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The Dark Forest hypothesis is one put forth by author Liu Cixin in a novel named thus, which essentially revolves around three primary assumptions:

  1. There is life everywhere throughout the galaxy - advanced civilizations are exactly as common as we think they should be.
  2. The primary goal of all civilizations is to survive as long as possible.
  3. The total amount of available matter in the galaxy (or universe, if we're talking about scales that large) is constant, while growth of all civilizations is always positive.

Thus, some conclusions can be made:

  1. For any given civilization, all other civilizations increasingly consume resources that the given civilization then can't consume - all other civs take from any given civ.
  2. Since there is a constant and finite amount of matter in the universe to use, allowing other civilizations to exist is an existential threat to any given civ.

And, finally,

  1. Any given civ capable of doing so should exterminate all other civs it finds in order to prevent those other civs from consuming its resources and limiting its growth (and therefore lifetime).

From that, we can draw one final conclusion:

  1. Since all sufficiently-advanced civs will be attempting to exterminate all other life, the only way to ensure survival against other civs is never to become apparent: to forever hide and never to reveal that your star system contains any life, or anything of value whatsoever. Revealing the location of a star system containing life is virtually a death sentence for that life, since after a sufficiently long period of time, an aggressor civ will come to wipe that life out (after all, there must be a civ somewhere out there capable of doing so - see statement 6).

This leads to a "dark forest", full of heavily-armed "hunters" who forever hide in the darkness but will annihilate any "prey" they come across.

This is a terrifying scenario! Furthermore, it indicates that it's possible that there may be other hyper-advanced civilizations hiding in plain sight around Proxima Centauri, and, since we've done nothing to conceal ourselves and our endless radio-transmission scream into the void, that there may be an invasion fleet on the way. What a wonderful world!

Anyway, onto the question. This seems like a very interesting hypothesis to build a world around, but it's hardly interesting for there to just be total blackness everywhere, so imagine a world where there is a single civilization that, after devoting centuries to technological and societal development, has become totally self-sufficient and capable of fast interstellar travel. This civilization (which, all things considered, probably isn't humanity) wants to explore the galaxy; the issue is, how does an explorer civilization guarantee that it will survive exploring the Dark Forest? In the dark forest scenario, revealing yourself is suicide, and there is bound to be another powerful civ on one of the planets selected for exploration by this explorer civ, and it is unclear to me how such a civilization would ensure that, no matter where it explores, it won't be annihilated by whatever other civilization it encounters there.

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    $\begingroup$ There are many problems with the scenario. Such as the hunters will attract much more unwanted attention by blowing up planets (or even stars) than will human-like civ with their weak radio noise. $\endgroup$
    – Juraj
    Feb 25 at 21:26
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    $\begingroup$ Step 1 would be to send out swarm of self replicating probes to expand across the galaxy and spy on every single star system to find out what is out there and what's not. Ideally these probes would do their best to try and avoid being seen while they do the observing and transmit data back home. $\endgroup$ Feb 26 at 2:53
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    $\begingroup$ @quarague if it's so easy to blow stuff up and not being caught then it's even easier if you don't do anything rash like that. $\endgroup$
    – Juraj
    Feb 26 at 8:45
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    $\begingroup$ That Dark Forrest hypothesis sounds kinda weird. All lifeforms we know that are bothered that someone make take their limited resources become highly territorial and spend their time marking their land and signaling everyone else to stay out. $\endgroup$
    – user28434
    Feb 26 at 13:48
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    $\begingroup$ Why does this argument not apply to countries in todays finite world? $\endgroup$ Feb 26 at 16:15

9 Answers 9

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Guarantee? You can't.

Take the galactic element out of the story and what you have is the history of exploration/colonization on Earth.

Now, as a slight Frame Challenge, there is a flaw in the premises:

The more advanced a Civilization, the more likely they are going to want to trade with near-peers.

And there's a reason for that:

The closer two civilizations are in terms of Martial Strength and capability - the more costlier for both it is to engage in Warfare.

Now, those rules don't apply when there is a significant disparity in force. Case in point - the British treatment of Australian Aboriginals.

However, as with the Maori (and their development of Trench warfare) - when one group demonstrates that they pose enough of a threat to be dangerous - then Trade is preferred.

So - what is an Explorer civilization to do?

Well - the old Axiom is "Walk Softly, and Carry a big stick"

They would want to be Armed to the teeth So that any dark forest hunter has to seriously consider the cost/benefit of engaging in combat with them.

They also need to walk softly - and this is probably the trickiest part, how do you be respectful of a culture you've never interacted with? Is approaching Silence considered rude? Should you make noise?

