 Alright, our next speaker is Dr. Ethan Sibo, who is an author and columnist. You may have read some of his popular science communication on boards, for example, where an iFright person is working, but he also writes books. He is an author and he has this book for sale here right now. You can get an assignment. It's called Beyond the Galaxy. How humanity looks beyond our Milky Way and discovered the entire universe. Speak to Ethan afterwards if you would like a copy. Please join me in welcoming Dr. Ethan Sibo. Alright, everybody in the back, can you see my face killed? Thank you. Alright, so the question portion of this, the quiz portion is over. I am very much in the, I am just going to give you all the answers. So many of you have learned a lot of things about what has happened in the universe so far. We've had 13.8 billion years of it being pretty good. And I'm going to spend the next 15 to 20 minutes giving you the entire rest of the story. So if you would like to know where everything is headed, let's see if we can cover it all. And here we go. So, wait, wait, this is going to work, right? Okay, so here's what we're going to talk about. I'm going to go real quick and give you what the universe actually is. If you do not know what the universe is, that's okay, we're going to cover that first. Then I'm going to talk to you about what the possible things are, what we observe, what we think is going to happen, what the things of planets, stars and galaxies. And finally, what that means for the entire universe. If that's all a lot, you don't have to remember it, I'm just going to give you the answers. So what is the universe? Sarah showed you a great picture of a telescope called the Sloan Digital Sky Survey. This is a result from the Sloan Digital Sky Survey. And if you don't know what it is, it's because you've probably never seen anything like this before. What this is, is you know that the Milky Way shines through the galaxy. If you look at the North Pole of the Milky Way, you don't get any of the Milky Way's stars in the way. So what the Sloan Digital Sky Survey did was it looked in that region of space and everywhere it found the galaxy, it said okay, I'm going to take some data there, that's a point. This is an image of 400,000 points from looking at the North Pole of the galaxy. Every point in this image is a galaxy. And what you see is that some points are big clusters of galaxies. Some points are big voids where there are very few galaxies. And you get this sort of weird web-like structure. If you take a look at our theory and what we predict, this is a cosmic theory of what we should form. So the answer is we should get a web-like structure, we see a web-like structure. That's what the universe looks like today, where you have these big nodes, you should have big collections of mass, that's where gravity wins the most. You get thousands of Milky Way-like galaxies all together. Along these little filaments in the sparse regions, you get little beads of galaxies, little tiny groups and clusters like us, where we've got us and Andromeda and about 50 or 60 like little monsters. And that's it. And then you have these big voids, these are the big cosmic losers. They give up all their matter to everyone else. You don't form stars or galaxies there. And this is weird because most places in the universe are like that. Most places in the universe are these big empty places. You are very, very fortunate to be in one of these little matter clumps where you're actually on a planet. If you would say, what's the average density of the universe? If you took all the matter in the universe and you smeared it out, and you say, what's the density of that versus what's my density now? It's a one with 30 zeros after it is how much more dense we are here than the average. So that's pretty good. Alright, what else is out there? So if you look at just a narrow region of space, right, you would say, oh, like there's galaxies here. And you would look at this image and you would say, yeah, there's like big galaxies and then there's like small galaxies. And that's what it is. That's right. That's totally wrong. What am I doing here? No, these galaxies are pretty much the same size. The ones that look smaller are just further away. So that's why what Sarah showed you, if you looked farther and farther back, right, at that big Hubble Deep Field image where she showed you a couple of stars, that's just a tiny fraction of this image of something like this, where you look super deep and you can see the farther you look, the finger you look, the more distant an object you can see. So it's easy to see the close ones because the light doesn't spread out as much, but the farther away you go, the harder it is to see. But everywhere we look, we see stuff. We see galaxies. This is something we see on a much smaller scale. We see individual stars with solar systems around them. This is not our solar system. This is the trackest one solar system about 40 light years away. So this is a new discovery. Since the 1990s, we've begun finding planets around other stars. And what we've learned, surprise, surprise, is that most stars have planets. And most stars have planets that are different from the ones we have in the solar system. Most stars will have either planets that are like gas giants that are close to their star, or they will have planets that are bigger than Earth, but smaller than the gas giants we have here. Our