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A Dyson sphere around a black hole

(arxiv.org)
214 points SkyMarshal | 4 comments | 19 Aug 21 03:40 UTC | HN request time: 0.801s | 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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DocTomoe ◴[19 Aug 21 09:38 UTC] No.28231938[source]▶
Why does man use hydro-power even though it is a rather silly idea if he has the technological prowess to generate a lot more power basically at will, basically anywhere, with a lot less resources destroyed, thanks to nuclear energy?

Well, hydro energy is just there, requires comparatively little ongoing maintenance, and has less catastrophic failure modes.

I think the same caveats work for Dyson spheres.

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1. stephanheijl ◴[19 Aug 21 11:55 UTC] No.28232713[source]▶
> has less catastrophic failure modes

Given incidence of dam bursts like the 1975 Banqiao dam failure[1], with an estimate death toll of 26,000 to 240,000 people and flooding of over 12,000 square kilometers, I'm inclined to disagree with this assessment.

[1]https://en.wikipedia.org/wiki/1975_Banqiao_Dam_failure

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2. goohle ◴[19 Aug 21 12:10 UTC] No.28232790[source]▶
Can you compare number of deaths because of dam failure with number of deaths because of flood and no dam to protect from flood? I.e. should we stop to build dams for flood protection because of telegraph failure at Banqiao dam?
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3. heavenlyblue ◴[19 Aug 21 12:53 UTC] No.28233209[source]▶
"We should not do tooth fillings because tooth fillings fail and then you're in pain"
4. stephanheijl ◴[19 Aug 21 15:27 UTC] No.28235080[source]▶
I am not claiming we should not have dams, or refrain from using dams to provide hydroelectricity. My point of contention is the assertion that hydro energy has less catastrophic failure modes than nuclear (presumably fission). Clearly the failure modes for hydro dams are at least on par with those of nuclear installations, given that we have historic evidence that they can inflict tens of thousands of casualties.

Hypothetical scenarios can be constructed for both methods of power generation (What if Braidwood plant melts down, somehow killing the 5 million people living within a 50 mile radius? What if the Three Gorges Dam busts, inundating an area inhabited by 600 million people?[1]) Either way, it is far from obvious to me that hydro has the superior safety profile, especially when their fatality rates are on the same order of magnitude even when the Banqiao incident is removed[2]*.

[1] https://web.archive.org/web/20210620174812/https://www.japan... p/opinion/2020/09/01/commentary/world-commentary/big-china-disaster/

[2] https://ourworldindata.org/safest-sources-of-energy

* Sovacool et al. (2016), the source of the data in [2] includes a hydro fatality rate per tWh 2.4x larger than nuclear when Banqiao is included.