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Fermi Paradox

Are We Alone In The Universe? 13 Theories

Tim Urban | Posted 08.17.2014 | Science
Tim Urban

Scientists estimate that there are over 100,000 intelligent alien civilizations in our galaxy alone -- but we've never heard anything from any of them. Here are 13 possible explanations for why.

Where Are They?

Mario Livio | Posted 03.20.2013 | Science
Mario Livio

If our Milky Way galaxy and the universe at large are indeed teeming with intelligent extraterrestrial (ET) civilizations, why haven't we seen any sign of them yet? In other words, where are they? This mystery has become known as the "Fermi paradox."

Where Are the Aliens? Fermi Paradox Redux

Seth Shostak | Posted 05.25.2011 | Technology
Seth Shostak

We don't see any evidence extraterrestrial life. Does that mean that Homo sapiens is the smartest species within 100 thousand light-years? That would be remarkable and, judging by my daily interaction with said species, scary.