I'm trying to find a hard sci-fi story where one of the major premises was that the world has a Riemannian geometry (x^2+y^2+z^2 + t^2) instead of the real world's Minkowski geometry (x^2+y^2+z^2 - t^2). The effects of this on relativity and how it affected the world were very significant. Here's some of the effects that I remember:
- Stars, instead of looking like points of white light, looked like lines that were cross-sections of a rainbow
- It was impossible for two objects to collide with certain velocities unless a third object was also present
- It was possible to "turn around" your direction through time, just as it's possible to turn around the direction you're moving through space in the real world
I remember seeing this online several years ago, along with an out-of-character analysis of the setting that explained all of the above effects in detail. Does anyone know what this is and/or where I found it?