solar system is just one possible outcome of a huge diversity of stars. So our universe is full of stars and galaxies with these heavy-element planets and chances for life. That's the big lucky thing in our universe, is that we have all of these complex atoms and molecules that come together and they make interesting things. That's what we are, is we're an interesting thing. This is great because the universe wasn't born with us. The universe wasn't even born with the right ingredients to make us. But things unfolded in such a way that here we are. There is a whole great cosmic story about this, about how the Big Bang happened and everything expanded and cooled and you form neutral atoms when it cooled enough. And these atoms came together under the influence of gravity to form the first stars. And the stars lived and died and exploded and put these heavy elements back out into space that formed the next generations of stars. And galaxies merged together and after 13.8 billion years here we are. That's background. We make stars, we know that. Stars live and die. The universe has expanded now anywhere we look. 46 billion light years in any direction. Which is interesting because I told you the universe is 13.8 billion years old. You guys know nothing can move faster than the speed of light and I tell you now that the universe is 46 billion light years in any direction. Does my math add up? Okay, this is the number one question I get writing about cosmology on the internet. But the way it's normally asked to me is, you can't even do math. How does that happen? The answer is because space itself is not a static thing. If all we had was like, oh we got space here and there it is. And now we're going to have a big bang and things are going to expand out at the speed of light. They'd be 13.8 billion light years away. But space is something that can expand. Space itself can expand. That's an important thing to realize. It's not like I just threw something away from me. It's like I have a moving walkway and I roll something away on the moving walkway. And the walkway moves and the thing moves. And that's how it can get even farther away. So the universe doesn't really care about what's on your moving walkway. The universe cares about how fast is space itself expanding and what's all this stuff in the universe. And that's what determines how fast it expands. We want to know what the future holds, right? Or apparently we want to know what could the future hold. So what happens when we look back? That actually is where we find the answer. You don't think about this in like the Dr. Philway of the oh that was predictor of future behavior of this past behavior. But instead I, that was terrible. But the way you look at this is if you look back at the universe if you look at what it was doing in the past you can figure out how fast is it expanding now. How fast was it expanding then and what are all the different things it was made of. So if we say oh like I can look at the galaxies that collided and I can look at the distant nebulae that formed stars and what happened out there in the past and I can look at the stars that lived and died and recycled their heavy elements into the universe that's all the past. But the farther back I look at these things the farther back I look at all the different ways I can measure what was the universe like in the past that helps tell me what it's like in the future. So imagine now we've gone all the way back to the Big Bang, right? So everything is hot, dense, and expanding super fast. What's going to happen? You're going to have two things fighting each other. It's like a race. On one hand you have this initial expansion pushing everything out, trying to drive space apart. That's the expanding universe. But on the other hand we know that the universe is full of stuff and it didn't just come out of nowhere that stuff's been around since the universe was born. So what happens? You have these two forces fighting each other. You have the initial expansion and you have gravity trying to pull everything back together. Who's going to win? That's what you would say. Oh, let's examine all the possibilities. That's how we're going to do it. That's how we know who's going to win. So maybe like Goldilocks, the porridge is too hot, right? Maybe the universe has too much mass in it. So what happens if gravity wins? You can imagine it, right? The space is expanding. It's getting farther and farther apart but gravity is like it's going to pull everything back together. It's going to try and drive everything in. So you're going to hit some maximum size and gravity is still going to be pulling and things are going to turn around and the universe is going to re-collapse and you had a big bang and before you know it after a certain amount of time you ended a big crunch. So that's one thing. The other is what if we're down here, right? What if it's the other way? What if the porridge is too cold? What if the expansion wins and there's not enough gravity? Well then you'll expand and gravity will slow you down but it won't slow you down enough and you'll just expand forever and ever and ever. And the last one is that other Goldilocks possibility. Maybe it's just right. Maybe the universe is going to expand and try and reach some maximum size and gravity is going to try and turn it around. It's going to be perfectly balanced where if you had one more proton you'd re-collapse but it doesn't. Instead