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I'm working on a sandbox astrophysics, economics and military simulation generator (there is no defined setting but I try to use real and hypothesized science for the most part) where different types of systems have various economic and/or military uses. But I'm struggling to conceive of any for stellar black holes, beyond being natural travel impediments and/or slingshots. Anything involving trade, resources or conflict would be really welcome as an idea.

Q: Are Black Holes Military & Economic Assets ?

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    $\begingroup$ Hi Wolf, welcome to Worldbuilding! Your question is very broad, could you focus your question some more, and add as much detail as you can think of about your world that is pertinent to the question, please? $\endgroup$
    – Joachim
    Commented Jan 29, 2022 at 19:08
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    $\begingroup$ There is no setting per se, it is a sandbox astrophysics, economics and military conflict generator. This question is purely about how scifi civilizations might use a black hole given our understanding of them and not as something unproven like a wormhole etc. $\endgroup$ Commented Jan 29, 2022 at 19:16
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    $\begingroup$ Upvoted because it's a nice idea, but it needs more focus. Better ask for ONE military or commercial aspect of your black holes, instead of asking for some general view about economy and military things. Success with the editing ! by the way, I wonder if stellar black holes would really be an impediment for travel.. Maybe you can use them, to do gravitational slingshots. Set your angle and velocity right.. and travel around it. On the other side, you could have a fantastic speed ! $\endgroup$
    – Goodies
    Commented Jan 29, 2022 at 19:18
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    $\begingroup$ You don't really have a metric for a "best" answer here though there may be multiple completely different valid answers, which is a bit of a warning sign that it might not necessarily be a good fit for this site. You've also hinted but not described the physics of your setting which can have a very substantial effect on what you can and cannot do with a black hole. If you have FTL, for example, all sorts of really interesting possibilities open up. I suggest you do a bit of editing and focussing. $\endgroup$ Commented Jan 29, 2022 at 19:51
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    $\begingroup$ I think this question can be refined or improved to be answerable. For example: "What are some commercial uses of a black hole to a society capable of XYZ?" or "What are the military applications of a black hole to a society capable of XYZ?" $\endgroup$
    – user535733
    Commented Jan 29, 2022 at 20:59

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Gravitational time dilation may have some useful applications. The closer you are to the black hole, the stronger you experience its gravity, and stronger gravity means you experience less time than people further away from the black hole. Of course, all gravitational masses cause time dilation, but black holes are especially small compared to other equivalent masses, so you can get much closer to them, and so the amount of time dilation can be much greater.

For example, if you have things which are used very rarely but require expensive ongoing maintenance - e.g. nuclear weapons - then you can put them near a black hole, and they will degrade slower relative to your frame of reference. That means lower maintenance costs.

You might also have some group of people who want to permanently live close to the black hole, so that they experience time slower and are able to benefit from a faster rate of technological progress from the outside world. This would mainly be people rich enough that they don't have to work to earn a living (as time dilation would proportionally reduce the value of their labour to people away from the black hole), but perhaps also include people with uncurable diseases who want to survive "longer" for a cure to be found.

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    $\begingroup$ Some leadership positions may actually be better with dilated time. A leader who is still going to be in charge in 300 years needs to consider how his policies will play out over such a time-frame, whereas no leader in real life needs to consider any consequences beyond ~20 years in the future. So placing at least some of your government near a black hole seems like a solid way to keep them careful. $\endgroup$
    – Ryan_L
    Commented Jan 30, 2022 at 6:25
  • $\begingroup$ @Ryan_L - but it becomes almost impossible for them to have timely reactions to acute problems. And if you split the government between the "long-termers" and "short-termers", then the two will always be at odds. $\endgroup$
    – Vilx-
    Commented Jan 30, 2022 at 11:35
  • $\begingroup$ This assumes that apparently time-dependent activities really ARE time dependent. Maybe these events 'decay' based on some factor other than 'time', but it just appears to be dependent on 'time' to us. $\endgroup$ Commented Jan 30, 2022 at 13:00
  • $\begingroup$ @Vilx The two being at odds can be a good thing. Many governments today are explicitly designed to have some internal conflict. Checks and balances, separation of powers. $\endgroup$
    – Ryan_L
    Commented Jan 30, 2022 at 17:08
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Behold, the Penrose Process.

Shoot a chunk of matter into the the black hole's ergosphere, and then split said chunk of matter into two parts right as it crosses the border.

One part escapes the ergosphere. One is pulled in. The part that escapes has more energy than the initial chunk of matter went in with.

In other words, this lets you harvest the black hole's rotational energy.

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Lighthouse

saggy

https://www.newscientist.com/article/2191429-our-galaxys-supermassive-black-hole-may-be-spewing-matter-right-at-us/

Some black holes are energetic radiation sources; depicted is Sagitarrius A aka "Saggy" at the center of our galaxy. Your people use their black hole with its characteristic electromagnetic visibility as a beacon, Lighthouse of Alexandria style.


A more esoteric use would be to pan the emissions for special particles. Autonomous drones arranged according to the same principles of a Dyson Sphere pan the emissions like prospectors pan for gold. Among the energetic protons and other common things are very uncommon things - super heavy nuclei, negative matter, antimatter and other weird matter forms which were forged in the hole and somehow wound up spewed into space.

