The Black Hole Bomb and Black Hole Civilizations


Black holes are the largest collections of pure violent energy in the universe. If you come too close, they’ll devour you and add your energy to their collection. And so, the energy is lost to us forever. Or is it? It turns out there’s a universe cheat code. A way of powering civilizations until the very death of everything, or of constructing the largest bomb in the universe. But how? Didn’t we learn that all energy is trapped forever in black holes, even light? This is true. Everything you think you know about the weirdest thing in the universe is about to get weirder, for one simple reason: Black holes are spinning. When really really massive stars die, their cores collapse under their own gravity into black holes. This means something very big becomes very, very tiny. Like the tiniest anything can be in this universe. But stars are rotating and a fundamental property of our universe is that things that are spinning don’t want to stop spinning. We call this: angular momentum. And this angular momentum can’t go away. A big thing that spins and becomes smaller, spins faster. So, as the core of a star collapses, its momentum makes it spin faster and faster and faster, until it collapses into a black hole . And the black hole keeps on spinning, inconceivably fast. Some of them spin millions of times a second. Just like non spinning black holes, …spinning black holes have an event horizon and a singularity at their core, where all of their mass is concentrated. The singularity is usually described as a single infinitely small point with no surface area. But points can’t rotate, so a rotating singularity can’t be a point. Instead, it’s a RINGularity. A ringularity is a ring with a thickness of zero and no surface, spinning extremely fast, containing all the mass of the black hole. The black hole is spinning so fast, that it morphs space and time itself. It literally drags space with it, such is its power. This creates a new and super weird region of space-time: the Ergosphere, which envelops the black hole. If space and time are completely broken inside the event horizon, then they’re only half broken inside the ergosphere. Inside the ergosphere, nothing makes sense. It’s possible to enter it and then leave it again, but it’s probably not a great experience. You can imagine it like this: Falling into a static black hole is like sliding down a hole. Being inside the ergosphere of a spinning black hole is like spiraling down a deadly drain. The black hole transfers its own kinetic energy in the form of rotation, to everything that enters the ergosphere. The ringularity makes you dance whether you want to or not. You need to move faster than the speed of light just to stand still here, which is impossible. But here’s our cheat code: We can steal this energy, and there’s a lot of energy to steal. Take the supermassive black hole at the center of the Milky Way. We could steal as much energy from it as every single star in the Milky Way emits in a billion years combined. The easiest way to steal this energy is, oddly enough, to drop something into the black hole. We’ve seen that the ringularity forces energy on us when we enter the ergosphere, …which is a lot like being in a whirlpool, with space-time rushing around and around. If you’re clever you can use the water to your advantage, and swim faster than before. In practice, this means sending a rocket into the ergosphere, and making a trade with the black hole: We give it some mass-energy, and it gives us some of its rotational energy. But it’s not a fair trade, we get the better deal. Normally, if you fire a rocket, you exchange chemical energy for kinetic energy. This is like pushing yourself forward in a swimming pool. But if you fire a rocket inside the ergosphere, it’s like pushing yourself forward in a wave pool. The rotational energy of the waves gives you a much stronger boost than you could get just by pushing yourself. The boost from the rotation of the back hole is so big, that you leave the ergosphere with much more energy than you entered it. The black hole gives a tiny amount of its rotational energy to you, and slows down a little. Obviously, this requires a lot of food. Fortunately, black holes aren’t picky eaters. An advanced future civilization would probably harvest asteroids to drop them into the black hole when they needed an energy boost. But there’s an even better way to get energy from a black hole, and oddly enough, it builds the biggest bomb any living thing could ever hope to build: We only need two things to build a black hole bomb: a fast-spinning black hole, and a big mirror. The mirror has to completely envelop the black hole, …which is similar to a Dyson Sphere, a mega structure that harvests the energy of an entire star. Although, our mirror would be easier to build. Mirrors are simpler, and black holes are much, much more compact than stars. If we made the mirror 10 centimeters thick, the metal of a big asteroid would probably be enough material for a black hole with the mass of our Sun. Once our mirror is in place, we only need to open a window, and shoot electromagnetic waves at the black hole. You can imagine what happens next, by imagining tossing a ball at a wall, and it coming back faster than a bullet. The waves hit the black hole at light speed. A small proportion of the waves falls past the event horizon to disappear forever. But a much larger amount sloshes through the ergosphere, …where the black hole forces some of its rotational energy on them, and amplifies them. They now begin superradiant scattering, which are fancy science words meaning: “Bouncing around between mirror and black hole and getting stronger.” Every time they go around, they are getting exponentially stronger. By opening some windows in the mirror, we can extract the energy from the waves as fast as they grow. Which we could use, in theory, to create what would be for all practical purposes, an endless source of energy for trillions of years. Or, we could blow it up. If the waves are not released, they will continue to get stronger and stronger, …and take more and more energy from the black hole, until the mirror shatters. A supermassive black hole would release as much energy as a supernova, …making the bomb the largest explosion any living being could ever create. The beauty of the black hole bomb, the Penrose process, and the super radiant scattering, is that they are not science-fiction. In the far far future, this might be the only way to survive in our dying universe. After all the red dwarfs have cooled down, and all the white dwarfs transformed into black dwarfs, the universe will turn dark forever. Rotating black holes might be the only sources of energy in the entire universe that life could harvest. If so, the last living being in existence might one day end its life around a black hole. Which is equally chilling and uplifting. It turns out that even without any light, there are places we can go. Black holes are as interesting as they are mysterious, but there’s actually a surprising amount we do know. Using math we can calculate things and come up with theories about how we die if we fall into them. If you’re the sort of person who gets excited about maths and calculating these things for yourself, …our friends at Brilliant have put together a fantastic black hole quiz to help you get your head around them. Brilliant is a problem-solving website that teaches you to think like a scientist, by guiding you through the problems. They take concepts like these, break them up into bite-sized pieces, present clear thinking in each part, and then build back up to an interesting conclusion. If you visit Brilliant.org/nutshell or click the link in the description, you can sign up for free and learn all kinds of cool stuff. And as a bonus for Kurzgesagt viewers, the first 688 people will also get 20% off their annual membership. If you want to truly learn about black holes and support Kurzgesagt, this is one of the best ways to do it.

