The Black Hole Bomb and Black Hole Civilizations

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 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. Humans are not able to store carbon dioxide in the atmosphere and yet you talking about having mirrors around a black hole!!

  2. Theoretically, could there be an incredibly massive planet trying to collapse itself but the only thing keeping it from doing so is because there’s 2 black holes flanking it that have enough of a pull to keep the planet stable?

  3. I'm srry but my brain can't understand, like I rally want to but its impossible, the hardest ice ever thought is making a guess on a multiple choice question for a chemistry test

  4. What if the end result of evolution is a race that controls all the energy in its galaxy and then eventually it's own universe and then it just creates or resets a new universe with the energy it's collected. Is that god?

  5. Interesting I think if there will be a machine in the future can use the Black hole to help humanity to destroy any planet that we want

  6. "Black holes are spinning"….. 'because of angular momentum of the star they were born of"… holes are spinning except when they are not spinning"….what now ?

  7. That Black Hole bomb sounds like the plot to a Sci-Fi Supervillain game. "We have to vent the Superradiant-scattering energy, or the system will be vaporized!"
    "I'm afraid I can't let you do that."

  8. After watching a Kurzgesagt video, my brain wants to leave my skull telling me that "it's time we see other people" and shit! I don't get that..!! In other words, I can't totally blame him because I've been causing him lots of grief and stress lately!!

  9. humans: "wow that monster in the movie was scary!"
    also humans: don't see the danger of black holes
    birds:"how to steal energy from a monster"

  10. My intuition kinda goes haywire when listening to this…

    There's so much wrong about this, I don't even know where to start lmao.

  11. Does anyone knows why the Channel Name is "Kurzgesagt" ? I mean, another language is not the best idea, I am sure that the most people can not Pronounce "Kurzgesagt" right. 🙂

    And why a German word? Is it the best word or what? 😀

  12. “Blackholes are the largest collection of pure violent energy in the universe … I mean, we think … we don’t know.”

  13. I see a lot of people talking about nukes, to clarify, this wouldn't be a nuke. it would be a SUPERNOVA which is pretty big. big enough to destroy a solar system. 100 billion nukes couldn't even put a crack in a planet. but, if like kurzgasagt was saying, we used the supermassive black hole in the center of the milky way, it would be trillions of times bigger than a supernova, bigger that a hypernova, it would be a Galaxy destroying, physics breaking, unbelievably cool, Übernova, if you will. so yeah that would be pretty big.

  14. "Here’s an infinite energy source to maintain your civilization for eternity"

    "Trillions of years"

    Yeah trillions of years is a long time, but it's neither infinite nor eternity.

  15. Kurzgesagt: You can take a black hole and turn it into an infinite energy source.
    America: ok
    Kurzgesagt: Or you can blow it up.

  16. Well black wholes can spew out stuff and here's a theory I have a black hole that inch contained everything else's it swallloeda. Old universe black holes spew out mass every so often in a beam the mass in the black whole bounce and speed up infinitely maybye even faster then light what if the mass got extremly fast and all the black holes energy or at least most of it faded away and it coudlent hold its mass anymore it then lost its mass and bassicly exploded this was the start of the newest universe it's just athery and not a great one but still a theory

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