Hacker News Reader

Comment by aetherson | Hacker News Reader

Short lived on those timescales, yes. But not necessarily short lived in terms of our perspective.

If we imagine that in the last 5 billion years, there have been a good solid 10,000 post-industrial civilizations, and each of those civilizations has lasted 10,000 years (in the post-industrial stage where they're detectable), then that implies that of the last 5,000,000,000 years, 100,000,000 of them have been host to a post-industrial civilization: a given year has on average 0.02 currently present civilizations in it.

Now, this hypothesis does probably imply that significantly interstellar civilizations are impossible, since it seems like if you've colonized say 20 stars, what disaster could possibly end your civilization?

(I think the most likely scenario is that we're the only civilization ever to have developed in the Milky Way. Everything else seems like it assumes a lot of additional stuff.)

View on HN

> if you've colonized say 20 stars, what disaster could possibly end your civilization?

Unfortunately, war with another civilization.

I mean, maybe. Honestly hard for me to imagine war actually going on between two interstellar civilizations. But even if it did, it seems like in 99% of all cases, that would leave at least one of the two civilizations still around. We're looking for explanations, in this hypothesis, that leave 98% of all time with no civilizations.

Maybe war between two spacefaring civilizations is too "easy". eg something like: throwing asteroids at ~the speed of light is necessarily a cheap thing to do once you're at that level, and everyone just dies.

Like if on Earth nukes were something everyone could cook up in their backyard in an afternoon, we'd all be gone pretty quick.

Not sure that really makes any sense though.

> Maybe war between two spacefaring civilizations is too "easy". eg something like: throwing asteroids at ~the speed of light is necessarily a cheap thing to do once you're at that level, and everyone just dies.

The Killing Star[0] and Flying to Valhalla by Charles Pellegrino are based around the idea that it's natural for a species to annihilate all other sentient species. The characters define three rules that an alien species may be operating by.

Rule 1. Aliens will believe their survival is more important than our survival.

Rule 2. Wimps don't become top dogs.

Rule 3. Aliens will assume that the first two rules apply to us as well.

[0] https://tvtropes.org/pmwiki/pmwiki.php/Literature/TheKilling...

Given the relative emptiness of observed space, im not convinced that a civilization A would try to annihilate all life but would maybe war with others in their light cone who threaten civA goals/expansion. If you can traverse interstellar space you can probably make home most anywhere further reducing the amount of potential conflict.

How likely does it seem that if you can traverse interstellar space, your civilization splinters over time and your potential for internal conflict just grows without bound?

If you can traverse interstellar space you are pretty much required to "live off the land" as you go and especially so once you reach your destination. This means you possess the ability to produce all of the energy, food, material, etc. required for a civilization to exist from what is present in either interstellar space or a solar system. If we put our sci-fi hats on we can imagine a perfect system of recycling and matter conversion that can keep a massive generational ship functioning with the only input being hydrogen scooped from the space it crosses. If you possess that level of sophistication then you really could live anywhere. That gives you plenty of living space with little motivation to pre-emptively attack others.

Spoilers for The Dark Forest and The Remembrance of Earth's Past Trilogy below.

In the book that the OP article is based on, humanity is doing anything and everything to prevent/defend themselves against an alien invasion happening ~400 years in the future. The character who coins "Dark Forest" theory in the book proposes sending a 'spell' (just a signal containing coordinates) to a nearby star, which is then amplified throughout the universe via "Sci-Fi science". This reveals the location of the star, and shortly after the star is destroyed by some comet-sized object moving at the speed of light. It's later revealed that some other civilization listens for broadcasts on every spectrum, decodes them for coordinates, then destroys the ones that seem to have actually been sent by intelligent life.

I thought this made perfect sense - why wouldn't another intelligent species do this if they possess the technology? I personally agree with "Dark Forest" theory and think that we should /never/ make first contact (lest we are destroyed), but if we were to attempt first contact, we should at the very least have a weapon like you described available to us first.

> why wouldn't another intelligent species do this if they possess the technology?

I think the only question we can ask here is "Would we do this if we possessed the technology?". We only have ourselves as an example of intelligent life.

You may be on to something there. Nukes aren't something that you can cook up in your back yard yet but it seems inevitable that at a certain level of technology they will be. The same is even more true for biological warfare.

Society probably only functions below a certain level of technological advancement before everybody dies to an onslaught of engineered diseases.

If the stars are reasonably close together a supernova would do it. Even a relatively distant supernova (like 30-40 light years) would likely render most planets inhabitable for a long time.

But maybe war is a territorial animal's instinct and once we have shaken up a bit more of our animality, we'd understand this makes no sense ?

If we can control resource, exchange knowledge and techniques, and reproduce automatically (for instance if we become small electronic machines rather than the current inefficient chemical process we are), "war" might probably sounds both ridiculous and totally ineffective, both to cull us if we're abstract enough, and to cull potential enemies, probably just as impossible to reach "physically".

OTOH animals evolved those instincts because they worked in the game-theoretical circumstances that competition with other animals.

Perhaps we can shake off many emotional components of war (which would make war an irrational option in many of the cases that our monkey brain would have been dragged into) but that doesn't necessarily mean that war itself would be eradicated

Animals are stuck in local maxima (betrayal in the Prisoner's Dilemma). A more evolved group might discover and be able to reach the global maximum (solidarity in the Prisoner's Dilemma). Imagine if tigers or sharks developed pack hunting, or the octopus became more pro-social.

Also, multi-species symbiotic relationships are quite common in the animal kingdom. It would be surprising if that weren't true at other scales (and if it were limited to the sci-fi trope of "worker species, soldier species, leader species").

I'm not saying it's not possible to find other equilibrium points. I'm just pointing out that there are more fundamental forces at play and it's not just because of our "monkey/animal brain".

Selective pressures that permit the emergence of cooperative behaviour require participating individuals to exhibit a variation in behaviour and those who cooperate result in having a higher fitness in the environment than those who shun cooperation. The selection effect operates on over the whole population and over times that are longer than the life span of an individual.

An individual that is implementing what ultimately will emerge as the winning strategy, may on average be better off, but it can (and it will) be also often worse off.

Depending whose existence you're optimizing for (individual or species) changes the framing of what is the optimal strategy.

An existential risk for a species changes the framing of what is rational to do quite a lot.

Ours always rot from the inside out.

> if you've colonized say 20 stars

This is the sticking point for me.

The rocket equation, energy being quadratic with velocity, and the impossibility of perfect efficiency (and, possibly, limits on material properties) constrain speeds.

That means it takes a long time to get between stars. A long time.

Which means if you venture between stars successfully, you're adapted for life in interstellar space. If that's the case, why would you go down the gravity well? There are lots of asteroids and comets to use in Oort clouds and between stars, and those down-well enviroments are hostile.

Reply on news.ycombinator.com