Schildās Ladder
Itās been a while since Iāve read a Greg Egan book. I often love the ideas he explores, particularly in Diaspora. But I sometimes find his stories difficult to get through. That was definitely true of a previous book I read, Incandescence, which takes place in the setting of an interesting interstellar civilization. But the story seems to slide into a thinly veiled tutorial on general relativity.
I had heard that Schildās Ladder was one of his more accessible works, but held off reading it until now. Iām glad I did. A decade ago a substantial portion would have been unintelligible. Today I know enough about quantum mechanics to follow many of the discussions and tactics used in the book. But Iām not sure the average reader would find this book that accessible. It doesnāt get into the math (although there are a few diagrams), but it helps to have a conceptual understanding of how superposition, decoherence, entanglement, and similar concepts work.
The setting is twenty thousand years in the future in a posthuman interstellar civilization. People can backup their minds and transfer to new bodies, and are generally immortal. This is hard sci-fi so no faster than light travel. In most cases traveling interstellar distances, typically by transmission, means separation from friends and loved ones for decades or centuries.
In some cases when someone travels, their entire home planet population will go into āslowdownā until they return in order to avoid having them become too out of sync. Slowdown is a protocol that itās possible to cheat on and exist in real time while everyone else is moving and thinking at a miniscule fraction of the normal pace.
There are also a group of humans known as anachronauts, who left Earth thousands of years earlier, before mind copying had become viable. They travel in sleeper ships, occasionally stopping at a world to check in on how humanity is developing. As the name implies, theyāre largely throwbacks, and have difficulty accepting many of the changes that have taken place.
One of those changes is that sexual dimorphism no longer exists among humans. The āheā and āsheā pronouns only continue as linguistic conventions relative to types of names. Sex requires peopleās bodies to react against each otherās pheromones and gradually become compatible, maximizing the chances that itās monogamous and consensual. Egan doesnāt describe his characters in physical terms, which likely downplays just how strange we would find them. (This conception of sexuality also reminds me of Ursula Le Guinās Gethens in The Left Hand of Darkness.)
Peopleās minds operate on qusps, quantum āsingletonā processors, which ensure that any decision is worked out in an isolated quantum superposition and then promoted prior to interaction with the environment, so that a person only ever makes one decision. In other words, they donāt branch (many-worlds style) into multiple versions based on their decisions. (Although itās accepted that they can and do branch due to other quantum outcomes.) So the premise assumes wave function realism, which becomes important at various points in the story.
Quantum mechanics and general relativity have been reconciled into a framework known as the Sarumpaet rules, presented as a descendent of loop quantum gravity theory. The rules are thousands of years old and heavily tested and validated. At the beginning of the story, itās hard for the characters to take seriously the idea they could be wrong. But it becomes clear they are when an experiment goes horribly wrong, leading to the accidental creation of a ānovo-vacuumā that begins expanding out at half the speed of light, consuming everything it comes in contact with.
As the centuries pass, the novo-vacuum consumes hundreds of star systems necessitating large scale evacuations and migrations. A space station, named the Rindler, is built just outside the boundary of the novo-vacuum with its speed matched to the expansion rate, and deploying scientific instruments to probe the āfar side,ā a nickname for the novo-vacuum, as opposed to the ānear sideā for regular space.
Initially built by scientists wanting to study and understand the far side, the Rindlerās population has swelled as additional people have arrived to participate in the studies. But a couple of camps have formed: the Preservationists, who want to stop the novo-vacuum and destroy it to preserve as many of the existing planets as possible, and the Yielders, who want to stop the far sideās growth but then study it. Relations between the two sides have become bitter.
Tchicaya, the protagonist, is a Yielder who has just arrived on the Rindler. His childhood friend, Mariama, arrives shortly after him. He has not seen her in centuries. She is a Preservationist. Which is ironic because as children, she was the more adventurous one while Tchicaya the one most inclined to preserve the existing status-quo.
This book has a moderate amount of conflict in it, even some violent conflict, something often missing in Eganās stories. Although as in his other posthuman books, the society envisioned is pretty utopian. The violence comes from the anachronauts, who are from outside the utopia. And the story eventually converges on a typical story frame for Egan, two people together on an odyssey of discovery.
I donāt think Iām spoiling much by noting the final portions of the story explore the changed physics inside the far side. This is a long standing fascination for Egan. He loves exploring alien physics, something that, based on the descriptions of many of his more recent books, has only increased over the years.
I enjoyed this book, but Iām not sure I would have enjoyed it as much without being familiar with the science. Eganās work is pretty much the hardest of hard sci-fi, which means quantum physics is central to the plot. Often in sci-fi the story can be enjoyed by people who arenāt necessarily into the scientific speculation. Iād say thatās less true here. There is some character drama, but relatively limited. If the idea of characters working on an intractable problem in a quantum superposition so that some version of them finds the right answer sounds like your jam, then itās probably worth checking out.
Have you read it? If so, any ideas from it that particularly resonated with you?
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