Новости науки и техники в "Scientific American"

SKEPTICAL OF TIME TRAVEL

In the original Star Trek series, Dr. McCoy falls through a time portal in a city "on the edge of forever," and changes the past in a way that erases the Enterprise and her crew, with the exception of Captain Kirk and Mr. Spock, who must return to the past to fix what McCoy has undone. Time travel is a well-worn staple of science fiction writers, but not only does it violate numerous physical laws, there are fundamental problems of consistency and causality.

CLIMATE EFFECTS OF CONTRAILS CONFIRMED

Scientists have long suspected that contrails, the trails of white exhaust that jets leave in their wake, can affect climate. Quantifying their effects was extremely difficult, however, because the nearly constant air traffic over most of Europe and North America made it impossible to study clear skies for comparison. But the grounding of commercial aircraft after the September 11 terrorist attacks provided just such an opportunity. Now an analysis of measurements taken during that time indicates that contrails do indeed warm the air.

BOOKSTORE: SEEING IN THE DARK: HOW BACKYARD STARGAZERS ARE PROBING DEEP SPACE AND GUARDING EARTH FROM INTERPLANETARY PERIL By Timothy Ferris

If you've never heard of Stephen James O'Meara or Don Parker, then you've missed some of the most fascinating adventures in 20th-century astronomy. O'Meara was the first person to measure the length of a day on Uranus and to see radial "spokes" in Saturn's rings. (Most astronomers dismissed that discovery as illusionary, until Voyager got close enough to photograph them.) What's more remarkable, in an age of computer-enhanced CCD images, O'Meara made these observations visually, using only a small telescope and his own eyes. Parker went in a different direction. After improving the technique of CCD-based astrophotography, he amassed what might be the world's most extensive and scientifically valuable digital archive of planetary portraits. Despite their passion for astronomy, both hold more down-to-earth day jobs.

FLYING SNAKE AERODYNAMICS EXPLAINED

The air is not the domain of winged beasts alone. Some creatures - certain species of squirrels and lizards among them - glide above the ground with the help of paired skin flaps that generate lift. But in the case of the paradise tree snake, which dwells in the tropical rainforests of South and Southeast Asia, no such appendages exist. Nor, for that matter, do any other morphological specializations. Yet the animal "flies" with great precision. New study results reveal how.

ANTIBODY COCKTAIL BATTLES BOTULISM

Researchers have developed a potent weapon against the paralyzing disease botulism. The affliction results from exposure to botulinum neurotoxin (BoNT), which is secreted by a soil bacterium called Clostridium botulinum. The most poisonous substance known, just a gram of BoNT could kill a million people if evenly dispersed and inhaled. As such, it ranks among the Centers for Disease Control and Prevention's six highest-risk threat agents for bioterrorism. At the moment, no anti-botulism treatments capable of being produced on a large scale are available. But a new drug both neutralizes the toxin very effectively in mice and apparently can be readily mass-produced and stockpiled.

SATELLITE DATA REVEAL A PLUMPER PLANET EARTH

The earth is more like a pumpkin than a perfect sphere: it's a bit wider around the middle. Scientists have been tracking the earth's girth for more than two decades. For most of this time, the planet was becoming more spherical because the melting of the polar ice caps at the end of the last glaciation allowed the earth's mantle to relax slightly in a process known as postglacial rebound. Now researchers say this trend has reversed.

ASK THE EXPERTS: WHY DO WE YAWN WHEN WE ARE TIRED?

Mark A. W. Andrews, associate professor of physiology at the Lake Erie College of Osteopathic Medicine, explains.