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So in this world I'm building there's a bunch of reasons to, at some point, stop being nice and make sure someone is really, really dead. For this purpose they decided to weaponize black holes. Nothing says "stay down" as ripping them to shreds, heating them up as they accelerate, crushing them into a tiny sphere of fused matter around a singularity in space-time and then even that matter they consisted of is erased from the universe due to Hawking radiation.

First to get this out of the way, black holes evaporate, and as this thread says: Black hole launcher.

A one second black hole would already be thousands of tons. This handheld miniature black hole weapon wouldn't have anywhere near that mass so its ammo would evaporate almost instantly upon firing, where "evaporate" will be closer to "explode violently". To combat this the weapon would either need to use some kind of anti-quantum beam in the black hole's path to reduce the amount of Hawking radiation until it reaches the target, or the black hole would need to be fired really really fast. That last one doesn't seem very useful as it would still be evaporating violently while traveling to the target, unleashing most of its energy at the launch-point. So maybe there's a better idea out there?

How the (handheld) weapon works (as far as my knowledge on these subjects go):

Our Sun does not have the temperature and pressure to actually perform fusion in its core. As particles move they are subject to quantum effects, one of which means they have a chance to be somewhere else entirely. This allows these particles to "tunnel" into another particle they wouldn't be able to fuse with normally and start a fusion reaction. The temperature and pressure of the sun only make the chance of this happening more likely. The weapon has a carefully calibrated system that changes the chances and makes it almost 100% likely that a large amount of particles with a certain mass will converge simultaneously and form a black-hole, preferably with a tiny delay so that this happens a distance after the projectile has left the barrel.

So for my question: How effective would such a weapon be? Would it basically be close to an anti-matter bomb in that it just releases butt-loads of energy in a short period of time (to which there's protection in this universe, against such energy releases not antimatter which they sometimes use as an alternative to black-hole launchers), or would it really be able to be shot at a hostile say 100 m away and absorb something the size and weight of a cow without adding more techno-magic than the quantum-chance alteration at the end of the barrel of this weapon? Preferably without turning the owner of the weapon into part of the black hole.

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    $\begingroup$ "Our Sun does not have the temperature and pressure to actually perform fusion in it's [sic] core": except that somehow 6.2E11 kg of hydrogen are somehow fused into helium per second, generating 3.8E26 W of energy. $\endgroup$ – AlexP Sep 21 '18 at 15:05
  • $\begingroup$ @AlexP as mentioned, this is because of quantum mechanics rather than temperature and pressure. Here's an example article explaining it: forbes.com/sites/ethansiegel/2015/06/22/… $\endgroup$ – Demigan Sep 21 '18 at 15:11
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    $\begingroup$ Except that those quantum mechanics effects are due to the temperature and pressure. $\endgroup$ – AlexP Sep 21 '18 at 15:32
  • $\begingroup$ "1 second black hole would already be thousands of tons" - Lets presume that the launcher is much much lighter and can be handheld - but who will be holding the ammunition? $\endgroup$ – Alexander Sep 21 '18 at 16:43
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    $\begingroup$ @Demigan, Technologically, not really unless you can smash pairs of super massive black holes together at different points in your ship. With magic, you just increase the gravity in a localized area (a lot) and then stop maintaining the gravity field. It would take a lot of power/mana/mojo to pull off. $\endgroup$ – ShadoCat Sep 21 '18 at 17:30
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A black hole gets its energy from its mass and the minimum mass of a stable black hole is 10¹⁶ Kg, so as a stellar killer mounted on a spaceship that could be made to work, but as a handgun you need to take into account the evaporation rate and 2 formulas exist:

For a mass much larger than 10¹⁷ grams:

Large Bullets

For a mass much smaller than 10¹⁷ grams, but much larger than 5×10¹⁴ g:

Small bullets

So each bullet is going to weigh at least 1,000,000,000,000 pounds: a bit impractical

Even if you would forget about a black hole handgun and go with neutronium bullets, you would have a ton of technical problems as free neutrons have a half life of about 10 minutes, cannot be contained by electromagnetic forces, so would have to be made on the spot, so a howitzer could be located in a desert and use the surrounding sand to create its shells as needed but a handgun would run into severe technical problems as well.

On top of this, you would need to accelerate these heavyweights to hit anything, so I would say: forget about kinetic black hole / neutronium handguns on a planetary scale...

The only possibilities are:

  • Drop de black hole or neutronium weapons from your storyline and concentrate on energy weapons
  • Take the scenery into intergalactic space and have a massive shout-out there.
  • Set your story in a hybrid Fantasy - Science Fiction universe and have it happen magically.

;-)

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  • $\begingroup$ I was thinking more on the lines of a modified rocketlauncher than handguns/rifles, those would be going too far even for this universe. It would likely fire a sphere of dense material and have the outer layers tunnel into the center with techno-magic. $\endgroup$ – Demigan Sep 21 '18 at 16:03
  • $\begingroup$ @Demigan Even a rocket launcher would pose severe problems: Physics is just against you on a planetary scale and that's why no one has ever used in in Science Fiction... ;-) Great idea, question needs more upvotes, but unfeasible scientifically. In a fantasy environment, anything is possible though: it's just magic! $\endgroup$ – Fabby Sep 22 '18 at 1:25
  • $\begingroup$ @Demigan Even a rocket launcher would pose severe problems: Physics is just against you on a planetary scale and that's why no one has ever used it in Science Fiction... ;-) Answer edited $\endgroup$ – Fabby Sep 22 '18 at 1:35
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    $\begingroup$ It's not magic! Its a perfectly scientific thingy done by the handwavium gun using unobtanium. $\endgroup$ – Garret Gang Sep 22 '18 at 2:54
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    $\begingroup$ It is a fantasy+science hybrid, hence the use of Black holes against people who wont always stay down. And I am going to be using technomagic to solve this, but the goal would be as little as possible with as good an effect as possible. $\endgroup$ – Demigan Sep 22 '18 at 6:42
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I was going to write a very long answer with physics and latex syntax and ****, *****ing about how this wouldn't work at all without . However, the lack of the tag coupled with my lazy pragmatical personality kept me from doing so.

