To some extent this is a companion volume to Egan's Orthogonal trilogy. In those books, he imagined what it would be like to live in a universe in which the time dimension behaved geometrically in exactly the same way as the three spatial dimensions, rather than with the hyperbolic coordinate relationship (described by special relativity) that we see in our own universe. In this book, Egan describes a universe in which one of the spatial dimensions has time-like properties - introducing the hyperbolic relationships of relativity into everyday spatial coordinates. (The title, Dichronauts, meaning "travellers in two times" is a reference to the fact that his story universe has two time-like dimensions (time and "axial") and two regular spatial dimensions.
So we have a world in which simply trying to rotate an object can change its apparent shape; where it's impossible to rotate a north-facing object to face east, or an east-facing object to face north; where the stable shape for a planet is the hyperboloid depicted on the cover; where light can't travel to the north or south; and where falling over in those directions can have lethal consequences.
As with Orthogonal, Egan's aliens have one utterly alien property (in this case, we have two intelligent species that exist as commensals, one threaded through the skull of the other), but otherwise behave and speak like clever and amiable humans. And that's fine, because Egan's imagined world is strange enough without him expecting us to accommodate to an alien society, too. I'm therefore reminded of Hal Clement at his best, though Egan's characters have more humour.
The story is a quest, in which the reader finds out more about the world along with the story's characters. There are some surprises, and one toe-curling moment I certainly didn't see coming.
I knock off a star only because I think Egan's world may simply be too strange for many readers. In Orthogonal, one could amble along accepting that there was something a little odd about time without fretting about the details. In this story, almost every event is influenced by the strange spatial geometry, and if you don't find the geometry of special relativity engaging, you may be left floundering. Egan provides some explanatory detail in the Afterword (which could productively be read first, since it contains no significant spoilers), and much more information on his website.
- Format: Kindle Edition
- File Size: 3576 KB
- Print Length: 312 pages
- Simultaneous Device Usage: Unlimited
- Publisher: Greg Egan (31 March 2017)
- Sold by: Amazon Australia Services, Inc.
- Language: English
- ASIN: B01MV3SUNB
- Text-to-Speech: Enabled
- Word Wise: Enabled
- Customer Reviews: 28 customer ratings
- Amazon Bestsellers Rank: #239,417 Paid in Kindle Store (See Top 100 Paid in Kindle Store)