Cover; August 2000; Scientific American Magazine; by Staff Editor; 1 Page(s)

Table of Contents; August 2000; Scientific American Magazine; by Staff Editor; 2 Page(s)

From the Editors, including Masthead; August 2000; Scientific American Magazine; by John Rennie; 2 Page(s)

Letters to the Editors; August 2000; Scientific American Magazine; by Staff Editor; 2 Page(s)

50, 100 and 150 Years Ago; August 2000; Scientific American Magazine; by Staff Editor; 1 Page(s)

WORLD FOOD-"The food problem confronts the world with two dangers. One is the political danger of hunger. A lifetime of malnutrition and hunger is the lot of two thirds of mankind. Yet in the midst of this dire need there remains the economic threat of the food surpluses generated by modern technologies. The abundant food output of the U.S. already has begun to undermine its prosperity. A World Food Board, as an agency of the U.N., would be responsible for maintenance of stable world prices, and would arrange for disposal of surpluses.-John Boyd-Orr, winner of the Nobel Peace Prize in 1949" [Editors' note: The World Food Board was never created.]

ULTRASONIC NAVIGATION-"Photographs of the wave-form of bats' ultrasonic sounds, as seen on the cathode-ray oscilloscope, show that a typical ultrasonic cry lasts only for about one five-hundredth of a second. An audible sound of this extreme brevity is heard as a sharp click. The frequency always seems to drop at least an octave from the beginning to the end of the pulse. Observations show that bats can use pulses of ultrasonic sound to detect objects as close as six inches. Under these conditions an echo will return to the bat's ears before the pulse can finish leaving its mouth. It would seem easier for a bat to distinguish between echo and original pulse if the two differed in frequency, as they do."

Uncontrolled Burn; August 2000; Scientific American Magazine; by Marguerite Holloway; 2 Page(s)

The Cerro Grande fire in New Mexico was stunningly damaging for a prescribed burn. It raged for more than two weeks, consuming some 50,000 acres of national forest and land on and around Los Alamos National Laboratory. It destroyed 230 or so homes, displaced thousands of people, came perilously close to hazardous-materials sites on the nuclear-weapons research facility, scorched precious habitat for the threatened Jemez Mountains salamander and, some have speculated, may have played a role in the mysterious movements of Los Alamos hard drives containing classified material. And the danger posed by the fire has not subsided with the flames. Not only is the lab still vulnerable to ignition because of adjacent unburned forests, but the land is littered with plutonium and other dangerous waste that may be dispersed into the environment if the heavy seasonal rains cause mud slides and flooding.

Yet the blaze may have some positive effects. Perhaps most notably, it has renewed needed discussion about several challenges facing the federal agencies that manage land: the poor health of the national forests, the lack of man power and expertise needed to start and extinguish fires, and the paucity of research on the relative benefit or appropriateness of various approaches-logging, mechanical thinning and controlled burns-to restoring the forests. It has done so at a significant political juncture. Two proposals are now before Congress: one that would ban logging in national forests and one from the Clinton administration urging an end to construction of new roads on those same lands. Both policies, if enacted, could have important consequences for the use of fire in land management.

Island Survivors; August 2000; Scientific American Magazine; by Eric Niiler; 3 Page(s)

GUADALUPE ISLAND, MEXICO-"Vermin. Rats with horns. Evil," Jon P. Rebman tells me as we hike across this rugged volcanic island about 150 miles west of Mexico's Baja California peninsula. "I could keep going. They've really eaten nearly everything."

Rebman, curator of botany at the San Diego Natural History Museum, is referring to the some 10,000 goats that have transformed the lush forest of Guadalupe Island into a barren field since they were introduced by sailors some 150 years ago. Now he and his colleagues are searching for the few remaining endemic plants that may have escaped the marauding herd.

Gene Scenes; August 2000; Scientific American Magazine; by Trisha Gura; 1 Page(s)

CLEVELAND-Imagine that you are an alien commissioned to decipher a football game. Equipped with nothing more than a Polaroid camera and a truckload of film, could you accurately explain the sporting event given that, to your otherworldly sensibilities, the halftime show carries just as much importance as the kickoff? That scenario depicts the challenge facing researchers who track cells during the development of embryos and tumors. Outfitted with scalpels and microscopes, investigators must try to explain the workings of biology by killing embryos or removing tissue samples, fixing them on slides and piecing together the "snapshots" taken over time. And there is no way to tell what is meaningful to the game and what is halftime fluff.

