The other end of a black hole – with James Beacham

At first you wouldn't notice anything and then suddenly everything would change radically and violently. Imagine 500 years in the future, you are sitting in a ship traversing the silent void of outer space, you are traveling to explore a

black

hole

. close for the first time in human history, you are very lucky to be able to do this for centuries, the prospect of traveling to a

black

hole

was absurd, the closest one is almost 60 million trillion kilometers away, but they were achieved great advances in space travel and cryogenics and here you are, you are traveling to explore a black hole and you are about to make a very big mistake, but we are getting ahead of ourselves, what is a black hole?

Actually everyone here is sitting or standing as a couple. of people are standing, which may not seem like a profound statement, but cosmically it is, and if you then watch this video, you probably know, maybe at home or in the office, you're probably standing at a table or sitting in a chair. or maybe lying on a couch, no matter who you are, no matter your gender or skin color, you all have one very important thing in common, you are not currently floating around the room, why are you not floating due to gravity, Of course, gravity is the force? of attraction between any two large objects, such as between the moon and the earth, between the earth and you, but behind that simple statement lies a series of very profound insights that require us to completely change our understanding of the fabric of reality, so the fundamental question that hides underneath it all is what causes gravity so physics as you know this is the kind of question what causes gravity this is the kind of question that keeps physicists up at night because Physics is, among

other

things, as you know, the search for mechanisms, the reasons you know or uh or explanations for why certain things happen the way they happen, the why and the how, and if a physicist comes close to you and tell her what and ask her what causes x phenomenon and you tell her that it is, she will be very dissatisfied. with your answer, for a long time the question what causes gravity was not so well understood and even you know a pretty brilliant guy known as Isaac Newton, uh, even Isaac Newton, someone who managed to describe gravity quite well in the 17th century , even Isaac Newton. at some point I had to admit that I don't know what is going on, so in the general chive he says that I have not yet been able to discover the reason for these properties of gravity from the phenomena and I do not pretend hypotheses, he says, yes, my equations. it works really really well but I have no idea why and for a long time people would say okay maybe gravity is like a universal force and that's always the wind as it is and if you think about that it's a little bit too close that's how it is is not at all satisfactory and then what is that?

What is the mechanism that keeps you sitting in your chair and that keeps the moon orbiting the earth like this for a longer time? it was not understood until albert einstein and albert einstein needs no introduction in 1915 he finally came up with general relativity a general theory of relativity and came up with a mechanism that explained how gravity really works and required us to completely change our perspective on nature of reality and then the question is what, for example, when an apple falls from a tree, why does the apple fall? Well, the atmosphere, then maybe that's a bad example, but what about the moon?

Why does the moon fall? Actually, it's not good at all, but it's falling. empty space, but what is space? The concept of space for a long time was this notion that it was like you know there are different ways that people thought about it, but for a long time you could think about the concept of space. It's like the kind of background grid on which things happen correctly, so space is space is not real in the sense that you know like a moon or the earth or you know like a table or something, but yeah I want to, I can impose a grid on it so that I can describe things in the physical world in a better way, in a more convenient way, so I can impose a grid like, for example, lines on a blackboard, if I want to make a grid so that I can do it better .

It describes some planets you know that are doing something with arrows, I don't know what that was, I just decided to draw it at any time, but you know that grid is there to help me with my calculations, right? I know it's kind of an abstract thing and it's so abstract that if I wanted to, I could choose a different coordinate system if I wanted, and as long as it's consistent with what I'm talking about, then everything will be fine, right, and we'll let this guy finish your work here, great, very good, oh, that's good too, oh beautiful, you're an artist, um, but again, just so you know, space in a sense is this background grid. like these these metric lines that we impose on things to then be able to describe physical phenomena that go inside but it is not real, it is not as if I like to draw a circle on the blackboard, the blackboard will change or the blackboard itself will not change the circle, but in fact it is like this, you could think that space is like this, space is nothing, it is just a kind of background, it turns out that Einstein pointed out that this is not the case at all, Einstein pointed out that in fact, there is a way completely different from thinking about it, in fact, the way gravity arises, the way gravity arises, the way the force of gravity arises is due to the presence of the fact that the presence of a certain amount of things within a certain volume of space actually warp and bend the structure of space itself, so in that sense space is actually something malleable, it's flexible and this is a completely different way of thinking about the world, It wasn't just a you know. a small step forward is a radical change in the way we understand the world and so now, for example, if I put something that has a certain density so that you can think of space in this sense as more of just a space Completely empty is more like a sheet of rubber, right? and if I put something heavy on the rubber sheet, it actually warps it, if I don't have anything there, the normal rubber sheet and we all stretch it hard if I tap it.

