How many people does it take to colonize another star system? | Hacker News Reader

How many people does it take to colonize another star system?

popularmechanics.com

55 pointsarnauddri67 comments

A somewhat related question. How many people would it take to sustainably maintain current levels of technology if given time to prepare, the ability to bring all of our knowledge (but not realtime communication with Earth), and a reasonable starting set of tools?

Would a generation ship with 10,000 people still be able to build an iPhone when they arrived? A GPS satellite? Is it a matter of knowledge/ability to specialize or is it the economies of scale that make it possible to build compact high tech items?

It's less about the people and more about the resource capabilities on the ship. If the ship has machinery that can rebuild things like a chip Fab for example, and the knowledge to repair all said machines, it becomes more feasible. If the ship has no machinery to construct advanced machines/facilities even 100,000 might not be enough to construct advanced tech.

> even 100,000 might not be enough to construct advanced tech.

I think that's way too large of an estimate. As long as we could continue to access records of how we did things, and the planet had sufficient relevant resources, I bet we could bootstrap ourselves from having only primitive mechanical tools to today's tech in a few generations. Again, that's assuming the planet is relatively hospitable and has the correct resources available.

I'd assumed he was asking about "immediately on arrival", not "within a few a generations", but I agree with your assessment.

Not sure about the parent here, but I was certainly considering longer term. I would expect early on that there would be high tech tools and items brought on the ship or built form parts of the ship. Actually setting up local production from local resources (beyond what could be constructed on the ship) would probably take some time.

Longer term though.. is it practically/economically feasible to build and run a chip fab capable of building modern ARM CPUs for the needs of 10,000 people? What about the rest of the manufacturing chain for these sorts of devices? Or is the only reason we can buy a smartphone today for a few hundred dollars because of the economies of scale of building tens of millions of them on a 2 year replacement cycle?

Yeah you're right, looking back on my estimate I'm really underestimating humanity if 100,000 can't learn and build this stuff in the long term. 100,000 hungry and driven people could do a lot if survival was on the line.

Food and shelter would probably be a higher priority than smart phones, surely?

And I'm not sure 100,000 people is enough. You need the right people in the right place at the right time.

It's an interesting thought exercise, but as many of the commenters point out, the article's premise is a little ridiculous. With modern technology you don't need to send the entire population. The vast majority of the genetic diversity could be in the form of frozen sperm and eggs.

It's a pity they went that way, because there's a different framing that is still an interesting question: How far could humanity fall and still be able to recover? It's essentially the same problem, and it's a lot easier to imagine that we're talking about a situation in which there's no longer any technology. We consider the people geographically co-located, but it's not hard to imagine a pocket of survivors of whatever $DISASTER, either.

You have to start somewhere more specific than no technology.

Like, no steel to find lying around, or no one that knows how to make charcoal and that some dirt has iron in it.

Or does anybody remember anything about agriculture?

I feel like anything like that has to be predicated on not being able to find any book. Which is certainly possible, but I feel like $DISASTER will probably leave behind some libraries and books somewhere. The people would just have to be dedicated to learning the lost info from books + experimentation.

I worry that such an event would still be devastating. One fire was all it took to lose all of the wealth of Alexandria's knowledge several thousand years ago.

A Canticle for Leibowitz is a great sci-fi thought experiment on the subject. Having survived (barely) world nuclear war, a monastery seeks to aggregate whatever fragments of information they can (notably they mysterious note "Pound pastrami, can kraut, six bagels—bring home for Emma"), and try to rebuild society without inevitably repeating the great conflagration.

"No advanced reproduction technology" is adequate for this. Even basic reproduction technology is fairly sophisticated stuff, with the exception of "the rhythm method" and basic (if very, very annoying) condoms, neither of which will affect the answers given by this analysis as only actual reproduction events matter. We assume that people can survive and procreate, and the gene pool cares little for in what style they survive and procreate in.

I see from other replies there's a bit of a misunderstanding here. This isn't an exercise in what tech levels might be used to rebuild civilization. This is an exercise in how much diversity is required to be in the gene pool for the species Homo sapiens to continue, as at that level we're still reeling from the previous near-extinction event we experienced.

