Edgard Neuman

uh.. no.. you would need the sphere to be hermetic for the gas inside to build up. Free solar wind or radiation pressure alone would never be able to counteract the mass of the sphere. We established that solar wind pressure is thousands of time too weak. Here I suppose the gas inside the sphere exert pressure of several Pascals : the density of the gas inside is nothing close to density around a free star. The sphere would be filled with hydrogen / helium (i suppose). We can't tell the density since it depends of the temperature of the gas. It can't be made of several parts or the gas would escape. So no, it's not what they call a "Dyson bubble".. (why do they call it a bubble if it isn't hermetical ?) The article doesn't seem to take into account that if you put the star inside a container, the space should start to fill up with atoms and gas. Do you agree that if you put the star inside a hermetical container, the pressure would build up ? Since we can (i suppose) build up the pressure this way, then a more massive sphere (not thin graphene, but any metal structure, thus more resistant to tensions) seems possible to maintains. The pressure inside have to be much greater than outside, greater that the normal distribution of gas around a free star. We can even control the pressure inside (by venting the gas accordingly), so we can control the amount of tension. We would aim to exactly compensate gravity with gas pressure. I totally understand how impossible it would be to build, my question is more about the stability of the thing once pressurized. I think it would be more complicated because of heat from the star.. I don't think the density of matter around a free star obey the pgh formula, because the star is emitting energy. It's not like a planet atmosphere. Honestly I think the only way to answer is to use simulations. And since the pressure at 1 AU (for my example, I put the sphere at 1 AU but i have no ideas how big the sphere should be to optimize it).. is 6 Pa, that imply the volume of gas inside the sphere is enormous and so the mass of the whole system depends on the density of gas ; the mass of "atmosphere" of the star isn't negligible relative to the mass of the star itself.

A gradient of pressure should be inside the sphere for the reasons I gave. I know, but i don't know how.. the result should be a combination of gas diffusion, gravity and solar wind.. The mass of the sphere of course. Since I suppose the sphere is 1 ton / m² (the interior surface of the sphere), The pressure inside needs to prevent the sphere to simply break and fall to the sun (the sphere doesn't need to be a rigid object). I though about it, I suppose it's a more general question : what would happen if we could put a planet atmosphere (like Jupiter) into a giant balloon...Could the balloon be in a stable state ? Will the balloon fall ? For the balloon to fall, the atmosphere would need to change shape and not be spherical anymore, for the balloon to bend. I think it would be stable. For instance, some planets have a layer of liquid water : what prevent the inner core to move inside the water then ? You could say that the upper layer floats.. but then, in my case since the pressure inside the balloon should equal gravity of the material, it should be "as if" the sphere floats on the gas.

Ok you both seems to not understand my question. Please read carefully. This is not a ordinary Dyson Sphere : no, it's not a structure orbiting the star. In that case, the sphere isn't even rotating (since rotation would break symmetry and create tension in the sphere). The star and the sphere would be perfectly symmetrical : nothing rotates. We don't use centrifugal force in any way here. In that case, we want the pressure of the gas, coming from the star to build up, until it's enough to thwart the gravity of the sphere, keeping it from falling or breaking. The sphere needs to be closed (that's the reason I put the word "Closed" right in the title. If it's not closed, the pressure wont build up, and in that case, of course it wouldn't work.. I understand what Dyson spheres are thank you.. and please don't quote this writing "no you don't" .. that would be very idiotic. The fact that people come here not to really think but to spew cheap rhetoric is really annoying. ). It means inside the sphere, there's a high pressure of hot gas. There is a gradient of pressure inside the sphere, for 2 reason : - gravity (by itself, the gas wouldn't distribute equally since the star gravity is strong at the center). It would be some sort of dense hot gas atmosphere around the star. - The continuous emission of gas from the star : there would still be a radial movement of matter. The sphere would need to vent some of the gas outside, because we want just the right pressure, so we want the gas to build up until the right pressure and then maintain this pressure. And since it's still a radial movement of matter, the surface that each sphere of gas progressing from the center to the the outer is proportional to R², and the pressure proportional to 1/R² . So yes, definitively a gradient of pressure (just like there is for the solar wind, and everything that goes away from a sphere : gravity is 1 /D² .. every wave.. ). Since there is a gradient of pressure, yes there is stabilization : if you move the sphere (let's say a length of x) , the pressure at the closest side would be 1/(R-x)² and the other side 1/(R+x)². You can check that in every case (for d << R) : 1/(R-x)² > 1/(R+x)² So yes, if the star isn't at the center, there is a force appearing to correct that. And yes I understand that gravity would work in the opposite way. So both forces would have to be precisely adjusted. Now I understand, given the size of the thing, the real problem is how the forces would propagate through the sphere, and yes the sphere would have to support very large tensions (not necessarily be solid, but only tangential tensions to hold together enough)