A little marble on the

other

side, the marble goes in a straight line, but if I put something heavy in there, like a bowling ball or this yellow thing, and then if I push something, throw a little marble or something, it actually comes out of the marbles. In perspective, it goes in a straight line, but from a broader perspective, it is actually falling towards what is curving the fabric of space itself. This was a tremendously different way of thinking about the universe, so we have our mechanism, the Moon and the Earth, for example. They orbit each other because each constantly falls into the other's curved spacetime due to the presence of energy and matter density in space itself.

This is just mind-blowing, you know? And it still is for me and I was in time too, so this was a very, very radically different way of thinking about the world, but it gets worse because it turns out that not only is space not flexible, not only does it bend, but it It also flows. Space is something that can really move parts of the world. Space can actually move compared to other parts of space and this has wild consequences, so what that means is that this basically comes out of the equations of general relativity, so if you have something that has a lot of gravity, in You can actually have a space that folds creating a sort of sinkhole in the space itself, but if there are a lot of things packed into a small enough volume, the space itself starts to flow toward the center of that volume, so, for example, if you have the sun, it is true that it has a certain amount of density, the denser the object, the deeper the sink and the more space begins to bend towards the center of this volume, so the sun, for example, deforms space-time in a certain way, you can think of the extent to which this space flows towards the center of any of these objects in the sense of how fast you would have to go to get away from the surface of one of these things, so, For example, if you wanted to get away from the earth, we know you have to go pretty fast to get away from the surface of the earth, but we know it can be done, obviously, if you wanted to get away from the sun, you would have to travel 50 or 60 times faster. than that. and if you want to get away from a neutron star you need to travel at something like 60 percent the speed of light, since we, my astrophysics colleagues, estimate that the fastest speed a human could go without dying is something as well as half the speed of light and, as humans, the fastest we've ever gone on anything, I think it's something like 0.000 percent of the speed of light.

You're not going to walk away from a neutron star with our current technology, but think. about what this means if you take this to its logical conclusion, if I take a certain amount of stuff into space, space doubles and space starts to flow by a certain amount, if I put more stuff into its fixed volume, it starts to bend and flow even more, take that to its logical conclusion, if I put too many things in a fixed space, the space will bend and flow so quickly towards the center that no matter how fast I move, I will never be able to escape this flow and this It is our black hole.

You can think of a black hole as an extremely strong drain of water where the water is the fabric of space itself. Imagine that you are a fish in water. If you get too close to the drain, water will flow in faster than ever. possibly swim and even if you swim at the fastest possible speed you will be sucked down the drain just the same, if you stay far enough from a black hole in space you are fine but there is a point of no return called the event horizon beyond which space flows towards the center of the object faster than the speed of light, so not even light can escape from the inside of this black hole, but if that's the case, you've probably heard these things, I understand that for the last 10 minutes or so I've been saying things that many of you have heard a million times before, but what does that really mean if that means that space flows faster than the speed of light inside this black hole beyond this event horizon this point of no What does that really mean?

What is really happening inside a black hole? That's the million dollar question. If you can find the answer, you will have about 10 Nobel Prize winners. I think two things probably caught your attention when you see an image. like this, a gif like this, so the first thing is that thing in the middle, a singularity, so you've probably heard the word singularity before, but in a physical sense, what this means is that there is an sp point at the space where you have infinite density and curvature of space, I don't know about you, but I have no idea what that means and I'm a physicist, so I have no idea what it means to have, you know, actualize that in the real world, what means we have a point that has infinite density and infinite curvature of space, probably what this means is that there is something we are missing, so if you look closely at the mathematics of general relativity and you should always look closely at the mathematics, you will see these things like singularities that point out, let's jump into equations like this and usually when you have something that shows up in your equations that doesn't make physical sense, that's typically the universe's way of telling you to think a little harder and you are missing something.

There's something that needs to be put in place to avoid this kind of catastrophic nonsense, so the other thing you've probably noticed about this is that within the event horizon of a black hole, if space flows faster than the speed of the light, if you were to travel. to a black hole to study it up close and you should definitely want to do this because it will be amazing, you should probably stay away from the event horizon because if you go in there is no way you can tell the rest of us what you learned because there is no way to send a signal outside the event horizon, it's a one-way trip to a black hole, so those are the two things that you probably have, you know, that have moved away from you, so again if you wanted to go to a black hole to study it close and you should definitely want to do it, you definitely want to stay away from the event horizon and the first reason of course is that scientific reason, like I said, it would be a very very bad scientist if you go down a path towards a black hole and you will never be able to send your data back to the rest of the community, right, that's a sign that you're being a bad scientist, you know, a bad scientist to the community, but the second reason you'd want to stay away is actually existential because the conditions within a black hole are such that the gravitational conditions will be such that it is likely that with a certain size of black hole, it is likely that if you enter a black hole, the gravitational force on let's say your feet will be very different from the force on yourhead and you may be stretched into spaghetti, so for example fish in water drains, if a fish gets too close to a black hole it will probably stretch into something resembling spaghetti fish .

