How Did the Ancient Greeks Measure the Circumference of the Earth?

Updated on May 9, 2017
1701TheOriginal profile image

Leonard Kelley holds a bachelor's in physics with a minor in mathematics. He loves the academic world and strives to constantly explore it.


The first recorded mention of the Earth’s length around its middle comes from Aristotle, who claimed it was 400,000 stadia in his On the Heavens II. That unit is mentioned by Pliny when he equated 40 of them to 12,000 royal cubits, of which each is about 0.525 meters. Therefore, 1 stadia is 300 cubits which is 157.5 meters which is about 516.73 feet. Therefore, Aristotle had the Earth’s circumference at about 39,146 miles, assuming this was the stadia he referenced. Turns out many different people considered a stadia to be different lengths, so we are not 100% sure Aristotle meant the modern value we find. He didn’t mention how he arrived at this number, but it is likely a Greek source since we don’t know of any Egyptian or Chaldean measurements of the sort at that time and also because no historians can see Aristotle being influenced by outside sources for this measurement. Another value we are not certain about comes from Archimedes who stated a value of 300,000 stadia, or about 29,560 miles. He most likely used some distance data of features in the Mediterranean compiled by Dicaearchus of Messana but again we are not sure as to his method (Dreyer 173, Stecchini).


The first known mathematical method was done by Eratosthenes of Alexandria, who lived from 276-194 BC. While his original work has been lost, Kleomedes has the event recorded. He looked at the position of the Sun at the Summer Solstice at different locations along the same meridian. When at Cyrene (which is south of Egypt), Eratosthenes looked at a vertical pit in the ground and saw it had no shadow, indicating that the Sun was directly at the zenith (which is directly above you), but at Alexandria (north of Cyrene the distance of the shadow in the pit implied that the arc difference from the zenith was 1/50 “the circumference of the heavens,” aka the sky. Using the Sun’s rays as roughly parallel lines, one can show that the angle between the two locations must be the same as the angle measured in Cyrene. Coupling this with the distance between the two cities at about 5,000 stadia gives a circumference of 250,000 stadia, or roughly 24,466 miles. Not bad, considering that the actual value is about 24,662 miles! Kleomedes was later able to show that a similar figure was reached when using the Winter Solstice, surprise surprise. It should be mentioned many scholars doubt the veracity of Eratosthenes and to this day no consensus has been reached on if Eratosthenes was truthful or a liar about his measurements. Why is this the case? Some details do not line up in regards to latitude and longitude and the supposed error that was taken into account could not have been found with the tools Eratosthenes had at the time. More than likely, Eratosthenes knew of the value and retroactively wanted to show that a mathematical model would also provide the same number (Dreyer 174-5, Pannekock 124).

An alternate method used was implemented by Rosidonius and also recorded by Kleomedes. Here, the star Canopus was recorded at the time it hit the horizon when at Rhodes. Comparing this to where the star was at the same time at Alexandra (7.5 degrees above) and using some right triangle trigonometry implied that the difference was in fact the change in latitude and then using the distance between the two locations led to a value of 240,000 stadia, or 23,488 miles (Pannekock 124).

Not bad for cultures without modern technology. We see time and time again that with some foresight and perseverance, we can find relatively accurate results of some difficult numbers. Now, what else can we do…

Works Cited

Dreyer, J.L.E. A History of Astronomy. Dover, New York: 1901. Print. 173-5

Pannekick, A. A History of Astronomy. Barnes & Noble, New York: 1961. Print. 124.

Stecchini, Livio C. Metrum, n.d. Web. 25 Nov. 2016.

© 2017 Leonard Kelley


    0 of 8192 characters used
    Post Comment

    No comments yet.


    This website uses cookies

    As a user in the EEA, your approval is needed on a few things. To provide a better website experience, uses cookies (and other similar technologies) and may collect, process, and share personal data. Please choose which areas of our service you consent to our doing so.

