The End of the Universe - with Geraint Lewis

thanks, so it's great to be back in RI again. I spoke here last year and this is a fantastic auditorium. I am a professor of astrophysics at the University of Sydney and, as mentioned there, I am a cosmologist. My job is to try to understand the forces that have shaped the evolution of the

universe

from a time when the

universe

was basically formless to the rich structure of the universe that we see around us today, so what I want to do tonight is basically taking all of us on a little trip what we want to do is not take a trip through space but a trip through time and we want to look back first to see how our universe evolved from its birth in the Big Bang to the universe with stars. and planets and galaxies today and then we want to turn around and move the universe forward and ask what destiny has in store for the universe, what is going to happen as this universe gets older and older, so that every journey begins with a single step and before we take a step back into the past or a step forward into the future.

I think it's important to understand where we are, where we are today, what kind of universe we live in, and of course the starting point for that is where we are now and where we find ourselves. We are on the surface of a small rocky planet and it is a very special planet, it is an extraordinary planet because of the thousands of planets that we know we have discovered in the universe and the billions of planets that we believe are out there in the observable universe. This is the only one where we have complete and absolute evidence that there is life on this planet.

Sometimes it's a little hard to see intelligent life on this planet, but there is life on this planet. Well, now I'm going to touch life on the planet. universe as we move a little bit into the future, so it's important to try to understand what we mean when we say life and it turns out that defining life is incredibly difficult when you get to know the details, how you define whether what is living and what is dead and people make rules so this is my dividing line this is the living that is the dead all this on the dead side that seems a little alive and that happens all the time and there are arguments about whether viruses are alive where prions are alive these things are even smaller than viruses and that is how life is defined, that would require another conference and probably a few more conferences and we would be here until almost the end of the universe trying to define what life is but what I'm going to address an aspect of life that, in my opinion, I think is one of the key things that life does if we're going to define something as a living organism and that has to do with energy.

Well, all life processes energy. So what we have in this image here is a beautiful sunflower, that sunflower has captured sunlight and that sunlight has been stored as energy in the chemical bonds within the plant. Creatures appear that eat the plant and they can use that energy to run their own chemical processes in their body and similarly we could eat the plants or we could eat the animals that ate the plants and then there is a continuous progression by which we use and we process energy and that is one of the defining characteristics of life, all the processes of life. energy of some kind and that energy not only drives the chemical reactions in your body but it also drives the kind of mental reactions in your mind when you think well, we all know that when you have low blood sugar it is very difficult to think about it.

Whatever you need energy to run your brain, in fact, consumes a lot of the energy it takes in, so there's actually a very strong link between energy flows and information processing, and every time you run your computer and your computers do very difficult calculations or update Facebook or something like that, it is processing information and you can feel the heat that is generated by processing that information, so if any living creature is going to be sentient and know its environment and react to He, you will need to have a flow of energy to drive that kind of behavior now the main source of energy on Earth is of course the Sun in the middle of the Sun.

Every second 11 million tons of hydrogen are converted into helium which releases energy that takes a hundred thousand years to filter out. through the Sun and then eight minutes to get from the surface of the Sun to the Earth where it gets absorbed by this sunflower or lands on the pavement outside in London and makes the place even hotter, then all life on Earth exists because we have a large reserve of energy right next to us in the universe and we can use that energy and that has fueled life and evolution to this day take away that source of energy you don't have life what we will see is that energy It will come to play a critical role in what life can do as we look to the distant future of the universe.

It becomes the scarce resource. It's what any life that exists in the distant future universe will need to seek out if it wants to. Let's continue living, but let's try to remember our place in the universe, as I said, we are on the surface of this rocky planet, our energy is given to us by the Sun, which is a very typical dwarf star and our Sun is not alone in the universe, but The Sun actually occupies a small portion of the universe with approximately 300 billion other suns in an object known as the Milky Way. When we look out into the universe, we see that there are possibly between a hundred billion and a trillion other galaxies.

There are a lot of stars, a lot of galaxies, a lot of potential places where there could be life, but we have no idea what the frequency of life is in the universe. Life could be very common or life could be extremely rare and all. Our observational evidence is pretty consistent with this being the only place in the universe where there is life right now, so I said this is a special planet, so before we play the game of looking into the future, let's figure out how we understand it. what happened. In the past, okay, and what we know is that people have looked at the heavens for 4000 years and see patterns of stars in the sky and people usually made up stories of heroes, gods and legends to explain the various patterns we see here .

