In one of the outlying spiral arms of the Milky Way galaxy, an inconspicuous, solitary yellow star slowly orbits the galactic centre thirty thousand light years away. This stable star, the Sun, takes 225 million years to complete one revolution in its galactic orbit. The last time the Sun was in its present position, giant reptiles of fearsome power had just begun to establish their dominion on the Earth, a small blue planet that is one of the satellites of the Sun.
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 dimension 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 20 per cent of these stars have orbiting planets, and that a small but significant numbers 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 chemical that are the sine qua non for any biology we can reasonably hypothesise. 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 in motion. How can we presume that this sequence occured only that single time in all history? The heavier atoms necessary to create us have been forged in the stellar catalysms 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 adventures of Rama by Arthur C Clarke and Gentry Lee available as Game