I personally suspect the engineering challenges might pale next to the challenges of political organization.
Quite simply, the continued human expertise and organization necessary to manage and sustain such a system is far, far beyond anything we have today.
We can't even manage to globally reduce CO2, and the recent government responses to coronavirus have led a lot to be desired, to say the least.
Just because you put people up in space habitats doesn't mean they become any less power-hungry, any more cooperative, or any more peaceful.
You say we'll have the engineering in 1,000 years, and I could buy that. But read Aristotle's Politics from 2,400 years ago, which is concerned mainly with political stability and revolution, and he might as well be describing people today.
I'd like to see us manage "spaceship earth" a helluva lot better before I have even the remotest faith we could manage space habitats politically. Heck, we couldn't even manage Biosphere 2, remember?
I get your concern but the differences are significant.
1. Habitats are mobile. If you don't like the neighbours you can up and move, something not possible with geography on Earth;
2. Land area is essentially infinite, not so on Earth.
> We can't even manage to globally reduce CO2
On the contrary, excessive CO2 is, at least in some context, a remarkably simple problem. We can extract CO2 from the atmosphere and make fuel. It just doesn't make any sense to do it because we need to burn fossil fuels to power the process.
So all we really need is a power source that's cheaper than fossil fuels. There are two obvious contenders for this:
1. Solar power. Estimates I've seen are that an orbital collector can be about 7 times as efficient as current Earth-based solar collectors.
2. Fusion power. Personally I'm not yet convinced if hydrogen fusion is viable. There are of course other proposals. We shall see.
You'll note that I don't include fission. It's an unpopular opinion on HN but until we have a good story for fuel and waste processing then this is a nonstarter.
That relies on the assumption that people within a single habitat wouldn't want to separate for whatever reason. Nation within a nation. It already happens on Earth(see: Catalonia, Taiwan, Hong-Kong, Silesia).
As in trade is very essential for growth. Both of goods and ideas.
Mobile? Are we talking O'Neal Cylinders here? While yes, technically they will be mobile, I highly doubt the reaction mass requirements to actually move a constructed space habitat on the scale of maintaining as near to self-sufficiency as possible a city size population would be terribly practical, especially if everyone was doing it wantonly.
Keep in mind the effect as of late with Moore's Law in processors, and realize that the same phenomena is likely to happen with spaveflight in that yes, the technology will scale in capacity, but a great deal of that capacity may be expended in rendering the technology "more accessible" to the less specialized consumer as opposed to remaining in a state where you're actually optimizing for maximum throughput theoretically possible.
Cars/motorcycles would be another example of the same phenomena I'm trying to get across in that we're trading technically superior performance of the motorcycle (maximally efficient, yet relatively hard to control and severe to lose control of) vs. The relative safety and friendliness offered by a car to an less skilled user, even if lugging around all the extra metal eats into the overall efficiency of attaining movement of small packets of material from point A to point B via motion attained through internal combustion processes.
Never mind the political issues. I fail to entertain enough optimism to realistically expect even getting beyond the ISS-like stage of space habitation within my lifetime at the rate we're going, and fully expect climate/ecological breakdowns to start creating too much conflict to really keep us moving forward in a cooperation friendly regime.
I'd love to be proven wrong though.
> On the contrary, excessive CO2 is, at least in some context, a remarkably simple problem.
I would argue that even though we have the technical skill, the fact we do not have the political capacity is a significant problem.
Given where humans came from, I’m sometimes surprised that our political thought processes functions at all on groups as large as cities, never mind nations or the plant as a whole. While I would like to hope that scaling it to the size of a Dyson swarm or larger would be fine, even at the level of one planet we do keep repeating cycles of genocides followed by people saying “never again” followed by more genocides elsewhere.
Waste processing in space? Just give it a slight push in the direction of the sun (or whatever the right direction is taking in consideration gravity) and forget about it.
That's not how orbital dynamics work; a slight push in any direction won't change the orbit enough for that thing to not be a problem anymore.
To make something fall into the sun, one needs quite a bit of delta-vee, which means energy. However, if the thing isn't in any hurry (and I imagine waste isn't), one can simply attach a solar sail with a tiny computer for steering it, and let it brake for the next few thousand years.
