 All right. So my name is Charlie Lineweaver and I was asked to tell a few things about myself before we started talking and I was born in the U.S. as you might be able to tell from my accent and let's see these are three pictures of me one left when I was in eighth grade and then here I am in the middle as a soccer player and on the top on the right is me today. So who am I? Well I studied a bunch of things in university. I first studied history and I played soccer and I studied English, French, physics, German, Japanese. Essentially I've been in a university for my entire life studying things and German, Japanese, astrophysics, cosmology, exoplanets and most recently astrobiology. Also when I was in high school and college I didn't know what I wanted to do but I knew I wanted to be a man of the world and figure out what the world was about so I traveled to a lot of countries and I started making a list of the countries I've been to and then I made some more and there they are anyway I've been to about 60 or 70 countries and so that's right. So let's talk about are we alone in the universe and here's my name Charlie Lineweaver I'm at the Planetary Science Institute at the Research School of Astronomy and Astrophysics. All right and so are we alone? Well about four and a half billion years ago this is what the sun looked like it was an over-density in a molecular cloud and then four and a half billion years later we have this. So we have a transition from a cold odorless gas to a kangaroo or a life form made out of HNO CNPS that's hydrogen oxygen carbon nitrogen phosphorus and sulfur and that's life forms of all kinds are at the 98% level made out of those six elements and the question we're trying to figure out is how often does that turn into that in the universe? We know it happened on our planet but the question is has it happened elsewhere? All right now I used to teach a course called are we alone at the University of New South Wales and before the course I would do a survey and I asked the students are we alone and here is the distribution of answers before the course and that was 10% said yes we are alone 80% said no we're not alone and 10% said huh what does the question mean? Well after the course I took another survey and here are those results and the answer and you see how yes increased yes we are alone increased doubled to 20% no decreased and I'm most proud of the fact that 10% more of the students didn't understand the question and I guess part of the theme of tonight's talk will be that we have to understand what this question means if we want to try to answer it and it's not obvious it seems obvious but it's not. So for example why do people think that we're not alone? Well part of that reason might be because so many people have seen Hollywood movies with aliens like this nine-foot blue I guess this is Naititi from the Omatekaya tribe of the Navi people who live on Pandora and it's a planet a moon around a planet that goes around the star Alpha Centauri which is the closest star to the Sun well actually it's Proxima. Anyway if you watch enough of these movies in Hollywood you think no we are not alone but that but science is not a democracy you this is not how you do science by asking people what they think that's how you figure out what our prejudices are but not what the answer to the question is. So I should also point out that I've done this survey around the world and the places I've done it India has the highest percentage of no we are not alone as a matter of fact 85 to 95 percent of students in India think that no we are not alone maybe that's because they enjoy the alien movies more than other people I'm not sure. So in the question are we alone what does we mean and many people about half the people I've asked think we means we humans. So here's a human being this happens to be Charles Darwin. Now if you think it's we humans well then we know the answer are we humans alone in the universe well no we're not because we humans are not even alone on earth so we know the answer to the question here are all the other life forms on earth this is a phylogenetic tree and you can see that the human is not alone. So that takes care of the people who think that are we humans alone in the universe our closest relatives in the universe are on earth and here are some of them however if you then say wait a minute okay I don't like that I'll say how about we not we humans but we the life on earth and when that's the question it becomes more difficult now I should say that if you have any questions at any part of this talk just type in the question and they will be relayed to me through a chat window which is open on my computer now and so anyway just type in those questions if you have any so if we if the if are we alone if the we in that question is we the life forms on earth then what is the answer well it's it's an interesting thing about how changing the identity of the we so here's a picture from Scientific American and there are various tribes here you can see my art here's one group of hominids and here's another group here another group here and another group over here walking away there they are so homo sapiens are the only extant hominid on earth and therefore we are alone on the other hand homo sapiens are not the only ape so are we apes alone no we're not we as apes no we are not alone homo sapiens are not the only primate or the only mammal or the only vertebrate on earth and that in that sense we are not alone so the answer to the question really does depend strongly on on what we mean by we so what about alone what does alone mean and i was surprised to find out by asking people that people interpreted this word differently so for example if we found microbes on mars will we still be alone most of the microbiologists and biologists and physicists said oh yes so we they would say no we would found life elsewhere therefore we're not alone but a lot of people would say well wait a minute i'm not interested in microbes i can't talk to them i can't be friends with them so yes we would still be alone even if we find microbes on mars or for that matter if we find microbial life anywhere in the solar system or anywhere in the universe so the the