Chemist Thomas J. Meade and his colleagues at the California Institute of Technology may have found the engineering equivalent of a video camera and an on-field microphone. This past May at a National Academy of Engineering meeting in Cleveland, Meade unrolled stunning videos of frog embryos unfolding from egg to tadpole stages. With unprecedented detail and cellular-level resolution, the images showed the creatures' cells at work communicating with one another during development.

Magnetic Anomalies; August 2000; Scientific American Magazine; by George Musser; 1 Page(s)

The next time you visit deep space, don't forget to pack a compass. It might not be much use for navigation, but it will be one of the few ways you can take in one of space's sublimities, the magnetic fields. The lines of magnetic force twist and wind through the interstellar miasma and arch over millions of light-years of intergalactic wilderness. They are, astronomers have gradually realized, one of the great shaping forces of the universe. Now it seems that even the outermost of outer space-the chasms between clusters of galaxies-is pervaded by magnetic fields of unforeseen power and unknown origin. "These magnetic fields are the dominant free energy of the universe," says astrophysicist Stirling A. Colgate of Los Alamos National Laboratory.

Magnetism had long been considered a side attraction in astronomy-hard to measure, hard to master, seemingly easy to neglect. The basic trouble is that the fields are invisible. To infer their presence, astronomers must make do with such compasses and filings as nature has haphazardly provided, including dust grains and charged particles. By aligning dust grains or diverting the paths of electrons, for example, a magnetic field can effect the emission of polarized radio waves or skew the polarization of light passing through a region of space, rather like a weak pair of polarizing sunglasses.

Global Positioning; August 2000; Scientific American Magazine; by Kate Wong; 1 Page(s)

Scientists have long known that hominids arose in Africa, and for the first few million years they stayed there. But at some point our ancestors began to move out of their motherland, marking the start of global colonization. Determining why and when they left, however, has proved difficult because of the scarcity of early human fossils. Now two ancient skulls from the Republic of Georgia provide the strongest evidence yet of the first humans to journey out of Africa. According to a report in the May 12 Science, they appear to have accomplished this far earlier-and with a much more modest technology-han many investigators had expected.

Researchers unearthed the skulls in Dmanisi, about 85 kilometers southwest of the Georgian capital, Tbilisi. Based on radiometric dating of the volcanic layer underlying the fossils, paleomagnetic measurements and the presence of animal species whose age has been documented elsewhere, the team dated the skulls to around 1.7 million years ago-at least 300,000 years older than stone tools from a site in Israel called 'Ubeidiya that were considered the oldest undisputed traces of humans outside Africa.

More Than the Best Medicine; August 2000; Scientific American Magazine; by Meredith F. Small; 1 Page(s)

ITHACA, N.Y.-Psychologist Jo-Anne Bachorowski of Vanderbilt University has learned an important lesson from her research on laughter: "I know now to snort and grunt only with friends but never around men I want to impress." Bachorowski, her Vanderbilt colleague Moria Smoski and Michael J. Owren of Cornell University have tested how men and women respond to and use laughter. They have discovered that the quality of a laugh can make someone more or less attractive. More interesting, other people in the room affect how much, and in what form, someone laughs. Women laugh more wildly around male strangers, but men laugh most with their buddies. And these differences, the researchers suggest, make evolutionary sense.

In one experiment, subjects listened to recorded laughs and were asked to "rate" the sound: Would they like to meet the laugher? Unvoiced laughs-like that of your friend who opens his mouth, rocks back and forth, and pants like a hyena-failed to attract any interest. Snorters and grunters, especially women, were also not high on anybody's list. But the woman with the singsong laugh, well, she could have a date every night. Such women were rated as even friendlier and sexier than men with the same kind of laugh.

