55 Minutes of Interesting Facts About The Universe ¦ Brian Cox

If you define God as the creator, yes, then you're right from from some point that we don't understand by the way We do the Big Bang. We don't even understand whether that was the origin of the universe By the way, we understand that something interesting happened infinite cyclical universe. Yes, and he's trying to answer questions about the very special state of the early universe and why it was the way that it was it doesn't Recontracts it kind of it's called. What's it called conformal cosmology or cyclical conformal cosmology hasn't So it's essentially that and I don't fully understand it and I have asked him about it with some colleagues No, I don't think many of us understand what? Roger I mean Roger Penrose is one of the greats, right? So you listen to him and take him very seriously, but I've met anyone who quite understand what he what he's talking about but But it doesn't recontract it's not one of those models where the universe expands and then and then recontracts and bounces like that It's not one of those It's somehow he argues that when you get to what we usually call the heat death of the universe where even the black holes have evaporated away you have conditions that Begin to look perhaps like an origin of the universe again, and I can't really fully explain it because I don't really Understand what he's kind of looks like conformal means there are no Sort of distances or time measurements or anything in the universe it kind of loses all sense of scale and Then you could you could reimagine that as looking somewhat like the beginning. It's something like that that he has in mind But I really couldn't explain to you. I don't understand what what he's what he's proposing Wow, so it but what it does tell you is that we don't know Why or how the universe got into the state? That we call the Big Bang So we don't we don't know whether the universe existed before that we have theories that it did theories called inflation which are very popular Theories you'll find up in all the textbooks which say that before the universe was hot and dense Which we used to call the Big Bang Space and time is still there and the universe is expanding extremely fast It's called it's called inflation and then that period draws to a close and that expansion So slows down and almost collapses and changes and the energy that was driving the expansion Gets dumped into space and changes and ultimately makes the particles out of which we are made So that that's that's actually the standard model of cosmology now So so we do have an idea that We redefine the Big Bang is the hot Big Bang and it's not the origin of the universe in time It's the end of inflation. Oh And then you get the question. What is inflation there? What did that have a beginning and the answer is that In Einstein's theory alone then yes And Roger Penrose actually in Stephen Hawking proved this a long time ago that just given Einstein's theory You have this singularity just like kind of like the black hole singularity, but at the beginning of time but We do know that when you put quantum mechanics in and add that in Then it gets messy and we don't really know what that means And so Stephen Hawking had a thing called the no boundary proposals all sorts Basically, the point is we don't know so we don't know whether the universe had a beginning in time I would say is that is the correct statement as we are at the moment There's a part of the reason why by the way getting back to the black holes they're important and interesting Because the study of black holes and this idea of information and how does it get out? That's leading us to suspect that space and time themselves are not fundamental, but they emerge from something else So just in the way that we've been talking about consciousness Emerging from this physical structure in our heads, so we don't know how it emerges It's a very strange thing, but it but it emerges from this collection of atoms right in a particular pattern Well, we think now from the study of black holes that space and time emerge from something else Which is kind of the one way to describe it is just a quantum theory So it's in quantum computing terms. It would be just qubits So a network of qubits and tangled together just like a quantum computer out of that We suspect that space and time might emerge So surely we have to understand that process and we don't really fully understand that but we have glimpses of it in much more detail to start talking about the origin of time because not to talk about the origin of time you have to know What it is and we don't actually know what it is Which is you know, and that's kind of when you say that it sounds bizarre, doesn't it? Well, how can you not know what time is? I think Einstein once said that it is the thing that you measure on a watch But he said that as kind of an almost a joke because You assume in Einstein's theory. There's a thing that the watch measures, but what actually it is At the deepest level is a good question. So but it's funny. It's interesting that study of black holes is forcing us towards these theories it's not that we had the theories space and time emerging from something and Found and decided we could check it by thinking about black holes. It's come the other way around really And so it's it's interesting but that that almost makes The universe look in some ways like a giant quantum computer Which is not to say that we live in the simulation But it just looks like there's a description of the universe That looks like a quantum computer type description that doesn't have the concept of space or time in it It is it's interesting that it you're right and that's a good way of phrasing it mimics how looks like Right a network of qubits. So it looks like Some kind of quantum computing description is is is available to us, right the universe It's right to say that Einstein Really felt I think that initially that an eternal universe was more natural But it is also true to say that his theory General relativity really Doesn't quite rule that out, but it's strongly suggestive of there being a beginning and or an end So the theory itself historically speaking Strongly suggests that and so he came changed his mind and then we saw the universe was expanding We observed that and then we've now seen the oldest light in the universe the cosmic microwave background radiation Which is the