meaning of the word alone is an important part of this question now are we alone in the universe that's the question we're trying to answer and we can also ask which universe are we talking about are we talking about the entire universe which it looks like from the latest evidence it might be spatially infinite or are we only talking about the observable universe the finite sphere of the universe around us that we can see and and make contact with we cannot contact the entire universe but eventually we may be able to contact the entire observable universe a lot of people think wait a minute that's way too big i want to only talk about life in the milky way galaxy for example the the drake equation talks about how many communicable civilizations are in the galaxy they're not referring to the observable universe or the entire universe now i'd like to know if that concepts are clear and if you have a question about that just ask now so the the majority of people in the universe majority of people on planet earth say no we are not alone and when people say that i say why what are your reasons what what evidence do we have suggesting that we are not alone and uh well some evidence is the following there are there seem to be a lot of earth like planets as a matter of fact there probably 10 to the 22 in the observable universe and the universe looks like it's spatially infinite so that's a lot maybe and that might mean that there are an infinite number of earth like planets in the universe and therefore there may be an infinite number of places with watery planets on which life could get started now i wanted to show you a little bit about some of the progress we've been making in finding exoplanets just as a historical perspective if we ask this question about 50 years ago scientists real scientists true scientists hardcore scientists they would say no this is not a scientific question why because we have no data we don't have any extraterrestrials in our laboratory that we can talk to or communicate with and we don't know any other planets well now that has changed in 1995 the first extra solar planet was detected and here is a plot we made in 2012 of all the planets exoplanets these are planets orbiting other stars that had been detected and just to show and here you can see the earth is right here and there's venus and there's mercury mars jupiter saturn urnus ineptum that's where our solar system is here is where we've detected a lot of planets and but that those are the easiest ones to detect with the highest masses and the shortest periods here's 365 days for example and use 88 days and most of them are very short periods and they're very massive now have a look at this next slide and it will show you how much progress has been made in the in well from 2012 to 2016 in four years and it got it has gone from this to this and so a lot more planets now here we are in 2020 so probably on the order of about 4 000 planets have been detected notice however that the the selection effects the bias of the observations is still towards the upper left of this diagram that doesn't mean that there aren't a lot of planets around the planets in our solar system it's just that the type of planets we live in the type of planets in our solar system are harder to detect than the ones we've been able to detect so far okay so based on the statistics and our knowledge of how what type of planetary systems we have been looking at we can estimate that every star probably has some type of planetary system and that's what this diagram represents planets around every star so if you go out tonight and look out at a star that star probably has some type of planetary system around it but we probably haven't detected any yet just because our observations are not good enough not comprehensive enough and uh we're unable to look at planets that are very small like the earth for example another reason why you might say no we're not alone is that in the past few decades not only have we found lots and lots of exoplanets that's the yellow dot here on the left extra extraterrestrial environments known to exist well we found lots and lots of them so this yellow oval has gotten very big but also here on earth we have studied more and more about the life on earth and we found that wow life exists in a much larger range of environments than we had known before and so the hope is if this blue circle is getting bigger and the yellow circle is getting bigger then there should be an overlap between these extraterrestrial environments and yellow and the types of conditions that we know at least on earth life has been able to adapt to okay so that's our hope but notice we have not found any life elsewhere yet and that's what we're looking for and I suspect though that we will find life or we will find something on these other planets because in the next five to ten years a lot of new instruments will be focused and targeting the nearest earth like planets so one other thing we should that goes into this thinking about are we alone is that in 1953 there was an experiment called the urie miller experiment and what he was able to do in this simple water vapor heated up have electrodes into an environment into an atmosphere with methane and ammonia and hydrogen they were able to pull out here amino acids and these are the building blocks of life and they can easily be made in the laboratory and not only that but the building blocks of life fall from the sky this is a piece of the mercheson meteorite and uh what that tells us is that the chemicals that we're made of the things that my head is made of the skin for example this finger these are made out of proteins proteins are made out of amino acids and amino acids fall from the sky and can be easily made in a reducing atmosphere so that the the ingredients for life are everywhere on earth and particularly in the early earth when there was a heavy bombardment and lots more things were falling from the sky because the inner part of the solar system had not been emptied out by the gravitational attraction of planets for all the dust and debris and gases that are in the accretion disk of young stars when they're forming so the bottom line here is ingredients are everywhere but