"The Clockwork Rocket" by Greg Egan is the first in his Orthogonal trilogy. As usual the author is very committed with the writing and goes the extra mile (or miles in this case) in order to achieve credibility. The story develops in an completely different universe from ours, unlike what could be argued of other Eganian literature. The events during the first part of the book lead the main character "Yalda" to become a Physicist at a renowned University in a city far away from her family. The mathematical content of the book is vast, sometimes aided by diagrams (which most of them happen to be drawn over the characters' bodies).

In a nutshell Yalda turns out to be the equivalent of Einstein in her home world (universe). By studying the Hurtlers' phenomenon (some sort of comets which appeared when she was little) she establishes (by accident) the principles of Special Relativity based on her studies of light and the mathematics that describe it, calling it Rotational Physics. This revolutionizes the scientific knowledge of her time (as expected), but also sheds light on the enormous threat the Hurtlers represent to her planet (and everything else actually), prompting the scientific community and the society to engage in the biggest project ever to get a chance of survival. A space opera on board the Peerless (a mountain turned into a spaceship) looking for the answers needed to prevent the impending catastrophe is in order.

Yalda's discovery is the geometry of her universe, a closed Riemannian manifold, where, contrary to what happens in our pseudo-Riemannian situation, the metric has signature (++++). Thus the fundamental laws of physics we are familiar with become dramatically modified. Egan has put a lot of effort in this book (more than any of his previous work) and the extra material in his website proves that. More than 80,000 words in topics such as Geometry, Hamiltonian Mechanics, Wave Equations, Abstract Algebra, Electrodynamics, General Relativity and more. But what really impressed me was the way he (alone?) carried out the calculations for the speculative Physics to be consistent with his premise. In the process he obtains many interesting results worth of looking at (I would even recommend writing a paper). After going trough the mathematical details of his extra material (at least the speculative part for this book) I have yet to find any mistakes or misinterpretations (writing erroneously Klein-Gordan instead of Klein-Gordon is understandable recalling that it can be confused with the Gordan in the Clebsch-Gordan coefficients).

At a personal level I really enjoyed the book and I'm looking forward to read the sequel, but I'm afraid this may not be a memorable lecture for everyone. Not only because the reader will necessarily need some understanding of the underlying mathematics and physics to follow the major turning points, but also due to storytelling some notions have names which can be confusing (e.g. rotational physics involves space-time diagrams NOT classical mechanics), even doing the effort to clearly imagine Yalda's race's physiology is important as I found out after neglecting it for a couple chapters then seeing I couldn't keep reading cause my simplistic model didn't work anymore. Looks like a symmetry exercise where, based on his own commitment, the author demands a lot of commitment from the reader too. It's possible many people won't appreciate that and just go to next book in queue.