afterglow of the Big Bang. So we know that the universe was hot and dense 13.8 billion years ago We have so much evidence for that not least that we have a photograph of it 380,000 years after the Big Bang. It's called the cosmic microwave background. Let's see that images of that That's from the satellite called Planck a European satellite and also a satellite called Kobe So we have this images of the afterglow of the Big Bang We also have theories that tell us about the abundance of chemical elements in the universe which match this perfectly So there's multiple lines of evidence that tell us the universe was hot and dense But none of that tells us that that was the beginning that I think that would be Widely accepted then it's a beginning in Einstein's theory. If you just take general relativity There's a singularity there at the beginning of time We don't know what it is, but it's there but it absolutely is true to say that we think that's not complete as a picture So so we there it is that's that so that is light that was emitted about 380,000 years after the Big Bang So it's it's a and the key thing. There's so many things to say about these images, but one thing is those colors Correspond to regions of very slightly different density that we detected now in in the in the gases of the young universe Are you talking about the red blue? Yeah, the reds and blues those those are those as well They're both both same. So that that greeny one. Well, either that one or the one with the greeny blue that one That's the from the Planck satellite. So those colors Correspond to regions of different density So in this young universe 380,000 years after the Big Bang, that's only hydrogen and helium gas Basically and a bit of lithium bit of little some of the lighter elements were basically hydrogen and helium So you've got an almost smooth almost featureless universe then but these little Density fluctuations are very important because as the universe expanded and cooled they collapsed to form the galaxies So without those ripples without that pattern we would not exist Nothing of interest would exist. And so you the question is where did that come from that pattern? It's fundamentally important and The theory of inflation that I mentioned earlier that there's this time before the universe got hot and dense That theory predicted that pattern before it was observed So this idea that you've got this very stretch very quickly stretching space By the way, so it's so the stretch if I can remember the number is if you consider two points in space during inflation The distance between them was doubling Every 10 to the minus 37 seconds, which is point nought nought nought nought nought nought 37 noughts one of a sec. So it's incredible rate of expansion that draws to a close and those theories So there's inflation there. So those theories predicted slight variations in the rate at which inflation stops There are a lot of things about the universe that that I find it almost impossible to imagine Well, actually impossible to imagine one just the size and scale of it. I mean in the piece of the universe we can see there are something like Roughly 2 trillion galaxies. We haven't counted them all but that's a an estimate based on Surveys of the local universe 2 trillion 2,000 billion galaxies and each galaxy is let's say Around the size of the Milky Way some are bigger some are smaller but the Milky Way has 400 billion stars in it takes light over a hundred thousand years to cross a Galaxy and there are 2 trillion of them in a piece of the universe we can see and we're very sure that that piece that we can see is a small bit of What may be an infinite universe beyond we don't know actually and I always say, you know Don't get worried about that because nobody can picture it It is impossible to visualize the scale of the universe And so that's the first thing I could I could then list a lot of more of a thing But we'll stop there for now, but just the size and scale of it. I think is beyond imagination And that is a very good question. The one minute Answer is we don't know so one of our theories is that space and time for that matter So I should say back in 1905 Einstein realized that space and time are not separate But they're woven together into something that's often called the fabric of the universe or more technically space-time But we now suspect or at least we have a theory that space-time emerges from something deeper, which is just basically quantum entanglement so we think that there is a description of our universe, which is just Bits of information basically or qubits to be more technical quantum bits of information That are entangled together into some sort of network So space and time don't exist in that network and then space and time emerge from that deeper theory This is cutting-edge physics, but it's one of the pictures that we have for what space and time might be Often is the case with science questions There's not complete agreement, but there is a theory that with which most people agree Which is that it was made in an impact so very early on in the life of the solar system So let's say four and a half billion years ago or so. We think that a planet about the size of Mars collided with the young earth and It's a glancing blow actually, which caused a lot of rubble to go out into space Formed a momentarily a ring around the earth somewhat like the rings around Saturn but then that ring very quickly coalesced into the moon, so we think that the moon is made of Mainly bits of the earth and also bits of this other planet that glanced off it about and much of the exact day I think something like four and a half billion years ago. It's very very early very soon after the earth form So, um, I say sometimes in my life shows there's only it's kind of a joke, right? So I'm not insulting philosophers here, but I say there's only one interesting question in philosophy And I don't really mean it, but I think it sounds funny And so the interesting question is what does it mean to live a finite fragile life in an infinite eternal universe? So that's not that funny, right? It's a good question What does it mean to live a finite fragile life in an infinite eternal universe? And then I think the answer is that So paradoxically whilst we are definitely physically insignificant I've just said, you know The earth is one star around one The earth is one planet around one star amongst four hundred billion stars