Copernicus
Nicolaus Copernicus (1473–1543) was a Polish astronomer who revolutionized the scientific world by proposing that the sun, rather than the Earth, is at the center of our solar system. This heliocentric model displaced centuries of geocentrism and established a new way to understand how planets move around their stars.
Copernicus' groundbreaking work built upon ancient Greek astronomical theories as well as his own observations and mathematical calculations. He published his theory in 1543 in On The Revolutions of Celestial Spheres, which provided evidence for a heliocentric universe with orbits being described by circles or combinations thereof instead of epicycles as used in Ptolemaic models. His publication also suggested reformulating timekeeping methods to account for variations due to planetary motion, such as leap years and other calendar adjustments.
His findings challenged traditional beliefs about astronomy but were not widely accepted until after he died, when Johannes Kepler began further developing them into what we now know today as modern astronomy. Today, the Copernican Revolution is considered one of the most important moments in history, which shifted humanity's understanding from an earth-centered view towards one based on scientific observation and reason, thus laying foundations for future advances in science and technology while helping create modern society itself.