Egan: Orthogonal Series

Orthogonal, book #1

Generally I like my SF hard, even diamond hard. I don’t disdain fantasy; some of my favorite stories are fantastic. (As I’ve said often, Terry Pratchett’s Discworld series is my #1, my proverbial desert island companion.) But I definitely lean towards harder SF.

Growing up it was, of course, the Holy Trinity, Asimov, Clarke, Heinlein, but there was also Clement, Niven, and many others who stirred a large measure of science into their fiction. More recently the list of hard SF authors includes Forward, Steele, Stephenson, and a particular favorite of mine, Greg Egan.

I can safely say his Orthogonal series is as hard as science fiction gets.

I can equally safely say it may be too hard for many readers, even fans of SF. It might even be a bit hard for fans of Egan’s work — I’m an avid fan, but I found it a bit challenging. For one thing, it’s “hard SF” in the usual sense, very science-y, but the science itself isn’t easy.

In fact, to help readers make sense of the book, Egan offers a large amount of support material on his website. Getting everything from the book that Egan put into it requires some level of familiarity with that material.

I do have vaguely mixed feelings about niche stories, and Egan’s work tends to be niche in general, and extremely so in some cases. That niche being theoretical physics in all its foundational and mathematical glory. (Not surprising; Egan is a skilled mathematician.) The Yin-Yang tension here is that art should be as accessible to all as possible, but extreme niche art has strong appeal to those in the niche. Ultimately I think if an artist accepts the consequences of niche work (poor sales), there is good value for both creating and enjoying niche art.

Hell, this blog is pretty niche (my other blog even more so). Niche is fine, but it has caveats. And now I’m going to stop saying niche, because I’m starting to feel like a Knight of Niche (bring me a small exotic cactus).

§

The Orthogonal trilogy takes place in a radically different physical reality than ours, and its characters are non-human in the extreme. The three books take their civilization from the equivalent of a pre-Newton view of reality to a modern science on par with, or in some ways slightly better than, ours.

Egan details their advances in great,… um, detail. So much detail.

But it’s important because the physics of their world gives them a way to gain the time needed to figure out how to save their civilization from an imminent existential threat. Recently they’ve begun to observe what they name “Hurtlers” in their skies. They come to identify these as high-velocity objects from outside their system (outside their galaxy, as it turns out).

The Hurtlers have been few and small, but seem to be increasing in number and size. One strikes Gemma, one of the other planets in their system, and sets it on fire — it becomes a new sun. They realize that a large enough Hurtler could do the same to their world. It would be a decisive end to their species.

§

Orthogonal, book #2

Egan has designed an interesting species. They’re something like people-sized amoeba with male and female kinds. They have a basically bipedal shape, but can reform their bodies as needed. It’s a native ability, not due to any special self knowledge.

Their reproductive cycle is striking. Women are larger and stronger than men, and families begin with mated pairs. When they decide to have children, a reproductive act in which the man issues a binding promise to the woman causes her to first reabsorb her limbs, features, and brain; and to then fission into four children, two pairs of mated female-male “cos” — both of whom eventually reproduce.

The wife is lost in the process; the husband raises the kids. Men have all the child-raising feelings and innate abilities, whereas women, who are never closer than aunts, tend to be the leaders, teachers, and world-builders. That women are lost during child-bearing is seen as unfortunate but just the way life is. Much of the social tension comes from those who rail against the hand nature dealt — women who want to go on working; men who don’t want to lose their wives.

There’s an interesting naming convention, reminiscent of Latin names. For instance, the first character we meet is Yalda, a female “solo” — someone born without a co. That’s not common, but it happens. It’s perhaps analogous to, but the opposite of, identical twins for us. Normally Yalda would have a co named Yaldo. She does have a brother-sister co-pair, Lucia and Lucio.

In reproducing by fission, it would seem there is no chance for genetic mixing. But it turns out traits (and diseases) can be passed — with light. I’ll come back to that.

If Egan was more into social issues, this alone would be a great canvas for stories about gender, and Egan does explore it, but these are just the characters that populate his larger story about a universe with a major physics twist. For one thing, the speed of light depends on its frequency. More importantly, Special Relativity works backwards!

§

In our reality, the faster something moves, the slower its clock appears to run to observers. Those last two words are important; our local clocks always run at one second per second, but observers in motion relative to us may see our clock tick differently (slower).

The canonical example is the Twin Paradox in which one identical twin, say Roberta, takes a fast spaceship to a distant star and then returns to Roberto, her twin who stayed back on Earth. Their ages originally matched, but now Roberta is younger than Roberto. (See: the posts in the Time & Twins section of the Special Relativity series for details.)

In the Orthogonal reality, a fast-moving clock appears to tick faster, not slower. What’s more, speed can be infinite; it isn’t limited to light speed (which varies by frequency, anyway). It’s possible to go fast enough that your motion vector is orthogonal to your previous vector through spacetime. This effectively stops time “back home” — allowing a journey of any length without time passing for those left behind.

Spacetime diagram of the loop made by the Peerless. During the horizontal segments, no time passes on Homeworld. Time only passes there during the acceleration and deceleration curves.

