum hall¿s designer, and I visited the Laetoli site in Tanzania and discussed our plans for the diorama with Peter Jones, an archaeologist who was part of Mary Leakey¿s team when the trackway was discovered in 1978. We also consulted paleoanthropologist Ron Clarke, who excavated many of the footprints. Nobody disputes that the two parallel trails were made by beings who were walking bipedally (although they may have been tree climbers as well). The footprints in the westernmost trail were much smaller and more clearly defined than the prints in the eastern trail, but Jones pointed out that the stride lengths were the same. Clearly, the hominids were walking in step and accommodating each other¿s stride--which meant that the two trails were made at the same time. What is more, the trails are so close together that the hominids must have been in some kind of physical contact when they made them.

Weightlessness and the Human Body; September 1998; Scientific American Magazine; by White; 6 Page(s)

When a healthy Valeri Polyakov climbed out of his Soyuz capsule on March 22, 1995, after a world-record 438 days on the Mir space station, he had demonstrated that humans can live and work in space for months at a time. It was not always clear that this would be the case.

In 1951, more than 10 years before Yuri Gagarin¿s first short flight (108 minutes), Scientific American published an article by Heinz Haber of the U.S. Air Force School of Aviation Medicine that anticipated many of the medical effects of space travel and, in particular, of weightlessness [see "The Human Body in Space," January 1951]. Some of his predictions, such as the occurrence of space motion sickness at the beginning of a flight, have been borne out. Others, such as the notion that space travelers would feel as if they were being jerked back and forth or that they would suddenly start to spin around during normal motion in space, have not.

Attention-Deficit Hyperactivity Disorder; September 1998; Scientific American Magazine; by Barkley; 6 Page(s)

As I watched five-year-old Keith in the waiting room of my of- fice, I could see why his parents said he was having such a tough time in kindergarten. He hopped from chair to chair, swinging his arms and legs restlessly, and then began to fiddle with the light switches, turning the lights on and off again to everyone¿s annoyance-- all the while talking nonstop. When his mother encouraged him to join a group of other children busy in the playroom, Keith butted into a game that was already in progress and took over, causing the other children to complain of his bossiness and drift away to other activities. Even when Keith had the toys to himself, he fidgeted aimlessly with them and seemed unable to entertain himself quietly. Once I examined him more fully, my initial suspicions were confirmed: Keith had attention-deficit hyperactivity disorder (ADHD).

Since the 1940s, psychiatrists have applied various labels to children who are hyperactive and inordinately inattentive and impulsive. Such youngsters have been considered to have "minimal brain dysfunction," "brain-injured child syndrome," "hyperkinetic reaction of childhood," "hyperactive child syndrome" and, most recently, "attention-deficit disorder." The frequent name changes re- flect how uncertain researchers have been about the underlying causes of, and even the precise diagnostic criteria for, the disorder.

Making New Elements; September 1998; Scientific American Magazine; by Armbruster, Hessberger; 6 Page(s)

You can call it a gamble: there¿s just a narrow path to reach our goal--or to miss it. In this spirit, we start an experiment to make new, superheavy elements. These elements have to be produced in a lengthy, complicated procedure in which we smash atomic nuclei into one another at very high speeds and hope they undergo fusion. The resulting products will be extremely fragile, and most will break apart immediately.

Only under very extraordinary conditions will a new element have a chance to survive the production process and land in a stable configuration--what we call the ground state. But even when these conditions are met, the production rate of a new element is tiny. To make element 112, the heaviest artificial element produced to date, we conducted an around-the-clock experiment for 24 days and created only two atoms of 112, which lasted for only microseconds.

The Evolution of the Periodic System; September 1998; Scientific American Magazine; by Scerri; 6 Page(s)

The periodic table of the elements is one of the most powerful icons in science: a single document that consolidates much of our knowledge of chemistry. A version hangs on the wall of nearly every chemical laboratory and lecture hall in the world. Indeed, nothing quite like it exists in the other disciplines of science.