So quickly, existentially, you would want to stay away from the black hole as much as you could, but that is for black holes of a certain size, for example smaller ones. Black holes are medium-sized black holes, yes, the gravitational conditions as you enter will be so violent and so crazy that they will probably tear you apart or stretch you into spaghetti like this, but there is a big warning here and we will get We'll talk about that in a moment, but the other thing you should ask yourself is: okay, what I mentioned, and every time your math tells you something that doesn't make sense and doesn't make any sense and you think, wait a minute, this probably doesn't exist in the universe.

You should also ask: do we really know that black holes exist? Maybe this is just some kind of nonsense that arises from some equations that humans are using but that nature wisely avoids using because it doesn't make sense. It's not just a mathematical oddity that our universe avoids black holes. It was a prediction for many years, so let's go back to 1915, about 10 years before Einstein completely changed everything with special relativity. the guy completely ruined everyone's perceptions of the universe twice in 10 years, so these people were playing catch-up on this and the first some of these early predictions that were coming out didn't make a lot of sense, people thought like, okay, we need to verify this, we need to verify this, there is also this solution that you found that led to this concept, this object known as a black hole, which is very scary and strange, and for a long time, for decades, to people like, well, that's kind of the strange thing maybe you know, I don't know how we're going to detect one of those things, so maybe we'll see them in a few years or something, so it was a very strange prediction . for decades and decades until the 1960s when in the 60s and 70s astronomers noticed that something strange was happening near Cygnus x1 and if you can't detect the black hole in this object, no, you shouldn't feel bad because there it is where The black hole is hiding There is a black hole hidden in that point of light, so Cygnus x1 is actually a double double system.

There is a black hole with a blue giant supergiant star next to it and this is an artistic interpretation of what it is. cygnus it seemed to be eating another star that was next door and these signals matched almost exactly what you would expect from a black hole doing this, so this is an artist's radiation of course, you could also ask, okay, this is just an example, but we also know that we can, so we can't actually see black holes directly because no light can emerge from them, but we can see other stars orbiting completely dark empty spots in space, there's obviously something going on there in the medium, although even in the middle. there is no star that you can see and since then the evidence of black holes is increasing and increasing and as you know as of 2019 we can see the hot gas around a black hole as it twists around this black . hole and this is from the 2019 event horizon telescope collaboration one of the most amazing images humanity has ever produced and this is an m87 55 million light years away so black holes are really real and they're not even that rare, you know?

It's strange because the universe seems to love these twisted vortexes. There's a big one at the center of almost every large galaxy we've seen and our own. In fact, the closest confirmed black hole is Cygnus x1, which is approximately 6,000 light away. years away given the fact that our milky way is about a hundred thousand light years away six thousand light years is not that far away our universe our milky way appears to be dotted with smaller black holes too and there could even be a black hole mysterious Even surprisingly closer to Earth, on the outer edges of our solar system, several large rocks appear to be orbiting in strange ways.

Some astronomers believe there is a new planet, Planet Nine, that could be responsible for these strange wobbly orbits, but we see no evidence of a visible planet. And what happens if it's not a pl? The reason we haven't seen it is that it is not a planet, but is actually a small black hole the size of an apple that was born shortly after the universe formed, 13.8 billion years ago. ago and then floated around our universe for billions of years before finally getting stuck in our solar system, so an apple-sized black hole appears in an apple site.

Oh, and I wanted to show you this too, so actually a couple of physicists who proposed this idea because other physicists I know came up with the idea that maybe there's a black nine planet, then other physicists I know, jacob schultz , this guy says, well, wait a minute, what if it's actually a black hole in his article? you go to your article in the auxiliary supplementary material which is usually the place in the place in an article where you put really very detailed calculations that no one wants to deal with or you know or you like the extra part of your data, the copious list, so In case anyone wants to replicate what you did, this is the really boring part of the paper, these guys decided to put up a life-size version of what the black hole would look like, so this is if you printed the paper that's there, in the this on the page is pretty good, so a black hole the size of an apple, could you make a black hole yourself?

So if you want to know what it takes to make a black hole, just grab your textbook on gravity. I guess you all have a textbook on gravity. Set up your nightstand like I do and find the black hole equation. It will tell you, for a given amount of mass, what small volume you need to pack in to make a black hole, for example, to make a black hole out of the Earth. you need to pack everything into a volume the size of a blueberry, most of the black holes we know of, of course, are much larger than this with masses, uh, for example, the one at the center of our galaxy has a volume , Yes I believe. a diameter that is something like a third of the distance between the Earth and the Sun, but with a mass that is like several million times that of the Sun and there are also much larger black holes with masses that are in the billions, tens billions of times larger than the sun and with volumes that would encompass our entire solar system, but it's really that easy, the equation is fun, we can do some fun things with this equation, we can take any mass and look at it, like this This is our equation, let's imagine that we want to make a black hole from a proton, a proton is already very, very small, 10 to the power minus 15 meters, decreasing completely, it is already true, if you want to make a black hole from starting from a proton, you must package it. a volume that is 10 billion trillion times smaller than the Planck length, since the Planck length is the smallest physically significant distance that quantum mechanics allows us to define, a proton is safe, you are never going to make a black hole from a proton, what happens?

