Ancient Greeks Were Smart Enough to Determine that the Earth Was Round.

Even in 2019, if you still believe the Earth is flat, you are not alone. There is still a group of people out there, albeit small, that believe that the earth is Flat and that Round-Earth evidence is just a hoax organized by the government to fool everyone. Theories supporting the Round shape of the Earth started surfacing about 2000 years ago when satellites were not available but Flat-Earth supporters still dispute available pieces of evidence given the “fact” that the horizon doesn’t appear to curve.

How Round Was Earth?

Historically, in 500 B.C, the polymath Pythagoras was the first to propose a Spherical Earth, and even the ancient Greeks had the same idea before they found concrete evidence. According to Pythagoras, the sphere was the appropriate shape for the Earth, based mainly on his observations of the beauty of nature. His Round-Earth theories were made even more popular a century later by Plato’s support for the idea. And as one of the most famous Philosophers of all time, Plato’s influence further solidified Round-Earth theories.

In terms of supplying proofs, Aristotle was the one that actually went to great lengths. Within his means and given the available technology of the time, in his book “On the Heavens” in 350 B.C., Aristotle pointed us towards several Round-Earth pieces of evidence like the round shadow of the Earth on the moon during lunar eclipses regardless of the position of the Earth in its rotation.

He further stated that:

Not only that the earth is circular in shape, but also that it is a sphere of no great size: for otherwise, the effect of so slight a change of place would not be quickly apparent.

Years later, Eratosthenes comes into the picture and changes the whole story for everyone. He did not just supply evidence of the round nature of the earth, he even released measurements with a stick via his observation of the sun.

A Smart Man, Some Common Sense and A Stick

Because of his immense contributions to the fields of Mathematics, Geography and the Sciences, Eratosthenes turned out to be one of the most prominent scholars of his own time. For Eratosthenes, the main goal was to produce a map of the entire world and the size of the Earth was going to be the first step. At his prime, at about 240 B.C, Eratosthenes was the chief librarian of the library of Alexandria – the Wikipedia of the time.

How did he arrive at the measurement of the earth?

The story goes that Eratosthenes had heard of the city of Syene, which had a special geographical feature, that at noon time during the summer solstice when the sun is directly overhead, sunlight illuminated the entire bottom of a well without casting any shadows. To experiment in Alexandria, Eratosthenes used a stick. He placed a stick upright in the ground at noontime during the summer solstice and the sun actually cast a shadow at an angle of 7.2 degrees.

With the degree measurement above, what was left to measure the circumference of the earth was only a few more calculations by Eratosthenes but he needed the distance between Alexandria and Seyne. To achieve this, he went ahead to hire some professional walkers – bematists. These were people who walked for a living and could measure their steps. They found that the distance between Seyne and Alexandria was about 5,000 stadia. In today’s measurement, 5,000 stadia is about 500 and 600 miles (800 and 900 kilometers).

With that, he could do a quick back-of-the-scroll calculation. Since the sun hit straight-on in Syene and at a 7.2-degree angle in Alexandria, the distance between them should be a 7.2-degree chunk of the 360-degree sphere that is the Earth. He also knew that that 7.2-degree chunk was roughly 500 miles long. It turns out that 7.2 is to 360 what 500 is to 25,000 — and that was his answer. The Earth was 25,000 miles (40,000 kilometers) around.

So, in conclusion, many of Eratosthenes’s assumptions were faulty and rough, no doubt, but he was only off by 100 miles. Now we know that the Earth is 24,901 miles which is about 40,075 kilometers around its equator. Given the limitations of the technology of the day, Eratosthenes did quite a lot of work with just a stick. Hence his new title bestowed upon him by me – The Simple Smart Man With A Stick.

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