3M views · Apr 24, 2009 · 6:42 · 4 HN recommenders · 4 mentions · discussed 2022–2024
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.
Why Hacker News points people here: HN commenters link it whenever the question of how the Earth's size was first measured comes up, calling it a wonderful explanation.
“Here is a wonderful video of Carl Sagan explaining it[0].”HN comment, 2023
“One of my favourite episodes of Cosmos centres around Eratosthenes’ calculation of the circumference of the Earth”
Cosmos episode on Eratosthenes' calculation of Earth's circumference
One of my favourite episodes of Cosmos centres around Eratosthenes’ calculation of the circumference of the Earth: this video
“The video has a good explanation of how it was done.”
Good explanation of how Eratosthenes estimated Earth's size
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 )
“Carl Sagan's explanation on Cosmos of Eratosthenes' discovery is great”
Sagan's explanation of Eratosthenes' discovery
Likely familiar to this crowd, but Carl Sagan's explanation on Cosmos of Eratosthenes' discovery is great: this video
“Here is a wonderful video of Carl Sagan explaining it[0].”
Sagan explaining how Earth's size was 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
