Estimating the Chances of Life Out There

good evening everyone my name is Andrew frack boy I'm the Astronomy instructor here at Foothill College and it's a great pleasure for me to introduce this evenings Silicon Valley astronomy lectures co-sponsored by the NASA Ames Research Center Foothill College the Astronomical Society of the Pacific and the SETI Institute our speaker tonight is dr. Frank Drake one of the most distinguished astronomers in the United States who is popularly known as the father of SETI the search for extraterrestrial intelligence in 1960 dr. Drake performed the first experimental search for radio signals from possible civilizations around other stars thereby essentially founding the experimental science of SETI and he's continued to search for such signals using both radio telescopes and visible light telescopes with Carl Sagan and others dr. Drake composed several of the messages that humanity has sent out to the stars including the Pioneer plaque the voyager audio-video record and the radio message sent from the arecibo observatory the largest radio dish in the world dr. Drake helped found the SETI Institute the main organization involved in the search for life elsewhere and has served as the Institute's president for many years now president emeritus he still serves as the director of the Institute's Center for the study of life in the universe he is also the former president of the Astronomical Society of the Pacific educated at Cornell and Harvard dr. Drake has been a professor of astronomy at Cornell a professor of astronomy and Dean of Natural Sciences at the University of California Santa Cruz and a director of the Arecibo Observatory in 1961 dr. Drake proposed an intriguing method of estimating how many intelligent civilizations might be out there for us to talk to a method that has since become known as the Drake Equation tonight we asked him to up his thoughts about the Drake equations in light of recent developments ladies and gentlemen it is both a personal pleasure and a professional privilege to introduce to you a visionary scientist and a great popularizer of science dr. Frank Drake thank you very much for that very kind introduction Andy Andy and I have been partners for gosh I don't know how long 25 years at least and it's been a very great pleasure to work all these years with Andy you're very fortunate to have him here at football Foothill College I guess they don't play Matt doesn't play football here they do have a football team and undoubtedly you have heard him on kgo and many other radio interview shows where he always plays a marvelous role as a representative of the astronomical world in the world of Education now I'm here to talk to you about estimating the chances of life out there and zani just mentioned back in 1960 our civilization came to a threshold a very important threshold where our technology had advanced to a level where for the first time we could detect manifestations of intelligent life across the great distances which separate the stars at that time those manifestations were our radio and television signals our radar signals the signals we were then radiating could be detected by the radio telescopes then primitive compared to those of today from the nearest stars out to distances of about 10 light years that led to the first search which Andy just mentioned and a year after that search it led to the first organized attempts to give a scientific grounding to this whole subject to give guidance as to what makes a sensible search what the challenges were what we would have to do if we were really to have a chance of finding extraterrestrial intelligent life and as Andy mentioned that actually led to a meeting at which a formula appeared actually in a very simple way it appeared as the agenda of the meeting with the know feeling that this was only great importance other as an agenda but it has become in fact an equation which gives us both insight as to what we need to know to understand the challenges of our search and what we need to know to design the equipment we do use to search for signs of extraterrestrial intelligent life this equation is shown here in a pictorial form shown in your mathematical form in a second doesn't the the goal of the equation is to give you a number which will appear as n which is the number of an intelligent civilizations in the galaxy that is derived from an understanding of the history of the evolution of our galaxy of the life of Earth and our technology and the recognition that this can be quantified into a very simple equation which is simply the product of seven factors it is based on the fact that our galaxy has existed for about 13.7 billion years stars have been created at an almost constant rate through the life of the galaxy and this implies that stars planets life intelligence civilizations technology has also been produced at almost a constant rate with that picture one gets the simple equation the first factor is the rate of star formation the more stars you make each year the more civilizations eventually you will have you multiply that by the second factor which is the fraction of those stars which has planetary systems you then have the rate of production of planetary systems in our galaxy multiply that by the third factor the number of planets suitable for life in each system and you get the rate of production of potentially habitable planets in our galaxy you go to the next factor where you see the butterflies here and that is the actual fraction of such