What Is the Black Hole Information Paradox? The Problem with Black Hole Evaporation

Have you heard that black holes destroy any information that goes into them? Why is this such a big problem for physics?
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Team: Fraser Cain - @fcain
Jason Harmer - @jasoncharmer
Susie Murph - @susiemmurph
Brian Koberlein - @briankoberlein
Kevin Gill - @kevinmgill

Created by: Fraser Cain and Jason Harmer

Edited by: Chad Weber

Music: Left Spine Down - “X-Ray”
In my day, things were simple. Robot dogs had wheels and laser noses. School was uphill both ways. Unwanted children removed themselves from lawns, and we didn’t need those horrible electrified tentacle arms. The cut of my jib was completely beyond reproach. Nathan Fillion was the captain of the Serenity all day, every day. … And black holes were holes that were black. By that I mean black holes would compress matter and energy into an infinitely dense singularity, and didn’t create a seemingly insurmountable information paradox. Yep, those were the good ol’ days.

But those days are over. Now it’s all 50 shades of grey, with the laws of physics bending under other laws of physics. “Hashtag not my Christian”. What I’m talking about is the black hole information paradox.

First, let’s talk information. When physicists talk information, they’re on about the specific state of every single particle in the Universe: mass, position, spin, temperature, you name it. The fingerprint that uniquely identifies each one, and the probabilities for what they’re going to do in the Universe. You can change atoms, crush them together, but the quantum wave function that describes them must always be preserved.

Quantum physics allows you to run the whole Universe forwards and backwards, as long as you reverse everything in your math: charge, parity and time. Here’s the important part. The big brains tell us information must live on, no matter what. Think about it like energy. You can’t destroy energy, all you can do is transform it.

Now, the black hole recap. Naturally formed when the largest stars, those with more than 20 times the mass of the Sun, collapse violently and explode. Here the density of matter is so high, the escape velocity exceeds the speed of light. The fancy ones have a super-heated accretion disk of matter swirling around the black hole event horizon, where even light can be pulled into orbit.

Here, we get one of the strangest side effects from Relativity: time dilation. Imagine a clock falling towards a black hole, moving deeper into the gravity well. It would appear to slow as it got closer to the black hole, and eventually freeze at the edge of the event horizon. Photons from the clock would stretch out, and the color of the clock would redshift. Eventually, it fades away as the photons stretched out beyond what our eyes can detect.

If you could stare at the black hole for billions of years, you would see everything it ever collected, stuck to the outside like flypaper. You could point out the clock, the Titanic, the Ranger, and USS Cygnus, and theoretically, you could identify the quantum state of every single particle and photon that went into the black hole. Since they’re going to take an infinite length of time to disappear completely, everything’s fine.

Their information is preserved forever on the surface of the black hole. They’re all totally dead, but their information, their precious precious quantum information, is totally safe.

If you could unravel a black hole, you could get at all the quantum information describing everything the black hole ever consumed. And least, that’s how it was in the good old days.

But in 1975, Hawking dropped a bombshell. He realized black holes have a temperature, over vast periods of time, they would evaporate away until there was nothing left. releasing their mass and energy back into the Universe. Unsurprisingly known as Hawking Radiation.

[TheMGOkilla]

I love astronomy and the like, came here from Kurzgesagt, glad you were in the comments. You got me to check out the channel. Looking forward to more videos man.

[superawesomeboy]

The Black Hole Information Paradox would be an awesome band name

[Kingricky]

is it weird that it really bothers me that I'll never truly know how the universe works..

[christosvoskresye]

Q: What is the Black Hole Information Paradox?
A: I'm not sure. I wrote it down, but the notebook fell into a black hole.

[timmonapier]

Thanx to you Fraser for putting it simply enough for me to understand

[thebritishgeek]

Speaking of black holes. Can you have a binary system consisting of a black hole and a star, if so could planets in that system contain life?

[AkiRa]

So if matter and anti-matter annihilate each other, what happens with this "information"?

[rob]

Can we not create an artificial blackhole? Using a particle accelerator or some other technology. Even if it has to be done in space? So we can observe what happens to the information.

[unvergebeneid]

So what exactly happens with that event horizon wallpaper of accreted gas, spaceships and wall clocks while the black hole slowly evaporates away according to the theory? I assume the wavelength of light they reflect goes to infinity as the black hole comes closer to disappearing which takes care of the "I can see it, I can see it, I can ... poof, it's gone" effect that one would otherwise observe? How does the information slowly disappear though? Does it have something to do with the uncertainty principle? So the less energy the photons contain, the less information they contain, too? Or am I talking utter bullshit here?

[flaviogomes]

Inside a black hole there is gravity, matter and energy.

The event horizon of a black hole is the limit between the black hole and the space. When the matter reaches the event horizon it turns into energy. E=mc2.

[UnforgivingDemon]

I am curious to know that if someone were to theoretically fall into a black hole and survive past the event horizon(supermassive black hole), would they be completely engulfed by darkness and the view of the universe fade away behind them or will it appear that the event horizon continues to stand off at a distance even after passing it? What would someone see and what would it look like to fall past a black holes event horizon? Perhaps this would be a good topic for a future video?

[forgerulethemall]

If black holes have photons in orbit doesn't that mean that if you entered one of those orbits there'd be a flash of light as photons bounced off you? (well what ever is left of you after being so close to a black hole) If that's the case wouldn't it also mean that those orbiting photons would be completely invisible to the naked eye outside that orbit as no light ever actually reaches you?

[dishserve]

I am really confused here, the black hole information paradox is because of the time dilation effect as you say or is it because all the quantum states devolve into the same state thus violating the Copenhagen principle?

[EmdrGreg]

I'm not a scientist. I'm wondering though about entanglement. If one particle of an entangled pair falls into a black hole and the other is well outside of it, is not the quantum information saved even if it is lost for the one in the black hole? Maybe every particle that exists is entangled with at least one other particle somewhere. On the other hand, I just don't get the importance of saving the wave function information of a given particle when it's essentially the same as the wave function information for every other particle that exists-- anywhere. I know I am missing layer upon layer of subtle and complex knowledge-- just curious.

[unvergebeneid]

Ok, I can see how inverting charges and stuff would be the same as reversing time. But how does gravity fit into this picture? How do you make two particles that usually attract each other gravitationally suddenly repel each other?

[shigiz]

2:48 THE RANGER FROM INTERSTELLAR I LOVE U FRASER CAIN

[ProperLogicalDebate]

What if there was a very long strong rod that moved straight in with an engine at the leading end with sufficient thrust & fuel to change the velocity of the moving rod than information can come out in the form of the rod slowing down at times as the engine is turned on & off like a Morse Code Key? Nothing comes out except for the information of how fast the rod is going in. The same might apply to a rope that can swing from the inside but might be affected on the outside. It can swing in 4 directions, Dit, Dah, Space, Double Space.

[michaelhernandez]

(Topic Request) Can galactic magnetic fields explain the galactic rotational speed observations? You know, the observations that led instead to the dark matter hypotheses. Or have you already explored this idea?

[marufhashem]

I am having a difficult time grasping this concept of "Information". Is information made of matter i.e. particles ? If so, then how do we lose it when the black hole evaporates?

[parkerflop]

Best video of yours I have watched and definitely a better explanation of black holes then every single other video of black holes that I watched.