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Review of Diaspora by


by Greg Egan

I want to give this book five stars. I want to give this book one star. It’s amazing. It’s terrible.

Keeping Earth habitable is a pressing concern today. Even if we manage to avoid eco-catastrophe (and I’m optimistic on this), that’s only a small hurdle in the grand scheme of the cosmos. We only have about a billion years left before the Sun swells so much that it cooks the atmosphere. A few billion years after that, the Sun will engulf Earth itself—bye, bye, homeworld. Even if we manage to emigrate to the outer solar system or other solar systems entirely, we’re still just buying time until the end of the universe—whether it’s heat death or a Big Crunch or something else entirely. We can’t outrun eternity.

Of course, if we are around in a billion, let alone ten billion years, I somehow doubt we would recognize our future selves. Considering how much we differ from our hominin ancestors a million years ago, I suspect that evolution—natural or artificially-induced—will carry us away from this body plan. If we are going to migrate, we will adapt our forms—in body, or just in mind. Diaspora is a vision of a possible future, one in which humanity has diversified itself, speciated itself, and it attempting to find a way to survive.

Diaspora is a challenging novel, intentionally so. It is no-holds-barred, no-punches-pulled posthumanity. By the thirtieth century, humanity exists in three forms: flesh humans on Earth, embodied robots floating around the outer solar system, and polises of minds running as software on immense architectures. The main characters are exclusively minds from a polis. After an unanticipated, unexplained gamma-ray burst irradiates Earth, precipitating the extinction of flesh humanity, these minds resolve to explain the phenomenon and find a way of protecting humanity from it in the future. This triggers a strange and wonderful exploration of physical space and theoretical physics, and more mathematical exposition than you can shake a stick at.

The bulk of this book is a discussion of high-level mathematics and highly theoretical, even speculative, physics. Everything from high-energy wormholes to alternative universe topologies makes an appearance here. As a mathematician, and one who loves the abstract, axiomatic fields, I enjoyed most of this. It’s nice to step into someone else’s series of “what if” scenarios. When these are combined with the exploration of the physical universe and encounters with extraterrestrial life, it’s even cooler. The ideas that Egan explores here are intriguing enough to make me want to give Diaspora 5 stars—if it were a blog post, maybe.

Greg Egan bypasses the conventional structure of a novel, giving us instead mathematical musings in four acts. Technically Diaspora has everything a novel needs: characters, dialogue, even a plot. But with nature as the sole antagonist, the threats in this book are extremely distant. They are existential (though I hesitate to use that word when these characters are cloning themselves thousands of times over), but only in the most distant sense. This is literally a book about the end of the world as we don’t know it, and it’s almost as difficult for me to wrap my head around as the physics and mathematics are.

I think it would be tempting to seize upon the very abstract subject matter and level the charge that Diaspora is difficult because, with so many posthumans leaving flesh behind for a sixteen-dimensional universe, it loses something of what it means to be human. I understand why some people would feel this way, but I don’t think it’s the case at all. In spite of the very technical and dry dialogue between these characters, Egan makes it clear that their main concern—other than survival—is the preservation of humanity. There are, if not conflicts, then arguments between characters about the best path to take to remain human—the merits of flesh versus software, the perils of solipsism. Indeed, Diaspora is about the ultimate quest to remain human in spite of the universe itself stacking the deck against you.

I’m not going to give Diaspora five stars, because I think other authors have done this better while still delivering a very compelling story. I’m not going to give Diaspora one star, because it is an amazing collection of ideas and dialogues about humanity, progress, and physics. It’s like a really trippy blog post, just masquerading as a novel because novels, like bow ties, are cool. And like anything pretending to be something it’s not, Diaspora isn’t quite as satisfying as the conventional novel we’ve been trained to enjoy. It’s not bad, but different, and anything too different has to work a lot harder to earn acclaim. I’m willing to meet it halfway, so I’ll give it a solid three stars.

I majored in math and minored in English and philosophy; I’m teaching math and English to high school students come this fall. The intersectionality of this novel is kind of tailor-made for me—I suspect other people might have a hard time with it, and I want to be very upfront with this opinion lest my enthusiasm for the subject lead you astray. But if you are willing to make the effort and tolerate the paper-thin plot, then … wow. Yeah, in a way, totally worth it.


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