the expansion rate just asymptotes to zero. Everyone knows what an asymptote is if you have student loans. Okay. So these are your three possibilities here. It depends on who wins the cosmic race. Does expansion win or does gravitation win? If expansion wins then you're this top line, right? You expand, expand, expand and gravity tries to slow you down but it fails and here you go you're just going to expand forever and ever and ever. Or if gravity wins you re-collapse and boom your universe comes to an end over here. Or you can be in the middle and just be like on that Goldilocks case forever and ever and ever. So that's what we thought for years and years and decades and decades the fate of the universe is going to be one of these three and the whole field of cosmology which is my field was the quest to measure what's it going to be. I said I'd just give you the answer. They're all wrong. Everything is not right here. None of these is the answer. So what is the answer? I want you to think about something. What is, right? I told you the expansion rate is determined by what's in your universe. So imagine your universe is filled with matter and it's expanding. Well matter is just stuff, right? And so as your universe expands you got the same amount of stuff but it's getting less and less dense, right? So the more your universe expands the volume goes up, the mass stays the same so the density goes down. And that's it. That's how your universe would work if all you had was matter in it. And so you can see the expansion rate drops over time. What about if you got radiation? Radiation's a little bit like matter because it's just stuff. It's just photons. It's just these particles except they also have wavelengths. The wavelength of radiation is what determines how energetic it is. So if I take this space and I have these tiny, tiny wavelengths because everything's close together and I stretch my space what happens? These wavelengths stretch too. When you make a wavelength longer it gets less energetic. So if I take a wavelength like this in a one that's ten times as long the one that's ten times as long has ten times less energy than the one that was shorter the universe has expanded by factors of trillions and trillions since the big bag. So it's lost a lot of energy and you can kind of see that in this line that doesn't show up that this falls off faster. But what if there was some extra type of energy? What if there was this type of energy that just was inherent to space itself? What if I just said what about the energy of space itself? It doesn't drop, right? Because if I have this universe and then I have this universe there's just more space now. So if there's any type of energy that's inherent to the fabric of space then as space grows this energy is just growing. In this case the expansion rate remains constant. It doesn't drop. So as your universe grows it's like you're just making more and more of this new type of energy if there's any non-zero energy to space itself. So this is what Sarah was telling you they discovered in 1998 looking at supernovae, right? That you look at these faint ones and then you look at these more distant ones and you said, oh yeah, right if the universe were like down here this would be the closed case that re-collapses the big crunch case. This middle line here would be the intermediate case where it's that Goldilocks parages just right, right? And this would be this third line up here that's the open case that's the case where the universe expands forever. But what we observe is none of those it's this top line it's this case where the universe appears to have this extra thing this extra energy inherent to space itself. So what does that mean if the universe has this extra energy it means instead of a universe that expands and re-collapses or that expands forever or that is on the border between expansion forever and re-collapse we have this other universe instead we have one that accelerates we have one that if we look at a distant galaxy that's a certain distance away we see that galaxy expand from us and the farther away the galaxy gets the faster it appears to expand from us the faster and faster it moves away that's the thing that's accelerating not the expansion rate I told you the expansion rate stays constant what happens instead what accelerates is the speed of the individual galaxy now this is messed up because what this means is that here's my galaxy now it's pretty close by and it's expanding away at a certain rate but at a later time that galaxy is going to be farther away from me and there's more space in between us that's expanding so the galaxy is going to move away faster and this one is going to move away even faster and the most distant one is going to move away fastest of all I'm going to step on you for a while so what this means is the more that we let time go on I know you've had a market of because they're leaving every galaxy that isn't already gravitationally bound to us which is only our local group it's us Andromeda and those loser galaxies that are super close by that's what we get everything else they might be bound in their own groups but they're gone unless we go and get them they're accelerating away and the faster the more time goes on the faster they're going to move away from us in fact we don't really talk about how bad this is very often because it's a little depressing but I love depressing so if you were to say