'More accurately than others' : Eratosthenes' measurement of the Earth's circumference (c.230BC)

Abstract

The aim of this project is to re-evaluate the results of Eratosthenes' calculations the circumference of the Earth through a reexamination of all of the available evidence - astronomical, philological, historical and archaeological. This, in turn, will allow for engagement with the long-running scholarly debate over this topic to be undertaken in order to identify any errors or omissions in these prior theories, and account for these errors. This project will examine the available data to compile the first multi-disciplinary re-evaluation of Eratosthenes' work in order to address two key research objectives: 1. Determine the size of the stade that Eratosthenes used in his calculations. 2. Determine the accuracy of Eratosthenes' calculation of the circumference of the Earth. As a result, this project will provide the first multi-disciplinary analysis of this important event in the history of astronomy and the ancient attempts to understand our place in a wider universe. Through a critical examination of the available evidence, it can be shown that Eratosthenes was using a stade of 180m in length in his determination of the Earth's circumference. A unit of this size has never been applied to an analysis of Eratosthenes' work before now, and constitutes an original contribution by this thesis. The use of a unit of this size is confirmed through a comparison of stated distances between locations in Iran, Afghanistan and Egypt that are attributed to Eratosthenes with 'on the ground' measurements obtained using satellite mapping software (Google Earth). This has also never been applied to the examination of Eratosthenes, and constitutes another original contribution of this research. Furthermore, an examination of several key ancient passages, which have been ignored by many previous scholars, demonstrates that the result of Eratosthenes' calculations was a circumference of around 224,000 stadia - as opposed to the 250,000 or 252,000 stade figures that form the basis of all prior studies into this topic - and that this was based upon a latitudinal distance, determined using sundials, between the two locations which formed a fundamental element of his determination of the size of the Earth. The results of this research show that Eratosthenes' calculations were highly accurate - with a margin of error of

Date of Award	2022
Original language	English