in one galaxy amongst two trillion galaxies In a small patch of the universe, right? So we're definitely small and you can't argue with that We're just specks of dust But if you think about what we are So everybody me and you everybody we're just collections of atoms, right? Some of them are as old as time pretty much and some of them Were the other ones everything else other than the hydrogen in our bodies was made in stars, right? So we all cooked over billions of years and we're in this pattern that can think So suddenly there's a great Carl Sagan said you have a means by which the universe Understands and explores itself, which is us and that sounds unlikely when you put it like that That you can have a few things that were cooked in the hearts of stars You stick them together in a pattern and suddenly as some ideas and starts writing music and an arts and thing That's that's quite difficult to comprehend, right? But that what that happened here We know that because we're sat here having the conversation And so the question then becomes well on how many other worlds did that happen? And that's where I think the value can come in Because it's a reasonable guess and it's just a guess right, but it's reasonable you can make the argument That there aren't any other worlds where this happened certainly in our galaxy So it could be this planet notwithstanding its physical insignificance is the only place where anything thinks Right for millions of light-years in every direction And suddenly therefore you end up Considering this planet has been the most valuable place in the local universe Notwithstanding the fact that it's small and that idea It's not just a complete random guess by the way we've had a bit of a look with astronomers have pointed radio telescopes up at the stars for a while 50 years or more now and Heard nothing. We've seen no evidence of any Civilizations out there beyond earth and that's a surprise There's a reasonably plausible explanation for that which is biology Which is that if you look at the history of life on earth? Then you see that life began pretty much as soon as it could here on earth We have evidence there was life 3.8 billion years ago something like that and the earth's four and a half billion years old So pretty much pretty quick in geological time you get life But then if you talk about advanced like complex life multicellular life, then there's no evidence at all beyond Back beyond a billion years actually really in the fossil record 650 million years ago or something you start seeing the first evidence of complex creatures So that means that on he on this planet It took over three billion years to go from a single cell life To anything more complex than a single cell and then another half a billion years or so to go from the Multicellular things to a civilization, so it's three and a half to four billion years It's a third of the age of the universe that is a really long time if you say That's an unbroken chain of life on a little piece of rock in a violent universe and that chain was not cut For four billion years in order to get us and that might be a big ask We live in a really violent universe You look at the Milky Way and you look at that arc of stars across the sky 400 billion Suns, although all there will be up there at best is slime It's just like Nothing, right? And I think that's a reasonable guess. That's my that's where I start from. I mean, I wouldn't be surprised if That's wrong. Then you go. Okay good. Well fine that but at the moment It looks like there isn't anything else other than slime. We haven't even discovered slime by the way yet We're still in the position where we've not seen any not even a single cell on Mars or you know The moons of Jupiter or somewhere like that. So at the moment we are alone As far as we can tell. Oh That's a good question. And so I I don't know the the figure for the biggest star But the one of the biggest you can see and with the naked eye actually is Beetlejuice or Betelgeuse in Orion And that's so that's the red star and in in the constellation of Orion I sort of want to say but I can't because the orientations different here, but it's a top left But it's not it's gonna rotate it over Go and find Betelgeuse It's a red star in Orion the shoulder of Orion and then what's interesting about that is if you put it where the earth is Then it would extend out pretty much to the orbit of Jupiter. I think even beyond the orbit of Jupiter So if you imagine how far it is to Jupiter that will be orbiting inside the star and it's so big that we can see Sunspots on the surface with telescopes here on earth So it's a vast star but that that isn't that's a star at the end of its life that's swollen up that isn't however the biggest and and so what we should probably do is that and I Should go onto the internet and look up I don't have in my head the number for the most massive star or the biggest star, but there are stars that are Really literally the size of solar systems Yeah, well, they have very short lifetimes. That's the thing. So the more massive the star is so you're talking about as you said a star Let's say 10,000 times the mass of the Sun then it has to burn its fuel Extremely quickly to stay up against the force of gravity. And so they live Millions of years actually the lifetimes are not not billions of years. So they're very very very short-lived They're really massive stars in the universe So the the number of stars you can see first of all is actually only a few thousand I think it depends obviously depends on how big the telescope is that you have all of the stars we can see are in our Galaxy, and the only thing you can see beyond our galaxy. Well, there are three things in the southern hemisphere You can see the Magellanic clouds Which are satellite galaxies of the Milky Way and you can also see Andromeda with the naked eye And that's pretty much all you can see beyond our galaxy without binoculars or a telescope You get some good binoculars and you start to see tens of galaxies or even a small telescope you can start to see tens or even hundreds of galaxies out there and The number of stars in the universe that's a so there are something like between 200 and 400 billion stars in our galaxy and you might think that's why it's not because I don't know it's because nobody knows It's quite hard to count actually so it changes all the time that the estimate, but let's say conservatively 200 billion that's 