Scientific American Magazine

Could orbiting lasers defend a nation against missile attack? The technological obstacles are insurmountable; furthermore, such weapons would be vulnerable to simple countermeasures

Certain aquatic bacteria are magnetotactic: they have tiny internal compasses that orient them in the earth's magnetic field. Swimming along the inclined magnetic field lines directs them toward the mud

These megalithic monuments, like many others, have been seen as ancient astronomical observatories. It seems clear that although they are astronomically aligned, their purpose was purely ritual

Competing models seek to describe the sun's two giant companions. In one model the winds are confined to a thin layer at the surface; in another the winds extend through the fluid depths of each planet

The bird exploits diikrences between the sound in its left and right ears to find mice in the dark. It can localize sounds more accurately than any other species that has been tested

The plasma protein fibrinogen is converted into fibrin to form a blood clot. In time the clot breaks down. Both processes can now be understood in terms of the detailed structure of the protein

Symbols as well as numbers can be manipulated by a computer. New, general-purpose algorithms can undertake a wide variety of routine mathematical work and solve intractable problems

Certain conditions, such as temperature, were favorable to the emergence of life on the earth. The anthropic principle argues the reverse: the presence of life may "explain" the conditions