One of my readers pointed out an error in my recent post about the 4-color theorem. I wrote an update that reframes the theorem in terms of graph theory and talks about some corollaries of the theorem.
A diagram I created that illustrates part of an argument about the 4-color theorem.
My reasoning was that we could take a region of a map that required four colors and then surround it by a country that touches all the countries of the region. The surrounding country couldn’t be colored with any of the four colors we had already used, so we’d have to add an extra color. Logical enough, no? The only problem is that it’s wrong.
Read the full post at Roots of Unity.
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