3 ms·

Regarding alien life and search for it, I have really big problem with concept of Dyson Sphere/Swarm. The moment when human race will be able to build such mega

Regarding alien life and search for it, I have really big problem with concept of Dyson Sphere/Swarm. The moment when human race will be able to build such megastructures, it is very likely that long time before that fusion generators will be about as common as a smart phone and probably with a same size. Furthermore matter is just condensed energy, so why bother with some wonky immobile megastructure when you can just decay your everyday trash into pure energy.

randomname93857 3y ago
>> Furthermore matter is just condensed energy, so why bother with some wonky immobile megastructure when you can just decay your everyday trash into pure energy. True, matter is an energy... however the only known way to convert matter into pure energy is to make it annihilate with antimatter ( akin to electron-positron). We first have to have a good and cheap source of antimatter! And the matter annihilation may still generate a lot of particles/matter - that may be a waste (or not) depending what you do with that further. A Partial conversion of a matter into energy is also fusion and fission reactions, but they are limited by the difference between source and end element of reaction here https://en.wikipedia.org/wiki/Iron_peak#/media/File:Binding_energy_curve_-_common_isotopes.svg https://en.wikipedia.org/wiki/Iron_peak#/media/File:Binding_... - e.g. H2 -> He3, That uses only a tiny portion of matter, no energy that can be extracted from Fe56 (max), and all its close elements are also useless for either fusion or fission energy extraction.
XorNot 3y ago
We're closer to building a Dyson swarm today then we are to workable fusion reactors though - as in, we technically have the technology and means to start building one right now - a series of solar-harvesting satellites in Earth-halo orbits beaming microwave power back towards us. It would be inefficient, but there is no physical reason we couldn't do it. The other problem is scale: Dyson swarm power levels are orders of magnitude greater then the amount of deuterium in the Earth's oceans. At those sort of levels, you can't use fusion because you don't have the fuel. Finally, based on what we know there's some real problems with compact fusion: ITER and other big vacuum vessels are because we're at the materials science limits of how strong magnets can be without destroying themselves.
- TheLoafOfBread 3y ago
  The first problem with microwave beam is that it can be used as a weapon and will be treated as such. So I don't believe it will get over prototype test phase before being banned like nukes. Additionally the further you are going to be from such beam, the less energy you will get from it. So transferring any energy from the Sun will be extremely inefficient endeavor. Another big problem with nodes in Dyson swarm is heat, or the inability to get rid of it. They need to be close to the star so they can get as much energy as possible so they will heat up by position, but also modulate this energy and transfer it further, which won't happen without loses. So nodes can be constructed on gigawatt output but in reality be able to do fraction of that, otherwise they would fry itself up.
chillfox 3y ago
A Dyson swarm does allow you to move the star or sterilise any planet in the galaxy by focusing the light into a “death ray”. So it’s a useful tool to have for more reasons than just energy.
- fbdab103 3y ago
  Even if you could refocus all of the sun into a single direction, over stellar distances, wouldn't it have dispersed into nothing more than a bright star? What is the range of a putative Sol death ray?
  - naasking 3y ago
    How would it disperse? There's little matter to disperse it over interstellar distances. Very little energy would be lost if it were properly focused.
  - hansvm 3y ago
    "Dispersion" as I think you're describing is an artifact of the fact that most light sources radiate spherically, and more focused alternatives simply reflect the edges of that sphere to obtain some focus at larger distances, still radiating off in a 1/r^2 nature eventually. If you actually take every photon from Sol and point it in a single direction (think "LASER" rather than "mirrors"), the range is infinite, give-or-take the fact that you'll hit some objects on the way, and the intensity is on par with the intensity next to the surface of the sun.
    - fbdab103 3y ago
      Even laser beams diverge, so that is where my intuition is headed. Plus the engineering implausibility of perfectly aligning every photon to go in the same direction.
      - hansvm 3y ago
        I see. If we're willing to suspend disbelief enough to say that we can focus a star in a direction, I think it's reasonable to assume we'll get the rest of the engineering "good enough." The only hard limits I'm aware of are the engineering (which we're ignoring), and diffraction (which is small, I'll touch on). Diffraction-limited lasers have a wavelength / diameter term in the mix, so the relative increase in beam diameter is miniscule at any reasonable scale (doubling at 650M light years, tripling at twice that, quadrupling at 3x that, and so on linearly). Surface power scales with the inverse of that squared. The engineering is pretty obviously going to be the dominant term. Even with some lasers we've already created (not to mention more exotic forms of wave propagation), dispersion (diameter) would be on the order of 750x at 1 light year, or ballpark 1.1e2 watts per square metre if I haven't screwed up too much arithmetic, contrasted with the 1.4e3 or so we experience on Earth when measured in a plane normal to the Sun and the roughly 6.3e7 you get on the surface of the sun and the roughly 5.6e4 where no matter your orientation if you didn't have protection or active cooling you couldn't prevent death by overheating just via sweating (that last threshold you hit from this hypothetical laser at 0.045 light years -- a small chunk of the way into the oort cloud). How much better will we get the engineering between now and then? Who knows, but the math in that regime is _almost_ linear, and if you halve the angle of dispersion you double the distances in question for a given power flux.
l33tman 3y ago
You can use the dyson structure for other things.. there is a (sci-fi'esque) suggestion called a Matrioska Brain I think, where the entire dyson structure is made of computational substrates - it could be conveniently powered by the solar radiation but also by fusion. Given the track of AI and realistic world sims, everything might end up "living" inside one of those structures.. You would have to protect it pretty decently though..
- __MatrixMan__ 3y ago
  protect it... like running more than one instance of everybody so that we still experience continuity when a bolide strikes a compute node? Or like, we build a wall?
  - burnished 3y ago
    Por que no los dos?
    - __MatrixMan__ 3y ago
      Because it's unclear where you'd get the mass for the wall. Seems better to just let the nodes fail sometimes and tolerate the unreliability in a RAID sort of way.
- TheLoafOfBread 3y ago
  > Matrioska Brain I think, where the entire dyson structure is made of computational substrate Well let's compare star to the amount of available material in Solar System - I don't think that there is enough material to build one layer, let alone several + protective layer.
naasking 3y ago
Power output of a fusion reactor scales with something like the fourth power of the radius, IIRC. I don't think they're going to be able to build a reactor the size of their sun, so capturing that energy still seems pretty useful for large-scale efforts, like moving ships between star systems at near light speed.
- TheLoafOfBread 3y ago
  Power output is for sure important, but 1. Being able to take your power source with you, so it also works behind nearest asteroid is even more important 2. Having your own source, so not to be dependent on one megastructure, because it is a single point of failure and single point of control of civilization.