Again, referencing Maori Culture - in a traditional Powhiri (welcome) - Women sing a karanga (A Song that involves Greetings, tributes to those recently died, reason for a visit etc.) - then there is the Challenge - in front of Armed Warriors, a small token (Branch) is laid on the ground - the whole process is 'We are ready for you to find out if you mess around' but also 'If you don't start nothing, we won't either' - essentially, it's Politeness maintained through a well-armed society.

(I'm doing a super-duper condensed version here to articulate a point)

So, Your traveler would want to be extremely well armed, but also not trigger-happy, very confident and with something to offer in return

However, all that said - a Society that sincerely believes that any discovery is an existential threat - has already decided that any losses are preferable to the alternative - and should your explorer come across such a society - their options are to Fight and be victorious or die.

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    $\begingroup$ Agreed, not to mention that The Dark Forest scenario has so-called "civilisations" destroying entire solar systems, ie the very resources they are supposedly in competition for! $\endgroup$ Feb 26 at 5:02
  • $\begingroup$ @KerrAvon2055 the 3rd book explores the far future and hints that some of the civilisations are so advanced that even the raw materials of a destroyed solar system could be harvested. Not sure about flattenings, the unofficial 4th book (expansion of the universe by a different author) states it is not reversible, but we don't know what the original author's thoughts were. $\endgroup$
    – Tom
    Feb 26 at 8:16
  • $\begingroup$ See why Japan wasn't colonized during the Great Navigations era. $\endgroup$ Feb 26 at 13:07
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    $\begingroup$ this is also seen in game theory. cooperation yields more resources than conflict in most situations, trust is the only issue that gets in the way of that. Also cooperators have a big incentive to wipe out non-cooperatives, and more importantly better capability too do so. combative civilizations should quickly get wiped out. $\endgroup$
    – John
    Feb 26 at 21:43
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    $\begingroup$ Additional historical consideration is that in pre-modern warfare, winning a war was usually a net benefit for the winning state/people/... Societies valuing military prowess had an edge. Modern war has become so destructive that in wars between near peers, even the winner is worse off than if no war occurred. One can argue that the increased value we currently assign to peace is a cultural adaptation to the lethality of modern war. Technological advances increase the destructiveness of war while increasing gains from trade and can thus increase pacifism. $\endgroup$ Feb 27 at 9:15
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Accepting the Dark Forest hypothesis as stated, the only way for an explorer civilization is to be mobile and distributed, i.e. tribal nomad organisation.

If the explorers have no discernible link to their mother civilization, the discovery of the explorers does not endanger the civ. If the various explorer units are independent of each other, it also doesn't directly threaten the other explorers (though it probably raises their risk).

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Survival by constantly moving

There's a bunch of flaws in the dark forest scenario, but one of the unavoidable constraints on information transmission is time.

If you have a roving, exploring civilization that stays, say, less than the amount of time normally taken for signals to reach the next star, harvests everything it can, and then moves on, any strikes will hit behind it.

I'd imagine an entirely shipborne civ, sending out probes constantly to the next star system they are headed to. If there's another civ there, they change course, and go vacuum up other resources.

They'd need to be pretty fast - depending on the likelihood of detection, you may want to be a sufficient number of star systems away by the time another civ can detect where you were, otherwise they may make the choice to just wipe out, say, the closest 8 stars to you.

You also, maybe, get some excellent research data by goading other civilisations into striking somewhere where you were and left probes - you'd see whatever interesting physics they use to wipe out star systems, you may get some information on the direction of the strike, all of which might inform your response.

You're basically playing battleship, but you might get an advantage by being able to move your pieces around after each shot. And every shot gives you an idea of where the attacking civ is, and what tech they have

(If, for example, a solar detonator hits the star you were just at after 25 years, signal travel time + probe travel time would give you enemy civ's distance from the star you left, letting you draw a sphere. Draw another sphere, from another hit, and you start to be able to pin down where they're shooting from, and hopefully respond. Their maths is harder, because you're moving.)

Edit: My two assumptions on communications speed:

  1. Probes can have ansibles - i.e, instantaneous communication
  2. Nothing else can go faster than x, where x is probably the speed of light, but may be faster if someone has discovered some new physics
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In networking there is the concept of blackholing and detection of the very same. https://en.wikipedia.org/wiki/Black_hole_(networking)

This of course needs communication back to others, who you dont want to see traced and whose breaching you want to be able to firewall, with a.

https://en.wikipedia.org/wiki/Clandestine_cell_system

Colony ships would wipe all memories of the past, all references to the planet of origin, even all knowledge of star charts would be falsified before the deep sleep journey.