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Harvesting energy

Hawking radiation is a theorized form of radiation generated by black holes. You can theoretically harvest this energy.

Not a fan of super theoretical ideas? Well there are plenty of other ways.

You can shoot some stuff in, have the black hole speed it it up. And you now have some power. You can do All sorts of other fancy stuff with it, point is you can get energy from a black hole, it can basically be a power plant.

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  • $\begingroup$ A black hole radiates black body radiation. But so does everything else. A black hole 2.5 solar masses would radiate less energy in a year as one atom of uranium decaying. $\endgroup$ Commented Jan 30, 2022 at 4:11
  • $\begingroup$ @Acccumulation black body radiation and Hawking radiation are separate concepts. $\endgroup$
    – Topcode
    Commented Jan 30, 2022 at 18:19
  • $\begingroup$ "black body radiation and Hawking radiation are separate concepts." What make you think that? "Combining the formulas for the Schwarzschild radius of the black hole, the Stefan–Boltzmann law of blackbody radiation" en.wikipedia.org/wiki/Hawking_radiation $\endgroup$ Commented Jan 30, 2022 at 21:47
  • $\begingroup$ @Acccumulation well the article you linked says “difference between the black hole radiation as computed by Hawking and thermal radiation emitted from a black body” which seems to state that they are not the same thing $\endgroup$
    – Topcode
    Commented Jan 30, 2022 at 23:20
  • $\begingroup$ The entire sentence is "An important difference between the black hole radiation as computed by Hawking and thermal radiation emitted from a black body is that the latter is statistical in nature, and only its average satisfies what is known as Planck's law of black-body radiation, while the former fits the data better." It sounds to me that they on average have the same output. At the very least they're within an order of magnitude. $\endgroup$ Commented Jan 31, 2022 at 1:14
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As an alternative to my other answer, you could construct a black hole bomb. Surround a rotating black hole with mirrors and shoot a laser into it. Over time, the laser is sped up as the black hole's gravity acts on it, but it can't leave - instead, it hits a mirror and is then reflected back towards the black hole, which speeds it up again, and bounces it off a mirror again, and so on and so forth.

Eventually, this laser is going to be packing a lot of energy - and, if you remove the mirror where it's going to hit next, it escapes.

This can serve as either a power source or a weapon, depending on whether you aim it at a set of collectors or somebody you REALLY don't like.

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  • $\begingroup$ Depending on which use case (weapon or power source) you think of first could be a good personality test. I personally thought weapon. $\endgroup$
    – Murphy L.
    Commented Jan 29, 2022 at 21:43
  • $\begingroup$ The laser does not hit the black hole because then it is gone. It hits a Mirror and is reflected, presumably away from the black hole. And as it moves away the energy it gained on the way in is lost. You could get that energy back by reflecting it back towards the black hole but we saw how that ends up. $\endgroup$
    – Willk
    Commented Jan 30, 2022 at 3:56
  • $\begingroup$ This sounds like a perpetual motion machine. The energy that a photon loses as it climbs out a gravity well is as much or more than the amount that it gains as it descends (and if you're in a frame of reference that is inertial with respect to local space, the photon wouldn't ever be gaining energy). So unless I'm misunderstanding your answer, this doesn't make any sense. $\endgroup$ Commented Jan 30, 2022 at 4:03
  • $\begingroup$ @Acccumulation It's not a perpetual-motion machine. It takes away a bit of the black hole's rotational velocity each time. $\endgroup$
    – KEY_ABRADE
    Commented Jan 30, 2022 at 4:05
  • $\begingroup$ @Willk It doesn't hit it, but it gets close to it. Each time it gets close, it gains energy by sapping some of the black hole's rotational velocity. $\endgroup$
    – KEY_ABRADE
    Commented Jan 30, 2022 at 4:05
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if it has an accretion disk it's a source of cosmic rays and relativistic particles, not a healthy neighbourhood.

they're good at turning mass into energy. But regular stars do that too if less efficiently, the stars are less deadly.

maybe you can think up a way to use them as gravity wave transmitters.

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Completely fictional, and just for fun...

  • Let's assume that a black hole exists perpendicular to the orbital plane of a solar system. It's far enough away to not threaten the solar system, but close enough to suspend disbelief for this next part.

  • Let's assume a traditional mono-molecular can't-be-broken-in-heaven-or-on-earth wire. And it's really long.

  • Let's assume an end of the wire is connected to a reasonably indestructible golf ball.

  • Let's assume the other end of the wire is attached to a piezo-electric generator on one of the orbiting planets and mounted on some whomping foundation blocks that are well attached to bedrock.

And then we fly it as close to the black hole as we can and set the hummer free!

Once the wire tightens, you'd have free power for the whole planet forever. The closer the golf ball gets to the black hole, the stronger the pull on the wire, the more power you get.

Besides, you can have stories like, "Commander, why can I see the bottom-half of the ship over there to our left? What'd we hit?" Given the tension on the wire, you might have a planet be sliced in half like a peach and not really know it happened.

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You could use them to put people in stasis. If you have a way of accelerating one, you can use it to drag a spaceship behind it without the spaceship experiencing local g-forces.

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