The woods are dark and full of terrors

I wanted to "circle back" on a comment I'd made on the "Dark Forest" hypothesis, which is basically the idea that we don't see signs of alien life because everyone's hiding for fear of everyone else.  This will probably be the last I want to say about the "Fermi Paradox", at least until the next time I feel like posting about it ...

I haven't read the book Dark Forest, but my understanding is that the Dark Forest hypothesis is based on the observation that when a relatively technologically developed society on Earth has made contact with a less developed society, the results have generally not been pretty.   "Technology" in this context particularly means "military technology."  The safest assumption is that this isn't unique to our own planet and species, but a consequence of universal factors such as competition for resources.

If you're a civilization at the point of being able to explore the stars, you're probably aware of this first hand from your own history, and the next obvious observation is that you're just at the beginning of the process of exploring the stars.  Is it really prudent to assume that there's no one out there more advanced?

Now put yourself in the place of that hypothetical more advanced civilization.  They've just detected signs of intelligent life on your world.  You are now either a threat to them, or a potential conquest, or both.  Maybe you shouldn't be so eager to advertise your presence.

But you don't actually see anyone out there, so there's nothing to worry about, right?  Not so fast.  Everyone else out there is probably applying the same logic.  They might be hunkering down quietly, or they might already be on their way, quietly, in order to get the jump on you, but either way you certainly shouldn't assume that not detecting anyone is good news.

Follow this through and, assuming that intelligent life in general isn't too rare at any given point in time, you get a galaxy dotted with technological civilizations, each doing its best to avoid detection, detect everyone else and, ideally, neutralize any threats that may be out there.  Kind of like a Hunger Games scenario set in the middle of a dark forest.


This all seems disturbingly plausible, at least until you take scale into account.


There are two broad classes of scenarios:  Faster-than-light travel is possible, or it's not.  If anyone's figured out how to travel faster than light, then all bets are off.  The procedure in that case seems pretty simple: Send probes to as many star systems as you can.  Have them start off in the outer reaches, unlikely to be detected, scanning for planets, then scanning for life on those planets.  If you find anything that looks plunderable, send back word and bring in the troops.  Conquer.  Build more probes.  Repeat.

This doesn't require listening for radio waves as a sign of civilization.  Put a telescope and a camera on an asteroid with a suitable orbit and take pictures as it swings by your planet of choice.  Or whatever.  The main point is if there's anyone out there with that level of technology, our fate is sealed one way or another.


On the other hand, if the speed of light really is a hard and fast limit, then economics will play a significant role.  Traveling interstellar distances takes a huge amount of energy and not a little time (from the home planet's point of view -- less for the travelers, particularly if they manage to get near light speed).  By contrast, in the period of exploration and conquest from the late 1400s to the late 1700s it was not difficult to build a seaworthy ship and oceans could be crossed in weeks or months using available energy from the wind.  The brutal fact is that discovering and exploiting new territories on Earth at that time was economically profitable.

If your aim is to discover and exploit resources in other star systems, then you have to ask what they might have that you can't obtain on your home system using the very large amount of energy you would have to use to get to the other system.  The only sensible answer I can come up with is advanced technology, which assumes that your target is more advanced than you are, in which case you might want to rethink.


Even if your aim is just to conquer other worlds for the evulz or out of some mostly-instinctive drive, you're fighting an extremely uphill battle.  Suppose you're attacking a planet 10 light-years away.  Messages from the home planet will take 10 years to reach your expeditionary force, and any reply will take another 10 years, so they're effectively on their own.

You detected radio transmissions from your target ten years ago.  It takes you at least 10 years to reach their planet (probably quite a bit longer, but let's take the best case, for you at least).  They're at least 20 years more advanced than when the signal that led you to plot this invasion left their planet.

You've somehow managed to assemble and send a force of thousands, or tens of thousands, or a million.  You're still outnumbered by -- well, you don't really know until you get there, do you? -- but hundreds to one at the least and more likely millions to one.  You'd better have a crushing technological advantage.

I could come up with scenarios that might work.  Maybe you're able to threaten with truly devastating weapons that the locals have no way to counter.  The locals treat with you and agree to become your loyal minions.

Now what?

Unless your goal was just the accomplishment of being able to threaten another species from afar, you'll want to make some sort of physical contact.  Presumably you land your population on the planet and colonize, assuming the planet is habitable to you and the local microbes don't see you as an interesting host environment/lunch (or maybe you've mastered the art of fighting microbes, even completely unfamiliar ones).

You're now on unfamiliar territory to which you're not well adapted, outnumbered at least a hundred to one by intelligent and extremely resentful beings that would love to steal whatever technology you're using to maintain your position.  Help is twenty years away, counting from the time you send your distress call, and if you're in a position to need it, is the home planet really going to want to send another wave out?  By the time they get there, the locals will have had another twenty years to prepare since you sent your distress call, this time with access to at least some of your technology.


I'm always at least a little skeptical of the idea that other civilizations will think like we do.  Granted, it doesn't seem too unreasonable to assume that anyone who gets to the point that we would call them "technological" is capable of doing the same kind of cost/benefit analyses that we do.  On the other hand, it also seems reasonable to assume that they have the same sort of cognitive biases and blind spots that we do.

The "soft" sciences are a lot about how to model the aggregate behavior of not-completely rational individuals.  There's been some progress, but there's an awful lot we don't know even about our own species, which we have pretty good access to.  When it comes to hypothetical aliens, I don't see how we can say anything close to "surely they will do thus-and-such", even if there are practical limits on how bonkers you can be and still develop technology on a large scale.

In the context of the Dark Forest, the question is not so much how likely it is that alien species are actually a danger to us, but how likely is it that an alien species would think they were in danger from another alien species (maybe us) and act on that by actively going dark.

Our own case suggests that's not very likely.  There may be quite a few people who think that an alien invasion is a serious threat (or for that matter, that one has already happened), or who think that it's unlikely but catastrophic enough if it did happen that we should be prepared.  That doesn't seem to have stopped us from spewing radio waves into the universe anyway.  Maybe we're the fools and everyone else is smarter, but imagine the level of coordination it would take to keep the entire population of a planet from ever doing anything that would reveal their presence.  This seems like a lot to ask, even if the threat of invasion seems likely, which, if you buy the analysis above, it's probably not.

Overall, it seems unlikely that every single technological civilization out there would conclude that staying dark was worth the trouble.  At most, I think, there would be fewer detectable civilizations, than there would have been otherwise, but I still think that as far as explaining why we haven't heard from anyone, it's more likely that whatever civilizations there are, have been or will be out there are too far away for our present methods to detect (and may always be), and that the window of opportunity for detecting them is either long past or far in the future.