Could a Black Hole Surrounded by Energy-Harvesters Really Power a Civilization? (sciencemag.org) 77
"In the long-running TV show Doctor Who, aliens known as time lords derived their power from the captured heart of a black hole, which provided energy for their planet and time travel technology," writes Science magazine.
"The idea has merit, according to a new study."
Slashdot reader sciencehabit quotes their report: Researchers have shown that highly advanced alien civilizations could theoretically build megastructures called Dyson spheres around black holes to harness their energy, which can be 100,000 times that of our Sun. The work could even give us a way to detect the existence of these extraterrestrial societies...
Black holes are typically thought of as consumers rather than producers of energy. Yet their huge gravitational fields can generate power through several theoretical processes. These include the radiation emitted from the accumulation of gas around the hole, the spinning "accretion" disk of matter slowly falling toward the event horizon, the relativistic jets of matter and energy that shoot out along the hole's axis of rotation, and Hawking radiation—a theoretical way that black holes can lose mass, releasing energy in the process.
From their calculations, researchers concluded that the accretion disk, surrounding gas, and jets of black holes can all serve as viable energy sources. In fact, the energy from the accretion disk alone of a stellar black hole of 20 solar masses could provide the same amount of power as Dyson spheres around 100,000 stars, the team will report next month in the Monthly Notices of the Royal Astronomical Society. Were a supermassive black hole harnessed, the energy it could provide might be 1 million times larger still.
If such technology is at work, there may be a way to spot it. According to the researchers, the waste heat signal from a so-called "hot" Dyson sphere—one somehow capable of surviving temperatures in excess of 3000 kelvin, above the melting point of known metals—around a stellar mass black hole in the Milky Way would be detectible at ultraviolet wavelengths. Such signals might be found in the data from various telescopes, including NASA's Hubble Space Telescope and Galaxy Evolution Explorer.
"The idea has merit, according to a new study."
Slashdot reader sciencehabit quotes their report: Researchers have shown that highly advanced alien civilizations could theoretically build megastructures called Dyson spheres around black holes to harness their energy, which can be 100,000 times that of our Sun. The work could even give us a way to detect the existence of these extraterrestrial societies...
Black holes are typically thought of as consumers rather than producers of energy. Yet their huge gravitational fields can generate power through several theoretical processes. These include the radiation emitted from the accumulation of gas around the hole, the spinning "accretion" disk of matter slowly falling toward the event horizon, the relativistic jets of matter and energy that shoot out along the hole's axis of rotation, and Hawking radiation—a theoretical way that black holes can lose mass, releasing energy in the process.
From their calculations, researchers concluded that the accretion disk, surrounding gas, and jets of black holes can all serve as viable energy sources. In fact, the energy from the accretion disk alone of a stellar black hole of 20 solar masses could provide the same amount of power as Dyson spheres around 100,000 stars, the team will report next month in the Monthly Notices of the Royal Astronomical Society. Were a supermassive black hole harnessed, the energy it could provide might be 1 million times larger still.
If such technology is at work, there may be a way to spot it. According to the researchers, the waste heat signal from a so-called "hot" Dyson sphere—one somehow capable of surviving temperatures in excess of 3000 kelvin, above the melting point of known metals—around a stellar mass black hole in the Milky Way would be detectible at ultraviolet wavelengths. Such signals might be found in the data from various telescopes, including NASA's Hubble Space Telescope and Galaxy Evolution Explorer.
Well of course it can (Score:1)
Computers got better, so anything's possible. I mean they told the Wright Brothers it would never fly, so there's your proof. Plus it's shown on a TV show.
So there you go, it's obviously easy to do, so the biggest question is will it be AC or DC?
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The Doctor Who reference convinced me. They wouldn't be allowed to include something in Doctor Who if it wasn't 100% realistic.
Re: Well of course it can (Score:2)
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The Doctor Who reference convinced me. They wouldn't be allowed to include something in Doctor Who if it wasn't 100% realistic.
In addition, the Romulans - in Star Trek: The Next Generation - used artificial singularities to power their ships.
I mean - given that TWO classic science fiction shows used this idea, there must be real world merit to it... amirite?
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Funny to discover something when people have been living here for thousands of years. Kinda like a billionaire going very high up but not actually getting to a point where orbit is possible and calling it space.
Be careful of those who write history, they're often full of shit.
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No (Score:1)
No [wikipedia.org].
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Ugh, maybe we can get some cancel culture in here on comments that have nothing to do with the articles they're under.
If You Put a Dyson Sphere Around It (Score:2)
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They do not have the technology of "hatches" or "windows"?
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I think you'll find the correct terminology is "space hatches" and "space windows".
You can choose what goes in (Score:1)
Wouldn't a Dyson Sphere stop stuff from falling into it?
Aha, that's why you pull an Australia and populate the sphere with criminals, the worst of which you throw in the black hole from time to time.
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There are many difficult aspects of a Dyson sphere. It's why Larry Niven and Jerry Pournelle described a "Ringworld", which is physically more feasible to build.
