Who are the San-Ti in The Three-Body Problem?
The San-Ti are the alien civilization at the center of the story — the same beings the English novels call the Trisolarans. Netflix simply chose a different name. "San-Ti" is a direct transliteration of the Chinese title 三体 (pinyin: sān tǐ, literally "three-body"), while translator Ken Liu coined "Trisolaran" from tri- (three) plus solar (sun). Both names point to one civilization, one home planet, and one invasion. If you have been confused by the two labels, they are interchangeable — the show uses San-Ti, the books use Trisolarans. For a fuller map of what else changed between versions, the Netflix versus book changes breakdown walks through it line by line.
Why is their planet called "three-body"?
Because the San-Ti home world orbits a system of three suns — the show places it at Alpha Centauri, roughly four light-years away. Three stars pulling on each other produce orbits that cannot be predicted by any formula, which is the real astronomy behind the famous unsolvable three-body problem.
For the San-Ti this is not abstract math but daily survival. When the three suns happen to hold their planet at a livable temperature, they call it a Stable Era. When the planet is flung too far or too close, temperatures crash or soar into extinction range — a Chaotic Era. Crucially, neither can be forecast, which is why their entire psychology is built around unpredictable catastrophe.
How do the San-Ti survive their own planet?
They dehydrate. When a Chaotic Era makes the surface unlivable, a San-Ti can expel all the water from its body, collapse into a dry fibrous roll, and wait in that dormant state until a Stable Era returns and someone rehydrates it. This dehydration-rehydration cycle is what lets their civilization persist through disasters that would wipe out a normal species — the mechanics are covered in the Trisolaran dehydration ability explainer.
Even so, their civilization has been destroyed and rebuilt close to two hundred times. That running tally of collapse and rebirth, tracked in how many times Trisolaran civilization was destroyed, is what forged a culture that is cold, hyper-collective, and stripped of individual sentiment — a temperament explored further in the Trisolaran society and culture profile.
Why do the San-Ti want Earth?
Earth has a single, stable sun. To a civilization tormented across countless eras by three chaotic suns, a world where the Stable Era never ends is paradise. That is the entire motive: they want a home that will not try to kill them.
The invasion is triggered when Ye Wenjie beams a signal into space from the Red Coast base. The San-Ti lock onto Earth's coordinates and launch a fleet that travels at about one percent of light speed — a journey of more than four centuries, detailed in how long until the Trisolarans reach Earth.
There is one more reason the San-Ti both need and fear humanity: their thoughts are completely transparent. Communication is thought, so their species has no concept of deception. When they discover that humans can lie, disguise intent, and plan strategic deception, they grow genuinely afraid — the seed of the whole cosmic standoff to come. Why the San-Ti cannot lie, and how badly that shapes the war, is unpacked in why Trisolarans can't lie, and the suspicion that grows between the two worlds ultimately points to the core idea of the entire trilogy: the dark forest theory.