What is this and what does it do?

(this has got to play in the background)

The the belief that most matter is concentrated in galaxies is false. A relatively huge portion of the matter in our universe is concentrated there, the heaviest of building blocks having been forged in the hearts of collapsing stars and fiery deaths of neutron star collisions, but the vast majority is actually concentrated in the galactic filaments that weave through our universe like roots of a tree or the neurons of some cosmic brain.

Sadly, only a minuscule fraction of the matter in the universe are the heavy elements needed for technology, like copper, nickel, zinc, tin, platinum, gold and lead, all of which are heavier than iron, the nuclear ash of supermassive stars that can fuse past helium throughout their lives.

This means basically all of it is concentrated within galaxies where these stars form, live and die, and so this is what this great machine might fix for a Kardashev Type-3 civilization.

How might it work?

Even I don't pretend to know how one might be built and operated, but I have a basic operating principle in mind. The foundry itself would be built around a rotating black hole, most probably at the churning heart of a galactic quasar, where matter is already kicking up a storm.

As billions of solar masses are syphoned from the galactic filaments per second, they are poured down and into the quasar's accretion disk, converting massive quantities of mass into energy that is funneled into a relativistic jet. The heat and friction as the gas accelerates to a fraction of light-speed as it falls in would be harnessed by this machine to fuse elements, first with a positive net energy, and continuing past iron to fuse even heavier elements.

Such a machine would be beautiful and yet unfathomable in scale, the burning heart and crowning jewel of an intergalactic civilization which satiates its need for raw materials to continue its empire.

The setting for such a machine

After predicting and finally testing the first methods of inter-dimensional travel, a higher plane of existence is discovered, in which abstract concepts start to bleed into reality, and what we collectively believe begins to hold immense power.

This civilizations 'magic', as far as we understand it, directed the energy that permeates the universe to the whims of the minds of these aliens. Part of this technology is controlled by runes carved in stone, which seem to direct energy and hold complex instructions like code for a computer, so far beyond us it might as well be magic.

In this higher dimension, location, relative to our universe, stops making sense. It exists nowhere and everywhere, and controlling the construct that breaches out of this dimension and into the next, space can be traversed in an instant. In effect, teleportation.

But this discovery is their undoing. As they begin to experiment, they realize that there is something beyond this dimension, beyond all of them. A place where the writhing insanity of nonexistance is more than real. The darkness in the back of the minds of the depraved, incarnate.

As they test their machine once again, they realize they have breached reality itself and have begun an invasion of our world. With no way to undo it, they try to stop the Old Ones, cosmic beings of indescribable power, by with their immense knowledge of manipulating black holes, build the Barrier, a machine powered by the Penrose process and accelerated evaporation of a supermassive black hole, which will power the machine and lock away the Outsiders for as long as it continues running.

Why is it important for the story?

As the protagonist touches an inscription carved in stone and imbued with power, they witness a fractured memory of the Empire, a shard of which is the remnant of a space installation which became the moon of Neptune, Triton. Along with it they discover the ancient past of the millions of terraformed planets across the galaxy, and of a supermassive black hole which the forge was built around.

And so my question is this: How would this machine operate? Given the kinds of technology this empire would be using, they're knowledge and machinery to manipulate black holes, and extrapolations of it.

Is it even theoretically possible, in the same way as a black hole bomb is theoretically possible? I don't have a good understanding of the math and physics which operate around black holes, and don't know if such a structure has been theorized and by who.

Is this a believable megastructure for a Kardashev Type-3+ civilization to have built? And if so, how would the math pan out for the energy released by a black hole when fed matter as an accretion disk? Could it be usefully harnessed to make heavier-than-iron elements? How efficient would it be? (within a few orders of magnitude) As far as I understand, it's an efficient mass-energy conversion method, but I don't understand enough about black holes to be sure.


I should have properly specified that there would be independent infrastructure harvesting, processing and transporting the gas to the Foundry, on an equally massive scale. The black hole and the foundry built on it only process the gas into heavy elements for use as raw materials.

Not really concerned how they manage to do it, just that it is done. It doesn't seem out of character for a godlike civilization to be able to move billions of solar masses worth of mass in the blink of an eye, given that they've mastered black holes.

