Containing a Singularity

[Oracle_Hunter]

@Cealocanth

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First, let's break down how dangerous a gravitational singularity is, and what happens if Our Heroes don't Do Something.

A black hole with an event horizon of even a nanometer is a serious threat to the planet, because no force in existence is capable of preventing any matter that passes into that event horizon from compressing down into a single, 0-dimensional point. Not electromagnetic bonds or repulsion between distinct protons and electrons, nor even the nuclear forces that keep subatomic particles from spacially overlapping.... and every atom ever discovered or produced has been considerably less than a nanometer in size, as measured by the diameter of its electrons' orbits. (Diameter of the nucleus might be a better measure for this threat, and it's several orders of magnitude smaller, but I'll stick with this.)

Outside of the event horizon (er, let's call it a few times the event horizon to be safe), we don't notice the black hole at all. It's actually not all that massive, and doesn't generate that much gravity; what's special about it is that it's packed so tight that the gravity it DOES generate reaches a critical threshhold before we reach the boundary of its mass. The problem isn't standing near the black hole; it's coming in CONTACT with it (or, at least, its event horizon). And I mean actual contact. What we normally think of touching something is actually nothing of the sort. When we, say, pick up a glass, the molecules in the glass aren't actually coming into physical contact with our hand. That's the stuff of nuclear fusion. No, what's happening is that the electrons in both sets of molecules are mutually repulsing each other, preventing actual contact from being made and actually holding the molecules quite a bit more than atomic distances from each other. It's like you have a "don't touch me" force field repelling everything away from you... but only a few nanometers away from you.

Except the black hole doesn't output this electromagnetic force, and thus isn't affected. It bump into atoms, and something oh-so-much worse than fusion takes place. Decent people don't think about these kinds of things.

If this black hole were free-falling (uncontained), then nothing would stop it from reaching the center of relative gravity (the Earth's core). Nothing at ALL. The good news is that it would have very little gravitational pull, so it wouldn't actually be drawing things into it, or significantly affecting but anything that DID come into it would go bye-bye, adding its own mass to that of the black hole's. It would sink through the ground, absorbing and consuming the matter it came into "contact" with, producing needle-hole about a nanometer in width headed towards the earth's core. More good news: this is not a large enough hole to allow for volcanic outflow or even trigger earthquakes.

So it gets to the earth's core. Atoms are pressed together pretty tightly near the earth's core, so our black hole's bound to come into contact with something. Velocity causes it to shoot past the center of the earth. It probably doesn't go through the exact center of mass, because rotational velocity at the surface will give it more of a parabolic path, but it gets close enough for government work. It then shoots past the center and back out towards the earth's surface on the opposite side of the planet, the hole to China, if you will.

Except it doesn't get there. It's been absorbing mass as it goes, and this mass had less gravitational potential energy relative to mass the closer to the Earth's core it was. By the time it reaches it's maximum "height", it's probably at least doubled in mass (I'd guess one or two orders of magnitude, rather, but couldn't begin to compute it), and most of that mass came from mantle or nickle-iron core which, if free to fall, would NOT break to the surface. The black hole never emerges, and after several oscillations where its movement is further dampened by absorbed matter, eventually stops moving (or close enough for government work) at the exact center of the Earth's core.

Note that this is STILL not causing tidal distortions sufficient for earthquakes, tsunamis, volcanoes, or so forth. As far as anyone at the surface is so far concerned, nothing at all has happened.

But they're going to be concerned very soon. Oh yes.

Pressure is extremely high at the core, with liquid or semi-liquid nickle-iron pressing in from all directions. For the black hole, this is like a duck being tube fed at massive speed without the unhappy prospect of being turned into fois gras at the end of the process. Consider any particular molecule at the core. Normally it's in a rough equilibrium of forces, with pressure from below being slightly higher than pressure from above, and this being offset by a fairly light gravitational pull downwards. But then the black hole EATS the molecules below you, and there's suddenly no pressure from below. You DROP, straight to the center of mass, actually propelled at tremendous speeds by the pressure of the molecules above... which follow you in turn. A nice arch or self-bracing support structure of some sort might stop this collapse, but no such solid structure really exists at the earth's core. The black hole consumes the entire core, as well as the liquid mantle.

The entire Earth is now a hollow crust, kinda-braced against itself, with nothing holding it "up". Sort of the arch I was talking about earlier. Except it's nowhere near solid enough for the job. The surface disintegrates -- a bit like the trailers for that 2012 movie I never saw -- and everything collapses Inwards. It's likely proceeded by earthquakes (but NOT volcanoes, since all the magma is being sucked inwards), but I doubt the crust would last more than a minute before it disintegrated. This is probably the first, last, and only warning anyone on the surface gets, and about when we would get very, very concerned for a very brief time.

