Are we all living in an enormous black hole?

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1:08Hello, it's Meredith. There are some wicked, exciting, unexplainable projects in the works. We are really looking forward to sharing them with you all. And so soon, we're almost there. But in the meantime, we are revisiting some of our favorite unexplainable episodes of all time. And today, I want to share an episode from Noam from 2024 that made me think about the universe in a totally new way. When scientists look out into the stars, there's an edge, a horizon that they just can't see beyond. What if that edge is the boundary of an enormous black hole? What if our universe is inside of an enormous black hole?

2:01Here's Noam. A couple months ago, I was watching a video and I heard this question that I didn't even know was possible.

2:12James Beacham:Do we live inside an enormous black hole? I was like, yeah, no, it's not possible. Like, that's a strange question. So I looked up the bio of this guy, James Beecham, and he's a particle physicist at the Large Hadron Collider at CERN. So, yeah, okay. I kept watching. It turns out that the mathematics of the interior of a black hole is almost identical to the mathematics of the exterior of the black hole. At this point, I was legitimately curious. So I called him up. I find myself drawn toward all of these kinds of, just the edge of our human knowledge, and I want to step just beyond it to see what's there.

2:59James Beacham:It's not a crazy step. It's just a very small step. What I love about talking to James is just how sincerely he takes this question and how excited he is about the even bigger questions it opens up. Like, if we do live inside an enormous black hole. Does that mean that our universe was birthed from a black hole in another universe? And does that mean that the black holes in our universe are little seeds of baby universes in another multiverse situation? So, I'm Noam Hassenfeld, and this week on Unexplainable, is our entire universe inside a black hole?

3:56Okay, so before we dive into the black hole, let me just give you a little heads up. James, this particle physicist at CERN, he's really good at posing fascinating questions. He's also pretty good at not really answering them, which means there's going to be a lot more speculation than explanation coming up, even more questions than normal for our show. Let's just say it's going to get weird, but it's going to be a lot of fun. So to start, here's a little Gravity 101. What we observe as gravity, so a ball falling toward the ground or the moon orbiting around the Earth, it's not that the Earth is tugging on those things.

4:41It's that the mass of Earth is warping the fabric of the universe. It's essentially creating a kind of crater in space.

4:50James Beacham:Gravity arises because the presence of stuff within a certain volume of space creates a kind of sinkhole in space itself. This is where we get to black holes. Because if you get enough mass in a small enough area, space starts to warp dramatically. The sinkhole gets so steep that nothing can escape it, even light. You can think about a black hole in space like an extremely strong water drain. If you're a fish in the water, you stay far enough away from the drain, you wouldn't even notice that it's there. But if you get close enough to the drain, at some point, the water will be flowing inward faster than you could ever possibly swim.

5:29James Beacham:That's like light. If I am inside the black hole and I turn on a flashlight, that light signal is still going to light speed. But if this pocket of space is being sucked toward the center of the black hole faster than the speed of light, it's never going to be able to get outside of the black hole. And this incredibly strong gravity doesn't just affect light. It affects everything. Like, if you were falling into a small black hole and you made it past the edge, what's called the event horizon, space would be warped so dramatically that your feet would be pulled in faster than your head. And it would probably just start to stretch you out.

6:07James Beacham:You would probably get stretched into spaghetti.

6:16That's basically what I knew before speaking to James. It's the way you'll often see black holes presented in movies like Interstellar or High Life or Star Trek. Black holes suck in light. They stretch things out. They're not exactly fun places to be. But then James went galaxy brain.

6:34James Beacham:For a large enough black hole, you wouldn't even notice at all. I could, in fact, just kind of sit there and I would be fine. I could hang around quite a long time, probably even indefinitely within this enormous black hole. So you're saying in a large enough black hole, it could be potentially possible for people to just hang out and be okay? Yeah, so, you know, you can kind of just do the calculation yourself If you want to, you can calculate what the gravitational pull would be on your feet versus your head as you go into different sizes of black holes. And you can see that for smaller ones, yeah, it would be quite an extreme thing and you get stretched out.

7:07James Beacham:And for larger ones, if it's an extremely large black hole, you wouldn't even notice at all. How large a black hole are we talking? Yeah, okay. So you can use the black hole equation. And if you want to, it'll tell you for some given amount of mass, how small of a volume you'd have to pack it in to make a black hole. That's pretty straightforward. So, for example, if I wanted to make a black hole out of the entire Earth, I need to pack it into a volume about the size of a blueberry. And if you have a blueberry-sized black hole, your entire body getting sucked into that would basically just be crushed and stretched into oblivion, for sure.

7:38James Beacham:Right. Bad. Because, you know, just think about it in a very, very bad way. Catastrophically, you know, I mean, honestly, from a kind of epic scientific way, that's a pretty good way to go. But, like, it would also be quite bad. Very bad. But if I wanted to make the black hole out of the entire sun, I would have to pack it into a volume that's around kind of the center part of London. And that's also going to be extreme curvature and extreme flow of space as you get closer to this thing. So if you happen to be in Trafalgar Square, when the sun gets packed into London, you would also get sucked in and killed.

