The Fermi Paradox illustrates the apparent contradiction between the high likelihood that there is intelligent life somewhere out there and our lack of contact (or proof of contact) with any of those civilizations. The Paradox rests on the ideas that there are billions of stars and galaxies much, much older than ours, and that many of them contain habitable planets (the Kepler telescope has confirmed this), and some of those must support life. And where there’s intelligent life, there’s technology, particularly in terms of interstellar travel.
The key question, then, of the Fermi paradox is: why haven’t we been visited by aliens? In a recent interview with Business Insider, astrophycisist Neil deGrasse Tyson shares some “unorthodox” thoughts about why that might be.