Indeed, even with modern advanced technology, we are still tied to the gene pool. Until we can more easily and reliably rewrite genes before the fertilized egg begins to reproduce we're still stuck with this problem. "Designer babies" remain science fiction... tantalizingly close science fiction, close enough that the ethics debates are increasingly less abstract, but still not here yet.

Replacement rate is a big factor. Highly advanced technology won't help much if the population doesn't procreate fast enough. Japan is a surprising example: profoundly high-tech, but nowhere near enough offspring to maintain the population (as in the entire country/culture/race is on track to disappear entirely).

reproduction rates are highly tied to culture, risk (high risk = more offsprings) and wealth. How that would look in the context of high tech space ships is rather unclear.

>Highly advanced technology won't help much if the population doesn't procreate fast enough.

Japan is profoundly high-tech because they have a declining population. They desperately need to boost the productivity per individual. Advanced technology is the only thing keeping Japan afloat.

Those were my thoughts as well., I wonder though how long frozen eggs and sperm are viable. Could you really rely on then for 2000 years?

"Whereas in the simulations, the larger populations were allowed to have only one child per couple".

This seemed a little strange to me. If you have only a single child per couple wouldn't you expect the population to at least half each generation?

I think this just means that the random number selected for children from a couple was allowed to range between 1 and N, whereas for the smaller populations, it is between 2 and N. It doesn't mean all couples generate 1 child.

People have children early in life. Even at that rate, the population can grow without bound. E.g. if people lived forever its clear the population would still grow.

Living forever is somewhat an exception. But even if people live forever there will still be a hard bound. Imagine a population of 8 people (4 couples). With one child per couple the first 4 couples will have 4 kids. These 4 kids will have on child per couple giving 2 kids. The 2 kids make a single couple which can have one more kid. The last kid cannot make a couple with anyone without someone having had more than one kid. So starting with 16 immortal people having immortal kids you cannot get a population above 15. (8+4+2+1=15)

So for a stable population in the long run couples need to be having on average around 2 kids each (assuming they are not immortal, if everyone is immortal then no kids are required for a stable population).

Of course if we take "couple" very literally then perhaps we might allow people to have as many kids as they chose provided they have each with a different partner (to form a new "couple"). This seems like rule bending though.

Without rule bending one kid per couple just couldn't work in the long run.

When 10,000 people are housed in one starship, there's a potential for a giant catastrophe to wipe out almost everyone onboard. But when 10,000 people are spread out over five ships of 2000 apiece, the damage is limited.

Whatever you do, don't go on the B Ark.

First of all, we need better engines. We need better engines and better probes to be able to investigate candidate systems up close. We won't send humans before we have thoroughly evaluated the environment and ensured it's, if not safe, habitable. It's OK if they take centuries to arrive, but it would be really great if they didn't. They could also be accelerated and decelerated at much more than 1G, something we would prefer not to do with a live payload.

Second, we need better engines, better robots and better manufacturing technology. Once the right planet is found, we'll send supplies and robots that can build the colony mostly from local resources. Hopefully, all that can withstand much greater accelerations than humans would.

Only then we can send humans, with human-rated engines (we can't do much more than 1G for any significant part of the trip) and a complete habitat that can sustain the population for the duration of the trip (as seen from the passengers - relativistics may apply, depending on our progress with the all-important engine thing)

So, before we have better engines (and get rid of the bureaucratic problems with nuclear reactors in space), it's really a waste of time to think about how large the crew should be. We can have that data if we build marginally better engines (yes, they are key) and colonize other planetary surfaces and asteroids. Eventually, some populations may opt to isolate themselves.

Also, don't forget we may end up learning a lot about genetics well before we can build a relativistic engine. It's perfectly reasonable to imagine we could reintroduce (or introduce, or remove) any genetic trait we want in the population at any time we need to.

250,000 kph isn't fast enough for you? http://en.wikipedia.org/wiki/Helios_probes

DARPA and NASA are working on it. http://en.wikipedia.org/wiki/Hundred-Year_Starship

What's needed is either a faster-than-light drive or the ability to cryogenically freeze people and bring them back once the spacecraft arrives. http://en.wikipedia.org/wiki/Faster-than-light and http://en.wikipedia.org/wiki/Alcubierre_drive

If we can't bend space-time (using something like a worm-hole) or travel faster than light then there will never be any communication between the 2 civilizations.

