[gizmo686]

Spoilers below:

The Three Body Problem trilogy breaks down if you think about it too hard. The in-universe explanation was that the aliens did want to destroy us, and had an attack fleet heading towards us. However, the attack fleet was relativly slow, and they were concerned that by the time it reached us we would have advanced to the point where we might win in a fight. To prevent this, they sent smaller probes to us at near light speed. In theory, these weren't capable of causing significant damage, but they could cause enough of an effect that they could make the results of particle accelerators useless. Without being able to use particle accelerators, we wouldn't be able to advance our knowledge of fundamental physics, so the aliens were confident that when their attack fleet reached us we would be defenseless.

By itself, what I have written is not particularly absurd, but if you look at the other things those advanced probes ended up being able to do, they could have easily just killed everyone.

[rsynnott]

The sophons don't seem to be able to do anything much beyond bother particle accelerators. The later droplet probes _are_ very nasty, but it's at least implied that those weren't even available at the time they set out.

[ASalazarMX]

Killing everyone is too much to ask, remember they were ultimately just protons, physically they're not more powerful than cosmic rays.

Their strength was information gathering and special effects.

[gizmo686]

Protons that could cause controlled visual hallucinations in people. If they can cause that level of interference with our nervous system, they can kill us. Even if they were somehow limited to visual hallucinations, a well timed hallucination is easily lethal. They probably ought to be able to hack into computer systems with that as well.

[HotHotLava]

Tbf, from the way they were described it should have been fairly easy to defeat the Sophons even without any science-fiction technology; just build e.g. 10-20 particle accelerators distributed over the world and take measurements close enough in time to each other that you cannot be at multiple sites without exceeding the speed of light. Then at most 3 of them could be corrupted for any given run, and these can be thrown out as statistical noise.

[xster]

I think the argument was that they could send Sophons faster than we can build particle accelerators.

[rsynnott]

This is addressed in the book; a new sophon is cheaper than a new particle accelerator.

[wdwvt1]

Totally agree with this, the effort to retard development could have been better spent with a myriad of ecosystem destroying actions or geopolitical manipulations. Also just send the indestructible probe to kill every human...

My bigger problem with this book was that the author seems to wholely confuse secrecy for strategy. The entire conceit behind the wallfacers seemed ridiculous to me. The best strategic plan need not be secret (eg MAD). Make it clear that humanity will destroy every planet in the solar system and you've got at least MAD in the centuries the trisolarians will take to arrive.

[gizmo686]

More spoilers below:

They actualy did a fair amount of geopolitical manipulations. That formed most of the plot.

In the end, it turned out to be MAD that saved us, but setting up the MAD scenario involved secrecy from them (or else they would have stopped us before we could trigger it), and from the rest of humanity (because an official plan to destroy Earth would never have been approved).

[wdwvt1]

It seems like the manipulations were exceedingly silly. It seems like having the sophont start a nuclear war would be straightforward. It was hard for me to suspend disbelief in the sense that it had planet-sized computational power and the ability to manipulate some information on the subatomic level, but couldn't find a vulnerability in aging nuclear launch protocols? The history of near misses with human controlled nuclear weapons suggests a variety of vulnerabilities exist that wouldn't require e.g. directly hacking into command and control. Could it spoof images/data to a sub? Could it cause hallucinations in a large sensor array that feeds data to Norad or a Chinese/Russian equivalent?

Re MAD: I think a plan to destroy Earth would have been easily approved - much like it was in 1960-now, with ICBM and SSBN retaliatory strike capability. Obviously somewhat different in that those MAD-based nuclear wars would be extinctive but not deny the planet to the trisolarians, but the idea that human governments aren't ready to commit to that seems wrong given our history.

[bmh100]

The aliens specifically wanted Earth because of its life. A nuclear war would damage the planet's ecosystem too much.

[shhsshs]

> In the end, it turned out to be MAD that saved us

Read the rest of the series and this answer gets more interesting. I will not say any more about the outcome (spoilers)

[saiya-jin]

They cared about our stable single sun more than planets. We were not on the level to destroy our sun, or the planets themselves