Can we make a black hole from you? If you want to make a black hole out of you, we would need to pack you into a volume that is 110 billionth the size of a proton, given that it is a thousand times smaller than the current one. powerful distance resolution on earth, which is the large hadron collider, you are also safe, we are not going to make a black hole with you, what about the sun? If you want to make a black hole out of the sun, you'd have to crush it. in a diameter in a sphere that has a diameter that goes from Westminster Abbey to Dalston, okay, so I know that sometimes, you know, during the peak tourist season, Trafalgar Square becomes so dense that it seems to be It would form a black hole, but no.

It's never going to be anywhere near the volume, the density that you need to create a black hole, like you know, packing the whole sun into Dalston, what about something really big, what about the observable universe? So remember that space bends and flows as we established before. We know that space is not static, it is actually malleable, it bends and flows. This also happens on a large scale. You may have heard that statement a million times before the universe expanded and it's true, we know the universe is expanding, but expanding into nothingness, space itself is expanding, for example two galaxies in our solar system or sorry, two galaxies in our universe are like two pins stuck in this sheet of rubber, so the sheet of rubber is being pulled from all directions from the perspective of an ant on the sheet nothing happened to make the pins move space itself is moving on the sheet and the distance between them is increasing so we know that this is happening to our universe and that's why we also know that in the particular way, so you know, for For example, if you, uh, if because of the particular way the universe expanded right at its birth, we also know that there are parts of the universe that are currently not observable to us, they are outside the so-called observable universe, this is a consequence the way the universe expanded right at the time of the big bang, right before the time of the big bang, in fact there are parts of the universe that are so far away that we can't see them, so the observable universe is defined as this sphere that is around you, each of you, in fact, has a slightly different observable universe, there is a sphere around you that is made up of all the things that have had the opportunity to send a light signal that they could receive, but beyond that we have no idea. how big is the entire universe, so the observable universe right now is 93 billion light years in diameter, but we have no idea about the entire universe, it could be infinite, in fact, it could be something smaller, we don't know, so we can't, it's very hard to estimate how much stuff there is in the entire universe, but you know, my astrophysical physics colleagues are pretty good, we can correctly estimate how much stuff there is in the observable universe, so If we take all the things that are in the observable universe, we add all the protons, all the neutrons, all the electrons, everything that makes up you and me and the potatoes and then we also add all the uh, the neutrinos, each one of you has about 10 trillion neutrinos from the sun passing through with your thumb, every second we add all these particles too, then we add all the dark matter and we add all the photons and we add all the gravitational waves, we get a huge number, we get some that the universe is probably the The estimated total mass is something like 10 to the power of 54 kilograms.

So if we look at what this is, again, we just use this equation, we can calculate what it would take to form a black hole from the entire observable universe and if you do it. In this calculation it is found that a diameter that is three times the diameter of the current observable universe would be needed. Let me check my calculation here, okay, okay, okay, astrophysical numbers are subject to uncertainties, maybe we got the number a little wrong. Let's imagine that even the number is double what we calculate here. Let's imagine that in fact the universe is something like uh 10, you know, 5 times 10 to the power of 53, it's half of what we thought it was, this will make more sense.

So if you wanted to make a black hole out of the entire observable universe, you need to pack it into a sphere that's a little bigger than the current observable universe. Were we living inside a huge black hole when I first found it? This calculation stunned me and it didn't make any sense. Is it possible that the inside of our entire universe is the inside of a huge black hole? I mean, it doesn't make any sense because I thought the black holes that you know from science fiction, these twisted vortexes that suck up entire stars and drive you crazy, you know Christopher Nolan movies, you know things like that, so I thought that's what It was black holes and this didn't make sense to me, turns out it depends on, so you know, I thought. that it doesn't make sense for us to be inside a black hole because you would just squirm, they would tear you to pieces just like we talked about.

It turns out that as long as the black hole is big enough, you'd be fine. be well within the event horizon of a black hole, soIt depends on the size, for example, if you fall into a black hole that is the size that would surround London, the solar mass black hole inside, you know it from Westminster. from Abbey to Dalston you wouldn't stand a chance of being ripped to shreds immediately, but with a big enough black hole you'd be fine, it would still be a one-way trip once you cross this event horizon, there's no way you're going.

