Why is sci-fi so obsessed with asteroid impact disasters (and how to stop them)?

For longer than science fiction has even existed, humans have been fascinated with (and terrified by) the prospect of space rocks falling to Earth. But why?

There is one obvious explanation: Asteroids have fallen to Earth many times before, sometimes with devastating consequences. (RIP, dinosaurs.) But at present, there is no imminent threat of any space rock hitting Earth and causing harm. While planetary defense experts monitor near-Earth asteroids, the vast majority of wayfaring cosmic chunks either miss us completely or are small enough to burn up on their way through our planet's atmosphere.

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