what about the recipe how about the recipe how specific is the recipe do you just take all these ingredients push them together and then you get life uh that doesn't seem to be the case so we but we don't know much about the recipe needed we can't make life in the laboratory yet i'm not sure we'll ever be able to do that and until we do it'll be very hard to figure out the probability of life even if we have even if the ingredients are abundant and we're very sure that they are abundant because the elements that are the most abundant on earth are the same that are the most abundant in our sun and by looking at the specter of other stars we can verify that those are the same elements that are abundant elsewhere in the universe everywhere in the universe not just in our solar system not just in our galaxy but in all the galaxies we see so the the statement ingredients are everywhere applies to the entire universe and i'm pretty confident to the entire the entire universe not just the entire observable universe as for the recipe we're not quite sure okay and here's the the universe it's very big and i wanted to talk to you about one other piece of evidence that's relevant to trying to answer the question are we alone and that is this here's our galaxy here and our galaxy is a hundred thousand light years from here to here across now if if if us or another civilization make a rocket ship that could travel at about 10 the speed of light well then you can do the calculation and that figures out that how long will it take you to go from one end to the other of a galaxy at 10 the speed of light and the answer is here a million years it takes a million years to go from here to here if this were our galaxy now that's interesting because how old is this galaxy well the galaxy is 10 billion years old so that we can ask the question in the 10 billion year history of our galaxy how many times could a rocket ship go back and forth and back and forth and so the math is kind of simply you divide 10 to the 10 by 10 to the 6 which is a million years and then you get 10 to the 4 so what that 10 to the 4 means is that if there was a civilization that learned how to make a rocket ship that could go 10 percent the speed of light and they had evolved very early in the history of our galaxy then they could have gone back and forth and back and forth and back and forth and back and forth and back forth 10 000 times in the history of our galaxy and so that begs the question well when we look around on earth we see skulls like this we don't see any aliens we don't see any sign that the aliens have colonized our earth before we came when we lose our best radios to listen for extraterrestrial intelligence we don't hear anything we just have silence and so where is everybody and this is known as the Fermi paradox if you assume that life starts on some of these planets and that life eventually leads to technological life what you would call a civilization then there's no reason why they couldn't colonize the galaxy and yet we don't see them and that is the Fermi paradox where is everybody now you might want to interpret that saying well there's there is not anybody nobody's out there we are the only technological civilization in the universe maybe and maybe that's true we do not know now so here are all the stars and some of the stars in our galaxy and the question is hello is anybody out there now here's a cartoon that kind of just it's a message that demonstrates all what kind of makes fun at our search for life elsewhere here are two ants and no ants they they smell things we've searched dozens of these floor tiles for several common types of pheromone trails if there were intelligent life up there we would have seen its messages by now and so these are the conversation as the world's first ant colony to achieve sentience calls off the search for us so if we do find aliens will they eat us or will they help us join the federation of galactic civilization or will we kill ourselves before then we don't know so i'd like to summarize this talk is in the question are we alone it's important to know what do we mean by we if we mean we humans then the answer is simple we are not alone we humans are not alone on earth therefore we are not alone in the universe if the question becomes are we the life on earth alone in the universe well then it becomes a more difficult question but i should point out that the word life we don't have a good definition of that we're not sure what life is for example our virus is alive i've gone around the world and and talked to biologists and i whenever i hear see a biologist i say our viruses are alive our viruses alive and the uh the responses are the the first time i just tried to categorize the responses it was essentially half of them said yes and half of them said no but as i asked more and more i got dozens and dozens and dozens of biologists asked to answer the question are viruses alive they're about a quarter of them would say yes and a quarter of them would say no a quarter would say that's not a well-defined question and the quarter would say that doesn't matter it's not an important question and so that tells you the the status of what we know about viruses and what we know about the definition of life if biologists cannot agree on what life is one question you might ask is do we need to know what life is to answer the question are we alone and i'm not quite sure that's the case it seems that we do not know what life is and that would make the just as we don't know what who we is we if we don't know what life is maybe we've already detected life for example some physicists think that the oh life could be a hurricane or a convection cell or a fire and if that's your definition of life then we've found those things on other planets then there is the more subjective what does alone mean and uh well uh i don't know what alone means it means different things to different people uh if we find i think if we find life on mars even microbial life i think that that will mean that we are not alone uh but that's my personal opinion and i'll stick with now that's the end of the talk and if you have any questions please chat type them in now and i can wait and i will wait