In Cixin Liu’s Death’s End (i.e. the final book of the Three-Body Problem series, AKA Remembrance of Earth’s Past), a central element of the story is a set of “fairy tales” packed with secrets. Despite the crucial importance of these, and despite much discussion and even controversy online, I was unable to find a straightforward summary and discussion of their hidden meanings in the context of the story — only scattered Reddit threads and handful of superficial treatments. So I’m putting one here.
Warning: Major spoilers ahead. Do not read this unless you have finished the books! Also, these are all just my opinion or theories I’ve read.
The fairy tales (really, one tale in three parts) told by Yun Tianming concern the royal family of the Storyless Kingdom, a name which we’ll come back to later. I’ll forgo a summary and assume the reader of this piece has read the original.
First, I think it is worth saying that the tale is worth reading; there are comments saying it tried their patience or that they skipped it because it wasn’t really sci-fi. That is misguided — it is entirely relevant and appropriate to the story. Also, the oft-mentioned criticism that Liu pats himself on the back with the note that “as fairy tales, these are very good” is likewise I think missing the point — do we really expect an author who ranks among the first in the world in popularity and critical reception to needlessly praise his own work? The point is made by the people in the book, who are introduced as non-specialists, that these are in fact well made fairy tales, put together with care, not just some thrown-together thing to carry a secret message.
As to the content of the tale itself, it is with hindsight a fairly clear description of the history of the galaxy, the Dark Forest in which humanity lives, and some ways of existing within it or, potentially, escaping it altogether.
How the dark forest grew
The description of the galaxy is found in the name of the kingdom and in the story of the Glutton’s Sea. Long ago, many civilizations of the galaxy were far apart but in communication and peace with one another, even those of vastly different advancement levels. But as more “low-entropy entities,” as Singer would put it, appeared, strife in the form of existential-scale attacks (sun-destroying photoids and dimensional weapons) became more common, until self-obfuscation and preemptive annihilation became the ironclad rule. “Hide yourself well; cleanse well,” quoth Singer.
Now, every inch of the galaxy (and perhaps beyond) is teeming with these omnivorous, xenophobic glutton fish: entities which, quite sensibly, refuse to allow others to exist, attacking and destroying them on sight. This is how the galaxy became a dark forest, and how the Storyful Kingdom became the Storyless Kingdom. The complexity and diversity (dimensional and otherwise) of the early universe gave way to isolated islands like the story’s setting, which is a stand-in for all non-spacefaring civilizations. Bordered by an empty, silent sea of stars and without commerce with advanced civilizations (i.e. He’ershingenmosiken), they believe themselves alone and as a result develop slowly if at all.
But while these nascent civilizations are isolated from others by the huge distances of space, they are not protected from them. The apparent peace and quiet of the dark forest, like the conspicuously empty sea, is the result of enormous and omnipresent danger.
The threat of dimensional attacks
The specific threat of the dimension-based weapon is explained in Needle-Eye. The reduction of a person to a hypnotically detailed 2D plane occurs both in the story and at the end of the book, when humanity rather memorably meets this painterly fate.
We already saw this occurring with the 4D space being reduced to 3D, though the beings within were a bit cryptic about it. We are meant to understand that the reduction of one space to a lower-dimension space is, unless done carefully and deliberately, inevitably fatal.
The terrifyingly casual destruction of the solar system and human race by Singer is done with a piece of 2D space that has been packaged up for use as a weapon. The snow-wave paper and special obsidian blocks are, I think, non-specific but hint at the technology required to manipulate lower-dimensional space the way Singer’s civilization does. In fact, the actual article of attack (a softly glowing white “sheet of paper”) is described in the story quite clearly!
Interestingly, Tianming does not so much as mention a “photoid” or any other form of destruction. It is possible he already understands that the solar system would be best cleansed using the 2D method.
The need to view the victim, as Needle-Eye does, is not specific to the 2D attack, but rather indicative of Singer’s “great law of reversible discovery”: if you can see someone, they can see you, and being perceived is essentially to be given a death warrant. It comes down, as Needle-Eye says, to who paints whom first. We saw a small-scale version of this quick-draw challenge in the human ships that attack one another earlier; in that case it came down to the second.
Traversing the Glutton’s Sea
In the story, the glutton fish are placated by the weightless soap and its plentiful bubbles. This is a rather fanciful representation of the opportunity and danger of lightspeed travel.
The “curvature drive” developed later by humanity and apparently quite recently by the Trisolarans is represented by the special soap. Though the exact methods are left to the imagination, there are clear references to frames of reference in how the bubbles making it up are to be caught — by going the same speed as them. We see this echoed in the methods of travel used by the Trisolarans, who must collect enough of some unknown resource in order to accelerate further.
These bubbles burst forth again in use (echoing the soapy-surface-tension method method of propelling a toy boat) producing a highly visible wake: “the sea seemed to suddenly be inhabited by a long-tailed comet.” This is the warning regarding its use. But the foam also stops the attackers cold, in reality because the “slow fog” lowers the speed of light.
Tianming, no doubt to avoid the detection of his ruse, was not explicit about how these two things could be combined to humanity’s benefit — the obvious in-story action of using the rest of the soap to fill the sea around the island with foam would likely too closely resemble the truth. But if humanity had thought a little harder, they might have realized that completely surrounding the solar system with slow fog would be both camouflage and a statement of non-aggression.
