Did you ever wonder how did our ancestors measure the Earth's size during ancient times?
Ancient Greeks wondered about Earth's actual size. Aristarchus of Samos was said to be the first to try measuring Earth's circumference in 280 BC.
More than 2000 years ago, in Alexandria, Egypt. The Greek scholar, Eratosthenes, recorded the first nearly accurate measurements of Earth using an ingenious method.
Eratosthenes calculated the Earth's circumference using the angle of the sun's rays at the Syene (now Aswan) and Alexandria.
From his readings, Eratosthenes knew that on the day of the summer solstice, sunlight fell directly into a very deep well in Syene (now Aswan), Egypt. On this day he measured the shadow of a pole in Alexandria. He found that the sun's rays made an angle of 7.2°. Knowing that 7.2° is 1/50 of a circle, he multiplied the distance ( which is 5000 stadia or 925 km) between Alexandria and Syene (925 km x 50 = 46,250 km).
The presently accepted value is 40 075 km circumference, 12 756 km diameter, 6 378 km radius.
While Eratosthenes measurements 46 250 km circumference, 14 729 km diameter, 7 365 km radius.
This value is very close to the presently accepted value.
Scientist today measure Earth's circumference more accurately with better instruments, but they are still using Eratosthenes' method.
Earth's circumference is about 40 000 kilometers. Can you imaging how big it is?
If you travel by jet plane day and night without stopping, it will take you 42 hours or about two days to go around the world. This is how big our planet is.
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