 Galileo 's championing of heliocentrism and Copernicanism was controversial during his lifetime , when most subscribed to either geocentrism or the Tychonic system . He met with opposition from astronomers , who doubted heliocentrism because of the absence of an observed stellar parallax . The matter was investigated by the Roman Inquisition in 1615 , which concluded that heliocentrism was " foolish and absurd in philosophy , and formally heretical since it explicitly contradicts in many places the sense of Holy Scripture . " Galileo later defended his views in Dialogue Concerning the Two Chief World Systems , which appeared to attack Pope Urban VIII and thus alienated him and the Jesuits , who had both supported Galileo up until this point . He was tried by the Inquisition , found " vehemently suspect of heresy " , and forced to recant . He spent the rest of his life under house arrest . While under house arrest , he wrote one of his best @-@ known works , Two New Sciences , in which he summarized work he had done some forty years earlier on the two sciences now called kinematics and strength of materials . 
