The Drake equation [from google]
R*= 1/year (1 star formed per year, on the average over the life of the galaxy; this was regarded as conservative)
fp= 0.2-0.5 (one fifth to one half of all stars formed will have planets)
ne= 1-5 (stars with planets will have between 1 and 5 planets capable of developing life)
fl= 1 (100% of these planets will develop life)
fi= 1 (100% of which will develop intelligent life)
fc= 0.1-0.2 (10-20% of which will be able to communicate)
L= 1000-100,000,000 years (which will last somewhere between 1000 and 100,000,000 years)
Inserting the above minimum numbers into the equation gives a minimum N of 20. Inserting the maximum numbers gives a maximum of 50,000,000. Drake states that given the uncertainties, the original meeting concluded thatN ≈ L, and there were probably between 1000 and 100,000,000 civilizations in theMilky Waygalaxy.
Furthermore, no confirmed signs of intelligence elsewhere have been spotted, either in our galaxy or the more than 80 billion other galaxies of theobservable universe. [also google]
Though estimates today vary from just 2 civilizations all the way into the hundreds of millions! [still google]
For this discussion, I will use Drakes original estimate of 20 and that the Milky Way galaxy is nothing special as far as galaxies are concerned. Multiplying the terms together, 20x80 billion: 1.6 trillion civilizations!!
Some civilizations may be very densely populated or not. No way to know. Earth has some 7 billion people. So lets say an average civilization is 5 billion. Multiplying the terms together, 1.6 trillion x 5 billion: 8e+21 [google]
That's an astonishing amount of "people" in the universe.
Where are they?