BLACK HOLE INFORMATION PARADOX
Hello hello today we'll be talking all about one of the most famous theories that has graced the field of cosmology aka the Black Hole Information Paradox! #scicomm
lets goooo! (1/25)

For starters the term was coined after Stephen Hawking famously shed new light on a possible way of how Black holes work in 1974, the regions of inescapable gravity with centers where all known laws of physics ceased to work. (2/25)

Two of the best theories in physics paint a very contradictory picture of these objects and an explanation of why they work the way they do aka the Theory of Relativity and Quantum Mechanics. (3/25)

General theory of relativity explains that these objects arise when the density of matter in an area of spacetime becomes too concentrated and collapses all its material into a pinpointed central area. The gravity is strong here that not even light can escape their grip. (4/25)

The area which acts as the crossing point of the "area of no coming back" is called an Event Horizon and acts as a supposed one way membrane. All seems well and good (ish) for now. (5/25)

But adding quantum mechanics to this mixture, aka the theory of the most fundamental particles, the story changes. In 1974, Stephen Hawking presented a hypothesis that changed the way we look at blackholes and left a riddle that might lead to the theory of quantum gravity. (6/25)

Now black holes are thought of as static objects, unchanging and defined only by their mass, charge and spin. But Hawking stated in his paper that black holes actually were "evolving engines that had a temperature, emitted radiation and evaporated." pretty weird huh? (7/25)

A small explanation before we proceed: what we call as "dark" or "black" in the fields of cosmology does not mean that the object is black. It simply means that the object is unobservable/cannot be seen directly. aka Dark matter and Dark Energy. Or our very own blackholes. (8/25)

Coming back to that evaporation bit. WHATT? Okay so Hawking said that quantum fluctuations near the blackhole i.e the formation of matter-antimatter pairs near the event horizon of a blackhole causes one of them to escape to infinity... (9/25)

...and the antimatter to be trapped in the event horizon of a black hole. Now we all know antimatter. Matter w negative energy. This very particle accumulation would cause instability in the blackhole, reduce it mass till it disappears into nothingness. (10/25)

So far so good, ya know disappearing blackholes go poof but what makes this a paradox? What is this blackhole up to? (11/25)

Now we all know the second law of thermodynamics aka the entropy of a closed system or an isolated system NEVER decreases over time. Period. Entropy can never be destroyed. (12/25)

The universe can be thought of as a closed system and ideally this law should hold but it seems like it doesn't. Now blackholes were thought to have zero entropy, they remained constant structures with the entropy never decreasing. (13/25)

This hypotheses was presented by John Wheeler, an American physicist who imagined that an object falling into a black hole would asymptomatically approach the event horizon, turn red due to redshift & be the prey of a relativistic time dilation (ya know, normal stuff) (14/25)

and like every good guard, the blackhole would keep the "information" from whatever fell in it encoded on its surface. That is, a blackhole keeps note of everything about the object that falls in it, be it the information in a pizza slice or an elephant. (15/25)

Now doing this made sure that the natural place for the entropy of a blackhole to be is on its surface aka the event horizon. All of a sudden these structures had a massive entropy formed by huge amounts of quantum information encoded on its surface. (16/25)

Now comes in the Hawking radiation. The emission of energy means that Einstein's famous e=mc² is being put to work. Meaning that if the black hole is losing mass, the energy, too, is coming from it. What is the energy? (17/25)

The energy is actually the information that it had collected over millenia getting destroyed. Until in the distant future, it evaporates in a brilliant flash of light. Going out dramatically are we, blackholes? (18/25)

This is all fantastic but you see the obvious problem? The radiation is blackbody and hence same for each blackhole, irregardless of the information imprinted on the event horizon. (19/25)

This is in direct contradiction to the fact that entropy can never change for an isolated system. Liouvilles theorem was violated. In addition quantum mechanics explicitly states that information can never be destroyed. well well well blackholes, you cheeky bastards... (20/25)

This basically means that all the information EVER on the surface of a blackhole leaves no trace in the observable universe when the blackhole evaporates. Now if this is happening then either information is truly destroyed when a blackhole evaporates or (21/25)

instead there are new laws of physics that we're unaware of when it comes to governing the blackhole evaporation. We really don't know for sure. (22/25)

Countless famed academics like John Preskill, Kip Thorne, Gerald't Hoofy and Leonard Susskind have tried to find why blackholes work the way they do but this paradox still remains unsolved. (23/25)

A hopeful future in this mess is that if this enigmatic working of blackholes is understood, we could either bridge the gap between QM and Relativity or find a new branch of physics preciously unknown. (24/25)

But all in all, Hawking truly left us with the most beautiful paradox ever and hopefully it's workings might finally be understood in the future. Who knows? It could even be you who does that.(25/25. end)