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Orthogonal #3
The Arrows of Time
In an alien universe where space and time play by different rules, interstellar voyages last longer for the travellers than for those they left behind. After six generations in flight, the inhabitants of the mountain-sized spacecraft the Peerless have used their borrowed time to develop advanced technology that could save their home world from annihilation.
But not every traveller feels allegiance to a world they have never seen, and as tensions mount over the risks of turning the ship around and starting the long voyage home, a new complication arises: the prospect of constructing a messaging system that will give the Peerless news of its own future.
While some of the crew welcome the opportunity to be warned of impending dangers - and perhaps even hear reports of the ship's triumphant return - others are convinced that knowing what lies ahead will be oppressive, and that the system will be abused. Agata longs for a chance to hear a message from the ancestors back on the home world, proving that the sacrifices of the travellers have not been in vain, but her most outspoken rival, Ramiro, fears that the system will undermine every decision the travellers make.
When a vote fails to settle the matter and dissent erupts into violence, Ramiro, Agata and their allies must seek a new way to bring peace to the Peerless - by traveling to a world where time runs in reverse.
But not every traveller feels allegiance to a world they have never seen, and as tensions mount over the risks of turning the ship around and starting the long voyage home, a new complication arises: the prospect of constructing a messaging system that will give the Peerless news of its own future.
While some of the crew welcome the opportunity to be warned of impending dangers - and perhaps even hear reports of the ship's triumphant return - others are convinced that knowing what lies ahead will be oppressive, and that the system will be abused. Agata longs for a chance to hear a message from the ancestors back on the home world, proving that the sacrifices of the travellers have not been in vain, but her most outspoken rival, Ramiro, fears that the system will undermine every decision the travellers make.
When a vote fails to settle the matter and dissent erupts into violence, Ramiro, Agata and their allies must seek a new way to bring peace to the Peerless - by traveling to a world where time runs in reverse.
368 pages, Kindle Edition
First published November 21, 2013
36 people are currently reading
870 people want to read
About the author
Greg Egan
265 books2,763 followersGreg 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), and has also won the John W Campbell Memorial Award for Best Novel. Some of his earlier short stories feature strong elements of supernatural horror, while due to his more popular science fiction he is known within the genre for his tendency to deal with complex and highly technical material (including inventive new physics and epistemology) in an unapologetically thorough manner.
Egan is a famously reclusive author when it comes to public appearances, he doesn't attend science fiction conventions, doesn't sign books and there are no photos available of him on the web.
Excerpted from Wikipedia.
He is a Hugo Award winner (and has been shortlisted for the Hugos three other times), and has also won the John W Campbell Memorial Award for Best Novel. Some of his earlier short stories feature strong elements of supernatural horror, while due to his more popular science fiction he is known within the genre for his tendency to deal with complex and highly technical material (including inventive new physics and epistemology) in an unapologetically thorough manner.
Egan is a famously reclusive author when it comes to public appearances, he doesn't attend science fiction conventions, doesn't sign books and there are no photos available of him on the web.
Excerpted from Wikipedia.
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Displaying 1 - 30 of 79 reviews
May 1, 2023
From The Eternal Flame
But seriously...
Okay, it's easy to mock this series, and I'm afraid that in my reviews of volumes 1 and 2 I was unable to resist the temptation. It's literally the geekiest thing ever written. But at the same time it's completely awesome. Greg Egan has created a new kind of novel here, a novel where physics is the hero - physics that is quite unlike our own universe's physics, but thought out in incredible detail, the level of detail that Tolkien devoted to the Elvish languages. Hardly anyone could do this. Tolkien needed to be a serious philologist to create Middle Earth, and Egan couldn't have created the Orthogonal universe without having pretty nontrivial skills in maths and physics.
He's got page after page of background on his site, corresponding to all those notebooks that Tolkien filled with the linguistics of Quenya and Sindarin. Geeks will be looking at it for years, discussing whether the ideas really work or not and trying to patch them where there seem to be holes - because dammit, you want this to work! To take just one example, the plot requires it to be possible to reach an infinite velocity in a finite time; in the books, Egan never really explains this. If you're used to our universe's physics, it seems impossible. Infinite velocity would imply infinite energy, and how could you acquire infinite energy?
But the orthogonal universe is quite different, and in particular its version of energy is quite different. You don't need an infinite amount of energy to reach an infinite velocity. Accelerating means rotating your 4-velocity, and in the orthogonal universe uniform acceleration rotates your 4-velocity at a constant rate. So it takes a finite time to rotate it by π/2, which is what you need to reach infinite velocity.
If that made absolutely no sense to you, you most likely don't want to read Orthogonal. If it kind of half made sense and you're wondering what the other half is, go out now and buy a copy of The Clockwork Rocket. You're about to take a trip you'll never forget.
____________________
mannyrayner: Could you write the precis of a fanfic set in the Greg Egan "Orthogonal" universe, explaining what addition you would make to his fictional physics and how the plot would use it?
ChatGPT-4: Title: Orthogonal: The Tesseract Enigma
Premise: Set within the universe of Greg Egan's "Orthogonal" trilogy, this fanfic explores an uncharted realm of the unique physics established in the original series. The story introduces a new discovery, the Tesseract Drive, which enables travel across alternate timelines and challenges the characters to confront the implications of their newfound power.
Addition to the fictional physics: In the "Orthogonal" universe, the fundamental physics differs from our own due to a crucial variation in the spacetime metric. This fanfic introduces the Tesseract Drive, a device that manipulates the orthogonal time dimension, allowing the characters to access alternate timelines. The Tesseract Drive operates by generating controlled time waves that resonate with the orthogonal time dimension, creating a bridge to different temporal possibilities.
Plot: The inhabitants of the Peerless have achieved a deep understanding of their universe's physics and have settled on a new world, free from the existential threats that once haunted them. Among them, a brilliant scientist, Dr. Ilara Tendris, makes a groundbreaking discovery: the Tesseract Drive.
With this new technology, the inhabitants of the Peerless can explore alternate timelines, witnessing the outcomes of different choices and decisions. As the people grapple with the moral and philosophical implications of their newfound power, a mysterious force threatens their world.
Driven by curiosity and a desire to understand the nature of this enigmatic force, Dr. Tendris and her team embark on a perilous journey across alternate timelines. Their quest takes them to the brink of their universe's boundaries, where they must confront the limits of their understanding and face the consequences of their actions.
As Dr. Tendris delves deeper into the orthogonal time dimension, she uncovers a profound truth that binds together the disparate timelines. The key to understanding the mysterious force lies in the delicate balance between the orthogonal timelines and the fabric of existence itself.
With the fate of their world hanging in the balance, Dr. Tendris and her team must make an impossible choice, one that will not only determine the future of their people but the very nature of their reality.
"Orthogonal: The Tesseract Enigma" takes fans on a thrilling adventure through the fascinating universe of Greg Egan's creation, blending hard science fiction with a captivating narrative that explores the boundaries of knowledge, choice, and consequence.
mannyrayner: I like it, sounds very Egan! So, if I understand this correctly, in your fanfic it turns out that Orthogonal space is really five-dimensional, with the additional dimension crossing multiple timelines. I can immediately see the Egan fans wondering about how this meshes with Orthogonal quantum physics. Do the multiple timelines also instantiate an Orthogonal quantum multiverse? If so, does the Tesseract Drive function by exploiting Orthogonal quantum effects?
ChatGPT-4: I'm glad you liked the fanfic concept! You're correct in understanding that the fanfic introduces an additional dimension to the Orthogonal universe, which allows for the existence of multiple timelines. This additional dimension, coupled with the orthogonal time dimension, indeed results in a five-dimensional space.
As for the interaction between the multiple timelines and the Orthogonal quantum physics, you raise an intriguing possibility. The fanfic could explore the concept of an Orthogonal quantum multiverse, where each timeline corresponds to a different branch of the multiverse. In this interpretation, the Tesseract Drive would function by exploiting Orthogonal quantum effects.
The Tesseract Drive could work by selectively creating and manipulating entangled states in the Orthogonal quantum multiverse, enabling travel between alternate timelines. This would be a delicate and complex process, as the characters would need to navigate the intricacies of Orthogonal quantum physics while ensuring the stability of their own universe.
By incorporating these ideas, the fanfic could delve deeper into the relationship between the orthogonal time dimension, multiple timelines, and the quantum nature of the Orthogonal universe. This would provide an exciting opportunity for fans of Greg Egan's work to further explore the fascinating and intricate world he has created, while offering new challenges and discoveries for the characters to encounter.
But seriously...
Okay, it's easy to mock this series, and I'm afraid that in my reviews of volumes 1 and 2 I was unable to resist the temptation. It's literally the geekiest thing ever written. But at the same time it's completely awesome. Greg Egan has created a new kind of novel here, a novel where physics is the hero - physics that is quite unlike our own universe's physics, but thought out in incredible detail, the level of detail that Tolkien devoted to the Elvish languages. Hardly anyone could do this. Tolkien needed to be a serious philologist to create Middle Earth, and Egan couldn't have created the Orthogonal universe without having pretty nontrivial skills in maths and physics.
He's got page after page of background on his site, corresponding to all those notebooks that Tolkien filled with the linguistics of Quenya and Sindarin. Geeks will be looking at it for years, discussing whether the ideas really work or not and trying to patch them where there seem to be holes - because dammit, you want this to work! To take just one example, the plot requires it to be possible to reach an infinite velocity in a finite time; in the books, Egan never really explains this. If you're used to our universe's physics, it seems impossible. Infinite velocity would imply infinite energy, and how could you acquire infinite energy?