200,000 million stars in our galaxy and the current estimate for the number of galaxies in the observable universe Which is the bit we can see is around 2 trillion so that's 2 million Million, yeah, that's right 2 million So we have something like let's say 2 million million galaxies that we can see in principle and each one of those Has 200,000 million stars, let's say on average so you have to multiply 2 million million by 2,000 million so that's a 6 and a 6 and a 6 that's 18 19 20 21 So it's something like let's say 4 With 21 knots after it. So that's a 2 with 12 knots after it and then we have a Let's say a 2 with 9 knots after it so it's a 12 and a 9 so that's 21 knots and probably 4 or 5 So let's say 22. So let's say 1 with 22 knots after it's something like that However, that's the bit of the universe we can see in principle. It's called the observable universe. We very strongly suspect That the universe extends way beyond the bit we can see It does for all intents and purposes and we don't know how big it is. So it could go on forever We just don't know and so You know, these are big numbers You you know these questions we have about our place and and as you said it can be easy to be myopic Can't you? Yeah, so if you look at our screens We it's it's earth that we think about at most And most of us don't really think about earth you think about your country or your city or your town or your neighborhood Yeah, you can think about the earth But you're right if you know when you look at that arc of stars and as you said when you see it in a truly Dark sky. Yeah powerful. It's incredible hundred billion Suns give or take 400,000 million Suns most And most of them I think probably the best guess would be all of them have planets so pretty much So you're talking about trillions of planets now, we're getting into my subjects No, I mean the thing is there's a thing called the Fermi paradox Yes, which I think we talked about before on the show. Yes, which is and the paradox is That if if we haven't seen it, let's assume we haven't seen any evidence of anything That's a paradox because as I said, there are we now know we didn't when Fermi first posed it by the way We now know there's so many planets out there So let's say trillions of planets in the Milky Way Milky Way has been there for over 13 billion years pretty much the age of the Universe so if there's no one else out there, then the question is why? Because there's been so much time and so many places for civilizations to become space-faring civilizations Right as as as Elon talks about multi-planetary civilization we're very close to becoming a multi-planetary civilization and once you have become a multi-planetary and Multistellar civilization if you become that you're immortal basically essentially, right? So the question is the paradox is why does it appear nobody has done that? So the first thing to say is I would not be surprised But if a UFO landed here now in the parking lot, I'd actually not only would I not be surprised I'd be relieved actually This is good because it'd be a weight off my shoulders because I'm worried that we're the only ones that's a terrifying Scenario and we're gonna make a mess of it. Yeah, and so I'm worried if we could talk about that Isn't it bizarre like that? We're the only ones in our galaxy. Let's say okay, then I would argue That so there's a question I ask any of these live shows that I do I start with a question which is kind of a joke in a way Which is what does it mean to live a finite fragile life in an infinite eternal universe, which is a good question, right? That's what you're asking. Yeah Right, the first thing to say is Meaning right, but it mean that that doesn't sound like a scientific concept in a way me, right? I would argue that whatever it is It self-evidently exists because the universe means something to us. I Would argue that it's a property of complex biological systems. So whatever it is It's something that emerges in this case from human brains It self-evidently exists we everyone is listening to this knows that the the world means something to them so I would argue that if This planet is the only planet in our galaxy where complex biological systems exist at our level Then it follows. It's the only place where meaning currently exists in a galaxy of 400 billion Suns and Therefore I would argue just for that very basic point that we have a tremendous responsibility in some sense because if I by the way I gave a talk a little video thing at the one of the climate summit the COP climate summit in Glasgow in the UK a Few years ago and they asked me to do a little video to the world leaders And I think they thought I'd say, you know, welcome to Glasgow have a nice meeting But I made this little argument as fast as I could I said it's possible at least that this is the only place where complex Biology has emerged in in our galaxy if that's true This is the only island of meaning in a galaxy of 400 billion Suns and you are responsible for it because you are the world leaders Therefore if you destroy it through deliberate action or inaction Then each of you would be personally responsible for destroying meaning in a galaxy of 400 billion Suns potentially forever Now go and discuss that Was my intro to Glasgow now and we can all argue because people have listened to this going this Nonsense how can it be we can all argue about whether that's true what I would say is Given that as far as I'm aware, we don't have any good evidence to the contrary Which goes back to your previous question. It's a reasonable working assumption So why don't we just operate on that basis and then you know Yeah if someone lands tomorrow as I said I'd be very delighted because then what I just said would be false and We could relax a bit and go it doesn't really matter if we destroy ourselves to some extent but so I think It's worth taking seriously the idea that civilizations are very rare now And by the way, I used to say so I probably last time I was on actually complex life will cease to exist So it probably doesn't matter on a global scale But it matters locally because of this idea that meaning emerges from complex biological systems So if you don't care about that, what do you care about that? It's not necessarily true. The life is Temporary because you could imagine a situation as you go into the far future Let's imagine that we continue for a million years or a billion years as a civilization