By the Numbers: The U.S. Population Race; August 2000; Scientific American Magazine; by Rodger Doyle; 1 Page(s)

In the standard demographic scheme, population change results from three forces: births, deaths and migration. In the period 1970-1999 the U.S. saw about 110 million births and 63 million deaths, a natural increase of 47 million. Domestic migration was far greater: there were 425 million occasions in which Americans moved to another county in the same state or to a different state altogether. (The more than 750 million occasions in which Americans moved within counties are not reflected in the map.) The 38 million who migrated to the U.S. from abroad had a small effect overall on the redistribution of population, except in a few areas such as New York City.

Technology and the economy, of course, largely govern regional migration. The long-term decline of population in the Buffalo and Pittsburgh regions traces mostly to the crisis in heavy manufacturing of the 1980s. Because other industries could not absorb the laid-off workers, many job seekers relocated, particularly the young. Those who stayed, being older, had fewer children. The demographic shock was so great that populations in these areas are still about 15 percent below 1970 levels.

News Briefs; August 2000; Scientific American Magazine; by Julia Karow, Diane Martindale, George Musser, Sarah Simpson, Steve Mirsky; 2 Page(s)

When the trash collector doesn't come, the waste may become dangerous to health. A similar negligence might cause the severe autoimmune disease systemic lupus erythematosus, which affects more than one million people in the U.S. When a body cell dies, a crew of proteins quickly chops it up and clears the remnants. But if molecules such as DNA are left behind, antibodies can develop against them and lead to inflammation.

To test if failure to remove the DNA from dead cells can alone elicit lupus, researchers from the universities of Essen and Bochum in Germany, led by Tarik Moroy, created mice lacking the DNA-clearing enzyme called Dnase-1. In the June issue of Nature Genetics they report that after six to eight months, some of these genetically engineered mice had indeed developed antibodies against DNA and a form of kidney inflammation common in lupus. Because Dnase-1 activity is also low in lupus patients, treating them with the enzyme might improve their condition.-Julia Karow

Profile: Inventor of the Blue-Light Laser and LED, Shuji Nakamura; August 2000; Scientific American Magazine; by Glenn Zorpette; 2 Page(s)

SANTA BARBARA, CALIF.-I press a button on the pocket light-emitting diode tester, and three specks of plastic and semiconductor shoot out blue and green rays intense enough to hurt my eyes. The two blue devices emit a furious cerulean with the slightest hint of violet. The green is sharp and rich-not that ghastly yellowish hue that had to do if you wanted a "green" LED until recently. Until, that is, the man who is grinning at me, Shuji Nakamura, got some very bright ideas.

Nakamura, the newest addition to the engineering faculty at the University of California at Santa Barbara, stunned colleagues late in 1999, when he revealed that he was leaving Nichia Corporation, a once obscure Japanese maker of phosphors for cathode-ray tubes and fluorescent lights. Thanks to Nakamura, Nichia now fabricates the world's best blue and green LEDs and the only commercially available blue-violet semiconductor lasers. At a time when invention is dominated by faceless teams at huge corporations, he showed that an inventor with enough talent and determination can triumph despite daunting disadvantages.

No Resistance; August 2000; Scientific American Magazine; by Bruce Schechter; 2 Page(s)

For a few months in 1987, it seemed the world was about to change. Trains would fly on magnetic cushions, computers would be faster, electric power cheaper, new medical scanners would sprout in doctors' offices and more. The reason for this overheated optimism was the discovery by IBM scientists in Zurich, namely, J. Georg Bednorz and K. Alex Muller, of a new kind of superconductor, an almost miraculous material that conducts electricity without any loss of energy. Superconductors had been around since 1911, but all known superconductors worked at near absolute zero, which made them impractical for all but the most specialized applications.

The discovery led to a class of oxide superconductor working well above the temperature of liquid nitrogen. Boiling at 77 kelvins, liquid nitrogen is much less expensive to make and far easier to handle than liquid helium, which cools conventional superconductors. (Physicists still hope to find a material that superconducts at room temperature-possibly the next best thing to perpetual motion.) Gradually, researchers have found ways to craft high-temperature superconductors into useful magnetic components for research and for medical diagnostics and have even manufactured motors, current limiters and other devices for demonstration purposes. But now, more than a decade after their discovery, they are entering two markets closer to the consumer realm-power lines and wireless communications.