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Ringworld is unstable!
https://physics.stackexchange.... [stackexchange.com]
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Indeed it is, which is why a later story from them explained that Ringworld relied on solar powered control jets.
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A single-piece Dyson sphere is probably unworkable, but multi-segment ones aren't that bad. My favorite one so far is topopolis https://en.wikipedia.org/wiki/... [wikipedia.org] , sometimes called "cosmic spaghetti", which is a tube you live inside of that circles the sun as many times as you want. There are lots of details, but it's perfectly feasible...well, there aren't an obvious deal-breakers, like needing a material of impossible strength, or needing artificial gravity generators, or needing to build the whole thin
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Don't get too close (Score:1)
I read the brief article (sacrilege?).
It seems that to draw energy from the accretion disk etc. would require equipment/satellites to be very close. Wouldn't they be subject to the black hole's extreme gravitational pull?
Re:Don't get too close (Score:4, Interesting)
Wouldn't they be subject to the black hole's extreme gravitational pull?
Blackholes don't 'pull'/suck any more than any other mass does.
So long as they stay high enough so there is a stable orbit, and can boost to maintain that if needs be (versus the drag from the accretion disk and other losses), then there's no problem. If they have sufficient delta-v for continuous thrust they could also 'orbit' lower (above the event horizon, but inside the innermost stable orbit) if that's necessary for efficiency of the energy extraction mechanism. Obviously that risks expending too much energy for it to be worthwhile.
You just have to ensure you're not on a geodesic that can only go inwards. Now, there's almost certainly going to be relativistic effects to contend with; some mixture of Special (time going slower due to speed) and General (time going slower due to local gravitational gradient), but that's another matter.
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Don't forget tidal forces as you get closer to the event horizon, unless a really big black hole.
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IIUC, for most black holes the tidal forces only become extreme considerably within the event horizon. Where you need to worry about them is around neutron stars, where you have have a stable orbit that gets a lot closer. (Although, if you could survive the radiation, a little thing like tidal forces shouldn't be that much of a problem. There was a reason the "General Products" spaceship hull was invented for that story.)
Look at the size of that thing! (Score:4, Interesting)
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If your alien civilization built a Dyson sphere that was solid matter [the generally recognized form from the name] then no additional matter would pass closer to
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Or it will need some sort of huge port to guide planet or star size material to enter the Dyson Sphere to keep feeding the black hole occasionally.
Assuming you can create a Dyson Sphere around a black hole and make it habitable, presumably you will be able to guide "fuel" into the black hole as needed.
I think it would suck (Score:2)
Coming soon: black hole energy. (Score:2)
Just 2000 years away!
when it comes to converting mass to energy (Score:2)
... black holes are more efficient than fission, and fusion:
https://www.popularmechanics.c... [popularmechanics.com]
Chase the money (Score:2)
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Building a permanent base on the moon could be very useful. The technologies developed would assist on Mars (and the asteroids, which I think of as more important). And the far side of the moon is an ideal place for things like radio-telescopes which are bedeviled by local noise. For optical telescopes, space based is probably better, but that's because it's relatively easy to block optical wavelength radiation.
And the moon is close enough that we might be able to evacuate people if something went really
Practicalities (Score:2)
Knowing that:-
1. The "energy given off" by a Black hole is in fact the excitation of matter in the accretion disk, which will of course be consumed over time
2. The challenges of constructing the sphere around a black hole
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re 1 - the energy given off by a regular star is also based on a finite resource.
re 2 - challenge greater, but reward greater. if a black hole gives back 100,000x the reward (per the summary), it might be worth the effort. Hell it might in the end be a lot less effort if you have the technology to do either. At 100,000x more engergy is a lot. Also, a billionaire will do it for bragging rights. :p
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We estimate that our sun has been burning for 4.6 billion years and that it will take another five billion years to turn in to a red giant, destroying the Earth in the process. Now, it’s a bit harder to give any reasonable answer concerning the lifespan of an accretion disk orbiting a black hole: it’s g
Proof aliens don't exist (Score:1)
The article mentions advanced alien civilizations building stuff. This is a serious publication?
*We* are that advanced alien civilization. If no one has observed a Dyson Sphere its because we were the first.
Seeding them throughout the galaxy will act as a beacon for any primitive species looking through their telescopes for signs of extraterrestrial life.
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Seeding them throughout the galaxy will act as a beacon for any primitive species looking through their telescopes for signs of extraterrestrial life.
Not for up to 100,000 years. It’s not even that short in galactic time, 70,000 back and forth communications across just our galaxy would take since the dawn of time. On galactic scales, distance separates in time fundamentally and the universe is far more isolated than most people imagine.
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Your point is valid, but your conclusion is incorrect. You neglect parallel processing. There are several black holes around...the central one probably isn't feasible to use (for multiple reasons.
OTOH, I don't think a classic Dyson Sphere as imagined is possible for any technology. But there are ways around it which still capture much of the energy of the central mass. And I surely don't believe that any species based around chemical metabolism would live in a place hot enough to emit ultra-violet. So
I don't know... (Score:2)
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The purpose of a Dyson Sphere is to capture all the energy emitted by the contained system. It's probably impossible in the classic form for multiple reasons, but there are alternatives that are a lot more plausible and can do most of the same job. (My favorite is the topopolis.)
