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3.55  ·  Rating details ·  490 ratings  ·  90 reviews
Seth is a surveyor, along with his friend Theo, a leech-like creature running through his skull who tells Seth what lies to his left and right. Theo, in turn, relies on Seth for mobility, and for ordinary vision looking forwards and backwards. Like everyone else in their world, they are symbionts, depending on each other to survive.

In the universe containing Seth's world,
Published July 4th 2017 by Night Shade Books
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Manuel Antão
Mar 18, 2018 rated it really liked it  ·  review of another edition
Shelves: 2018
If you're into stuff like this, you can read the full review.

Eigen-stuff Applied to Buridan's Ass: Dichronauts by Greg Egan

When I read an Egan's book I cannot tackle it on a purely literary level. Egan's fiction makes me think about things I didn't know I wanted to think about. This is another one of those novels with a mind-boggling universe.
Egan's world has far consequences:

The space won't be isotropic any more. Thus, things would behave differently if you rotate them around the zz-axis and
This was one tough book to comprehend. I read all I could find on Greg Egan site and some more about differential geometry and I still did not understand how the world imagined by the author works.

Because this is not an action or character driven story, but one in which geometry makes the rules and the reader tries to visualize how this world is constructed. Instead of a 3-dimensional space and 1 dimension of time, we have 2 of each.

After playing with this simulation here, I could imagine a bit
Nov 04, 2018 rated it liked it
For fans of multiple world-time-lines and especially for fans of Christopher Priest's The Inverted World, welcome to Dichronoauts.

Walking one way brings you to the future, the other, to the past. But space is still space and time is still time. Thanks to the little creature attached to the people here, we've got a cultural/exploratory thing going on that is the spiritual godchild of Priest's classic novel. Just look at the cover to get an idea. That's a picture of the Earth. As in, the Earth,
Nov 18, 2018 rated it really liked it  ·  review of another edition
Symbionts on a planet with a different set of dimensions and shaped as an hyperboloid.

A somewhat human body and a leech-like creature, cohabiting and sharing their life. How do you decide the direction of your life, how do you choose your profession, your partners.... who gives in, who takes precedence, what happens in case of irreconcilable differences? Fascinating.

The book is split in several parts, each part of the book dealing with a distinct section of plot. Part One did a nice job of
Apr 11, 2017 rated it liked it
finally finished this one and after a great beginning which was very intriguing and another maybe 100 pages that kept me really interested, the book became sort of a slog as the difficulty of reconciling the strangeness of the Dichronauts universe and beings with a sort of human-like behavior started showing more and more and the book became "it sounded a cool idea at the time but it cannot sustain itself beyond an initial introduction" as on the world building side things got stranger and ...more
Nov 09, 2020 rated it liked it
Dichronautss back cover has the perfect blurb: Impressively bizarre Egan may have out-Eganed himself with this one. Yeah, pretty much. Dichronauts gives us a world in which water flowing uphill is not even its most bizarre feature. Nor that the world is an infinite hyperboloid. Nor that light cannot travel in certain directions. Nope. For me, the most bizarre feature of Dichronauts world is that its denizens cannot safely rotate.

Its all so bizarre, in fact, that if you want to become a
Tim Hicks
Sep 29, 2017 rated it liked it
Shelves: science-fiction
If this is your first Greg Egan, just put it down slowly and back away quietly. No one needs to get hurt here. Go find an earlier work as an introduction.

This is hard SF to make Hannu Rajaniemi blush. This is hard SF made of adamantium, or impossibilium. I'm guessing there aren't 200 people in the world who could read this and smile and say, oh, yes, haha, of COURSE it would be like that, wouldn't it?" and maybe ten who could say "ahem, a little error there on page 212 with the rotational
May 11, 2017 rated it liked it
The world of Greg Egans Dichronauts contains two spatial dimensions and two temporal ones. The people of this world are symbiotes, each comprised of a walker and a sider siders are parasites who leech nourishment from their walkers; walkers can only see one side of the world on their own and need their siders to see the other.
The sun revolves around the earth in this world, so its people are constantly migrating to stay within its habitable zones. The walker Seth and his sider, Theo, are
Jan 26, 2018 rated it really liked it  ·  review of another edition
Shelves: science-fiction
I read Greg Egans new hard-sf novel Dichronauts in kindle format. I have previously read and liked a half dozen of his novels, and so I was well prepared that this would be a challenging read.