In RI, of course, the important thing is not just the stories that people told but how they came to apply science to understand the evolution of the universe and all of this happened, of course, during the time of the birth of modern science and I will . just this guy appears here, this of course is probably the most famous scientist in Britain, the second famous if you also consider Stephen Hawking, but this is Isaac Newton, in my opinion he should be the most famous scientist in Britain. Isaac Newton existed at the time when there was a single changing view on how we understand the universe and I like this photo this photo was taken from the back of old friend's note there are people in this room who have clearly never seen a old friend not too young but in the old days there used to be a note in the back it was this photo of Isaac Newton and I like this photo because there is a photo of Isaac Newton with this telescope and he observed the universe, he used this telescope to see what was happening now he was not the first to look at the heavens, it is reported that Galileo was the first to look at the heavens and see, when he looked at the planet Jupiter, that Jupiter had companions, that there were moons orbiting Jupiter and that led to this general idea that there must be some kind of order in the heavens and then people wonder if the order in the heavens is similar to the order here on earth and if I understand how things behave here on earth maybe that tell me how things behave in the heavens and so what you start to do is start to dispel the need for gods and heroes by describing what happens in the universe, but what you want are laws of science that tell you how things behave things behave now.

The other reason I like this image of Newton There is his book Principia, where he essentially laid out the key ideas that became classical mechanics, how things react to forces, but he also described the law of gravity and image that we have in the background is a kind of description of Newton. how gravity works by basically keeping the Earth in its orbit as it travels around the Sun, and of course Newton's big idea was to realize that the force that picks up an apple, rips it off the tree, and throws it to the ground is exactly the same force. which keeps the moon in its orbit around the earth the earth and its orbit around the Sun and the moons of Jupiter in their orbit around Jupiter so you could write mathematical equations and you could make predictions you could predict where the moons of Jupiter will be because they simply They obey the laws of science, it is not necessary to introduce gods or mythical beings anywhere because everything is there in the equations.

Now some people don't like that which leads to a very sterile universe, of course, where everything is governed simply by mathematical equations. but at least it means it's predictable, we know where things will be now, in the 400 years or so since we had Newton, the only thing that's changed is that we've gone deeper into our physical laws, we understand the physical laws that govern the universe very much. more detail and we have looked deeper into the universe and what we have done is develop new telescopes that can see further and further into the distant cosmos and this image here is a telescope that is currently being built in In the southern hemisphere, this is the Square Kilometer Array that was built in South Africa and Australia.

It will be a radio telescope, so it will only be able to see radio waves and it will be basically a one square kilometer collecting area, so we will be able to see some of the faintest things that exist in the universe, but in addition to a set of square kilometers , we have many giant optical telescopes, there are telescopes in space that look at X-rays and gamma rays and look at microwaves, etc. What they have revealed is a universe, which in my humble opinion being a cosmologist is quite exciting, so what we have here is an image that was made by the W map consortium.

W map is just to say that it is in space Wilkinson and The Microwave Anisotropy Probe its job was to look deeper into the universe than any other telescope, but what we have here is a picture of our entire universe as we understand it well, both in terms of what we can see and what we can see. We can understand in terms of physics what is happening in the universe now because light travels at a finite speed. When you look at increasingly distant objects, you are looking further and further back in time and what we have is a picture of our universe.

From today as far as we can see and what we can see is that the universe has changed and evolved throughout its life, the first important thing is to realize that our universe has not existed forever, the universe seems to have been born in an event now known as Big Bang which occurred approximately fourteen billion years ago so our universe has a finite age but looking back we see that the universe in the past was different than the current universe so today around us we see all these stars and galaxies and like If we look back in the past, we also see stars and galaxies, but they are different from today, they are less formed and as we go further and further back, we reach a point where we do not there was no galaxy and we can push. go back even further and we come across the very beginning of the universe, so in terms of the evolution of the universe, you can go from left to right, on this side you have the Big Bang, the universe was filled with material or spread out smoothly, then the laws of physics.

It acted for about fourteen billion years to give us the universe that we see today, so there are a number of key features that people like to talk about from birth itself, which is something that we don't understand, we don't yet have the laws. of physics to understand the very birth of the universe, but after that, the evolution of the universe through this rapid expansion known as inflation, through the general evolution of matter into stars and galaxies, everything seems to be very much described. precision by the laws of six, so in fact, one of the things that we like to do and that is actually a very important part of modern astrophysics is that we like to build our own universes, and I have PhD students working for me that they generate universes before breakfast, well, in general, not because no one ever got up before breakfast, so early in the afternoon, they will generate a universe, so what do I mean by that?

What do I mean by generating a universe? Well, as I said, we believe that all the processes that are taking place in the universe are simply governed by the laws of science, so if I take my laws of science, my laws of physics, my law of how it works gravity, how gases work, how nuclear physics works, etc, etc, and I translate those equations into computer code and I give the equations to a computer and I say: the computer solves theequations for me because that's what good computers are good for. In fact, I can generate a synthetic universe, so in the next type of animation I will show you the results of one of the great universe simulations that were carried out. made by a person who calls the group Lustrous essentially what you do is simply say I'm going to take a large volume of the universe, this volume is billions of light years in diameter, much larger than our own galaxy.