But the orthogonal universe is quite different, and in particular its version of energy is quite different. You don't need an infinite amount of energy to reach an infinite velocity. Accelerating means rotating your 4-velocity, and in the orthogonal universe uniform acceleration rotates your 4-velocity at a constant rate. So it takes a finite time to rotate it by π/2, which is what you need to reach infinite velocity.
If that made absolutely no sense to you, you most likely don't want to read Orthogonal. If it kind of half made sense and you're wondering what the other half is, go out now and buy a copy of The Clockwork Rocket. You're about to take a trip you'll never forget.
____________________
mannyrayner: Could you write the precis of a fanfic set in the Greg Egan "Orthogonal" universe, explaining what addition you would make to his fictional physics and how the plot would use it?
ChatGPT-4: Title: Orthogonal: The Tesseract Enigma
Premise: Set within the universe of Greg Egan's "Orthogonal" trilogy, this fanfic explores an uncharted realm of the unique physics established in the original series. The story introduces a new discovery, the Tesseract Drive, which enables travel across alternate timelines and challenges the characters to confront the implications of their newfound power.
Addition to the fictional physics: In the "Orthogonal" universe, the fundamental physics differs from our own due to a crucial variation in the spacetime metric. This fanfic introduces the Tesseract Drive, a device that manipulates the orthogonal time dimension, allowing the characters to access alternate timelines. The Tesseract Drive operates by generating controlled time waves that resonate with the orthogonal time dimension, creating a bridge to different temporal possibilities.
Plot: The inhabitants of the Peerless have achieved a deep understanding of their universe's physics and have settled on a new world, free from the existential threats that once haunted them. Among them, a brilliant scientist, Dr. Ilara Tendris, makes a groundbreaking discovery: the Tesseract Drive.
With this new technology, the inhabitants of the Peerless can explore alternate timelines, witnessing the outcomes of different choices and decisions. As the people grapple with the moral and philosophical implications of their newfound power, a mysterious force threatens their world.
Driven by curiosity and a desire to understand the nature of this enigmatic force, Dr. Tendris and her team embark on a perilous journey across alternate timelines. Their quest takes them to the brink of their universe's boundaries, where they must confront the limits of their understanding and face the consequences of their actions.
As Dr. Tendris delves deeper into the orthogonal time dimension, she uncovers a profound truth that binds together the disparate timelines. The key to understanding the mysterious force lies in the delicate balance between the orthogonal timelines and the fabric of existence itself.
With the fate of their world hanging in the balance, Dr. Tendris and her team must make an impossible choice, one that will not only determine the future of their people but the very nature of their reality.
"Orthogonal: The Tesseract Enigma" takes fans on a thrilling adventure through the fascinating universe of Greg Egan's creation, blending hard science fiction with a captivating narrative that explores the boundaries of knowledge, choice, and consequence.
mannyrayner: I like it, sounds very Egan! So, if I understand this correctly, in your fanfic it turns out that Orthogonal space is really five-dimensional, with the additional dimension crossing multiple timelines. I can immediately see the Egan fans wondering about how this meshes with Orthogonal quantum physics. Do the multiple timelines also instantiate an Orthogonal quantum multiverse? If so, does the Tesseract Drive function by exploiting Orthogonal quantum effects?
ChatGPT-4: I'm glad you liked the fanfic concept! You're correct in understanding that the fanfic introduces an additional dimension to the Orthogonal universe, which allows for the existence of multiple timelines. This additional dimension, coupled with the orthogonal time dimension, indeed results in a five-dimensional space.
As for the interaction between the multiple timelines and the Orthogonal quantum physics, you raise an intriguing possibility. The fanfic could explore the concept of an Orthogonal quantum multiverse, where each timeline corresponds to a different branch of the multiverse. In this interpretation, the Tesseract Drive would function by exploiting Orthogonal quantum effects.
The Tesseract Drive could work by selectively creating and manipulating entangled states in the Orthogonal quantum multiverse, enabling travel between alternate timelines. This would be a delicate and complex process, as the characters would need to navigate the intricacies of Orthogonal quantum physics while ensuring the stability of their own universe.
By incorporating these ideas, the fanfic could delve deeper into the relationship between the orthogonal time dimension, multiple timelines, and the quantum nature of the Orthogonal universe. This would provide an exciting opportunity for fans of Greg Egan's work to further explore the fascinating and intricate world he has created, while offering new challenges and discoveries for the characters to encounter.
August 8, 2019
I'm still in awe of this trilogy, and only for one reason: the math.
Oh, god, no, please, no, no more math, right? Well, Egan took math and built a universe for us and then populated it with interesting aliens discovering their universe from step to step. You could call this a mystery, or you could call it the basic drive to KNOW, but either way, we're taking this ride and Egan is taking us FAR off the charts of normal SF.
Say what you will about the characters or the basic plots. The fact that he has twirled them and us around a VERY different kind of universe is amazing.
And our generational mountain-ship aliens are caught in a very determination/non-determination story loop. Which is very a familiar territory for SF fans. So even if you don't quite GET the math which kinda inverts the whole space-effect and inverts the whole light effect. Where life forms and rocks emit light, where gravity is curved on the other side, where there is no light-speed, but rotation can take you to infinite energies and space-like loops in time.
Oh, hell-yes.
Our generational mountain-ship is caught in something akin to a civil-war between those who want to see into the fixed future and deal with the effects of knowing--on the resulting changes in the future because they knew, versus those who choose to just DO WHAT THEY WERE GOING TO DO ANYWAY. :)
And while there's a bit less math in this one than the first two books, thank goodness, it does resolve a few of the more interesting feminist issues regarding DYING just because you gave birth. I'm quite happy with the result. :)
Bottom-line: Do I recommend this for all SF readers? No. But for anyone who wants to be challenged, to have something really super-number-juicy to sink your brain into? Definitely. Read this trilogy. :)
Oh, god, no, please, no, no more math, right? Well, Egan took math and built a universe for us and then populated it with interesting aliens discovering their universe from step to step. You could call this a mystery, or you could call it the basic drive to KNOW, but either way, we're taking this ride and Egan is taking us FAR off the charts of normal SF.
Say what you will about the characters or the basic plots. The fact that he has twirled them and us around a VERY different kind of universe is amazing.
And our generational mountain-ship aliens are caught in a very determination/non-determination story loop. Which is very a familiar territory for SF fans. So even if you don't quite GET the math which kinda inverts the whole space-effect and inverts the whole light effect. Where life forms and rocks emit light, where gravity is curved on the other side, where there is no light-speed, but rotation can take you to infinite energies and space-like loops in time.
Oh, hell-yes.
Our generational mountain-ship is caught in something akin to a civil-war between those who want to see into the fixed future and deal with the effects of knowing--on the resulting changes in the future because they knew, versus those who choose to just DO WHAT THEY WERE GOING TO DO ANYWAY. :)
And while there's a bit less math in this one than the first two books, thank goodness, it does resolve a few of the more interesting feminist issues regarding DYING just because you gave birth. I'm quite happy with the result. :)
Bottom-line: Do I recommend this for all SF readers? No. But for anyone who wants to be challenged, to have something really super-number-juicy to sink your brain into? Definitely. Read this trilogy. :)
December 24, 2013
Note: this is going to be something more of a review of the entire trilogy, because I don't feel like writing up individual reviews for each book and I want to make sure I write down somewhere what a monumental achievement these books are when taken together.
Excellent conclusion to the Orthogonal trilogy. It's kind of breathtaking to see what Egan has accomplished here. He started out with an incredibly simple premise -- flipping one sign in one equation -- and then re-derived modern physics from this new principle. Not satisfied with this, he then figured out what chemistry and biology might look like in this universe, and created a vivid world filled with interesting characters.
Each book in the trilogy, moreover, has a plot that centers around some problem arising from the new physics: in the first, an encounter with a debris cloud moving on an orthogonal path to the home world; in the second, the creation of a limitless energy source; and in this third volume, the implications of the fact that time travel is possible in the Orthogonal universe. To top it all off, all three books show working scientists figuring out details of their universe, meaning that Egan also came up with plausible alternative theories for his new universe, thought of experiments that would distinguish them, and then had his characters carry them out. And throughout the whole process, his scientist characters have ego clashes, pet theories, and in general show off the glorious messiness of the scientific process.
I'm flabbergasted that he pulled off this feat and produced three readable books. Bravo.
Excellent conclusion to the Orthogonal trilogy. It's kind of breathtaking to see what Egan has accomplished here. He started out with an incredibly simple premise -- flipping one sign in one equation -- and then re-derived modern physics from this new principle. Not satisfied with this, he then figured out what chemistry and biology might look like in this universe, and created a vivid world filled with interesting characters.
Each book in the trilogy, moreover, has a plot that centers around some problem arising from the new physics: in the first, an encounter with a debris cloud moving on an orthogonal path to the home world; in the second, the creation of a limitless energy source; and in this third volume, the implications of the fact that time travel is possible in the Orthogonal universe. To top it all off, all three books show working scientists figuring out details of their universe, meaning that Egan also came up with plausible alternative theories for his new universe, thought of experiments that would distinguish them, and then had his characters carry them out. And throughout the whole process, his scientist characters have ego clashes, pet theories, and in general show off the glorious messiness of the scientific process.
