“In the beginning,” so it is written, “God created the heavens and the earth.”
Sometime after that, humans came along in this cosmological origin story too (although I would wager that this occurred more than just a few days later, despite what the text quoted above has to say about it). Thereafter, we spent ages bumbling around on our little mudball, during which the rise and fall of chiefdoms, city-states, and civilizations occurred, along with countless wars and conflicts over land disputes, material shortages, kidnappings, killings, and the like.
At some point, things seemed to have calmed down a little–agriculture certainly helped with this, as did the formation of laws and governance–and humans finally had time to rest, and perhaps more importantly, to think. After a few thousand years of contemplation along these lines, finally, within the last few hundred years or so somebody had the idea that we might not be the only ones the Big Guy upstairs took the time to bother to create… if you prescribe to that sort of thing.
Formation of the idea that there might be inhabited worlds beyond our own first required understanding that Earth is, in fact, a round planetary body in space, and that several others exist in our cosmic neighborhood, all encircling our sun (hat tips are in order here for Galileo, Kepler, Pythagoras, Eratosthenes, and various others who contributed to such thought over the ages). In light of this, the idea of leaving Earth to visit nearby celestial bodies has actually been around for quite a while: mention of such things as travel to the moon had already been left to posterity as early as the second-century in Lucien’s satires, and a few centuries thereafter, philosophers were seriously debating the idea of whether other planets existed, and what kinds of “people” might reside there (“Cosmic Pluralism,” in other words).
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