At the end of this process, the black hole's event horizon is now a little less than 17.5 kilometers in diameter. The mass of the Earth hasn't changed, nor has its path through the solar system. It's just much, MUCH more tightly packed. Anything NOT held apart from the Earth's core by pressure (ie, physical contact) continues on its merry way unconcerned. The moon might wobble a little bit as the mass it revolves around compressed from a small but significant arc in the sky to a zero-dimensional point, but if so it is a very, very tiny wobble.

A black hole with an event horizon one nm in radius, which started this whole mess, requires a mass of about 670 million kilograms, or roughly one tenth the mass of the Great Pyramid of Giza.

The good news is that while a black hole that small can continue to exist in a somewhat stable manner, it cannot spontaneously form from its own mass. For that, you'd need a bit less than 3 times the mass found in our sun. Of course, you've introduced some super-tech magic to this and the black hole can be artificially formed. SEE WHAT YOU DID?

That's the long of it. The short of it is that a black hole with the mass of one of the Giza pyramids IS a threat and Our Heroes DO need to Do Something About It.

So what Something are we talking about?

Job 1 is detection. As mentioned before, this thing doesn't produce significant tidal or tectonic activity until the endgame. Gravitationally, it looks like any other lump of several hundred million kilograms (think a medium-sized hill) and I doubt some Lab Coats in Generic Uber Science Place a few miles away would ever notice a blip on their meters. So instead, Our Heroes need to stum-- er, discover it through Ancient Lore or The Villain's Plans.

Job 2 is containment. Ideally, this involves whatever existing containment has prevented it from already destroying the Earth. That failing, you need to get it contained BEFORE it falls through the ground.

There is no Job 3. If Our Heroes fail Job 2, then Job 3 is grab your ankles, bend over, and kiss your but goodbye.

So, to finally answer your question.... what can contain a black hole? Here's where we get to the Really Bad News. PRETTY MUCH NOTHING.

As mentioned, the black hole doesn't get repelled from contact with molecules. It can't be "held up" on some sort of pedestal, because it would just eat the pedestal. Other things that don't work are magnets, super-glue, or blowing on it really hard. About the only thing that DOES effect it is gravity, and that's working against you. An alternate strategy might be to build a cage of some sort around it.

A nice molecule shaped around the black hole could work, maybe some sort of carbon structure. This wouldn't keep the black hole from drawing mass in, so much as hold the mass back. The problem is that it also doesn't prevent the black hole from moving, and either slipping between the atoms of our cage molecule or consuming a few of them on the way out. Our cage might be held up by its environment; the black hole most definitely is not. It would be like holding a sieve filled with water, and expecting the fact that we're holding the sieve's handle to guarantee that the water doesn't leak out.

So for the cage strategy to work, it must be constructed AFTER the black hole stops moving and is already at the earth's core. Now, the cage molecule could theoretically work... except that in the center of the Earth's core, with the world collapsing around you, and on the threshold of a growing event horizon, is not the ideal environment for doing finicky and precise nanoengineering. The issues of physical access alone are staggering, as is the non-trivial question of where you stand while you work. Also, if the event horizon grows past a certain point, the black hole becomes too big for our cage molecule to work, and I suspect that this will have been done already by the time that the singularity settles to rest at the core. Remember, the cage ONLY works if the black hole is NOT moving around relative to the mass around it.

So now we have to reach into really theoretical physics, which probably will NOT be available for applied science in the next few generations. There are a few promising things here. In particular, I would suggest dark energy.

Dark energy is a hypothesized force, or, perhaps, an overlooked element of the gravitational equation. Observations of gravitation in the universe at large haven't quite jived with our ground-based laboratory experiments, or even orbital mechanics in the solar system. It's almost as if gravity is weaker over long distances... even weaker than the inverse-square law would suggest. Dark energy is a repulsive force that explains or expresses this. If we want to be absurd and ignore the fact that dark energy only seems to kick in over long distances (intergalactic), this could hypothetically be used for antigravity... and antigravity is EXACTLY the thing needed to keep our nanoscopic black hole contained. It's extremely theoretical physics twisted into an application that utterly ignores its actual properties of scale, and we have no reason to believe that we could ever intentionally generate it in the first place, and it's STILL our best hope.

In other words, Our Heroes need to use some of this Ancient Civilization's Magic Artifact Tech, because nothing WE invent will be ready any time soon.

Man, I don't know if this is all kosher, but it is close enough for jazz -- by which I mean D&D. Use this stuff to inform your background on the Doomsday Device.

On a related note, it's a fools errand to try to find "plausible" technology to contain something that can't even exist without using "implausible" means. I'd say it's best to keep as much of the hard stuff Black Boxed as you can (i.e. creating the Hole, containing the hole) and leave something impressive for the easy stuff. So, rather than an inscrutable fusion battery how about setting up an elaborate Geothermal Generator to power the whole thing.

A better question is why did the Ancients make such a dangerous device and leave it on the planet where they live? If you want a ludicrous but impressive answer, I'd go with garbage disposal.