Flat Earthers 101

Welcome to Flat Earther’s 101.

There is no need for you to go into space to discover the circumference of the Earth. I say this because I also hear that there are many flat earth believers who think that we have not been to the moon either. No need to get to space to learn that the earth is not flat.

Over 2000 years ago, the mathematician Eratosthenes had heard that in Syene, a city south of Alexandria, cast no vertical shadows at noon on the summer solstice, the longest day of the year. The reason for this is simply that the sun was right overhead. He wondered if this was also true in Alexandria.

So, on 21 June, he pushed his walking stick directly to the ground and waited to see if a shadow was cast at noon. He could clearly see that the rod created a shadow.

This left him to posit, that if the sun's rays arrive at the same angle at the same time of day and a stick in Alexandria casts a shadow, while a stick in Syene does not, it means that the surface of the earth is curved. Eratosthenes decided to sit and ponder this for a spell.

As a mathematician, what remained for Eratosthenes was to do some calculations to discover the circumference of the Earth. Thank to Pythagorus (500BC), who came before Eratosthenes, gave us the knowledge of his Pythagorean theorem and what is algebra, geometry and the law of cosines. He is also known for the power of the number three. He found this to be "ideal number" because it had a beginning, middle, and end. I was also the smallest number of points that could be used to define a plane triangle, which at the time people revered as a symbol of the god Apollo.

Pythagorus found that the difference of the shadow is 7 degrees in Alexandria and Syene, this meant that 7 degrees separated the two cities on the surface compared to the Earth's 360 degrees. The story goes that Eratosthenes hired a man to travel the distance between the two cities, and discovered that they were separated by 5000 stadia, a unit of measure at that time, which is equivalent to 800 km. Due to the regular caravan journeys of the day it is likely that he was already aware of the distance.

He then used simple proportions to find the circumference of the Earth: 7.2 degrees is 1\50 of 360 degrees, so 800 times 50 equals 40,000 km. Through modern day technology, geo location and more modern precision means of measuring we now know that the circumference of the earth is 40,075km.

Pythagorus found the circumference of the Earth using his walking stick and his brain.