At the end of The Three Body Problem, we discover that the Trisolarans are able to 2-dimensionalize a proton and make it into a computer called a sophon.

The 2-dimensional sophon stretches across the entire sky, wrapping the entire planet and shading it from the stars. From the description it seemed that its mirrored surface would be very protective from electromagnetic radiation. It is capable of becoming more or less transparent so they could tune it how they wished. EDIT: It seems I was wrong about the transparency. I couldn't find the source saying it could become more or less transparent. However, there is another potential solution by stretching it only so far when in 2D mode, and intelligently reflecting light when in a cold era or blocking it during a hot era. Though this would be much easier to explain why this would be difficult or impossible given the nature of the 3-body system since it would have to be more preemptive and the system cannot be predicted.

Once they had created this, couldn't they have just used this sophon to protect them from the harsh environments during Chaotic eras? This seems like it would have solved their survivability problems much more effectively than interaction with the humans.

Note: I have only begun book two so maybe this is addressed later.

  • I can't find any text saying it can become more or less transparent while unfurled. Which section of the book is that in?
    – Jontia
    Commented Mar 9, 2018 at 8:05
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    The answer to questions involving world-spanning computers is usually 42.
    – Spencer
    Commented Nov 20, 2019 at 19:37
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    I do not think you are mistaken. P. 407: "But, finally, after the last ray of sunlight was blocked, everything sank into the darkest night in the history of Trisolaris. [...] the proton plane formed a gigantic shell ... Bitter cold followed." P. 417: "We have already written the software to allow a sophon to unfold itself into two dimensions. After the unfolding is complete, the huge plane can wrap itself around the Earth. This software can also adjust the membrane so that's transparent, but the degree of transparency can be tuned in the frequencies of the comic microwave background." Commented Jan 21, 2022 at 19:33
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    It was addressed in the first book. They were expecting their planet to fall into the sun in the next thousand years or so.
    – J Doe
    Commented Feb 26, 2023 at 5:52
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    I had to comment on this as it really bothered me: it is made clear the Trisolarans want to destroy humanity. Why didn't they just program the Sophons to stretch into 2d form and block all sunlight from reaching earth? It seems to me there was no need for the whole fancy slow down science thing. The Sophons were so powerful there were many ways they could have outright destroyed humanity in a matter of weeks, leaving the planet ready and uninhabited for the Trisolarons when they arrive - (note I haven't read book 2. Maybe it deals with this) Commented Aug 14, 2023 at 12:16

2 Answers 2


I don't think we get the sense that the trisolarans, in their advanced state of technology, are terribly bothered by the chaotic and stable eras anymore. At least, we don't get much information about it. However, we do know that they know their planet will inevitably, at an unknown point, fall into one of their stars. This is the real driver, I gather, of their frantic search to find a better planet to make their home.

BTW, asking a question on the internet like this before finishing the series is a risky move. I almost mentioned something from the third book.

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    You can always put things in future series inside a spoiler tag (>!). Commented Mar 25, 2018 at 14:17
  • Or you can totally not use spoiler tags!
    – Lexible
    Commented Jan 29, 2019 at 23:58
  • "are terribly bothered by the chaotic and stable eras anymore" - I can't point out an exact statement right now, but if I recall correctly, the entire point of slowing down humanity's science was because they expected Earth science to steadily progress during the 400 years it takes the Trisolaran invasion fleet to reach Earth, whereas science on Trisolaris would suffer (or at least be at risk of) regular setbacks when the next chaotic era arrives. Not saying they would have to start at zero, but it would be disruptive enough for Trisolaran science progress that Earth would overtake ... Commented May 11 at 8:29
  • ... Trisolaris in those 400 years research-wise. Commented May 11 at 8:29

The Trisolarans' sophons were, as you may recall, able to be shattered by particle collisions in particle accelerators (albeit they were also able to reasseble themselves). Given that particles carrying much more energy than those in our most powerful accelerators (i.e. cosmic rays) are constantly bombarding our upper atmosphere and planet—and the same would be true for their planet—a long-term sophon shield seems a non-starter.

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