"Crusade" is a short story by English writer Arthur C. Clarke published in 1968 and republished in The Wind from the Sun as well as The Collected Stories of Arthur C. Clarke. It follows the extremely long life span of an artificial intelligence that exists on a freezing planet in the vast space between two galaxies. The intelligence sends out scouts into another galaxy to seek other life like themselves, only to discover the inhabitants of planet Earth, whose physique is very different from their own. Tens of thousands of years pass to collect data about the humans, before the intelligence decides to send a "crusade" that will reach planet Earth in the year 2050.
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Crusade (short story) Wikipedia(Text) CC BY-SA