What is your opinion of the arguments made in "Rare Earth". The Drake equation only gives the upside, but doesn't seem to take into account the conditions that would preclude higher forms of life. For instance, the radiation conditions in the core of galaxies and in the arms of spiral galaxies are too high to allow the survival of higher life forms. That leaves the area between the arms for habitable zones in spiral galaxies, and stars only stay in between the spiral arms for extended periods of time if they are 1/2 the radius of the galaxy from the center of the galaxy. These factors alone remove several orders of magnitude from the number of possible stars that could sustain higher forms of life.
Still leaving a fairly large number in the end.
Just a thought: If we only find ONE other inhabited planet in the entire galaxy will the Bible Thumpers admit defeat and all become atheists? How about two planets? What's the end-of-Religion threshold?
Hint- The Americas are not mentioned ANYWHERE in the Bible, finding land and 'Injuns' didn't make the Church crumble. So, why do the Bible Thumpers fear life anywhere but here?
hmmm?
As I stated earlier; there is at least one data point for life in the Galaxy/Universe. Us! Even if all life is confined to these sparse regions of the galaxy, there could be huge numbers of life producing planets. And that is just in our galaxy alone.