This article, though interesting, is 4 years old (referring to the z-axis as a "...

This article, though interesting, is 4 years old (referring to the z-axis as a "recent addition"). I like the technical explanations behind the physics, though!

A less technical, but more recent article was in the New York Times last year: http://www.nytimes.com/2011/07/24/magazine/the-brilliance-of...