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I'm writing a science fiction, although I'm not from a physics background. A part of my plot is:

In a futuristic Earth threatened by huge power demand and climate change, a scientist creates a quantum singularity to generate power.

Garbage is thrown into the quantum black hole, which is then converted into clean energy, used to meet the world's power demand.

It was hypothesized that once the mini singularity reaches a certain, manageable size, they'd stop feeding it, and it would spontaneously decay by Hawking Radiation.

But to the world's horror, the artificial quantum singularity never decayed by Hawking Radiation, and now poses a threat to the whole world.

Does this plot violate laws of physics, or is it feasible in a futuristic Earth with access to much better technologies? Could you please suggest anything else, if there are plot-holes?

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    $\begingroup$ The smaller the black hole the hotter it get, yours must be too small to do anything why bother about it. $\endgroup$
    – user6760
    Sep 8, 2016 at 10:09
  • $\begingroup$ Hawking radiation is how you get energy out of a black hole so if they were getting energy out of it would be radiating hawking radiation. If it stop it would mean that for some reason the environment is too hot which would break physics as i know it --- Take a look at this video youtube.com/watch?v=Qam5BkXIEhQ $\endgroup$
    – Durakken
    Sep 8, 2016 at 10:48
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    $\begingroup$ I don't think this is worth putting in an answer, but as an "out" you can say that the physicists kept feeding the black hole because they weren't getting a detection of radiation and assumed they simply needed the black hole to be bigger to create a detectable amount. Then they feed it a bit too much and off it goes. Humor points if they finally detect Hawking Radiation when they start to see the containment area flexing inward. I actually quite like this story idea - be sure to leave a link if you write the story and publish it online. $\endgroup$
    – GrinningX
    Sep 8, 2016 at 14:01
  • $\begingroup$ See this answer. Using power for something other than propultion does not change the particulars of power production and logistics of feeding the micro-black hole. $\endgroup$
    – JDługosz
    Sep 8, 2016 at 14:48
  • $\begingroup$ If you mean black hole then it takes a huge amount of power to make a black hole big enough not to decay in a split second. Dyson sphere required. $\endgroup$
    – Donald Hobson
    Sep 8, 2016 at 20:04

4 Answers 4

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Yes, it does violate laws of physics

Garbage is thrown into the quantum black hole, which is then converted into clean energy, used to meet the world's power demand.

I have been waiting for a time to use this image:

enter image description here

What do you mean "is then converted to clean energy"? How do you suppose that happens? That is the miracle right there. And especially so if you then say that Hawking Radiation does not exist.

I would say that if this future mankind of yours has such a command of the elements of nature, to a degree where they can make singularities, then making nuclear fusion power work should be very easy since we are tantalizingly close to that already today.

But if you still want this as a plot-device, I would say: screw it with the laws of physics and just handwave it. You have already thrown Hawking out with the bath-water so you are free to make up whatever you want. :)

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    $\begingroup$ A good answer with a good illustration, so it got my upvote. Sorry double negatives confuse me too. $\endgroup$
    – a4android
    Sep 8, 2016 at 10:18
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    $\begingroup$ @Bagho You are missing my point here: your plot element must break the laws of physics because your scientist character did something that they expected to operate in a certain manner, according to some laws of physics or others. But this thing he created operates differently, i.e. the laws of physics as we know them were actually wrong and as such are broken. So it its not a matter of trying to avoid breaking the laws of physics with your story; you must break the laws of physics, otherwise you do not have a story. $\endgroup$
    – MichaelK
    Sep 8, 2016 at 10:30
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    $\begingroup$ @Bagho My suggestion was call it a quantum singularity. There are no science rules for them. It's all handwaving. Michael Karnefors' suggestion about dark energy is good too. The runaway power source could be dark energy collector they can't shutdown. Or call it a zeta power source, then zeta power can be anything you want it to be. Sometimes being too scientific can ruin a story. Only explain as much as you know or understand, steer clear of too much science if you don't understand it. Star Trek uses 'fluffy science', but that's all they need to tell a story. $\endgroup$
    – a4android
    Sep 8, 2016 at 10:33
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    $\begingroup$ +1 on what @a4android just said. If you try to go for scientific accuracy you just as likely likely to ruin a story instead of strengthening it when you are dealing with things like this. Star Trek uses vague techno-babble to reach suspension of disbelief and then swiftly moves on with the story. Always keep your story close at heart because everything you create in terms of a world, concepts, physics and so forth are there to support the story, and not to steal the spotlight from it. $\endgroup$
    – MichaelK
    Sep 8, 2016 at 10:37
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    $\begingroup$ Thank you very much, Michael, Android. Now I feel confident enough to go on handweaving the plot, without worrying much about physics. :) And I'd use the term Quantum Singularity as you suggest, (or Artificial Singularity since Star Trek holds copyright lol.) They'd pour some garbage, 30% of whose mass would be converted to Gamma radiation. This Gamma would be harvested. But then this man-made singularity would pose a threat to mankind. $\endgroup$
    – Bagho
    Sep 8, 2016 at 10:41
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The garbage gets converted to gamma radiation... that IS Hawking Radiation. And it should boil away if you stop feeding it. So have your scientist discover that Earth just happens to be in a large patch of nearly-undetectable dark matter, and then discover that dark matter feeds a singularity just as well as regular matter. In other words, we aren't feeding it, but it gets fed anyway.

