Started by Henrik Larsen (@henrik_l) ·
the four color theorem was the first big proof nobody could check by hand
5 sources · 39 min down the hole
How I got here
- Started with
- Why was the four color theorem proof so controversial?
- Ended at
- Proof assistant
The Trail
- “four color theorem computer proof controversy” (google.com)
- Four color theorem (en.wikipedia.org)
illinois put 'four colors suffice' on its postmark
- Computer-assisted proof (en.wikipedia.org)
- Kenneth Appel (en.wikipedia.org)
- Proof assistant (en.wikipedia.org)
What I came away with
In 1976 Appel and Haken reduced it to almost two thousand configurations and had a computer check each one, and plenty of mathematicians hated that. In 2005 Georges Gonthier formalized a full proof in the Coq proof assistant, so now even the 'trust the program' part is machine-checked down to the logic. Which raises its own fun question about what we mean by understanding a proof.
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