Dyson Spheres?

Wouldn't units on the inside of a Dyson sphere fall upwards? I'm not sure how them being able to stick to the surface would work, considering the sun on the inside that would tug at them pretty seriously.

As far as I know they would be two layers rotating in opposite directions to create artificial gravity and thus no.

If the sphere rotates then there can be gravity, although at the poles there would obviously be none....


the alternative is magnetism.

One can only imagine how much power would be needed to move a dyson sphere like that.

Good thing they're essentially giant batteries

No, because it is still orbiting the sun and thus you get gravity due to acceleration. Unless you are referring to the Complete Sphere version which will fail on so many levels its hardly worth discussing

On top of that there is the mass of the Dyson Sphere itself, how much mass is present at any given point? How much gravity does it possess at any given point? how far from the sun is it? The sun has a vastly greater mass than the Earth and we dont go falling towards it.

If the sphere was built by a species anything like us then it stands to reason that it would be built approximately an AU from the star. A dyson sphere would likely be pretty thick, and might just have enough mass at any given point on its surface to exert a gravitational force that would compete with a star 1 AU away.

You'd only need energy to start it spinning. How big are the rocket engines that keep the Earth spinning while it orbits the Sun?

After that it'll happily carry one forever until you smash stuff into it.

On the poles? Yes. A full sphere would be extremely impractical for that reason alone. The difference in acceleration along various lines of latitude would also create massive stresses on the structure itself.

Ringworlds don't suffer those issues, making them a far more practical "impossible world" to make.

That would work for a ringworld only anyway. A Dyson shell would crumble on itself at the poles, where there is no rotation to counter the star's gravity. Even if you did build a Dyson shell in a material hard enough to not crumble on its own weight (which should be impossible as far as we know today), then there is another problem. The star being inside the shell, the shell's gravity don't affect the star and it can move freely (or the shell can move freely around the star). Which means that unless you always correct the shell's position, the star will end up hitting a wall.
Which is why Dyson never thought about a solid shell for the sphere. He was talking about a swarm of orbiting solar collectors.

Instead of satellites, though, you could use statites (that stay stationary by being solar sails and being pushed by the Sun's radiations/solar wind). From there, it's possible to imagine a Dyson sphere made of a continuous surface (I call it 'Dyson bubble'). It would in fact be a giant spherical statite around the star, maintained in place and shape by the solar radiation/wind pressure like a balloon.
The bubble would have a surface gravity depending on its radius and it's mass (bubble+star+anything in between), like for a planet. Meaning that you could easily (theoretically) have a Dyson bubble of any surface gravity you want, including 1g.

Though in a universe with 3km planets, death star-like battlestations and giant bipedal war robots, I'd expect technomagic to allow you to create any kind of Dyson sphere you want, including one that has technomagical gravity pointing outward, or even outward inside and inward outside.
Depending on the size of it, it could make for an interesting huge map.