Another remote possibility is that one alien race had a colony on our planet, making it a target in an interstellar war. Or an indigenous intelligent species, for instance an intelligent reptile race. But we would have seen some signs of such a colony in the fossil record. We have never seen a fossil from that period with a large enough brain-case to be intelligent.
The only other remote possibility is a stray missile which had wandered through interstellar space and hit our planet. But again the distances between stars are so great that the chances of an alien missile even entering our inner solar system are remote, let alone actually hitting our planet.
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Venus 1485AD say: That's not a scientific theory, it's just juvenile fiction. Interstellar travel is impractical. No ETs could come here and have wars. We already know what caused the dinosaurs' extinction, so we don't need juvenile fiction about it.
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Acetek say: Nonsense
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Namjodh say: Just like in the Bible, eh?
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Jeff say: We need to ask all the christians who were riding dinosaurs on saddles...
(idiots)
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