A Dyson sphere around a black hole

The additional benefit is the amount of power. With the power of a star at your disposal, beaming your energy using lasers and microwaves, even if only 1% efficient, would instantly solve the energy needs of any planet in a solar system. If we did it, we could instantly colonize all planets in our solar system because things like "running an AC on Mercury" or "Hovercraft in Jupiter Atmosphere" becomes trivial when you have limitless power.

Heck, you could start projects like moving planets in orbits or collecting astroids to built a planet if you wanted.

Black holes are the stage after that since you can use a spinning black hole to convert a given mass into energy at >10% efficiency (given E=MC^2). That would allow a civilization to power multiple solar systems at the cost of a few planets per year.

Granted, the sphere is difficult to build, but that is what you have dyson swarms for.

It's unstable without active stabilisation. The stabilisation has to be perfect because otherwise you get massive distorting spherequakes propagating through it, which will make it a very uncomfortable ride for a short time and will soon tear it apart.

A perfect spherical stabilising solution with components and sensors that are light minutes - or possibly light hours - from each other is impossible because of the signalling delays.

Ringworlds have the same problem. Even if the ring is made of infinitely strong unobtanium, it won't stay in a useful orbit for long enough to be built, never mind inhabited.

Swarms have more potential, because you can build them with sparse shells and move things around to handle instabilities. But you still need massive computational effort to keep swarm units from colliding with each other, possibly at very high speed.

None of this matters, because the limiting factor for civs is collective intelligence, not energy.

We already have access to far more energy than we could possibly use on earth for any technology that's actually buildable. But we're not using it because we don't have the species IQ to make the right choices.

This. The entire “moving planets” and “powering asteroids” theme is just a projection of our historical aggressive reproduction, which is not even a requirement for an advanced civilization. Earth alone could serve us a few billions of happy years, if we didn’t have the happy urge to multiply until critical shortage. That’s far from intelligent, imo.

With that, being happy does not seem to be a universal quality of life; some would even posit that the opposite is true (ask Gautama B.)

I don't see humans completely overcome their biological nature any time soon, if ever.

Humans are exceptional in this regard as that can expand beyond the limits, and at the expense of, all other known species. Humans are also exceptional in that they could extinguish themselves, either by choice on their own folly.

Not intentionally, but we've managed to create societies where reproduction is extremely costly in every conceivable way and are even working to convince people that reproduction is outright tyrannical, sexist, and environmentally genocidal.

The instinct will certainly remain, but population decline seems inevitable the way things are going. Even a few decades from now, the human breadbaskets of the developing world adopt the anti-natalist systems we have in the developed world.

Why couldn't a Dyson sphere have uncoordinated movement joints distributed all around to absorb those spherequakes? Or even active locally coordinated ones?

I'm sure a Dyson-sphere-building civilization would figure this out.

https://en.wikipedia.org/wiki/Projections_of_population_grow...

Repeat at 90 degrees, 45 degrees, etc until you have a sphere.

You're right that speed-of-light delays make negative feedback control difficult, but it might be possible to have rockets that sense local photon flux on the inner surface of the ring/sphere and fire autonomously when it increases.

Of course. But they reach a limit. Only one species is able to exploit resources, and the biosphere, to its own ends. Agriculture, mining, and technological advancement are peculiar to humans. All of these permit us to live longer, with fewer setbacks, and in environments no other animals can survive (space, and soon other planets). Are these not exceptional traits?

We can also engineer a virus, or deploy strategic weapons that could wipe out our entire species (and a bunch of others). Is that not exceptional?

But some animals have agriculture (ants?) and some plants exploit metals in the soil (phytomining)! Still, Sapiens are the champs.

That's just what species are selected for. If you have two competing populations and one multiplies and expands just slightly better than the other, everything else equal, then that one will eventually outcompete the slower one.

But it does not have to be that way. Humans are the top predator, so no competition here. We could make do with limiting expansion if we chose to. It's still life, but without this "quality" that you seem to consider a necessity.

