June 19, 240 B.C.: The Earth Is Round, and It’s This Big
So how big is 252,000 stades? Depending on which classical source you trust, it’s somewhere between 24,663 and 27,967 miles. The accepted figure for equatorial circumference today is 24,902 miles. Pretty darn good for a guy without modern measurement tools.
Eratosthenes went further and computed the tilt of the Earth’s axis to within a degree. He also deduced the length of the year as 365Â¼ days. He suggested that calendars should have a leap day every fourth year, an idea taken up two centuries later by Julius Caesar.
Great article. Because Eratosthenes did not “back up” his data and the library of Alexandria was destroyed, more than a thousand years passed before people started to accept that the earth is round…