I'm going to put stuff in there. and distributed smoothly like it was after the Big Bang and then I'll press go and you can solve all the difficult equations and you can tell me what the universe looks like so when the best things have happened like strong conversations you can just put on the movies and you can have a cup of coffee when the movie ends and you say it wasn't that beautiful, right, so what we're seeing here is matter moving around in the early universe, so it was originally distributed smoothly. Gravity started to act and brought matter together and matter just doesn't fall in one big lump, they fall. in several clumps connected by this structure known as the cosmic web, within these clumps the gas can gather and when that gas accumulates it can form stars, so where these large clumps are obtained is where galaxies are formed, so that within these galaxies we have stars. burning up, but stars evolve over time and eventually giant stars basically run out of fuel and then they explode and hopefully we shouldn't explode at any point, we're in the nick of time, okay, what you have there is a giant star that has been burning elements in its core hydrogen to helium helium in carbon carbon in oxygen to add all those elements are trapped in the heart of the star, but for life having those elements in the heart of a star is pretty useless, you need them It's spreading throughout the rest of the intergalactic medium or interstellar medium, I should say, and for that material to be recycled into the next generation of stars, that's what happens when massive stars explode, the stars explode and spit out the heavy elements. that are needed for life, so it's a little sobering to think about this, you know you look at yourself and you think this is me.

I'm nine years old, but I'm made of water, mostly water, the hydrogen in that water where the hydrogen was formed. in the Big Bang that hydrogen is 14 billion years old the oxygen in water that oxygen was formed in the heart of a large star and in fact the elements that make me up have probably passed through the heart of several stars over several generations of being material formed spit out recycled being spit out and recycled and what I always like to mention is that items like this the jeweler told me it's gold okay but gold stars don't create gold when stars burn gold it's just created when stars die, that's what gives you the conditions that can squeeze atoms so tightly to give you gold, so I said if you want to be romantic then you should say that a star had to die to give us this ring, right? , but we are implicitly tied to the evolution of stars, there is no way we could have had life in the early universe with just hydrogen, helium, there just isn't the complexity to have life, so what we have, of course, is our image today. today this is a beautiful photo taken in Chile this is the VLT, the Very Large Telescope, we are not very imaginative in naming it, it says that the ELT has come in an extremely large telescope.

I kid you not, there is also an overwhelmingly large telescope, we should spend more. I've been thinking about these names for a while, but anyway the VLT exists it's in Chile it's for eight meter telescopes all the good telescopes in the world are now in Chile because they have some of the clearest skies that you can reach very high up and this is a beautiful view of the center of our own galaxy, the Milky Way, well, if we were in Chile, your eyes don't see as well as this, but the view is quite spectacular, but we are on a rocky planet orbiting a fairly typical small star in a reasonably large galaxy that is one of many hundreds of billions or trillions of other galaxies in the universe.

Now one of the problems when you think about evolution, let's go back to the evolution of humans, is that we often make the mistake that here we are here, we are now and therefore we are the pinnacle of evolution this must be the end point how can it get better than this? true, but of course we are wrong, humans are still evolving and changing all the time evolution hasn't stopped because we suddenly discovered the iPhone. Well, we're still evolving there and there are different pressures on how things evolve, but we're still evolving and it's the same with the universe.

You would think that holding this planet is quite comfortable and this universe can. It looks pretty pretty and photogenic maybe this is the pinnacle of the universe this is how it will always be from now on how can it get better? Unfortunately this is not the pinnacle of the universe and on some level this is the beginning of a long decline, so on that happy note, let's change our tune and start looking to the future. Now, to understand the future history of the universe, we have some limitations that we are going to have to recognize when studying the evolution of the universe from the beginning.

From the Big Bang until now you can have a telescope and you can see what happened in the universe to guide you which processes were important, but unfortunately we don't have any telescope that can receive light from the future. It would be beautiful to see what future. universe is going to do because it would help you make a prediction because you can see it well, so we can't, so on some level we are working in the dark, right, we are going to make predictions and there will be some level. of uncertainty because we don't know perfectly everything about our current state of the universe, but there is a bigger problem and the bigger problem is that we don't know our laws of physics perfectly, we know that we have some very good laws of physics. we have quantum mechanics, you know, if your iPhone wants to work, it's based on quantum mechanics, we know that to a very high degree of precision, we also have a very good description of gravity that Einstein gave us again.

The GPS works, it gets you to the point. To know one centimeter on the surface of the Earth you have to worry about Einstein's theory of gravity for GPS to work. The only problem we have is that when we have conditions where we have to worry about quantum mechanics and gravity together, they just don't fit. together mathematically, so there are going to be places that we go into the future where this uncertainty of how these types of combinations intertwine is going to cause problems, so as we go out into the far future universe we're going to get a little more speculative. and I'll try and there won't be a flashier speculation meter as we go, but in near times pretty good, in distant times things are going to get a little more complicated, so what's the first thing that's going to happen?

