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+ngcles
most of the 'first cycle' stars are devoid of anything heavier than helium so eliminating the first cycle after the big bang.
Even short cycle second cycle stars are unlikely to produce as they are usually supergiants and go SN quite early in life.
So we need a third cycle star with no close by heavy radiation to keep us in the slime.
Which means you have to be on the outside of the galaxy arms or lucky.
You then need a mass extinction to produce enough storable energy to lay down hydrocarbon fuels for a prospective intelligent species to break through the industrial revolution.
Then you need the civilisation to be smart enough not to nuke itself when it does reach that level (I'm not sure we've gotten away with this yet).
Then they need to crack plus light travel.
All in all, not a good set of odds. Perhaps one in 1,000,000 planets in our galaxy. That means there's thousands and thousands if not millions of planets out there with intelligent life.... all onthe threshhold of interstellar travel.
Hopefully they're not all as greedy and vicious as us.
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