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  • Scientists work on the boundaries of the unknown, where every new piece of knowledge forms a path into a void of uncertainty.

  • And nothing is more uncertain, or potentially enlightening, than a paradox.

  • Throughout history, paradoxes have threatened to undermine everything we know, and just as often, they've reshaped our understanding of the world.

  • Today, one of the biggest paradoxes in the universe threatens to unravel the fields of general relativity and quantum mechanics: the black hole information paradox.

  • To understand this paradox, we first need to define what we mean by "information."

  • Typically, the information we talk about is visible to the naked eye.

  • For example, this kind of information tells us that an apple is red, round, and shiny.

  • But physicists are more concerned with quantum information.

  • This refers to the quantum properties of all the particles that make up that apple, such as their position, velocity, and spin.

  • Every object in the Universe is composed of particles with unique quantum properties.

  • This idea is evoked most significantly in a vital law of physics: "the total amount of quantum information in the Universe must be conserved".

  • Even if you destroy an object beyond recognition, its quantum information is never permanently deleted.

  • And theoretically, knowledge of that information would allow us to recreate the object from its particle components.

  • Conservation of information isn't just an arbitrary rule, but a mathematical necessity, upon which much of modern science is built.

  • But around black holes, those foundations get shaken.

  • When an apple enters a black hole, it seems as though it leaves the Universe, and all its quantum information becomes irretrievably lost.

  • However, this doesn't immediately break the laws of physics.

  • The information is out of sight, but it might still exist within the black hole's mysterious void.

  • Alternatively, some theories suggest that information doesn't even make it inside the black hole at all.

  • Seen from outside, it's as if the apple's quantum information is encoded on the surface layer of the black hole, called the event horizon.

  • As the black hole's mass increases, the surface of the event horizon increases as well.

  • So it's possible that as a black hole swallows an object, it also grows large enough to conserve the object's quantum information.

  • But whether information is conserved inside the black hole or on its surface, the laws of physics remain intactuntil you account for Hawking radiation.

  • Discovered by Stephen Hawking in 1974, this phenomenon shows that black holes are gradually evaporating.

  • Over incredibly long periods of time black holes lose mass as they shed particles away from their event horizons.

  • Critically, it seems as though the evaporating particles are unrelated to the information the black hole encodes, suggesting that a black hole and all the quantum information it contains could be completely erased.

  • Does that quantum information truly disappear?

  • If not, where does it go?

  • While the evaporation process would take an incredibly long time, the questions it raises for physics are far more urgent.

  • The destruction of information would force us to rewrite some of our most fundamental scientific paradigms.

  • But fortunately, in science, every paradox is an opportunity for new discoveries.

  • Researchers are investigating a broad range of possible solutions to the information paradox.

  • Some have theorized that information actually is encoded in the escaping radiation, in some way we can't yet understand.

  • Others have suggested the paradox is just a misunderstanding of how general relativity and quantum field theory interact.

  • Respectively, these two theories describe the largest and smallest physical phenomena, and they're notoriously difficult to combine.

  • Some researchers argue that a solution to this and many other paradoxes will come naturally with a "unified theory of everything."

  • But perhaps the most mind-bending theory to come from exploring this paradox is the holographic principle".

  • Expanding on the idea that the 2D surface of an event horizon can store quantum information, this principle suggests that the very boundary of the observable universe is also a 2D surface encoded with information about real, 3D objects.

  • If this is true, it's possible that reality as we know it is just a holographic projection of that information.

  • If proven, any of these theories would open up new questions to explore, while still preserving our current models of the universe.

  • But it's also possible that those models are wrong! Either way, this paradox has already helped us take another step into the unknown.

  • Ever wonder if a black hole could destroy us?

  • Or we could destroy a black hole?

  • Cast your lot for or against humanity by watching one of these videos next.

Scientists work on the boundaries of the unknown, where every new piece of knowledge forms a path into a void of uncertainty.

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B2 US TED-Ed quantum information black hole hole paradox

Hawking's black hole paradox explained - Fabio Pacucci

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    Seraya posted on 2020/02/14
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