Different Stripes; August 2000; Scientific American Magazine; by Graham P. Collins; 1 Page(s)

Despite researchers' best efforts, high-temperature superconductivity remains a mystery. In the past few years, many physicists have studied the idea that organized lines of electric charge, known as stripes, could produce the resistanceless flow of current and other bizarre properties. In April two groups announced direct experimental evidence for this model in the superconductor known as YBCO (yttrium barium copper oxide). As has so often occurred in this field, the significance of the results is hotly debated, and barely a month later a third group reported studies inconsistent with stripes.

High-temperature superconductors are multilayered, ceramic crystals. All the superconducting action takes place in planes of copper and oxygen atoms sandwiched between layers of other elements, such as yttrium and barium. The density of electric charges free to move about on the copper oxide "meat" of the sandwich depends on the precise recipe used for the "bread." In the case of YBCO, excess oxygen in the yttrium barium oxide bread soaks up electrons from the copper oxide meat, leaving behind holes, which can be thought of as positively charged particles.

Cyber View: Circles of Trust; August 2000; Scientific American Magazine; by Wendy Grossman; 1 Page(s)

LONDON-In a world of disembodied strangers, the issue of trust is complicated. Some governments seem to think there's a simple solution-just make everyone trackable. The British government, for example, talks quite a lot about nonrepudiable digital signatures without ever acknowledging that a piece of electronic information is never going to be perfectly bound to a human.

The notion that the security systems we've been relying on don't work for the mass market the way we'd hoped they would occurred to me last December. An e-commerce site sent me a message saying the certificates built into earlier versions of Netscape were expiring. If I wanted to keep using their site, I had to... Upgrade my browser. First question: Why can't I just get updated copies of the certificates? Second question: What are certificates?

How Green Are Green Plastics?; August 2000; Scientific American Magazine; by Tillman U. Gerngross, Steven C. Slater; 6 Page(s)

Driving down a dusty gravel road in central Iowa, a farmer gazes toward the horizon at rows of tall, leafy corn plants shuddering in the breeze as far as the eye can see. The farmer smiles to himself, because he knows something about his crop that few people realize. Not only are kernels of corn growing in the ears, but granules of plastic are sprouting in the stalks and leaves.

This idyllic notion of growing plastic, achievable in the foreseeable future, seems vastly more appealing than manufacturing plastic in petrochemical factories, which consume about 270 million tons of oil and gas every year worldwide. Fossil fuels provide both the power and the raw materials that transform crude oil into common plastics such as polystyrene, polyethylene and polypropylene. From milk jugs and soda bottles to clothing and car parts, it is difficult to imagine everyday life without plastics, but the sustainability of their production has increasingly been called into question. Known global reserves of oil are expected to run dry in approximately 80 years, natural gas in 70 years and coal in 700 years, but the economic impact of their depletion could hit much sooner. As the resources diminish, prices will go up-a reality that has not escaped the attention of policymakers. President Bill Clinton issued an executive order in August 1999 insisting that researchers work toward replacing fossil resources with plant material both as fuel and as raw material.

Fountains of Youth: Early Days in the Life of a Star; August 2000; Scientific American Magazine; by Thomas P. Ray; 6 Page(s)

Go out on a winter's night in the Northern Hemisphere and look due south around midnight. You will see the constellation of Orion the Hunter, probably the bestknown group of stars after the Big Dipper. Just below Orion's Belt, which is clearly marked by three prominent stars in a line, is the Sword of Orion, and in the center of the sword is a faint fuzzy patch. This region, the Orion Nebula, is a giant stellar nursery embracing thousands of newborn stars.

Orion is a convenient place to study the birth of stars because it is relatively close by¿a mere 1,500 light-years away¿and has a good mix of low-and high-mass stars. It also contains a vast quantity of gas and dust in the form of a so-called molecular cloud. Such clouds are known to provide the raw material for new stars. What is now happening in Orion probably replicates what took place in our part of the galaxy five billion years ago, when the sun and its planets first came into being.

Is Global Warming Harmful to Health?; August 2000; Scientific American Magazine; by Paul R. Epstein; 8 Page(s)

Today few scientists doubt the atmosphere is warming. Most also agree that the rate of heating is accelerating and that the consequences of this temperature change could become increasingly disruptive. Even high school students can reel off some projected outcomes: the oceans will warm, and glaciers will melt, causing sea levels to rise and salt water to inundate settlements along many low-lying coasts. Meanwhile the regions suitable for farming will shift. Weather patterns should also become more erratic and storms more severe.

Yet less familiar effects could be equally detrimental. Notably, computer models predict that global warming, and other climate alterations it induces, will expand the incidence and distribution of many serious medical disorders. Disturbingly, these forecasts seem to be coming true.

Form from Fire; August 2000; Scientific American Magazine; by Arvind Varma; 4 Page(s)

Think of a burning trail of gunpowder. The fire races along its length, leaving nothing behind except loose ash and gases. Now imagine igniting the end of a different trail of powder. This time the bright, glowing wave of heat that surges through the mixture leaves a solidified mass in its wake. This seemingly paradoxical effect-that burning need not always use up materials or break them down-is entirely real and is the essence of one of the most promising innovations in materials science: combustion synthesis.

Scientists have known about combustion synthesis for three decades, and they have learned to create more than 500 compounds, many of which have proved to be invaluable as ball bearings, nuclear safety shields, abrasives, high-temperature superconductors and other technologically advanced items [see box on page 61]. But despite this long history, trial and error has been the primary means of invention. For example, a researcher might eventually realize that starting with finer powders can make the synthesized material stronger, but he or she could only guess at the reasons why. As a result, the applications of combustion synthesis have remained highly specialized. Only recently have engineers begun to understand how a heat wave actually propagates through the original mixture, leaving the desired material in its wake. Knowing precisely what happens between starting components and final product is the best way for researchers to refine techniques of combustion synthesis for widespread use.

The Universe's Unseen Dimensions; August 2000; Scientific American Magazine; by Nima Arkani-Hamed, Savas Dimopoulos, Georgi Dvali, side bar by Graham P. Collins; 8 Page(s)

The classic 1884 story Flatland: A Romance of Many Dimensions, by Edwin A. Abbott, describes the adventures of "A. Square," a character who lives in a two-dimensional world populated by animated geometric figures-triangles, squares, pentagons, and so on. Toward the end of the story, on the first day of 2000, a spherical creature from three-dimensional "Spaceland" passes through Flatland and carries A. Square up off his planar domain to show him the true three-dimensional nature of the larger world. As he comes to grasp what the sphere is showing him, A. Square speculates that Spaceland may itself exist as a small subspace of a still larger four-dimensional universe.

Amazingly, in the past two years physicists have begun seriously examining a very similar idea: that everything we can see in our universe is confined to a three-dimensional "membrane" that lies within a higher-dimensional realm. But unlike A. Square, who had to rely on divine intervention from Spaceland for his insights, physicists may soon be able to detect and verify the existence of reality's extra dimensions, which could extend over distances as large as a millimeter ( 1/25 of an inch). Experiments are already looking for the extra dimensions' effect on the force of gravity. If the theory is correct, upcoming high-energy particle experiments in Europe could see unusual processes involving quantum gravity, such as the creation of transitory micro black holes. More than just an idle romance of many dimensions, the theory is based on some of the most recent developments in string theory and would solve some long-standing puzzles of particle physics and cosmology.

Male Sexual Circuitry; August 2000; Scientific American Magazine; by Irwin Goldstein; 6 Page(s)

Five hundred years ago Leonardo da Vinci made an observation about the penis that rings true even today for many men and their partners. The Renaissance scientist, inventor and artist-one in a long line of investigators who have attempted to solve the riddle of penile rigidity-observed that this seemingly wayward organ has a will of its own. "The penis does not obey the order of its master, who tries to erect or shrink it at will, whereas instead the penis erects freely while its master is asleep. The penis must be said to have its own mind, by any stretch of the imagination," he wrote.

Da Vinci, who dissected cadaverous penises from men who had been executed by hanging, was the first scientist to recognize that during an erection, the penis fills with blood. In his perception that the penis acts of its own free will, however, this multitalented scholar was wrong.

