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in reply to Extraterrestrials haven't visited the Earth yet because:

#2 and #3 really should go together. There probably aren't any suitably capable extraterrestrials close enough to have detected us, decided to contact us and then done so. Note that, unless Einstein was dead wrong about the limitations imposed by the speed of light, extraterrestrials must have the capability to live for millennia in order to either communicate or travel effectively over interstellar distances. That means they would either need to also have the capability to engineer that longevity or they would take billions of years to evolve.

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Re^2: Extraterrestrials haven't visited the Earth yet because:
by Arunbear (Prior) on Sep 19, 2016 at 10:49 UTC
    Not exactly. #2 is meant to cover the case where there is extraterrestrial life, but it never evolves to a human level of intelligence (or higher). i.e. we don't know if the emergence of life inevitably leads to technological capability.