    For more information on managing or withdrawing consents and how we handle data, visit our Privacy Policy at:

    Show Details
    HubPages Device IDThis is used to identify particular browsers or devices when the access the service, and is used for security reasons.
    LoginThis is necessary to sign in to the HubPages Service.
    Google RecaptchaThis is used to prevent bots and spam. (Privacy Policy)
    AkismetThis is used to detect comment spam. (Privacy Policy)
    HubPages Google AnalyticsThis is used to provide data on traffic to our website, all personally identifyable data is anonymized. (Privacy Policy)
    HubPages Traffic PixelThis is used to collect data on traffic to articles and other pages on our site. Unless you are signed in to a HubPages account, all personally identifiable information is anonymized.
    Amazon Web ServicesThis is a cloud services platform that we used to host our service. (Privacy Policy)
    CloudflareThis is a cloud CDN service that we use to efficiently deliver files required for our service to operate such as javascript, cascading style sheets, images, and videos. (Privacy Policy)
    Google Hosted LibrariesJavascript software libraries such as jQuery are loaded at endpoints on the or domains, for performance and efficiency reasons. (Privacy Policy)
    Google Custom SearchThis is feature allows you to search the site. (Privacy Policy)
    Google MapsSome articles have Google Maps embedded in them. (Privacy Policy)
    Google ChartsThis is used to display charts and graphs on articles and the author center. (Privacy Policy)
    Google AdSense Host APIThis service allows you to sign up for or associate a Google AdSense account with HubPages, so that you can earn money from ads on your articles. No data is shared unless you engage with this feature. (Privacy Policy)
    Google YouTubeSome articles have YouTube videos embedded in them. (Privacy Policy)
    VimeoSome articles have Vimeo videos embedded in them. (Privacy Policy)
    PaypalThis is used for a registered author who enrolls in the HubPages Earnings program and requests to be paid via PayPal. No data is shared with Paypal unless you engage with this feature. (Privacy Policy)
    Facebook LoginYou can use this to streamline signing up for, or signing in to your Hubpages account. No data is shared with Facebook unless you engage with this feature. (Privacy Policy)
    MavenThis supports the Maven widget and search functionality. (Privacy Policy)
    Google AdSenseThis is an ad network. (Privacy Policy)
    Google DoubleClickGoogle provides ad serving technology and runs an ad network. (Privacy Policy)
    Index ExchangeThis is an ad network. (Privacy Policy)
    SovrnThis is an ad network. (Privacy Policy)
    Facebook AdsThis is an ad network. (Privacy Policy)
    Amazon Unified Ad MarketplaceThis is an ad network. (Privacy Policy)
    AppNexusThis is an ad network. (Privacy Policy)
    OpenxThis is an ad network. (Privacy Policy)
    Rubicon ProjectThis is an ad network. (Privacy Policy)
    TripleLiftThis is an ad network. (Privacy Policy)
    Say MediaWe partner with Say Media to deliver ad campaigns on our sites. (Privacy Policy)
    Remarketing PixelsWe may use remarketing pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to advertise the HubPages Service to people that have visited our sites.
    Conversion Tracking PixelsWe may use conversion tracking pixels from advertising networks such as Google AdWords, Bing Ads, and Facebook in order to identify when an advertisement has successfully resulted in the desired action, such as signing up for the HubPages Service or publishing an article on the HubPages Service.
    Author Google AnalyticsThis is used to provide traffic data and reports to the authors of articles on the HubPages Service. (Privacy Policy)
    ComscoreComScore is a media measurement and analytics company providing marketing data and analytics to enterprises, media and advertising agencies, and publishers. Non-consent will result in ComScore only processing obfuscated personal data. (Privacy Policy)
    Amazon Tracking PixelSome articles display amazon products as part of the Amazon Affiliate program, this pixel provides traffic statistics for those products (Privacy Policy)
    ClickscoThis is a data management platform studying reader behavior (Privacy Policy)