Kevin R. Grazier, a Ph.D in geophysics and a huge fan of Halo, has contributed to a book called Halo Effect that looks at the Halo phenomenon; his piece, Halo Science 101, is about the science of the Halo universe. Halo Science 101 is up now at Gamasutra. Thanks for the heads-up to Roger Wilco, via Louis Wu at HBO.

Very interesting read, despite some of the absolutely ancient screenshots used for illustrations.