I back off, but it's entirely possible that our currently observable universe exists inside a massive black hole. This is very strange, I admit, but black holes are more than astrophysical oddities, if you think about it, they are actually profound statements about the limitations of knowledge, so what does a black hole really do? Think about what he does. A black hole separates the world. Cetera, separates the physical world into two regions. You have the inside of the black hole and the outside of the black hole, and this event horizon becomes a barrier, a boundary, this thing that is always in the distance that you can never get to no matter how fast you travel you can never get to that. thing well we know that black holes eat things and grow, for example, so big that the artist's interpretation I showed with the swirling black hole sucking in the blue giant thatThe holes or the event horizon grows as it absorbs more things, so we know that that event horizon is growing.

If you are inside, this would also grow, so this horizon think about what it means to be inside a black hole. this you would have this point of space, this region of space that you could never reach and it always goes away from you on a horizon, so yeah, just so you know, show, so, you have things that are falling into the black hole, the event. The horizon grows properly, but think about what it means to you right now on Earth. Think about your situation right now here on Earth. If you look into space, there is a horizon far, far away, beyond which we cannot see, but we know there are things. there, but we'll never be able to see it and no matter how fast you travel, you'll never be able to get to it, that's remarkably similar to what you would experience inside a black hole and it turns out that math and again you should.

Always look closely at the mathematics, it turns out that the mathematics of the inside of a black hole is almost identical to the mathematics of the outside of the black hole. You know, you have to do some things with infinities going to infinity versus zero, but yeah, trust. I, you know, believe me, you can look it up in your gravity textbook that you have on your nightstand, but this is what's really happening mathematically. It also makes sense, so there's also another reason to think this. it's oh so yeah and for example I just wanted to show my nice animation here so as things go show me here, there come on yeah okay it's the same thing you've got things coming up , so this, this, this, this edge of the observable universe is getting bigger and bigger and, for example, if you could live for hundreds of millions of years, things would appear that you couldn't see before, so this is very similar to what you would experience inside a black hole, so the other interesting thing about this right is that we know that the universe is expanding and then if you turn back the clock like the YouTube universe slider, you eventually do backwards to the right, that means Everything very, very far back in time, if everything is expanding now, everything had to be packed into a tiny little dense point at some point and that is something similar to what you would expect of a singularity in the middle of a black hole, does this mean? that our universe, which was born from a 13.8 black hole, was born from a big explosion 13.8 billion years ago, our universe was actually born from a black hole in another universe and does that mean that black holes in our universe are doing the same thing in all cases?

The hole could be a seed for a new universe and I also see the looks on your faces and I completely agree with you because at the end of the day I am an experimentalist and these ideas are wonderful. I love these fantastic ideas. I love reading. About them, I love it when theorists go crazy and show me their new articles and look, this is happening at the end of the day. I need to see some evidence and it currently turns out that there is little chance that we will be able to gather evidence for this hypothesis. for the foreseeable future, so at the end of the day, again, this is not, this may sound very science fiction, right, but it's actually at the end of the day that you can find solutions again, by going back and looking closely at the mathematics that you can find. solutions that show that inside a black hole there doesn't have to be just one point of singularity, you know, that doesn't make sense, it's like mathematical nonsense, in fact, as you've heard and again I mentioned Christopher Nolan movies.

There are solutions that if you enter a black hole it is not just a point, but it could be a so-called wormhole or an Einstein-Rosen bridge and in principle this wormhole could be a wormhole from here from our universe to some other point in our own space-time within our own universe or it could be in another universe within a multiverse or in fact it could be a small seed for another universe but again I'm an experimentalist how do we go to try this? Here's the problem, can we test the idea of ​​the universe in a black hole, first of all, the way you test it is to go into a black hole and find out, as we mentioned, that it's a one-way trip.

Really, thank you very much for doing that, but I will never be able to. to learn what you learned, so you know it's a one way trip, second, there's no difference, there's no experiment that I can currently think of that would allow me to distinguish that hypothesis from some other hypothesis, so if I say, oh yeah Well, you know. We live in a huge black hole, okay, okay, you know, part of the equations show me that that's indistinguishable from our current experience, but how am I going to distinguish this from some other hypothesis? There may be some ideas floating around out there, but they aren't that obvious.

Well third, what does it mean for me to contact another universe? I would love for someone to give me a coherent answer to this question because the ideas that come up don't make sense, for example, what if I have a measuring device here in my universe? works very, very well as a ruler or you know some kind of additional device or something and I take it to another universe where carbon atoms do not exist. The measuring device is useless, so this is just an extreme example, but at this point you know. There is no way we can even test this hypothesis, so I love these ideas.

