Heliocentrism is the astronomical model that posits the Sun as the center of the universe, with the Earth and other planets revolving around it. This revolutionary idea challenged the long-standing geocentric model, which placed the Earth at the center, fundamentally changing our understanding of the cosmos. The shift to heliocentrism marked a pivotal moment in scientific thought, laying the groundwork for modern physics and the methods of observation and experimentation that define it today.