So what we're going to do is We move forward and we will move forward in steps, but the steps will get bigger because the universe will have different times when things are important and they tend to be spaced out in bigger and bigger steps. What are we going to worry about right now? The next billion years, as mentioned, Brexit might be resolved on that time scale or it might not, but what's going to happen well, the first thing we need to think about is essentially the end of our galaxy, the Milky Way. image in a few billion years will disappear then, what do I mean?

Well, here is our galaxy, the Milky Way, it is a spiral galaxy, there is a bulge in the middle, stars that rotate around the outside, our Sun is one of those stars that rotate outside the Sun, it takes 250 million to orbit the center of the Milky Way the problem is that the Milky Way is not alone in the universe, it inhabits this part of the universe with two other large galaxies, one of them is called m33 or Triangle, it has 1/10 of the mass of the Milky Way We care about the other m31 is Andromeda, which is about the same size as the Milky Way and Andromeda is approaching us at half a million kilometers per hour, which we do the math quickly, which says that in about 4 billion years will be here, so what's going to happen is that Andromeda and the Milky Way are going to collide, so we saw there that it was the initial collision that the stars started to rip them off, so gravity pulls the stars in and starts throwing them away. outwards, now the Sun could be one of those stars that ends up being ejected from the Milky Way, so the collision has just begun before continuing.

I should point out that I have a small time scale up there and I've tried to use words to describe time, a billion years makes sense, we all know what a billion is, we all know what the national debt is, etc, etc, so We can understand billions, but we will have to go to bigger numbers, so there is scientific notation of 5 times 10 at 9 years all it means is 5 followed by 9 zeros, that's five billion, okay, then you'll see. numbers ^ something just add so many zeros at the end and just say wow, that's a long time, okay, so we had this initial collision, so if you saw that collision, the two galaxies got closer, some stars broke off but then they separated, so it will be exciting why, because in the collision the Milky Way galaxy shakes, okay, it shakes vigorously when the Andromeda galaxy approaches and what.

What the shaking does is it causes the gas clouds inside the Milky Way to collapse. That gas is what makes a lot of stars, but if you shake it up and make them all collapse at the same time, what happens is you make a lot of very massive stars. stars very gigantic stars such massive stars are hot, they have a great brightness Lu and for a moment our universe, our local area of ​​the universe, will look like a Christmas tree, our sky will be completely filled with these hot blue stars that shine somehow way, but the collision has not ended properly, gravity started to do its thing, the galaxies will come back together and hit each other again and you will notice that as they hit each other they get closer and closer, they are losing energy because the stars are being ejected, but they are now merging, the other thing that happens is that some of that gas, instead of becoming stars, swirls towards the center of the resulting galaxy that formed from the merger of the Milky Way with Andromeda.

I'm going to have to apologize in advance, this object is known as Amida milk I hate the name with a passion I have to use it I'm sorry it's part of my union card I think there's going to be a big black hole in the center of this remnant galaxy the gas is going to fall towards that black hole and that gas as it falls starts to spin and collide with other pieces of gas and gets very hot, so the center of this milk galaxy or medium algometer will start to glow, it will shine very, very brightly. , okay, so we won't do it.

We just have this Christmas tree of bright blue stars in the sky. We'll also have this very active region around the black hole shining brightly and firing at that matter. Here you can see a big jet of matter coming out, so that's very exciting. so it would be good to see it. I would like to stay a few billion years to see this collision, but there is a problem and the problem is that it will all end too quickly. what do I want to say with that? massive stars we have in the Milky Way are there James Dean stars some people know who James was nee live fast die young Amy Whitehouse other than that my cultural references are out the window I'm afraid giant stars live fast die young so They burn up for 10 million years and then they explode, they disappear, so the Christmas tree effect will disappear in a similar way to the gas that, floating in the middle of the well, is eventually devoured by the black hole, so active galaxies are the part that shines very brilliantly that disappears and what we are left with is the rest of the crash it is really boring the two beautiful spiral galaxies Andromeda and the Milky Way that were in the beginning have now completely disappeared, we are left with this amorphous mass with a rather horrible name, it is well that's a bit sad, one of the nice things about being an astronomer is looking up at the sky and seeing the structure of the Milky Way in this future galaxy after the collision, or will we be in it and just have a uniform distribution of stars all over heaven or we will be outside.