I love them. I want more ideas like this, but I also want ways I can test them. However, I'm actually excited for the future because I know from history that I would never want to underestimate humanity's ability to come up with ingenious ways to test impossible ideas, so I hope someone in this room ends up studying physics and finds a way to test this hypothesis again at the end of the We know that we currently don't have a way to test this, but one thing we haven't covered at all so far is the fact that this is how black holes arise because if we knew that, in principle, we could design an experiment.

To do something or maybe just so you know, to figure out how we could study this in an indirect way, we don't have to go directly to a black hole, just like we don't have to go directly and about the Higgs boson that we discovered. At the LHC you will never have the Higgs boson in your hand, but we can indirectly see that the Higgs boson exists based on its decay properties, things like that, so maybe there is an indirect way to understand whether or not we live within a black hole, but first we have to figure out how to make black holes, so how does the universe make black holes?

How does the universe make some of these twisted vortexes, these things that are so dense that they almost pierce well into the fabric of space-time? One way is when a huge star dies after billions of years, a star can use up the fuel it needs to burn and when the last hurrah comes, it explodes and then, with no more nuclear fusion to push it out, gravity wins and everything collapses on itself. and this collapse can be so severe that it creates a black hole, so you know, what you can see in this is what you need and also let me mention the black hole the size of an apple, so the knight black hole right here that he is holding.

These apple-sized black holes could, in principle, be something called primordial black holes, meaning they could be black holes that were caused right around the time of the Big Bang, right when the universe was born, and the shape particular way the universe expanded could have made a bunch of these primordial black holes appear and just spread around the universe for billions of years, so you can see that it takes an extremely violent event to create a black hole, it's That's why you can't create a black hole. from you or an apple or anything or the earth, is it possible that we can make black holes where I work at the large hadron collider?

So the large hadron collider is a 27 kilometer circular tunnel on the French border in Switzerland, about 100 meters underground. and in this tunnel we use superconducting magnets colder than outer space to accelerate protons to almost the speed of light and then hit them together millions of times per second at the particle level. This is a pretty violent event and is actually theoretically possible. We could make tiny versions of black holes that would evaporate immediately, but I know what some of you might be thinking. I also see some looks on their faces. Let me make it very clear to you that there is no way we are going to make a normal black hole in the large hadron collider for the following reason, you should already know this since you have seen the first one, you know the first half of this talk, black holes have to do with gravity, so we are colliding protons. together in the large hadron collider, the right protons get close to each other and start to experience interaction forces, we only know four, four known forces, fundamental forces in nature, right, we have three that you know, the strong force, the strong force weak, electromagnetism and then gravity. true, but not all have the same force, especially at the particle level, when two particles approach each other, some are more powerful than others, so starting from two, when two protons approach each other, the strongest force we know is called the strong force, it's a very nice name for this, so let's give it a pow a for a force of one compared to the strong force, the force of gravity is 10 to the minus 39 power, there is no possible way to that in fact we completely neglect this when we do calculations in the large hadron collider of proton collisions the force of gravity between two protons is completely negligible compared to each other, so there is no possible way for us to do this to create a black hole from two protons at the large hadron collider, oh, and I want to show you, show my nice animation here.

Pow Black Hole, it's not just a hammer home, but remember that the reason why, well, I'll put it this way, the reason why we physicists are obsessed and fascinated by black holes is because they could help us. Answer one of the most important open questions in physics for a long time and this is the question whether gravity and quantum mechanics have anything to do with each other in physics. We have two fantastically good theoretical models that have withstood essentially all of our experimental tests. The first is called general relativity, which we talked about and which governs how gravity works on very large scales and the other is called quantum field theory, quantum mechanics that governs the world of the very small, each of them on their own.

It is among the most impressive intellectual achievements. of humanity, but there is a problem when we try to naively combine these two theories in the hope of a more fundamental theory of the universe, everything fails, we get meaningless answers, such as infinite energies or probabilities greater than one, when this happens, as I said, This is the universe's way of telling us to think more and it's quite possible that the reason we haven't, we don't fully understand how gravity and quantum mechanics work together is that there is, in fact, something we're missing. about the structure of space itself, so one of the ways that gravity because basically the question is why gravity is so weak compared to the other forces why if you were some kind of person you know how to make a logical universe , uh, logical, you would never do it that way, it doesn't make sense that you have one force that is down here and all these other forces thatare up here, so one of the ways this could happen is if, in fact, our understanding of the structure of space needs to be changed, in fact, one of the ways The fact that we could be overlooking the fact that Why gravity is so weak compared to the other forces is whether gravity actually exists in extra dimensions of space that are small and nestled at every point in space and therefore gravity actually leaks into these other ones. dimensions. and if we had some magical measuring device that allowed us to somehow measure gravity in these other dimensions, we would measure it as if it were as strong as the other forces, this would be amazing and, you know, give some more details, basically, what? that?