Dichronauts physics -
Dichronauts world -

The setting is the outstanding feature in this work, and it is described as a world in a universe with 2 dimensions of space and 2 dimensions of time, rather than the 3 and 1 of our
Sep 30, 2017 rated it it was amazing
This is another one of Egan's marvelous alternative universes with different physical laws from our own. It's an adventure story following some young denizens of a nomadic civilization. Through the course of their adventure the reader slowly (and with a lot of hard work!) comes to understand the bizarre world they inhabit.

(view spoiler)
David Swanson
Fascinating but a bit too clever

As with most novels by Egan, I'm very glad I took the time to read it, and equally as glad that I never have to read it again.

Egan has a knack for introducing us to genuinely alien worlds and viewpoints, and this novel is no different. Introducing exactly how things differ from our viewpoint is possibly a spoiler, but suffice to say that the afterword explains things extremely clearly... if you can grasp the mathematics.

The downside to all this is that the
Jul 25, 2017 rated it liked it
This review was originally published at Book Learning.

Who knew geometry could be so confusing?

According to the biography on the inside cover, Greg Egan is a computer programmer. For those who are familiar with his work, if not his biography, that wont come as a great surprise. Egan writes hard sci-fi, the sort of hard sci-fi that doesnt take any prisoners and doesnt bother to go slowly to let stragglers keep up. There is a certain clockwork logic to all his books that makes them feel almost
Quinn Dougherty
Oct 27, 2019 rated it really liked it
very impressive! i thought it would've been nice as two books-- in one, a story about the physics of an infinite hyperboloid planet (and the edge cases where that model breaks down), and in another, a story about humanoids who rely on slug-oid parasites for more than half of their sensory input. But, for the sheer joy of being able to tell you this book exists, I'm ultimately glad both stories were fused into one.

it's not even that weird, he makes it relatable i swear.

Of course i could spend
Pavel Lishin
Jul 19, 2017 rated it really liked it
Gonna have to brush up on my Dichronaut cosmology, and re-read this one, I think. I'm still pretty unclear how Walkers' hands and fingers work.

There's some interesting parallels here with Peter Watts' Blindsight: The Gang's accusation of what 20th century psychiatry was up to, and Thanton.
Simona Vesela
Oct 20, 2020 rated it it was amazing
I have tried to read this 3 times. Twice I have stopped after 3 pages utterly confused. Few weeks ago I read his science notes on it, started my third attempt and was hooked. (I would tip my nonexistent hat to anyone who read it without studying those notes first).