  • 1
    $\begingroup$ I'm going to +1 this question because I like "review my idea" questions and you used the word "believable" rather than "possible." Bless you for having a realistic expectation of what this stack can/will do. $\endgroup$
    – JBH
    Jun 15, 2023 at 5:44
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    $\begingroup$ You have an ancient civilization that accidentally summoned the Great Old Ones and you're concerned that their industrial particle accelerator is implausible? $\endgroup$
    – Cadence
    Jun 15, 2023 at 6:02
  • $\begingroup$ @Cadence Well... yes, because they later use this industrial particle accelerator to lock away the Old Ones in a magic bubble that we dumb ape-things manage to break. I add context about the whole Old Ones thing because I have more questions which link back to this, so might as well explain here. $\endgroup$ Jun 15, 2023 at 6:25
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    $\begingroup$ I realize that I never overtly state what the machine actually does. So here it is: It consumes the gas in the galactic filaments to generate energy (on the side) and fuse heavier-than-iron elements for the civilization to use as construction material, on an epic scale, solar masses worth per second. $\endgroup$ Jun 15, 2023 at 6:29

2 Answers 2


The the belief that most matter is concentrated in galaxies is false. A relatively huge portion of the matter in our universe is concentrated there, the heaviest of building blocks having been forged in the hearts of collapsing stars and fiery deaths of neutron star collisions, but the vast majority is actually concentrated in the galactic filaments that weave through our universe like roots of a tree or the neurons of some cosmic brain.

I'm afraid you have misunderstood galactic filaments. They are composed of "walls of gravitationally bound galactic superclusters", and yes, they are the same thing as "Galaxy filaments".

The filaments are mostly made of galaxies. There's no way that your machine can be fed at the rate of ". . billions of solar masses are syphoned from the galactic filaments per second . . ." unless you're gulping down galaxies. They're the only things that have enough mass to fulfil that criterion.

If you have wormhole methods of moving the mass faster than light, that solves part of the problem, but they're going to have to transport stars without dismantling them: you're talking about feeding your machine billions of stars a second, which means you need to create your wormholes up close to the stars, gulp them down, then turn off the wormhole and set up a new one a parsec or three away. If you can take a star every ten seconds with one wormhole generator, you need tens of billions of generators.

And that won't work at the necessary speed without an utterly ludicrous level of force pulling the star into the wormhole. If you can pass the gravity of your ludicrously massive black hole through the wormhole, that could do it, but that's rather hard on any equipment around the mouth of the black hole. You also need to apply some care that you don't gulp a star that's about to go supernova, since that's also a bit hard on your local equipment.

What do you plan to do about planets with life on them?

  • $\begingroup$ I should have specified and will edit, but no, mass isn't syphoned by the black hole itself, there is literally no way to do that with just a black hole and its gravity alone, but the civilization would have some equally extreme infrastructure to harvest feed gas, armies of autonomous harvester ships and thousands of wormholes to transport the material to the Foundry. $\endgroup$ Jun 15, 2023 at 13:31
  • $\begingroup$ But the important part isn't how the gas gets there, just that they can dump those quantities of gas down a black hole. $\endgroup$ Jun 15, 2023 at 13:32
  • $\begingroup$ Given the handwavium I just sprinkled on this, will it work now? $\endgroup$ Jun 15, 2023 at 13:38
  • $\begingroup$ @SamKitsune: It fails differently now. $\endgroup$ Jun 15, 2023 at 19:50

Could be believable if you were to feed it dark matter, it would increase the gravitational force around it and siphon a decent amount of those filaments, but i think you cant even on "believable" scale siphon billion of solar masses, how would you store it ? You would need a unbelievable giant storage system of at least "Million of solar masses" (assuming you could somewhat compact it), also that is universe destroying because if a blackhole would suck up billion of solar masses in seconds, theres nothing stopping it from consuming the whole universe , its just a matter of time.

With that out of the way, the best way i can think of would be to feed dark matter to the black hole and make it kind of a "super" black hole in order to fulfill your needs, or something different about it because all black holes cant consume billions of stars per second if you want it to be believable.In my opinion.

But i have to comeback to dark matter, its the only way i know of that could in theory be used to move masses through space without issue since they don't directly interact with it.

EDIT Since your edit provided more information, science-based tag would say that black holes don't transport matter, but ignoring that, yes it could work but unless you dump solar masses of gas in order to achieve your goals, as for a cap (Maximum amount of production) i cant be precise but i would say that more then the size of the black hole couldn't be produced in a second (you can justify with some pseudo-science that builds on the time difference that seems to occur the closer you get to black holes).

  • $\begingroup$ Sorry for not explaining it properly, but I added more context to the question in an edit. $\endgroup$ Jun 15, 2023 at 13:37
  • $\begingroup$ Its ok i edited the question based on your edit $\endgroup$
    – Or4ng3h4t
    Jun 15, 2023 at 14:06

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