Nightmare Fuel / Remembrance of Earth's Past

We are not alone in this universe, unfortunately.

No spoiler warnings ahead!

General

• The entire trilogy manages to be a Cosmic Horror Story without resorting to using any kind of supernatural plot point or element. Just applied physics and the law of the jungle taken to its final, logical, horrifying conclusion. Cixin Liu did not make a Crapsack World. He made a Crapsack universe.
• Scary Dogmatic Aliens are the only kind of aliens in existence just on the principle that nobody knows who is friend or foe, a hostile race could make a technological breakthrough in the blink of an eye and the distance between worlds is simply far too vast for any kind of diplomacy to be practical. The only way an alien race can guarantee its own survival is to make sure that they're the only one alive. Worst of all? It's a theory that is taken seriously by real-world scientists.
• Just the idea of humanity facing a Hopeless War with a species that can turn off the cosmic microwave background at will! Okay, they can't actually do that, but they can fake it, which is still bloody impressive.

The Three Body Problem

• Trisolaris. Its chaotic orbit around Alpha Centauri has destroyed over two hundred civilizations over the eons, some in pretty horrific ways. It's so much of a hellhole that the Trisolaran government has purged nearly all forms of cultural expression, recreation, ethics or values that don't contribute to their continued existence. All in the name of survival. The moment a Trisolaran is incapable of working is the moment they are forcibly dehydrated and thrown in the incinerator.
• Sophons. Massive supercomputers that have been folded into lower and lower dimensions until they are no larger than a subatomic particle. They are capable of screwing with scientific data and observations, can communicate with the ETO in real-time and spy on their enemies without being detected, obstructed or subverted.
• The advanced VR MMORPG, "3-Body", which allows people from all over the world to take part in building a civilization on a world with three suns. However, because of the planet's truly unpredictable orbit - known in science as the three-body problem - nobody knows if it will be a "Stable Era" (where the environment is nominal for human life) or a "Chaotic Era" (where everyone exposed will either freeze or burn to death). And nobody knows how long those eras will last, either. And it's used as a recruitment tool by the Earth-Trisolaris Organization.
  • In one instance, the combined gravitational pull of the three stars caused everything on the surface to literally fall into the sky. This is described in very graphic detail as witnessed by Wang.
  • Another civilization is destroyed by a close pass to one of the suns, which literally rips the planet in half and kills virtually every living thing on it.
• In 3-Body, players - like the Trisolarans - will have their bodies dehydrated and stored in towers so they can survive a Chaotic Era. When in a Stable Era, players logging on will toss the skins into a lake where they would come back to normal. One poor bastard is resurrected, only to lose a finger because a rat gnawed on his skin while it was in storage (which makes you wonder where the rat came from if dehydration is the only way to survive the lethal environmental conditions).
• The Earth-Trisolaris Organization was founded on the belief that Humanity is doomed to die by industrialization and that only the Trisolarans can save their civilization. In practice however, the group is divided into two ideological factions: The Redemptionists, who see the Trisolarans as veritable gods and the Adventists, who believe that Humanity is inherently evil and deserves to die.
• The Judgement Day, ETO's oil-tanker-turned-headquarters, gets screwed over by the Sino-American coalition in the Panama Canal. Da Shi formulated a plan to stretch a net of hair-thin nanomaterial across the canal so their forces can kill its crew without them having enough time to destroy the files they have on Trisolaris. It worked.
  • In the animated book trailer, one of the victims is a seagull.
• One of the Trisolarans' experiments in dimensional folding ends up with the Sophon producing a parabolic mirror by proxy that almost incinerates their capital. This is due to the Trisolarans alerting a 2D Species of their presence, the 2D beings presumably being terrified of these (would-be) invaders. The response is a pre-emptive attack, as the species (resembling a collection of floating eyes) manifest in the 3rd dimension above the skies of Trisolaris and merge into said parabolic mirror. The connection to the 2D Plane deactivates just in time to avoid doing turning the main plaza into slag... and saves the leader of their science division from his own fiery fate.