I'm going to draw a circle around all the galaxies within those 46 billion light years that I could reach I went at the speed of light today you'd only be able to get to 3% of them 97% of all the galaxies in the universe that we can see are already unreachable even if we left today at the speed of light and every second that goes by another 20,000 stars we lose the ability to ever reach so start on that space travel program now so yeah that's it our little local group is like these few galaxies like right in here that's our little local group us and Andromeda, the Large Magellanic Cloud the Small Magellanic Cloud the Triangular Galaxy about 50 to 60 other dwarf galaxies everything else the big Virgo cluster that's a collection of over 1,000 Milky Way size galaxies they'll all stay bound together but we'll never fall in there the Virgo cluster is expanding away from us at over 1,000 kilometers a second already and as time goes on that speed is only going to get faster and faster thanks to dark energy our local group will at least stick around once you beat the expansion of the universe once you overcome dark energy once you gravitationally bow things are going to stick around so you're in luck dark energy isn't going to come for you and we'll get all the galaxies in us all the stars in Andromeda all these little satellite galaxies we're all going to merge together it's going to be awesome here's what's going to happen 4 to 7 billion years in the future 4 to 7 billion years in the future the Milky Way and Andromeda are going to merge together as they start to gravitationally interact you'll start to see big spiral arms stripped away you'll see stars get flung off into interlactic space probably not us you're going to get to see a huge burst of new star formation one of the places the missing barions are even if she hasn't found them yet is they are in the interstellar media they are in the form of gas and dust and plasma in the halo of our galaxy when galaxies collide these gases will form new generations of stars so we can expect a whole wild burst of new star formation when this happens but once that merger is complete we're going to become a giant elliptical galaxy that's a merger of the Milky Way and Andromeda and we have already named it it sounds like a terrible candy bar Milky Andromeda what about in our solar system what's our future well we'll stick around I'm going to bet that we don't get kicked out of the galaxy during the merger less than 1% of stars will so I bet on us unfortunately in about 1 to 2 billion years only 1 to 2 billion years the earth will look like this why? as stars like our sun go through their life they heat up our sun right now is about 20% hotter and more luminous than it was when it was born a little over 4 billion years ago in 1 to 2 billion years it will heat up by enough that it should boil our oceans it's a slow process you cannot blame global warming on this but if you come back 1 to 2 billion years from now and you see this you can totally blame global warming on this it's just a different type so that's the future of life on earth 1 to 2 billion years is still a pretty good amount of time so don't worry yet the sun has maybe another 5 to 7 billion years before it becomes a red giant blows off its outer layers into a planetary nebula and contracts down to a white dwarf ok good news for us mercury is going to get eaten by the sun when it becomes a red giant venus is going to get eaten by a sun when it becomes a red giant suckers we're going to be just fine the sun is going to undergo some mass ejection events and that's going to gently blow earth to a higher orbit we're not going to get engulfed so when the sun becomes when it's done charring the solar system and charring the earth we'll still be a rock going around the sun it's pretty good stuff our sun will contract down to a white dwarf which will continue to be visible if there were any people left on earth which will not look like this in the future the sun is going to stay as a luminous white dwarf for about a quadrillion years ten to the fifteen years before it goes dark that is about a hundred thousand times the current age of the universe there is not a single white dwarf star that has gone dark yet in the entire universe and won't be for trillions and trillions of years the galaxy is going to look awesome if you can watch it from the earth during that time which you can't because we're going to be destroyed by the sun so let's pretend that this is from Terraformed Mars alright so you're going to see this is Andromeda this is the Milky Way you're going to see this big burst of star formation that is fun by the way when you look up at the galaxy have you ever seen pictures of galaxies with like these little pink things tracing their spiral arms have you ever seen that pink thing next time you see a big famous astronomy picture look for those little pink lines around the spiral arms that pink is real when you form new stars it emits light of a very particular wavelength that is 656 nanometers which is red to our eyes you combine red and white light and that's the pink you see so people look out for that in the sky four billion years from now what about the stars I told you about when our star is going to go dark we can have these big massive sun like stars when they run out of fuel they turn into white dwarfs when white dwarfs run out of energy after they radiate it away for enough time they go