The story of the periodic system for classifying the elements can be traced back over 200 years. Throughout its long history, the periodic table has been disputed, altered and improved as science has progressed and as new elements have been discovered.

The Oort Cloud; September 1998; Scientific American Magazine; by Weissman; 6 Page(s)

It is common to think of the solar system as ending at the orbit of the most distant known planet, Pluto. But the sun¿s gravitational influence extends more than 3,000 times farther, halfway to the nearest stars. And that space is not empty--it is filled with a giant reservoir of comets, leftover material from the formation of the solar system. That reservoir is called the Oort cloud.

The Oort cloud is the Siberia of the solar system, a vast, cold frontier filled with exiles of the sun¿s inner empire and only barely under the sway of the central authority. Typical noontime temperatures are a frigid four degrees Celsius above absolute zero, and neighboring comets are typically tens of millions of kilometers apart. The sun, while still the brightest star in the sky, is only about as bright as Venus in the evening sky on Earth.

Thermophotovoltaics; September 1998; Scientific American Magazine; by Coutts, Fitzgerald; 6 Page(s)

Photovoltaics is a technology that typically transforms sunlight into electricity. Radiation from the visible part of the spectrum is, after all, abundant, nonpolluting and free. But photovoltaics can also provide useful amounts of electricity from infrared radiation-- that is, radiant heat generated by a source of energy such as fuel oil.

This lesser-known approach, called thermophotovoltaics, offers a major advantage in certain settings: a generator can operate at night or when the sky is overcast, thereby eliminating any need for batteries to store electricity. The technology is also preferable in some ways to conventional electricity-generating technology based on burning fossil fuels. Its efficiency--the percent of fuel energy converted to electricity--can be substantially higher than that of electric generators powered by natural gas or another fossil fuel. Moreover, a semiconductor- based thermophotovoltaic system can be designed to minimize pollutants. And because it contains no moving parts, it will run silently and reliably, requiring little maintenance.

The Amateur Scientist; September 1998; Scientific American Magazine; by Carlson; 2 Page(s)

If you're a man who's looking to get married, here's some friendly advice. Only consider women who are smarter than you are. I followed this prescription four years ago when I married Michelle Tetreault, a charming and brilliant biophysicist. Now my wife always intrigues me with her insights and never lets me get away with anything dubious at home.

At work Michelle employs the latest techniques in biochemistry to unravel the secrets of photosynthesis. By manipulating the smallest units of inheritance, the individual base pairs on a single strand of DNA, she can change one by one the amino acids that make up a key protein and then study how well this altered molecule can do its job.

Mathematical Recreations; September 1998; Scientific American Magazine; by Stewart; 2 Page(s)

The pyramids of ancient Egypt rank among the most enigmatic of archaeological mysteries. The largest, the Great Pyramid at Giza, was built by Egyptian king Khufu in about 2500 B.C. and is still mostly intact. Its original height was almost 147 meters (482 feet), and it weighed more than seven billion kilograms (7.7 million tons). The pyramid was made from huge blocks of stone, which were quarried, trimmed to a fairly regular shape, transported to the construction site and then piled on top of one another with astonishing precision.

How did the Egyptians put together such giant edifices? And why were they built? Historians and archaeologists do not know for certain. Many pyramids were used as tombs for kings, and there are plenty of theories about their construction. And now historians can make a good guess at the size of the workforce, thanks to some mathematical detective work by Stuart Kirkland Wier, an amateur Egyptologist who belongs to a study group sponsored by the Denver Museum of Natural History. His calculations appeared in the Cambridge Archaeological Journal (April 1996).

Reviews; September 1998; Scientific American Magazine; by Albers; 2 Page(s)

Sixty-one years ago W. W. Norton and Company published Lancelot Hogben¿s Mathematics for the Million, one of the truly great popularizations of this century. It has sold more than 600,000 copies and is still selling thousands of copies a year. With the publication of Jan Gullberg¿s Mathematics: From the Birth of Numbers, Norton seems to have done it again. The book is an enthusiastic and utterly amazing popularization that promises to be in print for decades. After 18 months, it is in its sixth printing.

