Carl Sagan - Cosmos - Eratosthenes
Why Hacker News recommends it
HN commenters link it whenever the question of how the Earth's size was first measured comes up, calling it a wonderful explanation.
What it is
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.
Recommended by 4 HN commenters across 4 different months, 2022 to 2024.
What Hacker News said
Strong rec ubutler · 2024-03 · on “Webb and Hubble confirm Universe's expansion rate”
One of my favourite episodes of Cosmos centres around Eratosthenes’ calculation of the circumference of the Earth: [this video]
Recommends hotpotamus · 2022-02 · on “Zen and the Art of Talking to Conspiracy Theorists”
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] )
Recommends jamesgill · 2023-01 · on “Interesting”
Likely familiar to this crowd, but Carl Sagan's explanation on Cosmos of Eratosthenes' discovery is great: [this video]
Recommends kemotep · 2023-08 · on “How was the size of Earth first measured?”
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]