A paradigm shift in how science was conducted: Johannes Kepler
Debunked the geocentric theory and introduced the heliocentric theory of the universe: Nicolaus Copernicus
Burned at the stake for introducing the idea of infinite universe - that other stars were like our sun and could potentially also support life: Giordano Bruno
Introduced the geocentric model of the universe: Ptolemy
Discovered Jupiter's moons and the phases of Venus: Galileo Galilei