Overview
Murray Leinster's 1945 novelette "First Contact" established the term "first contact" in science fiction, although the theme had previously appeared in e.g. H. G. Wells' The Time Machine (1895), The War of the Worlds (1898) and The First Men in the Moon (1901).
Of many variations of the trope, one may recognize the subclasses of the actual interstellar meeting of two civilizations and the "message from space" one.
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