(Kerbal Space Program should be part of school curricula)
[1]: https://www.reddit.com/r/askscience/comments/5lt50r/why_does...
You don't need "a system" for doing this. You only need one. 9,999 of 10,000 habitats could be staring into their naval, but the one building more will still be building more. So, I think you ought to flip the intuition around; it's not a question of keeping everyone on board, it's a question of what it takes to extinguish everyone's ability to do this, which, once it gets going, would basically amount to "a local supernova".
"I have even the remotest faith we could manage space habitats politically"
Again, I think maybe you're envisioning a world in which all the space habitats are just peacefully co-existing... but this is not a necessary precondition for them to exist, or propagate. Yes, they'll war, and they'll split, and they'll join into groups, and there will be diversity that makes the current diversity on Earth look like boring homogeneity, because there won't be such a strong force pulling people back towards a single species mean. It doesn't have to be utopia to exist.
It's not about habitats coexisting with each other or not, it's about them imploding internally because people develop factions, compete for resources internally, threaten brinkmanship with critical systems, and eventually someone goes too far -- like people do all the time in countries all around the globe today.
Except a company can go bankrupt and a political regime can be replaced without all their employees or citizens dying in the process, because none of them are responsible for maintaining earth's life support.
But not all of them. And the ones that survive have the opportunity to learn from the ones that didn't.
That's less different from Earth than you may think. We've witnessed entire countries collapsing even in the last few years. If it wasn't for Earth providing free air, reasonably cheap water, and not-that-difficult food even when your local political system collapses, nobody on Earth would even consider switching their country to run on Communism; rather than merely killing dozens of millions of people it would be witnessed as bringing total extinction to anyone who tried it.
Basically, evolution doesn't stop.
How often have I talked with people and mentioned, that in terms of social behavior, we make such slow progress, if any. If we could end human greed and other bad things, how easy it woule be for us to go to space. If money did not count and all would work for a great goal of advancing into space, we would be there already.
What many call "human nature" (which I do not believe) is what holds us back.
Those seem to be in conflict to me. I do agree that human engineering has developed far faster than human politics, but I think we need to just accept that this trend will continue.
It's pretty easy to imagine a minority of administrators on a space habitat decide they'll take some critical system hostage unless they get a bigger share of whatever they want because they think (perhaps legitimately) they've been the victim of some injustice... overplay their hand, critical system fails despite nobody actually intending it, millions of people in the habitat die. Or a million other ways for disaster to happen because of human reasons, not engineering ones.
Here on earth, even when societies devolve into civil war and massacre (e.g. Syria the past few years), at least they don't destroy the earth along with it. But with a space habitat, even a partial breakdown of order easily means everybody can just die.
So let me be clearer: I wouldn't just "like" to see us manage Earth better first. My point is that this may very likely actually prevent space habitats from being viable at all. "Accepting that this trend will continue" doesn't mean we'll make space habitats regardless -- it means accepting space habitats might not ever be thing (no matter how possible the engineering is), unless it ever happens that we first make enough massive progress in our forms of political organization and cooperation as well.
[1] Not a high bar, and not by much. Nevertheless, we are still (barely) here.
Modern encrypted spread-spectrum digital radio would have looked like random noise until quite recently. I'm not sure if you'd pointed all the technology and all the brilliant minds that existed in 1930, at a modern cellular tower, that they'd have recognized the signals to be coming from a technological civilization.
In another century we'll no doubt be hugging the noise floor even more closely. It's not hard to imagine that even if alien civilizations are broadcasting omnidirectionally all around us, that we're simply too primitive to bother targeting with a message. Why waste the effort when you'd be able to communicate so much more information, and more efficiently, by targeting just a slightly higher baseline of receiving technology?
Topics like this are discussed in Stanislaw Lems, Masters voice novel. A really good read.
Then using your Drake equation variables calculate how many are within those couple decades at any given point that you can see.
The hard part is deciding if it's natural or artificial.
The converse: any life out there trying their best to communicate with us, beyond 600 ly... we wouldn't realize it even if we happened to catch (what's left of) the signal.
Doesn't that depend on how large the receiving antenna is, because the larger the antenna the smaller the source angle you can focus on and the less background radiation will be in that source angle ?
