How was the size of Earth first measured? (2015)
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How was the size of Earth first measured? (2015)
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Re: How was the size of Earth first measured? (2015)
#2> the distance from Alexandria to Syene -- believed to have been about 515 miles
Even this part sounds amazing to me. How did they measure distances this long back then?
Re: How was the size of Earth first measured? (2015)
#3> the distance from Alexandria to Syene -- believed to have been about 515 miles Even this part sounds amazing to me. How did they measure distances this long back then?
Land along the Nile was heavily surveyed, yearly, to ensure its course changes were recorded in landownership.
> Long distances were measured by professional distance walkers, called bematists, who walked at a very regular pace and counted each step. Shorter distances were measured with lengths of knotted rope by men called harpedonaptai, which means “rope stretchers”
https://www.maa.org/press/periodicals/convergence/eratosthen...
Re: How was the size of Earth first measured? (2015)
#4> the distance from Alexandria to Syene -- believed to have been about 515 miles Even this part sounds amazing to me. How did they measure distances this long back then?
A very long piece of string.
Re: How was the size of Earth first measured? (2015)
#5> the distance from Alexandria to Syene -- believed to have been about 515 miles Even this part sounds amazing to me. How did they measure distances this long back then?
And well enough that they ended up only a couple percent off
Re: How was the size of Earth first measured? (2015)
#6Classic Carl Sagan clip relaying this story: https://m.youtube.com/watch?v=8hZl3arO7SY
Re: How was the size of Earth first measured? (2015)
#7Eratosthenes was (IMO) pretty amazing in the range of interests and accomplishments: https://en.wikipedia.org/wiki/Eratosthenes
His name came up recently on another post on a very different topic: https://news.ycombinator.com/item?id=37236099
Re: How was the size of Earth first measured? (2015)
#8Given the large distance between the cities, how did they communicate to confirm that the sun was indeed overhead at particular time and date?
Re: How was the size of Earth first measured? (2015)
#9> the distance from Alexandria to Syene -- believed to have been about 515 miles Even this part sounds amazing to me. How did they measure distances this long back then?
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Re: How was the size of Earth first measured? (2015)
#10> the distance from Alexandria to Syene -- believed to have been about 515 miles Even this part sounds amazing to me. How did they measure distances this long back then?
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].