8:08James Beacham:But then take that to its logical conclusion. So, for example, my astronomer friends are very, very good at calculating what the total mass of the observable universe is. I put it into the equation that says how tightly I would have to pack that. You'd think it's something like the size of a galaxy or something like that, right? Right. But it turns out that the amount of stuff in the universe, the observable universe, would need to be packed into a volume that is already larger than the observable universe. That's weird. If you say that's weird, it's because it is. Yeah. When I first came across this calculation, I think just like any other physicist, the first time you come across this calculation, you think, well, that can't be right.

8:48James Beacham:And so you go and start looking at it yourself and you do it yourself. And it's absolutely true. So you start to think, okay, well, maybe my astronomer friends, they made an error. Maybe the mass of the universe is not really what they think it is. Maybe they got it off by half, right? I mean, that's a huge error, right? So maybe the total mass of the observable universe is only half of what it is. But it turns out you would still need to pack the entire universe into a volume that's already larger than what it is itself. So then you take this to its logical conclusion, and you might ask the question, is our entire observable universe inside an enormous black hole?

9:25James Beacham:And that's a bit disquieting. Are you aware how that sounds? Completely aware. And so at first, that doesn't make much sense because, you know, again, I thought black holes were these enormous objects that are kind of voraciously sucking in things and spaghettification and stretching everything about it. And like, if I look at the moon, it's not being voraciously sucked and pulled in one direction, right? Or being spaghettified, right? So how is it possible that I look up into space, I look around me that I could actually be inside of a black hole? Well, think about what your experience would be like if you were inside of an enormous black hole.

10:00James Beacham:You can see stuff around you. You can still exist in your kind of local patch of space, but there will be sort of a thing in the distance, a so-called horizon. What is a horizon? A horizon is something you can never get to. That's what a horizon is, right? It's something in the distance. If you ever got to the horizon, it wouldn't be the horizon anymore. Right. So you'd see this thing inside your black hole that is this horizon beyond which you can't see anything. But this event horizon is also always slowly growing. We know the black holes are sucking things in all the time. They're getting radiation.

10:33James Beacham:They're getting particles and things like this. So more stuff is coming into view at all times. So this is what your experience would be like inside an enormous black hole. Now, imagine you right now on Spaceship Earth. We look up into the sky. It seems fine. It seems kind of placid. Everything's kind of, you know, sitting there, you know, very serenely. But in the distance, there's an edge beyond which we cannot see. And this is the cosmological horizon beyond which there is stuff. There has to be. But it has sent a light signal to us that hasn't had time to get to us yet. And this is also slowly growing, too.

11:07James Beacham:Right. After a certain amount of time, stuff will start to come into this cosmological horizon, and our observable universe will grow. But as it stands now, you're just kind of sitting here, and with our best telescopes, we're seeing this very edge of the universe slowly getting larger.

11:28But black holes suck everything into the center, right? Like if we were in a huge black hole, there would be a center somewhere, right?

11:36James Beacham:Right. It is true that at the center of a black hole, there's some kind of weird little thing that we don't understand that simply doesn't make any sense, known as a singularity. Inside the black hole, you would be falling toward the center of this black hole, this kind of like point of infinite density. So if that's the case, that we are in an enormous black hole, where in the universe is the singularity of our black hole? Exactly. The closest thing that we know of in the entire history of our universe that has existed, that is close to a singularity, is the Big Bang. Okay. So maybe our universe, as it exists now, satisfies this notion that it could potentially be inside of an enormous black hole because our universe did originate from something that's very similar to a singularity, which was the Big Bang.

12:20James Beacham:We had a kind of singularity-like object that was the kind of seed to our universe. And again, it's a good question where when we say the Big Bang happened 13.8 billion years ago, you could ask the question, where did the Big Bang happen? The Big Bang happened everywhere. So really the singularity in our universe, if we live inside an enormous black hole, the singularity happened everywhere at once. The singularity is all of us. It's everything. The singularity is everything. That's insane. Yeah. Yeah. So if I can see if I'm understanding this, it's not where is the singularity, it's like when is the singularity almost?

13:02James Beacham:Yeah, that's a good way to think about it. And the answer to all of this is, again, you have to keep in mind that when we're talking about the curvature of space, we're also talking about the curvature of time. Because space and time are two parts of the same thing, which is space-time. You have to think about them as related. And so if we live inside of a black hole, and if—these are the big ifs. Big ifs. If we live inside of a black hole, and if this is a meaningful statement to make, then where is the singularity inside of our enormous universe-sized black hole? And the answer is that it's either nowhere or everywhere.

