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Comment by anyonecancode | Hacker News Reader

Maybe this just reflect poorly on my numerical intuition, but it seems to me the forest may be dark because it's more of very sparse forest? As in, no matter how many trees there are, they are so far apart from each other that it's really more of a steppe. When "nearby" is tens or hundreds of light years, and most things are not nearby, it seems there's plenty of both time and space to make it very believable that there's just little to no overlap between when detectable civilizations and civilizations able to listen coincide.

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The problem is exponential growth destroys all. You can't explore the universe very quickly on human timescales...but presuming the trend lines of technological civilization hold up, eventually immortal sufficiently-intelligent Von Neumann probes can rapidly and easily (hundreds of thousands of years, but a blink of the eye geologically) explore the entire galaxy.

Even if it took a few million years to do, that's still far less time then the Earth has been habitable and had life. So the question of course is still where are they?

Civilizations will sort out neatly into expansionist and stable. Stable civilizations will be, generally, much, much older than expansionist neighbors, and so incomprehensibly more advanced.

Thus, each expansionist civilization will spread out to encompass an exponentially increasing number of advanced, stable civilizations, and antagonize an increasing number of them. Soon, they will encounter one that chooses to put them in their place, and maybe just wipe them out.

So we may think of the galaxy as an archipelago of stable civilizations that interact little, with splashes of expansionism in between that encounter and annoy them, and are swiftly contained. Such expansions are exceedingly unlikely to get to us before such an event curtails them.

I think that model only works if the stable civilizations are advanced enough to survive arbitrary threats, otherwise they'll just get wiped out by chance over time and replaced with expansionist ones which are more robust against anything other than being systematically destroyed by something they irritated. ... plus to destroy an expansionist civilization you'd have to have significantly superior expansionist technology.

I.e. how do you destroy an expansionist fleet which has scaled up to the point that it's furthest point from you is increasing close to the speed of light?

See, you don't know how, and I don't know how.

But they are, remember, incomprehensibly more advanced than you or me. And they know a bunch of other incomprehensibly more advanced civilizations all the way on the other side of the expansionist noobs. And, just because they don't usually see much point in going out there doesn't mean they can't, or won't, when the time seems right for it.

Not much point in reasoning about magic though, might as well say "God will provide" as it gives similar insight. I think assuming that the laws of physics, as we understand them, and reasoning whats possible and likely within them is a lot more interesting.

I can come up with one respons within the believed laws of physics at how a hypothetical stable civilization could suppress exponential ones even though exponential ones would quickly be expanding their radius at close to C: the stable civilization would need to pre-seed the visible universe with idle hidden outposts of a sufficient density to detect and suppress exponential expanders.

The non-expansionists don't need to fight all possible expansionists. They only need to fight the ones that come around. If B can't beat A, A will soon encounter C, and then D and E, with a fresh roll of the dice each time. The bigger they get, the more adversaries they cross.

We are not predicting the future, but trying to account for an observation. For the scenario to remain on the list of reasons why we haven't been visited, it suffices that it is possible. There are of course lots of other possible reasons, among them that there is nobody to visit.

> The non-expansionists don't need to fight all possible expansionists. They only need to fight the ones that come around.

That come around us since we're trying to explain why we haven't seen an expansionists. So this line of thinking predicts that we're in the shadow of a non-expansionists, I guess?

Exactly.

If the fleet flies far enough, they will merely isolate themselves in the intergalactic space.

> Stable civilizations will be, generally, much, much older than expansionist neighbors, and so incomprehensibly more advanced.

This is not necessarily true. A roiling cluster of ephemeral, competing life forms and civilizations may very well develop warfare and defence technology better and faster than stable civilizations. This is especially true if you consider the cost of stability: all new technology is a potential threat to stability that has to be weighed carefully, so I expect stable civilizations to evolve much slower than unstable ones. In the aggregate, instability is not really a problem: a civilization's progress will be scavenged or stolen by its successors, retaining the advantage, and for that reason I would argue the unstable regime will almost systemically overwhelm the stable one.

You can kind of see this with humanity: a lot of the big problems we have to face as a civilization (but not all of them) result from the careless adoption of technology. Climate change would not be a problem if we had industrialized slowly enough. The Internet spread too fast for us to understand its effects on the propagation of (dis)information. A truly stable civilization would have taken a thousand years to do what we did in a hundred. Perhaps it would be happier for it, but if we met them, we would eat them alive.

The stable societies still standing after confronting and defeating numerous upstarts will be the ones that really are more advanced. You could say there will be a survivorship bias in the extant population.

Both conflict and technological advancement are destabilizing influences, though. How do these societies remain stable? My worry here is that any confrontation with an inventive upstart will require swift change and adaptation in order to fend off the threat, but such fast change is likely to cause internal instability. I don't think there is such a thing as a "stable society" that cannot implode and turn into a bunch of expansionist upstarts, unless they are so careful about progress they are practically defenceless.

Stability and not-expanding are not necessarily the same thing. ("Stable" is easier to write.) They could be extremely dynamic, but if their population isn't exceeding their resources, why do they need more room? Expansion is what brings cultures into contact and conflict.

Puny humans are confined to one solar system, and even just the one planet, but are pretty dynamic. Population in wealthy countries is in decline.

Remember we are not just talking about humans with bumpy heads, here. Social universals on Earth do not apply. Expansion might be limited just by a physical inability to reproduce beyond their home planet, without giving up any dynamism.

>So the question of course is still where are they?

You described barbarians. But barbarians don't need Von Neumann probes, they can do everything they want with a stone hammer.

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