Imagine what we could do. It is possible that life can get so advanced in the universe that it can start to Manipulate the universe itself So or at least stars you could imagine he said you could imagine for example, just imagine wild speculation But imagine life gets so advanced that it can start to change the destiny of a star Maybe it could start to add material into the star or something, you know, whatever So we don't know how to do that or if it's possible, but imagine it could then the evolution of stars Would life would matter in the sense that it could start to change the way that the universe behaves on a large scale in the future and so it's Reminded me actually is another great book By John Barrow and Frank Tipler called the anthropic cosmological principle from the 1980s It's one of my favorite books actually and I remembered it and in there they speculate about this life in the far far future and if it became powerful enough to Manipulate the whole universe or the observable universe then suddenly it's can't make predictions about the far future Unless you consider the possible impact of life on the universe and whilst this is I should say it's what wildly Speculative, but it's actually logically it's quite an interesting point So so I kind of disagree with my self a few years ago where I would have said that Life is extremely valuable because it brings meaning to the universe But temporarily and so it it bring these brief like flickering candles of meaning and then they go out again But it but it's it's worth considering. It might not necessarily be true that if you really think I mean just to say I mean, it's it must sound so many people listening just nonsense, right science fiction But if you think our civilization has been around for what 10,000 years at best really give or take And in that time we've sent stuff out of the solar system We've although we don't yet we're way away from being able to manipulate stars. We can manipulate planets So we are changing the way this planet operates life has changed it You know the oxygen in the atmosphere before we appeared the oxygen in the atmosphere is a product of life. So life already We know changes planets and so that that spec I like that speculation that possibly just possibly It's not just a temporary little phenomena that flickers in and out and then disappears again It could wrap it a real bearing on the future of the universe Well exactly and this is the point that David Deutsch made in the in the book I've just been reading and and John Byron Frank Tiffler made before that that it although it sounds insane Right you said And that four billion years there's a lot to say about that By the way, because for three billion plus years of that on this planet, it was just single cells. And so So it's only in the last Let's say a billion years, but actually a bit less that we've had multicellular organisms So three quarters of it at the time were just single cell. That's even crazier So which is one of the reasons that many people think civilizations might be rare Because if you just the only evidence we have is this planet right and the evidence on this planet is that single-celled life is sort of the way that things are for most most of the history and then so it seems like a An accident in a way that happened late on in the history of life on earth that produced multicellular life And now what is that typical? We don't know maybe it was took a longer time here than it might might do somewhere else But if it's typical, I mean four billion years you said it it's not a long time It is a third of the age of the universe So here you put it that way. It's a long time I think one third of the age of the universe to go from the origin of life to a civilization Mmm, and and so what was required here on earth was that that broke unbroken chain of life? Remained unbroken for a third of the age of the universe in a violent universe Maybe you know, we know their impacts from space many stars are Significantly more active than the Sun So the Sun's kind of a quite a boring little star that just ticks along. It's very nice to us We're also on the edge of the galaxy, by the way We're not close in if you go into this region where that black hole is There are a lot of stars around there are supernova explosions and all sorts of stuff going on. So it's violent in there So maybe you can only get unbroken chains of life for billions of years on the outskirts of a galaxy So there are fewer stars and planets out there and maybe even then you need to be fortunate Well, also we aren't we very unusual in the size of our moon and the distance the moon that it is big And so it stabilizes the spin. So the spin axis Mars I think if I'm right, I think the spin axis is wobbled around by something like 60 degrees or something So What you mean by probability favors the existence of aliens? I guess you mean and I'd agree with you that the universe is so big I mean, we just said that there was something like one with 22 knots after its stars in the observable universe We now know that most of those and have planetary systems And certainly if you look in the Milky Way, which we can do in our own galaxy Basically everywhere we look we find planets around the stars. So let's say that most of them have solar systems So it is inconceivable that there will not be life and I think civilizations out there amongst the stars But the question becomes first of all, what form does that life take so in the solar system We know there's only one place earth which has complex life and certainly a civilization like ours It could well be that there are microbes and below the surface on Mars today or there may have been microbes on Mars in the past when Mars had rivers and Lakes and quite possibly oceans for a few hundred million years And so they could have been Martians, but there would have been little microbes or bacteria like things At best I think and on the moons of Jupiter and Saturn Europa There are oceans below the surface and we think the conditions are right for life to have started But we don't know because we haven't been there. So if there are aliens in our solar system They'll be little single-celled things waiting for us to find them. Some of you might discover them actually because we are Building missions to Mars will be sending humans to Mars certainly in your lifetime And one of the things you'll be doing is looking for microbes below the surface So maybe