We keep asking ourselves whether we are indeed alone in the universe. There is a simple answer to this question, first posed by Enrico Fermi. Consider the following simple calculation:

Filter % #
Stars 300,000,000,000
Rocky Planets 0.1667% 500,000,000
Liquid Water 10.0000% 50,000,000
Sinple Life 1.0000% 500,000
Complex Life 1.0000% 5,000
Pre-Industrial Intelligence 1.0000% 50
Industrial Intelligence 1.0000% 1

If we apply reasonable assumptions to the filter of development of intelligent life, and even if we ignore the probability of this life’s destruction in the fullness of time, and even if we ignore the fact that life can develop and decline throughout the life of the galaxy, far outside of our own time horizon, we still arrive at the conclsion that in our galaxy there is only one technologically-advanced life form: us.

Update: Perhaps in 1500 years the numbers will look different.