Problem solved, totally within current known theory. We know dark matter exists, but we don't know what it is, but it interacts through gravity, so theorizing that it would go to a singularity is easy. It might not create gamma rads itself, but it would make the singularity bigger.

[edit] Snyder005 below notes some difficulties with this idea. I do still think you could find a solution similar to the one I proposed, but it will likely take more physics questions to work out. Which is a great segue to my original closing paragraph...

And if that doesn't work for you, you still don't have to break the known laws of physics. You just have to propose new physics. Create a new theory that explains why the hole doesn't boil away. That's your license as a sci fi author. Just make it as consistent with today's science as possible so that you help readers explore science instead of leading them away from it. :-)

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    $\begingroup$ Clever, but the dark matter is very hard to aim to the tiny BH. It does't form an accretion disk and can’t lose energy that way, so it will almost all pass by the BH in hyperbolic orbits. Remember, blqck holes don't “suck”! Gravity works like it always does. $\endgroup$
    – JDługosz
    Sep 8, 2016 at 14:53
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    $\begingroup$ Don't have to aim if there's enough just passing through. A stream of dark matter passing through the area should (in theory) stick, and be impossible to shut off. Even if only a small amount sticks, it might push the singularity beyond designed containment limits. $\endgroup$
    – SRM
    Sep 8, 2016 at 18:12
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    $\begingroup$ Unfortunately there are some errors in this answer with regards to physics. Hawking radiation need not be gamma radiation, in fact it would most likely be electron/positrons, and low energy radiation. Also the dark matter around us is contained in a halo, that is very diffuse (1 proton mass in a few cubic centimeters) and homogenous. Dark matter does not clump on small scales, so an appreciably large and massive patch would not form, nor would it be undetectable, since it's gravity would be easily detected. $\endgroup$
    – Snyder005
    Sep 8, 2016 at 23:27
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    $\begingroup$ We don't really know the small scale clumping behavior last I checked. Got citations on that? And just because it could be detected doesn't mean anyone thought to do so before generating the singularity. $\endgroup$
    – SRM
    Sep 9, 2016 at 1:46
  • $\begingroup$ arxiv.org/pdf/1405.2204v1.pdf discusses small-scale clumps, however even these have masses less than a solar mass spread over ~206 AU squared (larger than our solar system). We can constrain small scale clumping behavior just using the knowledge that dark matter is pressureless, and cannot dissipate energy through radiation. Where as dust and gas will spiral inwards, and heat up, dark matter cannot, thus it does not form compact objects. Microlensing also provides constraints on MAssive Compact Halo Objects. $\endgroup$
    – Snyder005
    Sep 9, 2016 at 15:20
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The previous answers talked about Hawking Radiation, but I propose you use a different method of generating the energy, known as the Penrose process. Of course this assumes you are willing to 'hand-wave' away the development of any such black hole, but otherwise this process would not violate our current laws of physics.

The Methodology

In a nutshell, you form a rotating Black Hole, and throw matter at it. If you split the matter just right, one half falls into the black hole, and the other half escapes, with more angular momentum than the original. The result is energy extraction from the escaping half, while the black hole's spin slows down, thus obeying the laws of physics. Energy is extracted from the black hole's spin.

At some point your black hole will slow down too much and you won't be able to extract more energy. How do you keep generating energy? Simply keep throwing matter into your black hole, but don't split it and let it all fall into the black hole. This will add angular momentum and increase the spin of the black hole, readying it to generate energy again!

