I think many people end up skimming the physics bits (there’s a lot of stuff where two scientists talk to each other about their experiments) but I can see why they are in there; I can see the importance to establishing how the protagonists are able to learn about their world. In some sorts of modern SF, you have 'clever' characters that suddenly come up with a world-changing plot-advancing idea out of nowhere, which is something that take me out of the story entirely; In the Orthogonal Trilogy, every discovery they make is the result of careful experimentation, thought and debate, just like the scientists do in real life when they’re jot busy copy each other’s work. But don’t mind the Physics. There's still a great. Leitmotiv: that the protagonists bootstrap space technology and launch a generation ship into space, with the express idea of giving the generation ship an infinite amount of time for its inhabitants to make scientific advances, and then come back and save the home-world (where only a few years will have passed) is a very epic concept to base a story around; you have bravery, separation, forming of a new society, the strange life of the many generations working to save ancestors they'll never see. I found the characters very relatable and each book built to a very satisfying climax that is character and emotion driven as much as science driven. The end of the second book in particular was very powerful, and was largely about relationships (feminism) and society (to put it vaguely) rather than physics. This very hard, hard SF Trilogy is perhaps the ultimate in hard SF world-building: starting by simply changing a minus sign to a plus sign in the Minkovsky equation that governs the geometry of spacetime, Egan then derived, from first principles, how light, matter, energy, motion, gravity and time would work in this Universe (MWI at play here). While the space-time in our universe has a Lorentzian geometry, space-time in the orthogonal universe is Riemannian. Listing all that gets changed because of this tiny physical variance: (1) different wavelengths of light travelling at different speeds; (2) faster-than-light travel being possible via conventional acceleration; (3) interstellar voyages taking longer for the travellers than the people that stayed at home; (4) Matter being structured differently, and hence biology is also very different. This Trilogy is a story, told in 3 volumes (“The Clockwork Rocket”, “The Eternal Flame”, and “The Arrows of Time”), about the inhabitants of that Everettian universe struggling to save themselves from a grave threat by scientific study of their world and cosmos. But it’s not only about that; it also touches on themes of gender politics, governance, philosophy and free will. There is a lot of physics, and I mean a lot! Egan once said that "much of what I write is coming from the position that mathematics and the natural sciences are intrinsically interesting, and are as suitable as the central concerns of fiction as anything else". But many readers have found that there's also a lot going on besides the physics. A theory is a model and not the reality. But a better theory predicts more accurate numbers in a wider area. You should ask yourself, whether cockroaches, ships or Portuguese are real. They are not. They are just parts of the model your mind successfully uses to manage the challenges of daily life: avoid suffering, gain joy. I believe that quantum information is real, and the world you experience is just the result of how your mind experiences changes of the information state. We know nothing. Knowing is only a very strong belief. How valid is it to ask what exactly comprises the link between the subjective observer and the real universe? Is it in any way meaningful to assume the universe will continue to exist without me in it? And how would you know that it did unless you existed?

Egan, once again, mindboggling. ( )