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> is there really any practical value in this sort of research In many ways it is too early to do this research, so it is a kind of art (as is a lot of researc

> is there really any practical value in this sort of research In many ways it is too early to do this research, so it is a kind of art (as is a lot of research, imho). As long as only a few people do it, it's cool and useful so we can be aware of our potential future. On the other hand, since we have no credible evidence of extraterrestrials, it would be surprising to find a civilisation so advanced to build a Dyson sphere. If they can build Dyson spheres, wouldn't they already be all over the place? Ok, I suppose I should actually go read the paper now...

bryanrasmussen 5y ago
Being able to build Dyson spheres does not make them capable of going faster than the speed of light, so any civilization capable of building a Dyson sphere would probably still be clustered around a couple stars and that's it. Would such a civilization spread to more than one star is actually also a question, or would they control their population rationally stay on their Dyson sphere and only start to move when the star had less than 100,000 years left to go. Only some Dyson sphere variants, like Shkadov thrusters, are primarily conceived as ways to move around. Which personally seems to me less likely, is a civilization, as well as the ability to construct these objects, also going to have a species level interest in going exploring?
- perihelions 5y ago
  > "Being able to build Dyson spheres does not make them capable of going faster than the speed of light, so any civilization capable of building a Dyson sphere would probably still be clustered around a couple stars and that's it." Check your math: this galaxy is ~10^5 light-years in size and ~10^10 years in age.
  - bryanrasmussen 5y ago
    what does that have to do with anything I said? Yes, I guess they would be everywhere if their civilization was able to make Dyson spheres 1 year after the creation of the galaxy, also if they decided to 1. Not control their population for some reason. 2. Had some sort of interest in exploring. 3. Implicit also in the speed of light thing, would find it really interesting to send a portion of their population to the next available and suitable star which might be enough light years away to make communication impractical. I mean for our civilization there is some level of argument that says it would be a ridiculous idea to move to a new solar system and we have an intellectual exploratory streak in our species. I mean we are currently not at the level of being able to do a Dyson sphere, it took us 4.543 billion years (age of earth) to get to the part that somebody could conceive of it. There is also some discussion as to whether or not our civilization is going to last, so given that and the other things I said it seems unlikely to me that any Dyson sphere civilization would actually build more than one, but maybe some build two because binary stars or some other weird circumstance which makes it worthwhile to do. on edit: if we get to Dyson sphere building capabilities which seems really unlikely, will we build more than one? How many more?
    - MattPalmer1086 5y ago
      The point is that you don't need to go faster than the speed of light. There's more than enough time to cover the entire galaxy in a relatively short period of time at sublight speeds. A few million years is sufficient.
      - bryanrasmussen 5y ago
        yeah, sure, enough time to GO everywhere but not enough time to BE everywhere, which is a different thing entirely, even if all the other things I brought up as to why the aliens weren't everywhere were not things to take into consideration. So again, still haven't heard any argument why an alien civilization achieving the ability to build Dyson spheres, even if they did so far enough in the past that they would then have adequate time to traverse the galaxy afterwards, would then have to be everywhere?
        MattPalmer1086 5y ago
        I'm not sure I understand your argument. There is sufficient time, with waves of colonisation to spread across the galaxy many times over. This can include pauses of thousands of years between colonisation waves. Some of those colonies could also build Dyson spheres. You would end up with them scattered all over the galaxy. Even if the colonies dies out subsequently, the spheres would still be detectable.
        bryanrasmussen 5y ago
        >I'm not sure I understand your argument. There is sufficient time, with waves of colonisation to spread across the galaxy many times over. yes, there is, if the achievement of Dyson sphere building happened long enough in the past for there to have been sufficient time. 50,000 years ago even, no. The length of human civilization is 6000 years approximately, what if this civilization much, much older than ours 6000 years ago just started building it's first Dyson sphere. For some reason the assumption is that it was far enough in the past that they COULD be everywhere if they wanted to. But then the phrasing is not that they could be everywhere but rather they would be everywhere, hence no civilization has built Dyson spheres. A lot of this theory that the aliens will go about building lots and lots of Dyson spheres seems based on the assumption that they will be a lot like us, but actually I don't even think we would ever build more than one. If we built a Dyson sphere it would be because we were at the point we needed the energy and we had the technology to do it of course, and we had a political system that could harness everyone to do it. But once we had the Dyson sphere I am not sure we would ever be at the position were we would need another one. Since people tend to have fewer kids the higher their standard of living it may be that with the standard of living of Dyson sphere civ that our population would be at replacement level, that is to say we would never need to move from one Dyson sphere until the sun was just about used up. So again, sure there is sufficient time with waves of colonization (started far enough in the past) - but waves of colonization assumes a species that has a colonization urge and perhaps one that has a colonization urge greater than that of humanity. That's a pretty big if, considering all the other big ifs in the whole building a Dyson sphere scenario.
