[cogman10]

Still doesn't make sense. Why limit our tech when they ultimately want to just eliminate us all together?

Drop a super virus on us or irradiate the whole planet. Any species capable of disrupting our particle accelerators is more than capable of wiping us from existence.

[temporalparts]

More spoilers:

In the book, they were scared of humanity's technological growth rate. They were observing our technological advances and noticed that it was significantly faster than theirs. While they were, at the time, technologically superior, they were afraid that after the 250+ years it would take for them to get to Earth, humanity would have become technologically superior; too strong for them to overtake.

[SkyMarshal]

They could send the subatomic particles from Trisolaris to Earth at light speed, and then use the entangled pair of particles (one on earth, its mate on Trisolaris) to monitor events on earth in real-time.

As already said, that preserves the planet, prevents a potential enemy from further developing technologically, and enables real-time monitoring of and interference with that enemy's activities.

[roywiggins]

>and then use the entangled pair of particles (one on earth, its mate on Trisolaris) to monitor events on earth in real-time.

This, of course, breaks the known laws of physics, since lightspeed is a hard limit on the speed of causality. You can't use entanglement that way in the real world (if QM is anywhere close to correct)

[AmericanChopper]

The sophons themselves were a piece of magic science fiction. Which I think is fine because the author really doesn’t ask you to suspend your disbelief all that much throughout the books. The star plucking is another example, as far as we know you can’t use a star to do that.

But accelerating them towards earth “at the speed of light” isn’t exactly a problem. The LHC accelerates protons to about 3 m/s less than the speed of light, and as far as the plot is concerned the sophons travelling here at the speed of light, or some tiny fraction of a percent less than the speed of light doesn’t make any difference.

[iainmerrick]

Right, that was the huge issue I had with the story. In most respects it seemed to be trying hard to be speculative hard SF in the Arthur C Clarke vein (i.e. fine to introduce exotic new physics, but only very carefully and consistently) so it was very surprising to have that gaping hole at the centre.

The aliens had instantaneous communications, and could directly influence events on earth, but still had to travel at sublight speeds? It wanted at least an acknowledgement of the inconsistency, and a token effort at explanation. As others have noted, it’s not at all clear why they couldn’t simply have killed off the humans remotely.

[Vecr]

I can't reply to roywiggins for some reason, but it's possible that the solar systems are closer in other dimensions or something like that. Probably not though, because the higher dimensions are so small. I assume the author didn't think about it until it was too late, or they couldn't fix it.

[EthanHeilman]

The book makes the claim that the sophons they send over are very limited. It seems reasonable to surmise that they could not create a super virus. Yet they can disrupt sub-atomic experiments. We are talking about an advanced basically magic tech the author made up for the purposes of the plot. So the author can set the rules that the magic tech can do X but not Y.

[dylan604]

It's kind of like nuclear warfare here on Earth. If you want to eliminate every living thing, then sure do some sort of scorched Earth type of thing. However, that leaves the planet in an un-inhabitable condition.

If you need to wipe out the inhabitants but leave everything else so you can now use it, you need to not destroy everything in the first place. Otherwise, you now have to terraform a planet that you chose because you didn't need to terraform it.

[numlocked]

That was probably the plan; but the “tech-blocking particle” gets here at the speed of light, ensuring that we are still sufficiently behind, technologically, by the time their e.g. virus or radiation gizmos arrive. It “freezes” development to ensure that they still have technological superiority when the much-slower, barely-relativistic, big guns arrive.

[AmericanChopper]

They did also send weapons towards earth ahead of their fleet. They arrived much faster than their fleet, but much slower than the sophons.