Wouldn't it be much easier to just mine the planets we have already and build artificial planets or massive space structures out of existing planets and resources within our own solar system? Yes, the sun will eventually burn out but that's not an issue that our generation will face more than likely.

Where should we go? http://en.wikipedia.org/wiki/List_of_nearest_terrestrial_exo...

> 250,000 kph isn't fast enough for you?

No. 250K kps would be more adequate. Faster == better (but we'll need good ablation shields).

> What's needed is either a faster-than-light drive or the ability to cryogenically freeze people

If you manage to get close to the speed of light, you will, from the crew's perspective, be FTL without inventing new physics. Freezing the crew is also an option, but keeping everything going for very long periods of time is challenging in itself.

> there will never be any communication between the 2 civilizations,

We still have radio. No way to phone your friends, but, still communicate, share news, share knowledge etc.

250K kph is nowhere near fast enough, by several orders of magnitude. That gives us a 4k year journey to the nearest star system, which AFAIK is not thought to have any habitable planets.

And that's a tiny probe, close in to the sun. Leaving the solar system with that kind of velocity is a whole different problem. Voyager 1 is leaving the system, doing about 17 kph, reportedly. As far as I know, we don't have anything right now that can do much better than that.

According to everything I've read, sending anything at all out of the solar system at a high enough velocity to get to another star system is way beyond any kind of engine technology we even have on the drawing board. We could probably build a fission engine if we really wanted to, but even that's still orders of magnitude less than we need. Much less propelling an actual starship, meant to contain hundreds or thousands of humans and keep them alive and happy for the journey, at those speeds.

I do believe that we'll do it someday, but it's going to require propulsion technology that we can only imagine right now. Anything like FTL or wormholes or whatever is pure hand-wavyium at this point.

Voyager 1 is traveling at about 57,000 kph. http://solarsystem.nasa.gov/missions/profile.cfm?MCode=Voyag...

The 250k being fast enough remark was just a joke.

Yeah, space is inconceivably massive, that's why my main recommendation was that we focus on staying in our solar system for now. Autonomous robots can mine and build huge structures in space for us to expand to, or I guess we could build them on Mars, either way.

Many NASA scientists don't think that a warp drive is impossible http://www.space.com/17628-warp-drive-possible-interstellar-...

http://www.space.com/9882-warp-drives-wormholes.html

We can make antimatter, we can see trillions of miles away, we can talk to people on the other side of the planet instantly, we have computers that can simulate nuclear weapons, we have nuclear weapons, we can connect and talk to the human brain, and we can even theorize with pretty good certainty what happened to start the universe, a warp-drive or worm-hole isn't completely impossible in the near future.

Humans are not too far off from becoming gods. We can create life, we can put life on other planets, we can even improve ourselves by fusing with machines, shits crazy these days. [0]

That site is awfully vague about exactly when it was travelling at that speed. Every link I can find says that the speed of Voyager 1 right now, having left the solar system, is 17kph. It was travelling faster earlier, but getting away from the sun eats up velocity.

That is an interesting link about Alcubierre drive work, but as far as I know, we still don't have any idea how to get the exotic matter required for it.

17 km per SECOND, not hour, if any site says hour then it's wrong.

Here is Voyager 1 and 2s official website, you can see the distance being updated live, you'll notice that it increases very fast. http://voyager.jpl.nasa.gov/

Make sure you are looking at distance from the sun, not Earth, the earth travels faster than Voyager 1 so sometimes it will actually be getting closer to earth.

We do know how to create antimatter, just not how to create amounts large enough to be used (the LHC generates it I think). I'm not optimistic about traveling faster than light anytime soon, but it isn't 100% out of the question.

And if an alien civilization captures one of our spacecraft: http://voyager.jpl.nasa.gov/spacecraft/goldenrec_more.html

Ah, looks like I misread things. 17kps makes a lot more sense - 17kph is like bicycle speed.

