4 ms·

Maybe this is a stupid question, but is there actually enough raw material in the solar system to cover the surface of our star and build the necessary machiner

by bbarn 5y ago

Maybe this is a stupid question, but is there actually enough raw material in the solar system to cover the surface of our star and build the necessary machinery to keep it in place, collect its energy, etc.?

kragen 5y ago
You don't put it on the surface of the star; you orbit at a distance far enough away to maintain a reasonable temperature. Current solar panels are about 300 grams per square meter, but there are much opaquer materials than silicon, so you can probably get down to a hundredth of that. A sphere at the radius of Earth's orbit would be 2.8e23 square meters and thus at 300 grams per square meter 8.4e22 kg. Earth's moon masses 7.3e22 kg, while Jupiter masses 1.90e27 kg. So there's at least five orders of magnitude more raw material than you need. If you happened to live in a planetary system without adequate gas giants, you could probably find some way to scoop mass off the surface of your star or capture it from coronal mass ejections, then use fusion to transmute it into the materials you need. Even Sun is 1.90e30 kg, and it's rather small as stars go.
- Smaug123 5y ago
  I'm sure you already know this, but GP probably doesn't: I love https://en.wikipedia.org/wiki/Star_lifting https://en.wikipedia.org/wiki/Star_lifting for very many reasons. 1. "Stellar husbandry". That phrase alone is worth the price of admission. 2. The idea of doing mass spectrometry on a jet of matter coming out of a star to separate it out into streams of hydrogen, deuterium, helium, etc. 3. The idea of creating artificial gas giants as a storage mechanism. (The list goes on, but 3 is a magic number.)
  - kragen 5y ago
    I didn't! Thanks!
dmead 5y ago
Probably not. I was under the assumption we could build a Dyson swarm however.
digitalronin 5y ago
There's plenty. The vast majority of the 'shell' would be solar concentrators - basically aluminium foil or something like it. You can make a LOT of that by dismantling a few asteroids, never mind a planet or two. Isaac Arthur's youtube channel goes into this in some depth (and is generally excellent, IMO). Here's an episode on Dyson Spheres: https://www.youtube.com/watch?v=HlmKejRSVd8 https://www.youtube.com/watch?v=HlmKejRSVd8
TaylorAlexander 5y ago
It's probably very difficult structurally to build an actual sphere, since the poles would not have any orbital velocity and the whole sphere would want to flatten. Unless there is a way to do some kind of anti-gravity that humans just haven't discovered (which is a possibility that seems plausible). But there is also the Dyson swarm, which is like a starlink constellation orbiting a star and designed to collect as much energy as possible. Anyway I don't know the answer to your question, but if we ignore structural problems with a sphere we could imagine a material a few atoms thick, like a giant carbon nanotube structure. Then one wonders how much material there is in Jupiter as an approximation of total matter in the solar system. I will leave the calculation as an exercise to the reader. ;)
- Blammar 5y ago
  I believe Dyson spheres don't rotate, so they just have to be able to handle the stress of the central sun pulling uniformly on the surface. Per the Ringworld not being stable, I think the same math applies to the sphere as well as the Ring, so the sphere will need attitude jets to maintain position with respect to the central sun. Dyson swarms seem drastically easier to construct. We could build one example of that habitat fairly soon!
  - TaylorAlexander 5y ago
    Ahh a non-rotating sphere makes sense! If it is light enough then solar pressure could help keep it up too, and it could have openings to adjust pressure which would serve as attitude jets. Hmmm this does seem possible after all, thanks for the tips!
buryat 5y ago
2pir^2 vs 4/3pir^3 plenty of material to capture the surface + you don't need a sphere, a ring/few rings would be enough

by bbarn 5y ago

kragen 5y ago

You don't put it on the surface of the star; you orbit at a distance far enough away to maintain a reasonable temperature. Current solar panels are about 300 grams per square meter, but there are much opaquer materials than silicon, so you can probably get down to a hundredth of that. A sphere at the radius of Earth's orbit would be 2.8e23 square meters and thus at 300 grams per square meter 8.4e22 kg. Earth's moon masses 7.3e22 kg, while Jupiter masses 1.90e27 kg. So there's at least five orders of magnitude more raw material than you need. If you happened to live in a planetary system without adequate gas giants, you could probably find some way to scoop mass off the surface of your star or capture it from coronal mass ejections, then use fusion to transmute it into the materials you need. Even Sun is 1.90e30 kg, and it's rather small as stars go.

Smaug123 5y ago
I'm sure you already know this, but GP probably doesn't: I love https://en.wikipedia.org/wiki/Star_lifting https://en.wikipedia.org/wiki/Star_lifting for very many reasons. 1. "Stellar husbandry". That phrase alone is worth the price of admission. 2. The idea of doing mass spectrometry on a jet of matter coming out of a star to separate it out into streams of hydrogen, deuterium, helium, etc. 3. The idea of creating artificial gas giants as a storage mechanism. (The list goes on, but 3 is a magic number.)
- kragen 5y ago
  I didn't! Thanks!

dmead 5y ago

Probably not. I was under the assumption we could build a Dyson swarm however.

digitalronin 5y ago

There's plenty. The vast majority of the 'shell' would be solar concentrators - basically aluminium foil or something like it. You can make a LOT of that by dismantling a few asteroids, never mind a planet or two. Isaac Arthur's youtube channel goes into this in some depth (and is generally excellent, IMO). Here's an episode on Dyson Spheres: https://www.youtube.com/watch?v=HlmKejRSVd8 https://www.youtube.com/watch?v=HlmKejRSVd8

TaylorAlexander 5y ago

It's probably very difficult structurally to build an actual sphere, since the poles would not have any orbital velocity and the whole sphere would want to flatten. Unless there is a way to do some kind of anti-gravity that humans just haven't discovered (which is a possibility that seems plausible). But there is also the Dyson swarm, which is like a starlink constellation orbiting a star and designed to collect as much energy as possible. Anyway I don't know the answer to your question, but if we ignore structural problems with a sphere we could imagine a material a few atoms thick, like a giant carbon nanotube structure. Then one wonders how much material there is in Jupiter as an approximation of total matter in the solar system. I will leave the calculation as an exercise to the reader. ;)

Blammar 5y ago
I believe Dyson spheres don't rotate, so they just have to be able to handle the stress of the central sun pulling uniformly on the surface. Per the Ringworld not being stable, I think the same math applies to the sphere as well as the Ring, so the sphere will need attitude jets to maintain position with respect to the central sun. Dyson swarms seem drastically easier to construct. We could build one example of that habitat fairly soon!
- TaylorAlexander 5y ago
  Ahh a non-rotating sphere makes sense! If it is light enough then solar pressure could help keep it up too, and it could have openings to adjust pressure which would serve as attitude jets. Hmmm this does seem possible after all, thanks for the tips!

buryat 5y ago

2pir^2 vs 4/3pir^3 plenty of material to capture the surface + you don't need a sphere, a ring/few rings would be enough