In Greg Egan's inventive new novel Schild's Ladder, the diverse range of characters utilise a number of different languages and communication techniques, but manage to find a common ground of meaning through the use of Mediator programs. For the scientific layperson (like myself) trying to comprehend the depths of physics and quantum theory which drive Schild's Ladder, a Mediator program would be most welcome. At times, this hard SF is just a little too hard as the narrative is intersected with lengthy, heavily detailed descriptions of theoretical physics that are beyond my capacity to comprehend. On the other hand, the epic struggle that unfolds encompassing the fate of not one but two unique universes, combined with a vibrancy of characterisation, more than compensate for the sporadic opacity of scientific jargon.
In the opening section, the scientist Cass travels to the Mimosan's station in order to use their unique equipment to momentarily create a `novo-vacuum', a microscopic universe with a completely new set of physics. The novo-vacuum is only expected to exist for a fraction of a second, but in that time Cass hopes that what is discovered about the alternative universe will enrich the understanding of her own. Of course, the experiment goes horribly wrong and the physics of the novo-vacuum turn out to be more stable than those of the outside world, with the result that the alternative universe begins expanding, engulfing the old, wiping out all in its path.
Six hundred years later former lovers Tichicaya and Mariama both find themselves onboard the Rindler, the foremost research centre focused on the novo-vacuum. Significantly, the Rindler is also a spacecraft maintaining the velocity which keeps the ship the closest possible distance from the expanding boundary of the mysterious, new universe. Despite their past together, Mariama and Tichicaya find themselves on opposite sides of the philosophical rift that divides the ship's occupants. Mariama is in the Preservationist camp, desperate to destroy the novo-vacuum and stop the destruction of the planets in its wake. At the other extreme, Tichicaya's group have been labelled Yielders, those who believe the novo-vacuum is the greatest scientific discovery of all time and that is should be studied, understood and if possible adapted to rather than eradicating it. As the experiments on board the Rindler reach a point where the novo-vacuum's exterior might finally be breached, the philosophic divide becomes a material battle for the fate of both universes.
To readers of Egan's past novels, much of Schild's Ladder will seem distantly familiar. Although Egan never writes sequels, his stories reveal an almost evolutionary development of ideas and theories. As with his novel Diaspora, for example, there is a dichotomy between those characters who choose to remain embodied and those who exist as acorporeals, living only as informatic patterns in virtual worlds. However, unlike Diaspora, even the embodied make their choice at a philosophic level; every individual's identity is stored on a Qusp-Quantum Singularity Processor-and the choice to be embodied or otherwise is the choice as to whether the Qusp exists as part of a digital network or embedded in a flesh body. Similarly, the idea of opposing worlds (or universes) clashing against each other has appeared in Egan's short stories and in Permutation City. In Permutation City, however, the conflict was on an ontological level when the Lambertians developed an Autoverse ontology without the need for a creator and somehow this act started to unravel their progenitors' digital world. In Schild's Ladder, the struggle is far more scientifically based detailing the collision of two unique physical universes, but the development of ideas from Permutation City are apparent.
The most significant development in Egan's recent work, though, is his vastly improved characterisation beginning with Teranesia and continuing in Schild's Ladder. The plight of Tichicaya and Mariama in human terms-their love, their motivation, and their similarities even when philosophically opposed-is what drove Schild's Ladder for me. If the scientific theories are as credible and intriguing as the human story in Schild's Ladder, then this book will be impossible to put down for a scientifically literate reader. For me, I learnt a little about science, glimpsed an intriguing future, and revelled in the complications of an all too human story.