dark what's the universe going to look like when our white dwarf goes dark well our night sky is mostly stars in our own galaxy and if we were to say hey I wonder what this is going to look like 10 to the 15 years from now most of the stars will have burned out all the ones that exist today will have burned out but you form new ones you just don't form as many in the future as you're forming now that's something that we need to appreciate is that when we look at the universe today most of the stars formed 10 billion years ago already as time goes on we're forming new ones but we're forming them at lower and lower and lower rates so by time we get to when our star has burned out the universe is going to kind of look like this it's going to be really dark and the only points of light that are left will be super red in color they will be low in energy, low in temperature hopefully we'll have better eyes by then and what about the future of black holes? you might say this does not look like a black hole and it doesn't because there's no black hole that's done that yet today either but in the far distant future when the last star has burned out when there's no more gas or fuel to form them we will still have black holes and they will still be black for a really long time if you were to take the sun and sun into a black hole it would stick around as a black hole for 10 to the 67 years so one with 67 zeros after it and then it would slowly start to lose its energy black holes evaporate due to a process known as Hawking Radiation and in the last few seconds of evaporation that's when a black hole would emit the most amount of energy much that it would be visible to human eyes as a giant flash of light the amount of energy that gets released in the last second of a black hole's evaporation is 500,000 times as powerful as the biggest atomic bomb we've ever detonated on earth in one second keep an eye out for that black hole the most massive black hole in the universe that we know of will evaporate in 10 to the 100 years and at that point there will be no stars all the other galaxies we see will have been pushed away due to dark energy and the last black hole will have evaporated too so all of this is contingent on the story I told you being correct all of this is contingent on the fact that we think dark energy really is energy inherent to space itself you have also maybe heard this as a cosmological constant you have also maybe heard this as vacuum energy it is as though we took that same problem we started with and said oh, here's what our universe is doing today, we looked back from now until the big bang and we can extrapolate into the future and say the universe is accelerating and will expand at this rate but that all assumes dark energy is that energy inherent to space itself there are a number of different things it could be though and that's one of the things we're trying to pin down better that's one of the goals of HEDDEX HEDDEX is going to do an okay job but if we really want to know pin it down below 10%, below 1%, below 0.1% accuracy we need bigger and better telescopes on the ground and in space to do these big surveys because it could be the case that this energy inherent to space itself gets stronger over time what would that look like if things didn't just accelerate the farther away they got but if that rate of acceleration went up and up and up what would happen? well it means that galaxies that are bound together wouldn't necessarily stay bound together forever as time went on and dark energy gets stronger and these galaxies that look like they were going to be bound together can suddenly be pushed back apart again individual spiral galaxies spinning around would see the outermost stars get flown off and then the inner ones get flown off too individual solar systems if dark energy got so strong we would see the Kuiper Belt disappear and then Neptune and Uranus and Saturn eventually down to Earth it itself would see its atoms get torn apart and in the very final moments everything, even the atoms that made you up even the nuclei that made you up would be ripped apart as well that fate is known as the big rip and it's possible I don't think it's right but you can't be sure unless you measure it and you find out no the universe is really doing that how do the opposite thing? it could get weaker or it could reverse in sign so instead of getting stronger and stronger and accelerating way faster and faster forever it could go the other direction it could say you know we are going to reach a maximum size after all and it is going to turn around and it is going to re-collapse and we are going to end in a big crunch and that's something we can also measure so these alternatives all the same graphics you start at the big bang the universe appears to be accelerated appears to be this Goldilocks case and then dark energy takes over with the matter density dilutes enough and you see things accelerate and expand faster and faster but we haven't constrained it well enough to know that it won't rip or that it won't turn around and crunch again the way we are going to find out is through bigger and better telescopes and observatories so how will we know well the ESA is going to send up a mission called Euclid and that is going to measure dark energy to better precision than anything we've done before after that NASA is going to send up the W1st mission which is going to do even better and around