Seventeenth-century astronomer Galileo Galilei is widely credited with convincing major church leaders and prominent scientists that the sun, not the Earth, was the center of the solar system. Galileo was the first astronomer to study astronomy with a telescope, which helped him validate Nicolaus Copernicus' early 16th-century heliocentric theories.
Prior to Copernicus, astronomers believed in the geocentric model of the solar system, which suggested that Earth was central. Copernicus studied with the naked eye and published his heliocentric theories in the early 1500s. His work was not highly regarded until Galileo validated many of his theories. Galileo initially met resistance from astronomers and church leaders who had long subscribed to Aristotle's philosophy that the sun and other planets orbited the Earth.