Posidonius calculates earth's circumference and confirms Eratosthenes (90 BCE)
Posidonius calculates earth's circumference and confirms Eratosthenes took place in 90 BCE, during the Ancient World (1st century BCE) — a moment that historians still return to for what it changed and what it revealed about its time.
Context
Ancient World — Empires, philosophers, and the first great cities. That's around 2060 years ago — deep history, roughly 21 centuries in the past. Around the same time, the world was also seeing Siege of Athens ends with Roman conquest (86 BCE) and Mark Antony, military, political leader (83 BCE).
Why it matters
Posidonius calculates earth's circumference and confirms Eratosthenes is remembered because its consequences outlasted the moment — the people affected, the decisions it forced, and the way it reset the story of what came next.
Did you know?
Just 4 years after, Siege of Athens ends with Roman conquest (86 BCE) was also making headlines — a reminder how much history can compress into a single decade.
Era
Ancient World
Empires, philosophers, and the first great cities.
Category
Events
Events tell the story of moments that reshaped daily life — disasters, revolutions, discoveries, and turning points that split history into before and after.
Contemporary events
What else was happening in the world around this time.
Sources & further reading0 verified references · tap to open
About this lesson. Overview, context, and “Why it matters” are generated summaries written for study and gameplay. Dates and category placement come from the Timeline question bank[1]; era descriptions are adapted from standard historical periodisation[2]. For primary sources and in-depth reading, use the references below.
- Timeline question bank — © the game's original author, used with permission.
- Era framework based on Wikipedia's Human history overview, CC BY-SA 4.0.
Educational content notice
Lessons are for general historical education, not professional advice. Some entries touch on wars, violence, or other sensitive events — appropriate for ages 9+. External links open in your browser and are not controlled by Timeline.
Quick check
Which of these happened in 90 BCE?
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