the same time as that the LSST the Large Synoptic Survey Telescope is going to come online so if you think that this stuff is fun I'm telling you it's going to get even better in the 2020s alright now I'm sure that there are no questions for me because I didn't have questions for you that's not true but with that said let's stop here and see what questions you have I'll answer the first one preemptively yes this is a plus we're going to do the same thing as last time I'm going to look at hands and I'm going to call on you and then we're going to repeat your question so you sir had a question ok so this is a question about the cosmic spider web so thank you for making me go all the way back to slide number 3 we're going to do it let's see how fast it is the question is I said the universe is like this cosmic spider web so what does that mean when we're talking about what's happening to galaxies in the future is that a good paraphrase ok so where we have this cosmic spider web this is something that's formed over time if I were to say what did the universe start off as right and I didn't worry about the expansion this would be an almost uniform and over time it would start to look like a sponge where it had some holes in it and it had some denser regions but it was still pretty uniform and as time goes on and on the web gets more pronounced you start to get matter really clustered together in these nexuses and you get galaxies dotting along these filaments and in the great regions in between you have nothing then after about 7 billion years or so dark energy turns on dark energy becomes important matter has diluted so much that this energy inherent to space itself is more important for expansion and at that point anything that hasn't already become gravitationally bound never will be so there's a limit to how big these clusters are already and we already hit that limit about 6 billion years ago so there are these gravitationally bound objects they are going to stick around but by and large they're not growing still they're not continuing to get larger and larger instead each individual bound group of things that formed is expanding away from one another other questions over here okay there's this question about accelerating and decelerating the question is if dark energy is so powerful and the initial expansion is so powerful and we're accelerating today why was the universe decelerating for so long and the answer is in this graph right here that I'm going to get to if I can find it this one okay imagine what happens early on over here right you have this tiny universe and it's full of all the stuff it's expanding fast it's full of radiation it's full of dark energy it's full of energy inherent to space itself at the earliest times who's most important now what it is today that we've got all these things in the universe and now run your universe backwards in the past the energy density here for dark energy it didn't go up when you went back into the past it stayed the same so the effect of dark energy today might make your universe expand at a certain rate and early times it made that universe expand at that same rate so it's not accelerating fast today it's just the universe is really big and there isn't a whole lot else going on the matter on the other hand was denser and denser and denser and denser when the universe was one tenth in size the matter density was a thousand times as important when the universe was one millionth in size the matter density was ten to the eighteen times as important so the expansion rate due to matter was way more important in the past which means as the universe expands it cools and the expansion rate slows down if matter was ever more important than dark energy and even earlier on radiation was even more important than matter that's for about the first nine thousand years of the universe or so radiation was the most important thing so the universe's expansion rate drops at a fast level due to radiation and then finally radiation is less important than matter and matter is like oh my god we don't have to expand so fast and the expansion rate goes down at a slower rate and then matter density drops finally below the dark energy density and dark energy says oh thank god now I don't have to go so now I don't have to decelerate anymore and now the expansion rate can accelerate so that's why the reason why the universe was decelerating in the past is because matter and radiation were more important than dark energy was early on alright what other questions do we have we have one right here in the front I'm going to ask you to repeat that okay when you talk about the first nine thousand years of the universe what does that mean in the context of relativity astronomers have a lot of different ways of measuring time I say the first nine thousand years of the universe I mean if I look back at the universe to the moment of the big bang when the universe is first full of matter and radiation and I understand it as it is today that is 13.8 billion years of the past and that's what I call time zero so I count forward from that time where I can first describe the universe from the big bang and I say well what are the things that happen right it's full of matter full of radiation full of everything super energetic I am doing all sorts of crazy stuff things are flying around super energetic smacking into one another I'm making matter anti matter pairs out of pure energy