The Dark Forest

• The droplet, a Trisolaran probe initially believed to be harmless, and its effortless massacre of mankind's entire space-based military. It is Made of Indestructium and simply plows through everything in its way, and it moves so fast that hundreds of ships are already destroyed by the time anyone manages to work out what's going on. Two ships try to flee the slaughter by accelerating away before their crews are prepared, gruesomely killing everyone aboard, in a desperate attempt to make sure that not every ship is destroyed. They're still not fast enough.
  • One line, as the droplet approaches the warship Infinite Frontier, make it very clear just how out of its depth the fleet is:
    In the roughly two seconds it took to cover that distance, the computer actually dropped its alert from level two back to level three, concluding that the fragment wasn't actually a physical object due to the fact that its motion was impossible under aerospace mechanics.
• The Dark Forest theory. Space is big, but it's finite and there's only so many resources to go around. Any Sufficiently Advanced Alien could colonize every single star in the Milky Way in less than a million years and take all those resources for themselves. What's more, the inevitable differences between other species means communication as a whole would be difficult, never mind the idea that you could tell if they're being entirely truthful, and with how fast technology progresses, you simply can't trust any other species enough to work with them. The solution? Kill anyone else you come across. Aliens Are Bastards by necessity.
  "The universe is a dark forest. Every civilization is an armed hunter stalking through the trees like a ghost, gently pushing aside branches that block the path and trying to tread without sound. Even breathing is done with care. The hunter has to be careful, because everywhere in the forest are stealthy hunters like him. If he finds other life — another hunter, an angel or a demon, a delicate infant or a tottering old man, a fairy or a demigod — there's only one thing he can do: open fire and eliminate them. In this forest, hell is other people. An eternal threat that any life that exposes its own existence will be swiftly wiped out. This is the picture of cosmic civilization. It's the explanation for the Fermi Paradox."
• Luo Ji, a member of the Wallfacer project, is this to the Trisolarans.
  • To study the Dark Forest Theory, Luo Ji decides to demonstrate what he calls a spell. He slingshots a broadcast around the sun that describes the location of 187J3X1, a (hopefully) lifeless star system located 50 light-years from Earth, to much of the surrounding cosmos. When he awakens two centuries later, he gets the word: nothing but a nebula of debris remains where 187J3X1 used to be, and it was too small and stable to go nova naturally.
  • And with that proof of concept, knowing he's being monitored by the Trisolarans, Luo Ji calls out to them. He reveals that there are 3,614 oil-filed bombs in precise orbits around the sun- a plan from another Wallfacer- whose trigger mechanisms are tied to a dead man's switch. If he dies, the bombs will detonate, creating huge dust clouds that will cause the sun to flicker in code, transmitting the location of Trisolaris and, by proxy, Earth. His ultimatum is simple: call off the invasion or he shoots himself, dooming both civilizations to extinction.
  • And according to later observations from Deterrence Game Theory, his odds of doing so were between 91.9%-98.4%.

Death's End

• The Trisolarans' plan for Earth. While they promise not to completely exterminate humanity when they take over, they'll strip them of all heavy industry, agriculture and weapons. They'll also turn Australia and a third of Mars into reservations where humanity can live, but with the catch that they all need to move within a year before the fleet's arrival, or they'll be considered invaders and killed on sight.
  • When it's made clear that four billion people living in Australia without any industry or agriculture will starve very quickly. Sophon remarks that they'll have plenty of food, and that the population should stabilize at around 50 million. Cheerfully, she remarks that all the people she's talking to will be among the survivors. It takes a broadcast from the crews of the ships Gravity and Blue Space to prevent it from being fully carried out.
• The destruction of Alpha Centauri. Much like 187J3X1, one of the stars is ripped apart by a photoid projectile. The resulting explosion shines so brightly that, on the night side of the Earth, it looks like a second sun for about half an hour. Trisolaris is caught in the blast and the entire planet is melted, annihilating what had been humanity's biggest threat for centuries. Of course, what replaces it is a darker and even more powerful universe full of hostile civilizations. And because Earth broadcasted the location of Trisolaris to the rest of the Universe to launch a Dark Forest attack on them, the rest of the Universe now knows that Life exists on Earth.
• The slip of paper puts the droplet to shame. It's a tiny, pure white thing that looks like a slip of paper, completely invisible save for its gravitational waves, and which that passes through everything it touches. The ship Revelation lets it onboard to study it and, at first, it's a mild amusement to the people aboard and even a nostalgic look back from this No-Paper Future. And then the Revelation's pinnace starts to melt. The object turns out to be an extragalactic dimensional superweapon, and as Revelation and her sister ships try to peel out, space itself starts to collapse toward it and cancel their motion. The ships are collapsed into two-dimensional space, which soon grows to engulf the entire solar system, killing every living thing.
• The concept of Dimension-Shifting. Guan Yifan speculates that the universe was originally composed of ten dimensions and the speed of light was near-infinite. Yet even back then, the Dark Forest way of thinking was in full force, and the species of that era found a way to permanently end any and all threats to themselves: weaponizing the very laws of physics. Over billions of years, they gradually collapsed the universe down from ten dimensions to three and lowered the speed of light to what it is now. And after engineering themselves to survive in lower dimensions, their plan is to continue collapsing the universe until there's nobody else left.
  • For a moment, Yifan also speculates that maybe every law of physics has been weaponized somewhere in the universe, including the very foundations of mathematics. Cheng Xin can't even fathom it.

Redemption of Time

• The revelation that the Trisolarans are the size of rice grains. Imagine humanity's death warrant being signed by a spacefaring race that is no bigger than an ant.

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