randomname93857 3y ago

>> Furthermore matter is just condensed energy, so why bother with some wonky immobile megastructure when you can just decay your everyday trash into pure energy. True, matter is an energy... however the only known way to convert matter into pure energy is to make it annihilate with antimatter ( akin to electron-positron). We first have to have a good and cheap source of antimatter! And the matter annihilation may still generate a lot of particles/matter - that may be a waste (or not) depending what you do with that further. A Partial conversion of a matter into energy is also fusion and fission reactions, but they are limited by the difference between source and end element of reaction here https://en.wikipedia.org/wiki/Iron_peak#/media/File:Binding_energy_curve_-_common_isotopes.svg https://en.wikipedia.org/wiki/Iron_peak#/media/File:Binding_... - e.g. H2 -> He3, That uses only a tiny portion of matter, no energy that can be extracted from Fe56 (max), and all its close elements are also useless for either fusion or fission energy extraction.

XorNot 3y ago

We're closer to building a Dyson swarm today then we are to workable fusion reactors though - as in, we technically have the technology and means to start building one right now - a series of solar-harvesting satellites in Earth-halo orbits beaming microwave power back towards us. It would be inefficient, but there is no physical reason we couldn't do it. The other problem is scale: Dyson swarm power levels are orders of magnitude greater then the amount of deuterium in the Earth's oceans. At those sort of levels, you can't use fusion because you don't have the fuel. Finally, based on what we know there's some real problems with compact fusion: ITER and other big vacuum vessels are because we're at the materials science limits of how strong magnets can be without destroying themselves.

