Since the dawn of recorded history, Man has pondered the possibility of life beyond Earth. Our ideas about extraterrestrial life have become an integral part of our culture, permeating everything from cinema to psychiatry. We have sent messages aboard deep-space probes, we scan the electromagnetic spectrum, and we slice apart ancient meteorites in an attempt to answer ages-old questions concerning the possibility of extraterrestrial life.

Initially, a distinction must be drawn between extraterrestrial life and extraterrestrial intelligence. Extraterrestrial life can encompass anything from microscopic amoebas to intelligent animal forms. To seek extraterrestrial intelligence, however, is to embark upon a search for extraterrestrial culture and communicative abilities. We assume that intelligent extraterrestrial civilizations would be the easiest for us to discover, either through direct contact (which seems unlikely, considering the vast interstellar distances that would presumably have to be crossed) or through an exchange of communications.

Thus...