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A Dyson sphere around a black hole

(arxiv.org)
214 points SkyMarshal | 7 comments | 19 Aug 21 03:40 UTC | HN request time: 0.232s | source | bottom
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ardit33 ◴[19 Aug 21 08:55 UTC] No.28231727[source]▶
The whole concept of a Dyson sphere is kinda idiotic. Any civilization that is capable to build one, it is probably able to work out fusion energy very efficiently.

There is no point to go and harness energy around a star or a black hole, when you can just produce it locally with a lot less resources/waste and materials. The sun itself is actually very inefficient in producing energy.

There is no need to harness the sun million of km away, when you can recreate it in your home planet. The only way to produce a dyson like of sphere, is to tame an over-heated sun, and reflect away un-needed energy. But there is no point to build one to just harness it.

It makes great sci-fi stories, but that's about it. Scientifically, it just doesn't make sense.

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hutzlibu ◴[19 Aug 21 08:59 UTC] No.28231746[source]▶
It depends on the amount of energy the civilisation needs.

Lets say, you want to manufacture new planets/planetary sized spaceships. You would need very big fusion reactors and you probably want to save the special fusion fuel for those, when they are on their voyage to other worlds. Because then they need fusion.

But why build a fusion reactor, when you already have a big one avaiable?

replies(1): >>28231802 #
1. mclightning ◴[19 Aug 21 09:10 UTC] No.28231802[source]▶
Because you can build a more efficient one? You could make it portable, controlled, modular etc etc
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2. hutzlibu ◴[19 Aug 21 09:31 UTC] No.28231897[source]▶
Yeah. All needed for interstellar travel for example. But for manufacturing planets?
replies(1): >>28231903 #
3. mclightning ◴[19 Aug 21 09:33 UTC] No.28231903[source]▶
Why would you want to manufacture a gravity well? There are plenty of them
replies(1): >>28231911 #
4. hutzlibu ◴[19 Aug 21 09:34 UTC] No.28231911{3}[source]▶
How many earth sized planets do we have in our solar system?
replies(1): >>28231941 #
5. mclightning ◴[19 Aug 21 09:39 UTC] No.28231941{4}[source]▶
If you're limited by the compounds available within the solar system, you should forget about building a dyson sphere for other reasons, or building a planet, or any kind of activity that will disturb the orbits of planets.

Few planets are similarly sized as Earth already btw, although with varying densities.

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6. hutzlibu ◴[19 Aug 21 09:45 UTC] No.28231972{5}[source]▶
Ok, earth sized is mainly about 1 g. So yes, also with earths density to be precice. That leaves only venus as a existing alternative.

And I just assume that a civilisation advanced enough to build a dyson sphere, can handle the non trivial orbital mechanics, too. But maybe still cannot travel FTL. So indeed rather choose to build planets, or planet sized space stations.

That would require lots of energy and maybe the need to harvest the sun directly and control the light going out towards the planets.

7. ◴[19 Aug 21 09:49 UTC] No.28232009[source]▶