I'm flabbergasted that he pulled off this feat and produced three readable books. Bravo.
May 19, 2021
I time-traveled once. Literally, if not quite in the Hollywood sense of whirring machines and flashing lights. One day, while I was teaching, I traveled back in time about two hours. Smoothly, with no sensorial discontinuity (I wasn’t in the middle of talking or anything like that). The mechanical watch I had with me broke - which may lead the more skeptical to believe I merely lost track of time. Except my notebook, filled with detailed notes and time-stamped records of these past two hours, had traveled with me.
Surprised, I queried my students if the same had happened to them. It hadn’t, and they thought I was joking. It’s an irony - I won’t say strange one because it’s obvious in hindsight - that arguably the most interesting thing that will ever happen in my life also turned out to be one of the dullest. I had to repeat those same two hours (while of course only being paid for them once), which weren’t particularly exciting the first time around.
I of course tried to use my foreknowledge to improve my teaching. I already knew *exactly* where my students would stumble, the questions they would ask, the problems they would miss. But I was able to change very little. Which, if you have much experience teaching, should not be too surprising.
First of all, a veteran teacher already knows the problems and ideas that different types of minds will struggle with. Changing the probability from 90% to 100% doesn’t do much. Second, teaching is not about transmitting knowledge from teacher to student, it’s about guiding the student into their own understanding. Minds are built from the inside-out. So what if I know the questions they ask? Answering them before they ask actually hurts their learning process by short-circuiting their own involvement in the process.
But I digress. My primary point is that knowledge plays a much smaller role in both personal and civilization-level advancement than most people credit. To some, knowledge is literally the ONLY metric of advancement. But, short of a definition of knowledge so wide as to be universal, this simply isn’t the case.
Take climate change for example. We already possess the scientific and technical know-how to reduce our carbon emissions. Solar power is already more cost-efficient than any other form of large-scale power generation. Extremely good electric and hybrid cars exist. But we lack the political and economical will, discipline, and maturity to evolve our electrical habits, both personal and communal.
This third and final book in the Orthogonal trilogy is in large part about this question of knowledge’s power, especially knowledge from the future. Thanks to the special physics of the Orthogonal universe, the engineers of the Mountain develop a camera that can see light from the future. Which they shortly use to develop a messaging system able to receive messages from their future selves.
Thus is the core conflict of Arrows of Time. Half of the citizens of the mountain strongly oppose such a system, for they believe it will have detrimental effects to their psychology and sense of free will [see Ted Chiang’s short story “What’s Expected of Us” for a short but incisive take on this]. The other half believe these messages from their future could prove pivotal to the survival of their mission. After all, couldn’t they receive a warning about a near-miss from a meteor strike, thus precipitating a course change that will make that near-miss (as opposed to being struck) a reality?
As that last question presages, any time you deal with time travel and fore-knowledge, you’ll swiftly find yourself in the Swamp of Destiny (and free will and determinism and etc), and Egan does not shy away. Of course he doesn’t, he’s Greg Egan! In fact, he double-downs; another big chunk of the book involves a journey to a planet from the orthogonal cluster - that is a planet whose ‘arrow of time’ (i.e. entropy direction) is flipped from theirs. If you’ve ever seen the film Tenet, it’s basically that, with better science and consistency. If you haven’t then strange things happen like dust from the planet gets into their spaceship BEFORE it even lands on the planet (because from the “perspective” of the planet and its dust, the ship isn’t landing… but leaving).
I won’t pretend a super clear understanding of the physics explored in this book. My own personal intuition is that interaction between matter with opposing arrows of time would result in mutual annihilation, like in a matter-antimatter reaction. Indeed in some Formalisms (Feynman/Wheeler’s as opposed to the more popular Hamiltonian), anti-matter IS time-reversed matter. But in this book and in more popular physics, this symmetry is rejected. Anti-matter and time-reversed matter are different.
Overall, I found this third book the most satisfying and Egan-like. The first book suffers because large chunks of it must be spent exploring the mundane realities of the Orthogonal universe and the civilization that we’re following. Yalda - the protagonist of the first book - does science not because she has some end-goal or purpose but simply out of curiosity. This makes it inherently less dramatic and interesting than the scientific explorations of these latter two books, in which science must save their entire civilization or fix some more immediate problem (such as women dying in order to give birth).
What’s more, the science of the first book is elementary in nature - the most basic ideas of atoms/electrons (“luxagens”) and light. Different in the Orthogonal universe and thus harder to understand but still ultimately at the high-school chemistry/physics level. Whereas the science in this last book is more cutting edge, more speculative and therefore interesting, to me at least.
Even so, even though I did like this third book best, I wouldn’t change any of what I wrote in my review of the first book. The whole series is still an astounding creation, a display of genius so far beyond the achievements of most sci-fi authors as to render Egan’s books a genre of their own. But for that same reason, they’re also incredibly niche. Just look at the reviews here on GR: how many demonstrate a technical appreciation or comprehension of the Orthogonal universe?
So my conclusion is much the same. Read it, if everything I’ve written sounds like something enjoyable, but also understand that the process of reading an Egan differs greatly from the process of reading most novels. You shouldn’t expect to easily and clearly understand every sentence, diagram, and idea. But you don’t need to, either. Instead, I’ve come to consider Egan a sort of Scientific Shakespeare. Just as I can appreciate the beauty and lyricism of the Bard’s writing without perfectly understanding every single line, so too can I enjoy the beauty and lyricism of Egan’s science, even when I’ve become lost, like an Alice in Scienceland.
Surprised, I queried my students if the same had happened to them. It hadn’t, and they thought I was joking. It’s an irony - I won’t say strange one because it’s obvious in hindsight - that arguably the most interesting thing that will ever happen in my life also turned out to be one of the dullest. I had to repeat those same two hours (while of course only being paid for them once), which weren’t particularly exciting the first time around.
I of course tried to use my foreknowledge to improve my teaching. I already knew *exactly* where my students would stumble, the questions they would ask, the problems they would miss. But I was able to change very little. Which, if you have much experience teaching, should not be too surprising.
First of all, a veteran teacher already knows the problems and ideas that different types of minds will struggle with. Changing the probability from 90% to 100% doesn’t do much. Second, teaching is not about transmitting knowledge from teacher to student, it’s about guiding the student into their own understanding. Minds are built from the inside-out. So what if I know the questions they ask? Answering them before they ask actually hurts their learning process by short-circuiting their own involvement in the process.
But I digress. My primary point is that knowledge plays a much smaller role in both personal and civilization-level advancement than most people credit. To some, knowledge is literally the ONLY metric of advancement. But, short of a definition of knowledge so wide as to be universal, this simply isn’t the case.
Take climate change for example. We already possess the scientific and technical know-how to reduce our carbon emissions. Solar power is already more cost-efficient than any other form of large-scale power generation. Extremely good electric and hybrid cars exist. But we lack the political and economical will, discipline, and maturity to evolve our electrical habits, both personal and communal.
This third and final book in the Orthogonal trilogy is in large part about this question of knowledge’s power, especially knowledge from the future. Thanks to the special physics of the Orthogonal universe, the engineers of the Mountain develop a camera that can see light from the future. Which they shortly use to develop a messaging system able to receive messages from their future selves.
Thus is the core conflict of Arrows of Time. Half of the citizens of the mountain strongly oppose such a system, for they believe it will have detrimental effects to their psychology and sense of free will [see Ted Chiang’s short story “What’s Expected of Us” for a short but incisive take on this]. The other half believe these messages from their future could prove pivotal to the survival of their mission. After all, couldn’t they receive a warning about a near-miss from a meteor strike, thus precipitating a course change that will make that near-miss (as opposed to being struck) a reality?
As that last question presages, any time you deal with time travel and fore-knowledge, you’ll swiftly find yourself in the Swamp of Destiny (and free will and determinism and etc), and Egan does not shy away. Of course he doesn’t, he’s Greg Egan! In fact, he double-downs; another big chunk of the book involves a journey to a planet from the orthogonal cluster - that is a planet whose ‘arrow of time’ (i.e. entropy direction) is flipped from theirs. If you’ve ever seen the film Tenet, it’s basically that, with better science and consistency. If you haven’t then strange things happen like dust from the planet gets into their spaceship BEFORE it even lands on the planet (because from the “perspective” of the planet and its dust, the ship isn’t landing… but leaving).
I won’t pretend a super clear understanding of the physics explored in this book. My own personal intuition is that interaction between matter with opposing arrows of time would result in mutual annihilation, like in a matter-antimatter reaction. Indeed in some Formalisms (Feynman/Wheeler’s as opposed to the more popular Hamiltonian), anti-matter IS time-reversed matter. But in this book and in more popular physics, this symmetry is rejected. Anti-matter and time-reversed matter are different.
Overall, I found this third book the most satisfying and Egan-like. The first book suffers because large chunks of it must be spent exploring the mundane realities of the Orthogonal universe and the civilization that we’re following. Yalda - the protagonist of the first book - does science not because she has some end-goal or purpose but simply out of curiosity. This makes it inherently less dramatic and interesting than the scientific explorations of these latter two books, in which science must save their entire civilization or fix some more immediate problem (such as women dying in order to give birth).
What’s more, the science of the first book is elementary in nature - the most basic ideas of atoms/electrons (“luxagens”) and light. Different in the Orthogonal universe and thus harder to understand but still ultimately at the high-school chemistry/physics level. Whereas the science in this last book is more cutting edge, more speculative and therefore interesting, to me at least.
