# Alternative to gravity inside a Dyson Sphere?

On the inside of a Dyson sphere there is effectively no gravity. Is there an alternative method to keep people on the inside surface from floating around?

I know it could spin and that would keep them down in a small ring around the equator, but is there a way to apply a 'downward' force equally? Could atmospheric density or buoyancy be reversed? Or maybe a fictional element is required?

It doesn't have to be 1g but the closer the better. To clarify, there is only 1 sphere, people live on the inside, the population is several orders of magnitude more than ours.

Edit: After a few answers, I'm starting to think I might need a graviton controlling element. Any suggestions?

• @RonJohn, not necessarily. Artificial gravity (apart from that generated by rotation) is not known to be possible, and therefore even a K2 level civilization may not be able to generate it. – Gryphon - Reinstate Monica Aug 3 '18 at 2:00
• I suspect the "small ring" around the equator would be large enough to give every person currently living on Earth their own private continent. – plasticinsect Aug 3 '18 at 2:24
• This is just one reason why Dyson Swarms are preferred over Dyson Spheres. – StephenG Aug 3 '18 at 4:11
• A 2 layer dyson sphere that your people on the "inside surface" are really sandwiched between the two layers. The smaller layer acts as the floor (the gravity from the star pulling them towards it) and the outer layer is just there to fulfill the requirement of not being exposed to space (and technically being inside a dyson sphere). "Down" is relative to what direction you're facing, but in this case it's pretty much "force that pulls you towards the surface of whatever you're standing on." By making use of the gravitational pull of the star you can avoid issues like floating into the star. – Aify Aug 3 '18 at 6:55
• Hi ZoneWolf. I edited out the last sentence of your question. If you feel that an answer is not helpful, then you can vote it down as not helpful. Part of our be nice policy is to assume good intentions. If you want answerers to pay particular attention to some area, there's no problem with adding something like "answers should elaborate on how they relate to X", but please take care to phrase it in a non-confrontational manner. – a CVn Aug 3 '18 at 9:36

You could spin the sphere, thus creating gravity on the equator and using the remaining internal surface (at 0g) for infrastructure/energy collection. This assumes that the material the sphere is constructed from is infinitely strong, as the forces created are massive.

As this question is posted in Worldbuilding, not experimental physics, perhaps the question should answer itself. There is no way, currently, to justify the creation of artificial gravity inside a sphere. You have built your world in a Dyson sphere; you should accept that zero gravity is part of that world.

Gravity is a pain in the backside anyway. Why would a space-faring civilisation go to such effort when they could just live on the outside of the sphere and harvest energy on the inside?

Imagine how much more interesting your world will be when you can throw a paper aeroplane and take someone's eye a hundred kilometres away. Physics gave you lemons; I say you juggle them - it's much more entertaining than pretending that they are oranges.

• I don't think you understood the problem OP is facing. See, Shell theorem. Essentially one of the things it states is that a spherically symmetric shell (such as a stable Dyson sphere) contributes no weight to objects inside it regardless of where they are. Increasing the mass of the shell has no impact on this fact. – AngelPray Aug 3 '18 at 8:16
• The force exerted due to gravity from a uniform shell on any point inside that shell is 0, this was even allude to in the question. Your proposed distance wrt temperature also makes no sense because Earth is only habitable due to a combination of day/night cycles, the atmosphere, and radiation shielding from the magnetosphere. A random spot in near-Earth space is lethal even if everything aside from the levels of visible light is manipulated to Earth level, you would basically be living under the noonday sun 24/7. – Teleka Aug 3 '18 at 8:34
• Thanks for the link, AngelPray. It's interesting, and I think it does prove what that my logic is flawed. My bad. – Inoutguttiwutts Aug 3 '18 at 8:37
• Edited to remove Bad Science. There's enough on the net already. – Inoutguttiwutts Aug 3 '18 at 8:47
• rotating the sphere would produce stress forces which would rip it apart. there's an article by Larry Niven somewhere where he mentions calculations which show that you need unobtainium to construct the ringworld - the argument is the same for a rotating sphere (probably worse) – ths Aug 3 '18 at 9:14

Electrostatic attraction.

Usually we think of electrostatics operating on small scales - like cat hair sticking to a balloon. But electrostatic attraction (and repulsion) can substitute for gravity in some situations. I put this idea forth in the linked Planet Walkers question, as a method to keep people who live on little asteroids from floating away.

The Planet Walkers - Feasibility

Electroadhesive robots have been constructed. From What sort of claws would be best utilized for melee combat and quickly scaling the walls of a modern day building?

By now, most roboticists are familiar with the myriad gecko-type robots that employ Van der Waals forces (created by microscopic synthetic setae) to cling to walls. Less well-known is the work on an electrically-controllable alternative developed by researchers at SRI International (formerly called Stanford Research Institute) called "electroadhesion". Impressively, the electroadhesive can support 0.2 to 1.4 N per square centimeter, requiring a mere 20 micro-Watts per Newton. This means that a square meter of electroadhesive could hold at least 200kg (440 lbs) while only consuming 40 milli-Watts, and could turn on and off at the flick of a switch! Read on for pictures, videos, and discussion.

So too your Dyson sphere. It maintains a charge on its surface adequate to produce intermolecular forces which replicate gravity, pulling down its inhabitants and the accoutrements of their world.

• This is awesome. I was thinking VDW forces could be a solution but didn't think it was strong enough. Since this would be the only noticeable force, it would be far more effective, as the only other force is the negligible pull from the sun. – ZoneWolf Aug 6 '18 at 6:09

Lots of ringworlds

You have a bunch of ringworlds at different angles until it covers the entire star. How are the ringworlds built? That is a question for you to answer.

I linked an interesting video on Dyson Spheres that I highly recommend you watch. (I got the ringworlds response from the https://www.youtube.com/watch?v=HlmKejRSVd8&vl=en

How far away is your Dyson Sphere from the sun? Three million kilometers away from the surface of the sun, you'd be seeing about a g of gravity on the surface of your Dyson Sphere.

$$F = G \times \left( \frac{Mm}{r^2} \right)$$

$$F = 6.674 \times 10^{-11} \times \frac{1.9891 \times 10^{30} ~\text{kg}}{(695 \times 10^6 + 3 \times 10^9)^2} = 9.7 ~\text{m/s}^2$$

Since you're able to build a Dyson Sphere, you should be able to store the sun's energy with a high degree of efficiency, making heat problems moot. Just make your Dyson Sphere smaller.

• 3 million km from the sun you would be incinerated instantly. Thats less than a tenth of mercury's orbital height. – ZoneWolf Aug 3 '18 at 11:04
• please note that this would be gravity pointing Towards the sun rather than towards the inner surface of the Dyson sphere. this solution would require the population to live on the outer surface of the sphere (though is still completely valid). – Ummdustry Aug 3 '18 at 15:58