~5% of the universe is made of the stuff that you, I, a cloud, and the sun are made of. We understand this stuff very well, in terms of cosmic scale stuff.
~20% of the universe if made of dark matter. We know that this stuff falls down and really doesn't do anything else. Does it interact with itself, with us, can we make sandwiches out of it? No clue.
~75% of the universe is made out of dark energy. We know that this stuff makes other things ... fall up (?). Well, kinda, maybe? We're totally at a loss as to what the super-majority of the universe is, let alone what it is doing, or what we can do with it.
Presumably, if there are other intelligences out there, they may know if they can do anything with the other ~95% of the universe and they may be making it into burritos or something. We're a long way away from concluding anything about anything.
2% of the human body is the brain, and while poetry is written about other body parts, the brain is the one doing all the writing.
Atoms are something like 0.05% electrons, but the interactions and behavior of the electrons account for almost all of the interesting parts, and with notably rare exceptions, the nuclei might as well be point charge/masses.
Just because there is a lot of dark matter and dark energy doesn't mean it will be particularly interesting in the long run.
Just in mass. In volume(orbitals), electric charge, importance for chemistry, the proportions are way different.
I have always thought that this would be a much more efficient way of living off Earth. Sci-fi wants us to believe that we can teraform planets. All they ever talk about are the atmosphere generators. However, they never address the reason the planet didn't have an atmosphere to begin with. To me, the research into generating artificial magnetic shields is the place to be. Generating those fields the size of a planet will be orders of magnitude more difficult than for smaller sized ships.
Given or current sample size of 1, clearly we can.
It's the part where the teraforming produces a more habitable planet that we haven't gotten down yet.
But hey, this is only or first attempt!
In my view, given that we can do this, it is not unreasonble to assume that one day we will know enough to be able to tweak a planet's habitability in the opposite direction, or in other words, make an inhabitable planet habitable.
Aren't those the same thing? Shouldn't this be "make an uninhabitable planet habitable"?
The Earth's magnetic Van Allen belts deflect most of the sun's nasty radiation streaming at the planet. These belts are created by the molten iron core of the planet. Mars no longer has this magnetic shield, and the sun's radiation burned off the atmosphere. If we generate new atmosphere, it will just get burned off again unless we can generate some way of deflecting that radiation.
If we you can create an atmosphere it should last for a long enough period to be worth it, heck it might outlast humanity.
I'm not saying one or the other is more or less likely, but the range of possibilities is vast and unimaginable. The idea of energy (in the sense you and I use it now) is not even 400 years old. Harnessing ever larger amounts of stored energy was the hallmark of the industrial revolution. Declaring it to be the fundamental law underlying civilization is like concluding that the earth is flat: You mistake the shape of our immediate environment (the recent past and short term future) for the structure of the overall thing.
We are quite definitely headed in the next couple of hundred years for an end to exponential growth in energy consumption. Exponential growth near where we've been would lead us to cooking the earth in 300-400 years. By the time we're capable of doing solar system scale engineering we will have had millennia of 'culture' that exists within a constant energy envelope. What these entities will value, or want to do is beyond anyone's guess.
Is the idea that the habitats would be much larger than planets or that there would be far more of them for a given total volume of matter ?
I think the viability of efficient is a big "if", and will depends on a lot of factors (not just engineering ones, also social, environmental, and economical ones).
Because I'm an eternal optimist I tend to think of these filters as very positive, things like finding alternative sources of energy to stars, or reclusing themselves in some VR utopia.
Interesting that you might consider that a positive outcome. My immediate reaction is that it would be a very negative one. It feels like giving up - "it's not great out here, we can't make it better, might as well plug in and pretend."
Maybe I'm making the same mistake as people trying to apply home ec budgeting to national economies; if I just dropped everything and started playing video games it would be bad, but the same might not be true for entire civilizations who are further up the Kardashev scale than humans.
How big would the signal be compared to normal variance between stars?
Enough for them to do .. what? Trapped in a closed box, with no unexplored 'natural' non-engineered habitat, nothing to dig for, no unknown/unowned resources, no resources to use to escape.
Enough to let the cylinder owners extract money from their non-optional labours? Then it will certainly happen, but that doesn't make it look a happier or more desirable future.