Even so, even though I did like this third book best, I wouldn’t change any of what I wrote in my review of the first book. The whole series is still an astounding creation, a display of genius so far beyond the achievements of most sci-fi authors as to render Egan’s books a genre of their own. But for that same reason, they’re also incredibly niche. Just look at the reviews here on GR: how many demonstrate a technical appreciation or comprehension of the Orthogonal universe?
So my conclusion is much the same. Read it, if everything I’ve written sounds like something enjoyable, but also understand that the process of reading an Egan differs greatly from the process of reading most novels. You shouldn’t expect to easily and clearly understand every sentence, diagram, and idea. But you don’t need to, either. Instead, I’ve come to consider Egan a sort of Scientific Shakespeare. Just as I can appreciate the beauty and lyricism of the Bard’s writing without perfectly understanding every single line, so too can I enjoy the beauty and lyricism of Egan’s science, even when I’ve become lost, like an Alice in Scienceland.
January 18, 2015
This book was reviewed on Dark Matter Zine; for more reviews, interviews and articles, go to Dark Matter Zine. Alternatively, this link is just to Dark Matter Zine's reviews.
A review by Rebecca Muir
Bec didn't include a star rating so I've guessed. — editor's note.
The Arrows of Time is the final book in Greg Egan’s Orthogonal trilogy. The first two books, The Clockwork Rocket and The Eternal Flame , have been reviewed by me previously – follow the links to get to the reviews.
This is an amazing trilogy, unlike anything I have ever read. It is set in a fictitious universe where not only are the creatures and planets different but the very laws of physics are different.
In the Orthogonal universe, time is a literal fourth dimension and the speed of light is proportional to its wavelength. Throughout all three books, the sentient creatures (we’ll call them people for want of a better term) who live in this universe gradually move through an increase in their scientific understanding and the readers are treated to explanations between characters and diagrams as the understanding unfolds.
If you are a physicist, you will likely find this fascinating. I have done high-school level physics and studied engineering at university and I didn’t understand all of it – it would have required too much extra time to stop and think it all through, and I would have lost the thread of the story. However, I understood enough to follow the implications of the discoveries for the storyline. If you have no scientific training, you will likely find all the science quite confusing but if you are willing to skim past the explanations, these books are still well worth the read.
In the Orthogonal universe, because time is a physical dimension, it is possible to arrange your travel so that your time vector is perpendicular to someone else’s. This means that you can travel for a long time without it taking up any time for the other person. When the home world realises they are facing a threat from space, a group of travellers do just that, flying the rocket Peerless into space to buy themselves time to find a solution to save the planet.
The universe Greg Egan has created has other quirks as well. The biology and reproduction system is very different. It appears that water is non-existent in this universe. Light plays a similar role to electricity in our world. The people can change their shape at will, extruding and absorbing limbs as they see fit. They require air in space, as we do, but it is not to breathe – it is to keep them cool and stop them dying of hyperthermia. There are many strange things about the universe Greg Egan has imagined, but the characters are so vivid that I found myself quickly drawn into the story, identifying so well with the characters that they quickly lost their strangeness.
This third book, the Arrows of Time, is set a couple of generations after the second book. Technology on the Peerless has progressed rapidly and they are now at the stage where they can turn the ship around and head for home. They are close to a solution for the home world and are confident that it can be perfected in the six generations it will take them to return. However, there are still discoveries to be made and challenges to face. A major challenge comes in the form of a message system, which has the potential (due to the fact that light can travel against your time stream in this universe) to allow messages to be sent back from the future. This technology splits the Peerless as people have to decide whether they want to know what their future holds, or not.
Meanwhile, the turning of the Peerless allows a new opportunity. There are planets which they are now in sync with and an expedition is mounted to one of them. This will allow some measurements to be made which will have implications for a vital theorem, as well as provide a chance to explore the possibility of creating a colony if the divisions on the Peerless cannot be peacefully mended. The main characters end up on this expedition that proves to be important for the future of not only the Peerless but also the home world.
Besides the science, this book has a number of issues it raises and explores. The question of free will and destiny is a big one – if the characters already know what will happen, how much of what they do is free will? Is what happens just an unchangeable destiny? How much can knowledge of the future give them hope, and how much can it paralyze them from making decisions?
Another theme which has been a part of the trilogy is that of gender roles, in particular how they are viewed by society. In the first book, the culture of the home world is very patriarchal. The role of a woman is to help her mate and then bear children. On board the Peerless, things have been changing. In this third book, society has now come to a point where males are feeling threatened – does the species actually need them? Will males cease to exist? Concepts of gender and gender roles are explored and an interesting conclusion is reached.
The species in this universe, by the nature of their biological differences, face different challenges than humanity does in the area of gender politics and discrimination, but there are overlaps and relevant observations made. I found the potential challenge of the returning Peerless to the culture of the home world particularly interesting. It can be hard to be faced with very different values to your own, and to have to sort through where your own values come from, and what is worth holding onto.
Another major theme explored by the book is that of legacy. What makes your life meaningful? Is contributing some small increment to the collective knowledge enough, or do we need to make our mark in a big way? Is it enough to have children, and make them our legacy? Is it ok to choose not to reproduce – what becomes of us if we don’t pass on a part of ourselves through our children?
The Arrows of Time was, in some ways, harder to read than the first two books in this trilogy. The implications of the time arrows was quite mind boggling and I found some of the subject matter a bit more depressing than the other books. However, it was as well written and interesting as the others, and brought the series to a good conclusion. Greg Egan is to be congratulated on this trilogy – it is an amazing piece of work. The science, the universe he has created, the themes he explores and the rich, vibrant characters all make this a superb trilogy that I highly recommend.
A review by Rebecca Muir
Bec didn't include a star rating so I've guessed. — editor's note.
The Arrows of Time is the final book in Greg Egan’s Orthogonal trilogy. The first two books, The Clockwork Rocket and The Eternal Flame , have been reviewed by me previously – follow the links to get to the reviews.
This is an amazing trilogy, unlike anything I have ever read. It is set in a fictitious universe where not only are the creatures and planets different but the very laws of physics are different.
In the Orthogonal universe, time is a literal fourth dimension and the speed of light is proportional to its wavelength. Throughout all three books, the sentient creatures (we’ll call them people for want of a better term) who live in this universe gradually move through an increase in their scientific understanding and the readers are treated to explanations between characters and diagrams as the understanding unfolds.
If you are a physicist, you will likely find this fascinating. I have done high-school level physics and studied engineering at university and I didn’t understand all of it – it would have required too much extra time to stop and think it all through, and I would have lost the thread of the story. However, I understood enough to follow the implications of the discoveries for the storyline. If you have no scientific training, you will likely find all the science quite confusing but if you are willing to skim past the explanations, these books are still well worth the read.
In the Orthogonal universe, because time is a physical dimension, it is possible to arrange your travel so that your time vector is perpendicular to someone else’s. This means that you can travel for a long time without it taking up any time for the other person. When the home world realises they are facing a threat from space, a group of travellers do just that, flying the rocket Peerless into space to buy themselves time to find a solution to save the planet.
The universe Greg Egan has created has other quirks as well. The biology and reproduction system is very different. It appears that water is non-existent in this universe. Light plays a similar role to electricity in our world. The people can change their shape at will, extruding and absorbing limbs as they see fit. They require air in space, as we do, but it is not to breathe – it is to keep them cool and stop them dying of hyperthermia. There are many strange things about the universe Greg Egan has imagined, but the characters are so vivid that I found myself quickly drawn into the story, identifying so well with the characters that they quickly lost their strangeness.
This third book, the Arrows of Time, is set a couple of generations after the second book. Technology on the Peerless has progressed rapidly and they are now at the stage where they can turn the ship around and head for home. They are close to a solution for the home world and are confident that it can be perfected in the six generations it will take them to return. However, there are still discoveries to be made and challenges to face. A major challenge comes in the form of a message system, which has the potential (due to the fact that light can travel against your time stream in this universe) to allow messages to be sent back from the future. This technology splits the Peerless as people have to decide whether they want to know what their future holds, or not.
Meanwhile, the turning of the Peerless allows a new opportunity. There are planets which they are now in sync with and an expedition is mounted to one of them. This will allow some measurements to be made which will have implications for a vital theorem, as well as provide a chance to explore the possibility of creating a colony if the divisions on the Peerless cannot be peacefully mended. The main characters end up on this expedition that proves to be important for the future of not only the Peerless but also the home world.
Besides the science, this book has a number of issues it raises and explores. The question of free will and destiny is a big one – if the characters already know what will happen, how much of what they do is free will? Is what happens just an unchangeable destiny? How much can knowledge of the future give them hope, and how much can it paralyze them from making decisions?
Another theme which has been a part of the trilogy is that of gender roles, in particular how they are viewed by society. In the first book, the culture of the home world is very patriarchal. The role of a woman is to help her mate and then bear children. On board the Peerless, things have been changing. In this third book, society has now come to a point where males are feeling threatened – does the species actually need them? Will males cease to exist? Concepts of gender and gender roles are explored and an interesting conclusion is reached.
The species in this universe, by the nature of their biological differences, face different challenges than humanity does in the area of gender politics and discrimination, but there are overlaps and relevant observations made. I found the potential challenge of the returning Peerless to the culture of the home world particularly interesting. It can be hard to be faced with very different values to your own, and to have to sort through where your own values come from, and what is worth holding onto.
