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

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

From the Editors; April 1998; Scientific American Magazine; by Rennie; 1 Page(s)

The laboratory is where it starts. Brilliant scientist (A) makes an important discovery. His loud cry of "Eureka!" startles sleep-deprived postdoctoral fellow (B), who drops a cage of laboratory mice (C). The animals, dizzy from running mazes, dash around the room, knocking experimental notes (D) onto the floor along with unfinished grant proposals, flyers for upcoming scientific meetings, the brilliant scientist's blurry vacation photographs, and a half-finished sandwich. Worried graduate student (E), acting on vaguely worded instructions from brilliant scientist, bundles all of the above into a large manila envelope (F) and mails it to Scientific American.

Upon arriving at our offices, the envelope is promptly opened by unpaid interns (G) who, desperate, eat the half-finished sandwich. The administrative staff (H) collects the rest of the contents and passes them to the editor in chief (I, that is, me), who immediately reaches for his large bottle of aspirin (J). The string attached to the aspirin bottle opens a valve on the coffeemaker (K), pouring a gallon of hazelnut Colombian directly into the waiting mouth of the article editor (L). Twitching with caffeine, that editor is now ready to begin her work.

Letters to the Editors; April 1998; Scientific American Magazine; by Staff Editor; 1 Page(s)

The skyscrapers of the 1930s (the Chrysler Building and the Empire State Building) were built just as the Great Depression took hold of the U.S. economy. The World Trade Center and Sears Tower were also leading indicators of the economic malaise of the 1970s. And just as Malaysia completes its showpiece, the Petronas Twin Towers (right) ["The World's Tallest Buildings," by Cesar Pelli, Charles Thornton and Leonard Joseph, December 1997], the economy of the region dives into disaster. In retrospect, this should be no surprise; during these periods, symbolism took great precedence over substance.

Had the Petronas Towers been built alongside the Sears Tower, those of us who actually worked on the 102nd floor of the Sears Tower would have laughed looking out at the pip-squeak spires of the new buildings. The Sears Tower is a building; the Petronas Towers are buildings with spires.

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

APRIL 1948 TECHNOLOGY TRANSFER--During the past two years, federal investigators have surveyed all German advances which could be of value to American industry. Their reports, available for the price of reproduction, contain descriptions of processes, equipment, formulas, plant layouts and other technical data. Many industries should benefit. For example, shops which do sheet metal stamping will be interested in a process for extruding cold steel, just as we extrude tin, zinc, copper and other non-ferrous metals.

NONINVASIVE MEASURES--A new X-ray gage measures the thickness of red-hot steel without physically contacting it in any way. The device shoots one X-ray beam through the hot steel strip as it moves off the finishing stands in a rolling mill. Simultaneously, a second X-ray beam from the same source penetrates a standard reference sample of a desired thickness. The instrument then compares the intensity of the two beams; a difference indicates that the strip is either more or less than the desired thickness.

In Focus: Lives in the Balance; April 1998; Scientific American Magazine; by Beardsley; 2 Page(s)

An estimated 16,000 people become infected with the human immunodeficiency virus (HIV) every day, according to the United Nations AIDS program, and 90 percent of them are in developing countries where antiviral drugs are unavailable. Although some candidate HIV vaccines made from noninfectious material do stimulate immune responses against the virus in laboratory tests, none has proved it can protect people from AIDS.

In desperation, researchers in Australia and in the U.S. are now pushing for clinical trials of vaccines that are essentially weakened yet still infectious forms of HIV. Within a couple of years, if plans move forward, HIV-negative volunteers in these countries will be vaccinated with an attenuated strain of either HIV itself or a "molecular clone," DNA that can establish a viral infection. The Chicago-based International Association of Physicians in AIDS Care had, as of February, lined up 276 HIV-negative volunteers who are at high risk of acquiring HIV and who are willing to be vaccinated. Charles F. Farthing, a physician who is volunteer number one and medical director of the AIDS Healthcare Foundation in Los Angeles, says, "I think the risk is very, very minimal, and that¿s what I want to prove."

Endangered; April 1998; Scientific American Magazine; by Gibbs; 2 Page(s)

Eighteen months after David S. McKay and his colleagues at the National Aeronautics and Space Administration Johnson Space Center raised eyebrows with their claim that a potato-shaped meteorite, dubbed ALH84001, contained microscopic fossils of ancient life from Mars, the team has made few converts. "There was a very quick division into a few groups that believed it and many more that didn¿t," recalls Allan H. Treiman of the Lunar and Planetary Institute in Houston. Since then, Treiman says, "I haven¿t seen anybody change their mind."

