Eratosthenes of Cyrene
c. 276 BCE–c. 194 BCE · Alexandria
Head of the Library of Alexandria; measured the circumference of the earth and founded scientific geography and chronology.
Did you know?
He measured the whole planet with a stick and a shadow
Around 240 BCE, Eratosthenes — the chief librarian of Alexandria — noticed that at noon on the summer solstice the sun shone straight down a well at Syene but cast a shadow at Alexandria. From the angle of that shadow and the known distance between the two cities, he calculated the circumference of the entire Earth, landing within a small margin of the true figure — more than seventeen centuries before anyone actually sailed around the globe.
How we know
Eratosthenes of Cyrene, c.276–194 BCE, chief librarian of Alexandria; his solstice-shadow measurement c.240 BCE yielded a circumference within roughly 1–16% of the true value depending on the stadion used. First circumnavigation: Magellan–Elcano 1519–1522 CE, about 1,760 years later.
Antiquity's two greatest scientists were pen pals
Archimedes, working in Syracuse, addressed one of his most remarkable treatises — The Method — as a letter directly to Eratosthenes, the polymath who ran the Library of Alexandria and had famously measured the size of the Earth. Its preface opens “Archimedes to Eratosthenes: Greetings,” and goes on to reveal his private technique for discovering theorems, sent across the Mediterranean to a fellow mathematician whose judgment he prized.
Meet Archimedes →How we know
Archimedes of Syracuse (c.287–212 BCE) and Eratosthenes of Cyrene (c.276–194 BCE) were contemporaries. Archimedes' treatise 'The Method of Mechanical Theorems' takes the form of a letter addressed to Eratosthenes, recovered from the Archimedes Palimpsest (identified by Heiberg in 1906).
Life journeyclick any stop, or use ←/→
AlexandriaEgypt
We know they were here, but the specifics of what they did at this stop aren’t recorded yet in our corpus.
About Alexandria
Alexandria (al-Iskandariyya) is the great Mediterranean port-city of northern Egypt, founded by Alexander the Great in 331 BCE and a leading centre of learning in antiquity. After the Muslim conquest of Egypt (642) it remained a major commercial and scholarly hub; the Shadhili Sufi Ibn Ata Allah al-Iskandari (d. 1309) took his nisba from the city, and the modernist reformer Muhammad Abduh (d. 1905) was active in Egypt's intellectual life there and in Cairo.
In Alexandria at the same time
Lycophron, Callimachus, Erasistratus of Ceos, Apollonius Rhodius, Aristophanes of Byzantium, Polybius
Across the traditions, in Alexandria at the same time
In the same place & time
Sages whose lives overlapped with Eratosthenes of Cyrene’s in the same cities, drawn from their recorded journeys.
In the same tradition
Lycophron, Callimachus, Erasistratus of Ceos, Apollonius Rhodius, Aristophanes of Byzantium, Polybius, Euclid
The world in their lifetime
Thinkers, teachers, and rulers whose lives overlapped with Eratosthenes of Cyrene’s — a glimpse of the wider world they lived in. Drawn purely from recorded birth and death years.
Graeco-Roman world
- Pyrrho· 360 BCE–270 BCE
- Epicurus· 341 BCE–270 BCE
- Crantor· 340 BCE–275 BCE
- Strato of Lampsacus· 335 BCE–269 BCE
- Zeno of Citium· 334 BCE–262 BCE
- Cleanthes· 330 BCE–230 BCE
- Hermarchus of Mytilene· 325 BCE–250 BCE
- Arcesilaus· 316 BCE–241 BCE
- Aratus Solensis· 315 BCE–240 BCE
- Aristarchus of Samos· 310 BCE–230 BCE
- Ariston of Chios· 300 BCE–240 BCE
- Theocritus· 300 BCE–260 BCE
- Archimedes· 287 BCE–212 BCE
- Chrysippus· 279 BCE–206 BCE
- Plautus· 254 BCE–184 BCE
- Apollonius of Perga· 240 BCE–190 BCE
- Diogenes Babylonius· 230 BCE–145 BCE
- Carneades· 214 BCE–129 BCE
- Antipater Tarsensis· 200 BCE–130 BCE
- Terence· 195 BCE–159 BCE
Jewish world
Rulers world
- Qin Shi Huang· 259 BCE–210 BCE
- Attalus I of Pergamon· 269 BCE–197 BCE
- Emperor Gaozu of Han (Liu Bang)· 256 BCE–195 BCE
- Hannibal Barca· 247 BCE–183 BCE
- Antiochus III the Great· 242 BCE–187 BCE
- Ashoka the Great· 304 BCE–232 BCE
- Antiochus IV Epiphanes· 215 BCE–164 BCE
- Emperor Wen of Han· 202 BCE–157 BCE
- Pyrrhus of Epirus· 319 BCE–272 BCE
- Mithridates I of Parthia· 195 BCE–132 BCE
- Bindusara· –273 BCE
Works
No works attributed in the corpus yet.