Schild's ladder Book

I first started this one four years ago and put it on hold after a while; I was not prepared for such a work. However, every now and then I thought about it and I finally said to myself: its time had come. Now that I read it, I wonder why I have postponed it for so long… This is one of the best hard sci-fi books out there.

While I don't pretend I fully understood it*, I found it beyond fascinating: the amazing worldbuilding, the huge scope, the mind-blowing concepts, everything I look for in sci-fi it's here.

Premise: while testing the new Quantum Graph Theory (the far future term for Grand Unified Theory) something goes wrong and the novovaccum, instead of disappearing the moment it was created, is stable and growing, something nobody expected. The event would have been a great accomplishment; however this new universe is advancing at half the speed of light, swallowing everything in its path. People discovered that Sarumpaet's laws** are not universal.

More than 600 years later, thousands of inhabited systems have been destroyed and refugees are seeking for safer systems, out of reach from the advancing novovaccum border.

Since this event, people divided themselves in two factions: the Yielders, who are trying to study it and find a way to penetrate this novovaccum in order to search and preserve the alien forms of life inside it (for they are certain they exist) and the Preservationists, who want to destroy it and protect the planetary systems and life as they know it.

Ultimately, a team formed between a Yielder (Tchicaya) and a Preservationist (Mariama) managed to find a way inside it and if they (and we) get a most extraordinary journey, which is mind-bending.

The honeycomb stretched on relentlessly; the Sarumpaet gained and lost ground. After eight hours of nominal ship time, they'd crossed a thousand cells. In near-side terms, they were a millimeter beneath the point where the border had last rested, and the chase had gone on for mere picoseconds. The Planck worms had spent more than two hours diversifying before they'd learned to penetrate these catacombs, but having found the basic trick they appeared to be unstoppable. So much for the strategy of burning away one vendek population and the predators trapped within it; that would have been like trying to cure a victim of bubonic plague by sterilizing a single pustule.
Tchicaya said, "If this goes on for a hundred kilometers, I'm going to lose my mind."

This quest is not only in an almost incomprehensible for us universe at Planck scale; it is also a journey within oneself:

"That's it," Tchicaya marveled. "We've done it." A lattice of diagonals ran along the path, marking the way, carrying the arrow forward. No compass, no stars to steer by, but they'd found a way to copy the arrow faithfully from start to finish. "It's beautiful, isn't it?" his father said. "This is called Schild's ladder. All throughout geometry, all throughout physics, the same idea shows up in a thousand different guises. How do you carry something from here to there, and keep it the same? You move it step by step, keeping it parallel in the only way that makes sense. You climb Schild's ladder."[…]
"There's one more thing you should see," his father said. He drew a second path on the globe, joining the same two points but following a different route. "Try it again."[…]
"I've made a mistake," he said. He erased the second ladder, and repeated the construction. Again, the second copy of the arrow at the end of the path failed to match the first. "I don't understand," Tchicaya complained. "What am I doing wrong?" "Nothing," his father assured him. "This is what you should expect. There's always a way to carry the arrow forward, but it depends on the path you take."

The worldbuilding is simply outstanding. Try imagining a fully functional universe at quantum level, with human avatars transformed in software and a ship as 'big' as a Planck unit. I think no other writer can take concepts like these and transform them into a story so mesmerizing and full of mouth-dropping ideas. This is an homage to the grace and elegance of math and physics.

"If some alien civilization had handed us Quantum Graph Theory on a stone tablet'out of the blue, in the eighteenth or nineteenth century'I might not feel the same way about it. But general relativity and quantum mechanics were among the most beautiful things the ancients created, and they're still the best practical approximations we have for most of the universe. QGT is their union."

There are many more other concepts regarding future human's biology, time, physics and these two universes but I think it's worth to discover them for yourself. From my PoV this is a unique piece of hard sci-fi and a must read for all genre lovers.

It is simply stunning.

* I spent half a day on Egan' site to read more about it and it helped:

** for more details on Sarumpaet's and graph theory, check this: