This is book three, and the conclusion, of the Orthogonal series.

Having become invested in the storyline of Egan's Eternal Flame (read: fission reactor), I, of course needed to finish the series. No, no, not of course, but in this case, worth finishing.

We still have some of the physics going on, so realizing Egan had written up the physics of his world in more depth and posted it on his website was a delightful discovery.

This book continues another three or so generations past the previous generations book, with women being able to survive childbirth instead of splitting into their children, dying in the process. Which is great, yay, women are on more equal footing, though the society does have the echos of "better when" and "oh, shit, how do we integrate our progressive thinking with the antiquated beliefs of the homeworld when we return?"

In this book, time travel is possible, with people being able to send messages back to their own selves. Information can't just create itself, however, and the mountain becomes stagnant, with the utter domination of the council and its control of information backward in time.

Just the sort of thing rebels would work to destroy, lest the world stagnate. Which it does. Of course.

I liked this book more than the first one, less than the second one, with the conclusion being realistically improbable and fictionally necessary. I ended up enjoying this series and recommend it to anyone who likes science in their science fiction.

This is book two of the Orthogonal series.

Okay, this book continues the Orthogonal series, following the Clockwork Rocket. The premise of the last book was that the world the heroine, Yalda, lived in was threatened by emmient destruction by hurtling stars invading their solar system, so they launched a mountain top to relativistic speeds so that time will slow for the occupants of the mountain and they will have time for intellectual pursuits. The expectation is that the people in said mountain will advance beyond the linear years of the homeworld, and return with technology needed to save it.

Great. With you there. This book continues where we are three generations into the flight. While Egan delightfully continues with the exploration of advancements in physics, mirroring much of our discovery of physics in the twentieth century, Egan also explores some of the cultural issues an isolated society with restricted resources might encounter.

And there is where I become emotionally invested in the book.

The characters of the book are shapeshifting amoeba-like sentient beings whose natural form is six limbs and four eyes. They give birth by the mother splitting into four parts, two girls and two boys, one of each of which are bonded into pairs that continue the cycle.