I loved those books, but the dark forest theory doesn’t make sense. Given a dangerous universe it would make sense for a civilization to try to communicate with other civilizations to create alliances for mutual safety.

The civilizations that are able to forge alliances will tend to out-compete lone wolves.

Liu assumes that it is somehow a lot easier to wipe out a civilization than communicate with it, and that for some reason your civilization has to decide to wipe out another civilization without communicating with it.

> Liu assumes that it is somehow a lot easier to wipe out a civilization than communicate with it...

This may be true, though. We struggle to effectively communicate with creatures on our own planet available in real-time, like dolphins and elephants, who appear to think and have language of sorts.

Launching some relativistic sand at another planet may well be a lot easier.

We seem to communicate pretty well with dolphins, elephants, and other animals. Consider trainers who work with these animals on a daily basis and have rich and productive relationships with them.

We can explain "go press that button" or "lift your leg" fairly well. We can't, as yet, put a dolphin through something like an elementary school level education.

alliances put some lower bound constraint on the logistic capabilities and density of the civilisations that form them.

strategically speaking and stunning hostile unknowns a stable civilization controls a territory matching reasonable response time from the ready armies at their combat speed and necessarily a requirement for alliances to form is for these zones to overlap

but if they are at such distance it negates one of the prerequisite for the dark forest theory, that civs are sparse enough for the chance of facing hostiles alone is on par with encountering non hostile civs

Interstellar space isn't an ocean, and star systems aren't countries. Analogies to Earth militaries and navies simply don't apply, the scale of space is too big.

You're not going to form any sort of "alliance" over a distance of light-years, much less consider the fleets of hostile civilizations to be a threat by their proximity the way England once considered Spanish fleets a threat. There's no "reasonable response time" when allies will take years to hear your distress call, and more years to arrive.

I loved the series, but the physics was horrendous, and I don't agree it made a strong argument for the Dark Forest theory. It made an enjoyable, interesting read about the Dark Forest theory, but the schemes the author used didn't make sense and wouldn't result in the universe as described in the books.

Yeah, the book was about allegories and situations. The plot devices were intended to drive certain plot elements, not to be in the Clarkean way the first principle driving rationale for the work.

The trilogy is very enjoyable!

Well put - the way he wrote the "science" was fun and used in novel, clever ways to further the interesting situations and ideas and analogies, which is why it was awesome. Plus it was neat reading a book that was first Chinese and then translated. I found the subtle differences in tones and characters fascinating.

The dark forest theory works wonderfully as a plot device in the book. That trilogy is the best sci-fi I've read after Banks, Clarke and Asimov, hands down.

But, if you stop and think about it, in the real universe it has two gaping problems:

First, The Dark Forest theory depends on the capability and willingness to develop world destroying devices.

Second, it depends on the likelihood that the species you detect has not yet spread to other systems. If it has, congratulations, you have started a shooting war with an enemy whose threat level you have no gauge of. Some with an inclination of game theory might want to figure this out through better, though.

> First, The Dark Forest theory depends on the capability and willingness to develop world destroying devices.

Any civilization capable of traveling to another solar system has this capability: just take one of their ships designed to accelerate to significant fractions of the speed of light and decelerate at the other end of the journey, set a course, and simply don't decelerate.

> Second, it depends on the likelihood that the species you detect has not yet spread to other systems. If it has, congratulations, you have started a shooting war with an enemy whose threat level you have no gauge of. Some with an inclination of game theory might want to figure this out through better, though.

There's a good chance the above described weapon would be nearly undetectable and untraceable. For at least the latter half of its journey, it's just a chunk of mass traveling through space, emitting no signals. It would also be only a small factor difference in capability (0-1 more accelerations and decelerations than an actual interstellar transit) to send it from a different part of the galaxy.

Another book in this vein, although distinctly more uncompromising in its conclusion, is The Killing Star, by Charles R. Pellegrino and George Zebrowski.

Available on Audible now. Hard to find it in print.

Another series is Greg Bear’s Forge of God

Having just today finished Cixin Liu's 'Death's End', I rescind my 'distinctly more uncompromising' comment.