Isaac Arthur on MSNOpinion
The ancient alien theory sounded possible - until the missing evidence became impossible to ignore
What if an alien civilization did not just exist somewhere in the universe, but actually reached Earth in the distant past?
Add Yahoo as a preferred source to see more of our stories on Google. Those concerned that 3I/ATLAS' arrival to our solar system meant that some sort of alien invasion was imminent can breathe a sigh ...
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