Book review: Death's End by Cixin Liu

This review contains lots of spoilers. DO NOT READ THIS REVIEW UNLESS YOU’VE ALREADY READ THE BOOK.

Death’s End by Cixin Liu is just WILD. I have no words to describe it. It is one of the best sci-fi I’ve ever read, although maybe “space fiction” is a better description for this book. It really takes you places and there is so much content in it.

This book explores a wide range of sci-fi topics like hibernation, dimensionality, light speed travel etc. The author attempts to ground the fiction with scientific explanations early on, but some of the more extreme elements introduced near the end of the book are left unexplained. This book really plays fast and loose with science at times. Ideas like “creating a mini universe on top of the supermembrane” and “Edenic universe with 11 dimensions and infinite speed of light” sound more fantasy than sci-fi. This lack of explanation is forgivable, however, as these concepts are meant to be beyond human understanding.

Most of the book is just:

• Be Cheng Xin
• Wake up
• Change the world
• Go back to hibernation
• Refuse to elaborate

It felt unrealistic how Cheng Xin is a part of every significant event in this world. I understand that she is the protagonist and thus we see the world through her eyes. But the plotline that puts her in these important positions is weak. For instance, why was she — a seemingly random woman from the Crisis era — nominated to be a Swordholder candidate? Another thing that felt unrealistic was the importance given to Crisis Era characters. Even hundreds of years into the future, after the world has undergone so much change, apparently people from our time are still some of the most important in the world.

This book is very good at making you feel insignificant — especially near the end when we read about civilizations that are more powerful than we can comprehend. Don’t read it when you’ve got a lot of work to do as it will ruin your mood.

It’s interesting that the Black domain project was introduced as humanity’s only hope at survival. But we see that spaceships Gravity and Blue space turned out to be much better at surviving than Black domain or curvature propulsion or anything else. Turns out, all humans needed to do was to spread out in the universe (even at sub-light speeds). We know that “galactic humans” survived long enough and were significant enough to be included in the “returners message”. Is this a plot hole? I’m not entirely sure.

Now a couple of questions regarding the “Dark Forest theory”. The universe is a dark forest because of two reasons:

• Chains of suspicion
• Technological explosion

Both of these reasons only exist because of the finite (and relatively small) nature of the speed of light. If speed of light was infinite (as claimed to have been in the “Edenic universe”), these reasons don’t hold up. Let me explain.

Chains of suspicion: Because the distance between stars is large, it is always safer to get rid of another civilization first before they get rid of you. But if speed of light is infinite, it is possible to observe every other star system in real time. This leads to something that I call the “inverse Dark Forest theory”. Since you may be under observation by millions of other civilizations at any given time, you are encouraged to appear as safe as possible to the rest of the universe. The most dangerous thing for any civilization to do would be to attempt to build weapons that can destroy other civilizations.

It gets even more interesting. What’s the best way to appear safe to the rest of the universe? Reducing the speed of light around your star system. Perhaps the light speed reduction in the universe happened because many civilizations built black domains to show that they are safe to the rest of the universe, and these black domains spread throughout the universe.

Technological explosion: You can never be sure that just because another civilization isn’t a threat to you now, it won’t be a threat to you soon. This also doesn’t hold up under infinite speed of light because:

• Civilizations can be under constant surveillance
• Projectiles can be launched at near-infinite speed

For now, I’m going to ignore all the physics that breaks when speed of light is infinite. One small example: Nuclear fusion/fission releases infinite energy. A single atom contains enough energy to destroy the whole universe (which just doesn’t make any sense).

Another thing that I found interesting was the existence of these “returners”. The mere existence of such a civilization questions the “dark forest theory”. We don’t know if it is one single civilization or a group of civilizations acting in collaboration. Either way, it is interesting to see cooperation at such scales in the universe despite its Dark-Forest nature. How can there be collaboration without trust? And how can there be trust between star systems in a Dark-Forest universe? So maybe the returners found a solution to the Dark Forest theory. Perhaps the author meant this as a symbol of hope for the universe.

This book is very long, and it can be a chore to read at times. But it is definitely worth finishing.