What it means is that the Planck scale, so I mentioned this thing called you know, the plunk energy or the plunk length and things like this, basically, this is a length, an energy and a time scale that is a kind of a limitation based on the constants of nature and what that means is that the radius of a sphere, for example, remember again that it takes a certain amount of stuff that you have to pack into a certain volume to make a black hole properly. , but that's that radius again that's the Schwarzschild radius the radius part in the equation that was showing you correctly that radius the definition of radius changes when you have additional dimensions of space and in fact what it can do is make this plonk level this planck scale where is the place where gravity and quantum mechanics have something to do with each other, it could actually reduce it, it actually reduces what this Planck scale is and makes it in principle doable a black hole from two small things with a very small amount of energy, so this is completely possible, but what it means is that we are not going to make a normal black hole at the large hadron collider, in principle we can make a tiny object. that would break it and it would come into existence and enter the extra dimensions and wobble around a little bit before breaking down and evaporating into things that would hit our detector and you know, this is not an artist's tradition, but there is a simulated version.

If we were to make a miniature black hole at the large hadron collider it might look like this, so again, this is... you might be a little surprised by the fact that we could be making miniature black holes, but to just so you know I don't want to go, I'm getting a little late here, but I just wanted to show that in fact this shouldn't be a cause for concern because even if we made a miniature black hole in the large hadron collider, it would evaporate immediately one of these miniature things and it would be great if we did because it would help us understand gravity, how gravity and quantum mechanics work together and maybe help us answer one of these biggest open questions in science, but if we still you are worried, don't worry at all because the large hadron collider We use very high energies of the large hadron collider, but we are no match for nature.

Nature has much higher energy collisions all the time just a few kilometers above your head, so above your head right now there are cosmic ray protons coming from outside. space all the time and they get to the upper atmosphere and they collide with the atoms that are in the upper atmosphere and then if these things happen, these collisions are happening all the time at energies that are much higher. than the large hadron collider and you've never actually experienced a quantum black hole that suddenly enters your body and disintegrates and devours you. This has never happened, so if this has never happened in the upper atmosphere, it won't happen. a large hadron collider will happen and I think for time reasons I'm going to look at these oh I'll show my nice animations so you can do different things if we were to see these quantum black holes, these miniature black holes in the upper atmosphere. they would do certain things blah blah they could actually go through the entire earth and come through the other side or in fact they could decay right near the surface of the earth and we could detect them so actually there are experiments that are looking for things like this, but okay, while we could potentially make miniature black holes at the Large Hadron Collider, we haven't seen any evidence of them yet.

Oh, this is very sad, but maybe we just need a bigger collider. Discussions are currently underway about the possible successor to the large hadron collider, the future circular collider that would be one hundred kilometers in diameter and could achieve an energy seven times greater than that currently used, but will it be big enough? Maybe quantum gravity is the holy grail. I've been looking for maybe quantum gravity is waiting for us on the Moon, so the last time I was here at your illustrious institution I gave a whole talk on the concept of a Big Bang machine on the Moon and I went into very rough detail. about what it would take to build a collider to go around the moon and why we would want to do this and just a few, just a few months ago, in fact, a colleague and I finally wrote a paper on this concept and it turns out so you could think that it is like building a you know, a colossal collider around the moon will be ranked 11th where the large hadron collider is 27 kilometers around the circular collider on the moon it would be 11,000 kilometers around and could reach energies a thousand times more than what is currently used and I also see the expressions on some of their faces so building a collider around the moon to potentially create miniature black holes on the moon is that crazy and I actually did it.

I did the exercise with a colleague of mine. and it turns out it's not crazy, in fact there are no obstacles to building a circular collider around the circumference of the moon, all the technology is there, all the science is there, it's just a question of scale, it's just a question development and scale. a circular collider on the moon sometime in the 22nd century is something that may seem impossible, but it is simply impossible, it is not impossible, and it is possible and impossible, we can do the impossible, it is only impossible until such time as someone does it possible, so it is to be big enough, although maybe a lunar collider will not be big enough for us to make these miniature black holes again.

The point here is that we wanted to understand how, what really happens inside a black hole, how they were made maybe. We could find a way to do them in the lab so we can understand them. The place where we really want to go to fully understand this is called the Planck scale, and the plunk energy again, if these additional dimensions don't exist, then. the planck scale is something extremely high, this is an energy in which gravity and quantum mechanics must have something to do with each other. The bigger the collider you build, the higher the energy, the greater the chances of discovering things like miniature black holes, so, the problem is making a Planck-scale collider.