I was spat out and we looked back at an amorphous mass, but there's more to worry about, so now we've moved on, now we're. Headed about seven billion years into the future, as I mentioned, these galaxies collide, but one thing that interests me is that the stars are actually very small compared to the separation between them, so we'll take two hundred billion stars. Thestars crush them together and no star will collide with another. Okay, so our Sun will survive the collision. The Sun will pass over all the other stars. I said it might end up somewhere interesting and it might end up somewhere not so interesting, but Now there are seven of us, approaching seven billion years in the future, the problem is that the Sun is currently 5 billion years old as of 5 billion years and what I mean by the Sun is 5 billion years, I mean for 5 billion years.

The Sun has converted hydrogen to helium in the core of the Sun and we know how much hydrogen is in the Sun, so we can estimate how long the Sun has left until it uses up all its hydrogen and it is approximately 5 to 6 billion. years, so while the Sun might survive this collision, it will run out of hydrogen fuel. That's what I said, the death of the Sun isn't exactly death, the Sun doesn't die nice and quietly when the Sun runs out of hydrogen. it sort of rearranges its internal pieces and tries to start burning helium into heavier elements instead of hydrogen, which causes the Sun to swell, swell, and cool, so it goes from being a typical star. yellow to be a red giant, but it continues to swell and swell. and it swells, eats mercury, eats Venus, gets brighter and brighter and at this point the flow of energy from the Sun rips away the Earth's atmosphere, boils the ocean and completely sterilizes the surface, this is reasonably inevitable, okay, this That's what's going to happen.

When the Sun runs out of hydrogen, we are eventually not quite sure how big the Sun will become. There are some who think that the Sun will actually become larger than the Earth's orbit and will completely swallow the Earth. totally and absolutely destroyed and the Sun could even swell towards the orbit of Mars. After that point, the Sun goes through a sort of mid-life crisis where it shrinks, grows, shrinks, I think we all know what happened. until the middle ages, the right shrinks and grows, but eventually the Sun becomes unstable and removes its outer layers and the Sun is no longer there if this is the only planet in the universe where there is life and we have not left the surface by then that the end of life in the universe on Earth will not survive now, it is 7 billion years away, so we are hopeful that on that time scale we can put our differences between us and work together and think that maybe it would be a good idea to leave the planet before the Sun completely evaporates.

OK, it may take a few billion years of discussion to get to that point, but this will be necessary if life is to continue. He can't stay for long. A single star, right, because stars just don't live long enough, life will have to move from one star to another, so hopefully we'll keep our fingers crossed that life will spring up among the descendants of humans or such. maybe the cockroaches. They will develop technology that allows them to travel to other stars. Well, that's the only way life will be able to protect itself as the universe evolves.

Now the technology needed to travel to the stars is difficult. We know we can't do it in the future. At the moment it's okay, we just don't have the technology, but like I said, there's a long time between now and a few billion years, so I hope that kind of thing can be developed, but you might think carefully if I'm going to travel. between the two. individual stars in our own galaxy, the Milky Way, so how about I go big? How about I just wander the stars around here? I think about jumping between galaxies, okay? So you know, I have billions of galaxies in the universe, they are quite a variety. at a great distance, but again, as technology gets involved, it might be possible for us to travel from one galaxy to the next galaxy, and the more life spreads, of course, the more chance it will have of surviving in the future universe.

The big problem is that if you're doing that, you'd better start relatively now, why, well, because it won't be possible when we get to the next step, so now we're about a hundred billion years away, why is it okay? As I mentioned at the beginning? What we have realized is that our universe today is dominated by this strange thing that we don't really know what dark energy is. Well, we know it exists because we see the expansion of the universe accelerating, so there is something there that is causing the University. of that, but we don't know what it is, but it's dominating seventy percent of all the energy in the universe, it seems to be in this dark energy and as time goes on that percentage increases, it's still very close.

I'm not too far away. the future will effectively be one hundred percent what that does is drive expansion faster and faster, which means that distant objects move away from us faster and faster until eventually they are moving so fast that any light signals they try to establish will never let's get here because the universe is expanding very rapidly between the distant object and us and that means that basically when we get to about a hundred billion years, what's going to happen is our distant universe is going to expand. begin to disappear from view, so first the most distant galaxies that we see will basically freeze and then become invisible and then the closest galaxies until, in a hundred billion years, all we can see are nearby stars of us in our leftover galaxies, everything else is now.

It is moving away from us so fast that we will never see it again, so any species or civilization that arises at this time in the universe will never come to the conclusion that we live in an expanding universe, why does everyone grab their telescopes and they look at the sky and said what do we see or do we just see stars in the nearby universe and everything else is inky blackness there is no evidence that there is expansion no, there will be no future Edwin Hubble, who measures the redshift of galaxies because no there will be galaxies to see.

