Science fiction crawls with intelligent BEMs (bug-eyed monsters) and humanoids (manlike creatures) that live on planets revolving about distant stars. Most fact-fancying scientists are far more skeptical. Somewhere in the universe, they say, there may indeed be a scattering of planets with salubrious atmospheres and temperatures, and something like earthly life. But the planets are probably few, and the odds against finding or communicating with their far-out creatures, say the skeptics, are exceedingly high.
Caltech Geochemist Harrison Brown demurs. It is a good bet that populated planets are spotted throughout the universe,...