Arsenic, Atomic Number 33 — introduced 815
Arsenic, Atomic Number 33 arrived in 815, during the Medieval (9th century). It expanded what people could build, measure, or communicate, and quickly reshaped daily life.
Context
Medieval — Kingdoms rise, faith spreads, castles and codices. That's around 1155 years ago — deep history, roughly 12 centuries in the past. Around the same time, the world was also seeing Sambisari, Hindu (Indonesia) (812) and Chand Baori [India] (800).
Why it matters
Arsenic, Atomic Number 33 mattered because it changed what was possible. New tools shift habits, industries, and even how people see the world — and this one is remembered for exactly that reason.
Did you know?
Just 3 years before, Sambisari, Hindu (Indonesia) (812) was also making headlines — a reminder how much history can compress into a single decade.
Era
Medieval
Kingdoms rise, faith spreads, castles and codices.
Category
Inventions
Inventions are the tools and technologies that changed what humans could do — from wheels and printing presses to satellites and smartphones.
Contemporary events
What else was happening in the world around this time.
Sources & further reading7 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.
Wikipedia
Community-maintained encyclopedia entry with citations.
Encyclopædia Britannica
Editorially reviewed reference articles.
Library of Congress
Primary sources, photographs, and archival records.
National Archives
Original U.S. government documents and records.
Smithsonian
Museum collections and curator-written explainers.
BBC History
Long-form explainers and documentaries.
History.com
Timelines and topic overviews from HISTORY.
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 815?
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published example
3 yrs before · 812
Sambisari, Hindu (Indonesia)
15 yrs before · 800
Chand Baori [India]