Black Holes: The Universe’s Ultimate Powerhouses
You know how black holes are like, the most powerful things in the universe? They’re so strong they can rip whole stars into pieces the size of atoms. That’s already pretty scary, right? Well, they actually have an even more powerful and dark property: they might actually delete the universe itself.
Black Holes in a Nutshell
So, how do these things even form? A black hole appears when an extraordinary amount of matter gets squeezed into a tiny space. Right at their center, the gravity is almost infinitely strong. Anything that gets too close gets ripped into its elementary particles. Not even light can escape from black holes, which is why we see them as perfectly black spheres.
If you were to fall into one, nothing really bad would happen until after you crossed its outer edge. This border is called the event horizon.
You can picture this like you’re swimming in a river that’s heading towards a giant waterfall. As you float along, maybe you don’t even notice it at first, but the current starts getting faster and faster. You could still swim back to safety until, without even realizing it, you cross the point of no return. Once you’re past that point, it doesn’t matter how fast you paddle; the current is just going to pull you down to certain death. Nothing can escape a black hole’s waterfall once it gets too close.
This border, the event horizon, completely separates black holes from the rest of the universe. We can’t get into them unless we’re okay with never coming back. Because of this, there’s no way of really telling what’s going on inside a black hole. But we do have some thoughts about what happens right at their very edges.
Black Hole Evaporation: Hawking Radiation
Here’s a weird part: black holes don’t just sit there forever. They actually radiate their mass away. Think of it like a hot pot on a stove slowly losing its water as steam. This process is called Hawking radiation.
Black holes are constantly losing an extremely tiny amount of their mass this way. It’s an unbelievably slow process. For example, a black hole with the same mass as our sun would take a mind-boggling 10,000 billion billion billion billion billion billion years to lose just 0.0000001% of its mass.
But here’s the thing: this is happening constantly and unstoppably. And as it goes on, this evaporation process actually speeds up more and more. Way, way in the future, long after the last star in the universe has died (trillions of years from now), black holes will become tinier and tinier until they finally evaporate and disappear completely. They’ll leave behind nothing but a little bit of radiation.
The Information Problem
Now, this evaporation is a problem. When black holes disappear, they might be deleting something absolutely fundamental: information.
What is Information?
Okay, so what is information in this context? It’s not something you can hold. It’s usually understood as a property of how particles are arranged.
What does that mean? Well, imagine you have a bunch of carbon atoms. Arrange them one way, and you get coal. Arrange those same carbon atoms a different way, and you get a diamond. The atoms are the same; what’s different is the information about how they’re put together.
Let’s make it more complicated. Add in a few more types of atoms. Arrange them one way, and you get a banana. Change the arrangement of those same atoms, and you get a squirrel.
The basic building blocks of everything in the universe are the same. They don’t care if they’re part of a bird, a rock, or your morning coffee. Without information, everything in the universe would be exactly the same.
Information is Indestructible (According to Physics)
According to the theory of quantum mechanics, information is indestructible. It can change shape, but it can never be lost.
Think about burning a piece of paper. You end up with ash. That ash will never become paper again, not on its own. But, if you were somehow able to carefully collect every single carbon atom in the ash, and also measured the exact properties of the smoke and heat that came off the fire, you could, in theory, reconstruct the paper. The information about the paper is still in the universe. It’s not lost; it’s just really, really hard to read.
Hypothetically, if you could somehow measure every single atom, every particle, and every wave of radiation in the universe, you could see and track every single bit of information that exists. You could, in theory, see the entire history of the universe, right back to the Big Bang.
The Information Paradox
And here’s where black holes trip us up. Information is what tells us how things are different from each other and what used to be what. Black holes seem to do the opposite. They take different things and make them the same. They destroy information.
This creates the information paradox, and it’s a serious problem for physics.
It’s absolutely fundamental for all our laws of physics that information can never be lost. Think about it: how could physics work if things could just wink out of existence or appear from nowhere without leaving a trace? Existing or not existing – you need clarity. Without information being preserved, everything becomes relative, and when it comes to understanding reality, we need absolutes.
How Could We Solve This Paradox?
Scientists have come up with a few possibilities:
-
Information is lost.
- It’s gone irretrievably and forever.
- This means we have to throw out all our current laws of physics. That’s a lot of stuff that has worked very well so far! We’d have to start completely from scratch.
- What those new laws would look like, or what it would mean for us, nobody knows.
- This is a little frightening, but also kind of exciting if you think about the possibilities.
