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i_should_be_coding t1_jdx2h8x wrote

Reply to comment by starcraftre in Would building a Dyson sphere be worth it: We ran the numbers. by filosoful

See, now I'm wondering if there's actually enough material to build something like this.

The combined mass of the asteroid belt is about 2*(10^(21)) kg. Let's say R is the radius of the sphere, and it's 1000m thick. The radius is much larger than the thickness, so we can estimate the volume at 1000*4*pi*R^(2). As for the density, Aluminum is about 2700 kg/m^(3), and Iron/Steel is about 8000 kg/m^(3), so let's just say 5000 for the argument's sake.

So the we have R = sqrt(2*10^(21) / 5000*4000*pi) ~ 5.6*10^(6) m according to WolframAlpha. That's the radius of the sphere we would be able to build with all of the asteroid belt combined.

For scale, the orbit of Mercury is 43,000,000 km in its closest point to the sun, and our sphere's radius is about 60,000 km.

So unless I got the math really wrong, I'd say constructing any sort of Dyson sphere that's solid, has 100% coverage, and is large enough that the Earth still has sunlight, would probably mean we would have to disassemble planets, and even that might not be enough, as the mass we need would increase proportionately to R^(2), and a lot of the mass in the solar system isn't useful.

For now, let's focus on fixing some potholes or something.

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starcraftre t1_jdx6l14 wrote

Assuming a 1 AU sphere for the original design spec, and assuming you want statites, then your target areal mass is around 1.6 g/m^2 .

Taking my 10% coverage estimate, the factored surface area of a 1 AU sphere is 2.81e22 m^2 or 4.5e19 kg of material. 2% of the Belt, assuming every rock is made of aluminum.

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[deleted] t1_jdx99pn wrote

[deleted]

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i_should_be_coding t1_jdxb7c9 wrote

I liked the Kurzgesagt video on it. Was fairly interesting, and I love their "Let's just assume these magic technologies exist" attitude.

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ItsAConspiracy t1_je0k4ci wrote

Right, the article compares the energy cost of disassembling planets to the energy that could be collected by the Dyson sphere you could build from the materials.

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