Recent posts tagged Sagan Dodecahedron

mention an association between that Platonic

solid and the 5×5 grid. That grid, when extended

by the six points on a "line at infinity," yields

the 31 points of the finite projective plane of

order five.

For details of how the dodecahedron serves as

a model of this projective plane (PG(2,5)), see

Polster's *A Geometrical Picture Book *, p. 120:

For associations of the grid with magic rather than

with Plato, see a search for 5×5 in this journal.