Quote:
Originally Posted by fjtorres
Beyond that, and bearing on life-probabilities, is what we're finding out about planet formation processes and the (limited) amount of time that the planet-formation clouds can survive. And about the composition of those clouds. The latter suggests that earthlike planet formation requires a lot of heavy elements in the cloud which requires supernova ejecta from second or third generation stars. Which in turn suggests there may not be many earthlike worlds that are older than Earth.
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This is my understanding as well. Although it may not matter much - behaviorally modern humans didn't arise until about 50,000 years ago; the oldest cities about 12,000 years ago; writing arose about 5,000 years ago; and e-ink readers only about 6 years ago. :-)
So on a comparable earth-like planet, it would be trivial to encounter a species with a civilization 100,000 years older than ours. Assuming equivalent development, that would mean that they would have to have gotten started only .0025% earlier than we did.
Which might make our listening for radio waves the equivalent of a primitive tribe trying to detect other intelligent life by listening for their drums.