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Not to sound like a broken record (I and others have said this or similar on these kinds of threads) but... I, personally, have become convinced that looking fo

by cletus 7y ago

Not to sound like a broken record (I and others have said this or similar on these kinds of threads) but... I, personally, have become convinced that looking for signals this way is actually pointless. 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.

resters 7y ago
Fascinating. Thank you for writing this comment.
StillBored 7y ago
I always thought the more realistic answer was that the window to detect an emerging civilization is on the order of a couple decades. In that time they go from simple easily detectable modulation schemes that are broadcast at very high power to modulation schemes that are nearly impossible to differentiate from noise at much higher efficiency/lower power levels. Much like we have, in the 1950's it was all high power TV/Radio signals which were radiating into space on fairly narrow bands. Now days we have really wide band signals using really advanced modulation techniques frequently sitting at or below the noise floor (GPS!) and frequently very short range (5G!). Then using your Drake equation variables calculate how many are within those couple decades at any given point that you can see.
- ars 7y ago
  Radar. That's the RF that's easiest to detect from long distances, it's focused, and it's strong. The hard part is deciding if it's natural or artificial.
  - Beldin 7y ago
    Top of my head, so I may be off, but: The Arecibo message was easily the easiest to detect by far. Its signal will become indistinguishable from background radiation at a distance of slightly over 625 light years. 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.
    - tgflynn 7y ago
      > Its signal will become indistinguishable from background radiation at a distance of slightly over 625 light years. 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 ?
  - StillBored 7y ago
    That may not last much longer either. Transponders are more effective/useful for civilian purposes and the military needs to be stealthy. Big radar installations have a sign painted on them that says "take me out first".
crazygringo 7y ago
That's a fascinating comment, thank you. 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? [1] https://en.wikipedia.org/wiki/Biosphere_2 https://en.wikipedia.org/wiki/Biosphere_2
- seventytwo 7y ago
  You make the case that political issues haven’t changed much isn’t he past 2400 years, but then go on to say you’d like to see us manage things here at home before expanding into space? 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.
  - crazygringo 7y ago
    The conflict is exactly what I'm pointing out. 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.
dylan604 7y ago
>3. Space habitats are more convenient and cheaper to move between than leaving or even entering a gravity well like Earth's. 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.
- ralusek 7y ago
  Or, you know, just use walls and glass.
  - dylan604 7y ago
    Building habitable structures on a planet's surface is not the same as making a planet's entire environment capable of supporting humans. That's the point of teraforming which was the point of the comment.
- Beldin 7y ago
  > Sci-fi wants us to believe that we can teraform planets. 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!
  - dylan604 7y ago
    I'm sorry, what? Are you claiming we have created a livable atmosphere on another planet? Where? Which one? Are you talking about Earth? Humans did not create the Earth's atmosphere. We can barely "fix" the damage we do to it. "Fixing" is not creating.
    - suby 7y ago
      He is saying that we are currently transformong the earth's atmosphere into a less hospitable one through a process of pollution / emitting greenhouse gases. 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.
KaoruAoiShiho 7y ago
Haven't seen the channel but it's likely that there's other filters that we don't fully understand yet facing us in the future that prevents aliens from creating dyson swarms. 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.
- chucksmash 7y ago
  > 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.
aeternum 7y ago
We may have the technology to create massive habitats in the near future, but what if we do not have the need. 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?
- eloff 7y ago
  Isaac Arthur deals with this at length in his videos. Those projections are unlikely to hold for long. Cultures that don't expand will quickly be replaced by those who do and the process continues. Population expansion is limited only really by resources. You see this in all other species, but we somehow think it's different for us. That remains to be seen.
  - apatters 7y ago
    We think it's different for us because the reversal in population growth is correlated with education and development levels. These are factors which aren't present in animal populations. 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.
    - eloff 7y ago
      This seems to currently be a thing. It's a little premature to say it's going to apply to all cultures across all time. In fact I'd take the opposite side of that bet. 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.
      - 7y ago
solstice 7y ago
Interesting. If I understand you correctly, you are saying that it makes more sense to look for large IR sources (without accompanying visible light), instead of looking for radio signals. Correct?
- cletus 7y ago
  Correct. The signature of a large Dyson Swarm would be hard to mistake, particularly for anything natural, at least anything we've seen thus far.
  - tgflynn 7y ago
    I'm having trouble seeing what it is about this scenario that would make it look so different from a star with planets (which is still very hard for us to detect) or surrounded by clouds of smaller debris. 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 ?
tgsovlerkhgsel 7y ago
> Even a partial Dyson Swarm should be detectable How big would the signal be compared to normal variance between stars?
schoen 7y ago
> Even if it was, no known or currently theorized material could support this. Which physical limits are most relevant to precluding the solid sphere? Tidal forces?
- cletus 7y ago
  So if we step back a second, look at a Ringworld. I'm not sure if Larry Niven proposed this idea (in the book by the same name) or just popularized it, but the idea is basically this: If you take the mass of the Earth and turn it into a ring that encircles a star, spin it to create artificial gravity and put walls on the sides (on the inside) to keep an atmosphere in. 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.