All that would remain, is a dead drop, to communicate back about stalkers, intercepts and enemies. No communication back, is communication too. Areas of space would be spheres of danger in a map of the dark forrest. Node falling silent would be sign of enemy expansion. At the same time, you would want information about encounters to propagate. And be ever fearful ob subversion, of your colonists being worrn as skinsuit by one of the stalkers, to unravel more of the cells.

The core of civilizations would be well hidden. In the energy and material less voids, trying to not attract the attention of other stalkers. The galaxybands in between would be the battlespaces, with lots of suspicous premature supernovas and planets getting regularly unihabitated with meteorshowers etc. Great care would be taken, to make "murders" plausible, to avoid suspicion and retribution.

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  • $\begingroup$ Imagine: The indoctrination a colonist ship might get, a completely fabricated backstory- of a civilwar, atrocities, a ending civilization, a horrific regime - only to missdirect and scare off potential interigators. $\endgroup$
    – Pica
    Feb 27 at 13:26
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    $\begingroup$ The end result of this will surely be each independent colony ship becoming a hostile civilisation. $\endgroup$
    – crobar
    Feb 27 at 23:38
  • $\begingroup$ So the trick is to have there hostility focused on something external, while being scaled back when meeting "allies" we do not know about. $\endgroup$
    – Pica
    Feb 28 at 8:05
  • $\begingroup$ How do you get a memory wiped culture to send back data to a place we're there is nothing? $\endgroup$
    – Pica
    Feb 29 at 6:59
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Grow

Herbivores on Earth don't survive by being able to defeat predators. They survive by out breeding the predators. And if the predators outbreed the herbivores they end up starving due to lack of food.

Segment

Species are and can be wiped out by various predators - viral, animal, or other. A typical predator needs to spread from one instance of the creature to another - by segmenting your population, this becomes less likely.

Spread

Spread your population at nearly the speed of light. This is the cosmic speed limit - any hunters cannot exceed it.

Communicate

Communicate using wide-band messages that don't specify who you are talking to. Your hunters have to mimic these messages saying "all is well", or give warning, and cannot miss any cases where the message is sent with valuable information about the hunters.

Keep the bandwidth of this communication small, to reduce the chance of infohazards. The predator's best move might be to flood it with random garbage to hide any real useful information; also, as the predator doesn't know if it has already been spotted due to relativity, it has to do so before it happens.

Concrete plan

Do the "launch self replicating probes to every galaxy" trick. This spreads and segments your population over the entire universe. Within each galaxy, have a few dozen probes arrive at nearly random spots, attempt to bootstrap up to a copy of your civilization, and then spread out from there (both locally and intergalactically again, as a matter of redundancy).

The arrival to growth phase can be done realtively stealthily, with only a launch being more obvious. A hunter looking to destroy all of your spreading seeds has to spend exponentially more effort on it than you did launching, and many of those seeds are going to places that are going to be causally disconnected from the local galaxy by the time they arrive.

The only hunters you are going to face for them are logically those that followed a similar strategy before you - they have to have some stake in what happens in causally-disconnected events in far galaxies!

Your local probes face more likely opposition. But you can lose almost every probe - if only a few survive, your growth continues exponentially. Even if every probe going to this galaxy is destroyed, so long as any galaxy anywhere doesn't destroy your probes you continue to expand.

You can't stop magic

A sufficiently advanced technology is indistinguishable from magic. So the problem is that no amount of hiding can hide you from such advanced technology.

You can learn how loud you can be

Vary how loud your probes and their resulting plans are. You might have an idea of how many probes you sent out, and how well you can hear their side effects -- the product of which gives you a ceiling on how loud you can be without being destroyed.

Suppose 1 in 10,000 probes are supposed to mass-launch by turning their star into a supernova launch facility, and you never see the telltales of that happening. That tells you a lot about how well you are spreading.

But if you see such supernovas, you get information about your spread.

(Note that this supernova launch might be a way to send probes between galaxies at a decent clip; the long-distance of the probes being a defence against hunters bothering to destroy them, as by the time they reach their destination, reproduce, and are ready to launch, this galaxy is going to be beyond the cosmic horizon.)

Accept Death

You fully expect most of your lineage to die out. Each branch is a probable sacrifice; but if you have enough branches, even a 99% failure rate is acceptable.

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Any exploration other than passive listening poses more danger than benefit

If you sent out ships or probes that will make only your detection more likely. Yes you might detect a civ before they detect you, but you also give them the opportunity to detect your ship/probe.

And having your probe/ship being detected by others would be the first step to get wiped out. Aside from the most obvious risks of capture etc. just the existence of your probe poses so much danger.