TheLoafOfBread 3y ago
The first problem with microwave beam is that it can be used as a weapon and will be treated as such. So I don't believe it will get over prototype test phase before being banned like nukes. Additionally the further you are going to be from such beam, the less energy you will get from it. So transferring any energy from the Sun will be extremely inefficient endeavor. Another big problem with nodes in Dyson swarm is heat, or the inability to get rid of it. They need to be close to the star so they can get as much energy as possible so they will heat up by position, but also modulate this energy and transfer it further, which won't happen without loses. So nodes can be constructed on gigawatt output but in reality be able to do fraction of that, otherwise they would fry itself up.

chillfox 3y ago

A Dyson swarm does allow you to move the star or sterilise any planet in the galaxy by focusing the light into a “death ray”. So it’s a useful tool to have for more reasons than just energy.

fbdab103 3y ago
Even if you could refocus all of the sun into a single direction, over stellar distances, wouldn't it have dispersed into nothing more than a bright star? What is the range of a putative Sol death ray?
- naasking 3y ago
  How would it disperse? There's little matter to disperse it over interstellar distances. Very little energy would be lost if it were properly focused.
- hansvm 3y ago
  "Dispersion" as I think you're describing is an artifact of the fact that most light sources radiate spherically, and more focused alternatives simply reflect the edges of that sphere to obtain some focus at larger distances, still radiating off in a 1/r^2 nature eventually. If you actually take every photon from Sol and point it in a single direction (think "LASER" rather than "mirrors"), the range is infinite, give-or-take the fact that you'll hit some objects on the way, and the intensity is on par with the intensity next to the surface of the sun.
  - fbdab103 3y ago
    Even laser beams diverge, so that is where my intuition is headed. Plus the engineering implausibility of perfectly aligning every photon to go in the same direction.
    - hansvm 3y ago
      I see. If we're willing to suspend disbelief enough to say that we can focus a star in a direction, I think it's reasonable to assume we'll get the rest of the engineering "good enough." The only hard limits I'm aware of are the engineering (which we're ignoring), and diffraction (which is small, I'll touch on). Diffraction-limited lasers have a wavelength / diameter term in the mix, so the relative increase in beam diameter is miniscule at any reasonable scale (doubling at 650M light years, tripling at twice that, quadrupling at 3x that, and so on linearly). Surface power scales with the inverse of that squared. The engineering is pretty obviously going to be the dominant term. Even with some lasers we've already created (not to mention more exotic forms of wave propagation), dispersion (diameter) would be on the order of 750x at 1 light year, or ballpark 1.1e2 watts per square metre if I haven't screwed up too much arithmetic, contrasted with the 1.4e3 or so we experience on Earth when measured in a plane normal to the Sun and the roughly 6.3e7 you get on the surface of the sun and the roughly 5.6e4 where no matter your orientation if you didn't have protection or active cooling you couldn't prevent death by overheating just via sweating (that last threshold you hit from this hypothetical laser at 0.045 light years -- a small chunk of the way into the oort cloud). How much better will we get the engineering between now and then? Who knows, but the math in that regime is _almost_ linear, and if you halve the angle of dispersion you double the distances in question for a given power flux.

l33tman 3y ago

You can use the dyson structure for other things.. there is a (sci-fi'esque) suggestion called a Matrioska Brain I think, where the entire dyson structure is made of computational substrates - it could be conveniently powered by the solar radiation but also by fusion. Given the track of AI and realistic world sims, everything might end up "living" inside one of those structures.. You would have to protect it pretty decently though..

__MatrixMan__ 3y ago
protect it... like running more than one instance of everybody so that we still experience continuity when a bolide strikes a compute node? Or like, we build a wall?
- burnished 3y ago
  Por que no los dos?
  - __MatrixMan__ 3y ago
    Because it's unclear where you'd get the mass for the wall. Seems better to just let the nodes fail sometimes and tolerate the unreliability in a RAID sort of way.
TheLoafOfBread 3y ago
> Matrioska Brain I think, where the entire dyson structure is made of computational substrate Well let's compare star to the amount of available material in Solar System - I don't think that there is enough material to build one layer, let alone several + protective layer.

naasking 3y ago

Power output of a fusion reactor scales with something like the fourth power of the radius, IIRC. I don't think they're going to be able to build a reactor the size of their sun, so capturing that energy still seems pretty useful for large-scale efforts, like moving ships between star systems at near light speed.

TheLoafOfBread 3y ago
Power output is for sure important, but 1. Being able to take your power source with you, so it also works behind nearest asteroid is even more important 2. Having your own source, so not to be dependent on one megastructure, because it is a single point of failure and single point of control of civilization.