- caf 5y ago
  They may not be moving around to explore so much as to keep their solar system safe. Galactic orbits are far more chaotic than the sedate stable orbits within the solar system - stars closely approach each other on a somewhat regular basis.
  - bryanrasmussen 5y ago
    that's a good point, but I guess at Dyson sphere level a star approaching is like discovering oil on your property.
dave_sullivan 5y ago
No Dyson spheres, but there are black holes all over the place. Some people think those would make great computing devices, many of their origins are not well explained as super nova remnants, and they efficiently harness energy from companion stars. They have all the properties of Dyson spheres but they actually exist. Maybe with advanced enough physics, intelligent civilizations learn to manufacture and harness black holes, neutron stars, and other dense objects for societal benefit.
- jonathankoren 5y ago
  > No Dyson spheres, but there are black holes all over the place. Some people think those would make great computing devices They’re crappy computing devices. Even if you figured out how to program one — and that’s an “if” that would make Sagittarius A* look like a neutrino — there’s no way to read the information out except Hawking Radiation, and that would take 10^70 years. https://youtu.be/0GLgZvTCbaA https://youtu.be/0GLgZvTCbaA (8:36)
- alfiedotwtf 5y ago
  This is the first time I've heard of this. Wow, yes! A blackhole is far more efficient at consuming energy than a Dyson Sphere... the hard part though is kickstarting the process I guess
ohyeshedid 5y ago
> If they can build Dyson spheres, wouldn't they already be all over the place? I figure they'd have to be. They'd need more than a solar system's worth of raw resources to build the sphere. They may need more than a solar system's worth of resources just to build the tools and craft to be able to build the sphere. They're going to need an insane amount of production facilities for various components, and that's going to take a massive amount of resources. That's going to require exploring quite a bit of a galaxy.
awb 5y ago
> If they can build Dyson spheres, wouldn't they already be all over the place? The number I’ve seen quoted is 50M years to colonize the galaxy: http://www.sentientdevelopments.com/2012/01/new-mathematical-study-reveals-that-our.html http://www.sentientdevelopments.com/2012/01/new-mathematical... > they calculated that any galactic empire would have spread outwards from its home planet at about 0.25% of the speed of light. The result is that after 50m years it would extend over 130,000 light years, with zealous colonisers moving in a relatively uniform cloud and more reticent ones protruding from a central blob. Since the Milky Way is estimated to be 100,000-120,000 light years across, outposts would be sprinkled throughout the galaxy, even if the home planet were, like Earth, located on the periphery. It’s actually so fast that advanced civilizations would have had time to colonize the galaxy and go extinct many times over without us noticing. Or maybe their spheres were built so long ago they’ve already collapsed and been consumed by the stars again. It’s a great mystery and interesting thought experiment though.
- denton-scratch 5y ago
  > 50M years to colonize the galaxy Our ancestors from 50M years ago are all extinct. So a civilisation spreading through the galaxy would have evolved in all kinds of different ways. It's not obvious to me that these diverse evolutionary strands would all still be interested in Dyson spheres, or space travel, or even astronomy. There's a belief that's hard to shake off, that the properties humans have that we think most important represent some kind of evolutionary pinnacle. Typically, those properties are language, and a large brain for processing language. But if language and a large brain are really such great evolutionary advantages, why are humans the only creatures on Earth that have evolved those properties? Possibly language and a large brain are an evolutionary backwater. At 0.25% of the speed of light, it would take us 1,600 years to reach Proxima Centauri; but it might take a lot longer to reach a star with habitable planets. We'd definitely need generation ships. After (say) a million years, we'd presumably have evolved to adapt to life on generation ships. It's not obvious to me that such adaptations would leave us fit to inhabit a planet. And perhaps adaptation to life on a generation ship means adapting to eating your fellow passengers. Given the history of humanity, I find it hard to believe that the population of a generation ship could survive as long as 100 years without war breaking out on-board. We've had large brains and language for about 50,000 years, as far as I can tell; we've been warring the whole time. Maybe large brains and language pre-dispose us to war? If that's right, then it seems unlikely that intelligent life would ever spread far from it's planet of origin. I'm very sceptical of the idea that any "civilisation" could ever spread far from its home planet. There are two things that we refeer to as a civilisation: a culture, and a species. Culture changes very quickly - over a single lifetime. But on a scale of millions of years, speciation is also pretty quick. So I can't see how any kind of homogenous civilisation or species could spread through a galaxy. They would have diversified before the train even reached its first stop. So I don't have any insurance against being kidnapped by aliens.

