this post was submitted on 07 Aug 2025
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No, they're not just trying to find an equation, which may not be possible. They say it's impossible to predict where the objects will be in the near term, which is nonsense.
The three-body problem doesn't say it's unpredictable, just that there is no universal equation to describe it. You can still determine where things will be with a high degree of probability with iteration. The earth, sun, and moon are a three-body problem but we know where they will be tomorrow, next year, next century, next millennium, etc. The error bars increase with time but the moon isn't suddenly going to be ejected beyond the orbit of Pluto in an unpredictable way due to some bullshit from the chaos of the three-body problem. The entire solar system is a (very large number)-body problem, but we know where every major body is going to be with a large degree of certainty for a long time.
Whether or not they could have found a way to preserve their civilisation thorough the periods inimical to life is also beside the point. They claim they couldn't predict the occurrences, which is bullshit. You don't need a computer for that, even a biological computer (which I admit was actually kind of a cool concept), you just need paper and pen.
You can't have pretentions to hard sci-fi and just talk nonsense. Either be hand-wavy soft sci-fi or make your explanations conform to our best current understanding. You can't try to explain shit and also get the most basic concepts wrong.
Predicting the orbits of the sun-earth-moon system is easy to do accurately because of the relative sizes and proximity of the bodies.
You don't even need to treat it like a 3-body problem, because the size of the earth/moon have an inconsequential impact on the sun, the size of the moon had an inconsequential impact on the earth, and the proximity of the moon means the sun has an inconsequential impact on it too. So you use a traditional "sphere of influence" 2 body problems, and get very accurate results.
But when the bodies are all large enough to significantly affect eachother's orbits, like a trinary star system, then doing simulation (iterative calculations) quickly builds up errors, especially as the steps are far apart (which they must be with their biological computer, given how slow it is). I haven't run the exact calculations, but I've done interactive simulation in the past and it can pretty quickly fall apart
Edit:
Now i just think you're being disingenuous.
Are you really trying to say you think the author understands the three-body problem?
Are you saying the errors from iterative calculations of three stars and a planet build up so fast, and that they move so fast, that they can go to sleep one night with everything fine and completely without warning wake up the next morning with a sun filling the entire sky or all three suns looking as far away as Sol from Neptune?
When in the book do you think that happens in a single night?
Do you mean in the video game invented by the aliens as a puzzle game, presenting a dramatized retelling of their society's history to keep the humans engaged in the puzzle, that clearly played it super lose with the passage of time?
I assume the Trisolarins were taking a little poetic licence there. I was being hyperbolic. I don't remember the author being specific about the timeline but I had the impression the cataclysms came on pretty quickly (much too quickly to be explained by errors building up, I would think they would constantly update their calculations with their observed track so significant errors should always remain well into the future), and they were just trying to get several months, maybe a year, of warning so they could cache some things that would give them a headstart next time around. Why they didn't just have that all the time, i don't recall that being explained. I guess short-sighted politicians are universal.
Are you just going to keep moving the goalposts and nitpicking my characterizations, or answer the question? Do you think the author understands the basic concept of the three-body problem?
I assume you have an opinion on it because you stuck your nose in here. Or did you just want to throw out an "um ackchyually"?
Yes, I think the author has at least a rudimentary understanding of the 3-body problem.
It's been a bit since I read it, but from what I remember is they wanted to know how long they had before a world-ending cataclysm that they couldn't recover from, aka how long they had to migrate everyone to a new system. to plan for the evacuation they needed to know how long they had, and how much of that would be in hibernation. And I think there was some other complication that made evacuation a problem but I forget the details now.
The point is they wanted to know centuries ahead, iirc, to make their plan.