GENESIS BY LIGHTNING--"University of Chicago chemist Harold Urey has championed one theory as to how life began on earth. It suggests that a billion years ago or so the earth's atmosphere consisted of methane, ammonia, hydrogen and water vapor. Under the action of lightning discharges or of ultraviolet radiation, these compounds were split into free radicals, which recombined in chance ways to form more complex molecules. A few months ago Urey had one of his students, Stanley L. Miller, assemble a mixture of methane, ammonia and hydrogen over boiling water in an air-tight glass system and circulated the vapor continuously past an electric spark. By the end of the day the mixture turned pink; after a week it was a deep, muddy red, and it contained amino acids--the building blocks of proteins."