Older Than deck / Events and discoveries
First nuclear chain reaction
Achieved
1942
The first controlled, self-sustaining chain reaction, in a reactor built in Chicago.
Sources and checks
Checked 2026-11-01: Researched by Codex (two independent publishers, verbatim quotes); every counted quote re-found on its page by the server check (content-verify, or content-verify-pdf for PDFs); scope and plausibility reviewed by Claude (AI build agent). Quotes are short passages from each source; for dates the quote is the year as printed, read in context.
“on Dec. 2, 1942”University of Chicago News — Louise Lerner's original historical explainer: source, retrieved 2026-10-30; quote re-found by the server check
“The first self-sustaining nuclear fission chain reaction (1942)”US Department of Energy, Office of Nuclear Energy — original historical article: source, retrieved 2026-10-30; quote re-found by the server check
Spotted a mistake? Tell us; a correction gets a new revision.