Another major theme explored by the book is that of legacy. What makes your life meaningful? Is contributing some small increment to the collective knowledge enough, or do we need to make our mark in a big way? Is it enough to have children, and make them our legacy? Is it ok to choose not to reproduce – what becomes of us if we don’t pass on a part of ourselves through our children?
The Arrows of Time was, in some ways, harder to read than the first two books in this trilogy. The implications of the time arrows was quite mind boggling and I found some of the subject matter a bit more depressing than the other books. However, it was as well written and interesting as the others, and brought the series to a good conclusion. Greg Egan is to be congratulated on this trilogy – it is an amazing piece of work. The science, the universe he has created, the themes he explores and the rich, vibrant characters all make this a superb trilogy that I highly recommend.
September 2, 2019
The first two books in this series were good, but this one felt like the payoff they were building up to. It would have been worth reading the first two even if they were only okay.
December 27, 2013
This is the third book in Egan's Orthogonal trilogy, after The Clockwork Rocket and The Eternal Flame. If you haven't read either, go and do it now - and don't read the rest of this as there are spoilers.
If you do know the earlier books, then this is what you'd expect: a continuation of the narrative of the travellers in their mountain-turned-spaceship, journeying orthogonally to the homeworld to give themselves the time needed to develop their science and save the planet from destruction. Six generations have passed now since the Peerless took off, and things have moved on from clockwork-and-sunstone to photonics. Again, the story portrays a slice of life aboard the ship - both the scientific controversies and the social tensions among the crew, as they struggle to come to terms with the turning point of their mission. Should they follow the mission plan laid down for them by Yalda, and return to save the "ancestors" - or continue the journey and find a new and habitable planet? The desire to find a place to settle leads a few brave explorers to land on a time-reversed planet where things are rather... backwards. It's quite mind-bending following what happens next: whatever these books are they're not simple, escapist reads.
As ever, Egan has worked the physics through to the last detail (and more is available on his website). I realised as I came to the end of this book that he's done nothing less than write a trilogy where the central character - whose nature and ways we gradually discover - is the universe itself, no, not the universe but a universe because it's not ours. the rules are recognisable, but different. And as if that's not enough, he's woven into it the most perfect realised story of social progress, as the people - whose nature we also discover gradually - confront their own biology and society to construct a better system where they can all be fulfilled.
It's an audacious sequence, hard to follow at times, challenging and clever.
I'm sorry the trip is over, but I've enjoyed the journey so much. Thank you Mr Egan.
If you do know the earlier books, then this is what you'd expect: a continuation of the narrative of the travellers in their mountain-turned-spaceship, journeying orthogonally to the homeworld to give themselves the time needed to develop their science and save the planet from destruction. Six generations have passed now since the Peerless took off, and things have moved on from clockwork-and-sunstone to photonics. Again, the story portrays a slice of life aboard the ship - both the scientific controversies and the social tensions among the crew, as they struggle to come to terms with the turning point of their mission. Should they follow the mission plan laid down for them by Yalda, and return to save the "ancestors" - or continue the journey and find a new and habitable planet? The desire to find a place to settle leads a few brave explorers to land on a time-reversed planet where things are rather... backwards. It's quite mind-bending following what happens next: whatever these books are they're not simple, escapist reads.
As ever, Egan has worked the physics through to the last detail (and more is available on his website). I realised as I came to the end of this book that he's done nothing less than write a trilogy where the central character - whose nature and ways we gradually discover - is the universe itself, no, not the universe but a universe because it's not ours. the rules are recognisable, but different. And as if that's not enough, he's woven into it the most perfect realised story of social progress, as the people - whose nature we also discover gradually - confront their own biology and society to construct a better system where they can all be fulfilled.
It's an audacious sequence, hard to follow at times, challenging and clever.
I'm sorry the trip is over, but I've enjoyed the journey so much. Thank you Mr Egan.
June 25, 2015
The ending is kind of anticlimatic. But opposing arrows of time were pretty exciting. All in all, the trilogy was worth reading, but it peaked at the first book for me.
September 8, 2019
The time has finally come.
I have finally finished Greg Egan's Orthogonal trilogy.
There really ought to be a fanfare for such an announcement.
The other books: Clockwork Rocket and Eternal Flame. Spoilers for these two naturally follow.
At the start of his one, Egan himself has written that you just won't really get this book without the previous two. I don't think I've ever come across the third book in a trilogy that said that so bluntly, and I really appreciate it. Because it is SO true: if you don't understand how light and time work in this universe (and look, I don't understand it, but I get how it's different from ours), let alone the society and what the folks are doing on this mountain-turned-spaceship, you will be so lost you'll end up in Antarctica instead of Bali.
As the second book was a few generations after the third, so here. The ship is sailing happily through the universe, and folks are still working on how to save the homeworld. Not that everyone especially wants to save the homeworld, from which they are now several generations distant - and will never see themselves anyway. So, classic generation ship angst, really. That's one issue. Then, there's what turns out to be a logical consequence of the bizarre universe Egan has set up where light travels at different speeds and some parts are orthogonal to others: that time is affected, too. Specifically, that it should be possible to set a receiver for messages from the future.
Because that couldn't possibly turn out badly.
So now there are two issues dividing the crew of the Peerless. And just to add to the problems, while the earlier issue about children has been solved - the females no longer need to either die to become their children, or starve to prevent that from happening, and they're not overpopulating - there are some people who aren't happy with the solution: especially some brothers who don't want to be compelled to care for their sister's children. So life is definitely not rainbows (which they've never seen) and roses (which they don't grow).
I love that Egan tackles such weighty topics as democracy, needs of the few vs needs of the many, the importance of choice, the place of parenthood, and so on - all in a book that literally has vector diagrams in it as it explores the outcomes of a thought experiment in physics.
From a narrative point of view, the most gripping part is when four people travel to an orthogonal world to see whether it would be habitable. Again, this is an exploration of the consequences of 'orthogonality'; time is literally going in the opposite for this world from how it is experienced by the travellers, so what could that possibly look like? What does that, what can that, mean for free will? (A whole bunch of headaches is the answer. Mostly metaphorically.) This bit is also a deeper exploration of the characters, as they interact only with each other, in very trying circumstances.
As with the other two books, I admit that I skimmed bits of the physics explanations. Including the diagrams. I read it well enough to get the point Egan is making, but I would in no way attempt to explain it.
I have a couple of thoughts that are spoilers, so don't read the rest if that's a problem... but if you've read the first two, I think you definitely need to see how the story plays out.
I have finally finished Greg Egan's Orthogonal trilogy.
There really ought to be a fanfare for such an announcement.
The other books: Clockwork Rocket and Eternal Flame. Spoilers for these two naturally follow.
At the start of his one, Egan himself has written that you just won't really get this book without the previous two. I don't think I've ever come across the third book in a trilogy that said that so bluntly, and I really appreciate it. Because it is SO true: if you don't understand how light and time work in this universe (and look, I don't understand it, but I get how it's different from ours), let alone the society and what the folks are doing on this mountain-turned-spaceship, you will be so lost you'll end up in Antarctica instead of Bali.
As the second book was a few generations after the third, so here. The ship is sailing happily through the universe, and folks are still working on how to save the homeworld. Not that everyone especially wants to save the homeworld, from which they are now several generations distant - and will never see themselves anyway. So, classic generation ship angst, really. That's one issue. Then, there's what turns out to be a logical consequence of the bizarre universe Egan has set up where light travels at different speeds and some parts are orthogonal to others: that time is affected, too. Specifically, that it should be possible to set a receiver for messages from the future.
Because that couldn't possibly turn out badly.
So now there are two issues dividing the crew of the Peerless. And just to add to the problems, while the earlier issue about children has been solved - the females no longer need to either die to become their children, or starve to prevent that from happening, and they're not overpopulating - there are some people who aren't happy with the solution: especially some brothers who don't want to be compelled to care for their sister's children. So life is definitely not rainbows (which they've never seen) and roses (which they don't grow).
I love that Egan tackles such weighty topics as democracy, needs of the few vs needs of the many, the importance of choice, the place of parenthood, and so on - all in a book that literally has vector diagrams in it as it explores the outcomes of a thought experiment in physics.
From a narrative point of view, the most gripping part is when four people travel to an orthogonal world to see whether it would be habitable. Again, this is an exploration of the consequences of 'orthogonality'; time is literally going in the opposite for this world from how it is experienced by the travellers, so what could that possibly look like? What does that, what can that, mean for free will? (A whole bunch of headaches is the answer. Mostly metaphorically.) This bit is also a deeper exploration of the characters, as they interact only with each other, in very trying circumstances.
As with the other two books, I admit that I skimmed bits of the physics explanations. Including the diagrams. I read it well enough to get the point Egan is making, but I would in no way attempt to explain it.
I have a couple of thoughts that are spoilers, so don't read the rest if that's a problem... but if you've read the first two, I think you definitely need to see how the story plays out.
January 28, 2017
Can anybody write a good trilogy of fat books?
I'm not sure this is essential reading for fans of the earlier books. Every reader must have imagined an ending or two and be curious about the author's version so there's at least one reason to bother.
But the rest of the book? It's a lighter read than the rest of the series. Readers willing to suspend disbelief may enjoy breezing through the convoluted plot, the action scenes and characters endlessly trying to talk their way through absurdity. The thing is, that's not why we read Egan, is it?
