Steve Donoghue at Open Letters Monthly:
Named after physicist Enrico Fermi, the paradox asks a simple question: where are the aliens? If the Milky Way has hundreds of billions of stars, millions of them millions of years older than Earth’s, and if even a tiny fraction of those stars have life-bearing planets, and if even a fraction of those planets developed sophisticated technology, even the most severe mathematical parsing should result in parking lots full of aliens, or at least museums full of their ancient relics. Even hobbled by the limitation of light speed, this paradox complains, there should be at least hundreds of alien civilizations that proved out the L in the Drake Equation and either came visiting – to conquer, colonize, or just sightsee – or sent mechanical probes to do it for them.
Instead, nothing. Entire arrays of gigantic radio telescopes have been probing the night sky for decades, spacecraft have been launched, and yet, as of this writing, there’s been no hint of life anywhere, and no hint that life has ever been anywhere in the past. The Drake Equation makes such life all but inevitable; the Fermi Paradox points out its resounding absence; the questing human spirit is caught somewhere in between.