Richard Southwell on Coxeter Groups

I only got as far as 2:42 and I am amazed! [Update: I listened to three hours and now it seems quite plausible!] The Coxeter Diagrams are an alien programming language that creates geometry. See also nLab on the Coxeter Group. 

This is also about the ADE phenomenon of Vladimir Arnold. See Norman Wildberger and Daniel Tubbenhauer on Formal and Structural Coincidents. 

You're expected to have watched this video first: 

Subscribe to Richard Southwell. 

Norman Wildberger on regular polytopes: 

On the ADE thing: 

Subscribe to Norman Wildberger. 

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