Classic example of a "scientific wild ass guess" made without any supporting data at all. Which means, of course, that there's nothing scientific about it at all, making it only a "wild ass guess."
A scientists' "wild ass guess" has no greater validity at all than anybody else's.
Sherman Logan: "Classic example of a "scientific wild ass guess" made without any supporting data at all."
It's worse than that -- it contradicts it's own numbers.
Consider, the Milky Way galaxy is said to have from 100 to 400 billion (with a "b") stars, of which supposedly NASA says:
Well, 10% of 100 billion is 10 billion, not 100 million, and 20% of 400 billion is 80 billion potential earth-like planets in the Milky Way galaxy alone.
Multiply times maybe 100 billion galaxies in the "known universe", and the number of possible Earth-like planets grows beyond comprehension.
Of course, "Earth-like" does not mean any of them have some kind of life, much less "intelligent life".
That's the big unknown.
Until some evidence is found of any life on any other planet, there's no possible way to guess if we are all alone, or just one of millions/billions of others.
So far the "odds" suggest billions of other, but the facts still say we're alone.