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A Dyson sphere around a black hole

(arxiv.org)
214 points SkyMarshal | 1 comments | 19 Aug 21 03:40 UTC | HN request time: 0.218s | source
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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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mytailorisrich ◴[19 Aug 21 09:29 UTC] No.28231889[source]▶
I don't think that how efficient the production is really matters because stars do produce that energy anyway and for free as far as we are concerned. The question is one of efficiency and cost of collecting it.
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arrow7000 ◴[19 Aug 21 12:39 UTC] No.28233058[source]▶
I'm surprised not more replies say this.

So what if it's inefficient? It's happening anyway and it's not like you can siphon the hydrogen off and do anything else with it.

What kind of purism is it to not tap the largest energy sources in existence because you bristle at their inefficiency.

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1. jjk166 ◴[19 Aug 21 19:34 UTC] No.28238293[source]▶
> It's happening anyway and it's not like you can siphon the hydrogen off and do anything else with it.

Actually this is another megastructure process known as Star Lifting. And it's not just hydrogen you can siphon off - the sun, by virtue of its immense size, contains the overwhelming majority of every element in the solar system.

Unfortunately because they burn up so quickly, the hydrogen isotopes we would use in fusion reactors are actually incredibly rare in the sun. The sun is estimated to have about the same amount of deuterium as Earth's oceans. On the other hand, Helium-3, another potential fusion fuel, is very abundant - about 10-20 Earth Masses are present. Still though, burning all this helium 3 at the same energy production rate of the Sun would only last us 870,000 years - a drop in the bucket compared to the lifetime of the sun.