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> Cixin Liu, like most other hard sci-fi authors, and everybody else who thinks about those things, seems to assume that lightspeed is just as problematic for everyone else as it is for us humans.

... the primary weapon of the Trisolans in the first book are subatomic ansible faeries.

I thought it was kind of funny, because the whole point behind the Dark Forest theory is that it emerges because aliens are so unknowable, there can never be proper trust between them. Yet a relatively young and slowly-developing race is literally more sure of what humanity is doing than we are of our neighbouring countries.

"Hard sci-fi", pfft :P

+++ SPOILERS +++

Eh, they had inside information (the Earth-Trisolaran Organisation was in contact with them).

And it's hard sci-fi because they were AIs made of protons, not actual fairies found in the magical forest of Elthrolien that had to be seduced with promises of space mead.

That's how it goes with sci-fi, innit. You can come up with anything you like as long as it's obvious that it's just advanced technology, not magic. Cixin Liu usually manages to weave in a couple of natural laws to every impossible thing so he passes.

I was more annoyed by the lightspeed contrails to be honest. That really comes out of nowhere and is a total literary device that has no basis on anything we know of. Makes the whole endeavour space opera if you ask me - which is not bad in and of itself. But in that case, where's the nuclear energy-sword wielding hero who saves humanity? Disappoint.

> And it's hard sci-fi because they were AIs made of protons, not actual fairies

Does mentioning your faeries are made out of atoms stop them being fantasy?

> That's how it goes with sci-fi, innit. You can come up with anything you like as long as it's obvious that it's just advanced technology, not magic.

Sure, I mean, even Star Wars is still considered within the genre despite it all being completely made-up - but the point of hard sci-fi is you're not just making it up and rubbing science-words on your endless stream of arbitrary plot contrivances.

My opinion on this might be controversial but I think there's very little difference between even "hard" sci-fi and all-out fantasy (but, with spaceships). There is very little space left to write a story that is interesting and compelling if one wishes to respect the bounds of what is scientifically plausible.

Then again, if one starts to stretch the definition of "scientifically plausible" there's all sorts of things that are classic sci-fi tropes like Einsten-Rosen bridges and Alcubierre drives, etc. So it's just my opinion. But, I note that the best Sci-Fi stories I've read always took lots of liberties with the laws of nature.

I'll even come up with a few examples if I really think about it.

>There is very little space left to write a story that is interesting and compelling if one wishes to respect the bounds of what is scientifically plausible.

Are we living in the same world? Quantum mechanics, relativistic effects, mathematics ( game theory anyone? ) are blowing my mind. The world is more phantastic than anything one could imagine and we know that we don't know everything. The constraint to stay in this world is the least limiting for an interesting and compelling story.

But those are not science fiction. If you tell a story that is within the limits of what we know to be possible with the knowledge that we have right now, you will end up with a very boring story. If you start speculating about what _might_ be possible- you'll end up with time travel through black holes, like in Interstellar, which makes for a nice story, but not a very realistic one.

There is a trade-off between speculation and realism, that leaves a very, very narrow space for an interesting story.

Part of it is due to the fact that most of modern science has been mined mercilessly for "hard" sci-fi subjects, that have now become tropes that can't form the basis for an interesting new story anymore. For example, try to write a story where the entire premise is that someone manages to construct an Alcubierre drive. You'd get ...Star Trek: First Contact. Nice movie, hey. But nothing new, there.

Er, no, on all counts.

> But those are not science fiction.

Stories based on physics and maths are not science fiction? Are you feeling OK?

> If you tell a story that is within the limits of what we know to be possible with the knowledge that we have right now, you will end up with a very boring story.

Um. Most stories in general stay within reasonable limits of what we know to be possible - are most stories very boring? You basically seem to be arguing that all stories that aren't fantasy are boring, which is clearly untrue.

> Interstellar, which makes for a nice story

Interstellar is tediously boring rubbish :P

> For example, try to write a story where the entire premise is that someone manages to construct an Alcubierre drive. You'd get ...Star Trek: First Contact.

What... no? The phase-space of all possible Alcubierre-drive fiction is not "Vulcans come to visit", any more so than the phase-space of all possible stargate fiction is "Ra gets quite angry".

He makes a lot of interesting hash from the speed of light (like the Dark Domain defense). But he more or less handwaves away the speed of light as a limitation, introducing viable FTL travel in Death's End. (As an aside, one of the things I like about the books is how terror scales... from the understandable, relativistic terror of the Trisolarans to the much more threatening terror of the Dark Forest, to the sheer hopelessness of some species altering the very laws of physics as a weapon.)

> to the much more threatening terror of the Dark Forest, to the sheer hopelessness of some species altering the very laws of physics as a weapon.

Yup. Reading the implication that the universe has only 3 dimensions because dimensionality reduction weapons were used in past wars triggered a small existential crisis in me.

Spoiler tags please! For the uninitiated.

Dimensinoality reduction? I never thought of those weapons as akin to universal PCA before. Thanks for the image.

Not really, since DFT covers how fast information travels, not biological bodies. Lifespans aren't really part of the equation.

That's not to do with Dark Forest Theory, but why do you say it's about how fast information travels? I take it as a theory about the outlook of technological civilisations with respect to each other.

And yes, lifespans are important. Perhaps not in the books, but in the real world our science and technology advances at least some in every generation, as new scientists and technologists continue the work of their forebears.

If human generations lasted a thousand years, it would perhaps take us a lot longer to make the same technological progress that it now only takes us a few years- if nothing else because the urgency of making progress would be reduced accordingly.

Lifespans may also influence the actualy speed by which species form thoughts and communicate. Remember the Ents in The Lord of the Rings? A species that lived ten thousand years may take an Earth day to form a meaningful utterance. Technological advancement would take considerably longer for them than for us.