The time has finally come.

I have finally finished Greg Egan’s Orthogonal trilogy.

There really ought to be a fanfare for such an announcement.

The other books: Clockwork Rocket and Eternal Flame. Spoilers for these two naturally follow.

At the start of his one, Egan himself has written that you just won’t really get this book without the previous two. I don’t think I’ve ever come across the third book in a trilogy that said that so bluntly, and I really appreciate it. Because it is SO true: if you don’t understand how light and time work in this universe (and look, I don’t understand it, but I get how it’s different from ours), let alone the society and what the folks are doing on this mountain-turned-spaceship, you will be so lost you’ll end up in Antarctica instead of Bali.

As the second book was a few generations after the third, so here. The ship is sailing happily through the universe, and folks are still working on how to save the homeworld. Not that everyone especially wants to save the homeworld, from which they are now several generations distant – and will never see themselves anyway. So, classic generation ship angst, really. That’s one issue. Then, there’s what turns out to be a logical consequence of the bizarre universe Egan has set up where light travels at different speeds and some parts are orthogonal to others: that time is affected, too. Specifically, that it should be possible to set a receiver for messages from the future.

Because that couldn’t possibly turn out badly.

So now there are two issues dividing the crew of the Peerless. And just to add to the problems, while the earlier issue about children has been solved – the females no longer need to either die to become their children, or starve to prevent that from happening, and they’re not overpopulating – there are some people who aren’t happy with the solution: especially some brothers who don’t want to be compelled to care for their sister’s children. So life is definitely not rainbows (which they’ve never seen) and roses (which they don’t grow).

I love that Egan tackles such weighty topics as democracy, needs of the few vs needs of the many, the importance of choice, the place of parenthood, and so on – all in a book that literally has vector diagrams in it as it explores the outcomes of a thought experiment in physics.

From a narrative point of view, the most gripping part is when four people travel to an orthogonal world to see whether it would be habitable. Again, this is an exploration of the consequences of ‘orthogonality’; time is literally going in the opposite for this world from how it is experienced by the travellers, so what could that possibly look like? What does that, what can that, mean for free will? (A whole bunch of headaches is the answer. Mostly metaphorically.) This bit is also a deeper exploration of the characters, as they interact only with each other, in very trying circumstances.

As with the other two books, I admit that I skimmed bits of the physics explanations. Including the diagrams. I read it well enough to get the point Egan is making, but I would in no way attempt to explain it.

I have a couple of thoughts that are spoilers, so don’t read the rest if that’s a problem… but if you’ve read the first two, I think you definitely need to see how the story plays out.

Firstly, I think the ‘innovation block’ is deeply fascinating and troubling as a result of the future messaging. And utterly believable, too. The whole question around free will then becomes a deeply fascinating and troubling one, too… because of course they fulfil the expectation of there being no breakthroughs, as they’ve been told, specifically by doing nothing. Having the dust already be present in the spaceship is weirder, I admit, but it’s all a good way to twist your brain in knots.

Secondly, I think I am unhappy with the ultimate resolution of the having-children conundrum. It neatly solves the what-if-I don’t-want-children issue, and removes the mothering/fathering split, suggesting that everyone is equally capable of parenting. And I am definitely not one to suggest that the gender binary must be maintained… which now that I think about it, in this species is entirely centred on the relationship to children. Which gives me further pause for thought. But… I still think I’m uncomfortable.