I've always believed the evolutionary filter argument.
Assuming Earth is the model of success for life.
Single cellular organisms existed for hundreds of millions of years comfortable without photosynthesis.
After that life lived on comfortable for Hundreds of millions of years before multicellular organisms formed.
Hundreds of millions of years again before animals. Sentient, complex, moving, thinking, multi-organelle systems.
Hundreds of millions of years again before language.
Maybe math or writing or scientific method are all equal difficult barriers that came easier to us because of the trajectory we are on.
So I look at it this way, if there are 1B systems in milky way that have formed life, and every one of those filters only has a 5% success rate, so 95% of life does not reach the next filter before catastrophe
Planets with Life 1B
A way of storing energy from a star 50M (photosynthesis)
Multi Cellular organisms 2.5M
Animals 125K
Language 6.25K
Writing/Math/Science 312
Assuming we survive the rest of our suns life we will have been detectable for what equates 1/3 of the current history of the universe. 104
The odds are even if most systems have life there could vary easily as few as 100 life forms that have reached the level of interplanetary communication, and then you have to assume the communicate in a way we can comprehend
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