Proving Earth's Spherical Shape: 5 irrefutable Evidences vs. the Flat-Earth Theory
In the year 240 BCE, a scientist named Eratosthenes made a remarkable discovery that would change our understanding of the Earth's shape. Working at the Library of Alexandria, he was intrigued by a peculiar observation: on the same day, the angle of the Sun's shadow in Alexandria was significantly different from that in the town of Syene (modern-day Aswan in southern Egypt).
Eratosthenes knew that on this particular day, the Sun shone directly overhead in Syene, illumininating a well without casting a shadow. However, in Alexandria, the well cast a shadow, indicating that the Sun's rays were angled. By measuring the angle of the shadow in Alexandria (approximately 7.2°, or 1/50th of a complete circle), he realised that the Earth must be round and that the distance between the two cities was approximately 5,000 stadia.
Using this information, Eratosthenes was able to estimate the Earth's circumference. While the exact length of a stadia varied in the ancient world, Eratosthenes' measurement placed the Earth's circumference between 38,000 and 46,000 kilometres. This was a significant improvement over previous estimates, which had placed the Earth's circumference at around double its actual size.
The Greeks had long been aware that the lengths of shadows differed depending on one's location in the Northern Hemisphere. It was Greek natural philosophers Empedocles and later Aristotle who first wrote about the round Earth around 430 BCE, based on observation of the curved shadow during a lunar eclipse. Aristotle systematically explained and supported the idea based on empirical observation.
The first direct proof that Earth was not flat but a spherical globe came in 1519, during the Magellan-Elcano expedition's circumnavigation of the globe. Today, we know that the Earth's circumference is approximately 40,007 kilometres, with the poles measuring around 40,008 kilometres. Eratosthenes' groundbreaking measurement remains a testament to the power of observation and scientific inquiry.
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