William W. Kellogg

Over the more than four-and-a-half billion years since the formation of the planet Earth, its climate has remained remarkably stable, and has apparently sustained life for about four billion of those years. Throughout that long period the oceans and the atmosphere have maintained an uneasy equilibrium; the sun has been a sufficiently steady source of heat so that the oceans have neither boiled their water away into space nor frozen down to the equator--fates that many other planets and satellites of the solar system have suffered.