habitable planets which actually give rise to life multiply that by the fraction of those which eventually involve evolve in intelligent species you have the rate of production at this point of the number of new intelligent species per year in our galaxy you multiply that by the fraction of those which give rise to a detectable technology and you then have the rate of production of detectable civilizations how many are there well we consider that once made they become visible we may detect them but they may not last forever for one reason or other perhaps there will be a cosmic accident a great asteroid collision which terminates the life of the civilization perhaps the civilization will collapse under the weight of its own growing population and such and fail to manifest itself to space in a way we can detect most likely at least two optimists such as myself civilizations will come into view as ours is in view right now but not stay in view forever because of increasing technological prowess we have to detect things they waste signals sent into space power sent into space energy which is wasted and should they find ways to economize and to avoid that waste a civilization can be thriving and yet undetectable but this tells us that we must be careful about this and assume that a civilization once being detectable does not stay that way forever and so this gives rise to the last factor which has kind of a bad appearance here the lifetime of a civilization in a detectable State if we take the rate of production and multiply by that lifetime we get that actual number n we saw it in the first place well here's the equation in they're shown mathematically including all the factors I just told you the factor n or the result in on the left that which we are seeking and all those other factors ending with L the longevity of civilizations on the right and what you're looking at here is in fact a picture of a plaque at the place where this equation first appeared in a conference room at the National Radio Astronomy Observatory in Green Bank West Virginia where that first meeting in 1961 was held and this was the agenda for the meeting now in the 44 years since this came into being our understanding of these values and what controls them of these factors has changed greatly and that's what Andy wanted me to talk to you about tonight what did we think 44 years to do ago and what do we think today or know today instead of some cases where we knew nothing 44 years ago and so I'm going to run through this and tell you what discoveries have been made what clarifications have happened and as you'll see there have been some very important breakthroughs most of them in a positive sense that is increasing the possibility of there being intelligent life and certainly some very important discoveries bearing on the nature and existence of life of all kinds primordial and advanced and technological in the universe now as I said who the whole premise of all of this is that the galaxy has been producing new stars and planets for many many years our Sun is 4.5 billion years old so not the oldest not the youngest and by the way that's an important point everything about our system is usual nothing special that we have ever discovered about our system we are not a freak system we're at the Sun is an average star of average age we have average amounts of chemical elements nothing fess special nothing freaky seems to have been involved in our here we note another galaxy the materials of planets life as iron carbon nitrogen oxygen phosphorus are made in the hearts of the stars and released into space as old stars explode as you see here there they join the gas and dust clouds of the galaxy where the gas and dust clouds break off into little fragments as you can see here in this picture and some of them this is a picture from the Hubble telescope collapsed even farther and in time become new stars and back in 1961 we believed but did not know they became planetary systems we had a theory they shows the three steps in the theoretical understanding of how planetary systems come about you start with a great cloud of dust it collapses into a rather ragged disk as you see in step 2 here and in time becomes a flattened pancake we see that more closely here the star forms in the center one gets a huge cloud of debris which has become a pancake and the little bits of stuff in the cloud of debris as they orbit the central star coalesce joined together to form ever larger bodies which in turn collide with one another sometimes disrupting each other but in the long run slowly accumulating into a small number of large bodies protoplanets those objects which will become planets there's a stage shown here the T Tauri stage where as it's called by astronomers where this whole system ejects material at high speed out of the center and this has been the theory and in fact this is well supported by observations because we haven't seen now directly through photographs these discs of dust discs of accumulating material around almost all of the nearby stars where it's possible to see them still this was in 244 years ago a theory with no observational support probably the greatest in step ahead which occurred in those 44 years was the direct detection of other planetary systems clear evidence of the existence of planetary systems beyond our own and in fact planetary systems in large numbers and providing us with so much information that we learn not only of their existence but of the nature of planetary systems in general and as