we'll find Martians But if you mean aliens in spaceships that means civilizations and We don't know we've looked a bit. We've listened for radio signals from other stars. We found nothing We have no evidence of alien civilizations at all That might mean we haven't looked hard enough because we haven't looked particularly hard the galaxy is very big, but it might also mean that civilizations are rare and The one thing I would say is if you speak to biologists They will be more pessimistic about discovering civilizations than astronomers I think astronomers tend to say don't know how to get loads of planets loads of planets There must be some but biologists say well, but if you look at life on earth, it began we have good evidence It was on the planet. Let's say three point eight billion years ago So let's say it may have begun even four billion years ago after the planet settled down and the oceans first formed It took four billion years let's say to go from the origin of life to a civilization, which is about a third of the age of the universe and if you Start to say well if that's typical and we don't know Then it may be that there are very few solar systems and planets and stars that are stable enough for that long to allow the Evolution to do its work and for the single-celled things to go to Multicellular creatures and plants and make an oxygen atmosphere and and then make a civilization, you know You get some things that are clever enough I mean you think about there are clever things on earth besides humans dolphins, for example But dolphins are not going to build spaceships because they can't have any electricity because they live in the sea And so you know it can it could be that quite typically if things with big brains tend to be under the water Then they're never going to build radio telescopes and spaceships. They won't be astronomers So if civilization exists, then yes, we could and again the distances are important If you think about our galaxy, it's let's say a hundred thousand light-years across or so That means that it would take a radio signal a hundred thousand years to go from one end to the other So it would be a very slow Conversation. I mean even our nearest star and Alva Centauri the nearest star system With planets around it we think is four light-years away or so So that means that around a conversation would take eight years So you said hello, you'd have to wait for eight years before they said hello back and that's our nearest star system So the distances tend to make conversation difficult so the first answer is I don't think we know when the Milky Way and Andromeda collide whether the black holes will merge I mean, we certainly know there's an interaction between the galaxies. We know they will the galaxies will merge so I May be there. I mean my guess not actually knowing the latest research is they probably would eventually I think But it depends on the angle that they hit each other and so on and so on and also the time scales I mean, it may be that they'll inevitably merge in Trillions of years but not billions. I don't know eventually they will but yes, it could be billions. It could be billions. Yeah, so Right. So maybe the consensus here is that they they will do eventually but it depends what you mean by eventually Yeah, and But we do know what happens when black holes collide because we've observed it so and our latest detectors Which did so-called gravitational wave detectors which detects? Unbelievably ripples in the fabric of the universe ripples in space and time from the collision of Objects like black holes and now working beautifully and we've seen several occurrences in the universe where black holes have collided with each other emerged and So what we know is that they form a black hole. They lose some energy when they collide But they do form a black hole with an area An air a surface area which is bigger than the two holes that collide and that was a prediction from Stephen Hawking the so-called area theorem And that's been proved so and the prediction of how they collide and how they merge and what you get afterwards is in Absolute accord with Einstein's theory of general relativity Which was published over a hundred years ago and Einstein didn't know that there were such things as black holes when he published the theory He certainly didn't know that we'd ever see them collide together He certainly didn't know that there were ripples in the fabric of the cosmos Although he predicted that slightly later that would carry the information just like light carries the information from distant stars So the ripples in the universe can carry information from collisions of black holes So we've in the last couple of years We've entered a new age of astronomy where we can watch black holes collide to reverse Stephen Hawking's area theorem which seems to have been proved by these collisions now says that if you collide two black holes together, then the the area of the Horizon around the new black hole has got to be bigger than the area of the horizons of the two little black holes And that seems to be what we've seen. What is that thing the event horizon? It's the area around the black hole from which light can't escape So if you if you go into a black hole, which you could do if it's sufficiently big or sufficiently massive you could fall in Through this point this this sort of region of space Around the hole and you wouldn't you could easily fall in and what happened when you fall in is that you could never get out Again, and you couldn't even send a signal of light out of the black hole because the gravity is so strong but the light can't escape and The region from which the light can't escape is called the event horizon or inside this event horizon And that's what you see with the black hole if you could float around and see one And you wouldn't see anything because it'd be black, but you would see this this sphere or this shape in space from which no light would emerge and Around which all the light from the distant stars and the galaxies would bend and curve and be warped So that's a very strange thing the black hole and I should also say we don't know what happens right in the middle So it's called the singularity that's where our physical theories break down and that's another thing for you lot to go and do what probably someone of your generation will work out how To how to do the physics to say what really happens in the middle I mean