Books by Egan, Greg

Egan, Greg. Dichronauts. New York: Night Shade Books, 2017. ISBN 978-1-59780-892-7.

One of the more fascinating sub-genres of science fiction is “world building”: creating the setting in which a story takes place by imagining an environment radically different from any in the human experience. This can run the gamut from life in the atmosphere of a gas giant planet (Saturn Rukh), on the surface of a neutron star (Dragon's Egg), or on an enormous alien-engineered wheel surrounding a star (Ringworld). When done well, the environment becomes an integral part of the tale, shaping the characters and driving the plot. Greg Egan is one of the most accomplished of world builders. His fiction includes numerous examples of alien environments, with the consequences worked out and woven into the story.

The present novel may be his most ambitious yet: a world in which the fundamental properties of spacetime are different from those in our universe. Unfortunately, for this reader, the execution was unequal to the ambition and the result disappointing. I'll explain this in more detail, but let's start with the basics.

We inhabit a spacetime which is well-approximated by Minkowski space. (In regions where gravity is strong, spacetime curvature must be taken into account, but this can be neglected in most circumstances including those in this novel.) Minkowski space is a flat four-dimensional space where each point is identified by three space and one time coordinate. It is thus spoken of as a 3+1 dimensional space. The space and time dimensions are not interchangeable: when computing the spacetime separation of two events, their distance or spacetime interval is given by the quantity −t²+x²+y²+z². Minkowski space is said to have a metric signature of (−,+,+,+), from the signs of the four coordinates in the distance (metric) equation.

Why does our universe have a dimensionality of 3+1? Nobody knows—string theorists who argue for a landscape of universes in an infinite multiverse speculate that the very dimensionality of a universe may be set randomly when the baby universe is created in its own big bang bubble. Max Tegmark has argued that universes with other dimensionalities would not permit the existence of observers such as us, so we shouldn't be surprised to find ourselves in one of the universes which is compatible with our own existence, nor should we rule out a multitude of other universes with different dimensionalities, all of which may be devoid of observers.

But need they necessarily be barren? The premise of this novel is, “not necessarily so”, and Egan has created a universe with a metric signature of (−,−,+,+), a 2+2 dimensional spacetime with two spacelike dimensions and two timelike dimensions. Note that “timelike” refers to the sign of the dimension in the distance equation, and the presence of two timelike dimensions is not equivalent to two time dimensions. There is still a single dimension of time, t, in which events occur in a linear order just as in our universe. The second timelike dimension, which we'll call u, behaves like a spatial dimension in that objects can move within it as they can along the other x and y spacelike dimensions, but its contribution in the distance equation is negative: −t²−u²+x²+y². This results in a seriously weird, if not bizarre world.

From this point on, just about everything I'm going to say can be considered a spoiler if your intention is to read the book from front to back and not consult the extensive background information on the author's Web site. Conversely, I shall give away nothing regarding the plot or ending which is not disclosed in the background information or the technical afterword of the novel. I do not consider this material as spoilers; in fact, I believe that many readers who do not first understand the universe in which the story is set are likely to abandon the book as simply incomprehensible. Some of the masters of world building science fiction introduce the reader to the world as an ongoing puzzle as the story unfolds but, for whatever reason, Egan did not choose to do that here, or else he did so sufficiently poorly that this reader didn't even notice the attempt. I think the publisher made a serious mistake in not alerting the reader to the existence of the technical afterword, the reading of which I consider a barely sufficient prerequisite for understanding the setting in which the novel takes place.

In the Dichronauts universe, there is a “world” around which a smaller ”star” orbits (or maybe the other way around; it's just a coordinate transformation). The geometry of the spacetime dominates everything. While in our universe we're free to move in any of the three spatial dimensions, in this spacetime motion in the x and y dimensions is as for us, but if you're facing in the positive x dimension—let's call it east—you cannot rotate outside the wedge from northeast to southeast, and as you rotate the distance equation causes a stretching to occur, like the distortions in relativistic motion in special relativity. It is no more possible to turn all the way to the northeast than it is to attain the speed of light in our universe. If you were born east-facing, the only way you can see to the west is to bend over and look between your legs. The beings who inhabit this world seem to be born randomly east- or west-facing.

Light only propagates within the cone defined by the spacelike dimensions. Any light source has a “dark cone” defined by a 45° angle around the timelike u dimension. In this region, vision does not work, so beings are blind to their sides. The creatures who inhabit the world are symbionts of bipeds who call themselves “walkers” and slug-like creatures, “siders”, who live inside their skulls and receive their nutrients from the walker's bloodstream. Siders are equipped with “pingers”, which use echolocation like terrestrial bats to sense within the dark cone. While light cannot propagate there, physical objects can move in that direction, including the density waves which carry sound. Walkers and siders are linked at the brain level and can directly perceive each other's views of the world and communicate without speaking aloud. Both symbiotes are independently conscious, bonded at a young age, and can, like married couples, have acrimonious disputes. While walkers cannot turn outside the 90° cone, they can move in the timelike north-south direction by “sidling”, relying upon their siders to detect obstacles within their cone of blindness.

