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Long before the era of satellites and modern measurements, ancient scientists were already trying to understand the circumference of the Earth. Using only basic concepts of geometry, Eratosthenes was able to calculate the circumference of the Earth with remarkable accuracy more than two thousand years ago.
In the century III BC, a Greek mathematician made an astonishing discovery. With a simple piece of wood, Eratosthenes managed to calculate the circumference of the Earth with great precision.
His method, based on observations and mathematical calculations, anticipates by more than two thousand years the modern measurements made by satellites.
The simple and ingenious experiment to measure the circumference of the Earth
Eratosthenes was head of the Library of Alexandria and had access to vast knowledge.
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He learned that in Syene, a city south of Alexandria, the Sun was directly overhead at noon on the summer solstice. On that date, no object cast a shadow vertically.
Curious, he wanted to test whether the same thing happened in Alexandria. On June 21, he stuck a stick in the ground and waited.
At noon, he noticed that the object cast a shadow at an angle of 7 degrees. This indicated that the Earth was not flat, but curved.
Mathematical reasoning
The idea that the Earth was a spheroid had existed since Pythagoras, around 500 BC, and Aristotle had provided further evidence. But Eratosthenes went further and decided to measure the planet.
Knowing that Syene and Alexandria were at different latitudes, he deduced that the angular difference of the shadows could reveal the size of the Earth.
Since the shadow in Alexandria indicated an angle of 7,2 degrees, he compared this value with the complete division of a circle, which is 360 degrees.
The proportion was simple: 7,2 degrees corresponds to 1/50 of the total circumference. Therefore, it was enough to measure the distance between Alexandria and Syene and multiply it by 50.
The surprising result
To get the distance between the cities, Eratosthenes hired a man to travel it. The messenger found a value of approximately 5.000 stadiums, something around 800 kilometers.
By multiplying 800 km by 50, Eratosthenes arrived at an incredible result: 40.000 kilometers. This measurement is extremely close to the actual circumference of the Earth, which we now know to be 40.030 km.
Eratosthenes' method demonstrated that science can make great discoveries with simple tools and careful observation. With just a stick and his wits, he was able to calculate the size of the planet with astonishing accuracy for the time.
With information from independent.
