Fill in the Blanks Who was Galileo GalileiOnline version Listen and complete by Juan Carlos Arias 1 four moon Earth Venus sun mathematics Science Jupiter Who Was Galileo Galilei ? Galileo Galilei ( February 15 , 1564 to January 8 , 1642 ) was an Italian astronomer , mathematician , physicist , philosopher and professor who made observations of nature . He also constructed a telescope and supported the Copernican theory , which supports a sun - centered solar system . Galileo was accused twice of heresy by the church for his beliefs , and wrote a number of books on his ideas . Galileo's contribution to our understanding of the universe was significant not only in his discoveries , but in the methods he developed and the use of to prove them . He is considered " The Father of Modern . " Telescope In the fall of 1609 he made the decision to turn his telescope toward the heavens . Using his telescope to explore the universe , Galileo observed the and found had phases like the moon , proving it rotated around the , which refuted the Aristotelian doctrine that the was the center of the universe . He also discovered and its moons .
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