Why Haven’t We Been Contacted by Aliens?

I know the universe is a big place, but (at least as far as the general public knows) there has never been contact with a civilization from another planet.   Distances and the limits of physics notwithstanding, I’ve just run across an interesting theory about why this might be true  —  all the aliens are already dead.

A group of astrobiologists from the Australian National University (ANU) just announced this theory.  They hypothesize that if life did arise on other planets in our general neighborhood, it would probably have gone extinct very quickly.  Granted, there are many habitable planets out there, but the problem would probably be runaway heating or cooling because early planet environments are very unstable.  That would make it rare for life on other worlds to advance.  This model is called  the Gaian Bottleneck, or near-universal early extinction.

Look at our own solar system.  Venus and Mars could’ve been habitable once, but something went wrong in both cases.  This makes Earth even more special — it had enough time for life to evolve, and even contribute to its own complexity, like when plants started producing oxygen.

On the other hand, considering the universe’s time scale, how much longer are we going to be here?

Read the full analysis on the EarthSky website at http://earthsky.org/space/are-the-aliens-extinct-gaian-bottleneck-early-armageddon?utm_source=EarthSky+News&utm_campaign=932c765aba-EarthSky_News&utm_medium=email&utm_term=0_c643945d79-932c765aba-394611693

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