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This is a follow-up question to Building a Dyson sphere while preserving moons/other objects?. User @Goodies answered my question with opting to harvest nearby stars. The problem here is that harvesting other star's planets would eliminate the opportunity of harnessing the energy of those stars because there would be nowhere to store the energy. Another potential problem is that you wouldn't have the resources to build one until you rip apart a whole star, which defeats the purpose as there isn't a star to be contained unless mass interstellar transport is developed (essentially delivering a few Jupiter masses worth of Dyson stuff to a nearby star within a few hundred or thousand years). With these concerns in mind, when are Dyson spheres worth the material expenditure and is there really a point?

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In Charles Stross' Accelerando when humanity has built a Dyson sphere around the Sun, it is in the stage of transhumanism, where humans exists as entities in a calculator, not as physical entities.

In such a scenario that you have eaten an entire solar system to build the sphere is of little relevance, because you just need the calculator to host your mind.

Also in a different scenario, you don't build where you farm: you take the energy from a Dyson sphere in A to use it in B, which is not necessarily in the same stellar system. Same as what happens with power plant today: you don't have a power plant in Piccadilly Circus or Times Square, you use there the energy produced somewhere else and transported there.

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Some civilizations may prefer space habitats over living on planets.

Although a future civilization may have control of their planet so natural disasters are no longer an issue as they control the weather and plate tectonics, Asteroids and supernova will still be a problem. Its much harder to propel a planet at speed than moving space habitats. large enough habitats could have nature reserves and bodies of water so it does not feel like a sterile hunk of metal.

The swarm could only use what light is harvested as a constant power source rather than trying to store it, until they have more theoretical methods. They could easily move from star to star when they have milked the star for all it has, either through solar harvesting it for its life-span or star lifting its material.

With all things considered a swarm could provide a much safer environment with all the perks and beauty of living on a planet.

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The point of Dyson swarms is to provide energy for the local population. Emphasis on swarm to indicate it need not be a complete structure to be useful.

If a society wants to support ever larger populations they require an ever larger energy supply. Due to FTL not being a thing in the nonfiction universe a Dyson swarm is one of the few ways to accomplish this.

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They Aren't

Dyson spheres (and all their mega-structure ilk) are cool juju for science fiction, but there's little to no way they can ever be practical because the cost of moving, constructing, and maintaining the structure is well beyond what we can imagine today as sensible.

Granted, supporters point out (and rightfully so) that the future can include marvelous developments that would allow such structures to be super-thin, super-light, super-easy and super-cheap to construct.

Unfortunately, human history as it stands doesn't suggest that will be the case.

Worse, there's two problems with the fundamental reasons why these structures would exist

First: The idea of storing the energy output of an entire star for even a second is breathtaking. It means your civilization's battery tech is way, way, way beyond it's energy-creation tech. The total power output of the sun is estimated to be 3.8e26 W. Compare this to our estimated total energy consumption today of a scant 1.77e13 W. You're talking about storing 1,000,000,000,000X more energy than our whole planet consumes right now.

Second: What would be the consequences of having all this energy? Storing it means only that a greater amount of energy is available "on demand" than might be available directly at any given moment.... So, what do you do with it, and what would be the consequences of having that much energy somewhere nearby?

That second question is ignored by most SciFi writers. If you dumped a trillion times the energy usage onto the Earth, what would happen? (That might be a pretty good question to ask on this Site all by itself....)

Conclusion

Granted, it's only my opinion, but I can't see a way to make Dyson Spheres (etc.) practical without invoking Clarkean Magic. I can't see a way to make them useful without invoking more Clarkean Magic. And to add one more thing, I can't imagine any power source more difficult to defend against enemies than a Dyson Sphere.

But addressing all those issues is what Science Fiction is all about, right?

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  • $\begingroup$ Well made points, and hard to dispel, however at the same time; the potential living area of a Dyson sphere is 2.83 × 1017 km2 compared to 148940000 km2 for Earth. IF a race is in need or capable of utilizing such a ridiculous area of land. I do not see the issue with putting forth the effort to construct such a structure. There is little hard true logic behind the pyramids or climbing Everest. $\endgroup$
    – Gillgamesh
    Jan 13, 2022 at 16:38
  • $\begingroup$ All statements i see in this answer are valid-except two. A solid, dyson sphere as OP talked about is impossible unless some sort of magmatter or clarkean magical material is discovered. Other megastructures are possible, and even practical. For example, a dyson SWARM would be extraordinarily useful both for energy production and habitation for a population numbering in the quadrillions, perhaps even more(and yes, if human progress continues without major mishaps, we will have a population of quadrillions one day or another, maybe in a thousand years). $\endgroup$
    – Sync
    Jan 14, 2022 at 21:02
  • $\begingroup$ The second statement i have a issue with is that you think that a sphere, harnessing the power of a whole star, would have trouble protecting itself. Seriously. If a force can create a real, true dyson sphere, would it not be reasonable to assume that it would possess immense production and space-faring abilty? Honestly, the forces you would be dealing with are impossible for the human mind to comprehend. And also, you could create a literal death star if you needed(nicoll dyson beam). $\endgroup$
    – Sync
    Jan 14, 2022 at 21:04
  • $\begingroup$ @Gillgamesh Yes, harking to Niven's Ringworld, Someone may build one simply becaues they can and populate it because either no other world in the system is now habitable (no sun) or every planet, asteroid belt, and a good chunk of the Oort cloud was used in its construction. However, your point about logic is certainly germaine - humans do things. It doesn't always make sense. Frankly, my biggest problem is what would anyone do with that much energy? You'd almost need to populate it just to justify it. $\endgroup$
    – JBH
    Jan 16, 2022 at 23:50
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    $\begingroup$ @Sync (a) Whether or not other mega structures are practical is irrelevant. The OP didn't ask about them. (b) The moment you said "reasonable to assume" your point was lost. $\endgroup$
    – JBH
    Jan 16, 2022 at 23:52

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