  - BlueTemplar 7y ago
    Wait, isn't the force "that would tear it apart" the same as the gravity you wanted to generate?
    - cletus 7y ago
      An O’Neil Cylinder is a few miles wide. Stainless steel can handle the rotation required to create earth like gravity. If we can practically produce graphemes instead you can go up to several thousand miles in diameter (McKendree Cylinders). 1 AU in diameter is something else entirely.
      - schoen 7y ago
        We can already practically produce graphemes -- just not graphenes. :-)
Balgair 7y ago
This is based on the current knowledge of physics that we have. We know that it is fairly incomplete. ~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.
- saalweachter 7y ago
  It's not impossible that 95% of the universe is boring. 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.
  - Balgair 7y ago
    I mean, that's my point. There's nothing to say it won't be very interesting. We just don't know yet.
  - cambalache 7y ago
    >Atoms are something like 0.05% electrons Just in mass. In volume(orbitals), electric charge, importance for chemistry, the proportions are way different.
- Yizahi 7y ago
  Only dark energy and matter are just a placeholders really. We aren't sure they exist, we are just seeing that our calculations are off without obvious reason.
Carpetsmoker 7y ago
I think this kind of thinking is roughly analogous to "why buy a phone now, when the latest model will be released next year"? Or, perhaps more on-topic, "why do any astronomical observation with this telescope when we will have a better one in a few years"? 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).
Yizahi 7y ago
I think you are overestimating ease of building and living in space habitats as opposed to living on planet surfaces. If I were to guess, I'd say that any significant and detectable space habitats will be preceded by extensive colonization to nearby stars. Though now I'm oversimplifying space travel instead. I guess this problem is so complex that we can't even estimate orders of magnitude correctly.
retrac 7y ago
I don't think you even have to go that far. 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?
- Random_ernest 7y ago
  > Modern encrypted spread-spectrum digital radio would have looked like random noise until quite recently Topics like this are discussed in Stanislaw Lems, Masters voice novel. A really good read.
otabdeveloper4 7y ago
Yes, but not for the reasons you outlined. 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.)
- mdorazio 7y ago
  That's a bit too broad of a statement to be plausible. It's likely there are no aliens near us in time, space, technology, and desire to communicate to make such a search fruitful right now. There could very well be aliens on the other side of the galaxy that we can't see. There could have been aliens nearby a million years ago that are now extinct or elsewhere. There could be aliens right now that are pre-industrial or advanced enough to not communicate with methods that resolve on the bands SETI looks at. There could be aliens that follow a game theory mindset of non-communication ala The Dark Forest. Etc. Space is ridiculously big. The universe is ridiculously old. Talking in absolutes about such things is a poor strategy.
  - otabdeveloper4 7y ago
    Okay, let me qualify: there are no aliens in the visible universe. 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.
    - mnsc 7y ago
      > Yes, I know I'm treading on some dearly-held religious beliefs .... > 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.
Certhas 7y ago
The question is, why do you assume that advanced civilization would maintain 10^18 animal bodies to carry around brains? That's ridiculously inefficient. It's also unclear why you would expect an advanced civilization to be built on a large number of individuals either. That, too is derived from an animal impulse to procreate and maybe a reaction to mortality. Say that in the next thousand years we manage to move consciousness off body, and the experiences enabled by this make the greatest drug trips obsolete by comparison. Why would we choose to build space habitats for bodies when we could build space ships that use a fraction of the energy but allow us to explore the galaxy by slowing down the rate of experience.
- cletus 7y ago
  I don’t assume that. If however your goal is a digital existence then you still have energy as the limiting factor and the best way to maximize this is likely a Matrioshka Brain, which from far away is largely indistinguishable from a Dyson Swarm.
  - Certhas 7y ago
    And why would energy be the limiting factor? Maybe the limiting factor will be accidental entanglement with the environment of your quantum computer, and you want to cool your system waaay down to avoid thermals interfering with your finely tuned computation engine. Having a hot sphere around a star seems like a terrible set up to do that. Maybe sitting out in a hydrogen cloud and running well controlled fusion would be a much better for that. 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.
dasKrokodil 7y ago
> space habitats What about gravity? Is it possible/feasible to have long-term habitats without any meaningful gravity?
- cletus 7y ago
  You spin them to create “gravity”, which is really just centrifugal force.
  - tgflynn 7y ago
    So what sort of geometry would they have, toroidal, cylindrical ? I was initially thinking you meant they would be spheres but I'm not sure how you would generate gravity on a sphere, unless only the equatorial region was inhabited.
    - zoonosis 7y ago
      The type of habitat he is describing is known as an O'Neil cylinder. The wikipedia page for the topic probably answers most questions you have about it. https://en.wikipedia.org/wiki/O'Neill_cylinder https://en.wikipedia.org/wiki/O'Neill_cylinder
learnstats2 7y ago
There are several gaps in logic here but in my opinion the most remarkable assumption here is: - 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?
- cletus 7y ago
  I wouldn't call using 1% of the mass of Mercury to create enough living area for a quintillion people and using most of the energy our Sun produces anyway to be analogous to anything you're alluding to on Earth thus far. 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.
  - learnstats2 7y ago
    My claim is that no civilization would engage in this kind of growth, yes. Maximally exploiting your resources is not civilized.
jodrellblank 7y ago
> enough to create enough living area for something like 10^16 to 10^18 people. 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.