While McKay¿s team has spent much of the intervening months searching for bacteria on Earth that at least proves that the creatures they hypothesize are not impossible, its critics have published dozens of new observations they believe make that theory increasingly improbable, compared with nonbiological explanations for the meteorite¿s puzzling features.

Clock Setting; April 1998; Scientific American Magazine; by Hopkin; 3 Page(s)

Organisms from bread molds to bread makers rely on biological clocks that respond to light cues that help them synchronize their activities to the rising and setting of the sun. In humans, this circadian clock controls a variety of physiological processes, including daily rhythms in body temperature, hormone production and sleep itself. Now Scott S. Campbell and Patricia J. Murphy of Cornell University Medical College in White Plains, N. Y., report in Science that they can reset the master circadian clock in humans by shining a light not in the subjects¿ eyes but on the backs of their knees.

"The results are incredibly provocative," says Steve Kay of the Scripps Research Institute in La Jolla, Calif. "And very surprising," he adds, because previous studies in humans suggested that the light signals that entrain the body¿s clock travel to the brain via the retina.

Anti Gravity: Comic Relief; April 1998; Scientific American Magazine; by Mirsky; 2 Page(s)

Medical conventions are the last place one might expect to find clowns, other than speakers extolling the virtues of managed care. But on January 31, at the opening of the annual conference of the American Association for Therapeutic Humor (AATH), the clowns in attendance actually sported big, red noses.

They wore their red badges of courage proudly because these clowns work in hospitals, bringing some levity to the lives of sick kids, mostly, but also some adults. These genuine jesters were joined at the Washington, D.C., meeting by a few M.D.s, a smattering of psychologists, a bunch of social workers and a load of nurses to spread the word that while laughter might not be the best medicine, it was in fact pretty good medicine.

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

Hazy Findings When cars emit nitrogen oxides and volatile organic compounds in the summer, sunlight frequently mixes the two gases into a low-lying ozone smog that can choke people and kill plants. But apparently this photoreaction does not happen as often as scientists thought. Daniel J. Jacob and his colleagues at Harvard University recently examined ground-level ozone trends between 1980 and 1995 in three major U.S. cities: New York, Los Angeles and Chicago. They found that although the number of miles vehicles had traveled during the same period rose 60 percent, ozone concentrations showed a significant drop.

Cook Out . . . Way Out Strange dishes are coming from Cornell University kitchens of late. Scientists there are busy concocting recipes that can be easily prepared in space. To do so, they are limiting themselves to only 15 to 30 crops for ingredients. (After all, you cannot serve freeze-dried ice cream on a space station indefinitely.) Wheat and potatoes are the main staples, complemented with rice, soy, peanuts, salad crops and herbs. So far Cornell cooks have whipped up such culinary delights as carrot "drumsticks," tempeh sloppy joes and tofu cheesecake.

On Shaky Ground; April 1998; Scientific American Magazine; by Schneider; 2 Page(s)

For more than a decade, Panayiotis Varotsos, a solid-state physicist at the University of Athens, has attempted to predict earthquakes in Greece. His technique (dubbed VAN, after the last names of its three originators: Varotsos, Kessar Alexopoulos and Konstantine Nomicos) involves planting electrodes in the ground and extracting precursory electrical signals. By doing so, this researcher says, he can anticipate temblors weeks ahead. Although other scientists are also attempting to find links between low-frequency electromagnetic pulsations and subsequent earthquakes, only Varotsos has been bold enough to issue predictions on this basis. In January he and his colleagues explained some of the theory behind their method in the Journal of Applied Physics and were credited with predicting most major earthquakes in Greece in the pages of Physics Today. Such exposure lends credence to their approach, which relies on the earth¿s ability to transmit small electrical signals from stressed rocks over long distances. But does their prediction scheme truly have merit?

In fact, the performance of VAN is almost impossible to score. Some scientists who examined the question in detail in 1996 concluded that the forecasts had no predictive power. Others, such as Stephen K. Park, a geophysicist at the University of California at Riverside, who is trying to monitor electrical precursors to earthquakes in his home state, concluded that the Greek predictions were doing better than chance. Others said the warnings were so vague no objective test was even possible.

