Scientific American Magazine

How many stars in our galaxy may be accompanied by planets capable of supporting intelligent life? The answer requires reflection on the characteristics and life history of stars

This simple apparatus is used to investigate depth perception in different animals. All species thus far tested seem able to perceive and avoid a sharp drop as soon as they can move about

A German physicist's discovery is the basis of a nuclear clock of unprecedented accuracy. Such a device should make possible the first conclusive test of the general theory of relativity

The geologist defines it as particles of rock between .05 and two millimeters in diameter. The shape of sand grains, transported by water and wind, is a clue to their history

These silken insect traps are spun in many forms, from an apparently careless tangle to a precise geometrical structure. All have evolved from the single thread of silk that all spiders pay out behind them

This type of allergy has been identified as the cause of rash in poison ivy, pains in rheumatoid arthritis, lung cavitation in tuberculosis and nerve degeneration in multiple sclerosis

The exposure of single human cells to X-rays indicates that they are far more sensitive to radiation than had been thought. This explains why the relatively small dose of 400 roentgens is lethal to the body

In 1816 Shaka, chief of the Zulus, began a series of conquests that eventually disrupted a third of Africa. The story of his brief and bloody reign is a case history in the sociology of war