Skip to content
statementVerified

A measurement of Earth’s circumference is later reported under Eratosthenes’s name, principally by Cleomedes

The surviving public method is later: Cleomedes’s astronomical lectures, not an autograph On the Measurement of the Earth. In the causal graph this event strengthens Digital Learning Access, a driver that weakens Learning Poverty Rate (low- and middle-income countries) — an improving welfare path.

Sources: [1][2]

Read the full account

The surviving public method is later: Cleomedes’s astronomical lectures, not an autograph On the Measurement of the Earth.

Context

Strabo and Theon of Smyrna also carry numbers. The length of the stadion is disputed; this catalog does not supply a unique kilometre error bar. Parallel-ray geometry as later taught is a method path of high confidence on the later report, medium on the lost treatise’s wording.

Eratosthenes’s documented role is bounded by other offices and collaborators named in the sources below.

Conventional years are c.276–c.194 BCE. Almost no autograph survives. Cleomedes, Strabo, Nicomachus, and later encyclopedias are the public file. Classroom globe reconstructions are not his acts. Contribution is complex.

Why it matters

It is not a GPS series and not a permission to invent a 240 BCE field notebook.

Who was responsible

Contribution type and responsibility level for each recorded actor — not sole-author shorthand.

  • Eratosthenes

    Person

    Direct responsibility

    responsibility level 0.4 · verified

What changed

Fact → Driver → Indicator. Relationship strength orders the paths; it is not the observed indicator movement.

Evidence

The sources behind this fact and its verification state.

Verified2 sources on file
  1. 1.Britannica — EratosthenesEncyclopaedia Britannica · High credibility · verified
  2. 2.MacTutor — Eratosthenes of CyreneUniversity of St Andrews · High credibility · verified
What the sources establish

Britannica and MacTutor print that Eratosthenes measured Earth’s circumference from the difference of noon shadows at Syene and Alexandria, obtaining a figure in stadia.

Britannica’s biography and MacTutor independently describe the Syene–Alexandria method as later reported. Cleomedes is named in both as a principal later carrier.

Established: later Greek scientific prose attributes a stadia circumference to him. Not established: the autograph treatise, the exact stadion, or that a modern school experiment is his act.

Eratosthenes did not file a later UNESCO form, a later Loeb colophon, or a later museum label as a personal act. Keep Cleomedes’s date as the reporter, not as Eratosthenes’s death year.

Causal path

How this event connects to drivers and indicators in the graph.

  1. ActorEratosthenes
  2. contributed toFactA measurement of Earth’s circumference is later reported under Eratosthenes’s name, principally by Cleomedes
  3. strengthensDriverDigital Learning Access
  4. weakensIndicatorLearning Poverty Rate (low- and middle-income countries)

Cite this page

Factrail. (2026). A measurement of Earth’s circumference is later reported under Eratosthenes’s name, principally by Cleomedes. Factrail. https://factrail.ai/facts/era-circumference-cleomedes

https://factrail.ai/facts/era-circumference-cleomedes

Accessed 16 October 2026.

By the Factrail desk · Method: how we source and score · Last reviewed

Dispute this factNamed here, or represent someone who is? Request a right of reply.