By the Numbers: Forest Density in the U.S.; April 1998; Scientific American Magazine; by Doyle; 1 Page(s)

As far back as the Civil War, Americans were concerned that the forests were being destroyed by logging and the conversion of woodland to farms. There was talk of an impending "national famine of wood," and indeed the facts must have seemed discouraging at a time when wood was the chief source of energy. In the late 19th century there was little prospect of a major expansion of prime cropland needed to feed a population that was increasing by more than 20 percent per decade. But the ecological crisis that loomed never came. Forest acreage stopped declining about 1920 because there was little need for additional farms. In fact, forests in many parts of the Northeast and the South have actually expanded since 1900, as agriculture shifted to the Midwest. The need for new farm acreage diminished partly because the use of crops to feed draft animals declined steeply with the introduction of tractors and other motorized equipment. And the productivity of farms rose as a result of genetically improved strains, increased use of fertilizers and better irrigation.

Forests also recovered as coal and oil replaced fuelwood, and conservation measures begun in the era of President Theodore Roosevelt and his chief of the forest service, Gifford Pinchot, started to take effect. Pollution by pulp and paper mills was cut drastically, and tree planting increased. Although population has grown by 2.5 times in the past 80 years, forests have been able to satisfy the rising demand for lumber, paper and other wood products.

Profile: An Ethnologist in Cyberspace; April 1998; Scientific American Magazine; by Holloway; 2 Page(s)

Beep. "At a certain point you want to kill it," says Sherry Turkle, pressing the tiny buttons of her daughter¿s virtual pet. Beep. Like many mothers the world over, Turkle is sometimes enslaved to a demanding electronic toy while her six-year-old is away at school. Beep, bleats the little plastic object. More buttons pushed. Turkle feeds it. Cleans up after it. Tends to it. Beep. But the dinosaurlike critter inhabiting the gray screen wants more of everything. "Because it is young, it needs attention every minute," Turkle sighs. "That is part of the deal."

Sitting at the kitchen counter, surrounded by her daughter¿s handmade books--which have bright-colored paper covers, a page or two of text or illustration and titles such as "Soccer Is for Boys: Fiction"--Turkle sketches the brief history of electronic toys. The professor of sociology at the Massachusetts Institute of Technology describes how digital devices used to be targeted solely at boys and how, in many ways, these video games taught them to be comfortable with computers. Now, as Tamagotchis, the most famous brand of virtual pet, become the rage for girls, the lessons are shifting. "The transition is from objects-to-think-with to objects-to-nurture," Turkle explains. "The new hook for these kids, and not just for kids, is nurturance instead of control and mastery."

Not What the Doctor Ordered; April 1998; Scientific American Magazine; by Nemecek; 2 Page(s)

Richard Laing studies the international drug trade. But instead of monitoring the latest cocaine shipment from Colombia, he is watching to see who is sending antibiotics to Africa. Laing, a professor of International Public Health at Boston University, is one of many observers concerned about the types of supplies pharmaceutical companies ship to needy countries. Too often these drugs are inappropriate and even dangerous. "The problem is very widespread," Laing says, "and there is lots of money involved-- the value of these medications is in the hundreds of millions of dollars."

Although by and large drug donations serve a vital need, every year or so a donation gone awry makes headlines. Antibiotics from Eli Lilly and Company that were not approved for use by either the U.S. Food and Drug Administration or the World Health Organization (WHO) were sent to Rwanda in 1994. In 1993, 11 Lithuanian women went temporarily blind after taking a veterinary medicine, made by Janssen Pharmaceutica, that doctors thought was a treatment for endometriosis--because the drugs were shipped with no instructions. In 1990, when Sudan was suffering from the ravages of war and famine, various companies sent donations of contact lens solution, appetite stimulants, expired antibiotics and drugs to treat high cholesterol.

Taking on the Energizer Bunny; April 1998; Scientific American Magazine; by Hayashi; 1 Page(s)

Batteries are a notorious weak link for many portable devices, such as laptop computers and cellular phones. They are expensive, heavy and cumbersome, often requiring recharging at the most inopportune times. Recent advances in fuel-cell technology might bring relief. Several research groups are developing "micro-fuel cells" that could, for example, result in mobile phones running continuously for weeks on standby power.