Due to details of the structure of their world, the walker/sider society, which seems to be at a pre-industrial level (perhaps due to the fact that many machines would not work in the weird geometry they inhabit), is forced to permanently migrate to stay within the habitable zone between latitudes which are seared by the rays of the star and those too cold for agriculture. For many generations, the town of Baharabad has migrated along a river, but now the river appears to be drying up, creating a crisis. Seth (walker) and Theo (sider), are surveyors, charged with charting the course of their community's migration. Now they are faced with the challenge of finding a new river to follow, one which has not already been claimed by another community. On an expedition to the limits of the habitable zone, they encounter what seems to be the edge of the world. Is it truly the edge, and if not what lies beyond? They join a small group of explorers who probe regions of their world never before seen, and discover clues to the origin of their species.

This didn't work for me. If you read all of the background information first (which, if you're going to dig into this novel, I strongly encourage you to do), you'll appreciate the effort the author went to in order to create a mathematically consistent universe with two timelike dimensions, and to work out the implications of this for a world within it and the beings who live there. But there is a tremendous amount of arm waving behind the curtain which, if you peek, subverts the plausibility of everything. For example, the walker/sider creatures are described as having what seems to be a relatively normal metabolism: they eat fruit, grow crops, breathe, eat, and drink, urinate and defecate, and otherwise behave as biological organisms. But biology as we know it, and all of these biological functions, requires the complex stereochemistry of the organic molecules upon which organisms are built. If the motion of molecules were constrained to a cone, and their shape stretched with rotation, the operation of enzymes and other biochemistry wouldn't work. And yet that doesn't seem to be a problem for these beings.

Finally, the story simply stops in the middle, with the great adventure and resolution of the central crisis unresolved. There will probably be a sequel. I shall not read it.

August 2017 

Egan, Greg. Schild's Ladder. New York: Night Shade Books, [2002, 2004, 2013] 2015. ISBN 978-1-59780-544-5.

Greg Egan is one of the most eminent contemporary authors in the genre of “hard” science fiction. By “hard”, one means not that it is necessarily difficult to read, but that the author has taken care to either follow the laws of known science or, if the story involves alternative laws (for example, a faster than light drive, anti-gravity, or time travel) to define those laws and then remain completely consistent with them. This needn't involve tedious lectures—masters of science fiction, like Greg Egan, “show, don't tell”—but the reader should be able to figure out the rules and the characters be constrained by them as the story unfolds. Egan is also a skilled practitioner of “world building” which takes hard science fiction to the next level by constructing entire worlds or universes in which an alternative set of conditions are worked out in a logical and consistent way.

Whenever a new large particle collider is proposed, fear-mongers prattle on about the risk of its unleashing some new physical phenomenon which might destroy the Earth or, for those who think big, the universe by, for example, causing it to collapse into a black hole or causing the quantum vacuum to tunnel to a lower energy state where the laws of physics are incompatible with the existence of condensed matter and life. This is, of course, completely absurd. We have observed cosmic rays, for example the Oh-My-God particle detected by an instrument in Utah in 1991, with energies more than twenty million times greater than those produced by the Large Hadron Collider, the most powerful particle accelerator in existence today. These natural cosmic rays strike the Earth, the Moon, the Sun, and everything else in the universe all the time and have been doing so for billions of years and, if you look around, you'll see that the universe is still here. If a high energy particle was going to destroy it, it would have been gone long ago.

No, if somebody's going to destroy the universe, I'd worry about some quiet lab in the physics building where somebody is exploring very low temperatures, trying to beat the record which stands at, depending upon how you define it, between 0.006 degrees Kelvin (for a large block of metal) and 100 picokelvin (for nuclear spins). These temperatures, and the physical conditions they may create, are deeply unnatural and, unless there are similar laboratories and apparatus created by alien scientists on other worlds, colder than have ever existed anywhere in our universe ever since the Big Bang.

The cosmic microwave background radiation pervades the universe, and has an energy at the present epoch which corresponds to a temperature of about 2.73 degrees Kelvin. Every natural object in the universe is bathed in this radiation so, even in the absence of other energy sources such as starlight, anything colder than that will heated by the background radiation until it reaches that temperature and comes into equilibrium. (There are a few natural processes in the universe which can temporarily create lower temperatures, but nothing below 1° K has ever been observed.) The temperature of the universe has been falling ever since the Big Bang, so no lower temperature has ever existed in the past. The only way to create a lower temperature is to expend energy in what amounts to a super-refrigerator that heats up something else in return for artificially cooling its contents. In doing so, it creates a region like none other in the known natural universe.