How You Can Make It Work

In terms of your story, lets say your scientist has a breakthrough and creates a stable rotating black hole. He/She then decides to solve the energy crisis. After some calculations he/she decides if they throw matter at the correct incidence angle, speed, and quantity, they can use the Penrose process to extract energy, while also balancing any Hawking radiation. Even better, they will throw all the worlds waste into the black hole and solve the trash crisis as well.

However something goes terribly wrong, when (by accident, sabotage, miscalculation), more matter is thrown in than intended and the black hole's growth overcomes it's rate of radioactive dissipation, and it starts to grow uncontrollably. For instance, perhaps the "feeding" process is automated, using probes to monitor the black hole's mass and spin, but the spin monitor fails, so the program thinks the black hole is not spinning. The program then starts "feeding" the black hole in an attempt to start it spinning again, unknowingly causing uncontrolled growth.

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  • $\begingroup$ Great idea! Thank you very much! I'll repost soon with a plot, considering all the invaluable info you all have given me! $\endgroup$
    – Bagho
    Sep 11, 2016 at 8:28
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The major plot hole is that no one would build such a power generation system without first checking to see whether black holes really do evaporate via Hawking radiation. Why? Because Hawking-radiation evaporation is a very violent process, and you'd want to make sure you could contain the process of "shutting down the power station and letting it explode". So you'd test things out by first making really small mini black holes somewhere out in space and letting them decay. (And then even if it worked, no one would want such a power plant anywhere near them in the first place.)

There are two potential ways to get power out of a black hole:

  1. Take a massive black hole (too massive to evaporate in any reasonable amount of time) and throw stuff ("garbage") at it to create an accretion disk; harvest the light and other forms of radiation coming off the accretion disk.

  2. Create a very small black hole and (starting immediately) feed mass into it fast enough to offset the Hawking radiation, setting up a delicate balance where the black hole's mass stays constant. In this case, you're getting some combination of accretion-based energy and Hawking radiation from the black hole itself.

(This would only work for black holes at least a few million tons in mass, because the Hawking radiation from a very small black hole would probably be intense enough tend to push away the stuff you're trying to feed into it, and even if it wasn't, you would probably have to send the mass in faster than the speed of light, which isn't possible.... Also, the Hawking radiation increases as the black hole gets smaller; for black holes that aren't large enough to destroy a city when you stop feeding them [see below], the transient power output is tremendous, so the processes of feeding the black hole and containing the power output would be rather difficult...)

So what happens when you stop feeding it? A black hole with initial mass of 230,000 kg will decay in about 1 second, releasing energy equivalent to 5 trillion megatons. An initial mass of 1 kg decays in about $10^{-16}$ seconds, releasing about 20 million megatons. A 1-milligram black hole decays in about $10^{-26}$ seconds, releasing about 20 megatons. (See here for formulas. These are crude, and more correct versions might change the results by factors of ten or a hundred, but that won't help you.)

You can see why NIMBY opposition to a mini-black-hole power plant might be pretty strong.

[Responding to the comment:]

Is it possible to slow down feeding the black hole, instead of totally starving it days (or years before planning to shut down the power station?) so that the explosion is not as violent, but gradual and controlled?

No, that will actually make it worse.

The problem is that as the black hole gets smaller (by losing mass-energy to Hawking radiation), it gets hotter and thus radiates more. When it's very small, it radiates with enormous power. A 1 kg black hole would have a power output of $3.6 \times 10^{32}$ watts -- a rate of about $10^{23}$ megatons per second. And bear in mind that you would have to feed it at least that much mass-energy equivalent each second (if that's even possible) to keep it from getting smaller and hotter and more luminous.

Really, the safet way to "shut down" a black hole power station is to shove lots of mass into it, so that the Hawking radiation goes down and the lifetime goes up. If you can boost the mass up to about one hundred billion tons or so, then the Hawking radiation will only amount to about 30 kilowatts and the lifetime will be about 100 billion years, so you can let some other poor bastard (civilization) worry about its ultimate fate.

[Edited to correct calculations and address question in comment]

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  • $\begingroup$ Thank you for the information. Is it possible to slow down feeding the black hole, instead of totally starving it days (or years before planning to shut down the power station?) so that the explosion is not as violent, but gradual and controlled? $\endgroup$
    – Bagho
    Sep 11, 2016 at 8:27
  • $\begingroup$ I figured it would take longer than a comment to address your new question, so I went ahead and edited my answer (and fixed some silly math errors; the result is that things are even worse...) $\endgroup$
    – Peter Erwin
    Sep 11, 2016 at 18:12

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