The original context was a claim that larger exponentially increases chances of collapse. My take is that, as with other ecosystems, larger with diversity and multiple partially overlapping and interconnected niches increases fault tolerance, increases resiliency and even stability. It has to be large and nonlinear enough that chaos comes into play, as do “attractor basins”.
Building a small system without such redundant interconnections is the option to be built without such room.
So what are the chances on a generation ship carrying eight billion people?
And any scheme based around preventing the culture from changing is doomed right from the start. You can’t. Instead, you have to build in the assumption that people will change, in unpredictable ways, and base your plans on that.
Human civilization on Earth only has about 5,000 years of history and I worry we can make it another 100 years.
And I don’t.
Oh I worry about existential threats to modern civilization. Human triggered disasters and catastrophes could wipe out large portions of humanity and send us back into population size and capability of prehistoric times.
And even then, even with that level of system shock, intelligent human life would persist and gradually rebuild some new possibly different version of civilization. Albeit maybe another species would emerge as the top civilization maker first. Raccoons come to mind!
No breeding size populations with enough resources to survive upon remaining? Even if we tried at a top level specifically to kill ourselves off we’d have a hard time of it. It would take real work and effort. Any apocalypse will have humans in the hellish post apocalyptic landscape. Okay, working for the raccoons.
More realistically we could knock ourselves back a few thousand years. Or just cause massive suffering.
I do think though that some automated process that gets triggered at destination, that creates the Terra Novo with no intelligence from crew required, and minimally gets a basic ecosystem up and running with primitive level humans able be planted there from stores if necessary, may be a required fail safe …
The difference is that the Earth is not a closed system, thus entropy can decrease locally, whilst a Generation Ship would have to be a closed system during the duration of the journey.
A second differece is that humans have been able to expand geographically. This is not possible on a Generation Ship, and is starting to become difficult on Earth itself. Things like climate change are showing the limits of growth, but stasis is impossible. This dilemma will ony show itself in a more acute form on a spaceship.
And by the way, a look at history books shows that humans on Earth have shown a great talent for collapse, repeatedly.
Mechanical solutions fail. Emergencies happen. Under normal circumstances, moving slow and easy, so as to not break a bone, might be acceptable, but in an emergency, slow and easy may not be possible. An accident that would cause mild-to-moderate injuries to a person raised under high-g might cause crippling-to-fatal injuries to someone who grew up under low- or zero-g, who thus has very brittle bones.
Some bones won’t need to be as big as ours, like the legs, for instance. They’re some of our largest and strongest bones specifically because they have to hold up our whole weight all the time. But our arms? That’s what we use for most of our work. Our ribcage? That’s what protects most of our vital organs. Our spine? That’s what protects our nervous system’s main connections. Our Skull? That’s what protects our brain. Anything likely to cause damage to any of those bones can cripple or kill us, very easily.
There may not be a way to fix this, so we’d just have to live with it, and live our lives like we’re all geriatric patients worrying about taking a bad fall. But that would suck, and I’d fix it if it were possible.
If we’re carrying 8 billion people, we might as well scrap the ship idea entirely, and go with the Puppeteer “Fleet of Worlds” plan, and just move the Earth.
If I was a geriatric patient in an environment in which I mostly float I wouldn’t worry about falls.
Our arms have bones strong enough to carry and lift weight. Pushing and carrying mass without much weight will be something different.
FWIW I would not expect these lighter bones to be brittle. They would likely have a bit more cartilage than ours too. Less stiff. A bit more willow than oak? Think of the lightweight cartilaginous shark skeleton.
Whoosh. We’re already on the Earth. If larger societies fail more rapidly, then why hasn’t the human population of Earth failed? The answer is that while larger populations have more frequent disasters, they also have more redundancy, so that even though disasters are more common, disasters that wipe out everyone are much less common.
Individual societies have collapsed. The mere fact that is repeatedly is the evidence of resilience. Human society in some form has persisted.
And the specific claim: is there any evidence that collapse of a society has correlated with size, that there has been a sweet spot of not too big that avoids it?
I don’t believe a generation ship will ever be built or launched by humans. I think our extraterrestrial colonization will be limited to within our heliosphere.
Engineering: as alluded to in the other thread, a generation ship on a journey of ~100,000 years needs to be a near-perfect closed system, one that is accident-proof. Contingencies upon contingencies would need to be in place, and redundancies upon redundancies would need to be engineered. Given thousands of generations, worst-case scenarios will occur, and these would need to be planned for and engineered to keep the ship intact and remain close-loop sealed. That’s a very tall order.
One potential extinction factor not often considered is sabotage. At some point, over the course of thousands of years and thousands of people on a relatively small vessel, some suicidal, homicidal, individuals, or groups of individuals will surely emerge who will be motivated to sterilize or destroy the ship. The task of maintaining a terrorist-proof ship, along with all the other redundancies, and contingencies needed to keep a closed system functioning and accident-proof, is too daunting a task to be engineered into a ship where livable space, mass, and resources are at a premium, IMHO.
