This Day in Tech History

On This Day . . .

The Earth is Not Flat?


February 19, 1476:

Copernicua is Born

In the early 1500s, when virtually everyone believed Earth was the center of the universe, Polish scientist Nicolaus Copernicus proposed that the planets instead rotated around the sun. Although his model wasn’t completely correct, it formed a strong foundation for future scientists to build on and improve mankind’s understanding of the motion of heavenly bodies. Indeed, other astronomers built on Copernicus’ work and proved that our planet is just one world orbiting one star in a vast cosmos loaded with both, and that we’re far from the center of anything

Nicolaus Copernicus is born in Torun, a city in north-central Poland on the Vistula River. The father of modern astronomy, he was the first modern European scientist to propose that Earth and other planets revolve around the sun.


The cosmology of early 16th-century Europe held that Earth sat stationary and motionless at the center of several rotating, concentric spheres that bore the celestial bodies: the sun, the moon, the known planets, and the stars. From ancient times, philosophers adhered to the belief that the heavens were arranged in circles (which by definition are perfectly round), causing confusion among astronomers who recorded the often eccentric motion of the planets, which sometimes appeared to halt in their orbit of Earth and move retrograde across the sky.

Sometime between 1508 and 1514, he wrote a short astronomical treatise commonly called the Commentariolus, or “Little Commentary,” which laid the basis for his heliocentric (sun-centered) system. The work was not published in his lifetime. In the treatise, he correctly postulated the order of the known planets, including Earth, from the sun, and estimated their orbital periods relatively accurately.

Copernicus’ groundbreaking argument that Earth and the planets revolve around the sun led him to make a number of other major astronomical discoveries. While revolving around the sun, Earth, he argued, spins on its axis daily. Earth takes one year to orbit the sun and during this time wobbles gradually on its axis, which accounts for the precession of the equinoxes. Major flaws in the work include his concept of the sun as the center of the whole universe, not just the solar system, and his failure to grasp the reality of elliptical orbits, which forced him to incorporate numerous epicycles into his system, as did Ptolemy. With no concept of gravity, Earth and the planets still revolved around the sun on giant transparent spheres.


It was not until the early 17th century that Galileo and Johannes Kepler developed and popularized the Copernican theory, which for Galileo resulted in a trial and conviction for heresy. Following Isaac Newton’s work in celestial mechanics in the late 17th century, acceptance of the Copernican theory spread rapidly in non-Catholic countries, and by the late 18th century it was almost universally accepted.

To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge.
Nicolaus Copernicus


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