As Enrico Fermi famously once said, "Where is everybody"?" These words were uttered in the summer of 1950 when the search for extraterrestrial intelligence (SETI) was heating up. They also captured the frustrations and unresolved questions surrounding the existence of extraterrestrial life.

At the time, scientists were of the belief that statistically speaking, life had to be plentiful in our Universe. This is still something of a consensus, seeing as how the Universe is so very, very big and there are countless planets out there for life to take root on.

And yet, all efforts to find that life so far have produced nothing - at least, nothing definitive. What these efforts have done is given our greatest scientific minds the opportunity to test various methods, theoretical frameworks, and the purpose of the search itself.

So to build on the words of the late and great Enrico Fermi, let's take a look at the history of SETI so far and ask the question, "What have we learned?"

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