Which physical limits are most relevant to precluding the solid sphere? Tidal forces?
What do you have? The same mass of Earth will have a million times the living area.
What's the problem? At 1 AU distance, this thing would have to spin so fast (IIRC ~1.5 million km/h) that the centrifugal forces would tear it apart. Not even graphene could withstand the forces. So the idea just isn't practical.
So if you create a hard shell, you have to ask: what is the intended goal?
If there is to create living area, where is gravity coming from? Do you spin the sphere? If so, it has the same centrifugal force problem.
If it's not (and technically even if it is) then you have the problem that the shell will collapse under the gravity of the star and/or its own mass.
- the only way that alien life could be intelligent is if they exploit the resources of their solar system maximally.
Don't we have enough evidence yet that maximal exploitation of resources is a Very Bad Idea?
But the point here isn't to dive into the moral issues. It's not even to ask what MOST civilizations would do. It's simply to ask would ALL civilizations restrain themselves this way? If the answer is "no" then we'll find at least one. Saying no civilization would engage in this kind of growth when it looks entirely possible seems like far more of a stretch than the scenario I outlined.
Maximally exploiting your resources is not civilized.
Population is projected to plateau in the near future. What if those habitats exist but just are not observable since they are quite small compared to their stars / planets?
You see this in all other species, but we somehow think it's different for us. That remains to be seen.
If we lived in a world where every culture had achieved a certain level of education and development (and most all of them do want to get there), it's likely they would all have flat or declining populations. They might have to heavily subsidize reproduction just to sustain themselves and all this talk about building space habitats would be even more abstract than it is today.
The thing is if there's any culture for which that's not true, like Mormons, Orthodox Jews, some groups of Muslims, whatever. In a few generations they replace the cultures that don't have a lot of children like our own. Then expansion continues.
I could see expansion slowing even reversing temporarily, but it seems hard to imagine it permanently ending.
Anyway I agree that we can't say for certain whether population will grow or shrink. In fact in the context of this discussion I think that's the most important point. Many discussions about alien civilizations tend to assume that they'll evolve into huge multiplanetary populations with large energy/EM/whatever footprints. When in reality our most developed cultures are slowly declining in population. If an underground cache of brains in pleasure boxes is the end stage for most civs we will probably never know.
And that is only thinking about the impact of tech we might see this century.
Exponential growth is really a phenomenon of transitions. We are in a very rapid 10.000 year transition from biological system to cultural system. This transition accelerated further in the last two centuries. If we think about the end point of this transition it should be a system that is entirely defined by its culture rather than by its biology. Maybe even completely away from its biology. It's fun but idle to speculate what that culture will be like, but if experiences can be shared as easily as text today, what is the value of having billions of copies of similar experiences? What _is_ an individual in that situation?
Even if we accept your simple expansion/competition/ressources based model of reality* (and I see no reason we should) maybe combining consciousnesses leads to much better results. Maybe expansion will look like ever increasing use of energy resources to enable larger consciousness rather than maintaining more animal bodies.
Use Occam's Razor: there are no aliens.
(Yes, I know I'm treading on some dearly-held religious beliefs now and will get lynched. Still, somebody had to say it.)
Space is ridiculously big. The universe is ridiculously old. Talking in absolutes about such things is a poor strategy.
When I was a kid, I figured the Earth itself would be a blip on a universal timescale. It's kind of disappointing that geological and astronomical timescales are so similar.
Of course, it doesn't really change your point. If a billion years is a surprisingly short period of time, then 21 years is an instant.
This was my original point: you can’t hide a Dyson Swarm. It goes the other way too. You can’t really hide from a K2 civilization either.
We’re getting into Fermi Paradox territory here. The beauty of a lot of arguments here is that you don’t need to prove or even assume that civilizations will, on average, “hide” because it just takes one to be detected. So the arguments is actually “do ALL civilizations hide?”
This is a much harder argument to make.
> There could have been aliens nearby a million years ago that are now extinct or elsewhere
In Fermi Paradox terms, this questioned is framed as “is there a Great Filter ahead of us?” This question predictably has a lot of discussion. It’s hard to predict what that might be because even apocalyptic scenarios other than extreme bad luck (eg a nearby star going supernova) are unlikely to completely wipe us out at this point, even nuclear Armageddon.
