Scientific American Magazine

What some call a "Star Wars" defense would depend on computers to control an unprecedentedly complex array of weapon systems. Developing reliable software for such a defense may be impossible

In everyday experience time always moves forward. The situation is qualitatively different, however, in the case of wave motion: light waves can be "time-reversed" and made to retrace their trajectories

The female's ability to recognize the male's calling song and to seek out the source of the song can be used to study how nervous-system activity underlies animal behavior

The AIDS virus alters the growth and function of T4 lymphocytes, a class of white blood cells that is crucial to the immune system. New knowledge of how the virus does so may lead to treatments and perhaps a vaccine

Regions at the planet's equator seem once to have been near a pole; possibly the entire lithosphere has shifted in relation to the axis of spin. This theory explains many puzzling features and processes

The classification of the finite, simple groups is unprecedented in the history of mathematics, for its proof is 15, 000 pages long. The exotic solution has stimulated interest far beyond the field

After the many disruptions of recent decades the output of China's farms about equals the need for food. Whether the balance can be maintained depends on how the nation copes with some problems

The nature of the "blueprints" from which the Greeks built their temples has long eluded archaeologists. A recent discovery shows they were drawn on stone surfaces of the very temple they depict