Fuel cells are simple devices, basically consisting of a nonmetallic conductor called an electrolyte sandwiched between two electrodes. Hydrogen from a fuel, such as methanol, flows through the electrolyte to mix with an oxidizer, such as oxygen from air, and the chemical reaction produces an electric current between the two electrodes. The cells can be replenished easily--and quickly-- by adding more fuel. Fuel cells also run cleanly, their main by-product being water from the combination of hydrogen and oxygen, whereas batteries, which eventually wear out from repeated recharging, present a disposal problem.

Fertilizing the Sea; April 1998; Scientific American Magazine; by Nadis; 1 Page(s)

Give me a half-tanker of iron, and I¿ll give you an ice age," said the late oceanographer John H. Martin, referring to the concept of stimulating the growth of phytoplankton by adding iron to ocean water. According to this scheme, which has been called the "Geritol solution" to global warming, the newly spawned microscopic plants would draw carbon dioxide from the atmosphere to support photosynthesis and carry carbon to the deep sea after they died.

While putting it less brashly, Michael Markels wants to apply the same principles, not only to alleviate the buildup of greenhouse gases but also to establish fisheries in otherwise nutrient-poor waters. Markels, a chemical engineer who founded the McLean, Va.-based company Ocean Farming, Inc. (OFI), literally wants deserts to bloom at sea. "The oceans, for the most part, are a great barren wasteland: 60 percent of the plant life comes from just 2 percent of the surface," he says. "Fertilization is required to make the barren parts more productive."

A New Fat Pipe; April 1998; Scientific American Magazine; by Zorpette; 1 Page(s)

In the high-stakes struggle to make the Internet more mainstream, one monumental challenge has loomed from the very beginning. That problem is replacing the thin "soda straws" through which data get to most home users with big "fat pipes."

Until a few months ago, the only fat pipes that seemed to have a reasonable chance of succeeding were cable television lines, converted to convey data through cable modems. Recently, however, three computer giants--Compaq Computer, Intel and Microsoft--threw their considerable weight behind the only real competitor to cable modems. The fat-pipes sweepstakes has become a bona fide race.

Cyber View; April 1998; Scientific American Magazine; by NA; 1 Page(s)

Today is a black day for anyone associated with alt.fan.unabomber," wrote one member of an Internet newsgroup¿s mailing list on January 22. That¿s when Theodore Kaczynski finally agreed to plead guilty to all federal charges for the bombings, which killed three people and seriously injured two others. "[We] will lose the chance of seeing Kaczynski attempt to sell his anti-technology views to a jury," the posting continued.

The writer, like many others, spoke with regret. On the Net, Kaczynski¿s political ideas have received a fairly respectful airing. His 35,000-word manifesto, entitled "Industrial Society and Its Future," has been widely quoted, its philosophy--the author calls for a revolution against the industrial system, arguing that it has been a "disaster for the human race"--debated with some seriousness. There were the inevitable jokes: "A 17-year reign of terror?" one correspondent wrote of the Unabomber¿s time at large. "Maybe the real terror is having to read his sophomoric essay." But in general Kaczynski¿s writing drew considerable interest and discussion, particularly among anarchists, antitechnologists, radical environmentalists and others inclined toward his notion that "the time is ripe for the presentation of anti-industrial ideas."

Cosmic Antimatter; April 1998; Scientific American Magazine; by Tarlé, Swordy; 6 Page(s)

In 1928 the English physicist P.A.M. Dirac predicted the existence of antimatter. Dirac claimed that for every particle of ordinary matter there was an antiparticle with the same mass but an opposite charge. These antiparticles could join to form antiatoms, and the antiatoms could form antimatter counterparts to every object in the universe-- antistars, antigalaxies, even antihumans. What is more, if a particle of matter collided with a particle of antimatter, they would both be annihilated in an energetic burst of gamma rays. If a human and an antihuman shook hands, the resulting explosion would be equivalent to 1,000 one-megaton nuclear blasts, each capable of destroying a small city.

It was an extraordinary proposition. The theory was confirmed just four years later, when Carl D. Anderson, a physicist at the California Institute of Technology, detected the first antiparticle. While using a cloud chamber to study cosmic rays--high-energy particles that bombard the earth from space--Anderson observed a vapor trail made by a particle with the same mass as an electell much about the origins of antimatter. They may also indicate whether antistars and antigalaxies really exist.

