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Preserving the Laetoli Footprints

The discovery of hominid footprints in East Africa reshaped the study of human origins. Now conservators have protected the fragile tracks from destruction

By Martha Demas and Neville Agnew

Weightlessness and the Human Body

The effects of space travel on the body resemble some of the conditions of aging. Studying astronauts' health may improve medical care both in orbit and on the ground

By Ronald J. White

Making New Elements

Three new elements--110, 111 and 112--have been produced over the past several years. Scientists are now struggling to create 113 and 114. How many elements can they add to the periodic table?

By Fritz Peter Hessberger and Peter Armbruster

The Oort Cloud

On the outskirts of the solar system swarms a vast cloud of comets, influenced almost as much by other stars as by our sun. The dynamics of this cloud may help explain such matters as mass extinctions on Earth

By Paul R. Weissman


Semiconductors that convert radiant heat to electricity may prove suitable for lighting remote villages or powering automobiles

By Mark C. Fitzgerald and Timothy J. Coutts


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