Transcription: The scientists David Raup and Jack Sapkowski have looked at the history of regular patterns of extinctions over time and they think that an extinction event, as they call it, not as big as our famous two but bigger than your average extinctions, occurs about every 26 million years. Now if they're right, why would this be? Their suggestion is that the only explanation is that Earth is being bombarded by asteroids or comets every 26 million years. It's probably comets because of their type of orbit. Anyway, they suggested this in 1984 and everybody thought they were bonkers. By the way, the next ...
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