Italian physicist, mathematician, astronomer, and philosopher who, by means of telescopic observation, disproved the Ptolomeaic theory of the universe. Works include: La Billancetta (1586), De Motu Antiquiora (1590), Le mecaniche (1600), Le operazioni del compasso geometrico et militare (1606), Sidereus Nuncius (1610), Discorso intorno alle cose che stanno in su l'acqua, o che in quella si muovono (1612), Istoria e dimostaziono intorno alle macchie solari (1613), Discorso del flusso e reflusso del mare (1616), Discorso delle Comete (1619), Il Saggiatore (1623), Dialogo sopra i due massimi sistemi del mondo (1632), and Discorsi e Dimostrazioni Matematiche, intorno a due nuove scienze (1638). For his Dialogo sopra i due massimi sistemi del mondo he was tried by the Inquisition and forced to recant. He was sentenced to house arrest, where he remained for the rest of his life, still continuing his scientific work.