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  • The number of habitable worlds in our galaxy is certainly in the tens of billions, minimum, and we haven't even talked about the moons. And the number of galaxies we can see, other than our own, is about 100 billion.

    "There Are ‘Tens Of Billions’ Of Habitable Planets In Our Galaxy, Astronomer Seth Shostak Says" by Lee Speigel, www.huffingtonpost.com. June 24, 2014.