Long before the first satellites were sent to space in the 1960’s in order to prove that the Earth is indeed round, Ancient Greek mathematician Eratosthenes had found the proof using a simple …stick. And that was more than 2,000 years ago.
Eratosthenes (276-194 BC) carried out an experiment that not only confirmed the planet’s spherical shape, but also allowed him to calculate its circumference at 40,030 km.
As explained by Business Insider, the attention of the mathematician, who was clearly way ahead of his time, was sparked when he discovered that no vertical shadows were cast at noon on the summer solstice at the city of Syene [Cyrene, Libya].
Wondering if it were the same case in Alexandria, where he was based, Eratosthenes stuck a stick in the ground on the same date and lo and behold, there was a shadow and it measured around seven degrees.
Since the difference in shadow length is 7 degrees in Alexandria and Syene, that means the two cities are 7 degrees apart on Earth’s 360-degrees surface.
According to businessinsider, Eratosthenes hired a man to pace the distance between the two cities and learned they were 5,000 stadia apart, which is about 800 kilometers.
He could then use simple proportions to find the Earth’s circumference — 7.2 degrees is 1/50 of 360 degrees, so 800 times 50 equals 40,000 kilometers. And just like that, a man 2200 years ago found the circumference of our entire planet with just a stick and his brain.
And just like that, a man 2200 years ago found the circumference of our entire planet with just a stick and his brain.
This confirmed the speculation that the Earth is round – although he likely already knew that thanks to theories brought to the fore by Pythagoras and further validated by Aristotle a couple of hundred years later.
“So he used his noodle, some mathematics wizardry and managed to work out that the Earth’s circumference is roughly 40,000 kilometers, long before anyone had even invented electricity or calculators, let alone space satellites,” notes ladbible.