Post-Polio Syndrome; April 1998; Scientific American Magazine; by Halstead; 6 Page(s)

In the first half of the 20th century, the scourge of paralytic poliomyelitis seemed unstoppable. A major polio epidemic hit the New York area in 1916, and in the following decades the epidemics grew in size and became more deadly. The epidemic of 1952, for instance, affected more than 50,000 Americans and had a mortality rate of about 12 percent. It is difficult to realize today the extent of the fear and panic that gripped the public. Polio haunted everyone: families stayed at home; swimming pools were closed; public events were canceled.

Children in particular were at risk. With the introduction of Jonas E. Salk¿s injected killed-virus polio vaccine in 1955 and Albert B. Sabin¿s oral live-virus vaccine six years later, the epidemics were brought to an end. By the mid- 1960s the number of new polio cases dropped to an average of 20 a year. Polio had been vanquished. Or so it seemed.

Science in Pictures: The Earliest Views; April 1998; Scientific American Magazine; by Ford; 4 Page(s)

In 1674 Antony van Leeuwenhoek peered through one of his homemade microscopes and discovered a new and entrancing universe. The Dutch amateur scientist was staring at slime he had collected from the surface of a lake when he suddenly saw unknown organisms: "I saw so many little animalcules and the motion of them in the water was so swift, and so various, upwards, downwards and round about, that it was wonderful to see."

Leeuwenhoek, who lived from 1632 to 1723, had inadvertently launched the field of microbiology. Working in an era before the science of optics really flourished, Leeuwenhoek himself constructed more than 500 microscopes. Using these basic instruments, he recorded--in addition to the "animalcules," or microbes--many cellular structures as well as the existence of red blood cells and spermatozoa. He also described bacteria, protozoa, rotifers, plant cells and fungi.

How Females Choose Their Mates; April 1998; Scientific American Magazine; by Dugatkin, Godin; 6 Page(s)

Picture a man who has a way with the ladies, and a character not unlike James Bond may spring to mind. He's clever, classy, fearless and flashy--characteristics that are almost universally appealing to the opposite sex. Throw in the powerful sports car, and you have a nearly irresistible combination.

That females often flock to the most ostentatious males is not a phenomenon unique to humans. In many different species, successful males--those that sire the most offspring--are often larger or more brightly colored or "show off" with more vigorous courtship displays.

Laser Scissors and Tweezers; April 1998; Scientific American Magazine; by Berns; 6 Page(s)

The intense, pure beams of light known as lasers are now standard components of such commonplace objects as compact-disc players and printers. The everyday presence of lasers does not mean, however, that they have been reduced to performing only pedestrian tasks. Imagine focusing a beam specifically onto an organelle, a structure within a living cell. Consider further that the beam can actually grasp that minuscule entity and hold it in place. Now imagine that while this "microbeam" acts as tweezers, a second beam serves as scalpel or scissors to conduct delicate surgery on the organelle.

Even in a world accustomed to lasers, such musings have the ring of science fiction. Nevertheless, much as medical surgeons guide micromachined tweezers and scissors through endoscopes to perform minimally invasive surgery on organs, the cell biologist can now use "laser tweezers" and "laser scissors" to perform minimally invasive manipulations on living cells and their organelles.

Wireless Technologies; April 1998; Scientific American Magazine; by Staff Editor; 1 Page(s)

Today¿s wireless systems would be unrecognizable to Guglielmo Marconi, who invented the wireless telegraph in 1896. Four decades ago the solid- state revolution started to bring ever smaller and higherperformance radios and televisions into millions of homes. Now we can slip either one into a jacket pocket and still have room for a cell phone. Satellites continually beam television and voice signals around the earth.

Yet even more radical developments are in store. This special report details how a new generation of satellites and high-altitude platforms will form a global cellular network providing first voice and then high-speed data links to portable terminals anywhere. Together with handheld wireless computers and ground-based networks, these technologies will put civilization¿s collection of digital knowledge at our fingertips whenever we want. They will make us more secure and keep us close to those we need to be in touch with. Marconi¿s legacy is a liberating gift.

New Satellites for Personal Communications; April 1998; Scientific American Magazine; by Evans; 8 Page(s)

Since the first commercial model was launched into orbit in 1965, the communications satellite has become a linchpin of global communications. From modest beginnings--that first satellite could handle only 240 voice circuits at a time--the technology has blossomed to the extent that satellites now carry about one third of the voice traffic between countries and essentially all the television signals between countries.

