Four colors will do

     As I work with Gizem Karaali, an editor of the Journal of Humanistic Mathematics, to plan a reading of mathematical poetry at the JMM (Joint Mathematics Meetings) in Boston on 6 January 2012, my thoughts return to a poetry reading that I helped to organize at JMM in Baltimore in 1992. One of the participants was a friend and former colleague, Frank Bernhart, whose work is guided by the rhythm pattern of a well-known song.
     Bernhart is an expert on the Four-Color Theorem and his poem celebrates its history -- including consideration of its proof (in 1976) by Kenneth Appel and Wolfgang Haken. (The theorem asserts that any map drawn on a flat surface or on a sphere requires only 4 colors to ensure that no regions sharing a boundary segment have the same color.)

How much math does a math-poem need?

Poems offered in this blog vary in the levels of mathematics they contain.  One mathematical reader commented privately that in some of the poems the use of mathematical terms is "purely decorative."  Indeed, some people have particular expectations for poetry that relates to mathematics -- they want the content to use mathematical notation or to present a mathematical truth. Such as, perhaps, this abbreviated statement of the four-color theorem (formulated as a 4x4 square):