Physicist Enrico Fermi famously asked the question "Where are they?" to express his surprise over the absence of any signs for the existence of other intelligent civilizations in the Milky Way Galaxy. Although many potential resolutions to this so-called “Fermi paradox” have been suggested over the years, there is still no consensus on which one, if any, is correct. The question of whether we are alone in the Milky Way (or in the universe at large) remains, however, one of the most intriguing questions in science in general, and in astronomy in particular.
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