As one might have guessed from the tile, most of the book deals with the fundamental problem with the setting. Since Egan dealt with such issues very well in stories like The Hundred-Light-Year-Diary, I was hoping for better than this. I came away from the previous books thinking that a universe without a separate time dimension might work and support life... but now I'm unconvinced. At least Egan wasn't afraid to face the issues head-on and as a result the book would be a goldmine for someone who enjoys uncovering logical problems in worldbuilding.
In this series' setting, light is going to mediate interactions across perceived time and that's liable to create causal loops, paradoxes and so forth. In mainstream SF, FTL has the same problem and writers simply ignore these issues, hoping that readers will be willing and able to suspend disbelief. It seems Egan wanted to show how such things could be a serious problem in fiction but ultimately to step away and protect his plot. That's fine. But instead of simply preventing interactions across time from carrying information that can be processed, Egan went for consistency protection mechanisms operating at a much higher level. That's not an easy approach for writers unwilling to play the God card and unfortunately Egan ended up with a borderline incoherent set of rules that gets uncomfortably close to God territory.
The mere mention of "free will" in the second book had me a bit worried and that indeed presaged the mess that would be this book's plot. Possibly in order to illustrate how the lack of a separate time dimension needn't be such a big deal (see the first book's afterword), Egan tried to uphold not only folk psychology but also a rather naive account of causality without completely giving up on quantum randomness and deterministic, statistics-driven thermodynamics. That was probably an impossible task and various parts of the book stress one of the contradictory aspects of that project at the expense of another.
Though the characters reify entropic "arrows of time", Egan doesn't describe any physical mechanism that would underly these "arrows". They ought to be a systemic property and, in the same way that the second law only applies to isolated systems, there is no reason to expect thermodynamics to cause things in four-space to behave as if you lived in a three-dimensional system with an "arrow of time" unless such a system was isolated. In particular, grains of dust would not somehow carry an "arrow" with them that the Universe would strive to uphold when it comes to causal interactions with other stuff! Inasmuch as grains of dust carry their own "arrow", it only pertains to temperature gradients and suchlike within the grain.
Less obviously, stuff that comes from outside a coherent system might well appear to heat up simply by being in contact with colder stuff because it's not anyone's perspective that would decide whether heat flows from hot to cold or vice-versa. Rather it's the direction in which heat flows from hot to cold which would give that direction properties analogous to some of our time dimension's. And since heat can only flow from hot to cold because energy has been converted in order to create such a disequilibrium, if such a universe is to make causal sense, things would have make more sense from the perspective of whoever is causing entropy to rise fastest. You could for instance reasonably expect that, if a landing module suddenly seemed to draw heat from its surroundings for no apparent reason, its empty fuel tank would soon fill up with fuel while the craft rose from the ground.
Instead, Egan wants things not to appear too causally unlikely from any of two perspectives even if that requires him to bend the very thermodynamics which were suposed to underpin his account of time. Only in extreme cases does he allow the causal perspective of the most entropic agent to prevail as any other outcome would be too obviously absurd. So while fuel thankfully is expended when a pilot makes engines perform work, he can still watch dust spontaneously accumulate on his ship while on the way to a dusty destination on account of that destination having a different "arrow of time". This of course makes no sense from any kind of bottom-up perspective. Instead, things behave as if some kind of universal Maxwell demon (a Laplace-Maxwell demon?) was trying to arbitrate between reified perspectives by splitting the difference within arbitrary constraints.
There are other issues with the book like the utterly preposterous pace of technological and industrical development between books two and three (though that allows us to read about great fantasy tech such as the "photonic corset"), the inconsistent behavior of a character at one point and the return of ungrounded cosmological speculation at another (yeah, readers will get closure even in topological matters - this book is a proper ending).
But the book is primarily about thermodynamics, time travel... and of course fantasy gender issues. Very intriguing material to be sure, just by my reckoning not as well thought out as the ideas underlying most of Egan's work.
Also of note, the book has an anti-bureaucratic streak.
I'm not sure this is essential reading for fans of the earlier books. Every reader must have imagined an ending or two and be curious about the author's version so there's at least one reason to bother.
But the rest of the book? It's a lighter read than the rest of the series. Readers willing to suspend disbelief may enjoy breezing through the convoluted plot, the action scenes and characters endlessly trying to talk their way through absurdity. The thing is, that's not why we read Egan, is it?
As one might have guessed from the tile, most of the book deals with the fundamental problem with the setting. Since Egan dealt with such issues very well in stories like The Hundred-Light-Year-Diary, I was hoping for better than this. I came away from the previous books thinking that a universe without a separate time dimension might work and support life... but now I'm unconvinced. At least Egan wasn't afraid to face the issues head-on and as a result the book would be a goldmine for someone who enjoys uncovering logical problems in worldbuilding.
In this series' setting, light is going to mediate interactions across perceived time and that's liable to create causal loops, paradoxes and so forth. In mainstream SF, FTL has the same problem and writers simply ignore these issues, hoping that readers will be willing and able to suspend disbelief. It seems Egan wanted to show how such things could be a serious problem in fiction but ultimately to step away and protect his plot. That's fine. But instead of simply preventing interactions across time from carrying information that can be processed, Egan went for consistency protection mechanisms operating at a much higher level. That's not an easy approach for writers unwilling to play the God card and unfortunately Egan ended up with a borderline incoherent set of rules that gets uncomfortably close to God territory.
The mere mention of "free will" in the second book had me a bit worried and that indeed presaged the mess that would be this book's plot. Possibly in order to illustrate how the lack of a separate time dimension needn't be such a big deal (see the first book's afterword), Egan tried to uphold not only folk psychology but also a rather naive account of causality without completely giving up on quantum randomness and deterministic, statistics-driven thermodynamics. That was probably an impossible task and various parts of the book stress one of the contradictory aspects of that project at the expense of another.
Though the characters reify entropic "arrows of time", Egan doesn't describe any physical mechanism that would underly these "arrows". They ought to be a systemic property and, in the same way that the second law only applies to isolated systems, there is no reason to expect thermodynamics to cause things in four-space to behave as if you lived in a three-dimensional system with an "arrow of time" unless such a system was isolated. In particular, grains of dust would not somehow carry an "arrow" with them that the Universe would strive to uphold when it comes to causal interactions with other stuff! Inasmuch as grains of dust carry their own "arrow", it only pertains to temperature gradients and suchlike within the grain.
Less obviously, stuff that comes from outside a coherent system might well appear to heat up simply by being in contact with colder stuff because it's not anyone's perspective that would decide whether heat flows from hot to cold or vice-versa. Rather it's the direction in which heat flows from hot to cold which would give that direction properties analogous to some of our time dimension's. And since heat can only flow from hot to cold because energy has been converted in order to create such a disequilibrium, if such a universe is to make causal sense, things would have make more sense from the perspective of whoever is causing entropy to rise fastest. You could for instance reasonably expect that, if a landing module suddenly seemed to draw heat from its surroundings for no apparent reason, its empty fuel tank would soon fill up with fuel while the craft rose from the ground.
Instead, Egan wants things not to appear too causally unlikely from any of two perspectives even if that requires him to bend the very thermodynamics which were suposed to underpin his account of time. Only in extreme cases does he allow the causal perspective of the most entropic agent to prevail as any other outcome would be too obviously absurd. So while fuel thankfully is expended when a pilot makes engines perform work, he can still watch dust spontaneously accumulate on his ship while on the way to a dusty destination on account of that destination having a different "arrow of time". This of course makes no sense from any kind of bottom-up perspective. Instead, things behave as if some kind of universal Maxwell demon (a Laplace-Maxwell demon?) was trying to arbitrate between reified perspectives by splitting the difference within arbitrary constraints.
There are other issues with the book like the utterly preposterous pace of technological and industrical development between books two and three (though that allows us to read about great fantasy tech such as the "photonic corset"), the inconsistent behavior of a character at one point and the return of ungrounded cosmological speculation at another (yeah, readers will get closure even in topological matters - this book is a proper ending).
But the book is primarily about thermodynamics, time travel... and of course fantasy gender issues. Very intriguing material to be sure, just by my reckoning not as well thought out as the ideas underlying most of Egan's work.
Also of note, the book has an anti-bureaucratic streak.
January 25, 2015
"The Arrows of Time" is the 3rd book in the Orthogonal Universe trilogy by Greg Egan. It's better than the 2nd and I loved it. I will pass on a a warning from the author: One should read "The Clockwork Rocket" before reading this book. Otherwise, one will be overwhelmed.
The story: The generational space-time ship Peerless is at the turning point, meaning that it is time to turn around and thus change the arrow of time. In this universe, one can travel through time by changing direction, but conflict arises when some people oppose the turnaround. The question to be answered is, "Can people live on a planet that has an arrow of time going in the opposite direction?"
Any problems with the story? If you've followed this series up to now, you already know. You are either OK with the formulas and diagrams or you are not. One can certainly ignore them and take everything at face value.
The ending ties up most of the issues but it is too short. As I was reading along, I realized I was running out of book and I wondered how the author was going to wind this thing up. It needed more development. I forgave the author for this, understanding the limits of publishing.
I'd read this book again if I was reading the entire series. Certainly I'd read book #1 again.
The story: The generational space-time ship Peerless is at the turning point, meaning that it is time to turn around and thus change the arrow of time. In this universe, one can travel through time by changing direction, but conflict arises when some people oppose the turnaround. The question to be answered is, "Can people live on a planet that has an arrow of time going in the opposite direction?"
