''Schild's Ladder'' is a (very) hard ScienceFiction novel by Creator/GregEgan. Possibly his hardest ever, filled with non-trivial mathematics and physics.

Physics researchers at a lab in remote space accidentally unleash a runaway reaction that threatens to eat the universe. As the threat grows (at half the speed of light), various factions disagree on how to deal with it.
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!! This novel contains examples of:
* [[ApocalypseHow/ClassX4 Apocalypse How: Class X-4]]: the runaway reaction itself.
* ContinuityNod: Everyone, even embodied people, runs on Qusps rather than brains; this is never explained, and you have to read the short story "[[http://www.gregegan.net/MISC/SINGLETON/Singleton.html Singleton]]" to get why this matters. And when Tchicaya wakes up, he muses that the process of constructing a brain must create unrememberable experiences; this was explored in the short story "Transition Dreams".
* DeusExMachina: The anachronauts, who show up in the novel's climax to [[spoiler: blow up the research ship]]. They are only mentioned twice before, never shown to have any specific agenda, and their actions have no lasting consequences beyond isolating the two main characters to continue exploration on their own.
* EternalLove: Before Tchicaya finally gets to have sex with his childhood lover Mariama he contemplates "Nothing could have lived up to four thousand years of waiting. Except perhaps an original theorem."
* FirstContactMath: The protagonists realize that there's intelligent life inside a pseudovacuum when they notice that a series of pulses coming from it represent consecutive prime numbers.
* ForScience: The freak lab accident that gives birth to a [[EarthShatteringKaboom ''galaxy''-shattering kaboom]] occurs because the scientist wanted to test an obscure physics theory. Nobody seems terribly annoyed that someone's physics experiment effectively ''blew up the universe'', which is justified in that Egan manages to eventually make it [[spoiler: a good thing]].
* LightspeedLeapfrog: Played straight. The slower travelers are known by most of spacefaring humanity as "anachronauts". It's an interesting variant, though: By the time the story begins, most anachronauts ''choose'' to continue traveling at relativistic speeds instead of using FTL, so that they can "hop" forward through time and observe the development of civilization. It's PlayedForLaughs when ''entire planetary civilizations'' coordinate elaborate pranks on the intrepid time travelers, leading them to think the development of the human race is even more bizarre than it actually is - which is saying something.
* MinovskyPhysics: The work pretty much runs on this trope, as it is based around the fictitious but believable (apparently it was based on loop quantum gravity) "quantum graph theory" and the "Sarumpaet rules" that govern all fundamental interactions. It's been described as the "hardest science-fiction ever" with good reason.
* NoBiologicalSex: Features essentially genderless posthumans but retains both male and female pronouns. When embodied people couple up, their bodies grow custom genitals over a period of six months that will only work with each other--it's considered quite romantic.
* SphereOfDestruction: The novo-vacuum, the expanding and destructive sphere of altered spacetime that is the focus of the story.
* StarfishAliens: [[spoiler: the apparent life inside the "eaten" region, which ranges from non-sentient fauna to sentient beings with their own civilization and technology, exists at the ''Planck scale''. (Mind-bogglingly tiny, for those of you not familiar with the term--by analogy, quantum graph edges are to electrons as electrons are to 100 km or so.)]]
* TheSingularity: Everyone runs on computers; some people are embodied (their processors located inside their heads), and some aren't. Nobody's actually died (apart from very rare suicides) in millennia. But one of the central ideas of Singularity thinking is ''averted''; it turns out that strong superintelligence is impossible. Sort of like all Turing-complete machines have the same power; they're just sometimes faster.
-->It was a rigorous result in information theory that once you could learn in a sufficiently flexible manner--something humanity had achieved in the Bronze Age--the only limits you faced were speed and storage; any other structural changes were just a matter of style.
* {{Twinmaker}}: People make backup copies of themselves with remarkable regularity, but generally only run one at a time. When someone dies a "local death" (which is pretty difficult, given that everyone runs on Qusps), they restore from the latest backup. People seem to fork themselves only rarely. Transport over great distances is accomplished by transmitting the contents of your mind and having it downloaded into a new body (or just run on local hardware).
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