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  • Black holes are one of the strangest things in existence.

  • They don’t seem to make any sense at all; where do they come from?

  • And what happens if you fall into one?

  • Stars are incredibly massive collections of mostly hydrogen atoms that collapse from enormous gas clouds under their own gravity.

  • In their core, nuclear fusion crushes hydrogen atoms into helium, releasing a tremendous amount of energy.

  • This energy, in the form of radiation, pushes against gravity, maintaining a delicate balance between the two forces.

  • As long as there is fusion in the core, a star remains stable enough.

  • But for stars with way more mass than our own Sun, the heat and pressure at the core allow them to fuse heavier elements, until they reach iron.

  • Unlike all the elements that went before, the fusion process that creates iron doesn’t generate any energy.

  • Iron builds up at the center of the star until it reaches a critical amount, and the balance between radiation and gravity is suddenly broken.

  • The core collapses.

  • Within a fraction of a second, the star implodes, moving at about a quarter of the speed of light, feeding even more mass into the core.

  • It’s at this very moment that all the heavier elements in the universe are created, as the star dies in a supernova explosion.

  • This produces either a neutron star or, if the star is massive enough, the entire mass of the core collapses into a black hole.

  • If you looked at a black hole, what you’d really be seeing is the event horizon.

  • Anything that crosses the event horizon needs to be travelling faster than the speed of light to escape.

  • In other words, it’s impossible.

  • So we just see a black sphere, reflecting nothing.

  • But if the event horizon is theblackpart, what is theholepart of the black hole?

  • The singularity.

  • Were not sure what it is exactly.

  • A singularity may be infinitely dense, meaning all its mass is concentrated into a single point in space with no surface or volume.

  • Or something completely different.

  • Right now, we just don’t know.

  • It’s like a dividing by zero error.

  • By the way, black holes do not suck things up like a vacuum cleaner.

  • If we were to swap the Sun for an equally massive black hole, nothing much would change for Earth, except that we would freeze to death, of course.

  • What would happen to you if you fell into a black hole?

  • The experience of time is different around black holes.

  • From the outside, you seem to slow down as you approach the event horizon, so time passes slower for you.

  • At some point, you would appear to freeze in time, slowly turn red, and disappear.

  • While from your perspective, you can watch the rest of the universe in fast-forward, kind of like seeing into the future.

  • Right now, we don’t know what happens next, but we think it could be one of two things.

  • One: you die a quick death.

  • A black hole curves space so much that once you cross the event horizon there is only one possible direction.

  • You can take this literally: inside the event horizon, you can only go in one direction.

  • It’s like being in a really tight alley that closes behind you after each step.

  • The mass of a black hole is so concentrated, at some point, even tiny distances of a few centimeters would mean that gravity acts with millions of times more force on different parts of your body.

  • Your cells get torn apart as your body stretches more and more, until youre a hot stream of plasma one atom wide.

  • Two: you die a very quick death.

  • Very soon after you cross the event horizon, you would hit a fire wall and be terminated in an instant.

  • Neither of these options are particularly pleasant.

  • How soon you would die depends on the mass of the black hole.

  • A smaller black hole would kill you before you even entered its event horizon, while you probably could travel inside a supermassive black hole for quite a while.

  • As a rule of thumb, the further away from the singularity you are, the longer you live.

  • Black holes come in different sizes.

  • There are stellar-mass black holes with a few times the mass of the Sun and the diameter of an asteroid.

  • And then there are the supermassive black holes, which are found at the heart of every galaxy and have been feeding for billions of years.

  • Currently, the largest supermassive black hole known is S5 0014+81, forty billion times the mass of our Sun.

  • It is 236.7 billion kilometers in diameter, which is 47 times the distance from the Sun to Pluto.

  • As powerful as black holes are, they will eventually evaporate through a process called Hawking radiation.

  • To understand how this works, we have to look at empty space.

  • Empty space is not really empty, but filled with virtual particles popping into existence and annihilating each other again.

  • When this happens right on the edge of a black hole, one of the virtual particles will be drawn into the black hole, and the other will escape and become a real particle.

  • So the black hole is losing energy.

  • This happens incredibly slowly at first, and gets faster as the black hole becomes smaller.

  • When it arrives at the mass of a large asteroid, it’s radiating at room temperature.

  • When it has the mass of a mountain, it radiates at about the heat of our Sun.

  • And in the last second of its life, the black hole radiates away with the energy of billions of nuclear bombs in a huge explosion.

  • But this process is incredibly slow.

  • The biggest black holes we know might take up to a googol years to evaporate.

  • Nobody will be around to witness it.

  • The universe will have become uninhabitable long before then.

  • This is not the end of our story; there are loads more interesting ideas about black holes.

  • Well explore them in part 2.

  • A big thanks to Fraser Cain for help with this video.

  • By the way, weve made some Kurzgesagt wallpapers in 4K for different screen sizes;

  • you can get them on our Patreon page, which also helps us to make more videos.

  • Like this December, the first month ever with three videos!

  • Subtitles by the community

Black holes are one of the strangest things in existence.

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Black Holes Explained – From Birth to Death

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    mommy posted on 2021/06/06
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