That also means that life is then isolated, now it is trapped here in this galaxy, millimeter, or in the other galaxies, but now they are separated and will never have contact again, so life will have to deal with what's happening here. If you're going to survive in the far future of the universe, then what's next? Now we are going to take another big leap, we are going to go from one hundred billion years to approximately ten billion years. Well, then the universe stays there. evolved into what we are going to see now is that we are going to see the remnant galaxies of the Milky Way and Andromeda when they merged and, as I said, when they merge they create many hot blue stars that live for a very short period. time before exploding, so all blue stars live for ten million years and then explode and disappear, then stars like our Sun reach the end of their lives, so they get older and older and die now, unlike the Milky Way which has a lot of gas and can produce new stars, this leftover object that used all its gas in that explosion during the interaction, so no new stars are born and all you have is this continuous death of stars as they get older and older and older.

The fact that there is an interesting relationship with stars is that the larger the star, the less it lives, so large stars live a few million years, stars the size of the Sun live a few billion years, and The little stars, these little red dwarf stars, live for billions of years, so what we're going to have is the stars are continually dying and our portion of the universe is going to get redder and redder, as these little faint ones Red dwarf stars are the only things left. Well, of course we will be. aging and galaxies will continually fade over time now you could say okay, well, this object that collided produced many hundreds of billions of stars, all moving, you still have a lot of these awful ones, you think that's not so bad for life. but red dwarfs are not friendly stars, which we have recently realized that red dwarf stars, although they look nice, quiet and calm, are actually quite violent and active, placing these stars instead of just staying there and transmit our energy.

Over their billions of years, what they do is they often have large solar flares, they have large explosions of energy and those energy explosions are believed to continually sterilize any planet that is orbiting that star, so it will be very difficult for life to exist. evolve again. planets orbiting red dwarf stars, but if life has survived from our period in this distant part of the universe, they will have to rely on the energy generated by these red dwarf stars to keep functioning now, as I mentioned, these stars are small. Stars are faint and so don't emit much energy compared to a star like the Sun, so any life in the future part of the universe will have to work very hard to become very efficient at harvesting energy and using it. and there have been a number of suggestions about what you would do.

I'll post this image because I think it's pretty. This is a Dyson Sphere. Now a Dyson Sphere is a simple idea. You have a future civilization that can do a lot of difficult things. We won't talk about how they do it, we'll just pretend that they can and they find a star and they want to be very efficient and use the star's energy, so instead of sitting on a planet, you build a kind of big enclosure around that star. That way you capture all the light from the star, you can use that light from the star to direct your life, and you can spend the residual heat on the universe, so that's essentially what you'd probably want to do with a red dwarf star, right?

If you have a red dwarf star, it has very little energy, but if you can try to capture all that energy in one of these Dyson spheres, then maybe you can continue to power life in the future, which is the next thing you'll need to do. It is possibly a little more radical and the big problem is that this is highly inefficient. I'm not just talking about me, okay, I'm talking about all of us. We need to assimilate and all the things we need to do to stay alive are wasteful in terms of energy, so energy is now becoming a scarce commodity in the universe and you might decide that essentially you might want to eliminate it. biological forms of life and move to a more efficient form of life which is effectively a computational electronic form of life.

Now, of course, there are some problems with all that. Number one, we don't know what consciousness is, so how can you take consciousness and put it in a computer and say there I am is an unsolved problem, but people think this is a possibility once computers become smart enough and fast enough that maybe you could have the equivalent of consciousness in a computer and that consciousness compared to the amount of energy we need to keep going would be highly energy efficient. Well, you would need a lot less energy to run a computer on you rather than on you, so there could be a move away from real physical life towards a more electronic life. this sees the realm loved by philosophers, okay, they love to talk about these things, he pointed out that if this is the case that in the future we move to an electronic way of life that is much more energy efficient, then it would be very easy. generate a large number of individual conscious life forms on your computer because they are very cheap compared to biological life forms and they say that throughout the entire history of the universe, the most numerous life form could be computational life in some moment close to time.

When we talk about how the universe is now dominated by red dwarfs and that we are indeed just at the beginning of life and most of life is yet to come, other people respond and say well, maybe we are the computational life that is to come. runs on a computer. around a red dwarf star, which makes you think that if this is synthetic reality, what was real reality like? Let's not worry too much about that now, so life will have to do something radical if it wants to be able to do it efficiently. use energy and survive in the future, but again there is a problem: we are going to go by a factor of ten to ten billion years and there will come a time when there will be the last star in the observable universe, there will be a star. fits well and that star, once it's about 100 billion years old, will run out of hydrogen in its core and will go back through this kind of solid internal reach and try to burn helium, but these stars are small, so they settle for a very short period of time and they become a blue dwarf star for a very, very short period of time until, if they essentially just do it, this is too difficult and they give up,so the nuclear reactions that power the star basically stop and what happens then? is that the star shrinks because gravity wins, there is no radiation pushing outwards, so the star shrinks more and more and what is left is a white dwarf and a white dwarf is a dead star, it does not generate new energy, all it does is sit there and cool, okay, then it cools from white to visible to infrared to radio and then it effectively disappears so what we have is we're going to get to a period where our universe is just going to have these dead hearts of stars floating around and there will be billions of them, but there will be no more starlight.

