Trisolarans knew about the rule "sit silent," so they should not allow Earth to send another transmission. That means they must use sophon to freeze Earth (just like what happened with the Trisol during sophon construction.)

Another bonus would be the destruction of mankind and a fresh empty planet for trisolarans.

  • 1
    If memory serves the Earth Command were hoping that they'd do that because the sophon in that configuration could be easily destroyed by nuclear weapons in orbit.
    – Valorum
    Commented Sep 11, 2021 at 12:38
  • And they were destroyed on a Trisol, but there they were not guided. In our case sophon could just change size for some short period of time. Commented Sep 11, 2021 at 12:46
  • Also sophon could be placed on the line between Sun and Earth, far from our planet. If sophon is too small, then several sophons could be employed. Commented Sep 11, 2021 at 13:33
  • 1
    Good point,, but killing humans would not be the only result of freezing the Earth. The Trisolarans coveted the planet for its stability; why muck that up when there is an opportunity of taking over the Earth with its biosphere intact? As they did, later in the series. Commented Sep 11, 2021 at 18:22
  • Sure, for that that could just do fast and sudden freezing, and then "unfreeze" it again, even not killing all humans, but destroying society. Commented Sep 11, 2021 at 18:57

2 Answers 2


This situation occurred in the Trisol system. When it's in its extended form, the sophon is extremely vulnerable to nuclear attacks.

Several brilliant fireballs appeared in different parts of the mirror, their blue color distinct from the light reflected from the mirror. These were the exploding nuclear warheads launched by the Trisolaran space defense corps. Because the explosions were happening outside the atmosphere, there was no sound. By the time the fireballs disappeared, several large holes appeared in the mirror, and then the entire surface of the mirror began to tear and crack, until it had broken into more than a dozen pieces.

One assumes that the defence forces on Earth would try much the same thing (e.g. whack it with nukes to see what happens) if a sophon unfolded in space, noting that it's roughly the size of a planet and hence needs to be pretty close by in order to make any significant difference to the amount of radiation being received by the Earth.

  • As a corollary, I think we can assume that it's far enough away to be able to easily avoid nukes, it's probably too small to cause an attenuating effect on solar radiation reaching Earth.
    – Valorum
    Commented Sep 11, 2021 at 13:40
  • But it was able to shield Trisol suns radiation. And it could be placed a bit away from Earth, to avoid nukes. Commented Sep 11, 2021 at 14:57
  • @YaroslavKornachevskyi - It's roughly the size of a planet when unfolded. The means that if it's able to shade the Earth it'll be near enough to nuke. If it's farther away, it won't shade the Earth and won't cause any significant harm]
    – Valorum
    Commented Sep 11, 2021 at 15:09
  • but they could employ many sophons. Also they could hack the nuke - disable its electonics in space. Commented Sep 11, 2021 at 15:15
  • @YaroslavKornachevskyi - The sophons can only hack what they can see. Dozens of black-body nukes diverging from multiple directions at differing speeds would be a pretty decent way to attack something like that, and there's only a limited number of sophons, so losing one or more would be a significant loss compared to a few nukes.
    – Valorum
    Commented Sep 11, 2021 at 15:18

My old hypothesis:

Well, due to the Dark Forest Hypothesis, the trisolarians may fear that an entire planet being wrapped up for a long time may cause suspicion from the technologically hyper-advanced civilisations, causing the Earth and Trisol to be wiped out, like what happened in the third book.

The accident that happened at Trisol was already a risk too large for the Trisolarians to manage.

What I agree with now:

The second book shows that the sophon cannot propel itself or maintain its shape after two-dimensionalization. This makes it vulnerable to ground attacks. The following text is copied from a pirate version.


The deepl translation is as follows. Sadly, I do not own an English copy of the book.

But he then learned that the sophon had no spatial maneuvering or positioning ability after two-dimensional unfolding, and could only hold its shape with the gravitational pull of the planets as its backbone, and if unfolded in space, would quickly lose its planar shape and fold up under the action of the solar wind and other factors, which was why the sophon could only hold its shape after two-dimensional unfolding to be circuit-etched if it wrapped around the three-body planets.

Actually, Luo Ji was concerned about Trisolarians messing with the broadcast via blocking the sun, so maybe temporarily blocking a planet or even a sun doesn't matter that much.

  • They have already messed with a couple of far more visible transmissions (back and forth). Actually, I think that after these transmissions that have to think about getting away from the system, and never bother with the invasion of the Earth. Commented Feb 27, 2023 at 8:16
  • "Sadly, I do not own an English copy of the book." - with some indication of the page (out of x pages total) and/or the chapter, it might be much easier for someone who does to find the actual passage in English for reference. Commented Dec 23, 2023 at 18:10
  • @O.R.Mapper I got a pirate copy of the English version. The text is from a footnote near the end of part three. It was unfortunately left out in the English translation.
    – polantina2
    Commented Dec 25, 2023 at 14:33

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.