By some estimates, you would have to build a collider that orbits the outer edge of the solar system. Clearly we are going to need some major innovation to do this. When our society, our civilization, advances enough to be able to build a superstructure like that, it will probably also have mastered interstellar space travel and at that point, 500 years from now, you will be sitting in your ship traversing the vacuum of empty space to explore a hole. black one day in your ship you get tired you realize that you should reach your destination in about twenty thousand years so you decide to take a nap for 20,000 years and while you lie down on your cryogenic bed you very lightly hit your ship's accelerator nor you don't even notice after 20,000 years you wake up you make a cup of coffee and you notice on your gravitational sensor that something is very wrong you seem to be too close to the event horizon of your black hole you look out the window and see a huge, deeply black disk In space, the light of stars and galaxies behind it, twisted and warped, you stare into the center of this void, a cosmic eye staring back at you and it's the emptiest thing you've ever seen, your jaw drops. and your eyes open and then you realize you're not sure you're past the event horizon, but at the point of no return, you double check your gravitational sensor and it says you're not there yet, you have five seconds to fly. you jump out of your chair jumping towards the rocket controls spilling your hot coffee on your hands burning your fingers you scream and fall to the ground and when you get up it's too late you're passing the event horizon of a black hole you almost stop breathing you feel the mouth like sand and you close your eyes you can't believe this could be happening you open your eyes and look out the window again and everything looks more or less the same the disk is getting a little bigger but otherwise everything is the same you feel same thing nothing is different you think maybe your estimate was wrong maybe there is still time to escape you triple check your gravitational sensor and no matter which direction you point it says you are pointing towards the center of a black hole and then you know for sure that you have passed the event horizon you are inside a black hole a quiet terror takes over you how did you get to this situation very slowly while you were sleeping?

The conditions of the universe around you were changing almost imperceptibly and then suddenly it was too late floating in your ship inside a black hole, what do you do? You might start thinking about possible escapes. I mean, you know logically that it's impossible to get out of a black hole again, but you think maybe there's something you missed. You go through all the options, I mean maybe all the smart scientists were wrong and there's some way to escape that wasn't anticipated, you start to fantasize that maybe if you wait long enough or just get lucky, you'll eventually get over it again.

At the event horizon, you could walk away from the black hole and go back to the way things were, go back to the world you once knew, and as you fantasize, you look down and see that your feet are moving away from you and your dreams. legs are stretching. long thin strands like spaghetti and suddenly your shoes are so far away that you can't see them anymore and in that split second before you reach the center you realize two things, one that no one really knows what happens in the center of a black hole and two there is no turning back the only way out is straight through the black hole sometimes reality twists seemingly beyond recognition and right now as the oceans burn and global temperatures rise and literal fascists have returned to our politics and so many of us have died from a poorly managed pandemic, you would be forgiven for thinking that we had fallen into a social black hole;

In retrospect, it happened very slowly, almost imperceptibly, while many of us were asleep and then everything changed, but like a black hole in space the only way out is through our current social black hole it is a golden opportunity to build a world better and think of radical new ways of doing it, but we will have to go deeper, very deeply, like when we study a black hole in space, if you like, if we could go to a black hole in space or create one in the laboratory, we could study the fabric and structure of space-time to understand what creates these twisted vortexes and right now we can use the current contemporary situation to understand and collectively study the fabric of society itself to understand what leads to these social black holes, how the structures social black holes that we have around us lead to such social black holes and how we can change them, for example, there is more than one reason why we should consider building a large collider a circular collider around the moon the first is scientific I want to know what surprising discoveries could be in this data even though I'll be dead a long time, we'll all be dead a long time It's time this thing starts taking data because discoveries like the understanding of quantum gravity could completely change our perspective of reality, But there is another reason why our society is addicted to repeating its mistakes and right now we seem to be on the verge of simply giving the moon to space. and mars to wealthy private individuals and corporations whose only interests are extraction, exploitation and profit.

This is bad because this extractive and exploitative mentality here on Earth is leading to the destruction of humanity due to anthropogenic climate change instead of allowing for, like encouraging, a moon. rush, for example, the moon should be protected in perpetuity against commercial exploitation and a project like this, a circular collider on the moon, sounds crazy, but it is a project that will berides solely because our species is curious about nature, focusing projects like this when we explore anything, not just space but anything humanity explores focusing projects like this would remind us that the moon belongs to everyone the moon belongs to everyone space belongs to everyone we need to definitively abandon the systems that, for example, lead to situations in which a few dozen individuals can have as much wealth as billions of the rest of us together must abandon these systems, if that seems impossible to you Please note that gravity creates black holes and gravity is simply a law of nature, but the social, political and economic structures that lead to social black holes lead to things like extreme wealth inequality, racist policing or emergencies climate, these are not laws of nature, they are created by humans, which means they can be undone by humans, we need to finally find the courage to undo these structures, we owe it to the humans of the future because of course you will not be you in 500 years traveling to a black hole to explore it up close, it's up to us to fix our social inequalities and it's up to us to make sure humanity isn't crushed into oblivion so that your great granddaughter of 25 great-grandfathers can move forward. the unknown to better understand humanity's place in this vast universe.

Thank you.