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dataflow·

> 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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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...

Staking claims, where corner posts were placed at half kilometer intervals, were usually paced on foot, estimating for canyons, stream crossings, and other diversions. Some claims were continuous up to 20km by 20 km. This was in complete wilderness, in the Yukon, British Columbia and so on. Pre GPS. Not that long ago! They used topographic maps for reference. It is amazing how accurate the claims were, when transferred to modern mapping systems.

Imagine what it took to make the highly accurate topo maps they relied on.

https://en.wikipedia.org/wiki/Great_Trigonometrical_Survey

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]: https://youtu.be/G8cbIWMv0rI?si=uRdlxGqBxxDTkUj6

We covered this literally this week in my intro to astronomy class, my prof said he paid a guy to walk the distance and measure it out.

And well enough that they ended up only a couple percent off

A very long piece of string.

That was for putting back the farm claims along the Nile. Professional rope stretchers did that.

This was paced.

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