you'll see this has led to some really astonishing possibilities for life in the universe almost all of the discoveries so far have come by detecting very small changes in the position of spectral lines in the light that comes from the star which is the parent of a planetary system as the planet orbit as it planet orbits a star it's gravity pulls on the star and cause the star to do a little wobble in the sky as that star does the wobble it introduces this very small Doppler effect a very small shift in the position of the spectral lines this has been detected and from this one can deduce the presence of a planet what it's corporal period is what its mass is and in this way and it's very difficult evidence for the presence of at this point 152 an astonishing number of other planetary systems have been detected most of this was done very near here at the Lick Observatory this is it a nice winter scene using a rather small telescope but an extremely powerful and sensitive spectrograph which is really the heart of the of the discovery of these extrasolar planets the small shifts in the spectral line are very hard to detect it takes a very special spectrograph to detect them this is one of the telescope's it looks at with which is associated with the spectrograph it's a three metre telescope many of you have probably seen it as many years old and it's not one of the largest by far but until recently its spectrograph was the best in the world they're not is now a better one made by the same person who made the spectrometer at Lick and that one is at the monarch at the Keck Observatory on Mauna Kea now we do know that these little wobbles in the little wobbles in the spectrum are the result of star or planets orbiting stars and we know that because now in several cases we have found it we are with some of the systems that the equatorial plane of the orbiting planet is lined up sufficiently with the line-of-sight to earth that we actually see eclipses we see the planet move across in front of the star dimming some of the light in exactly the way one would expect if an object say the size of Jupiter passed in front of a star like our Sun this is proof positive that what we are seeing is truly a planets no doubt about it in fact very recently light from the planets themselves have been detected exactly as expected and so there's no doubt at all that these 152 systems are extrasolar planets that tells us that the fraction of stars which have planets at least deduced from these observations is at least 50% it is probably more the present detecting detection system this Doppler of deviation system can only detect very massive planets so in fact most all of the planets which have been found are very large planets like Jupiter 300 times the mass of the earth and recently down to Saturn and even to Uranus and Neptune masses but very massive planets and in most cases surprisingly close to their stars contrary to what we might have expected so what we have found so far is clearly the tip of the iceberg in that we are finding the massive planets the statistics show that there must be far more or less massive planets than the massive ones we are finding and those would be the terrestrial planets planets like the earth they're there to be found our sensitivity is not there yet so we look out and see objects such as this giant Jupiter's of some systems more than one some of them orbiting very close to the stars and the main point is that indeed there are solar planetary systems are not rare at all they are very ubiquitous they're present probably with at least half the stars maybe many more confirming those old theories of 44 years ago now this is sunrise on one of those planets I'm sure going to show you a lot of artwork today all of it by Lynette Cooke who is a space artist in San Francisco that cooperates with the SETI Institute and many other organizations undoubtedly you have seen her work in sky and telescope and astronomy and she's been very kind to give me a large set of very recent paintings she's done for a book which is just about to be published and I'll show you the cover page for that book at the end of the lecture but here's sunrise just to give us an idea of what these other worlds might be like you can see the star in the background very large because this is a picture this point would get with one of these Jupiter planets Jupiter sized planets orbiting very close to its star now so far the planets we have seen are not suitable for life because we know jupiter-like planets do not have solid surfaces they're very hot inside to constituents necessary for life are rare perhaps being destroyed all the time in the heat of these bodies but we know that with these must be many many small objects presently beyond our detection capability for instance these these planets may have satellite systems just as our Jupiter does and those satellites if large enough and we have one in our system which is large enough Titan will have enough mass to hold an atmosphere and although they may be satellites they will have all the necessary constituents for life what are those very simple water organic compounds carbon-based compounds and one of many sources of energy that are possible star light lightning heat from just the interior of the planet and so forth and so we're beginning to glimpse the fact that there may be a greater variety of potentially habitable planets than our old ideas which had it that only planets very much like the earth could be supporting life now 44 years ago we had a concept