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I have seen some questions in this site regarding how to weaponise black holes. One very funny one was the Black Hole Launcher, which many to quick to point out how absurd that was. However, I had another idea which I think might be more viable, where instead of having the black hole be a "projectile", the black hole is formed "on impact".

More specifically, I referred to how high-energy particle collisions can temporarily create Micro Black Holes, such as in TeV Particle Colliders or when Cosmic Rays interact with the atmosphere. Of course, they only last for a while before they evaporate into Hawking Radiation.

To solve this, I searched for the energy requirements to make stable Micro Black Holes, and it seems that 100 TeV is enough to make Micro Black Holes that are stable. So, I thought, if we have strong enough particle accelerators that let particles be as energetic as that, and make the beams collide, it is likely that Micro Black Holes that last for a while can be made on the spot.

It is something like this question, but rather than move a Black Hole, it makes them.

I am also aware that normal and current particle accelerators are HUGE and bulky and inefficient, so I decided to just have some unobtainium (Q-Balls), which allows particles to have such high energies while letting the weapon be handheld (or at least artillery-sized) at the same time.

So far, it seems more viable than the Black Hole Launcher by a mile. Also, as an upside for this weapon, the same accelerators can be used to feed the stable Micro Black Hole. However, I am still stumped by a single question: Just what are the effects of such a weapon, both the high-energy particles and the Micro Black Hole? What harm can they do?

PS: As shown in my comments, these Black Holes can either be as light as a few micrograms, or as heavy as asteroids and mountains. Also, 100 TeV only seems to be a bare minimum. Lastly, when I mean stable, I mean "last forever" kinda stable. Extremal, if you will.

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  • $\begingroup$ From page 2 of the paper, "In this work we assume that there is no Hawking radiation." $\endgroup$
    – notovny
    Dec 1, 2020 at 16:22
  • $\begingroup$ Is this little more than the scifi "implosion grenade" trope, as seen in Thor: The Dark World, Warehouse 13, and others? Also, you're talking about particle accelerators. What happens when the fist particle hit is a nitrogen atom right outside the barrel of the gun? $\endgroup$
    – JBH
    Dec 1, 2020 at 19:13
  • $\begingroup$ And later, they say that evaporation is still gonna happen in one way or another. $\endgroup$
    – CYCLOPSCORE
    Dec 1, 2020 at 23:07
  • $\begingroup$ "100 TeV is enough to make Micro Black Holes that are stable" is not true. 100 TeV black holes would be possible only if the Planck scale is much lower than it appears to be, and even in that unlikely case, they'd evaporate in a minuscule fraction of a second. To produce a stable black hole you'd need many orders of magnitude more energy (roughly $(\text{desired lifetime} / \text{minimum lifetime})^{1/3}$, I think). $\endgroup$
    – benrg
    Dec 1, 2020 at 23:51
  • $\begingroup$ Actually, Q-Balls can make particles go far beyond 100 TeV, in fact, they can let particles reach as much as 100 EeV, around the same energy density as the Electroweak Scale. What I present is just the minimum. $\endgroup$
    – CYCLOPSCORE
    Dec 2, 2020 at 1:09

2 Answers 2

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What can they do? Practically nothing.

You didn't include the tag, so I'm going to assume that your source is right and stable black holes this size are possible.

Now, let's get into what they can do. As my main source, I used an article by CERN about the safety of LHC:

If stable microscopic black holes had no electric charge, their interactions with the Earth would be very weak. Those produced by cosmic rays would pass harmlessly through the Earth into space, whereas those produced by the LHC could remain on Earth. However, there are much larger and denser astronomical bodies than the Earth in the Universe. Black holes produced in cosmic-ray collisions with bodies such as neutron stars and white dwarf stars would be brought to rest. The continued existence of such dense bodies, as well as the Earth, rules out the possibility of the LHC producing any dangerous black holes.

In other words, as long as there are big objects in the universe (like Earth), no black holes that tiny are going to have any measurable effect on anything. It doesn't say it explicitly (maybe it does and I just didn't see it), but here's my explanation (bear in mind it might be completely wrong): It's just too little mass to have any gravitational pull. From what I see on Wikipedia, we're talking on the scale of micrograms. The earth, to get a 1g acceleration inward, has trillions of trillions of trillions of kilograms of mass. These black holes are far more affected by other objects than other objects affected by them.

There's my best guess, I hope it helps.

But while I'm at it, I might as well give you an idea for how you could massively scale up your particle accelerator. :)

This idea is from Death's End by Liu Cixin, the third book in the Three-Body Problem trilogy (if you haven't read it, I highly recommend it). In it, they construct a massive particle accelerator that rings the entire solar system. It's not enclosed, since one of the main reasons LHC and other accelerators are enclosed are to make a vacuum, which we already have in space, and each ring speeds up whatever it is and sends it shooting off to the next ring, which continues the process. Eventually, they let it go shooting away from the solar system at near lightspeed.

Don't know if that last bit is helpful, but I couldn't resist sharing what I think is one of the coolest gadgets I've seen in sci-fi.