This book imagines a world of index (2,2). I know a little about differential geometry and the combination of (2,2) and DI-chronauts scared me. Really. A lot. The author really wants to create consciousness and beings in a universe
Sep 03, 2017 rated it really liked it
Shelves: sf
The book was definitely an interesting read, from the point of "actual hard science fiction" instead of "a mix of romance and humans fighting each other in an unusual setting". If you are into the first type (which not necessarily means completely disdaining the second :D), and willing to invest some mental efforts into imagining the world based on different geometry rules than our own due to having two space-like and two time-like coordinates, and therefore different constraints and ...more
S.J. Higbee
Jul 11, 2017 rated it it was amazing
In order to be better able to visualise this world, my firm advice is to visit Greg Egans site at the link:
where you can discover how he came up with this intriguing creation and the inhabitants. Alongside all the maths, the world is also more fully explained before you plunge into this one. Inevitably, I discovered the site after I had completed the book and although I had picked up the gist of what was going on, it would have been helpful to have
Aug 19, 2017 rated it it was ok
Greg Egan might be my favorite sci-fi author (top-5 for sure), but this is both his worst book to date and a bad book overall. It is built around some completely novel physical geometry and universe dimensionality, poorly explained in the book (to have any hope of understanding, you'll need a guide on Egan's website), but that's fine. The problem is that is really the only positive part of the book; the rest is a stupid/weird morality story about different groups and coexistence (4000/800 had a ...more
Dec 29, 2019 rated it really liked it
Shelves: scifi, fiction
I really enjoyed this book, but your experience will be made much better by taking the time to read through the supplementary materials about the physics of this world, because it is very hard to understand from just reading the novel. This book is basically an intense, modern incarnation of the genre pioneered by Hal Clement's Mission of Gravity , and the tradition that (to a lesser extent) Larry Niven continued in books like Ringworld and The Integral Trees . An exploration travelogue set ...more
May 30, 2019 rated it it was amazing
This is mind-strainingly weird sci-fi. No one I have described it to will read it, but I loved almost every minute: it's one of the few books I'd like to reread. The e-book I bought has notes at the end (which I didn't realize until I got there), but I was baffled by the physics of the mundane tasks described in the first chapter. The notes on Egan's website are very helpful and cleared up all the confusion. I think one gets more out of it if they've done the math themselves and internalized the ...more
Shhhhh Ahhhhh
Dec 17, 2018 rated it it was amazing
I have mixed feelings about this book. It's a striking, novel concept. Describing the physics of a novel universe where tipping over means stretching out into infinity and dissolution, is necessarily novel. Wrapping my mind around the story happening in that strange space was a new and interesting sensation while reading. It definitely raised the difficulty level for me. Nevertheless, I found the basic, and archetypal, story to be fairly entertaining. In fact, the elements of their world, while ...more
Stacey Kondla
Aug 01, 2017 rated it liked it
Shelves: 2017
I found this to be a challenging read and quite different from the Greg Egan books I have read previously. The math and geometry in this was a bit beyond me, but it was still an entertaining story with an interesting sociological story thread. I wouldn't recommend this as a starter to Greg Egan, but I'm glad I read it and will be interested to read whatever he comes out with next. Without a doubt this was the strangest world with a very strange society and strange life forms.
Apr 15, 2019 rated it really liked it  ·  review of another edition
Wow!! I don't think I will ever fully understand how the physics of these characters and their world works but I found this book to be very readable. It would be hard to recommend to people who are not into Science/Speculative fiction to a fair degree but if people are willing to take a leap into the unknown this is an interesting and mind bending world to experience.
My first Greg Egan read and I will be exploring more of his work.
Julie Thomas
Sep 10, 2020 rated it it was amazing
Shelves: favorites
Wow, now those are some weird aliens!
Baal Of
Dec 04, 2017 rated it liked it  ·  review of another edition
Shelves: canned-soup
Like all of Egan's work, this novel is based on some mind-twisting speculative premises, in this case what would it be like to be in a world with 2 spacial and 2 time dimensions. I found it absolutely necessary to read the supplemental materials on his web site to help with comprehension. From that perspective, this book is good, however the story itself was unfortunately boring, and the characters seemed too human despite the fact they were symbiotic pairs, one of which lived in a hole in the ...more
Apr 22, 2017 rated it liked it
This really should have been a comic or videogame, or anything with more of a visual component to it. I hadn't even realized it was possible to get myself this mixed up in regard to cardinal directions.
Kam Yung Soh
May 03, 2017 rated it really liked it
Shelves: sf-and-fantasy
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
Ariana Mcgee
Jan 10, 2018 rated it it was ok
I found this book at B&N and purchased it because of the interesting world. I didn't think I would be so disappointed by it. If you like very technical science fiction this book is for you. The author has many sites explaining his view if you would still like to try it. Greg Egan really could have fleshed out his ideas more. I had a very hard time imagining a 2x2 dimensional world. I think the problem was that he was more concerned about the world he created than the intriguing social plot ...more
Jun 19, 2017 rated it it was ok
Shelves: sci-fi
I wanted to like this story but just found myself unable to really get into it. It takes place in a universe where there is a fundamental difference in physics and it explores what this means, but the books main failing for me is that it does a poor job of explaining how these changes affect the world. I had to consult the web site a couple of times, with it's diagrams and maths, to try and work out what was going on as the book did a poor job of explaining it's rules to me. This left me unable ...more
Sep 26, 2017 rated it it was ok  ·  review of another edition
I generally love Greg Egan's books, but this one just never grabbed me. It felt like it developed too slowly and I never really became interested in the characters or plot. Didn't finish.
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Greg Egan specialises in hard science fiction stories with mathematical and quantum ontology themes, including the nature of consciousness. Other themes include genetics, simulated reality, posthumanism, mind transfer, sexuality, artificial intelligence, and the superiority of rational naturalism over religion.

He is a Hugo Award winner (and has been shortlisted for the Hugos three other times),

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