-
Information is hidden.
- Maybe when a black hole disappears, a little part of it splits off and forms a baby universe.
- The information would be transferred into this new, weird place.
- We would never be able to observe or interact with it.
- But, technically, the information would not be lost. It’s kind of like having a broken hard drive with all your family photos on it. It’s nice that they haven’t been deleted, but it’s not very helpful if you can never access them.
- Or maybe black holes don’t disappear completely after they evaporate. Maybe a tiny piece is left behind, like an “information diamond”. This sounds a bit like a clown car filled with an infinite amount of information clowns – lots of stuff packed into a tiny space.
-
Information is safe after all.
- It’s not lost or hidden.
- Maybe we’ve just been looking at this whole thing the wrong way.
- We know black holes trap information and might delete it later, but we never really thought about what they do with it in the meantime.
- So, where do black holes store their information?
Where Black Holes Store Information: Cosmic Housekeeping
Let’s try to understand that last possibility with an analogy. Imagine we’re creating a black hole out of dirty laundry.
First, we fill up a room with laundry baskets. The more laundry (or information) you want to store, the more baskets you put in the room. Eventually, every single basket is full, and the room is completely stacked. You can’t fit a single extra sock in there. The room is at maximum capacity.
But if we somehow managed to squeeze that extra sock in using a lot of energy and violence, the room would actually collapse in on itself and form a black hole.
Now, you’d think the capacity of the room (or the space inside the black hole) hasn’t changed, and it’s still impossible to fit more stuff or information in. But what actually happens if we throw more laundry (more information) into it?
It turns out, the room itself (the black hole) gets a little bit bigger just to make space for the new information! Specifically, a black hole grows its surface by a tiny pixel for each bit of information we throw into it. In a nutshell: more information means more surface area.
The information isn’t stored inside the black hole; it gets painted on the surface, on the event horizon. This is similar to throwing a stone into a pond. After the stone sinks to the bottom, you can’t see it anymore, but you can definitely tell that something went in by the ripples it makes on the surface of the pond. The information about the stone is now reflected in the surface ripples.
This idea is mind-blowing: even the smallest black hole can store more information on its surface than all the data ever produced in human history! They can do this because they store information in a type of pixel that is unbelievably tiny. Black holes are basically the ultimate hard drive.
This is a bit like taking a paperback book and turning it into an e-book. They look completely different, but their content is the same. It’s just encoded and memorized in another way. A black hole swallowing stars and planets is kind of like transferring a whole library onto an e-reader.
This proposed solution is called the holographic principle. But if it’s correct, it means everything we thought we knew about the universe might be wrong in a fundamental way.
The Universe is a Hologram
If information is actually stored on the boundary (the surface) of a black hole, then the Hawking radiation that comes off the surface has a chance of learning about the information encoded there. This means the radiation can carry that information away as the black hole evaporates.
So, the information isn’t lost when black holes fade away! We do not need to redo physics. The information paradox is resolved.
But, like we said, we still have to change our understanding of reality in a pretty fundamental way. If everything that falls into a black hole is stored on its event horizon, that basically means that three-dimensional stuff is encoded on a flat surface. We have a name for that kind of thing: a hologram.
A hologram is like a 3D photo – it’s a flat piece of plastic (a 2D surface) that somehow encodes a three-dimensional image. A black hole is like a hologram because everything inside it is encoded on its event horizon (its surface).
Think about a person falling into a black hole. For them, inside the black hole, they would experience their usual three-dimensional life. But for us on the outside, they are essentially just flattened images on the surface of the black hole.
Now, here’s the consequence, and it’s pretty counterintuitive, so just stay with us for a moment. Black holes are extreme objects, sure, but they are still bound by the same rules as everything else in the universe. So, if this crazy duality between 2D information storage and 3D reality works for black holes, then maybe it might work for the whole universe, and yes, you in it.
Since a person inside a black hole wouldn’t realize that they’re encoded on a flat surface, maybe we share the same fate. You really might be stretched over a flat screen at the end of the universe.
The science behind this gets really complicated and weird. It involves things like “toy universes” scientists play with, string theory, and a lot of maths. We’ll probably talk about this more in another video.
Regardless of what the true nature of the universe actually is, we just know that it’s strange and complicated. And we have to do a lot more physics to truly understand it. But black holes, these incredibly powerful and mysterious objects, might just be the key to understanding the nature of reality itself.
Credits: This video was supported by the Swiss National Science Foundation. It was realized with the scientific advice of Alessandro Sfondrini.