For the number, I used the simple formula that I explained.. can you read all my messages ? (I compute gravity force (Newtonian) for 1m² of sphere where I assume 1 ton by m²), and then the pressure necessary for this force is trivial (since it's for 1m²) The sun is inside the sphere.. it's not like a balloon movement, since the force from the sun come from inside.. Now I see that as always on this forum, you don't really think and don't bring me thoughtful answers. Bye.

I totally understand that the solar wind is 1–6 nPa ((1–6)×10−9 N/m2) at 1 AU For a 1 UA sphere, the pressure necessary to support 1 ton / m² is 5.9641110164 Pa (since the solar wind pressure is also proportional to 1/D², the factor is always the same) BUT : if we prevent the solar wind from escaping, the pressure should increase rapidly inside the sphere. All we have to do is to put vents that only open when the pressure gets dangerously high (here that would be >6 Pa at 1 AU).. It's a "closed" sphere : the wind can't escape : it's a balloon, a sort of pressure cooker. The sphere would be filled with gas from the star at least at the necessary pressure (it would be incredibly difficult to construct before the pressure gets high enough) And the pressure gets greater when the surface get closer to the star : the correction is totally happening. Also I suppose the scale would make it extremely hard to manage the constraints provoked by any variation of the pressure around the sphere, and solar storm would break everything.. it would need a very calm star, with highly symmetrical wind and pressure.

https://medium.com/our-space/dyson-spheres-450146a7c13b Thanks.. read this : no mention of pressure inside the Dyson sphere and its ability to thwart gravity.. so that don't answer my question.. I did google Dyson, and nowhere did I found any mention of pressure inside.. everybody assume the sphere is structurally stabilized by centrifugal force, like it's a structure in orbit. Here I ask about inner gas pressure actively supporting the sphere.. that's totally different. You can read that : https://en.wikipedia.org/wiki/Dyson_sphere#Feasibility They talk about the gravity of the sphere, but they don't talk about the pressure generated by solar wind and inner gas pressure. Think about it. Suppose the totally closed sphere weight 1 ton by m² of surface (inside the sphere)... 1 ton by m² is already a heavy structure. The sun gravity for 1 ton, is relatively low if the sphere is big enough.. we can then compute the gas pressure inside the sphere necessary. Let's assume Sun mass = 2×10^30 kg Sphere ray = 57909050000 m (the orbit of mercury) Gravity force for 1 m² = 1 ton of sphere = G * Sun mass * 1 ton / r² I get a force of 39,8 Newton So 39,8 Pascal for 1 m² of sphere And the bigger the sphere, the lower the pressure It seems to me totally achievable if the sphere is filled with the gas from the star, no ? I totally understand that the solar wind is 1–6 nPa ((1–6)×10−9 N/m2) at 1 AU For a 1 UA sphere, the pressure necessary to support 1 ton / m² is 5.9641110164 Pa (since the solar wind pressure is also proportionnal to 1/D², the factor is always the same) BUT : if we prevent the solar wind from escaping, the pressure should increase rapidly I wouldn't be a "solid" sphere, but rather a space balloon, filled by the pressure of the star

Hi, Here is my question, until now, I thought "of course, it's impossible". The matter will never be hard enough to resist, and the whole thing is in meta stable equilibrium anyway : any deviation would pull the closest sides of the sphere and break the whole thing. ("That's dumb !.") Until I thought about this : what about solar wind and matter production from the star...? It seems to me now, that if you really close the star into a solid sphere, it will still produce a powerful solar wind, and temperature and pressure that would fill the solid sphere, until it increase enough to push the sphere away. So here is my question : is a "self pressured" Dyson sphere, where solar wind and matter pushes in every direction the sphere (and thwart gravity) totally impossible ? (it would then "only" require "pressure control", by venting enough Gaz to stabilize the sphere) (I know the true answer would probably require serious modeling : has it been done ?)