Much of the voice traffic handled by satellites, however, is to countries that have no access to fiber-optic cables, which are the preferred medium for carrying telephone calls. Because large communications satellites are typically put into geosynchronous orbits, where they are roughly 36,000 kilometers (22,300 miles) above the same spot on the earth at all times, it takes a quarter of a second for signals to travel to and from the satellite, delaying the responses received during a conversation. Although not all users find this delay irritating, communications satellites are increasingly being used to carry television signals and data rather than voice traffic.

Telecommunications for the 21st Century; April 1998; Scientific American Magazine; by Pelton; 6 Page(s)

Space-based telecommunications systems will change our lives over the next two decades, providing rapid access to information of all types, from handheld or briefcase-size terminals anywhere on the planet. Mass virtual-reality entertainment, videos on demand and expanded telehealth and tele-education services are just some of the developments we can expect to arrive with this torrent of data--along with mounting information overload and the 168-hour workweek.

In five years¿ time there will very likely be 1,000 commerical communications satellites in service, up from about 220 today. Many of these switching stations in the sky will zoom in low earth orbit (LEO) only a few hundred kilometers overhead. But satellites in the more traditional geosynchronous earth orbit (GEO), which turn with the earth 36,000 kilometers (22,300 miles) up, will remain very much in the picture.

Terrestrial Wireless Networks; April 1998; Scientific American Magazine; by Hills; 6 Page(s)

In the past decade, cellular phones have gone from being a rarity to being commonplace. More than 50 million Americans, one in five, use these devices; one in six uses a wireless pager. In developing countries where standard telephone service is not universally available, cellular is often seen as a better alternative to conventional wired service, because wireless systems can be built quickly. Clearly, if a communications service can be made portable, convenient and affordable, demand is great.

Consumers and businesses have been much slower to adopt wireless systems for data communications than for telephone service. (Paging barely scrapes the surface of wireless¿s potential.) In the U.S., data communications have been estimated to account for only 3 percent of wireless traffic with mobile terminals, and the proportion is probably even less in most other countries. One explanation for this imbalance between voice and data services is that wireless telephone service has been available to consumers for longer than wireless data-- since the early 1980s. And long before that, people in industrial countries were already accustomed to using telephones. Widespread use of computers, in contrast, is fairly recent, and so applications for wireless data links are much less mature.

Moving beyond Wireless Voice Systems; April 1998; Scientific American Magazine; by Stutzman, Dietrich; 2 Page(s)

Over the next few decades, the increasingly integrated network of terrestrial and satellite-based radio systems will grow to meet the rising demand for fast, mobile communications. Desire for simple wireless conversations first spurred the construction of this infrastructure, but many other uses are emerging. Primary among these are capabilities for determining the position of a person or object and for monitoring devices at a distance.

Until recently, such applications might have sounded as though they would be helpful only to professional navigators, surveyors or technicians. But wireless technology is so versatile--and the systems so compact and inexpensive because of advances in electronics and computing--that it can benefit even routine aspects of daily life, such as driving across town or protecting a house from burglars.

Spread-Spectrum Radio; April 1998; Scientific American Magazine; by Hughes, Hendricks; 3 Page(s)

Conventional wisdom holds that radio airspace is a valuable--and limited--resource that has to be rationed, like water in a desert. That mind-set comes from traditional transmitters and receivers, whose operation must be restricted to narrow, dedicated slices of the electromagnetic spectrum to minimize interference. Thus, governments have parceled out and licensed radio channels like real estate. In the U.S., the Federal Communications Commission (FCC) has sometimes used a cash-bidding process to allocate precious frequency bands for a variety of purposes, including commercial television and radio broadcasts; military, marine and police transmissions; taxi dispatchers; CB communications; and ham radio operators and cell phone consumers.

Recent advances in digital communications, though, have opened the door to an entirely new model. Transmitters can now deploy so-called spread-spectrum techniques to share channels without running afoul of one another. Information can be diced into tiny electronic bundles of 1s and 0s and then transmitted over radio waves, with each packet sent over different channels, or frequencies, at low power. New studies have shown that, theoretically, millions of radio transmitters within the same metropolitan area can successfully operate in the same frequency band while transferring hundreds of megabits of data per second.

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

Every creature on the earth lives under the warm, nurturing and protective blanket formed by the atmosphere. Yet all this air does more than trap the sun's heat and carry gases between plants and animals. It also presses down on our world with powerful force. At sea level, a single sheet of writing paper, when laid flat, sustains 6,111 newtons--about 1,400 pounds.