Lets start with a probe and improve it further and further to make your civ resistant against leading others to your home:

  1. An AI controlled probe that gathers data and eventually returns home
    A more advanced civ might capture the probe, dismatle it and find the home coordinates

  2. make the probe selfdestruct when it gets found
    The civ might instead just launch a probe to follow your probe. When they are more advanced, your probe will not detect theirs.

  3. instead of returning home send data home via broadcast
    now your probe has become MUCH more likely to be detected before it detects anyone...

  4. only sent all gathered data home when the mission is over (finding something or after a duration)
    still an enemy civ following your probe now know your data format and means of transmission. They can use it to fake data luring your attack fleet into a trap. Also they know what to listen for in the depth of space and just by that they might find your home.

  5. don't sent anything back
    now you have a useless probe. You don't get any data out of it. Also anyone finding your probe will still now know that you exist and at least some information about how you build your probes. They might be even able to build fake replicas of your probe and sent it on with some tracking to detect you without getting detected yourself.

Fake it till you make it

If hiding your existance is impossible in your universe (detectors outclass stealth, possible due to physical limits) te best option might be to not even try.
Make everyone know about you and your "strength". The fact alone that you do not fear being detected might cause all other civs to fear you so much that they duck and cover in hope of not getting detected by you.
If you have the technology to wipe out a solar system (doesn't matter if it is a bad technology that would be impractical in a real war) it would be a good idea to wipe out a random solar system once in a while regardless whether there is a civ living there. And make sure everybody knows about you destroying that system. You might know there was nobody there, but others will think you detected and wiped out a civ so advanced that they themselves couldn't detect them.
With the possibility to explore the universe unharmed your civ might actually become as powerful as they pose eventually. Or get wiped out by a civ that didn't fall for the trick, probably by something like the WH40k orks, being to dumb to make the connection "I let everyone know I am here" => "I am strong enough to fear nobody"

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Piracy

Each of these civilisations are contained to their own sectors of the galaxy/universe, so there must be some ressources or oddities that one civ has access to but the others don't. So, the best way for an independant non-aggressor party to survive is to become a pilotfish that swims with the shark, and brings it tasty morsels to feed on.

In practice, you get in close to a powerful member of one civilisation by promising them access to ressources that their civilisation could never gain access to directly. You then go around each other civilisation and offer them the same deal. You fill your ships with the most wonderful gems, pets and drugs the galaxy has to offer and go under the radar of all the major civs, making massive profit off of all these exclusive items.

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Nomadic Tribes

The civilization doesn't settle on worlds. They harvest asteroids and build new colonies to grow into and they spread out and keep moving.

A planet or even a solar system can be targeted and all life exterminated but billions of wandering colonies all through the gulf of space is much harder to exterminate in one fell swoop. You might be able to kill a few before the rest know you're an enemy.

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  • $\begingroup$ Wasn't Earth able to detect the Solarian ships approaching from 300 years away though? $\endgroup$
    – DKNguyen
    Feb 27 at 3:04
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Everyone in the Dark Forest is an Explorer Civilization

Asking the question how do explorers survive the Dark Forest is like asking how do tribal societies survive exploring in real dark forests... it is dangerous, yes, but those that do not explore just die; so, you do it despite the risk.

In the Dark Forest scenario as you've described it, everyone is a hunter, as much as they are prey. If there is a nearby civilization consuming resources, then your survival relies on finding and eliminating them. Making first contact puts you at a huge survival advantage, even against a significantly more advanced race than your own.

Think of it like this: if you can build an exploration ship that can traverse the stars, then you are already advanced enough to build one heck of a doomsday weapon. So, if you find another civilization, you have 2 options: wait around for them to find you too putting you in a mutually assured destruction scenario for the remainder of time ... or... you can nuke them before they find you keeping your civilization safe for the foreseeable future. The whole hypothesis behind the of the Dark Forest scenario is that nearly every rational race will pick option #2.

As for how they keep from being tracked home

With every civilization being explorers by necessity, and having no long term technological or cultural exchange with one another, it means that there should be many solutions to this problem, not just one. Some races might rely on cloaking technology, some might use time travel to look for civilizations that are older than thier own and wipe them out before they can become a threat, some might fly dangerously close to stars to dissipate thier warp path, some might have a strict policy of self-destructing when they encounter a species that they lack the technology to wipe out on first contact, some might have policies that only allow exploration do be done from small, distant colonies to make sure that if they are traced back, that only the one colony is compromised. Heck, some might actually rely on forging powerful alliances through diplomacy in which they still choose to keep thier planets dark because even if you are part of a powerful Federation, it does not mean you want to be advertising your presence to other empires that might be even more powerful than yours.

I would suggest listing out all the alien races in your setting, and trying to come up with whatever solution best fits the character of thier unique civilizations.

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