Answer:
Nicholas Copernicus was the first scientist to come with the idea that the sun was at the center of the solar system. Galileo had accepted this heliocentric model. But it was the observations of Venus, carried out by the Galileo that proved this theory. He used the telescope for proving the theory. He saw that Venus also went through phases similar to the moon and this movement was possible only if Venus was revolving around the sun. He concluded that it travels around the sun not earth and at times passes behind it. His observations proved that the Sun was at the center of the solar system.