Any problems with the story? If you've followed this series up to now, you already know. You are either OK with the formulas and diagrams or you are not. One can certainly ignore them and take everything at face value.
The ending ties up most of the issues but it is too short. As I was reading along, I realized I was running out of book and I wondered how the author was going to wind this thing up. It needed more development. I forgave the author for this, understanding the limits of publishing.
I'd read this book again if I was reading the entire series. Certainly I'd read book #1 again.
October 23, 2022
This final book has the most narrative and least number of different experiments. One experiment really stands out for how much effect it has and how much of the book is devoted to it, which is communicating with the future. I've read/watched several other works that explore this idea, and while the exploration of its societal and individual effects are interesting, somehow even when I enjoy it, I find it somewhat lacking, if not unconvincing. That's the case here as well, but once again, probably for some unresolved personal reason, I have a feeling of incongruity.
There isn't a focus on female self-determination this time, because that issue has been resolved. I don't believe anything about its resolution to be inherently wrong, but I understand that many would find it very distressing and controversial, as did the characters, before it was moot anyway. Most of the preexisting societal problems have been resolved. That means that they have the luxury of creating exciting new problems for themselves. The most notable of these new problems is that perhaps a single issue can be more important than the functioning of democracy, or is possibly even worth risking literally everything. What legitimacy is there in a majority vote when so many feel so strongly in opposition?
In terms of characters, they exist. This is the third cast of characters, and as with the second book, there are quite a few and not much time is spent developing them. They mostly serve functional purposes, same as anything else. The characters aren't the point, but they suffice well enough for me, even when their only purpose is emotional manipulation or to illustrate an idea.
Technology is quite improved. They still don't have any electronics, but there's a lot that can be done with photonics. By the ending they're doing quite the technological marvels, though by then it just happens rather than having any explanation unlike everything prior in the trilogy. The technology becomes sufficiently advanced to be indistinguishable from magic.
As the end approached I wondered how everything would be resolved considering how much was left. There's resolution, but it's achieved through skipping enough content to what could have been a second trilogy. That's how I felt about it anyway, but I also don't want more books in the series. Overall, the ending is a reasonably unsatisfying compromise. With narrative based books I often feel that they could've been condensed, some far more than others. Because these books are so focused on scientific exploration they present an odd situation where they are both the purpose of reading but not integral to the narrative. In narrative terms this trilogy could've easily been a single book, but that would require the excision of the majority of its science, which would defeat its purpose. Unlike the previous books, there isn't enough to round it up this time.
Rating: 3.5
There isn't a focus on female self-determination this time, because that issue has been resolved. I don't believe anything about its resolution to be inherently wrong, but I understand that many would find it very distressing and controversial, as did the characters, before it was moot anyway. Most of the preexisting societal problems have been resolved. That means that they have the luxury of creating exciting new problems for themselves. The most notable of these new problems is that perhaps a single issue can be more important than the functioning of democracy, or is possibly even worth risking literally everything. What legitimacy is there in a majority vote when so many feel so strongly in opposition?
In terms of characters, they exist. This is the third cast of characters, and as with the second book, there are quite a few and not much time is spent developing them. They mostly serve functional purposes, same as anything else. The characters aren't the point, but they suffice well enough for me, even when their only purpose is emotional manipulation or to illustrate an idea.
Technology is quite improved. They still don't have any electronics, but there's a lot that can be done with photonics. By the ending they're doing quite the technological marvels, though by then it just happens rather than having any explanation unlike everything prior in the trilogy. The technology becomes sufficiently advanced to be indistinguishable from magic.
As the end approached I wondered how everything would be resolved considering how much was left. There's resolution, but it's achieved through skipping enough content to what could have been a second trilogy. That's how I felt about it anyway, but I also don't want more books in the series. Overall, the ending is a reasonably unsatisfying compromise. With narrative based books I often feel that they could've been condensed, some far more than others. Because these books are so focused on scientific exploration they present an odd situation where they are both the purpose of reading but not integral to the narrative. In narrative terms this trilogy could've easily been a single book, but that would require the excision of the majority of its science, which would defeat its purpose. Unlike the previous books, there isn't enough to round it up this time.
Rating: 3.5
November 1, 2020
12/12 will buy hardcover trilogy for my bookshelf!
Well this was a wild ride! After the second book I started to doubt if Egan manages to stick the landing in the end. I am happy to report that Egan manages the smoothest landing (takeoff in the book hahaa) I can remember in recent history.
Going into the third book I was expecting a dramallama filled contact between the travelers and ancestors, but damn! Most of the book took place around the turnaround point in the journey. There were still loads of characters and groups, that I would have liked to punch repeatedly but the story and science trumped that. Visiting the time reversed planet gave me amazing Tenet vibes and it even showed what the movie got wrong. That rock message on that planet and the last line in the book mixed so well that I dropped some tears.
Now to the brain crunching. The future data stream stuff just wrecked my brain in a good way. I was thinking about it during reading breaks and it was so hard to stay sane. Not being able to think of new ideas because it would have been sent back was just soooo good! It is the kind of fundamental flaw in the system, that makes the system not fun to use and doesn't solve the questions about the life, the universe and everything.
The return was handled so well. It was a nice end to the trilogy but it left the universe so wide open that my mind is still racing and trying to generate more to the story.
Some thoughts:
*Photonic electronics was a cool alternative to conventional electronics
*I forgot how magical the traveler technology had become until they looked at the rockets engines in the end
*The gender mixing was a cool solution/thing that happens in most Egan books hahaa
*I thought from the beginning, that the mountain was the Hurtlers and it was looping around the universe or going back and forth in time... Well some of it I got right haha
*These books had a lot more "story" in them than my previous encounters with Egans books. I still love Diaspora and Permutation City to bits but this trilogy was something else. It has history and more of a world than the other books. I don't mean that the others didn't, but this trilogy had more(?) of it and it felt great.
Well this was a wild ride! After the second book I started to doubt if Egan manages to stick the landing in the end. I am happy to report that Egan manages the smoothest landing (takeoff in the book hahaa) I can remember in recent history.
Going into the third book I was expecting a dramallama filled contact between the travelers and ancestors, but damn! Most of the book took place around the turnaround point in the journey. There were still loads of characters and groups, that I would have liked to punch repeatedly but the story and science trumped that. Visiting the time reversed planet gave me amazing Tenet vibes and it even showed what the movie got wrong. That rock message on that planet and the last line in the book mixed so well that I dropped some tears.
Now to the brain crunching. The future data stream stuff just wrecked my brain in a good way. I was thinking about it during reading breaks and it was so hard to stay sane. Not being able to think of new ideas because it would have been sent back was just soooo good! It is the kind of fundamental flaw in the system, that makes the system not fun to use and doesn't solve the questions about the life, the universe and everything.
The return was handled so well. It was a nice end to the trilogy but it left the universe so wide open that my mind is still racing and trying to generate more to the story.
Some thoughts:
*Photonic electronics was a cool alternative to conventional electronics
*I forgot how magical the traveler technology had become until they looked at the rockets engines in the end
*The gender mixing was a cool solution/thing that happens in most Egan books hahaa
*I thought from the beginning, that the mountain was the Hurtlers and it was looping around the universe or going back and forth in time... Well some of it I got right haha
*These books had a lot more "story" in them than my previous encounters with Egans books. I still love Diaspora and Permutation City to bits but this trilogy was something else. It has history and more of a world than the other books. I don't mean that the others didn't, but this trilogy had more(?) of it and it felt great.
May 27, 2017
In this, the third book of the trilogy, Egan has chosen a slightly different course from the one in the previous books. Having already set up the scientific background, it is time to really explore the meaning of one of the most intriguing elements of his universe, the capability to have a different time line than your surrounding. This provides a way to see into the future, an exciting possibility. Combine this with the continuing conflicts caused by the biology and society Egan dreamed up and you get quite a number of interesting subjects. So what changed? To my relief, Egan has chosen to use the plot to explore these aspects.
One thing I did not like in the previous books was the "classroom sessions" in which the rules of the universe were discovered by the characters, and thus relayed to us. While this was somewhat intellectually challenging, it is not good story telling. I was left admiring the author's imagination, but wishing that he had a better way to convey it. I'm happy to say there are no more any such sessions in this book. If there is any rule of nature we were still not taught, we will have to discover it from the story. Don't get me wrong, some aspects are not much simpler to understand, but at least there is plot behind them. And while Egan's style remains somewhat dry, his characters remain a bit single-minded, and his plot is pretty straight forward, the story telling is served by the science, rather than being its slave. I enjoyed reading this book more than the previous ones.
The one thing that really did not work is the ending. Saying it is anticlimactic is an understatement. I was really looking forward to see how the Peerless saves home planet. I was also waiting for the conflict between the two societies, twelve generations apart. Instead, we get nine pages which tell us nothing. It's hard to believe, writing a thousand pages, and then spending so little on the ending. From the point of view of the readers, after a thousand pages we deserve more. The book up to that point is worth four stars, but the ending is so disappointing, I'm rating it three stars out of five.
One thing I did not like in the previous books was the "classroom sessions" in which the rules of the universe were discovered by the characters, and thus relayed to us. While this was somewhat intellectually challenging, it is not good story telling. I was left admiring the author's imagination, but wishing that he had a better way to convey it. I'm happy to say there are no more any such sessions in this book. If there is any rule of nature we were still not taught, we will have to discover it from the story. Don't get me wrong, some aspects are not much simpler to understand, but at least there is plot behind them. And while Egan's style remains somewhat dry, his characters remain a bit single-minded, and his plot is pretty straight forward, the story telling is served by the science, rather than being its slave. I enjoyed reading this book more than the previous ones.
