Quote:
Originally Posted by eburacum45
Maybe so, but I doubt that there are any such species within the visible universe, so we are unlikely to ever meet them.
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I think that even the visible universe is sufficiently large that I would still be satisfied that my assertion is reasonable - that is, if I may be allowed to modify my original statement by redefining "are" to mean "have been, now are, or will be." (The thing that I find most striking about the Drake equation is the effect of varying the length of time that ET's exist.)
Atlasoftheuniverse.com puts the number of large galaxies in the visible universe at 350 billion. There is an article on space.com in which Dr. Charles Lineweaver (research astronomer) guesses that there may be a billion Earth-like planets in our galaxy. Using these numbers, and assuming that there is nothing special about the Milky Way, if only one-billionth of Earth-like planets in the visible universe contain sentient life, and only one-billionth of these creatures closely resemble us, that still leaves 350 species.
However, I agree completely that the chance that a human will ever encounter one of them is vanishingly small.