for a little while but while i'm waiting i thought i'd talk about i thought i'd ask my own questions for example is the question are we alone an important question and i think it is and uh but you might ask well is it or not when when i think the the movie what was the movie contact with people we've we found ex intelligent extraterrestrials and then the whole world changed it for some people and others they just uh they just said wow and then went on with their business i just wanted to tell you a story what i was interviewing people about uh you know i said if i gave you a hundred billion dollars with the caveat that you had to answer the question are we alone how would you spend it and a lot of astronomers would say i would spend it on really fancy new telescopes a lot of planetary scientists said oh i would spend it on sending missions to mars a lot of steady people this is the search for extraterrestrial intelligence would say i would send i would i would buy more radio telescopes and and look listen more carefully to the whole universe but one student in india he said i would spend a hundred billion dollars on poverty reduction programs and i said what why would you do that and he pointed out something very fundamental and that is if you want to answer the question are you are we alone you have to stay alive and it's not obvious to me that humans will stay alive we might kill ourselves we are the first generation in the last hundred years humans have learned how to how to kill ourselves and we maybe may do that and that would be too bad because that would prevent us from answering this question so that's why investing a hundred billion dollars in poverty programs is not silly okay we have a question here it says do you think it's likely that another civilization would share our interests in exploration or that we would recognize their signals for what they are could we just be missing it well first of all do you think it's likely that another civilization would share our interests in exploration well in Darwinism it seems to be a truism that if you want to go extinct you should stay on one small island do not spread out and so if you want to guarantee the survival of any particular species or life form you should have them spread out to different islands or different continents and this is something that Elon Musk thinks is appropriate for us because he thinks we should become a multi-planet species specifically so we can avoid extinction for example if there's world war three or world war four world war five it's possible that we could kill ourselves but if we have in the meantime established colonies on the moon or on mars something that we hope to do in the next five ten twenty years there's this window of opportunity now where we can do that and if we do that the people who will be the colonists on the moon and the mars will be immune to that type of extinction from world war one on the earth unless of course the war spreads to the moon so um let's see do you think it's likely that another civilization would share our interests in exploration the reason I mentioned this is because if there is a if Darwinian evolution selects for proliferation and exploration not only for conscious creatures but for other things I mean when you have a plant and it makes its seed pod it makes its seeds pod specifically so that they spread all over the place as a matter of fact that's what fruit is for fruit was constructed by plants so animals would come eat it and then defecate and carry the seeds further away and then defecate and so that was the method to spread in some sense that's the type of exploration you're spreading your species out as to whether we would recognize the signals for what they are I don't know I don't know it's what you're what you're asking about is what is a signal and what is noise and that is something that's surprisingly difficult to answer for example there the first jocelyn bell found the first pulsars and she and she labeled them little green men and the idea was wow these are pulses nature doesn't create pulses but human artificial intelligence does but then we figured out wait mate nature does this now the problem with the dichotomy that I just made between artificial and natural is something that I don't really subscribe to in other words how do you identify artificial signals everything humans do you could say is artificial but I would say it's also natural now so could we just be missing the signals yes of course but I would also say that maybe we don't know what life is and maybe we don't know the difference between natural and artificial and therefore it we're bound to miss the signals because maybe we're making a false dichotomy between artificial intelligence and natural intelligence and there is none to be made okay somebody comments alone might include interaction not just existence yes they said two people may live in the same space but they meet they may be alone if there is no interaction that's right and that's why most people on I would say maybe even most people on earth believe that if we discover microbes on earth I'm sorry if we discover microbes on Mars that have an independent evolution from our life then we would still be alone because what kind of interaction can there be well I'm not I don't subscribe to that because there could be all kinds of interaction between us and microbes matter of fact that's what the COVID-19 pandemic is an interaction between viruses and human beings you I have a dog and there's an interaction between the dog some people are satisfied with that interaction and they feel not alone when the dog is there other people would say no I need a human being not only do I need a human being I need a new human being who can speak the same language and who shares the same interest and maybe the same religion you can get arbitrarily specific about your requirements for feeling not alone that's why it's arbitrarily subjective and hard to make an answer to so those are the questions and there are there seem to be no other questions so I will sign out wishing you to stay alive because that's the only way we're going to be able to answer the question are we alone we need to stay alive so thank you for listening