Among the planets and other bodies in the family of the Sun, it is only on this Earth that any complex, enduring life has ever developed. Only on this special world did chemicals evolve into consciousness and then ask, as they began to understand the wonders and dimensions of the universe, if miracles similar to the ones that had produced them had indeed occurred elsewhere.

After all, these sentient Earthlings argued, there are a hundred billion stars in our galaxy alone. We are fairly certain that at least twenty percent of these stars have orbiting planets, and that a small but significant number of these planets have had, at some time in their history, atmospheric and thermal conditions conducive to the formation of amino acids and other organic chemicals that are the sine qua non for any biology we can reasonably hypothesize. At least once in history, here on Earth, these amino acids discovered self-replication, and the evolutionary miracle that eventually produced human beings was set into motion. How can we presume that this sequence occurred only that single time in all history? The heavier atoms necessary to create us have been forged in the stellar cataclysms exploding across this universe for billions of years. Is it likely that only here, in this one place, these atoms have concatenated into special molecules and evolved into an intelligent being capable of asking the question, “Are we alone?”

The humans on Earth began their search for cosmic companions first by building telescopes with which they could see their immediate planetary neighbors. Later, when their technology had developed to a higher level, sophisticated robotic spacecraft were sent to examine these other planets and to ascertain whether or not there were any signs of biology. These explorations proved that no intelligent life has ever existed.on any other body in our solar system. If there is anyone out there, the human scientists concluded, any peer species with whom we might eventually communicate, they must be found beyond the void that separates our solar system from ail the other stars.