Book Review: “Dichronauts” by Greg Egan

Dichronauts by Greg Egan

The cover has the tag line, “Welcome to the strangest world in Science Fiction’, and that’s not far wrong.   Reading SF all my life, I have encountered a lot of mind stretching universes, in many different directions.

Egan has two prominent predilections: space time geometry, and fluid personal identities.

This story is an old-fashioned “big idea” SF. In this case, he works out a parallel universe with a fundamental geometry different from our own. We live in a physics that has 3 space-like dimensions plus 1 time-like dimension. This alternative universe has 2+2.

This geometry has lots of implications for movement, perception, and celestial mechanics, among other things. You know it’s tricky when the author has a whole tutorial web site.

Egan has decided to create a sort of “Flatland” for this hyperboloid geometry. He imagines a whole world with hyperbolic geomety, and an intelligent race who lives there. Biology seems mostly conventional, though Egan never gets into just how molecular biology might work in this geometry, and the people are pretty human. One of Egan’s perennial topics is how we’re all humans, across a very, very broad range of variations.

To show off the properties of this alternative space-time system, the protagonists choose to become professional surveyors, in which capacity they directly deal with the shape of the world.   They also are scouts and explorers, so interesting travels ensue.

I have to say that I wasn’t especially interested in the characters or their society. It’s all pretty shallow (one dimensional?), and, frankly, boring. The expeditions are interesting, though mostly as a kind of geometry lesson. Much of the time, the characters have to think and talk about things that would be obvious to them, but we don’t understand, such as the way their vision works. (Hint: it’s complicated, at least by our own standards.) This endless stream of tutorial asides doesn’t help the story flow.

The worst thing about the book is that I don’t understand the underlying geometry at all. Yes, I’ve seen these curves in calculus class. No, I don’t know how gravity would work. Or how light cones would work. Or any of that stuff. And, not to put too fine a point on it, I still have no idea what these animals look like, or how they move.

I had to go to his web site, in search of clues. I didn’t find them there.

I can’t overemphasize the magnitude of this problem. We follow a mostly first person story of Seth/Theo, but I don’t have any picture of what they look like, how they move, how they see, etc.

The best part of the story has to be the planet, and the amazing geography. I won’t give away any of the wonders discovered by the trekkers.

At the same time, the ecology of this planet is not explained and makes little sense. There are human –like sapients, but it’s mostly a lifeless desert. Where are all the other animals, where are the plants, where are the microbes, fungi, insects, and all the rest?   As I pointed out, I have to wonder what sort of analog to DNA might exist in such a space-dime geometry. How would protein folding work? How would chemical reactions of any kind work with two time-like dimensions?  How would blood or other flluids flow?  I have no idea.

This book has a kernel of an interesting idea, but my own view is that there isn’t enough story here for more than a few pages.

  1. Greg Egan, Dichronauts, New York, Nightshade Books, 2017.


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