We can create anti-matter all right, but AFAIK, that isn't the exotic matter required by an Alcubierre drive. Anti-matter could in theory be used to create the most efficient rocket drive possible, but apparently even that isn't all that great. According to this http://www.nasa.gov/centers/glenn/images/content/84509main_w... sobering chart, even a theoretical anti-matter rocket would require 1 million kg of propellant to send a small capsule past the Centauri cluster in 900 years, without counting stopping. Going back to chemical rockets, there is apparently not enough mass in the entire universe for that rather underwhelming plan!

I don't know that FTL is out of the question, but apparently it is impossible to have it without time travel. I'm not looking for any of that to happen tomorrow, and I don't think anybody alive now has a clue when anything like that might be ruled in or out for sure, but with the right theoretical breakthrough, a lot of interesting stuff could potentially happen very fast.

If you could invent a starship, you could also invent a new human, designed for starting civilizations. Calorie-efficient, hardworking, has litters of pups for rapid population growth, early maturity (8-10 yrs old), long-lived, prodigious learning and memory, adaptable and happy with rote work.

if you are doing because you believe in the value and beauty of human society, you wouldn't want to genetically modify their personality...

Who's personality? Yours? Mine? Why not this new guy, who's really very nice; nicer than most people we know. Because we made him that way.

I believe that a child's first program is a beautiful thing, but I still want them to grow. Acknowledging something has value doesn't mean you think it's perfect.

Very interesting article. There are tons of ethical and practical concerns above and beyond the genetic situation, which itself might be fixable well before a ship capable of such a journey was ready.

However, what I found weirdest about the article was not the topic itself, but this line: "He calculated the trajectory of each population 10 times, then averaged the results. (With one exception: The starting population of 40,000 is so large that it takes 18 hours to complete each simulation, so he calculated that trajectory only once.)"

Even without considering the possibility of running the simulation on 10 colleague's computers or spinning up cloud VMs or any number of workarounds, how rushed was this project that a week's worth of 18 hour MATLAB runs was considered too much work?

That stood out to me too. Maybe they figure they'll have enough time to run some more simulations between now and 2350 when the starship is built, so it's not worth wasting a lot of time on what is mostly just a fun thought experiment.

Related- The 1 kg Starship, with a lively discussion in the comments, from cstross among others.

http://www.centauri-dreams.org/?p=30313

The problem is more-daunting than stated. The mechanics of applying the energy it takes to accellerate, and decellerate, a plausible generation-ship to two orders of magnitude higher speeds than currently possible is multiple technology horizons away. Bio-engineering ourselves into forms required for millennia or tens of millennia of travel is probably much closer than acquiring that amount of energy. Indeed by the time such a ship could be built, the "human" form may be more distantly related to us than chimpanzees are.

But far before either of those happen we will have an increasing amount of either remote controlled robots or self guided robots exploring on the fringes before us.

That's also true. And another reason to stay away from sci-fi inspired prognostication, like a lot of comments here where space ships five orders of magnitude heavier than anything yet built are blithely assumed to be possible. Most of it requires magical solutions to very hard problems. David Brin is one of the few writers i have seen take on the "it's really hard, and insanely expensive, to get anywhere" problem and make a story based on that problem. The most plausible future doesn't have animals that look like us running around in it, never mind traveling to other stars. And that makes it hard to sympathize with, or even imagine, the protagonists of stories about the far future.

Very interesting, but this raises a point in my mind. If a colonisation trip takes several generations to reach its destination, would the human rights of the descendants of the original travellers be infringed?

They would be conceived, born, live out their lives and die without ever living anywhere but the ship (unless they are part of a generation lucky enough to reach the destination), and they would have no choice in the matter.

If a couple joins a colonization movement and moves to the middle of nowhere, with limited chance to survive (make your time) outside the colony, in a land occupied by dangerous animals and savage heathens - say, New England in the early 1600s - would you consider the human rights of their children and grandchildren to be infringed? Isn't the difference just a matter of degree?

(n.b. actual savageness of heathens is left as an exercise to the risk-averse potential colonist)

I think our understanding of human rights has evolved since the 1600s. This is a very interesting ethical question.