bryanrasmussen 5y ago

Being able to build Dyson spheres does not make them capable of going faster than the speed of light, so any civilization capable of building a Dyson sphere would probably still be clustered around a couple stars and that's it. Would such a civilization spread to more than one star is actually also a question, or would they control their population rationally stay on their Dyson sphere and only start to move when the star had less than 100,000 years left to go. Only some Dyson sphere variants, like Shkadov thrusters, are primarily conceived as ways to move around. Which personally seems to me less likely, is a civilization, as well as the ability to construct these objects, also going to have a species level interest in going exploring?

perihelions 5y ago
> "Being able to build Dyson spheres does not make them capable of going faster than the speed of light, so any civilization capable of building a Dyson sphere would probably still be clustered around a couple stars and that's it." Check your math: this galaxy is ~10^5 light-years in size and ~10^10 years in age.
- bryanrasmussen 5y ago
  what does that have to do with anything I said? Yes, I guess they would be everywhere if their civilization was able to make Dyson spheres 1 year after the creation of the galaxy, also if they decided to 1. Not control their population for some reason. 2. Had some sort of interest in exploring. 3. Implicit also in the speed of light thing, would find it really interesting to send a portion of their population to the next available and suitable star which might be enough light years away to make communication impractical. I mean for our civilization there is some level of argument that says it would be a ridiculous idea to move to a new solar system and we have an intellectual exploratory streak in our species. I mean we are currently not at the level of being able to do a Dyson sphere, it took us 4.543 billion years (age of earth) to get to the part that somebody could conceive of it. There is also some discussion as to whether or not our civilization is going to last, so given that and the other things I said it seems unlikely to me that any Dyson sphere civilization would actually build more than one, but maybe some build two because binary stars or some other weird circumstance which makes it worthwhile to do. on edit: if we get to Dyson sphere building capabilities which seems really unlikely, will we build more than one? How many more?
  - MattPalmer1086 5y ago
    The point is that you don't need to go faster than the speed of light. There's more than enough time to cover the entire galaxy in a relatively short period of time at sublight speeds. A few million years is sufficient.
    - bryanrasmussen 5y ago
      yeah, sure, enough time to GO everywhere but not enough time to BE everywhere, which is a different thing entirely, even if all the other things I brought up as to why the aliens weren't everywhere were not things to take into consideration. So again, still haven't heard any argument why an alien civilization achieving the ability to build Dyson spheres, even if they did so far enough in the past that they would then have adequate time to traverse the galaxy afterwards, would then have to be everywhere?
      - MattPalmer1086 5y ago
        I'm not sure I understand your argument. There is sufficient time, with waves of colonisation to spread across the galaxy many times over. This can include pauses of thousands of years between colonisation waves. Some of those colonies could also build Dyson spheres. You would end up with them scattered all over the galaxy. Even if the colonies dies out subsequently, the spheres would still be detectable.
        bryanrasmussen 5y ago
        >I'm not sure I understand your argument. There is sufficient time, with waves of colonisation to spread across the galaxy many times over. yes, there is, if the achievement of Dyson sphere building happened long enough in the past for there to have been sufficient time. 50,000 years ago even, no. The length of human civilization is 6000 years approximately, what if this civilization much, much older than ours 6000 years ago just started building it's first Dyson sphere. For some reason the assumption is that it was far enough in the past that they COULD be everywhere if they wanted to. But then the phrasing is not that they could be everywhere but rather they would be everywhere, hence no civilization has built Dyson spheres. A lot of this theory that the aliens will go about building lots and lots of Dyson spheres seems based on the assumption that they will be a lot like us, but actually I don't even think we would ever build more than one. If we built a Dyson sphere it would be because we were at the point we needed the energy and we had the technology to do it of course, and we had a political system that could harness everyone to do it. But once we had the Dyson sphere I am not sure we would ever be at the position were we would need another one. Since people tend to have fewer kids the higher their standard of living it may be that with the standard of living of Dyson sphere civ that our population would be at replacement level, that is to say we would never need to move from one Dyson sphere until the sun was just about used up. So again, sure there is sufficient time with waves of colonization (started far enough in the past) - but waves of colonization assumes a species that has a colonization urge and perhaps one that has a colonization urge greater than that of humanity. That's a pretty big if, considering all the other big ifs in the whole building a Dyson sphere scenario.
caf 5y ago
They may not be moving around to explore so much as to keep their solar system safe. Galactic orbits are far more chaotic than the sedate stable orbits within the solar system - stars closely approach each other on a somewhat regular basis.
- bryanrasmussen 5y ago
  that's a good point, but I guess at Dyson sphere level a star approaching is like discovering oil on your property.

