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Favorite scifi concept?
(lemmy.ml)
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this post was submitted on 12 Jul 2026
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This is a bit of a general one, but I have a fondness for very large space structures. A number of my favorite scifi stories take the premise of "exploring a (usually abandoned or tech-regressed) alien megastructure".
Dyson spheres and ringworlds and stellar engines and the like are the obvious candidates, but honestly I like smaller (but still huge) ideas like oneill cylinder colonies just as much, because what I like in them is a function of both size and how close to understood physics they follow, and the latter tend to be easier to make plausible.
There's a certain sense of inspiration that comes of someone describing something almost incomprehensibly huge, explaining that it is designed by intelligent entities, and then justifying it with enough real science as to convince you that something at least somewhat like it really could exist, someday, or maybe already does somewhere out in the vastness of the universe.
I think my favorite megastructure is the shell world.
The idea is that you take a geologically "dead" world (no mantle movement / tectonic drift like earth) and start excavating a big underground space, with the aim of adding another 'level' to the world below the surface level (with periodic pillars to hold up the ceiling). The rock from that excavation could then be transported up to the surface to form another level above that (using nanotech assemblers or what have you). Rinse and repeat until you have a bunch of nested shells.
Each 'ceiling' could be covered in a light field that replicates the sky, including sunlight. The spaces would be large enough to have their own weather, so that wouldn't need to be faked. The levels would need to be actively cooled though. So the support pillars would need to have coolant tubes in them and the actual surface would need to be covered in radiators.
Now, imagine a structure like that which has broken down and fallen into disrepair. Some or all of those levels could be dark. A dead ecosystem and ruins of a civilization entombed in an artificial underworld. Or maybe the displays still work in a few places. A few isolated pools of light supporting the last plant life, which herds grazing animals have to migrate between periodically to avoid exhausting their food supply. And ambush predators evolved to wait in the dark until something gets close.
Im with you i love a good megastructure. I know the bobiverse books are a bit cheesy but I really enjoyed the oneill cylinder world that was the main focus of book 4 I think it was. Pushing Ice, Ringworld, and Rendezvous with Rama were all good as well. Got any other good superstructure stories I could get into?
You named virtually all of the ones I'd mention first lol. I guess I'd probably add "bowl of heaven" to that, I'm not sure it's design is the most plausible form for the concept really but it features a stellar engine (specifically, one using the star as a sort of rocket thruster, to move something like a ringworld around).
Megastructure Enioyer spotted.
Seeing the Beyond Coast space colony in Policenauts use the o'neill cylinder for its design was pretty cool. I think its the only time I have seen one in a video game, and pretty neat considering its age.