There was an interesting the Boston Globe recently about Four Colors Suffice, a book by Robin Wilson on the history of the famous 4-color problem: How do you prove that you only need four colors to ensure that neighboring countries are colored differently. (More important: Why is Greenland pink?)

The proof (according to the article about the book that I didn’t read) was the first generated by a computer that couldn’t be checked by humans: in 1976, a Cray ground through every conceivable variation and found none that required more than four colors.

I have a question for the mathematically inclined (i.e., people unlike me): How many colors would you need for a 3-D map? Or, if you prefer, how many colors would you need to ensure that blocks (of any shape) stacked in any arbitrary way have differently colored neighbors? I am so bad at 3D stuff that you could tell me the answer is 2 and I would believe you, just so long as you looked at me with those doe-eyes of yours.

Categories: misc dw