A mass extinction event would mean there wouldn't be a civilization on the plane...

		pdonis on July 24, 2015 \| parent \| context \| favorite \| on: NASA’s Kepler Mission Discovers Bigger, Older Cous... A mass extinction event would mean there wouldn't be a civilization on the planet at all. That's certainly possible, but for this particular subthread I am taking as a premise that there is a civilization there.