At the turnaround point, deceleration and acceleration back along the flight path makes you not orthogonal with Homeworld, and so time does pass there. Once re-acceleration is complete time freezes back home until you return, decelerate, and re-enter the original vector (hopefully bearing gifts).

So the opposite of the Twin Paradox happens: the travelers age as much as needed (some 12 generations), but only four years pass back home. The trip gives the travelers time to figure out how to deal with the Hurtlers and return in time to save the species.

§

Orthogonal, book #3

They need to figure out more than the Hurtlers, though.

The generation ship they launch, the Peerless, uses a large fraction of its fuel accelerating to orthogonality with Homeworld. Most of the remaining fuel is allocated to running the ship for the unknown generations — there is none for slowing down, let alone returning.

The story wouldn’t be much fun if they failed, so it’s no spoiler to admit they don’t. Here it was never more true that “the journey is the reward.” (A big, very detailed, reward if you find strange physics rewarding.)

They do solve the fuel problem by finding a way to implement something mythical from their sagas: the Eternal Flame — a source of energy that doesn’t burn up.

Along the way they discover they need to address their population problem. A wife and her co become four children and a father. Two become five. The father dies of old age (“goes the way of men”) but each child-pair repeats the growth cycle. They explore a number of interesting paths; the ultimate solution is a game-changer.

The first book is called The Clockwork Rocket because this civilization doesn’t have electricity. They don’t even have metal. Their constructions are made from different kinds of rock. For example, clearstone is analogous to glass or clear plastics, and hardstone is analogous to metals. Their rocket, as did early airplanes, works entirely with mechanical linkages. (As their technology improves, they’ll discover photonics.)

They power their rocket — which is a mountain, by the way; their Everest, Mt. Peerless — with sunstone, a volatile form of rock that, when powdered and combined with “liberator” (which they get from plants), provides their power source. It can light lamps, heat, do work, or fuel rockets. If not carefully managed, it explodes.

So their mission is to figure out how to survive in the mountain (which is filled with tunnels and chambers huge and small) long enough to figure out the Hurtlers problem, figure out the fuel problem, and maybe figure out how to deal with going against time’s arrow on the way back.

Things get especially interesting when it turns out the Hurtlers, because of their unusual origin, act like antimatter. They’re even more dangerous to Homeworld than imagined. It isn’t just their high velocity that’s a killer.

§

To enable this reality, one thing Egan does is make a key change to the spacetime metric — the view-independent way we define length (space) and time. For us that metric is:

Note the minus sign for the time dimension. It’s this Minkowski space +++- signature that’s behind the effects of Special Relativity.

Egan’s Orthogonal reality has no minus:

Making spacetime Euclidean, not Minkowskian, turns out to have a number of unusual effects. The books are an exploration of the consequences of the ++++ spacetime metric signature.

A key consequence is that it’s possible to accelerate to infinite velocity in a finite time. In our reality, constant acceleration approaches light speed asymptotically. In the Orthogonal universe, there’s no asymptote, acceleration rotates your spacetime vector linearly, and that vector can tip all the way over to horizontal — to being orthogonal in time with your original vector.

Obviously this requires knowing about how light behaves, spacetime diagrams, Lorentz transforms, and how Minkowski space differs from Euclidean space. It’s hard for me to judge how readable, let alone enjoyable, the book is without at least some foundation physics. It’s definitely for us geeks.

§ §

As such, I can only recommend it provisionally. Huge thumbs up on the reality, aliens, and ideas, but be warned Egan leans hard into the deals. The books have a lot of diagrams. A good starting place is his essay, Plus, Minus: A Gentle Introduction to the Physics of Orthogonal. It’ll give you a good idea if you want to try the books.

That said, wow, the ideas are great and why I like Egan’s writing so much. (Likewise Neal Stephenson along almost exactly the same lines.) I’ve only touched on some of them. I haven’t mentioned how (or why) plants emit light, or why rock burns, or that light works both ways in time so messages from the future are possible.

I’ll also mention I found the third book less satisfying on several counts. I didn’t care for the characters, for one thing. (Each book deals with different generations along the trip.) The major problems have been solved by then, and much of the story is about politics in the mountain, fighting factions, and some truly weird physics (the future messages stuff).

Parts of the third book are very much like scenes in the movie Tenet — situations in which time is running both ways. I find the notion so incoherent it got in the way of my fulling enjoying the movie or those parts of book three. (In fact, I think both the movie and the book illustrate just how incoherent the notion is. Egan does go further than Tenet does in trying to account for it.)

But wow, what a cool universe and aliens!

§ §

As a hard SF aside, George O. Smith (1911–1981) wrote a series of short stories about communications engineers using vacuum tubes and other 1940s electronics to build and maintain a Solar system-wide radio network. Those were also super niche, but as an electronics hobbyist, it was my niche.

Of course, IN SPACE, vacuum tubes are just… tubes.

Question: Is science fiction rife with trilogies because it has a Holy Trinity?

Stay orthogonal, my friends! Go forth and spread beauty and light.

∇