At the level of technological sophistication required to send a probe to another star system, you could probably sequence/modify the genome of the eggs/sperm to produce humans that have a lust for exploration and pioneering.

Now it's just a question of whether genome modification is ethical.

Not quite: the 20 generations that are born and die on the ship don't get to explore anything. You'd want people content to live in a crowded can.

In a related point - what would the cultural mindset of the final descendants become, both individually and collectively?

They would have no shared experiences with those who first set off.

Ideals could be passed down, but with cultural evolution through the generations, would their priorities or preferences even be remotely similar?

Many science fiction stories written about this. The most popular theme is the breakdown of civilization and an ignorant crowd of savages set down on the destination world. Other authors have them undergoing violent revolution a dozen times over the centuries, recapitulating human history. The resulting world is populated by whatever form of government is extant at the time of arrival. Still others imagine them passing serenely by the destination, no longer interested in their progenitors plans and seeing no other future for themselves than perpetual ship-board life.

I would think it would be similar to living during war times, in terms of restriction. I'd also imagine that the kids would not really know better if they haven't tried anything else.

> I'd also imagine that the kids would not really know better if they haven't tried anything else.

An abused child may consider abuse perfectly normal and even miss it if it ceases, but that does not make abuse tolerable.

The following idea comes from a SciFi role playing game Traveller™:

The maximum sustainable techlevel of an economy equals the logarithm base 10 of the population. Even if a population of 10k-40k people is genetically healthy, they would fall back to to techlevel 4 or 5. They would be just able to sustain a technology of medieval times.

I suspect there is a tipping point. If there is sufficient automation and information available, a very small number of people could potentially reproduce/rebuild a full high-tech society in a short amount of time. Vinge's "Marooned in Realtime" engages in similar speculation. IIRC his requirement for preventing inbreeding was something on the order of 20 people -- much lower than the parent article's 150 bare minimum, with 10K being more realistic.

I would think if your technology is advanced enough to send a spaceship for a 1000 years in space, you should be able to manipulate the human genome to avoid "inbred" diseases.

First let's start by going back to the moon or even Mars ...

We have the technology now to get a long ways towards manipulating the genome to avoid disease, just combine an extensive screening program with in vitro fertilization.

It would be massively expensive (and of course would only work for genetic diseases that we understand). I guess it would also be a controversial endeavor.

I would argue that we know a lot more about the physics and engineering required to build a generational ship than we do about the biology to cure rare genetic diseases.

I would bet that if global warming doesn't destroy us before, we will master inbreeding before we're able to go for a 1000 years space exploration tour.

You don't necessarily need a perfect understanding of biology to do this. Just avoiding homozygotes for any rare genetic variant you don't have flagged in your database as well-understood will go a long way to avoiding in-breeding issues.

The number could be significantly higher, since genetics might not be the limit at all. The true question is how many people it takes to maintain the complete production line of our computers, from dirt and water to boards and chips.

Anybody interested in interstellar colonization topic (and in particular the question of how to get hundreds of thousands of colonists there) might also want to read "Neptune's Brood" by Charles Stross. The society and mechanics he describes are so far the most realistic I have ever seen.

Don't want to spoil anything, but according to him, the squishy biological stuff might not be up to the job.

This is a bit silly. Yes, genetic diversity is important for surviving viruses and other pathogens that come from Earth. Because we have evolved here, we can handle the other conditions of this planet. But it's not a guarantee that we'll survive the subtle changes on other planets - the gravity, magnetic fields, radiation, light, composition of the atmosphere etc etc.

A good argument for designing the people that will be sent to colonize.

Or simply designing the immunization shots?

Creating an artificial uterus and sending that device with frozen sperm and eggs would be more efficient.

I just think that it would be impossible to calculate the risks if real human beings would be sent on such a journey.

So all the children would then be educated by a robot ai?

Unrelated yet more relevant question:

How many people does it take to properly care for ourselves and the planet we live on?

According to the Bible two and a bunch of animals.

It's debatable whether their descendants (or those who claim to be their descendants) can build an advanced civilization.

Don't be silly. According to the Bible, eight and a bunch of animals. (Noah, three sons, and four wives.)

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