Schild’s Ladder

by Greg Egan

He gestured at the podium that was now growing before their eyes. His Mediator had explained that the timing was meant to encourage people to stop talking among themselves – like a change of lighting, or the raising of curtains – but apparently this was an aspect of the Rindler’s local culture that had been documented without ever being practiced.

He was gambling on a dizzying scale, like some dilettante ecologist in Earth’s colonial era, trying to balance one introduced predator against another.

“Can vendeks ever really be prey?” Tchicaya wondered. “They’re the smallest stable objects, so there’s no point seeking them out just to break them down into their constituent parts.” Mariama said, “There are no sub-units that you can extract from them and treat as nutrients – nothing analogous to vitamins or amino acids – so when you eat for the sake of eating, you’re infecting yourself. All food works like yogurt.

Given time, Tchicaya would have happily observed the Colonists from a distance until everything about them, right down to the subtlest cultural nuance, was absolutely clear. He and Mariama could have descended from the sky expecting compliments on their perfect local accents and unprecedented good manners, like a pair of conscientious travelers.

Quantum Graph Theory is fictitious, but the spin networks on which Sarumpaet’s work is based are part of a real theory, known as loop quantum gravity, discovered by Lee Smolin and Carlo Rovelli. There is a considerable literature on this subject; two comprehensive review papers are: “An Introduction to Spin Foam Models of BF Theory and Quantum Gravity” by John C. Baez, in Geometry and Quantum Physics, edited by Helmut Gausterer, Harald Grosse and Ludwig Pittner, Springer, Berlin, 2000. www.arXiv.org/abs/gr-qc/9905087 and “The Future of Spin Networks” by Lee Smolin, in The Geometric Universe, edited by S. A. Huggett et al., Oxford University Press, Oxford, 1998. www.arXiv.org/abs/gr-qc/9702030

I’m indebted to John Baez, who very kindly explained several points to me directly, as well as posting numerous articles on the news group sci.physics.research making these ideas more accessible to non-specialists. Of course, any errors I’ve committed in describing the real theory, and any absurdities in the way I’ve imagined its future, are my fault entirely.