Birth of the Modern Diet; August 2000; Scientific American Magazine; by Rachel Laudan; 6 Page(s)

Were we to attend a 16thcentury court banquet in France or England, the food would seem strange indeed to anyone accustomed to traditional Western cooking. Dishes might include blancmange-a thick puree of rice and chicken moistened with milk from ground almonds, then sprinkled with sugar and fried pork fat. Roast suckling pig might be accompanied by a cameline sauce, a side dish made of sour grape juice thickened with bread crumbs, ground raisins and crushed almonds, and spiced with cinnamon and cloves. Other offerings might consist of fava beans cooked in meat stock and sprinkled with chopped mint or quince paste, a sweetmeat of quinces and sugar or honey. And to wash it all down, we would probably drink hypocras, a mulled red wine seasoned with ground ginger, cinnamon, cloves and sugar.

Fast-forward 100 years, though, and the food would be reassuringly familiar. On the table might be beef bouillon, oysters, anchovies and a roast turkey with gravy. These dishes might be served alongside mushrooms cooked in cream and parsley, a green salad with a dressing of oil and vinegar, fresh pears, lemon sherbet, and sparkling white wine.

Working Knowledge: Focusing in a Flash; August 2000; Scientific American Magazine; by Glenn Zorpette; 2 Page(s)

High-quality cameras all employ the same basic system for automatic focusing, known as phase-detection autofocus. In a single-lens reflex (SLR) camera, light from a part of the scene passes through the lens and then through the camera's reflex mirror, which is partially transparent. (The reflex mirror flips up when the shutter button is pressed to allow the image to fall on the film.) A submirror, attached to the back of the reflex mirror, directs the light that comes through the main mirror downward to the autofocus module.

After passing through various lenses and filters, the light rays fall on an array of light-sensitive charge-coupled devices (CCDs). It is the distance between the illuminated CCD elements that indicates how close the image is to being in focus. A logic circuit constantly monitors that separation and drives a motor that spins the focusing ring of the lens, shifting the focus. When the separation hits a predetermined value, the logic circuit stops the motor and flashes lights in the viewfinder to indicate that the image is focused.

The Amateur Scientist: How to Rear a Plankton Menagerie; August 2000; Scientific American Magazine; by Shawn Carlson; 2 Page(s)

The Monterey Bay Aquarium in California houses some of the finest marine exhibits in the world. So when the staff recently offered me a personal, behind-thescenes tour, I couldn't refuse. Tim Cooke and Ed Seidel made the visit absolutely fascinating, and I am indebted to them for their hospitality. Tim, an aquarist extraordinaire, even let me in on a few secrets for raising plankton.

And he should know them: the Monterey Bay Aquarium grows a lot of plankton. Tim rears tons of the stuff each year to feed the thousands of voracious fish, crustaceans and jellies under its care. But these single-celled critters are not just fish food: they are quite intriguing in their own right and can provide amateur scientists with endless hours of delightful observation. When viewed under a microscope, the tiny phytoplankton (plants) and zooplankton (animals) are amazingly beautiful and complex.

Mathematical Recreations: A Fractal Guide to Tic-Tac-Toe; August 2000; Scientific American Magazine; by Ian Stewart; 3 Page(s)

I am being haunted by a fractal. In a recent column [see "Sierpinski's Ubiquitous Gasket," August 1999] I described several occurrences of the fractal known as Sierpinski's gasket, which can be obtained from a triangle by successively deleting an inverted triangle half its size. Ever since, readers have been alerting me to new sightings of this versatile figure. Its latest incarnation is in the field of mathematical logic. Patrick Grim and Paul St. Denis of the State University of New York at Stony Brook sent me a paper entitled "Fractal Images of Formal Systems" (Journal of Philosophical Logic, Vol. 26, No. 2, pages 181-222; 1997).

A fractal is a shape that can be divided into parts that are smaller versions of the whole. A genuine fractal such as Sierpinski's gasket has detailed structure on all scales of magnification: any piece of it, no matter how small, will resemble the whole. A quasi-fractal, in contrast, is an approximation of a true fractal-it has detailed structure over a large but finite range of magnification scales. The patterns of a quasi-fractal do not continue to infinitely fine scales, but because the human eye cannot distinguish such small details, quasi-fractals look convincingly fractal. One of the accomplishments of Grim and St. Denis was to devise a quasifractal diagram that represents all the possible games of tic-tac-toe.