One might imagine that such a burden would stress living creatures enormously. But far from hurting organisms, the weight of the atmosphere proves absolutely essential for life. Liquid water could not exist on the earth were not atmospheric pressure sufficient to keep it from boiling rapidly away. And many vital biological processes, cellular respiration chief among them, fail if the air pressure falls too low.

Mathematical Recreations; April 1998; Scientific American Magazine; by Stewart; 3 Page(s)

Suppose I keep tossing a fair coin-- one for which heads and tails are equally likely, each having probability 1/2--and maintain a running count of how many times each turns up. If at some stage I have tossed 100 more heads than tails, is there any tendency for tails to "catch up" in future tosses? Some people talk of a law of averages, based on the intuition that tosses of a fair coin ought to even out ultimately. Others assert that coins have no "memory"-- so the probability of heads or tails always remains 1/2--and deduce that there is no tendency whatsoever for the numbers to even out.

The same issues arise in diverse circumstances. If airplane crashes happen on average once every four months and three months have passed without one, should you expect one soon?

Commentary: Wonders - The Timekeeping ELF; April 1998; Scientific American Magazine; by Morrison; 2 Page(s)

Since the rise of the medieval city, the mechanical clock and its progeny have increasingly ordered our comings and goings. The year marks the sun¿s apparent path and the seasons it rules, the month makes a rather mannered bow to the moon¿s real form and presence, and the day carries the certainties of darkness and light. The fleeting second, without our quite realizing it, paces the most intimate of human rhythms, the quick heartbeat. Neither the hour nor the minute hand has much to do with any natural phenomenon.

Years ago a noontime ball would drop down some flagpole at every busy harbor so that ships¿ navigators might check their timekeeping. That performance was a marine necessity, for 10 seconds of clock error carried a penalty of three miles (five kilometers) lost. Nowadays fewer clocks are seaborne. My ingenious friend Giuseppe Cocconi, long a particle physicist in Geneva, Switzerland, tells of one time and place when that shift began to be manifest. With World War II just over, the thrifty captains of coastwise cargo vessels and offshore fishing boats grasped that radio signals and radio beams had come to displace the long reign of the chronometer. Ships¿ fine chronometers began to fill the pawnshop shelves in Italian port cities at unheard-of bargains.

Commentary: Connections - Sheer Poetry; April 1998; Scientific American Magazine; by Burke; 2 Page(s)

Iwas reading the poem on the base of the Statue of Liberty recently and thinking how often the best-laid plans get hit by Murphy¿s Law. In 1871 France had just lost a war to the Prussians and were beginning the soon-tobe- familiar pattern of governments imitating cuckoo clocks (in and out, on the hour). In the politically unstable climate of the times, yo-yoing between monarchy, revolutionary terror and moderate republicanism, those partial to the last were eager to find some way of warding off a return of the old guard.

A gigantic statue--to be built by the French, dedicated to republican ideals and erected in New York Harbor (the gateway to the nation whose independence the French had bankrolled a century earlier)-- would remind any French citizen wishing to go back to the bad old days of the link between the two countries and of France¿s natural republicanism. A good plan, it would seem, but 15 years later this political ploy had been thwarted by the no-fool Americans. Thanks to Emma Lazarus¿s ode to America, engraved on the monument¿s pedestal, the Statue of Liberty was, already at its inauguration in 1886, perceived to be less an acknowledgment of the debt to France and more an exclusively American statement of the country¿s open-door policy to immigrants (even to those escaping persecution in France).

Working Knowledge; April 1998; Scientific American Magazine; by Goldberg; 1 Page(s)

In recent years the international epidemic of embedded schmutz has captured the attention of the scientific and public health communities. Researchers discovered that persistent topical contact with common foodstuffs presents a grave health threat. Studies found that the random graham cracker crumb or the milk mustache can lead to a markedly diminished use in human populations of the oscultatory appendage--referred to in the scientific literature simply as kissy lips. In seeking to counter this imminent danger to the continued survival of the species, public health officials launched a worldwide campaign to seek technology that would automate the osculatory decontamination process.

The global search led to the discovery of the self-operating napkin. The idea can be attributed to one anonymous but heavily mustachioed academic. This estimable professor happened to be walking barefoot in his sleep on the first day of April. Upon contact with the thorns of a cactus, the good professor immediately awoke and screamed out the idea for his invention.