Eratosthenes measured the Earth's circumference using shadows and geometry.

the verdict

SUPPORTED

the evidence backs this

Recorded sources

2 sources for · 0 against

Counts group repeated records of the same source within each side. They do not measure evidence strength or source independence.

Historical and scholarly evidence confirms that Eratosthenes successfully calculated the Earth's circumference by analyzing the angles of shadows cast by sundials in different locations.

The analysis

The claim is a well-documented historical fact supported by retrieved papers 1 and 2, which detail Eratosthenes' use of shadow observations and geometry to measure the Earth.

Evidence for · 2

The Circumference

Recorded source metadata

Christopher A. Matthew. The Circumference. 2023. https://doi.org/10.1093/oso/9780198874294.003.0006

This chapter details how Eratosthenes used sundial shadows and geometric ratios to calculate the Earth's circumference with high accuracy.

Source citation format

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More for · 1

Eratosthenes and the Measurement of the Earth's Circumference (c.230 BC)

Recorded source metadata

Christopher A. Matthew. Eratosthenes and the Measurement of the Earth's Circumference (c.230 BC). 2023. https://doi.org/10.1093/oso/9780198874294.001.0001

This work discusses Eratosthenes' third-century BC calculation of the Earth's circumference based on shadows cast by sundials in Alexandria and Syene.

Source citation format

The paper trail · every fact has a biography

first checked01 Aug 2026

judged → SUPPORTED · 7501 Aug 2026

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