Orthogonal (series)

Orthogonal is a science fiction trilogy by Australian author Greg Egan taking place in a universe where, rather than three dimensions of space and one of time, there are four fundamentally identical dimensions.

Technically, the space-time of the universe portrayed in the novels has a positive-definite Riemannian metric, rather than a pseudo-Riemannian metric, which is the kind that describes our own universe.

The first novel of the trilogy, The Clockwork Rocket, was published in 2011, the second, The Eternal Flame, in 2012, and the third, The Arrows of Time, in 2013.