Books; August 2000; Scientific American Magazine; by Staff Editors; 2 Page(s)

Carol Beckwith and Angela Fisher spent the past 10 years living and traveling in 26 African countries, gathering material for this monumental two-volume set. They photographed 43 ceremonies that span the human life cycle-from birth, through initiation, courtship, marriage, royal coronations, seasonal rituals and healing exorcisms, to death. By living among the people, learning their languages, eating their foods and adapting to their pace of life, the women were able to witness ceremonies that might never have been recorded. Many of the traditions chronicled in African Ceremonies will disappear with the next generation.

Organized into sections corresponding to the cycle of life are nearly 850 full-color photographs. Some are an imposing 14 by 20 inches; all are stunning. Beckwith and Fisher introduce each section with a concise, informative essay. But it is the pictures that do the talking.-The Editors

Wonders: Laws of Calorie Counting; August 2000; Scientific American Magazine; by Philip Morrison, Phylis Morrison; 2 Page(s)

Gazing into our quiet street, we see a scrap of paper ruffle in the breeze or a little water creep along the gutter. Those motions have clear causes: wind and gravity. But the local raccoon that hunts by night and the car that rolls past are distinct. The forces that impel both are mustered internally: timed muscular contractions lift and plant paws, and a stream of explosions turns the wheels. Each selfmover draws on a diet of energy, the one scraps of food, the other gasoline.

The quantity of energy we take daily from food has entered common parlance in the U.S. Every edible offering on the shelf declares by law its nutritional energy in calories-units of heat, a form of energy release easily measured. (Bottled water declares itself out of the energy game: 0 calories per serving.) One kilocalorie is heat enough to raise the temperature of one kilogram of water by one degree Celsius. (Many labels carry the term "calorie" but all the same intend by it the kilocalorie.) The energy we expend is neither provided as nor mainly used as heat.

Connections: The Grand Plan; August 2000; Scientific American Magazine; by James Burke; 2 Page(s)

Whenever I begin to feel that my life is one of trivia and secondary sources, I whistle a happy tune and recall the words of Reverend William Paley (1743-1805), a well-heeled English prelate who managed almost never to preach at the many ecclesiastical livings he almost never visited. And on the rare occasion when he did climb into the pulpit, he operated by the precept "Write one sermon and steal five."

Paley was the guy whose 1802 "Natural Theology" (a last, fixity-of-species Grand Plan fling before Darwin) bolstered religion by showing how a rational examination of design in nature proved the existence of God during a period when scientific and technological change were calling all in doubt. An elephant's "unbending" neck, for example, was compensated for by its flexible trunk. All the different bits of nature were there for a specific purpose, and the entire thing worked together for a common end.

Anti Gravity: Measure for Measure; August 2000; Scientific American Magazine; by Steve Mirsky; 1 Page(s)

Don't forget your units, your joules!" my freshman chemistry professor used to say before every exam. Actually, he had a charming accent that made the admonition sound more like, "Dohn forgeh joor junits, joor hools," which at least partly explains why the words still ring in my ears more than two decades later. He thus reminded us students of the smelly science that without units-such as the joule, a standard quantity of energy-our test answers were meaningless. It was a good lesson. After all, 0.0648 gram of sodium chloride equals the proverbial grain of salt, a grain being an avoirdupois unit in good standing, also equal to 0.002285 ounce. But what are 10 or 20 of salt, other than an extra credit question on a philosophy exam?

Units are everywhere, with the exception of the previous sentence. We're drenched with ounces, laden with pounds, bursting with inches, overrun with feet. More obscure units include the hogshead, equal to 63 gallons for some reason. Speaking of hogsheads, there is the joke unit the milliHelen, which is the precise amount of beauty required to launch a single ship. There are profound, poetic units: T. S. Eliot's creation Prufrock notes, "I have measured out my life with coffee spoons." And this was way before Starbucks colonized the planet.