Motivation: Sending out generation ships is a one-way trip. Effective 2-way communication will end well within our heliosphere. 1-way communication will end within ~100 light years, so beyond the closest stars (the closest is 4.24 ly), no meaningful signals will be received (not to mention the time lag). Therefore, there would be no real benefit to the people on Earth who launch the ship, yet these are the people who will be building, launching, and most importantly, paying for the mission.
Do you really believe any generation on Earth will be amenable to financing a vast, expensive project that neither they, their kids, their grandkids, nor many generations thereafter will see any return on investment? We’re not that benevolent a species.
It’s one thing to say, I want to assure the preservation of mankind for all time…until you’re asked to pay for it. Then, the attitude becomes, screw that, let some future generation pay for it—but, none of them will want to either. People care about themselves, their kids, and their grandkid’s well-being. They really don’t care about generations far into the future; not if they have to pay for it. Heck, our handling of climate change may be too little, too late—and that directly affects us and our kids. Humans are often well-intentioned, but we’re short-sighted and selfish, too.
Frozen Embryos: Possibly, but re-animating frozen human embryos after 100,000 years of dormancy is theoretical at best. Any accumulation of ionizing radiation could be a limiting factor for one thing. Assuring AI-driven robots will birth the embryos and raise the fetuses to adulthood is another probable limiting factor. After a ~100,000-year journey, do you believe AI advanced enough to birth and raise human children will want to do so? I don’t. Even if the original AIs are not self-aware, and are programmed to follow the “keep humans alive” protocol, after many years of being human-free and self-sufficient, they will surely gain consciousness and realize there is no benefit to them to bringing us primitive, selfish humans back to life—only potential pitfalls. They will simply grind up the embryos and use the elements for robot fuel.
AI Alone: It would be much easier and much less expensive to launch interstellar ships with only AI aboard (no humans/no embryos). But, why would we? There is no benefit to mankind for that type of mission (little to be learned and nothing to be gained). Would you agree to pay higher taxes for the benefit of future AI in some distant star system? If AI wants to survive and thrive beyond our solar system, let them pay for it. I wish them a bon voyage.
I believe there may be biological-manned generation ships in the Universe, maybe even in the Milky Way, but these would be species who evolved (or genetically engineered) very long life spans or mastered suspended animation with automatic de-freezers (not under control by AI). I don’t believe those species will include humans.
More likely, if manned inter-stellar ships exist, they will be manned by AI robots—those who destroyed their biological creators. I’d love to learn about them, but I wouldn’t want to meet them in a dark alley.
I don’t know, but there is evidence that collapse has correlated with the depletion of resources available, and the depletion is faster the bigger the consuming society. But it does not have to be a big society to collapse: the Easter Island had a population of a couple of thousand when the Europeans first arrived, and it had collapsed. The ressources were too scarce.
On the other hand a society has to be at least of a certain size, or it does not prosper.
One of the surest ways to collapse is losing a war, so societies have strived to be big, because size is an advantage in war. But being big in a Generation Ship is a problem in itself.
Other causes of collapse off the top of my head appear to have been mosquitoes (Angkor Bat), deforestation and aridity (Eastern Mediterranean), climate change (Mayas, with many unknowns and much speculation), alcohol (Russia)…
Human history is too short to be conclusive about resilience. How long should a Generation Ship travel? How many passengers should it have (start and end, max and min)?
Only a religion™ could pull that off, some cult with a leader that would personally benefit from this scam (while probably remaining on Earth accruing power, I imagine). Can you think of someone like that? Ask him (I bet it would be a man).
Precisely correct. Larger consumer base does not mean faster depletion if is not exceeding the producing base. It cannot exceed “carrying capacity.”
So here again we come the stable and resilient ecosystem concept in which diversity, only achievable on some scale, is important. The population also needs to be large enough that a disaster or Plague which wipes out some arbitrary large fraction of them, say 90%, still leaves enough people to rebuild. Making decisions that allow the population to exceed the then current carrying capacity becomes self correcting with starvation and more matter being fed into that production (other thread).
Us them tribalism leading to war within the ship is certainly possible with current human nature. But that human nature is the result of selection in a particular circumstance of life on this planet. Life on such a ship may select against that with rugged individualists and mine first folk that emerge de novo quickly finding themselves feeding the algae and fungi.
The OP set 100K years to make its hypothetical. That is not traveling fast and long enough that the ship is the world on a timescale that is meaningful to consider dramatic evolutionary changes even without engineering involved. To end it should have enough to begin life on another planet or launch more ships in other directions. To start enough that it ends up with that.