You just want to know how effective such a weapon is. As a gun, you are always at the risk that you will shoot yourself on the foot, both literally and figuratively. There are a dozen ways you can miss a shot and the colateral damage will be more than the shooter could deal with. For example, should your aim from behind cover and hit the ****ing cover (happens more than I'd like to admit in paintball), you suddenly have a thousand tons of mass on your lap.

Even for a one second black hole, you would be facing a paradox much like the one from this previous question:

What effects would propellant that expands at near light speed have on firearm technology?

In short, quantum and relativistic weapons may sound cool to the ears of light sci-fi fans, but they are only ever practical for suicide bombers.

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    $\begingroup$ This wouldnt be a weapon you use lightly ofcourse, this is for the hypothetical superhero or supervillain with so many goodies they become nigh impossible to kill by other means. While there is nothing as close to superman in this universe it's a good example of a target you could want to hit with this. At that point "bad idea" and collateral arent your biggest worry as the next step is probably destroying the continent. I would be very interested in a black-hole weapon with as little technomagic as possible, what would the minimum physics magic be to get one working? $\endgroup$ – Demigan Sep 21 '18 at 17:24
  • $\begingroup$ @Demigan asking a 21st century dude that is like asking a caveman what minimum technobabble is needed for a flying jet. We don't have the knowledge to give you a proper answer. $\endgroup$ – Renan Sep 21 '18 at 17:57
  • $\begingroup$ we dont have a proper answer for Graphene yet either, but we can theorize with the knowledge that we have. A caveman who heard the question explained to him on his level would likely say "get big wings and a mouth at the end, then breathe in and blow hard", in his vocabulary ofcourse. Because thats the limit of his knowledge, and I find it extremely unfair to say "because the answer isnt discovered by humans for many years theres no proper answer" as if that finishes a question $\endgroup$ – Demigan Sep 22 '18 at 6:50
  • $\begingroup$ @Demigan alright, alright. You are going to need a flux capacitor that is able to provide energied at the teravolt scale, so handwave away how that is miniaturized for a gun. Physics holds that you cannot keep the entanglement of a particle pair if one is within a cleftal horizon, so you need to set the first tensor orthogonal to the forming black hole's barycenter. All that is beyond even near future technology, but if you can get it just right... $\endgroup$ – Renan Sep 22 '18 at 12:05
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The shortest answer of all is to forget about firing the micro black hole, but use it as a bomb or grenade. As it evaporates it releases ever increasing amounts of energy, mostly as hard radiation, so you have sphere hotter than a star in the final moments, blazing away at every frequency from gamma radiation to long radio waves. Shielding against that will be virtually impossible.

If you are not inclined to be a suicide bomber, the black hole and its containment unit is placed in a self driving vehicle and then sent to the address of the target. Precision isn't really much of an issue; several city blocks are going to be vapourized and large areas surrounding that will be irradiated, incinerated and blasted by high energy shock waves as the x-ray and higher radiation interacts with the atmosphere. Given even very small black holes have immense masses, you should be looking for a self driving truck to do the job.

Of course there is another issue to consider: the lifetime of quantum black holes is quite short, so you need to somehow prepare the entire package (including the black hole) within minutes of locating the target. Putting together a black hole is likely to take an enormous amount of energy and equipment, if I thought I'd be the target of a black hole bomb, I'd probably draw a circle around every high energy power plant and physics installation I knew of and clearly avoid this areas....

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Any black hole you're going to be able to make with such a weapon (I'm looking at how much matter you would have in close proximity to use) is going to be pretty close to an instant bang.

It will not be quite as sharp a shock wave as a nuclear weapon would produce as the energy release is slower--and, yes, that matters. Think of a fuel-air bomb compared to a conventional bomb. The former makes a much bigger boom per pound but fares poorly at cracking hard targets due to the shock wave being more spread out.

An antimatter bomb is pretty clean. The blast itself is pure gamma radiation (which quickly gets absorbed and replaced with an expanding ball of plasma), the only radioactivity left behind is from atoms that lost bits of their nucleus to contact with the antimatter but where not completely destroyed. A black hole bomb, however, emits it's energy as energetic particles. Those will have a fair ability to induce radioactivity in whatever they hit. Far more atoms get hit than in the antimatter scenario, thus there will be more induced radioactivity.

If you want to survive it that means you're limited to pretty small bangs. (Since you have a line-of-sight weapon you're looking at the detonation.) At this point the blast differences aren't going to matter anymore but it's still dirtier than the antimatter.

(And before someone brings up the Davy Crockett--that was not a suicide weapon. Yes, if you stupidly stood there when you pulled the trigger you would die, but if you did it properly you dived into a foxhole while the weapon was in flight. Now you have a lot of dirt between you and the blast, the bomb won't hurt you. Better be upwind, though!)

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