Suppose a planet/space station is a hollow sphere, and in the center of this sphere is a smaller sphere. This sphere would be solid, with grass and dirt like Earth. The only thing holding this smaller (but still big enough for people to live on, with a circumference of a few miles) sphere are 6 beams, attached to the inside of the outer sphere.

Civilization is mostly on the outside of this sphere. However, a small group of people live on the smaller sphere, without knowledge of this outer civilization. This smaller sphere has basically no technology at all, and must live off of what they have.

They are on this small sphere for a purpose – but what?

I have considered a few ideas. Maybe this sphere is actually a large generator that powers the outer dome, with electricity sent through the beams. It can also be a gravity generator or a gyroscope. The people there would basically be the "maintenance crew" for the sphere.

I don't know how well these would work, because maintaining an engine with basically no technology or knowledge of it does not make sense.

The smaller sphere is obviously of critical importance, and an explanation to why the people who live on it are isolated would also help the storyline.

What would this small sphere be for?


On the underside of the larger dome are lights that allow crops to grow, that dim and brighten according to a 24 hour cycle.

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    $\begingroup$ @HDE226868 I removed the space-station tag because I realized that it is intended for objects that orbit other objects in space, which does not really apply to my question. $\endgroup$ – erdekhayser Jan 4 '15 at 1:21
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    $\begingroup$ I'm having trouble with the smaller sphere having "no technology at all, and must live off what they have." This, combined with the fact that no light is going to hit the smaller sphere means you're going to need an ingenious way to get enough energy to the smaller sphere to grow food. Knowing how you plan to do that may help shape answers. $\endgroup$ – Cort Ammon Jan 4 '15 at 7:43
  • $\begingroup$ @CortAmmon I forget to put in a detail apparently. On the underside of the larger dome are lights that allow crops to grow, that dim and brighten according to a 24 hour cycle. $\endgroup$ – erdekhayser Jan 4 '15 at 15:14

One possibility is that people moved to the inner sphere to protect them from something that happened a long time ago. For whatever reason, they did not have sufficient resources to maintain their technology (or were saved by an outside force with greater technology).

If the people on the outer sphere know about the inner sphere or at least know that they are supposed to maintain power to the inner sphere, then the outer sphere can be the caretakers. Perhaps they have forgotten why they maintain things and just know that they are important. They may even think that the technology exists to protect them. So they keep the power running to the lights.

Alternately, the construct could have been created by someone with much greater technology. Perhaps a great empire saved its royal family and retainers but forgot to include those capable of maintaining the technology. Whatever they did has lasted though...at least this long.

A third possibility is that some outside force transplanted the people to the inner sphere. They may have been saving the people of the inner sphere from catastrophe or they may have simply been setting up a lab with study subjects. In this case, the inner sphere people have no concept of technology. They may even be more advanced now than they were originally. Fortunately, even after the sphere's creators have left, their work has kept running...at least so far.

With either of the last two, the outer sphere people may be totally unrelated to the inner sphere people. They found this seemingly empty planet and know nothing about what lies inside...yet.

If none of these help support your story, you might want to explain more about why you want people on two separate but cocentered spheres. Also, why do the inner sphere people need to be primitive?


I could see these people being essential for a balance of some sorts. It's easier to solve problems with less force when you are near the root of a problem. If there was something about this outer-sphere which was inherently unstable, the only potential way to balance it might be to put sentient beings down in the core to work.

Just to throw out one plausible scenario: a benevolent race of creators realized the planet was in trouble. Its magnetic core was failing. The temperatures in the core were getting too cold to support the liquid nickel needed to cause a magnetic field. It was solidifying. They realized that, while they might survive, the planet was at risk once the magnetic field dissipated (due to radiation that magnetic fields deflect). They hollowed out the core, cooled it down to where average beings could live, and installed a magnetic generator. The only problem was that this destabilized plate tectonics. Cooler core means less movement, and earthquakes would ravage the world unless a select few dedicated themselves to balancing the plates, shifting them millimeters one way or the other for eons.

Also worth noting, unless you have gravity generators, the denizens of this inner sphere would not live on the surface of the sphere. At the center of a planet, you are nearly weightless. They would inhabit the entire spherical shell of space between inner and outer spheres, floating effortlessly between them.

  • $\begingroup$ I don't think your final paragraph is correct. The outer shell doesn't provide any net gravity, true (assuming spherical symmetry), but the inner sphere provides all the gravity is would normally provide. If the inner sphere is like the Moon, it would have Moon-like gravity. If it was like the Earth, it would have Earth-like gravity. Etc. $\endgroup$ – Charles Jan 4 '15 at 21:19
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    $\begingroup$ @Charles: You are correct. However, from the question, the inner sphere only has a circumference of a few miles. It will have normal gravity a. la. Newton's Universal Gravitation, but it will be negligible unless some hand waving is done to enhance said gravitational effects. $\endgroup$ – Cort Ammon Jan 4 '15 at 21:25
  • $\begingroup$ Ah, I missed that. Then yes, it would be quite weak -- maybe 1/10,000th of Earth's. It would take you more than a day to fall from the outer shell to the inner sphere! $\endgroup$ – Charles Jan 4 '15 at 21:32
  • $\begingroup$ And you'd be able to jump off the inner sphere and get to the outer sphere to escape; things in motion stay in motion. And the escape velocity is negligible without artificial gravity for the inner sphere. Or climb the 10,000 ft. tree that grows in almost non-existent gravity. $\endgroup$ – user3082 Sep 28 '15 at 4:51

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