How Eratosthenes Calculated the Earth's Size in Ancient Greece

Discover how Eratosthenes used geometry to measure Earth's size in 240 B.C. with remarkable accuracy.

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Eratosthenes, a Greek mathematician and astronomer, was the first to calculate the size of the Earth around 240 B.C. He achieved this using simple geometry and observations of the sun's angles at two different locations in Egypt, Alexandria and Syene. His method involved measuring the shadow cast by a stick at noon during the summer solstice and comparing it with the no-shadow observation in Syene. This innovative approach led to remarkably accurate results for his time.

FAQs & Answers

  1. What method did Eratosthenes use to measure the Earth? Eratosthenes used geometry and the angle of shadows from sticks at two locations in Egypt during the summer solstice.
  2. What were the locations involved in Eratosthenes' calculation? He conducted his measurements in Alexandria and Syene (modern-day Aswan) in Egypt.
  3. Why was Eratosthenes' calculation significant? It was one of the first known estimations of Earth's size, showcasing the use of geometry in scientific inquiry.
  4. What year did Eratosthenes calculate the size of the Earth? Eratosthenes calculated the size of the Earth around 240 B.C.

Watch More

For more insights into the history of science and mathematics, check out our videos on other great thinkers like Archimedes and Ptolemy, or explore the evolution of geographic knowledge.

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