Seleucus of Seleucia was an ancient astronomer who defended heliocentrism, arguing that Earth orbits the Sun and rotates on ...

In 1508, Nicolaus Copernicus developed a celestial model of a heliocentric planetary system that transformed the way we view the universe. This bold theory, contrary to the geocentric ...

Dallas explains the geocentric model and then the heliocentric model developed by Kepler, Copernicus and Galileo. However, the orrery does not have the correct scale. Dallas goes outside ...