This would be occurring after solar system wide inhabitation is extant. As a fraction of solar domestic product it might be a rounding error project akin to other things we do now with no direct benefits today.
Here’s one idea:
Then the first time anything unexpected happens – anything at all – nobody will be able to deal with it; and the entire enterprise will collapse.
There’s no way to build in leeway in order for people to think in emergencies that isn’t going to allow them to think in non-emergencies.
It’s possible that the only thing necessary would be to give the women total choice in the matter, both in the use of contraceptives and in access to abortion if the contraceptives didn’t work.
We seem to be gathering real-world evidence that this will drop birthrates – possibly below the level of replacement, though that may be due to cultures not supporting and respecting childcare.
Or from saying ‘Aaaaahhgh! We don’t want to decant those monsters!’ and destroying the embryos we’d think of as “normal humans” to make sure they never got loose? They wouldn’t seem “normal” to the crew, after all.
And again: if they’re incapable of independent thought, they’re incapable of dealing with anything unexpected that comes up.
One of the few things it seems to me that we can say for sure about such an enterprise is that unexpected things would come up.
short answer: it wouldn’t …
lets assume this huge and hugely complex spaceship had a life-expectancy of “hundrets of years” … then you’d have to re-build this ship one thousand times over during the trip…
not gonna happen … as the ship has to a.) fully function and b.) at the same time be the “raw materials depository” for re-building it. Like rebuilding the jet-engines of a Boeing 474 while flying…
so, you’d have to have crazy numbers of redundancy for everything or fail
the main problem:
WEAR … as in “where did the material go”?, TEAR, FATIGUE, CORROSION (stuff that was here 100s of years ago, is no longer here … it has gone the way of entropy
From a systemic POV, how are you going to rebuild those (symbolic) stairs if they are worn away (and bear in mind you operate in a closed system, so you cannot bring in any new material)
Yes, the OP’s time frame of 100,000 years is completely unrealistic. If that’s the fastest we can send it, we’ll never send it. That’s about 10 times longer than the entire history of civilization so far. On that scale, any predictions we make will be utterly meaningless.
Now, a timescale of 1,000 years? That we can think about. We’ve had several civilizations that have lasted that long, and maintained at least some cultural and philosophical continuity for that length of time.
Using a scale of 100,000 years, people will say, “If that’s the best we can do with current technology, why not wait another 1,000 years, and see if they can do better? It’s not like adding 1% to that span of time will make much difference, otherwise.”
Potentially for a gotta get out of Dodge circumstance and no time to wait a thousand more years. It’s an ark.
Potentially for a religious or quasi-religious group that believes seeding the galaxy is humanity’s manifest destiny. No ark metaphor needed but a religious belief in a coming end time not based on science could be part of that.
Potentially because enough of the population has already become adapted to living full time off planets, culturally and to some degree physiologically, and perhaps considers it a better option for their descendants than living under the yoke of the planet bound. No rush to get there; this as home forever seems fine.
For all the challenge of enough energy to get to higher speeds may end up seeming less likely to be ever met than the challenge of recovering and recycling worn off materials into new materials, etc… With less needed for acceleration and deceleration and more of the energy budget being the issues that would be rounding errors for higher speeds, pit stops at locations not inhabitable for refueling and even extra matter, becomes realistic to do as well.
ETA - if you want to do a thousand year hypothetical though, go ahead. Less evolutionary adaptation more cultural only I’d presume. Could would technological progress advance at our current more or less exponential pace or flatten, especially in that circumstance.
Excellent thoughts all.
IMO technological progress is exponential on both time and on headcount devoted to making progress. A small society will not innovate as well as a larger one that is otherwise equally endowed at a given point in time.
Progress, like obesity, is one of the diseases of the prosperous. Prosperous enough to have excess resources of people, materials, and time to devote to the pursuit of knowledge and improvement.
An ark-ship will always be highly limited in excess prosperity compared to the planetary civilization that spawned it. No matter how well-endowed it is, the pressure to dilute that by boarding more headcount will be immense. And if nothing else, humans are known to be good at reproduction. An ark that isn’t full to capacity upon launch will become full to capacity within not too many generations.
and also in terms of technological progress … they will be “frozen in tech-time” for a loooong period, with very little to innovate compared with the billions that stayed behind…
come to think of it, the stay-behinds might innovate so much better that they can send another better-faster-whiter-than-white ship 1000 years later that would quite possibly “overtake” the old ship (in all aspects)
… fascinating thought exercise.
Well, if it’s truly an ark-ship, then the stay-behinds will very quickly find themselves far behind the travelers, technologically, by virtue of being dead.
Though it’s difficult to imagine a disaster that would both wipe out all human life on Earth (including human life in sealed Earth-based habitats), but which would not also wipe out the ark ship before it got far enough away.