“Dichronauts” by Greg Egan

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Rating: 4/5 Stars

Another interesting Hard SF read by Egan. It’s not as mind-bending or physics-bending as his “Orthogonal” series but contains intriguing ideas and characters. In contrast to his previous books where the characters slowly learn (and educate the reader about) the physics of their environment, here they are already well versed in the strange (to us) geometry of their universe and its consequences.

In this book, Egan posits a world that has two space dimensions and two time-like dimensions. The resulting geometry is a hyperboloid world orbited by a sun that is slowly wandering south. The inhabitants of various cities are thus forced to migrate to remain in the habitable zone of their world.

The story starts with two characters, a ‘walker’ named Seth, who can only face eastwards or westwards, and his parasitic companion Theo, who lives in his head and apparently uses echo location to see what is north or south. In the course of the story, they become surveyors who survey the landscape that their city would migrate to.

On a particularly long survey journey, they encounter a city which, to them, has committed a species wide crime. But that is small compared to what they ultimately encounter; the apparent edge of their world, whose depths they would have to survey to discover whether it can be bypassed when their city eventually encounters the edge.

In this adventure into the depths, their knowledge of the geometry of their world would be tested as they encounter strange new lifeforms and then perform some personal sacrifices to be able to return to their city with knowledge that will be vital to their survival.

As usual, Greg Egan provides a supplementary website that explains the geometry of the world. While not strictly necessary, I found it to be very helpful in understanding the challenges the characters have in living in this kind of universe and how things work.

Yet another interesting book by Egan for those who are more interested in strange world-building.

Book read from 2017/04/05 to 2017/05/29