The two books have much in common. Both were written by nonmathematicians: Hogben was a zoologist and Gullberg a surgeon. Neither was an American, but each ended up being published by an American company. Both saw mathematics as a social equalizer and essential for helping the masses to escape control by society¿s "clever people"--mathematicians, scientists and government officials. Both authors richly appreciated the historical development of mathematics.

Commentary: Wonders - A Minor Shift in Point of View; September 1998; Scientific American Magazine; by Morrison, Morrison; 2 Page(s)

Scientists have discovered some eight or 10 planetary systems beyond our own. So far the homiest example attends a dim, single star in the constellation of Ursa Major, the Great Bear. That sunlike star is designated as 47 Uma, entered long ago as just one more star by the first ever astronomer royal, John Flamsteed. (You can see it on a clear, dark night, as one of a sprinkle of faint stars. Extend the line of the Pointers backward from the North Star by about three times the sky separation between the two Pointers to find the little grouping.)

The distance of 47 Uma from Earth, about 45 light-years, is known by trigonometric measurement; from its spectrum we find that it is nearly the size and mass of our sun, though somewhat older, brighter and hotter. An unseen giant planet circles 47 Uma every 1,100 days: a super-Jupiter, yet too faint for the best telescopes. Our indirect evidence is compelling; tiny, elliptical motions of that sun-star in response to the wide swing of its planet have been mapped in detail since 1990. Alas, we lack the sensitivity to detect any sun¿s minute response to an Earth-like orbiter, which would be hundreds of times lighter than a giant gas planet.

Commentary: Connections - Rebellious Affiars; September 1998; Scientific American Magazine; by Burke; 2 Page(s)

Iwas in one of London¿s oldest coffeehouses the other day, sipping a cup (of Folger¿s, as it happens) and thinking about the first such watering holes. Like the one in St. Paul¿s churchyard, where those who supported the American colonists¿ cause used to meet and greet during the 1760s. One such dangerous coffee-drinking liberal was mathematician Richard Price, who put actuarial studies on a modern basis with his analysis of the Northampton Bills of Mortality. From which he was able to deduce life-and-death matters well enough for the new insurance firms to be able to charge realistic premiums and not go broke before their clients did.

Price¿s statistical work attracted the French finance minister, Anne-Robert- Jacques Turgot, who had the unenviable task of balancing the books at a time when the French economy was heading rapidly toiletward. A pal and adviser to Turgot was the Marquis de Condorcet, whose claim to fame was the way he took the new statistical view of things to the next stage and invented what he called "social mathematics." Thus armed, he intended to predict all aspects of behavior and thereby set the study of society onto a scientific footing.

Working Knowledge; September 1998; Scientific American Magazine; by Pohlmann; 1 Page(s)

The release of the compact disc and its player in 1982 revolutionized the audio world by introducing optical digital technology. Unlike the analog format of the oldfashioned LP record, in which a stylus traces a groove pressed into the record¿s surface, a CD player retrieves data by shining a focused laser beam on the underside of the disc. Because nothing except light touches the disc, playing a CD causes no more wear to the recording than reading does to the words printed on this page. Furthermore, the audio quality of a CD is extremely high, and any part of the disc can be accessed quickly for playback.

When music is recorded digitally, sound is sampled and represented as a series of numbers that measure the amplitude of the source signal. Thousands of numbers are needed to describe even a brief sound. These numbers are encoded in binary form (as strings of 0s and 1s) and stored in the form of microscopic pits and smooth areas called lands on the disc¿s data surface. During playback, the CD player¿s laser light reflects back from the rotating disc at varying intensities as it strikes the pits and lands. A photodiode array detects these fluctuations, which are then translated into 0s and 1s. This binary stream is decoded through demodulation and error correction and converted back into a variable electric signal, which is amplified and played through headphones or loudspeakers.