Over 2,000 A few years in the past, nearly each educated human being knew that the Earth was spherical. Because it seems, there are some fairly apparent clues. Touring south, you may see stars and constellations you’ve got by no means seen earlier than (as a result of they’re obstructed by the Earth’s curvature). When a ship enters a port, you’ll be able to see the highest of the ship earlier than you see the underside (as a result of the ocean floor is curved). Lastly, when the Earth’s shadow falls on the Moon throughout a lunar eclipse, the shadow turns into a circle. I imply, come on!
However that is spectacular. Round 240 BC, the Greek mathematician Eratosthenes, director of Egypt’s well-known Library of Alexandria, got here up with an excellent strategy to calculate the radius of the spherical Earth. You are able to do it too, and it does not require any particular gear. We’ll present you learn how to measure the scale of the Earth utilizing Lego items.
After all, Eratosthenes did not have Legos. However he knew that at midday on the day of the summer season solstice, the solar would shine straight right into a vertical effectively in Syene, Egypt. This implies the solar is straight overhead. So what did he do? He caught a stick into the bottom in Alexandria and seen that at midday that day it solid a shadow signifying the solar. It wasn’t like that Over there.
Within the photograph under, I am utilizing a syene pole (clearly to not scale) as an alternative of a effectively, however the thought is similar. You’ll be able to see that despite the fact that the Solar coincides with the Syene pole, it doesn’t coincide with the Alexandria pole. This will merely imply that the Earth is curved. However sure, he knew that.
Illustration: Rhett Alleyne
