Add Orthogonal

[Richard Littauer]

@mihailim have you read this? Can you add it?

[Mihai Limbășan]

I haven't read it, sorry :) While I like Egan's work very much (hard SF fan here, and he's the epitome of hard SF writers), I couldn't find the time to properly start this yet. It's not an easy read, you (quite literally, sometimes) have to work at it; having a good understanding of physics, geometry and calculus not only helps immensely, it's close to being a prerequisite. Even more so than for Schild's Ladder.