Whenever you explore some physical circumstance which is completely new, you never know what you're going to find, and researchers have been surprised many times in the past. Prior to 1911, nobody imagined that it was possible for an electrical current to flow with no resistance at all, and yet in early experiments with liquid helium, the phenomenon of superconductivity was discovered. In 1937, it was discovered that liquid helium could flow with zero viscosity: superfluidity. What might be discovered at temperatures a tiny fraction of those where these phenomena became manifest? Answering that question is why researchers strive to approach ever closer to the (unattainable) absolute zero. Might one of those phenomena destroy the universe? Could be: you'll never know until you try.

This is the premise of this book, which is hard science fiction but also difficult. For twenty thousand years the field of fundamental physics has found nothing new beyond the unification of quantum mechanics and general relativity called “Sarumpaet's rules” or Quantum Graph Theory (QGT). The theory explained the fabric of space and time and all of the particles and forces within it as coarse-grained manifestations of transformations of a graph at the Planck scale. Researchers at Mimosa Station, 370 light years from Earth, have built an experimental apparatus, the Quietener, to explore conditions which have never existed before in the universe and test Sarumpaet's Rules at the limits. Perhaps the currently-observed laws of physics were simply a random choice made by the universe an unimaginably short time after the Big Bang and frozen into place by decoherence due to interactions with the environment, analogous to the quantum Zeno effect. The Quietener attempts to null out every possible external influence, even gravitational waves by carefully positioned local cancelling sources, in the hope of reproducing the conditions in which the early universe made its random choice and to create, for a fleeting instant, just trillionths of a second, a region of space with entirely different laws of physics. Sarumpaet's Rules guaranteed that this so-called novo-vacuum would quickly collapse, as it would have a higher energy and decay into the vacuum we inhabit.

Oops.

Six hundred and five years after the unfortunate event at Mimosa, the Mimosa novo-vacuum, not just stable but expanding at half the speed of light, has swallowed more than two thousand inhabited star systems, and is inexorably expanding through the galaxy, transforming everything in its path to—nobody knows. The boundary emits only an unstructured “borderlight” which provides no clue as to what lies within. Because the interstellar society has long ago developed the ability to create backups of individuals, run them as computer emulations, transmit them at light speed from star to star, and re-instantiate them in new bodies for fuddy-duddies demanding corporeal existence, loss of life has been minimal, but one understands how an inexorably growing sphere devouring everything in its path might be disturbing. The Rindler is a research ship racing just ahead of the advancing novo-vacuum front, providing close-up access to it for investigators trying to figure out what it conceals.

Humans (who, with their divergently-evolved descendants, biological and digitally emulated, are the only intelligent species discovered so far in the galaxy) have divided, as they remain wont to do, into two factions: Preservationists, who view the novo-vacuum as an existential threat to the universe and seek ways to stop its expansion and, ideally, recover the space it has occupied; and Yielders, who believe the novo-vacuum to be a phenomenon so unique and potentially important that destroying it before understanding its nature and what is on the other side of the horizon would be unthinkable. Also, being (post-)human, the factions are willing to resort to violence to have their way.

This leads to an adventure spanning time and space, and eventually a mission into a region where the universe is making it up as it goes along. This is one of the most breathtakingly ambitious attempts at world (indeed, universe) building ever attempted in science fiction. But for this reader, it didn't work. First of all, when all of the principal characters have backups stored in safe locations and can reset, like a character in a video game with an infinite number of lives cheat, whenever anything bad happens, it's difficult to create dramatic tension. Humans have transcended biological substrates, yet those still choosing them remain fascinated with curious things about bumping their adaptive uglies. When we finally go and explore the unknown, it's mediated through several levels of sensors, translation, interpretation, and abstraction, so what is described comes across as something like a hundred pages of the acid trip scene at the end of 2001.

In the distance, glistening partitions, reminiscent of the algal membranes that formed the cages in some aquatic zoos, swayed back and forth gently, as if in time to mysterious currents. Behind each barrier the sea changed color abruptly, the green giving way to other bright hues, like a fastidiously segregated display of bioluminescent plankton.

Oh, wow.

And then, it stops. I don't mean ends, as that would imply that everything that's been thrown up in the air is somehow resolved. There is an attempt to close the circle with the start of the story, but a whole universe of questions are left unanswered. The human perspective is inadequate to describe a place where Planck length objects interact in Planck time intervals and the laws of physics are made up on the fly. Ultimately, the story failed for me since it never engaged me with the characters—I didn't care what happened to them. I'm a fan of hard science fiction, but this was just too adamantine to be interesting.

The title, Schild's Ladder, is taken from a method in differential geometry which is used to approximate the parallel transport of a vector along a curve.

July 2019