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I think it's not only about energy generation but what would massive civilization without dyson spheres imply: 1. sidestepping thermodynamic laws - to allow ma

by rini17 5y ago

I think it's not only about energy generation but what would massive civilization without dyson spheres imply: 1. sidestepping thermodynamic laws - to allow massive energy use without detectable waste heat and/or 2. sidestepping time lags - so that the system does not need to be bunched as closely together as possible to allow for efficient communication and flows of material

TheOtherHobbes 5y ago
Dyson Spheres are fundamentally unphysical. The stability constraint on a complete sphere turns out to be less of a problem than it might seem, but there are still huge issues with stresses - Sphere Quakes. And before you can build a full Sphere you have to build a partial Sphere. Which is where stability will really kill you. Dyson Swarms might be more practical, but you still have a computability problem because you have an insanely huge number of objects in orbit and you somehow have to keep them from colliding with each other. Not so much a three body problem as an n body problem. With a built-in light lag delay of (at least) minutes. I'm not sure if anyone has modelled that, but it would be hilarious if the computing and station-keeping power requirements turned out to be a significant proportion of the available energy,
- rini17 5y ago
  But you did not exhaust all the options. What about spherical constellation of energy gathering sails that stay mostly in place? Can autonomously maintain their position with help of solar wind.
  - perihelions 5y ago
    Or even pure radiation pressure. They balance out somewhere around 10^-3 kg/m^2; thinner than that and you have a solar sail.
  - PeterisP 5y ago
    > spherical constellation of energy gathering sails that stay mostly in place? Wait, what? You can't have a spherical constellation of unconnected stuff that mostly stays in place, that's not how orbits work. You can have a single orbital ring, but a sphere consisting of many circular orbits would have these orbits intersect with very large relative movement. If you're thinking about non-rotating constellation where the gravitational pull is balanced by solar wind, the problem is that they have gravitational interaction with each other and the planets so it's inherently unstable, they would "want to clump up" and as soon as they do, the balance is disrupted as the same mass has less solar pressure and it starts to fall into the sun.
    - rini17 5y ago
      To me it sounds like "flight heavier than air is impossible!!!!". Why would a device that has 1kW/m2 at its disposal at all times, be fundamentally unable to counteract gravitational interactions? We are not talking about planetary gravity wells here but much weaker ones.
edgyquant 5y ago
It’s probably just that colonizing the entire galaxy is really hard and no society ever has an economic need to. Populations don’t expand exponentially forever, the recent explosion is an effect of the industrial revolution, and any species that gets a certain size breaks up into subspecies and starts competing with each other. There could very well be individual dyson swarms out there and we haven’t seen them or haven’t realized that’s what they are. But building them around every star in the galaxy is something I’ll never understand why it’s taken as a given.

by rini17 5y ago

TheOtherHobbes 5y ago

Dyson Spheres are fundamentally unphysical. The stability constraint on a complete sphere turns out to be less of a problem than it might seem, but there are still huge issues with stresses - Sphere Quakes. And before you can build a full Sphere you have to build a partial Sphere. Which is where stability will really kill you. Dyson Swarms might be more practical, but you still have a computability problem because you have an insanely huge number of objects in orbit and you somehow have to keep them from colliding with each other. Not so much a three body problem as an n body problem. With a built-in light lag delay of (at least) minutes. I'm not sure if anyone has modelled that, but it would be hilarious if the computing and station-keeping power requirements turned out to be a significant proportion of the available energy,

rini17 5y ago
But you did not exhaust all the options. What about spherical constellation of energy gathering sails that stay mostly in place? Can autonomously maintain their position with help of solar wind.
- perihelions 5y ago
  Or even pure radiation pressure. They balance out somewhere around 10^-3 kg/m^2; thinner than that and you have a solar sail.
- PeterisP 5y ago
  > spherical constellation of energy gathering sails that stay mostly in place? Wait, what? You can't have a spherical constellation of unconnected stuff that mostly stays in place, that's not how orbits work. You can have a single orbital ring, but a sphere consisting of many circular orbits would have these orbits intersect with very large relative movement. If you're thinking about non-rotating constellation where the gravitational pull is balanced by solar wind, the problem is that they have gravitational interaction with each other and the planets so it's inherently unstable, they would "want to clump up" and as soon as they do, the balance is disrupted as the same mass has less solar pressure and it starts to fall into the sun.
  - rini17 5y ago
    To me it sounds like "flight heavier than air is impossible!!!!". Why would a device that has 1kW/m2 at its disposal at all times, be fundamentally unable to counteract gravitational interactions? We are not talking about planetary gravity wells here but much weaker ones.

edgyquant 5y ago

It’s probably just that colonizing the entire galaxy is really hard and no society ever has an economic need to. Populations don’t expand exponentially forever, the recent explosion is an effect of the industrial revolution, and any species that gets a certain size breaks up into subspecies and starts competing with each other. There could very well be individual dyson swarms out there and we haven’t seen them or haven’t realized that’s what they are. But building them around every star in the galaxy is something I’ll never understand why it’s taken as a given.