Who discovered that the Earth is round

A view of Earth from the space shuttle Discovery shows the intense glow of the late afternoon sun over the Andes Mountains and thick illuminated clouds. (Bettmann/Getty Images)

Saying that the earth is round might seem like saying that the sky is blue, which seems like common sense these days. Prior to the advent, the sky was never blue. These pictures show that this planet is actually a sphere. How did people do this way back in 500 BC? Did you find it?

Other Pythagorean Theorems

Much of the credit for proving that the earth is round goes to Pythagorean, who is best known for his famous theorem that must be learned in school. He developed the first documented theory that the Earth is round, based on observations of all other round celestial bodies visible to the human eye. Aristotle later took up this idea, pointing out that during a lunar eclipse the moon casts a circular shadow. He also noted that as one moved north or south, the stars moved through strange positions, and some constellations changed or disappeared entirely.

Eratosthenes of Cyrene

But these were all mere observations, with no real math or verifiable science to back them up. Meet Eratosthenes of Cyrene, Greek mathematician, astronomer, and chief librarian of the Library of Alexandria, Egypt. One day, he heard that the well in the city of Siene (now Aswan) is illuminated by the sun from directly above, so that even in the middle of summer it casts no shadow. On the following day of the summer solstice he decided to measure the shadow cast with a stick when the sun was exactly in the middle of the sky, and the value he determined was 7 degrees.

A simplified version of Cleomedes’ measurement of the circumference of the Earth, based on the approximation that Syene lies on the Tropic of Cancer and is on the same meridian as Alexandria. (CMG Lee/Wikimedia Commons)

The round earth

In a moment of great inspiration, Eratosthenes realized that he could calculate the circumference of the earth based on his knowledge of the distances between cities and the 7 degree curve, and the surveyors between Count your steps literally. Eratosthenes calculated that the circumference of the earth he is 24,000 miles. This is surprisingly close to the actual circumference of 24,900 miles, given how rudimentary his experiments were.

Since then, apart from some disagreements from some European religious communities, most people agree that the world is round. Despite myth, even Christopher Columbus knew this. The only reason the Spanish nobility funded it was to find a new route to the East, knowing that the world was a globe to travel.