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I've heard several schools of thought. From a hard science standpoint, could there be gravity on the habitable surface of a Dyson Swarm plate?

I keep thinking no. But if the outer shell were to be spun, could you generate a kind of artificial gravity?

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    $\begingroup$ Welcome to Worldbuilding! Would you be so kind as to share some of your reasoning for your 'no'? Also, as this is about worldbuilding, share some of the parameters of the Swarm you are envisioning. Size of the fragments, distance to the sun, nature of the fragments (mirrors, collectors, habitats, ...) might all pertain to the answer, so to avoid unneccesarily broad answers, try to give your question more focus. $\endgroup$ – bukwyrm Apr 21 '18 at 21:33
  • $\begingroup$ No, and yes, in this order. And the artificial gravity would be perpendicular to the rotation axis, so you'd be better off with a Dyson Ring. $\endgroup$ – LSerni Apr 21 '18 at 21:55
  • $\begingroup$ OK, so yes on the centrifugal approach. My main reason for 'no' would be a lack of mass for the plates meant to be habitable. And since any kind of artificial gravity other than using mass or some kind of motion are more cinematic scifi than hard science, I figured 'no' is not only the safest answer, but also the most accurate $\endgroup$ – Richard Apr 21 '18 at 22:28
  • $\begingroup$ As far as specifics for my swarm and the world. Currently I'm kicking around an idea for a setting that involves several races that populate several plates around a star in a dyson swarm. Most of the plates are meant for energy collection and distribution but many others are devoted to providing habitat for said races. The entire swarm is mean to be a kind of terrarium for less evolved species, to be studied by a higher form of life. In essence. The story I have in mind is about the destabilization of the swarm itself, as it is struck by a rogue celestial body, a large comet $\endgroup$ – Richard Apr 21 '18 at 22:31
  • $\begingroup$ I envision several smaller swarms and clusters of plates that are positioned at intervals within the habitable zone to create hotter and colder climates, that house a variety of species that are presumed to have evolved from these climates. Then there are two central rings, which are mainly for collection and distribution of solar energies. One very close to the parent star, which is not really visible, and another, large belt, on the outside,visible by may of the races on the habitable plates. $\endgroup$ – Richard Apr 21 '18 at 22:33
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A typical Dyson Swarm would have flat plates pointed at the Sun to maximize the surface area for the collection of solar energy (which is the point of having a Dyson Swarm in the first place). If you want to collect thermal energy, the mirrors would be parabolic with the focus facing the Sun in order to maximize the amount of thermal energy being gathered.

In either case, these devices could be spun in order to stabilize them and ensure they maintain proper orientation, providing centrifugal "gravity" around the edges.

The issue is solar energy collectors should be lightweight in order to make production, manoeuvring and so on quick and easy, and they should be specialized to generate the maximum amount of solar energy, so building them with a habitat attached seems a bit of a kludge.

The amount of area inside a Dyson Swarm would be so vast that purpose built rotating habitats ranging from "Island 3's" to "Bishop Cylinders" could easily be orbiting inside the swarm with thousands or hundreds of thousands of kilometers spacing between objects.

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Island 3

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Bishop cylinder

To put this in context, an Island 3 is 8km in diameter and 30 km long, with an interior area of roughly 500 square miles, while a Bishop Ring is 500km wide and has a radius of 1000km, has an interior area of 3 million square kilometres. Each type of structure can house hundreds of thousands to millions of people (much of the population density can be decided by how the internal society wants to structure itself, a Bishop ring has the surface area of a small continent and could house billions of people, if desired).

Since a Dyson swarm with a 1 AU diameter has an area of 2.8×10E17 km2, there is room for millions of habitats, along with billions of solar collectors and other devices, so people and their industrial machinery can be separated by a comfortable distance.

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  • $\begingroup$ Not building solar collectors to be connected to the habitats, they'll be separate just for that ergonomic reason and the energy will be transferred wirelessly. $\endgroup$ – Richard Apr 21 '18 at 23:27
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Since a Dyson swarm (Dyson's concept of a Dyson Sphere) is really a bunch of individual satellites, you can make them spinning cylinders if you wish.

The object of the swarm is to intercept all or most of the light from the central star. This would require many layers of satellites in different orbits. I could even picture satellites that use panels that collect the waste IR of the more inner orbits.

A solid dyson sphere or ringworld is highly unstable and will eventually intercept the star. This is because the star's gravity effects each side of the object the same, so there is no net gravity to hold it in place. This is why Larry Niven's sequel to Ringworld added rockets to keep it in a stable orbit.

I used a dyson swarm for a game once, and I used plenty of "magic" to make it an interesting setting for a game, such as hyperspatial tunnels between the satellites and robots who (unseen, underground) kept the ecology going.

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  • $\begingroup$ Dyson spheres are stable, ringworlds are not. I quote: "The difference is that gravity is a 1/r2 force, while the surface area at distance r of a 2-dimensional object inside a certain solid angle goes as r2. The fact that these exactly cancel is what balances the gravitational forces from a sphere so that they all cancel out in the interior. However, this balance doesn't happen with a ring, so the nearer parts of the ring provide more of a pull than the more distant parts, resulting in a net force towards the closest point." See fora.xkcd.com/viewtopic.php?t=62641 $\endgroup$ – a4android Apr 22 '18 at 8:57
  • $\begingroup$ I thought adding rocket engines to Ringworld was silly. Niven could have used gravity polarizers which were already part of Known Space. Sounds like you had fun with your dyson swarm game setting. $\endgroup$ – a4android Apr 22 '18 at 8:59
  • $\begingroup$ @a4android, the physics works the same for a ringworld and a dyson sphere. Basically, for both the gravitational force of the sun cancels out. Imagine a double-sided thin cone (perhaps 0.01 degrees) centered on the sun. If the object is exactly centered, then the gravitational forces experienced from both cones are identical and they cancel out. If one of the sides of the object is closer, then the gravitational force experienced by the closer side is larger, but the area is smaller. The side further away experience less force on a greater area. $\endgroup$ – NomadMaker Apr 22 '18 at 10:24
  • $\begingroup$ Because the gravitational force goes down at 1/r2 and the area goes up at r2, the combined force from the inner star cancels itself out. A dyson swarm, however, is a bunch of things in orbit and doesn't experience this problem. $\endgroup$ – NomadMaker Apr 22 '18 at 10:25
  • $\begingroup$ Yes I do know a dyson swarm isn't affected with the ringworld instability problem. It is the realistic, at least, plausible option. $\endgroup$ – a4android Apr 22 '18 at 10:31
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If you use an orbiting formation of "pie plates" per the intermediate step in constructing a ringworld laid out in Larry Niven's Bigger Than Worlds essay then yes you can have "gravity". In fact you have to have pseudo-gravity on such a structure due to linear acceleration towards the star to maintain a stable orbit. The amount of gravity you would experience in such a system depends on the orbital velocity and range of the plate involved as that will dictate the inward counter-acceleration needed to maintain a stable orbit.

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