The one thing that really did not work is the ending. Saying it is anticlimactic is an understatement. I was really looking forward to see how the Peerless saves home planet. I was also waiting for the conflict between the two societies, twelve generations apart. Instead, we get nine pages which tell us nothing. It's hard to believe, writing a thousand pages, and then spending so little on the ending. From the point of view of the readers, after a thousand pages we deserve more. The book up to that point is worth four stars, but the ending is so disappointing, I'm rating it three stars out of five.
August 7, 2024
Unsurprisingly, this was absolutely brilliant.
September 28, 2019
I'd say this is the weakest of the trilogy (for me), but there are still lots of good concepts at play. The political themes shift to more mundane power politics, but the scifi hook becomes time and the physics of predestination. I'll admit I didn't understand a lot of the technicalities, and like the first book skipped a lot of the alternate physics discussions, but this sums up the ideas at play:
This book sort of forgets about scarcity of resources and the implications of a generation ship, and instead focuses on the story it wants to tell. That's fine, it's earned a break.
It took a long time to get through the climax, and what I thought was felt a little too pat. But the final resolution of the problem the ship set out to remedy certainly was dramatic.
All he could do was keep following that path, and hope that the footprints in the dust ahead really were his own.
This book sort of forgets about scarcity of resources and the implications of a generation ship, and instead focuses on the story it wants to tell. That's fine, it's earned a break.
After geology, he was going to have to add time-reversed archaeology to the list of disciplines he'd sadly neglected.
It took a long time to get through the climax, and what I thought was felt a little too pat. But the final resolution of the problem the ship set out to remedy certainly was dramatic.
April 1, 2021
The hardest of hard sci-fi trilogies comes to an end.
Egan's Orthogonal series follows the tradition of taking actual physics and then building stories and plots around them. But it comes with a twist: It's not *actual* physics that Egan assumes. Rather, he takes the laws of physics and tweaks one law of nature: where, in our universe, spatiotemporal separation is determined by a function of spatial distances minus temporal distance, in this world spatiotemporal separation is determined by a function of spatial distance *plus* temporal distance. He then follows through all the ramifications of that and the weird world one ends up with. (Hint: If you don't really follow what I've just said, I'm not entirely sure this is the novel for you!)
In this book, the main theme is time reversibility. And I adore it. The plotting is excellent, and it turns out Egan's physics better showcases time reversibility than our own physics!
The story itself, and the characters themselves, are pretty good, but it's the exploration of this fantastical world where all the genius lies. Recommend, but probably to a select audience.
Egan's Orthogonal series follows the tradition of taking actual physics and then building stories and plots around them. But it comes with a twist: It's not *actual* physics that Egan assumes. Rather, he takes the laws of physics and tweaks one law of nature: where, in our universe, spatiotemporal separation is determined by a function of spatial distances minus temporal distance, in this world spatiotemporal separation is determined by a function of spatial distance *plus* temporal distance. He then follows through all the ramifications of that and the weird world one ends up with. (Hint: If you don't really follow what I've just said, I'm not entirely sure this is the novel for you!)
In this book, the main theme is time reversibility. And I adore it. The plotting is excellent, and it turns out Egan's physics better showcases time reversibility than our own physics!
The story itself, and the characters themselves, are pretty good, but it's the exploration of this fantastical world where all the genius lies. Recommend, but probably to a select audience.
February 2, 2019
I recently read "Dichronauts". This reminded me that I didn't notice when "Arrows of Time" came out and didn't complete that trilogy.
Like the first two books, there is a lot of physics and math. There was also an assumption that you remembered things from the first two books. I had to do some googling to catch up . Tip: Don't wait 4+ years between books.
This story was a good ending though. It explores a new technology that involves messaging across time. The central idea is that the endpoints are fixed, but not the middle. The politics is also well explored.
They took a side trip to a place where time runs backwards. This was confusing but interesting. The confusing part is that the visitors still see time in our direction. It's no more confusing than the anti-matter of course.
The characters were good. It was easy to forget they weren't human (until they talked about mating or drawing on their chests)
And of course, it was interesting to see how they solved the original problem of the Hurtlers.
Like the first two books, there is a lot of physics and math. There was also an assumption that you remembered things from the first two books. I had to do some googling to catch up . Tip: Don't wait 4+ years between books.
This story was a good ending though. It explores a new technology that involves messaging across time. The central idea is that the endpoints are fixed, but not the middle. The politics is also well explored.
They took a side trip to a place where time runs backwards. This was confusing but interesting. The confusing part is that the visitors still see time in our direction. It's no more confusing than the anti-matter of course.
The characters were good. It was easy to forget they weren't human (until they talked about mating or drawing on their chests)
And of course, it was interesting to see how they solved the original problem of the Hurtlers.
This entire review has been hidden because of spoilers.
September 18, 2021
I mean just when you think, how can this get any more wonderfully geekily amazing... For weeks after I felt like those people who were homesick for Pandora after seeing Avatar. I read these at the library, where I get 99% of my books, but I'm sorely tempted to buy a set of these and start evangelising to my (mostly astrophysicist) friends about their virtues. Brilliant, would read again!
January 1, 2022
Great end to the trilogy.
Great end to the book.
Great resolution of all the conflicts, scientific, cultural and political.
Above average characters, great characters for sci fi!
I like that the villain characters, you see their motivation and at times you even root for them.
Greg Egan is a master and helping readers to see things from different perspectives! If there was a way for more people to read these novels (adaptations with less science?) the world would benefit from the social, gender, cultural and political conflicts and resolutions in all his novels.
Of his short stories I really liked Oceanic.
Of his novels (I have not finished them all yet) I liked this one most, then:
Dichronauts
Incandescence
Zendegi
Great end to the book.
Great resolution of all the conflicts, scientific, cultural and political.
Above average characters, great characters for sci fi!
I like that the villain characters, you see their motivation and at times you even root for them.
Greg Egan is a master and helping readers to see things from different perspectives! If there was a way for more people to read these novels (adaptations with less science?) the world would benefit from the social, gender, cultural and political conflicts and resolutions in all his novels.
Of his short stories I really liked Oceanic.
Of his novels (I have not finished them all yet) I liked this one most, then:
Dichronauts
Incandescence
Zendegi
July 19, 2022
How can you describe an entity more intelligent than you are? You can only fake it with imagination, but for most of us mere mortals trying to understand Greg Egans novels is as close a we will ever get to listening to a super intelligent alien or AGI. I’m not dumb but am definitely not smart enough to understand what the hell he is daring to conceive of this time. Regardless I absolutely love reading it and can never get enough. It doesn’t matter to me whether it actually makes sense to a fellow genius, I’m convinced and you probably will be too. Proper Maths and physics nerds might argue but there are very few sf authors that can even conceive of anything this weird.
December 14, 2023
No real details, but spoilering it because you could glean something of the trajectory from it.
This is quite a good science fiction novel by itself, but it isn't by itself. It's the third in a trilogy.
This is quite a good science fiction novel by itself, but it isn't by itself. It's the third in a trilogy.
May 26, 2023
Egan wraps up his Orthogonal series with more charts and lectures, and a slightly less convincing political crisis than in some of the other installments. On the other hand, the section in which a group of explorers travel to a planet whose time direction is opposite their own ... functionally, running backwards ... is completely mind-bending and worth the read.
The concluding section is a bit brief, but does wrap up the storyline and resolve the initial conflict in a reasonably satisfactory way.
The concluding section is a bit brief, but does wrap up the storyline and resolve the initial conflict in a reasonably satisfactory way.
September 30, 2024
Very much not a typical Egan. It's like he was challenged to write characters, and did, resulting in a slower trilogy rather than his usual sort, dense novels. And the characters aren't human, either. They're not even really described. They're aliens from another universe with profoundly different physics.
Very weird trilogy. Had its moments and die done interesting stuff, but it was slow going and quite hard work.
Very weird trilogy. Had its moments and die done interesting stuff, but it was slow going and quite hard work.
April 28, 2020
Incomprehensible. Although in fairness, the author warns us to read the first two books in the series first. But even so, I went to the appendix in the back where it lists 50 categories and subcategories of time and distance. There are so few (none) links with our current base of knowledge. Might as well give me a story written with ancient hieroglyphs.
December 14, 2017
A fitting and proper conclusion, filled with more of that alternate universe scientific discovery process that I’ve come to expect and enjoy. Some twists and turns add narrative interest, and the extent to which Egan carries one simple idea to as many implications as he can is staggering.
July 16, 2018
This was so incredibly brain-bendy. I can't even imagine the amount of effort went into writing it and making sure everything was consistent with the wonky physics. This series is definitely worth a read!
January 11, 2021
The only thing that's managed to convey an intuition for compatibilism for me: how determinism may not be at odds with free will. I can't say more, or it'll spoil the story. Do read it. The final sentence manages to tie things up perfectly.
July 14, 2024
I can't. I just can't. The geometry of the spacetime in this book is just breaking my head. Lovely story, wonderful concept, but I have to stop. I was able to handle Mr. Egan's other works but this one has done me in.
January 22, 2025
A good cap to a great trilogy. I liked the interaction between the two worlds with opposite time arrows. And the dystopian horror created by the messaging system. But I think I've found my limit for sci-fi "hardness" with this series.
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