100 thoughts on “The Black Hole Bomb and Black Hole Civilizations

  1. If we did blow up the black hole, what happens to the black hole? Does it continue to be a black hole or does it dissipate and release all the mass inside it?

  2. 001¢ TNT = 🎒 (backpack has very small bomb)
    010¢ TNT = 🧺 (under the towels a small bomb)
    1$ TNT 🧨 = (dynamite)
    10$ TNT🚪 = (a some what big bomb fills this room)
    100$ TNT = 🌆 (a some what large bomb can destroy all these towers in one blow)
    1K$ TNT = 🌕 (a massive bomb that can destroy the moon)
    10K$ TNT = ☢️ (level 1 nuke)
    100K$ TNT = ☣️ (maximum level nuke)
    1M$ TNT = 🌎 (this TNT will destroy the world if set off)
    10M$ TNT ☀️ (this TNT will destroy the sun if set off)
    100M$ TNT 🌌 (this TNT will destroy the universe if set off)

    DISCLAIMER :
    This is not accurate in any way!

  3. So humans theoretically can take the most dangerous thing in the known universe AND TAKE ALL ITS STUFF 😀 humans are crazy

  4. Could we not just build our own stars?
    Or conceivably make something even denser than the black hole to fish all our stuff back out?

  5. Wait but what’s the point of making an energy source that lasts trillions of years when the sun will blow up in a few billions years. (assuming Jesus hasn’t come down yet, for you Christians)

  6. I REALLY like how you used the same cheat code from starcraft to give minerals and vespene, "show me the money" and turned it into "show me the energy" Nice little ode. But then you had to go and blow my mind with a RTS starcraft animation in the next bunch of frames. You are too good to us Kurzgasagt.

  7. Infinite energy: 2 vans taped together so the soles are facing each other. Add a generator and some other stuff and you can make thousands of them producing energy

  8. No, none of them spin millions of times per second. To spin millions of times per second, at as fast as a black hole can spin, it would require the black hole to be much smaller than the minimum mass black holes can form as.

  9. its actually good to make it explode, as with the materials of the black hole it COULD create stars, im not sure about it tho

  10. Did we all forget that mirrors can absorb a bit of light which is completely absorbed in a few nanoseconds? Ideal mirrors cannot exist

  11. So black holes spin cause they be like "yo collapsing star girl I like ya angular momentum ima hit you up we gon spin forever!" Edit: and then he got her a ringularity?

  12. Does this really work though? Doesn't time move slower as you approach the black hole? From our point of view at a safe distance… Would we ever experience the rocket actually entering it?

  13. When God wants to kill and ant he gives it wings. Our brains=wings=end. In universal time we have not had our brains for more than a micro second. lights out.

  14. I dislike as how you put the purple stuff rotating around it as the event horizon
    The event horizong would be the black part

  15. I have a question for you: is possible estract energy from the dark energy (the energy that makes the universe expand)? If it is possible the civilitation will have energy, without compromise, for all eternity!

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