---
title: Eratosthenes' Calculation of the Earth's Circumference
author: Lookang
source: https://www.worldhistory.org/image/1133/eratosthenes-calculation-of-the-earths-circumferen/
format: machine-readable-alternate
license: Creative Commons Attribution-ShareAlike (https://creativecommons.org/licenses/by-sa/4.0)
updated: 2023-02-10
---

# Eratosthenes' Calculation of the Earth's Circumference

_Authored by Lookang_

## Image File

[![Eratosthenes' Calculation of the Earth's Circumference](https://www.worldhistory.org/uploads/images/1133.png)](https://www.worldhistory.org/uploads/images/1133.png)

## Image Caption

An illustration showing [Greek](https://www.worldhistory.org/disambiguation/greek/) scientist [Eratosthenes](https://www.worldhistory.org/Eratosthenes/)' method for calculating the circumference of the Earth. By measuring the angle of a shadow in one location ([Alexandria](https://www.worldhistory.org/alexandria/)) and comparing at the same time with a second point (Syene) where the sun was directly overhead and created no shadow and by calculating the distance between these two points, Eratosthenes was able to calculate the curvature of the earth between the two points and extrapolate that figure to calculate the circumference of the earth. He arrived at a figure only 15% inaccurate and that probably due to the unreliable distance figure between the two points rather than any error in his mathematics.

## Cite This Work

### APA
Lookang. (2013, April 05). Eratosthenes' Calculation of the Earth's Circumference. *World History Encyclopedia*. <https://www.worldhistory.org/image/1133/eratosthenes-calculation-of-the-earths-circumferen/>
### Chicago
Lookang. "Eratosthenes' Calculation of the Earth's Circumference." *World History Encyclopedia*, April 05, 2013. <https://www.worldhistory.org/image/1133/eratosthenes-calculation-of-the-earths-circumferen/>.
### MLA
Lookang. "Eratosthenes' Calculation of the Earth's Circumference." *World History Encyclopedia*, 05 Apr 2013, <https://www.worldhistory.org/image/1133/eratosthenes-calculation-of-the-earths-circumferen/>.

## License & Copyright

[Original image](http://en.wikipedia.org/wiki/File:Eratosthenes.png) by [**Lookang**](http://en.wikipedia.org/wiki/File:Eratosthenes.png). Submitted by [Mark Cartwright](https://www.worldhistory.org/user/markzcartwright/ "User Page: Mark Cartwright"), published on 05 April 2013. The copyright holder has published this content under the following license: [Creative Commons Attribution-ShareAlike](https://creativecommons.org/licenses/by-sa/4.0deed.en). This license lets others remix, tweak, and build upon a work even for commercial reasons, as long as they credit the author and license their new creations under the identical terms. When republishing on the web a hyperlink back to the original content source URL must be included. Please note that content linked from this page may have different licensing terms.