by cletus 7y ago

resters 7y ago

Fascinating. Thank you for writing this comment.

StillBored 7y ago

I always thought the more realistic answer was that the window to detect an emerging civilization is on the order of a couple decades. In that time they go from simple easily detectable modulation schemes that are broadcast at very high power to modulation schemes that are nearly impossible to differentiate from noise at much higher efficiency/lower power levels. Much like we have, in the 1950's it was all high power TV/Radio signals which were radiating into space on fairly narrow bands. Now days we have really wide band signals using really advanced modulation techniques frequently sitting at or below the noise floor (GPS!) and frequently very short range (5G!). Then using your Drake equation variables calculate how many are within those couple decades at any given point that you can see.

ars 7y ago
Radar. That's the RF that's easiest to detect from long distances, it's focused, and it's strong. The hard part is deciding if it's natural or artificial.
- Beldin 7y ago
  Top of my head, so I may be off, but: The Arecibo message was easily the easiest to detect by far. Its signal will become indistinguishable from background radiation at a distance of slightly over 625 light years. 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.
  - tgflynn 7y ago
    > Its signal will become indistinguishable from background radiation at a distance of slightly over 625 light years. 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 ?
- StillBored 7y ago
  That may not last much longer either. Transponders are more effective/useful for civilian purposes and the military needs to be stealthy. Big radar installations have a sign painted on them that says "take me out first".

crazygringo 7y ago

That's a fascinating comment, thank you. 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? [1] https://en.wikipedia.org/wiki/Biosphere_2 https://en.wikipedia.org/wiki/Biosphere_2

seventytwo 7y ago
You make the case that political issues haven’t changed much isn’t he past 2400 years, but then go on to say you’d like to see us manage things here at home before expanding into space? 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.
- crazygringo 7y ago
  The conflict is exactly what I'm pointing out. 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.