13:34James Beacham:And these are kind of the same statement because our Big Bang happened everywhere at once. Oh, man. But there's an interesting corollary to this. Hit me. Somebody out there right now is thinking, James, you're a crazy person because we have black holes inside our universe right now. How is it possible that you can have black holes inside of a black hole? Yes, how? That's a very good question. Is it possible? And again, this is where we start to go from the kind of edges of science and starting to step over into the kind of like speculative part, not in a crazy way, but just stepping that way. Is it possible that our universe was birthed from a singularity of a black hole in another universe?

14:12James Beacham:And does that mean that the black holes in our universe are little seeds of other universes in a multiverse itself? So the idea there is that in our universe, there could be infinite other universes that are the black holes in our universe. Correct. Okay. And when I say correct, I mean, it's a hypothetical possibility. You know, I mean, at the end of the day, I might sound like a theorist, but in fact, I'm an experimentalist. And so I need an experiment to be able to demonstrate to me whether or not these things are true. Okay. And right now we don't actually have any way to possibly test these hypotheses.

14:51James Beacham:I would never be so hubristic to foreclose the idea that somebody in the future might come up with a way to test this, but right now we can't. Dang. No one's ever gone to a black hole. And if you did go inside of a black hole, like we know, it's a one-way trip. However, we should start with what we know and what we don't know. What is it we don't know? We have no idea what's actually going on inside of a black hole. So the first thing we should do is we should try to maybe study a black hole up close. So either we wait for a very long time to have, you know, interstellar space travel. But another way is if we could make black holes in a laboratory.

15:24You can make them?

15:25James Beacham:Well, if we were able to make miniature black holes in a laboratory, that would teach us a lot.

15:34Coming up in a minute, how to make a black hole.

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16:55Sucked into a bagel. Okay, we've been on this long, spaghettified journey together, so let's just get our bearings for a second. It's possible we might be living in an enormous black hole, because in a black hole there'd be this edge we can't see past that would always be getting further away, which sounds a lot like what we see from Earth right now. We just tend to see it as our universe getting bigger. But we can't prove this one way or the other because we don't really know that much about black holes to begin with. And we can't go out and study one up close because the closest confirmed black hole is just way too far away.

17:40So James Beecham, this particle physicist at CERN, he's got a different idea. If we want to study a black hole, we might be able to make one. Which leads me to a question I admit, I never thought I'd be asking a physicist. Wait, wait, how do you make a black hole?

18:00James Beacham:Yeah, okay, so to make a black hole, normally you need a pretty violent event, like an enormous star exploding and collapsing. So you need a pretty violent event to make a black hole. But what if we wanted to make miniature black holes that technically satisfy the equations of black holes, but they're so small and tiny that they would never do anything. In fact, they would evaporate immediately. We know that over long enough timescales, black holes should evaporate. This is something called Hawking radiation. Eventually, the universe will run out of stuff for black holes to suck in, and they will eventually have to evaporate.

18:30James Beacham:And over enormous timescales, they should evaporate all this stuff. So we know the black holes will evaporate. And if I made a tiny, tiny, tiny black hole, that should evaporate too. So if I were able to make these under a controlled condition, this would teach us a lot about black holes. in principle, it would be the first step toward understanding better what might be inside of a black hole. And you said we might be able to make black holes in a lab? Well, this is where it gets complicated because keep in mind what I said it takes to make a black hole. You need a kind of a violent event, but really what you need is you need to pack a large enough amount of stuff, either mass or energy density within a certain amount of space, and this would naturally make a black hole.

19:10James Beacham:So if I have two protons and I get them close enough together and smack them together, in principle, I can make a black hole. The problem though, is that I would have to reach an energy, you know, a collision energy that is so high that it's outside of the realm of our civilization at this moment. However, there's this idea that this energy at which you would make black holes, it could in fact be much, much lower because there could be extra dimensions of space that are everywhere around us all the time and tiny and curled up. Now, this is a bit strange. Right. Extra dimensions that would somehow allow us to make black holes.

19:48James Beacham:Oh, yeah. So at first, that doesn't make much sense. But you can think about it like, for example, imagine you're watching your friend on a tightrope. Maybe your friend's a tightrope walker. She's walking on a tightrope between two buildings. And you're down below, like in Manhattan. You're looking up and watching. You're like, oh, I hope you're OK. But from your perspective, she only has one dimension that she can go in, right? One direction, back and forth. That's it. She goes side to side. She falls, jumps up and down. she's going to jostle herself and fall too. Now imagine you zoom in to the rope itself.

20:16James Beacham:Suddenly, if you're an ant on the rope, there's an extra dimension that you did not see from a distance. The ant can go side to side, but the ant can also go around the rope. It has a different dimension. This, in fact, is entirely possible about our universe now. There could be extra dimensions of space everywhere all around us at all times, except they're imperceptible to you and me. You don't feel them, but maybe your particles and the forces do. And if that's the case, we would help explain why gravity is so weak compared to the other forces of nature. And maybe the reason why we measure gravity as being so weak compared to these other ones is because you and I are only experiencing a tiny three-dimensional slice of gravity that actually exists in multi-dimensions.