Dyson Sphere - The Ultimate in Navel Gazing?
- Thread starter noknowes
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Firstly I'd point out that a solid shell as seen on TNG is not the most likely arrangement for such a thing. A ring or network of tethered panels or satellites is more likely.
Secondly, any civilization capable of building a Dyson sphere harnesses the energy of entire star systems and consumes and breaks down entire planets in order to do their work. Pretty arrogant to assume we'd have much comprehension of how a Type II+ civilization would run it's economic affairs.
A one metre thick Dyson shell would require a 1000 star systems to be moved and crushed and processed.More energy would be expended then gained.
Well, we could build it around a cooler star than the sun, making it much smaller.
But a ring is more practical.
Surface area of a sphere the size of the Earth's orbit is:
4*pi*r^2=2.8x10^23 square meters. Make it a meter thick and you get 2.8x10^23 cubic meters. Assume a density of 5 or so and you get 1.4x10^24kg.
Jupiter masses 1.8986 × 10^27 kg
Am I missing something here?
A Dyson shell would be pretty useless as it wouldn't have any net gravitational attraction for any objects placed on its inside surface (Gauss' law) -- they would fall straight into the central star. For the same reason, any perturbation to the central star would result in it colliding with the shell unless a correction method was used to move the shell (Niven's Ringworld jets) or the star. Rotating the shell to create artificial gravity would require an immensely strong shell material (Niven's Scrith) and the nett force would fall to zero at the poles (hence Niven's choice of a ring).
Smaller constructed ringworlds (orbitals in Iain M Banks' Culture novels), which orbit the star in a more conventional fasion, would be a more probable step to take for an advanced civilisation. Personally, I think that uploading consciousness into a physical virtual reality matrix surrounding a black hole or neutron star used as a power source is even more likely.
Smaller constructed ringworlds (orbitals in Iain M Banks' Culture novels), which orbit the star in a more conventional fasion, would be a more probable step to take for an advanced civilisation. Personally, I think that uploading consciousness into a physical virtual reality matrix surrounding a black hole or neutron star used as a power source is even more likely.
Did you plan to build it out of hydrogen?
ETA: Though, at that point in technological development, we'd probably be able to fuse it down to iron.
I think Neopeius needed to multiply by 5000 kg/m^3 -- that would give a mass of 1.4x10^27kg or just under one Jupiter mass.
What if you had a series of contiguous rings, each one say half a million miles thick, coupled together to form an overall sphere but allowed to rotate at different rates? That way you could spin the thing for gravity, you don't need a super-strong exotic material, and you have a lot more available surface area than a single Ringworld.
The poles would be left unoccupied-- maybe they could be completely open, to let the solar wind escape. To keep the atmosphere from being driven out at the poles, the inside is stairstepped. Perhaps each ring protrudes into the interior by a few thousand miles. Centrifugal force keeps the atmosphere from escaping past the "wall" formed by the next ring outward, so the air remains on that particular ring-level. That does mean that each ring would have its own weather, ecosystem, and, probably, atmosphere. Hmm, that could be an advantage. Each ring could be used to support different forms of life.
Aside from perturbations to the central star, do you see any problems with this?
As your solution effectively consists of a large number of stacked rings of different sizes, you'd still need an incredibly strong substrate for most of them. Dyson didn't originally envisage a single monolithic construct like rings or a shell, but a vast swarm of bodies orbiting the star so that almost all of its power output would be captured. From the outside it would look like a 1AU-diameter object glowing in the IR with an effective black-body temperature aound 273K. I know that Dyson originally proposed searching for such objects, and that Fermilab did an analysis of IRAS data to this end. The next generation of IR satellites should provide much better data for a search.
I'm embarrassed, but I did put the 5 factor in there already so it's 1000kg/m^3
So a Jupiter can make six Dyson Spheres. It doesn't take thousands of star systems as previously asserted.
1000kg/m^3 is roughly the density of water but I guess that'll do.
You'd probably also need a hell of a lot reaction mass to spin the shell up to 1000km/s or so at the equator (using the Niven Ringworld size estimates).
True, but it seems like it wouldn't have to be as strong as the substrate for a single, solid sphere.
Oh, I know. I'm just buying into the kewl-factor of a Dyson shell.
I had my own thread on here a few years ago, on the same subject. I was polling ideas for the most plausible design for a Dyson shell, for a role-playing game I was designing. I've been avidly following all the latest threads too.
If you captured all or most of the power output of the star you would be burned to a cinder inside the Dyson sphere due to heat build up.The whole thing is very poorly thought out by the originator.
Right. I'm saying earlier in my calculations, I multiplied everything by 5 to get roughly Terran densities.
Why do you need to spin it?
kitsune
Captain
We don't know what percentage of the shell has an atmosphere, or how thick that atmosphere would be. But regardless, you'd need an awful lot of oxygen and nitrogen...
Assuming that you want people to live on it, instead of dying horribly as they are sucked towards the sun along with the entire atmosphere, soil, water, and everything else, simulated gravity.
The outside of a spherical structure has gravity equivalent to the mass of the sphere. The inside of a hollow sphere has no natural gravity, no matter how massive it is. Everything naturally cancels out on the inside. In order to overcome this, gravity must be simulated via spin. This isn't real gravity, but it is close enough in effect.
I'm pretty sure that the original idea wasn't to live in it, but to create a network of solar power collectors that could be used to send energy that would otherwise be lost out to the inhabited facilities and planets in the rest of the system.
Living on one is stupid, for many reasons. A sphere and a ring are both unstable, and would collide with the sun, eventually, without huge thrusters that require a huge reaction mass. It also requires a material far stronger than any that actually exists. Instead, you build a mesh network of photovoltaic or solarthermal power satellites. The mesh, being a mesh, has giant holes in it. These gaps are placed so that life-sustaining planets get their regular amount of sunlight, the satellites just collect the light that would be lost to the void of space. They then convert this into a tightly focused wireless power transmission beam, most likely microwave but possibly laser, and send it to a collection station, which then sends it to facilities in the rest of the system.
Hell, using laser transmission means that you don't even need to convert the light into electricity first, you just need to equip the collection satellites with mirrors and lenses that can focus and redirect it.
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That wouldn't happen -- the Dyson sphere would reradiate the energy in a manner akin to a black body -- basic laws of thermodynamics and all that.
If you put a 100 watt incandescent bulb in a shoe box the temperature inside the shoe box will go quite high.The shoe box will of course radiate heat eventually, but the temperature will go very high inside the show box killing any insects inside.