dylan604 7y ago

>3. Space habitats are more convenient and cheaper to move between than leaving or even entering a gravity well like Earth's. 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.

ralusek 7y ago
Or, you know, just use walls and glass.
- dylan604 7y ago
  Building habitable structures on a planet's surface is not the same as making a planet's entire environment capable of supporting humans. That's the point of teraforming which was the point of the comment.
Beldin 7y ago
> Sci-fi wants us to believe that we can teraform planets. 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!
- dylan604 7y ago
  I'm sorry, what? Are you claiming we have created a livable atmosphere on another planet? Where? Which one? Are you talking about Earth? Humans did not create the Earth's atmosphere. We can barely "fix" the damage we do to it. "Fixing" is not creating.
  - suby 7y ago
    He is saying that we are currently transformong the earth's atmosphere into a less hospitable one through a process of pollution / emitting greenhouse gases. 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.

KaoruAoiShiho 7y ago

Haven't seen the channel but it's likely that there's other filters that we don't fully understand yet facing us in the future that prevents aliens from creating dyson swarms. 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.

chucksmash 7y ago
> 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.

aeternum 7y ago

We may have the technology to create massive habitats in the near future, but what if we do not have the need. 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?

eloff 7y ago
Isaac Arthur deals with this at length in his videos. Those projections are unlikely to hold for long. Cultures that don't expand will quickly be replaced by those who do and the process continues. Population expansion is limited only really by resources. You see this in all other species, but we somehow think it's different for us. That remains to be seen.
- apatters 7y ago
  We think it's different for us because the reversal in population growth is correlated with education and development levels. These are factors which aren't present in animal populations. 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.
  - eloff 7y ago
    This seems to currently be a thing. It's a little premature to say it's going to apply to all cultures across all time. In fact I'd take the opposite side of that bet. 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.
    - 7y ago

solstice 7y ago

Interesting. If I understand you correctly, you are saying that it makes more sense to look for large IR sources (without accompanying visible light), instead of looking for radio signals. Correct?

cletus 7y ago
Correct. The signature of a large Dyson Swarm would be hard to mistake, particularly for anything natural, at least anything we've seen thus far.
- tgflynn 7y ago
  I'm having trouble seeing what it is about this scenario that would make it look so different from a star with planets (which is still very hard for us to detect) or surrounded by clouds of smaller debris. 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 ?

tgsovlerkhgsel 7y ago

> Even a partial Dyson Swarm should be detectable How big would the signal be compared to normal variance between stars?

schoen 7y ago

> Even if it was, no known or currently theorized material could support this. Which physical limits are most relevant to precluding the solid sphere? Tidal forces?

cletus 7y ago
So if we step back a second, look at a Ringworld. I'm not sure if Larry Niven proposed this idea (in the book by the same name) or just popularized it, but the idea is basically this: If you take the mass of the Earth and turn it into a ring that encircles a star, spin it to create artificial gravity and put walls on the sides (on the inside) to keep an atmosphere in. 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.
- BlueTemplar 7y ago
  Wait, isn't the force "that would tear it apart" the same as the gravity you wanted to generate?
  - cletus 7y ago
    An O’Neil Cylinder is a few miles wide. Stainless steel can handle the rotation required to create earth like gravity. If we can practically produce graphemes instead you can go up to several thousand miles in diameter (McKendree Cylinders). 1 AU in diameter is something else entirely.
    - schoen 7y ago
      We can already practically produce graphemes -- just not graphenes. :-)

Balgair 7y ago

This is based on the current knowledge of physics that we have. We know that it is fairly incomplete. ~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.

saalweachter 7y ago
It's not impossible that 95% of the universe is boring. 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.
- Balgair 7y ago
  I mean, that's my point. There's nothing to say it won't be very interesting. We just don't know yet.
- cambalache 7y ago
  >Atoms are something like 0.05% electrons Just in mass. In volume(orbitals), electric charge, importance for chemistry, the proportions are way different.
Yizahi 7y ago
Only dark energy and matter are just a placeholders really. We aren't sure they exist, we are just seeing that our calculations are off without obvious reason.

