Where Have All the Aliens Gone?

ScienceBlogs - Posted by Ethan on March 29, 2013

“If the Universe Is Teeming with Aliens… Where Is Everybody?” -Stephen Webb

It’s one of the biggest conundrums in the Universe, known as the Fermi Paradox: if the Universe is so conducive to life, and if there are so many opportunities for it within our galaxy alone, why isn’t there any evidence (outside of the History Channel) of extraterrestrial life?


Moreover, why haven’t we been visited by some extraterrestrial intelligence? After all, given the fact that our Universe is nearly 14 billion years old, while our galaxy itself is only a hundred-thousand light years from end-to-end, shouldn’t all of the potentially habitable planets have been visited, and colonized, by now?

A couple of years ago, I went through the estimates — both conservatively and liberally — of how rare or common intelligent life in the Universe is. But what I wanted to focus on, today, are the difficulties in even intelligently speaking about this question. First off, let’s start with the good news.

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