And it's such a banal obvious claim I'm making, and yet it's being downvoted to oblivion. I can't imagine cane toads doing anything I mentioned.. or even ants having some sort of hegemonic control over the fate of all other species.

We have no predators but we do have a lot of existential threats. The more we spread out the more chances we have of surviving. If we sit on our hands and stay put we’ll wind up like the dinosaurs one way or another.

Yet there are actual dust rings and discs in the sky surrounding stars for long periods without falling into the star, being blown out of the gravitational influence of the star, or condensing into planets on life-evolving timescales.

Some of them are pretty occlusive and get hot (~ 1000 degC) and are consequentially observational targets for MATISSE at the European Southern Observatory. It's not at all my field, but I gather https://theskylive.com/sky/stars/kappa-tucanae-star is a principal hot dust belt target.

Retreating towards my islands of comfort, there are plenty of small rocky bodies ( flavour of "dust" in the sense of the previous paragraphs) in the solar system that are in no immediate danger of colliding, plunging inwards, or escaping to infinity in spite of ablation from solar radiation, differential radiation pressure and other effects that lead to the term "active asteroid". Most of them will be there, and have been there, for billions of years despite evil Jupiter trying to mess them up. Speculating a little away from my weak-gravity island, I would be surprised if there were no ongoing organic chemistry reactions in the more icy carbonaceous active asteroids in our solar system. It's not a huge leap from that to an asteroid-based power station that slowly produces some alcohol(s) at much denser concentrations than the wood alcohol molecular clouds like in W3(OH) astrophysical alcohol megamaser region. [1]

Icy-carbonaceous bodies in closer orbit and with sufficient spin angular momentum (perhaps supported by the Yarkovsky effect) for cheap thermal management could in principle host terrestrial photoautotrophs suitable for processing into biodiesel. Impractical at small scale, but maybe useful if one has many billions of such "power plants" around a single star. And of course, one could use the photoautotrophs to feed microbes more suitable for the production of more complicated molecules like, oh I dunno, oxycodone (for fun and profit).

(A sufficiently dense dust belt in the goldilocks zone could even make use of ideas from the panspermia hypothesis, so that one only has to populate an initial fraction of the bodies with economically useful microbes, and the little bugs will reproduce and spread throughout.)

One can easily imagine greater efficiencies from engineering non-organism power collectors and storage systems instead of adapting blue-green algae to output biological compounds, and one would probably want to do this for a dust that is in bulk much hotter than the vast majority of our solar system's asteroids tend to get, or if practically the entirety of the dust is manufactured rather than already in place ready for populating with mats or colonies of economically useful microbes.

Returning to the paper at the top, I think the only advantage a black hole gives is that a sufficiently large one might have a much larger localised "goldilocks" volume which one might seed with small icy-carbonaceous body light-powered power plants, compared to having many such belts around many many stars. However density of production could be an important advantage, even if one has to move a swarm of objects to it rather than adapt a swarm of substrate objects already in place.

Super-concisely: Earth has a lot of oil, inefficiently, seemingly by accident, after a long delay from initial "activation" of the biosphere, and with a fairly high collection cost because it below so much atmosphere (and water and rock) through which it would have to be lifted for off-world use. Sufficiently advanced aliens (and perhaps future humans), if they wanted oil, undoubtedly could do better than Earth.

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[1] http://www.star.bris.ac.uk/mark/w3oh.html but don't inhale it, the W is for Wood alcohol (hydroxymethane).

One solution is for the expansion joints to have infinite range— a disconnected swarm of platforms which is exactly what a Dyson swarm is.

If the argument is that somehow the former is more environmentally friendly, then I don’t understand why we should accept dystopia for an uncaring god.

That's an interesting take. It does seem that we're more limited by our poor choices than by underlying physical limits. We invest ridiculous amounts of money into weapons by comparison to things like nuclear and fusion power.