and they're annihilating away into pure energy and all of this is going on and as I step forward in time and the universe expands the radiation density drops and the universe cools so after about one second I'm making matter and anti matter anymore and after about three minutes it's cool that I can make a atomic nuclei instead of just having protons and neutrons and after 380,000 years I can form neutral atoms for the first time and I don't have to smash it apart immediately anytime I put a proton and an electron together 9,000 years is counting forward from that it's that's the moment where radiation is finally diluted enough that it's wavelength has stretched so much that in terms of what makes a bigger contribution to the total amount of energy in the universe matter for the first time has passed radiation let's see if there are others and if you can, if there aren't then we can come back yeah you have a question what are your thoughts on multiverse okay this is an open-ended question what are my thoughts on multiverse do I have an opinion on that I do have an opinion on that that's the easy question what is my opinion on the multiverse so the Big Bang I've talked about that as being the moment we can first describe the universe as being expanding and full of matter and radiation there is a theory that is generally accepted known as cosmic inflation that came before the hot Big Bang and set it up at some very very high energy not like the tiny bit of energy inherent to space today but at some early times there is some huge amount of energy inherent to space itself and that space expanded at this hugely accelerating rate and in some pockets of that universe due to quantum fluctuations due to quantum fluctuations inflation ended that energy from space itself got converted into matter and radiation in some place including here the multiverse is a prediction you get out of inflation that says look in lots of places you don't have the right quantum fluctuation and inflation continues and you keep making more and more space but the more space you make the more chances you have for the right quantum fluctuation to occur for inflation to end and for a Big Bang to start and what cosmic inflation tells you is that we expect there to be other regions of space that are not connected to what we call the universe that are separated by these regions of inflating space where these regions have their own Big Bang they have their own place where inflation ended where the universe began with matter and radiation and we are not connected to them now I do not know if anyone professes to know how many of these other universes there are are there an infinite number only if inflation has been going on for an infinite amount of time has inflation been going on for an infinite number of time we believe our universe has information about the final 10 to the minus 33 seconds of inflation in it that is not a big number it is not possible that there are an infinite number of universes like this but if these theories that we have that appear to describe our universe are valid then there should be other regions that aren't contained in our own that have Big Bangs that have the expanding universe that maybe have different laws of physics from what we have you don't know shameless plug where we talk about this we have time for one more question and we are going to go with the lady in the front row the question is how do I feel about Fermi's paradox given that I invoked life and brought this question on myself Fermi's paradox for those of you who don't know say if the conditions for life are everywhere and we have all these different chances all these stars all these galaxies all these planets all these ingredients then where is everybody where are all the aliens and why haven't we heard from them yet that is Fermi's paradox and the the simple non-committal answer is because somewhere there is a hard step it's not easy to go from we were just matter in radiation to we are intelligent space-faring human beings we're not even really space-faring yet we're struggling at this but there is some step that's hard there we know some of the steps that aren't hard we know it's not hard to make atoms it's not hard to make stars it's not hard to make galaxies it's not hard to make heavy elements it's not hard to make planets it's not hard to make rocky planets at the right distance from their star for liquid water to be on them with the right ingredients for life on them with organic materials from interstellar space populating them that part is not hard but is it hard to take that step to go from organic materials to life is it hard to take that step that goes from life to complex multicellular information containing life is it hard to take that step from say the Cambrian explosion to intelligent using space-faring radio using human being type people my guess is one or more of those three steps is a lot harder than some Shmo in the 1940s saying boy I wasn't with everybody's audience I have been told that this talk is over so if you didn't have your burning question answered Ethan's book is for sale and like the answers are in that book so you can come see him afterwards so I just want to say thanks again to both of our speakers thanks to Peddler again for hosting us don't forget to take your lovely bartenders we're serving you all like as usual I'll be back again next month on June 28 so we hope to see you all again for warm weather