If extraterrestrial intelligence exists, then positive detection of it would be the greatest scientific discovery of all time. By what criteria should we judge whether we are alone in the cosmos, and how should we set about detecting extraterrestrials? Jean Heidmann answers these questions in this engaging discussion of extraterrestrial intelligence.

The author shows how planets fit into the hierachy of the universe, and discuss prebiotic stages of life, and the emergence of primitive biological molecules in the solar system. From this base the entire subject of extraterrestrials is explained: techniques and the results of current projects, the expansion of searches for extraterrestrials, the habitable zones in our universe, and what might happen if actual contact takes place.

Our generation is capable, in principle, of communication across interstellar space, bounded only by the speed of light, and soon it will be possible to set tight limits on the presence or absence of extraterrestrials in our Galaxy.