Fermi paradox
The Fermi paradox: life elsewhere looks likely, yet the universe we observe looks empty. Enrico Fermi, whose name it carries, never published a word about it.
In the summer of 1950, Enrico Fermi asked "but where is everybody?" He then ran rough odds on planets like Earth, on life, on humans and on how long high technology lasts, and decided Earth ought to have had visitors long ago. Our searches have barely begun: one estimate likens the share of the search space covered so far to a large hot tub set against all of Earth's oceans. Yet Fermi never published a word on the question.
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