Suppose there are 100,000,000 Earth like planets capable of sustaining intelligent life.
Also suppose that the Earth is 5,000,000,000 years old.
We have been exploring the universe and broadcasting radio waves for the last 100 years, and suppose that we may yet do so for another hundred.
So the window of time that we are detectable to an extraterrestrial intelligence will be 200/5,000,000,000 or one in 25,000,000 years.
So if the assumptions are true, the number of intelligent civilizations detectable to Earth explorers at any time is not 100,000,000 but more like four.
The fact that we are not seeing these other civilizations is merely an indication that the duration of a climax technological civilization like ours is very short, astronomically speaking, on the order of 200 to 1000 years.
Given what we can all see of human civilization, this seems very plausible.
Someone has to be ‘first’..............Why not us?....................