4 HN users recommended this explainer4 months2022–2024score 4.5
Years with an HN recommendation, 2007–2026
HN commenters link it whenever the question of how the Earth's size was first measured comes up, calling it a wonderful explanation.
A short clip from Carl Sagan's Cosmos in which he explains how Eratosthenes measured the circumference of the Earth using shadows in two Egyptian cities. It is a clear, visual account of an ancient scientific feat.
“Here is a wonderful video of Carl Sagan explaining it[0].” (HN, 2023)
Carl Sagan talked about Eratosthenes in Cosmos[0] actually which is what I was thinking of. He was also able to make a good estimate of the size of the Earth as well. The video has a good explanation of how it was done. [0]( [this video] )
Good explanation of how Eratosthenes estimated Earth's size
I heard it was using a military unit’s standard marching pace to calculate the distance. Here is a wonderful video of Carl Sagan explaining it[0]. [0]: [this video]
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