Singer actually wonders why this hasn’t happened yet before cleansing the system — the answer, we may speculate, is that this would have been the course taken by the implacable Wade, who was pursuing this technology and likely would have spotted this opportunity. As Cheng Xin points out, his gambits tended to pay off, as indeed the one with Tianming did. (I will leave the analysis of that to others, but it seems like Liu endorses the fantasy of a ruthless genius as leader, at least in such dire circumstances.)
Defending against strikes
In the story, there are two ways to prevent being painted, which refer to two ways of preventing reduction to lower dimensions.
One is the magic umbrella, which must be spun at the right speed; the other is Prince Deep Water’s quality of not respecting frames of reference. These are not so easy to pin down.
The umbrella may refer to a technology that counteracts a dimension-lowering attack, possibly (as some have speculated) the solar-scale particle accelerator. It’s not much to go on, frankly, and it’s not surprising no one has taken this hint to the finish line. The way it’s described also suggests the umbrella is not easily made — I doubt humanity would survive finding out what the real-life equivalent of the story’s “Abyss Dragon” is.
It’s also possible that the carefully speed-regulated umbrella is a reference to using the slow fog to adjust the local speed of light to a happy medium where it doesn’t escape but also doesn’t interfere with everyday physics.
The Prince’s failure to grow or shrink as you change distance is, I believe, a reference to higher dimensionality. “No matter how far away he is, he looks the same size in our eyes,” says Captain Long-Sail. It’s not quite how a four-dimensional being or reference frame would work, but it gets one thinking, right? If we as 3D beings could be “above” a 2D plane and no matter how they moved, we did not change size, something similar might be the case for the dimension “above” us.
This was described with partial success in another story-within-a-story, the 15th-century “magician” in the first chapter, and later the encroachment of 4-dimensional space on our own space when the ship is investigating the 4D “tomb” collapsing into 3D and presaging a similar end for all of us. It’s hard to describe 4D space, so let’s not criticize Liu’s attempt.
As Needle-Eye complains in the story, the Prince doesn’t obey the laws of perspective, by which I believe he means that higher-dimensional beings and spaces don’t follow the same physical laws as we do, or at least not in the same way. Reducing a 4D thing to 3D is necessarily destructive and incomplete; to sublimate it, as it were, to 2D is impossible or close to it. (Though, as the duel between the brothers shows, it is trivial for a higher dimension to interfere with a lower one.)
But it’s unclear what Tianming is advising here. As we have seen, changing dimensions is unidirectional; you can only go down. What use is it to know that you can resist a 2D attack by being 4D? If it were that easy to ascend dimensionality, everyone would be doing it.
This is perhaps why some support another interpretation, that the Prince’s constant size represents the speed of light, c, which although it goes up and down in relative frames of reference, never actually changes. And as the expedition that is “the first to be painted into this grand painting of annihilation” discovers (and others put to use), the escape velocity from an encroaching 2D space is the speed of light.
A third possibility is that the Prince’s anomaly represents spaces outside space, the pocket universes in which many denizens of the galaxy take refuge as things decline “outside.” Though this ends up being a common solution to the problem of a collapsing universe (to the point where some godlike beings need to step in), it doesn’t really map onto Prince Deep Water as much as I’d like — except of course that he literally lives on Tomb Island, and the 4D beings call their enclosure a tomb. However, the extradimensional spaces and the tombs appear to be distinct concepts.
At any rate, others have pointed out that none of the metaphors are exact, so this interpretation could be correct. Perhaps the story is even ambiguous in service of those multiple possibilities.
Other characters and concepts
Princess Dewdrop herself is — like many of the women in the series, unfortunately — mainly just a pretty thing that the men around her want to protect. She does in this case I think represent not just Cheng Xin but the innocent masses of humanity, and the impulse towards wonder and exploration that once dominated the cosmos.
Some have suggested that “Auntie Wide” is some kind of reference to antimatter, but that is probably just coincidence owing to the English “auntie” — I don’t think her name suggests this in the original Chinese. However, there may be some significance to the numerous dimensions used in names. Long, Wide, and Deep are all good guys. Perhaps it is just Tianming’s way of saying he hopes the 3D universe will live on.
Ice Sand and Needle-Eye are, I think, not representative of anything in particular in their names or persons. Every story needs a villain and it wouldn’t make much sense if the paintings painted themselves.
The suggestion that Cheng Xin and Yun Tianming meet up at “their” star, combined with the fact that Princess Dewdrop leaves with Long-Sail — who in no way resembles Tianming — has caused some to suggest some timey-wimey action here that I don’t think holds water, essentially that Tianming is broadcasting from a future in which he has already witnessed the 2D attack. It’s a compelling thought but I just don’t think Liu intended that to be the case.
I suspect that, instead, he was setting up Tianming as a romantic realist, who would (and does) try to cross the galaxy to meet up with his crush — but, knowing how slim the chances were of success, he suggested that she go with someone she loves even if that’s not him. It’s a bit tragic, and I’ll also put here my own personal disappointment that Liu decided to punish his characters so needlessly and severely at the end; I don’t think it was necessary to rob these two characters of their moment together, it added nothing and didn’t really happen for any particular reason. The two couples could have easily swapped partners before the events occurred, and it would have been merely bittersweet rather than simply cruel.
Liu’s fairy tales are, in my opinion, a really wonderful thing to insert into this hard sci-fi series that can at times feel dry or mechanistic. The stories themselves are (as Liu’s own expert testifies) good on their own, and the fact that they include so much hidden information at the same time really speaks to the author’s ingenuity. That said, there are also a fair number of elements that are left unexplained, surely on purpose — you wouldn’t want him to explain literally everything, would you?