Carpetsmoker 7y ago

I think this kind of thinking is roughly analogous to "why buy a phone now, when the latest model will be released next year"? Or, perhaps more on-topic, "why do any astronomical observation with this telescope when we will have a better one in a few years"? 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).

Yizahi 7y ago

I think you are overestimating ease of building and living in space habitats as opposed to living on planet surfaces. If I were to guess, I'd say that any significant and detectable space habitats will be preceded by extensive colonization to nearby stars. Though now I'm oversimplifying space travel instead. I guess this problem is so complex that we can't even estimate orders of magnitude correctly.

retrac 7y ago

I don't think you even have to go that far. 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?

Random_ernest 7y ago
> Modern encrypted spread-spectrum digital radio would have looked like random noise until quite recently Topics like this are discussed in Stanislaw Lems, Masters voice novel. A really good read.

otabdeveloper4 7y ago

Yes, but not for the reasons you outlined. 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.)

mdorazio 7y ago
That's a bit too broad of a statement to be plausible. It's likely there are no aliens near us in time, space, technology, and desire to communicate to make such a search fruitful right now. There could very well be aliens on the other side of the galaxy that we can't see. There could have been aliens nearby a million years ago that are now extinct or elsewhere. There could be aliens right now that are pre-industrial or advanced enough to not communicate with methods that resolve on the bands SETI looks at. There could be aliens that follow a game theory mindset of non-communication ala The Dark Forest. Etc. Space is ridiculously big. The universe is ridiculously old. Talking in absolutes about such things is a poor strategy.
- otabdeveloper4 7y ago
  Okay, let me qualify: there are no aliens in the visible universe. 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.
  - mnsc 7y ago
    > Yes, I know I'm treading on some dearly-held religious beliefs .... > 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.

Certhas 7y ago

The question is, why do you assume that advanced civilization would maintain 10^18 animal bodies to carry around brains? That's ridiculously inefficient. It's also unclear why you would expect an advanced civilization to be built on a large number of individuals either. That, too is derived from an animal impulse to procreate and maybe a reaction to mortality. Say that in the next thousand years we manage to move consciousness off body, and the experiences enabled by this make the greatest drug trips obsolete by comparison. Why would we choose to build space habitats for bodies when we could build space ships that use a fraction of the energy but allow us to explore the galaxy by slowing down the rate of experience.

cletus 7y ago
I don’t assume that. If however your goal is a digital existence then you still have energy as the limiting factor and the best way to maximize this is likely a Matrioshka Brain, which from far away is largely indistinguishable from a Dyson Swarm.
- Certhas 7y ago
  And why would energy be the limiting factor? Maybe the limiting factor will be accidental entanglement with the environment of your quantum computer, and you want to cool your system waaay down to avoid thermals interfering with your finely tuned computation engine. Having a hot sphere around a star seems like a terrible set up to do that. Maybe sitting out in a hydrogen cloud and running well controlled fusion would be a much better for that. 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.

dasKrokodil 7y ago

> space habitats What about gravity? Is it possible/feasible to have long-term habitats without any meaningful gravity?

cletus 7y ago
You spin them to create “gravity”, which is really just centrifugal force.
- tgflynn 7y ago
  So what sort of geometry would they have, toroidal, cylindrical ? I was initially thinking you meant they would be spheres but I'm not sure how you would generate gravity on a sphere, unless only the equatorial region was inhabited.
  - zoonosis 7y ago
    The type of habitat he is describing is known as an O'Neil cylinder. The wikipedia page for the topic probably answers most questions you have about it. https://en.wikipedia.org/wiki/O'Neill_cylinder https://en.wikipedia.org/wiki/O'Neill_cylinder

learnstats2 7y ago

There are several gaps in logic here but in my opinion the most remarkable assumption here is: - 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?

cletus 7y ago
I wouldn't call using 1% of the mass of Mercury to create enough living area for a quintillion people and using most of the energy our Sun produces anyway to be analogous to anything you're alluding to on Earth thus far. 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.
- learnstats2 7y ago
  My claim is that no civilization would engage in this kind of growth, yes. Maximally exploiting your resources is not civilized.

jodrellblank 7y ago

> enough to create enough living area for something like 10^16 to 10^18 people. 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.