it it is he doesn't like inflation as a theory doesn't and oh no So but so but but but it's right that so our universe is Accelerating in its expansion at the moment, which is one of the great mysteries that was discovered in the 1990s By a friend of mine actually Brian Schmidt got the Nobel Prize for this discovery. He told me once I don't know if I told you the story before but he told me that he he'd Made this measurement and it wasn't really He's looking at supernova explosions and he'd seen that day the suggestion in the data was that the universe is Accelerating in its expansion not slowing down but speeding up in its rate of expansion and and no one was expecting it So he thought it was just wrong. He thought but he couldn't find anything wrong with his data So he published it and thought well, that's the end of my career. Oh boy, you know, I use quite young That's a good scientist, right, I don't think this is right, but I can't see anything wrong with it I'll publish it Someone else will tell me where my mistake was and there was no mistake and he won the Nobel Prize Wow for that discovery That's the 1990s. So this idea the universe is Accelerating in its expansion the way that it does that is really important Is it going to carry on doing that is whatever's driving that expansion going to change in some way? Which could actually recollapse the universe again. We give it a name by the way dark energy this thing Mm-hmm, but we don't know what it is. I think it's very fair to say But it looks a bit like inflation, but it's way slower. So maybe they're linked. Maybe it's the same kind of thing We don't really know and so it's one of the great mysteries So but it but the universe it looks like the universe is going to continue to expand forever and to continue to accelerate In brackets I am it's really easy to explain actually Dark matter when we look out into the universe. We see lots of things. For example, the speed that galaxies rotate or the way that galaxies interact together or actually the oldest light in the universe called the cosmic microwave background and patterns in it which a Suggestive of there being some kind of particle. So that's like this stuff like electrons and things There's some kind of particle that's quite heavy and does not interact with light So so that's why it's called dark matter You can't see it because it doesn't interact with photons But it dominates the universe five times as much of it as there is of this stuff After which everything we can see is made. So that's what dark matter the best theory for it We see it by its gravitational interaction. However, it's not Shown it's not proven That's the case because we haven't detected the particle and there are experiments everywhere in Underground lamps and so on a large hadron collider at CERN where we're looking for these things But we haven't seen them and so that leaves open the possibility that there's something else going on that we don't understand Yeah dark matters in some sense marginally less confusing in the sense that at least we have an idea of what it might be Whereas dark energy there are people listening to there'll be there are people working on it So there are theories about what it might be, but I think it's further it feels less explicable given what we know than dark matter, but We haven't discovered what we think dark matter might be some kind of particle that is got certain properties and Doesn't interact very strongly. It's like interacts like neutrinos Basically mentioned earlier, so really doesn't interact very strongly, but we thought we might have seen those particles. We're looking for them They would be passing through this room now And so we can build a detector in here and we do that and we look for these particles We haven't seen them. We thought we might make them at the large hadron collider at CERN I think many people thought that we'd see the signature of these things and we haven't done so it could be that we're not right With that picture. So yeah, so it's about 5% matter about 70% dark energy and the rest. So 25% dark matter So we were just less than 5% dip this that's crazy So and stuff we can see so everything we can see in the sky all the gas and the dust and the galaxies and the stars And the black holes all those things less than 5% According to the standard model of cosmology and so the other 95% is just like who something else knows something else Yeah, and so but those are models. I mean, it's important to say that it's interesting because Until so we have a hypothesis which is strongly supported by lots of bits of evidence That dark matter is some kind of particle so it's that's the broadly that's what you find in the textbooks But it's true that until you find it until you see it then you haven't shown it to be correct Are there alternative theories there are and they're not compelling No They all have problems and most of them have problems with that pattern the CMV the cosmic microwave background that we just saw Because that pattern what you're looking at actually in that pattern is Acoustic its wave sound waves essentially in the early universe that go through the plasma of the early universe And they go out and we know what speed they go through that plasma So it's almost like you're looking at a pond and you're throwing stones into the pond And they all land in the pond at the same time and send ripples out Little circular ripples in the pond and they all overlap and that's what that pattern is So we're looking at sound waves going through this plasma and and those those theories Require the dark matter the dark matter fits Well, if it's in there in in this plasma in this kind of soup that this subatomic Particle soup that's the early universe and the way the sound waves go through it fit that idea So that's one thing but the the the idea also came from looking at galaxies and how they rotate and galaxies and how they bend light and And and deform space and time and how they interact together. So there's loads of different bits of information Observations of the universe from the cosmic microwave background all the way through to galaxies and the formation of galaxies and the theories that we Suggest there are these particles around that interact very weakly with light So they don't really interact with light at all, which is why we don't see them, which is why they're dark That's just like a neutrino, right? So so like heavy neutrinos on and