dave_sullivan 5y ago

No Dyson spheres, but there are black holes all over the place. Some people think those would make great computing devices, many of their origins are not well explained as super nova remnants, and they efficiently harness energy from companion stars. They have all the properties of Dyson spheres but they actually exist. Maybe with advanced enough physics, intelligent civilizations learn to manufacture and harness black holes, neutron stars, and other dense objects for societal benefit.

jonathankoren 5y ago
> No Dyson spheres, but there are black holes all over the place. Some people think those would make great computing devices They’re crappy computing devices. Even if you figured out how to program one — and that’s an “if” that would make Sagittarius A* look like a neutrino — there’s no way to read the information out except Hawking Radiation, and that would take 10^70 years. https://youtu.be/0GLgZvTCbaA https://youtu.be/0GLgZvTCbaA (8:36)
alfiedotwtf 5y ago
This is the first time I've heard of this. Wow, yes! A blackhole is far more efficient at consuming energy than a Dyson Sphere... the hard part though is kickstarting the process I guess

ohyeshedid 5y ago

> If they can build Dyson spheres, wouldn't they already be all over the place? I figure they'd have to be. They'd need more than a solar system's worth of raw resources to build the sphere. They may need more than a solar system's worth of resources just to build the tools and craft to be able to build the sphere. They're going to need an insane amount of production facilities for various components, and that's going to take a massive amount of resources. That's going to require exploring quite a bit of a galaxy.

awb 5y ago

> If they can build Dyson spheres, wouldn't they already be all over the place? The number I’ve seen quoted is 50M years to colonize the galaxy: http://www.sentientdevelopments.com/2012/01/new-mathematical-study-reveals-that-our.html http://www.sentientdevelopments.com/2012/01/new-mathematical... > they calculated that any galactic empire would have spread outwards from its home planet at about 0.25% of the speed of light. The result is that after 50m years it would extend over 130,000 light years, with zealous colonisers moving in a relatively uniform cloud and more reticent ones protruding from a central blob. Since the Milky Way is estimated to be 100,000-120,000 light years across, outposts would be sprinkled throughout the galaxy, even if the home planet were, like Earth, located on the periphery. It’s actually so fast that advanced civilizations would have had time to colonize the galaxy and go extinct many times over without us noticing. Or maybe their spheres were built so long ago they’ve already collapsed and been consumed by the stars again. It’s a great mystery and interesting thought experiment though.

denton-scratch 5y ago
> 50M years to colonize the galaxy Our ancestors from 50M years ago are all extinct. So a civilisation spreading through the galaxy would have evolved in all kinds of different ways. It's not obvious to me that these diverse evolutionary strands would all still be interested in Dyson spheres, or space travel, or even astronomy. There's a belief that's hard to shake off, that the properties humans have that we think most important represent some kind of evolutionary pinnacle. Typically, those properties are language, and a large brain for processing language. But if language and a large brain are really such great evolutionary advantages, why are humans the only creatures on Earth that have evolved those properties? Possibly language and a large brain are an evolutionary backwater. At 0.25% of the speed of light, it would take us 1,600 years to reach Proxima Centauri; but it might take a lot longer to reach a star with habitable planets. We'd definitely need generation ships. After (say) a million years, we'd presumably have evolved to adapt to life on generation ships. It's not obvious to me that such adaptations would leave us fit to inhabit a planet. And perhaps adaptation to life on a generation ship means adapting to eating your fellow passengers. Given the history of humanity, I find it hard to believe that the population of a generation ship could survive as long as 100 years without war breaking out on-board. We've had large brains and language for about 50,000 years, as far as I can tell; we've been warring the whole time. Maybe large brains and language pre-dispose us to war? If that's right, then it seems unlikely that intelligent life would ever spread far from it's planet of origin. I'm very sceptical of the idea that any "civilisation" could ever spread far from its home planet. There are two things that we refeer to as a civilisation: a culture, and a species. Culture changes very quickly - over a single lifetime. But on a scale of millions of years, speciation is also pretty quick. So I can't see how any kind of homogenous civilisation or species could spread through a galaxy. They would have diversified before the train even reached its first stop. So I don't have any insurance against being kidnapped by aliens.