This is precisely the appeal of Larry Niven's Ringworld concept. You instead take a slice of that sphere and spin it around the star and generate gravity through centrifugal force. They can take a number of configurations but the default one would give you the equivalent of 2 million earth's worth of living space inside one continual surface. This is obviously hugely mass intensive and having a ring of that kind of radius spinning at the tangential velocities required for the equivalent of one g of simulated gravity (around 1200 km/s) requires materials so magically strong that they make graphene look like soggy tissues. The only material that could do this even in the theoretical realm is magmatter, which would be materials constructed out of magnetic monopoles, something that has been predicted to exist by some but has yet to be observed.

However, you could construct one using known materials by creating a superstructure around the ring that is much more massive and orbits the other direction at normal orbital speeds for a body about an AU out from the sun with the ringworld electromagnetically suspended from the superstructure, normalising their collective momentum to zero. That obviously greatly increase the mass requirements but this could mostly take the form of hydrogen and helium which is far more abundant than heavier elements and would be usable as fuel for fusion reactors. That superstructure can contain many smaller rotating habitats and the whole thing could be used as a vast habitat for microgravity living as well - something I envision as many humans doing as living on worlds with gravity by the time we would have constructed one of these.

You also want to have a superstructure because at such a high tangential velocity, if a human being of 80 kg struck the ring from the outside, it would blow with the kinetic energy of a thermonuclear bomb. Point defence is absolutely necessary and the superstucture offers both an excellent shield covering the non sun lit side of the ring and a great platform for hosting those point defence systems. Ringworlds are also not in stable orbital configurations over astronomical timescales so you need to maintain their orbit through corrective thrust. This could be done through light sails which would also be appealing for it's mechanical simplicity.

Ringworlds are very mass intensive especially if your civilisation still has no access to unobtanium building materials and I don't think this would be something we would ever build a lot of in our particular solar system but even with that mass cost, you could easily gather enough rocky material from the sun to build a few and still have the vast majority of people living in other far smaller structures (but only relative to a star encompassing ring) in the swarm.

I've heard Dyson spheres referred to as a K2 Civ's wonder or vanity project.

  Science advisor:
    Eternal leader, those pesky Alpha Centaurans just completed work on a galactic wonder, the Dyson Sphere! [+1000 energy, +100 habitat]
    Shall we redirect our own Dyson Sphere efforts to a new project?

  Eternal leader:
    Damnit! Yeah fine whatever, let's switch to building a Kemplerer Rosette.

Is this really the limiting factor? I've always assumed the limiting factor was distance. I can envision a species that is more intelligent or more altruistic. But what I can't envision is how collective action is coordinated over interstellar distances. It would seem to me that the extreme communication delay would cause any interstellar civilization to inevitably break apart into a bunch of separate "local" civilizations.

If tomorrow all ants disappear then most land-oriented ecosystems would just collapse.

We humans are having so egoistically anthropocentrical world views that it's not even funny anymore.

Solving world hunger does not need expansion. Stopping climate change does not need expansion. Preventing the upcoming antibiotics crisis does not need expansion. To the contrary, expansion makes all those things worse or has even started them in the first place.

This problem is twofold. First is that much food is produced far from many poorly nourished people. This problem is totally solvable by modern transport. There are enough charity donations to prevent hunger everywhere.

Second, and most importantly, it's the social structure what prevents ending the hunger where the hunger still is. People prevent production and distribution of food in order to keep the social structures where they are on top, or are fighting to be on top. They themselves are not hungry, and don't care about the rest much.

> Humans are also exceptional in that they could extinguish themselves, either by choice on their own folly.

Could you imagine ants finding a method to annihilate themselves? I don't claim that animals are unintelligent, but we are unique in our ability to create technology to achieve almost any goal, no matter goal's 'sapience'.

> If tomorrow all ants disappear then most land-oriented ecosystems would just collapse.

I don't dispute this, but it's completely orthogonal to my claim. Humans have disrupted the biosphere in a manner that is unprecedented since when meteor strikes and seismic events were still shaping earth

It's not very hard for ants to collectively commit suicide.

The age of star formation is mostly over yes, but not completely yet - and I believe it's figured that no red dwarf can have reached even a tiny fraction of its lifespan so far?