actually there was a theory once that maybe they were heavy neutrinos But that's kind of disfavored now. And so so we have loads of kind of different bits that fit This is how you do science You start with a theory and you make a load of observations and you can infer things and you get a consistent picture but Very importantly until you find it until you really find that particle then you don't know And we've inferred it So you might say how do you know it's there, you know, which is a good question, right? I mean if we have now detected this stuff, how do you know and it's from Einstein's theory really so it's from Gravity it's from looking at the way that Galaxies rotate and the way that these sound waves moves through the early universe and the way that universe expands Because the way the universe expands Is related to the stuff that's in the universe so we can weigh the universe By and find out what kind of different things are in there by looking at the way it's expanded and how that expansion history has changed over time So it's all you what what you do with science which is why it's You know, it's true that you can criticize any one bit of it and people will so online You'll see in the comments under this there'll be people saying but about this. What about this? What are they sure and it's true that you can you can pluck away and pick away any piece of it But the way it tends to work is when you have this kind of consensus view of something It's because you have multiple observations that all fits a particular hypothesis And by changing one of them by changing the explanation of one of them You tend to mess the whole other thing up you mess the the wider description of multiple phenomena up you mess it all up So it's quite hard to to find The other theories at the moment that will fit all of those different observations I mean another example will be the age of things is it? You know, it's interesting that You can look at we can measure the age of the earth, right? And you measure from geological processes radioactive dating and so on and you can kind of measure the age of the earth You can measure the age of the Sun in a different way You can measure it by looking at by looking at called helio seismology So you can work out you can measure how much helium is in the core of the Sun and the Sun shines by making helium from hydrogen So by measuring the amount of helium in the core by looking at basically sound waves It's like an earthquake but Sun quakes you can measure how much helium is in there so you can get an estimate of the age of the Sun and Then you can get an estimate the age of the universe by measuring how it's expanding and using Einstein's theory The fact that they all fit with the picture of a universe that's 13.8 billion years old a Sun that's four and a half billion years old a planet that's four and a half billion years old. The fact that it all fits is It's it's quite an intricate model and so you could say well I argue with the The measurements of the age of the earth, maybe I don't like the radioactive dating or something and people will say that But the thing is it's a consistent picture with multiple different observations and same with dark matter So the standard model of cosmology is you have I said about 5% matter 25% dark matter 75 70 percent dark energy It might be wrong But it fits loads of different independent observations, so it's a consistent picture How will the universe end? well, the current best guess or best estimate is that it will carry on expanding forever and The reason I say that is because actually one at one of your great scientists in Australia Brian Schmidt Got the Nobel Prize for discovering that the universe is accelerating in its expansion Which is a great mystery because before that discovery we thought well gravity is always attractive and so it should be we've got all these galaxies in the universe and the universe has been expanding since the Big Bang and So it should at least be slowing down and there was even a question as is there enough matter in it to slow it down? So much that it stops and recollapses again, but this new discovery It's only a decade old or so that the universe is accelerating in its expansion Suggests that it will continue to accelerate unless some new physics appears that we don't understand and so it will just continue to expand forever These are brilliant questions against one of the fundamental questions in modern theoretical physics And it's interesting this idea of the Big Bang created the universe. That's what Einstein's theory says That's textbook cosmology if you like But the current textbook picture is there was a phase in the universe's life before the Big Bang if You define the Big Bang as the hot dense phase from which the universe appeared to sort of burst for 13.8 billion years ago And that phase is called inflation. So what we think happened is that before that the universe was accelerating Exponentially fast it means it was doubling and doubling and doubling in size and the numbers are ridiculous And we think that if you started with the universe that was smaller than a single atom Then it would be bigger by a long way than the whole observable universe 350 billion galaxies in it in Less than a million million million million million millionths of a second for those of you that know scientific notation It's something like 10 to the minus 35 or 10 to the minus 36 seconds. So very rapid Exponentially fast expansion and when that stopped all the energy that was driving that expansion got dumped into space It heated it up It produced the particles of matter out of which we are made and all the things that we see out there in the sky And that's what we see is the Big Bang So that sounds fanciful, but that's standard cosmology at the moment The big question then is well what started the inflation what stops the inflation How long did the inflation go on for and the answer that is we're not sure we don't know and I just say one last thing Some of those theories suggest that the inflation doesn't stop all at once It stops in patches and every time it stops you get a universe And so some of these theoretical eternal inflation theories suggest that there might not be just our universe the bit that we can see But there might be many universes perhaps an infinite number of them and they may be being produced all the time. So that's What to make of that but that's where her current modern cosmology is