which was very widespread widely discussed and which was probably one of the most wrong concepts in the history of astronomy and this was the idea that for a star to have life like the life of Earth it had to be at just the right distance from its star just the right distance so there could be liquid water because we thought liquid water was necessary for life that meant it couldn't be too close to a star because it would be too hot the water would all be evaporated it couldn't be too far because then the water would be frozen and we couldn't have liquid water to act as solutions for chemical reactions and this led to the concept of what was called the continuously habitable zone and all the astrobiologists who are here remember well the lengthy papers and discussions of the continuously habitable zone and the calculations which showed it was in our system in fact very narrow that the earth just lucked out by being in it and there were controversy as to whether clouds would keep a planet more or colder and what changed the habitable zone and so forth well what we recognized finally and we it was staring in ourselves in the face all along was that there were phenomena which made that whole concept almost meaningless that there are ways for a planet in almost any distance from its star to be a habitable place one of the prime ways that this was flashed in our face splashed in our face was the planet Venus back again about 40 years ago radio telescope showed that the surface of Venus was at a very high temperature this was a very strange result because Venus is almost a twin to the earth in mass and Composition it's cloud covered at all time which means that much of the sunlight is reflected so the amount of sunlight it captures is almost the same as the earth and you would expect Venus to be at the same temperature as the earth and to be a planet suitable for life and yet the radio telescopes showed it wasn't at a temperature of say 70 Fahrenheit but surprisingly about 750 degrees Fahrenheit and it was in the early days at the National Radio Astronomy Observatory that I took this on as a project and was amazed to find that when I looked at the dark side of Venus it was just as warm as the hot side the night side and night on Venus lasts a 116 Earth days by the way the night side was the same temperature as the day side to within one or two degrees took 80 hours of observation to establish that by the way it was a very difficult measurement subsequently there were spacecraft landings which showed that the surface was truly 750 degrees that this wasn't some freakish radio emission that was confusing us and we quickly recognized actually Carl Sagan was pioneer in this that the reason this was caused by the greenhouse effect what we know so well today is the greenhouse effect that the atmosphere of Venus with almost a hundred atmospheres worth of carbon dioxide has such a powerful greenhouse effect that it keeps the temperature very very high and what this means is you could move Venus way out in the solar system and the temperatures would still be high you could put it way out and where it should be much too cold for life and it would be suitable for life and this toll is that a greenhouse effect can cause a planet to be a habitable planet over an enormous range of distances just an enormous range so an atmosphere can make a planet habitable and keep it habitable in a great variety of places in planetary systems and then we discovered something else the satellite Europa of Jupiter which has an equivalent insulator to keep its ocean if you will suitable for life in this case the insulator is a layer of ice about ten kilometers thick these two views of the same face of Arafah no craters because the surface is very young it's made of water ice ten kilometers thick underneath that ice there is an ocean of water the outer surface of this object is that about a hundred and seventy degrees below zero but that ten kilometers of ice creates an insulating layer so effective that water can be in liquid state a few degrees above freezing in the ocean of Europa which actually contains much more water than the ocean of Earth and this tells us then that here we could have life far out in a planetary system where the outer surface is extremely cold and yet in there inside this due to the insulating properties the conditions are suitable for life there's a third way this happens and that is just the surface of a planet itself acting as an insulator and the earth is an example of that deep in the earth that is depths of several kilometers there is a great deal of microbial life very ancient microbial life and if the Sun turned off that life would exist here on earth for billions of years just it kept alive by the heat flowing out from the interior of the earth so there's a third kind of insulators solid surface in addition to the liquid surface or the ice surface as in with Europa or a heavy atmosphere and that's telling us then that there are many ways by which planets can be kept habitable in places which forty years ago we thought were ridiculous this is a picture of the ice on Europa ice floes we're looking at area about 50 kilometers across and you see the ice floes which have broken off floated on whatever kind of slush or whatever is there sometime in the past it's now frozen but this is evidence that there are there is liquid water beneath the surface now what this says is that in planets like Uranus and Neptune there like that there can be places where temperatures are suitable for