EDIT: Okay, so you've now told me that these can be up to trillions of kilograms. So I'm going to go with the figure of a trillion for this next bit (also please note these are guesses, we don't actually have data on this):

If fired at a person, the person would be torn apart by tidal forces well outside their Roche limit (somehow it feels a bit wrong to apply that term to people, but black holes will do that). Within a couple centimeters of the black hole, there are hundreds of m/s^2 of acceleration, but a meter away it's pretty much negligible. So if they fire for your heart, you'll pretty much have your heart ripped out as the rest of your body stays intact.

If at a planet, here's where it gets a bit interesting. I'd expect it to be like Randall Munroe's Neutron Star Bullet scenario (which I can't find online, so I guess you need the book what-if to check it out): It'll fall toward the center of the planet, ripping its way through the same way it rips through a human's body. Once it's there, it'll kinda just... stay there.

At that point I see a couple options. (1) It'll rip everything within reach and then just stay right there in the middle of the planet chilling. (2) Pressure's too much or something so that whatever's outside keeps getting pulled in. The black hole grows significantly (okay, it grew significantly in number 1 too, but not as much) and keeps growing. It might possibly get large enough to cause serious problems for us unsuspecting humans above.

Again, this is guesswork. I've never seen a trillion kg black hole and I haven't had the chance to fire them at someone (though the first test subject might be an unsuspecting little brother). If you do happen to get data, please let me know! I'd be fascinated to see real stuff on this. But I guess that's not likely.

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  • $\begingroup$ Well, that microgram stuff is only the bare minimum. Actually, these Micro Black Holes can be as heavy as trillions of kilogrammes. Let that sink in. $\endgroup$
    – CYCLOPSCORE
    Dec 1, 2020 at 12:03
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    $\begingroup$ @CYCLOPSCORE I'd assume that would take exponentially larger energy to create, so I guess in that case it depends how far you're willing to push your handwavium/unobtanium Q-Balls. Trillions of kilograms would definitely have more of an impact, but since we haven't seen any of those I can't find any specifics on what that would look like. Still, the gravitational pull would only be 0.07 m/s^2 from a meter away and barely anything from further. It would also be tiny; something on the scale of a tenth of a millimeter. $\endgroup$
    – Benjamin Hollon
    Dec 1, 2020 at 12:15
  • $\begingroup$ I mean, that wouldn't be much if you were just shooting at the environment. But imagine if you were shooting the two beams directly at someone. $\endgroup$
    – CYCLOPSCORE
    Dec 1, 2020 at 12:29
  • $\begingroup$ @CYCLOPSCORE I see, I was thinking from the perspective of larger targets. Since it's spawned on collision, that would definitely be close enough to have serious gravitational forces. There's no data I can find on black holes this small, but my guess is that you'd be torn apart by it. Huge tidal forces because things closer to it will be pulled exponentially harder and your body parts away from it will hardly notice it's there. If I'm doing my math right, part of you 1cm away will feel 600+ m/s^2 while the rest of you, 1m away will feel almost negligible pull. Easily within your Roche limit. $\endgroup$
    – Benjamin Hollon
    Dec 1, 2020 at 12:44
  • $\begingroup$ Though now that I think about it, something similar would probably happen if it were on Earth. I'd expect something like xkcd's neutron star bullet scenario (which doesn't seem to be posted online, it's just in the book). Basically, it would be sucked down into the center of the Earth. But because it's a black hole it might grow and cause serious problems if it didn't mess up its stability first. $\endgroup$
    – Benjamin Hollon
    Dec 1, 2020 at 12:46
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For starters, if you have a weapon that is capable of generating a black hole, you've already got a blockbuster on your hands. It is simply firing a lot of energy in a single point, so at a much lower setting you could easily destroy stuff.

If you can make a bullet-sized black hole, you can level a city. The black hole's gravity will be negligible - the amount of energy involved will not. I'd like to refer you to my answer on another question, Finding out the mass of a black hole for it to last ten thousand years:

(...) a black hole with a mass of 1.55 million metric tons and measuring 0.0000000046 nanometers across (~40 times wider than an atom). Any gas around it may reach a temperature over dozens of trillions of kelvin. At the distance characters and portals will be from the black hole, that means enough luminosity to probably cause a lot of destruction. As per the comments in this answer:

The black hole will emit 150 TW of blackbody radiation at 80 tera-Kelvin. You won't be as much sucked in as literally torn apart by gamma radiation. The black hole will "only" emit 16 grams of photons per second (yup, you read that right), but they'll be moving at the speed of light. For comparison, the Hoover dam produces measly 2GW, and it's much bigger than a 20-meter sphere.

-John Dvorak

150 TW means that, in a little over four hours, the black hole emits as much energy as all nukes ever detonated in history (until 2020), combined.

Supposing you shoot nanometric black holes and you can control them so that they disappear after just one second, it is still a bullet emitting ~10 GJ of radiation, which is about five Hoover dams all pouring out all their output into a small point for a second. You better be very far away from your target when you shoot.

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