The only energy we will get will be from these hearts of dead stars. Life is going to have difficulties. Even a Dyson Sphere around a dead star is going to capture very little energy. Here we come across areas of unbridled speculation. If you're going to have life in this universe, you're going to have to look for energy wherever you can find it and maybe instead of having life concentrated in individual Dyson spheres, you'll spread it out into something that looks like a cloud now, it's actually an interstellar cloud in Our own Milky Way Galaxy is not a representation of a cloud of life in the future, but it is an idea that people have had is that maybe life spreads out and takes bits of energy where it can. and he uses it to feed himself and it is not a new idea.

There is a book by Fred Hoyle, who was one of the greatest astronomers of the last century. The British astronomer called the black cloud, where he had the idea that these clouds of interstellar gas believe that they might be thinking about beans, they have very slow processes in which they somehow send information back and forth and feed into our time. approaching the stars, that's how the problem started in the book. This black cloud comes to our Sun to get more energy, but it could be that in the future our life could spread out and take all the little bits of energy scattered around and continue to propel itself, so maybe so, now we reach a point at which all our stars are dead, what is left to the universe.

Well, now we have to worry about something fundamental and that is the stability of matter. This table looks pretty solid. I think we'd all be quite surprised if this table suddenly evaporated into nothingness before our eyes. Well, we believe. of matter has been a long-lived solid object, we now know that matter is not purely stable because we have radioactivity and one element can be made to change to another element so that uranium can decay into other elements through radioactive decay , but what are the bits that Atoms are stable on very long time scales. So what we're going to do now is take a really big jump and here we are, in 100 billion years.

We're going to jump to 100 not million years, which is apparently a word, so we're going to jump from ten to thirty. and two years and what we're going to do is think about an atom, so what we're going to do is We're just going to zoom in on a single atom here, okay, so everyone remembers high school chemistry in high school physics. high school. Yeah, that wasn't very enthusiastic anyway, let's try to properly recapitulate what we have in an atom. We have electrons moving around the. outside, a kind of clouds of electrons that move at very high speeds, electrons are small things, they weigh almost nothing, but if we continue to descend further and further and deeper and deeper into the heart of an atom, what we will eventually find It is the atomic nucleus. the scales here are incredible the scale of an atom to the scale of a nucleus is the same as the scale of a cathedral to the scale of a fly, okay, that's how big the nucleus of each of your atoms is and the rest of your atoms. empty space so most of you are just empty space your mass is in all the nuclei in your eye in your atoms when we look at an atom we see that it is made up of a few particles we have two of them we have the colored neutron Blue is called that because it is neutral and the proton is red, which carries a positive charge and it is the protons and electrons that interact that keep the atom together, what keeps the nucleus together is that yellow substance that is the strong force, therefore what the strong force maintains everything. those protons in this very tight beam in the center of your atom now, if I take a neutron and put it aside and wait, after about 15 minutes, the neutron decays, the neutron will become a proton, an electron and a neutrino, so it will decay and it can do that through Einsteins equals mc-squared neutrons are more massive than protons, so there is enough energy there for the neutron to become a proton, plus some other things now if we take a proton and put it next to the protons.

They have less mass and if we do the calculations concerned with quantum mechanics, it seems that the protons should stay. If I put a proton in there, it should stay there forever, except again there's a problem with that and the problem is that there is matter in the universe. Why is that a problem? Well, when we use our laws of physics to predict the early universe, when it was born, there should be equal amounts of matter and antimatter when the universe cooled the mantle, the matter and antimatter annihilated leaving no matter in the universe. Nowadays, however, when I look around this room I see a lot of matter, what I looked at through a telescope I see a lot of matter, I don't see a lot of antimatter, so something happened in the early universe, which means there was more matter than antimatter and so what?

What we think is that there was an additional force that we don't fully understand, that kind of treated matter, different antimatter that produced more matter in the universe than antimatter, okay, that's very good, the important thing is that if that force still exists . so it has a consequence and that consequence is that protons should eventually decay and we have tried to look at proton decay and we don't look at it by taking a proton and looking because that would take a long time, it takes a lot of protons. and you stare at them and look to see if any of them are disintegrating.

We haven't seen it yet, but it is believed that on this time scale of ten to thirty-two years the protons will decay. I'll just give you a little illustration, so here's what It looks like the proton is not a fundamental particle, it has quarks buzzing around inside it, but after ten to thirty-two years, two of those quarks will interact through this unknown force. , okay, so wait a long time, eventually this force will activate and the quarks will interact with the proton. It enters a state it has never been in before and decays into two photons flying in one direction and a positron flying in another, what that means is that on this time scale of 10 to 32 years the matter decays. will melt well.

