EDIT: It occurred to me people might not want to follow the links, so the TL:DR version of the question is this: "Realistically, how thick would this have to be to be habitable, farmable and stable enough to hold up cities?"

I asked the question originally here:


I deleted it based on feedback.

I also asked in on the worldbuilding beta here:


I edited the question down when I realized it was too broad but it still got closed.

Is there a way I can ask the question on stack exchange? If so, what site would you recommend?

Also note this question on SF&F Meta: https://scifi.meta.stackexchange.com/questions/8028/when-is-science-fiction-existing

Some good back and forth in the comments, but the gist I get is that they don't want any non-published materials discussed there. So here I am, hoping to not get dumped on by yet another community. Any help would be greatly appreciated.

2 Answers 2


I think Worldbuilding is the best home for this. I took a look at the question there, and I'm a little confused by it. Maybe others are too. What is the purpose of the alien shell -- why are they building this? I think if you can describe it in a little more detail, you could get this reopened on Worldbuilding. (Beware of "idea-generation" questions, but describing a desired outcome and asking how to get there can work.)

The best approach, I think, would be to ask on Worldbuilding Meta what needs to happen for the question to be reopened. The community there is pretty helpful and wants to see people succeed; if you ask on meta what the issues are, I expect you'll get helpful feedback.

Writers isn't the right place; it sounds like you're trying to figure out what to write or how some aspect of your world works. Writers is targetted for writing questions once you know what you want to write.

I'm sorry you've been getting a bit of a run-around.

  • 1
    The problem is the question is broad, I know that. The original on worldbuilding got edited way down. I was trying to be broad enough to provide context without being too specific. The fear of sharing too much is real. Writers helps with quality and SF&F isn't mostly writers. On worldbuilding I'm a lot more hesitant to overshare because my world is my baby. In terms of what I'm looking for, I genuinely think I'd get the best answers from pure science sites, but I'm not sure if they do fiction. It might be time to just start inviting some professors to lunch like a real writer... Feb 1, 2016 at 5:00
  • @StevetheMaker concern about sharing too much has come up before on Worldbuilding; this meta post is relevant. Feb 1, 2016 at 16:40

The original question, as I understand it from the second link, is about a science fiction scenario—aliens have built a solid sphere around the earth, and you want to know how thick it would have to be to avoid falling in pieces.

Imagine this. You take a long wall, and suspend it 50 feet above the ground. How thick does the wall have to be to avoid the bricks at the bottom from falling down? The answer is that thickness as such doesn't have much to do with it. A brick at the bottom of a low wall will fall as readily as the brick at the bottom of a high one. As it becomes larger, its behaviour becomes more like a sheet of floating sand. Think of the way the earth's surface, solid rock, is bent and twisted by geological forces.

If it were me, I'd invent some magical substance that has the properties you need. Thin as an eggshell. Part matter, part force-field. Etc. Or make sure each section of it is independently supported by antigravity pods.

But if you want to know the physics, you might take a look at some of the discussions about Larry Niven's "Ringworld" (a circular structure around a star) and Dyson spheres (a sphere around a star). Assuming the structure doesn't fall apart (most real matter will), the next question is whether it would be stable, or whether one side of it would fall towards the body it surrounds. (Answer: usually unstable.)

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