The Global Positioning System
Thomas A. Herring
Two dozen satellites hovering thousands of miles up can locate your position on the earth's surface to within a few centimeters. Originally constructed for military applications, this network of space beacons today finds civilian applications--such as landing airplanes in fog--that demand accuracy beyond what its designers had thought would be technically possible.
Seeing Underwater with Background Sound
Michael J. Buckingham, John R. Potter and Chad L. Epifanio
The crash of waves, the patter of rain, the thrum of ships' engines and other activities fill the oceans with ambient sound, much as the sun fills our sky with light. Using a variation on sonar technologies, it is now possible to visualize objects underwater by seeing how they interact with this "acoustic daylight." A prototype system has already been tested with the help of killer whales.
Telomeres, Telomerase and Cancer
Carol W. Greider and Elizabeth H. Blackburn
Time whittles away away at us, in literal truth: in much of the human body, those precious bundles of DNA called chromosomes become fractionally shorter with every cell division. Tumor cells, though, are immortal, seemingly because an enzyme called telomerase rebuilds the shrinking ends of the chromosomes. New research is focusing on telomerase as a possible target for anticancer therapies.
Colossal Explosions in Nearby Galaxies
Sylvain Veilleux , Gerald Cecil and Jonathan Bland-Hawthorn
The centers of some galaxies glow with a light that outshines the entire Milky Way. Black holes a billion times more massive than our sun may power most of them; others draw their energy from a rapid pulse of stellar evolution that creates millions of hot stars in a small volume of space. By strewing space with heavy elements, these active galaxies may shape the evolution of the universe.
The Bacteria behind Ulcers
Martin J. Blaser
Not spicy foods or nervous dispositions but acid-loving microbes are the culprits in most cases of stomach ulcers. They seem to be linked to stomach cancer as well. At least a third of all people carry these bacteria, yet only a small number ever become sick. Discover why that may be and what the newest treatments are.
The Loves of the Plants
Londa Shiebinger
When the great taxonomist Linnaeus looked at a flower bed, he saw a veritable orgy of botanical lust. By choosing to classify plants on the basis of their flowers' reproductive organs, he imposed 18th-century assumptions on the interpretation of nature--and found a natural "validation" of contemporary sexual values.
Computing Quarks
Donald H. Weingarten
The theory of quantum chromodynamics (QCD, for short) explains the behavior of matter well, but it was one drawback: its mathematics is too complicated for exact predictions. At least, it used to be--until the author helped to build a computer that tamed the ferocious calculations at the heart of fundamental physics.
The Analytical Economist
Communism's new capitalist clothes.
Technology and Business
Insurers fret over climate change.... The evolving Internet.... History lesson for Bill Gates.
Profile
Daniel C. Dennett explains consciousness and unleashes Darwin.
Letters to the Editors
Sex, evolution and psychology.... Identifying estrogens.... Physics survives.
50, 100 and 150 Years Ago
1946: No atomic cars.
1896: Spanish meteorite.
1846: Fire extinguisher.
The Amateur Scientist
Simulating how plants would grow on Mars.
Mathematical Recreations
Zero-based transactions: they know that you know that they know.
Reviews and Commentaries
Star guides.... Ecology in error?...
Wonders, by Philip Morrison: Binary beauty....
Connections, by James Burke: Fairy tales and photoelectricity.
Essay: James Randi
These weeping Madonnas are less than miraculous.
James Burke: Fairy tales and photoelectricity.
Essay: James Randi
No miracles in these weeping Madonnas.