Of course what exists or doesn't exist in the universe that's not visible is pure unscientific speculation; might as well be made of blue cheese as far as science is concerned.
> Space is ridiculously big. The universe is ridiculously old.
This isn't true. Mathematical concepts of infinities and limits are "ridiculously big". Space is finite and thus ridiculously small.
If something can only be proven to a 99.999999% certainty, is that still "unscientific"? What if scientists predict something happening with only 0.1% chance, for example the likelihood of a particular asteroid hitting earth? Or what about 60%, like a typical weather report predicting rain.
Generally, the high, low, or intermediate likelihood of some event happening does not make it unscientific.
While it would be unscientific to simply say that aliens exist, it's plenty scientific to consider the rate of star formation and age, conditions for life around stars, and time it takes to develop intelligent life to say that there is a particular likelihood of there being alien life.
Like I said in another comment below - you're assuming information is distributed uniformly across the universe, which we don't really know and can't assume because it certainly isn't in the solar system.
> what exists or doesn't exist in the universe that's not visible is pure unscientific speculation
I don't see anyone saying that the existence of aliens aren't speculation or that "aliens exists" (or your: "aliens don't exist") isn't just a personal belief as stupid to argue about as religion. But as countless wars have shown, people (like you) will try to create conflict from differing personal beliefs. Just because you drop "Occam's razor" doesn't make your belief the correct one.
The singularity was infinite. Space is infinity, but bigger.
Everything you said is unsupportable
What's out there outside the observable universe is fun to speculate about, but it's armchair philosophy, not science. Maybe there's an infinite variety of life and somewhere out there right now Gandalf is wielding a light saber while riding a dinosaur. Maybe we're alone in the universe because the Earth so happens to sit right on the only information complexity singularity in the universe. (We really don't know anything about the information structure of the universe yet; all the "dude, the universe is really big" arguments assume that information is distributed uniformly across the universe, but this obviously doesn't match observed reality.)
Here are all the facts:
1) There's an incomprehensibly large amount of stars and planets in the universe
2) On one of these planets (Earth), there are conditions which have lead to the appearance of life
3) These conditions are not unique to this planet
We don't know of any fact that would exclude the possibility of life coming about on other planets with similar conditions, so using Occam's Razor actually tells us that there's probably lots of other life out there.
What about gravity? Is it possible/feasible to have long-term habitats without any meaningful gravity?
The argument is basically this:
1. Within 1000 years (and maybe a lot less) we will have the engineering capability to build space habitats, powered by solar power. This last part is important because this thought experiment isn't gated on commercial viability of nuclear fusion power, which I'm not yet convinced is possible.
2. These space habitats are far more efficient at creating living area than planets. I forget the exact numbers but something like 1% of the mass of Mercury is enough to create enough living area for something like 10^16 to 10^18 people.
3. Space habitats are more convenient and cheaper to move between than leaving or even entering a gravity well like Earth's.
4. Roughly one billionth of the Sun's energy hits the Earth.
5. Once you have the ability to create one of these things, each becomes progressively easier.
This, of course, is the classic Dyson Swarm. Originally this was called a Dyson Sphere but this has led some to think it's a solid shell around a star. That was never the intent. Even if it was, no known or currently theorized material could support this.
Dyson Swarms are not subtle. Even a partial Dyson Swarm should be detectable as a large IR source compared to how much visible light is produced. This is because the only way for something in space to cool down is to radiate that heat away and physics determines the wavelength of that based on the temperature of the object.
Standard objection: what if you can recycle that heat? Well, you can't do that perfectly (as this would violate Thermodynamics) and even if you reduce IR emissions by 90%, you've simply reduced the IR emissions by one order of magnitude. For comparison, the Sun produces roughly 4x10^26 Watts of power.
So if you accept the above premises the gap between stabbing each other with swords and having this technology, at least for us, is 1000-2000 years, a cosmic blink of an eye to produce signals without the above IR signature. Those are long odds.
Personally I subscribe to the view that technological life is, at least within a billion light years of us, is likely quite rare.
The above is a very superficial summary of a topic that Isaac Arthur's channel goes into great depth about. I guarantee you any objection you have has at least one video that goes into that in great depth.