Scientific American Magazine

Unless some action is taken soon to restrain the further development of such weapons the positive contributions of satellites to international security will be threatened

The metalsmiths of Andean cultures knew how to plate copper with gold or silver and how to treat alloys of copper, gold and silver so that the surface of the metal consisted only of gold

During brief intervals over the past 700 million years many marine animals and plants have died out. Geologic evidence now suggests that most of the mass extinctions were caused by cooling of the sea

The mobile genes Barbara McClintock discovered 40 years ago have since been identified in bacteria, other plants and animals. Several maize elements have now been characterized at the molecular level

The left- and right-handed versions of an atomic experiment do not always give rise to mirror-symmetric effects. The asymmetry is caused by the weak force between the electrons and the nucleus

The subtle interplay of such signals enables the Douglas-fir beetle to attract a mate, to repel intruders and to regulate the density of its population in the great tree of the western forest on which it preys

The particles of cosmic dust turn out to have an elaborate core-and-mantle construction. In the organic mantle there is evidence of complex, and even violent, chemical processes

The notion that a threaded bolt and a matching nut could serve as a fastener dates back only to the 15th century. Today nuts and bolts and ways of making them are still actively evolving