When their wandering robot probes stumbled on Earth, with its ancient, burnt seabeds, its flattened forests, its cracked continents, they rapidly uncovered evidence of the long-dead human civilization, buried under three million years of rubble and dust, and they despaired that though they finally had found evidence of other intelligent creatures in the universe, they had missed meeting us by (in astronomical terms) only moments and would never have the chance to exchange so much as a word of greeting, as our race was clearly and inarguably now extinct.

But ... they were wrong.