All the atoms here will constantly disintegrate, so if I had waited long enough, this desk would have evaporated. You would have to wait 10, over 32 years, and that's quite a long time, but ultimately that's the fate of what will happen to you. matter in the universe now life could try to hold on to that energy and carry on but things are now starting to get difficult you can pick up these little bits of energy and you can use them to power your life but then you realize that your Protons themselves are also decaying, so then you will find a way to produce new protons because they will last a long time, but to produce new protons you need more energy, so where do you get the energy so that there is a source left?

We haven't really mentioned them much, but they are black holes. I mentioned that there was a large black hole in the center of the Milky Way and that other black holes form when stars die, so you create these black holes, they are completely collapsed massive objects. at points, they have very strong gravitational fields and therefore you can extract energy from them. It's okay, you can drop things into them. Think about it this way. If you have a black hole. I have a fishing rod. I have a rock on the end of the fishing line. I drop that stone and it falls.

The spindle rotates. You could extract that energy and turn on the TV and watch the cricket or something, but there are many ways to extract energy. black holes and they will still be there in the dark, so you might come up with a method to use that extra energy to sustain life, except of course there is a problem and the problem is the ghost of Stephen Hawking, why well what Stephen? Hawking is famous in terms of his scientific work, he is famous for looking at black holes and linking it to quantum mechanics and what he showed is that black holes are not really black if you take into account quantum mechanics at the edge of the black hole .

They emit small amounts of energy, in small quantities, but over time that energy that is emitted removes part of the mass from the center of the black hole, now on immense time scales of 10 to 100 years, a large black hole like the one that is in the center of the Milky Way will begin to lose enough energy to begin to shrink very quickly and what happens is that if there are black holes in the universe, they suffer from what is known as Hawking radiation, as they shrink, they emit more energy and as they give off more energy they shrink even more so they get this feedback from the runner coming back, running, fleeing which essentially gets them to a point and then they explode with all their final masses released in the explosion and this will happen to all black holes at all times.

Black holes will emit this Hawking radiation, so there will be continuous random bursts of energy in the universe. Now, if you are a creature and live in this distant part of the universe, perhaps you can harness this energy. while the black holes disappear, but I think it's going to be very, very hard work, okay, very, very hard work and effectively what you are doing is postponing the inevitable because once these black holes have evaporated and They have gone once all the stars are dead and their stellar hearts have dissolved nothing is left okay there is no matter in the form of stars except there are just electrons and positrons buzzing around there are no energy sources just this bubbling photon soup. the universe, so the universe reaches this beautiful state known as heat death of the universe and what that means is that we have reached a point where there is no usable energy left for life, this is probably the case, since we probably as far as life goes. we're going to be able to push it out into the universe now we don't want to end on a sad note because we've also entered the realm of speculation and speculative physics, so let's be speculative on the positive side, right? positive about life in this universe, but we can be positive about the universe itself and there are many ideas that if we really stretch the age of the universe from 10 to more than 2000 years, the universe could manage to change its points.

I mentioned that there is this dark energy in the universe, that this material is there and this energy associated with space, but there are a lot of ideas that that energy could decay and go from one energy state to another energy state and if it does, so that The release of energy as the universe essentially changes, this energy state will give a new burst to the expansion of the universe. Well, it'll be like when you open a bottle of sparkling water and you get all these places where the bubbles form nucleation sites. that is where they believe it will happen to the universe that in individual places in the universe there will be this change of energy and you will get these rapidly expanding patches of the universe and these rapidly expanding patches would effectively be new universes now again speculation runs wild.

I don't know what kind of universes are going to be created, they could be a completely different universe than ours in terms of the laws of physics and how the universe is made up of matter and radiation, or they could be like ours and the cycle could begin. again, you could form matter from this reborn universe that falls into each other, giving us stars, the Stars evolving, and giving us new bursts of life in any universe that follows this one, which is a reasonably happy ending in its name anyway. I'm going to end essentially. with a quote from one of my favorite authors, so Douglas Adams is right and there is a theory that if anyone ever finds out exactly what the universe is for and why it is here, it will instantly disappear and be replaced by something even stranger and inexplicable, we may never answer the deep philosophical questions, but we may live in a universe that is replaced by something strange and even more inexplicable, but the line that really got me when I read this was the following.

There is another theory that This already happened and that this universe itself could have been born from the death of a previous universe and we may have these endless cycles of unity in life from infinity in thepast to infinity in the future, so it's almost the end of the Sonic of the Buddhists. But that was the same positive note. I ended up putting up a picture of what the Earth will look like in about seven billion years and I ended up there, so thanks.