Ringworld is not only unstable, it requires a material with probably impossible strength to build. And a Pak protector to maintain it.
Temperatures in excess of 3000 kelvin (Score:2)
above the melting point of known metals
My light bulb would like a word with you.
Landauer's Limit (Score:2)
Romulans (Score:2)
Meh, the Romulans have been doing this for years; except they use an artificial micro-singularity (and it powers their ships).
It would be particularly humbling (Score:2)
if the first evidence we have of extraterrestrial intelligence is detecting their Dyson sphere black hole generator.
The important question: why bother? (Score:2)
There seems to be this odd misconception that an advanced society will need an absurd amount of energy to function. I can only guess that this has been assumed by looking at our own technology and energy use. However, technology like quantum dot cellular automaton shows that processors do not need a large amounts of energy to function.
Furthermore, the idea of building megastructures to reside in or upon is foolishness because the optimal megastructure (never fails and requires maintenance free) is natural
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There seems to be this odd misconception that an advanced society will need an absurd amount of energy to function. I can only guess that this has been assumed by looking at our own technology and energy use.
Basically - people who like to spend time talking about alien civilizations seem to have no concerns regarding extrapolating from a single data point.
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Futurists do this a lot and it's rather annoying. People that speak about aliens are just futurists with the exception that they are projecting their view of the future of the human race onto aliens.
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Furthermore, the idea of building megastructures to reside in or upon is foolishness because the optimal megastructure (never fails and requires maintenance free) is naturally occurring: planets.
I can't see why any advanced civilisation would want to build artificial living spaces when the optimal living space already exists - caves.
Yes, sorry, that's a bit facetious, but surely the point of megastructures is that you can build them where you want? You don't need a solid planet around a star (never mind a habitable one) when you can build some kind of orbital or sphere. I'm not an expert, but is a planet easier to make from scratch than say an orbital belt? Also at that stage of a civilisation, wha
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the point of megastructures is that you can build them where you want
Any why would you want to be in the middle of nowhere?
I'm not an expert, but is a planet easier to make from scratch than say an orbital belt?
Definitely. All you have to do is push a bunch of asteroids close together.
Also at that stage of a civilisation, what is the population?
Honestly, probably not as high as you seem to think.
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Still, megastructures are probably a bad idea. I like the idea of macrolife, but anything much larger than a large city is probably a bad idea. You don't want to put all your eggs in one basket.
I'd prefer a design that can start fairly small, say .5km by .5km by .5km as a rough volume (though not the shape) and grow as desired by adding pieces. Ideally it should also be able (when large enough) to split in half, like an amoeba. Eventually it might evolve into a "multi-cellular" life form, but we aren't
What about us? (Score:2)
Researchers have shown that highly advanced alien civilizations could theoretically build megastructures called Dyson spheres around black holes to harness their energy, which can be 100,000 times that of our Sun.
I guess they don't think Humans will ever be that highly advanced ... :-)
Environmental impact (Score:4, Funny)
While we are at it is still ok to call them "black holes"? Should we not be calling them "optically challenged spaces"?
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One of these days I'm going to write an environmental impact statement for a large asteroid, like the one that killed the non-bird dinosaurs.
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Not to forget checking for any endangered (or otherwise) living things in / around the black hole before you are sure you are not affecting any other lifeforms by building the Dyson Sphere.
Why? (Score:2)
There are so many other sources of energy that are cheaper and closer to home.
We might be alone (Score:2)
It sucks, but frankly, it is becoming more and more plausible that we are the most advanced beings in the universe. Where the fuck are the aliens?
They haven't built anything, no large-scale structures. I reckon humans 1000 years from now would have structures detectable from Andromeda and we'd be computer-hybrids.
Is advanced technology imatginable (Score:2)
OTOH, we might be like neolithic farmers in 7000BC trying to imagine present day technology 10,000 years in advance - and have essentially none of the scientific knowledge required to imagine that technology.
Tail of the Dragon (Score:1)
Yes, but ... (Score:1)
Black holes are the worst (Score:2)
A black hole is a lot less interesting than a star of the same mass. The difference is that there is no upper limit to the mass of a black hole. So in very crowded , very active places there is a lot of stuff floating about which the black holes can vacuum up. They can't vacuum up their surroundings when these are empty. This does indeed offer opportunities to harvest energy but
- when there is so much activity there are many more sources of energy
- when there is so much activity you'd rather be somewhere el
Theoretical physicists using fantasy again. (Score:2)
"3000 K, above the melting point of known metals" (Score:2)
How did that slip through?
"one somehow capable of surviving temperatures in excess of 3000 kelvin, above the melting point of known metals"
Melting points of 4 known metals > 3000K:
Tungston 3683K
Rhenum 3453K
Osmium 3318K
Tantalium 3269K
K = C + 273.15.
Who cares? (Score:2)
Go exercise, don't waste time on such nonsense.