An astronomer's faint lines on Mars convinced a generation aliens built canals
Mapping Mars in 1877, Giovanni Schiaparelli recorded long straight features he called 'canali' — Italian for channels. Mistranslated into English as 'canals', the word let Percival Lowell build a theory of an intelligent Martian civilisation irrigating a dying planet. Better telescopes in the early 1900s showed the lines were an optical illusion from eyes connecting faint, scattered dots into straight lines; Mariner 4's 1965 flyby found only craters.