life the outer surface may be at a hundred and fifty two hundred degrees below zero Fahrenheit but as you go down in the atmosphere because of the great greenhouse effect of the atmosphere the temperatures go up and up and in fact we have observed directly with radio telescopes that there are layers in all of Jupiter Saturn Uranus and Neptune where the temperatures are as in this room and if the chemicals are right you could even have perhaps life there now that's a speculation there's no solid surface there is only gas but here's a concept of what are called floaters kind of cute for some reason they have turquoise spots on them that's the artists idea and the what you're looking at here is what could occur only not very far about ten ten to a hundred kilometers below the surface the cloud layer which covers all of these planets and by the way this idea is an old one it was first suggested by Ed saltpeter and Carl Sagan at Cornell in the first paper on extraterrestrial life which was ever accepted for publication in the Astrophysical Journal which was the real milestone because the editor at that time was a very conservative guy and thought talking about little green men and let alone floaters floating in the atmosphere of Jupiter was pretty far out and it was now stars like the Sun which again forty years ago we thought were the only place where you might find life the more massive stars burn up their resources they blink out too quickly to allow the evolution of any sophisticated life that was our belief we ruled out actually the great majority of stars the M stars the red dwarf stars M stars call that by the astronomers these are small stars with a mass about half that of the Sun but whose light is only a few percent that of the Sun and that meant that any planet of those stars would have to be cuddled in huddled and close to the star in order to be warm enough to support life I guess you can already guess what's coming a little greenhouse effect can take care of that and they can be far out from the star and be warm enough for life but there was another problem which people thought was lethal to the idea of life on these stars this is a conception of saturn-like planet orbiting a red dwarf star glowing sort of a reddish color because the stars are there was another problem and that is that if the planets were to puddle close enough to the star to be warm enough to have liquid water the tidal force of the star would be extremely strong and it would act on the star to cause the planet to keep one face to the star just as the tidal force of the earth keeps one face of the moon towards the earth and so it was felt that these would be very strange places with planets in synchronous rotation one face towards the star at all times and that meant one hemisphere of the star was in the dark never got sunlight and Starlight became very cold and would and this cold would freeze out the atmosphere and prevent them there from being an atmosphere and therefore preventing the origin of life now recently it has been recognized through calculations that this isn't so that the of course the star will heat the Sun word and hemisphere of the star and here's an artist's conception of it but this will cause an air circulation just as it does on the earth where hot air rises flows in this case towards the Terminator the boundary between light and dark towards the cold backside of the star and would warm the star and then there would be a reverse flow underneath the gases flowing from the hot side and the end result is it turns out from theory is that in fact the hot the cold side the dark side is kept warm enough that the atmosphere does not freeze out and so in fact these things could in fact be habitable very interesting places the star does keep one face to this this planet keeps one face to the star you may think there are two poles but there's a hot place in a cold place but these are not the poles of rotation those are at right angles to the hot in the cold place so it takes a little getting used to and what's wonderful about these when it comes to life is that you have a very hot region directly facing the star and as you go towards the Terminator the temperatures become less and less so there's a tremendous range of temperatures and this creates the opportunity for there to be somewhere a zone where the temperatures are suitable for life where there will be liquid water and life can evolve and the artist has shown this here in the form of lakes which are forming just the right place and you can see the clouds tracing the streaming gases from the hot point to the cold point you might call these stars Camelot the star the star if you're standing in any place on this star where the Sun where the star of the stars in the sky the star never moves star never sets it never Rises it's always in the same place there is no night so if you're a living thing there and you live in quite a different way as we live here if you move towards the hot substellar point you get warmer if you want cold you want to ski you go the other direction towards the Terminator and you can have anything you want and it's totally predictable now just to make this even more interesting something has been revealed in those last 40 years about our system which reveals to us at phenomenon which we had not guessed and was real real to us by the planet Mercury Mercury is close to our Sun and people thought it kept one face towards the Sun just as the moon does towards the earth but in fact radar observations made at Arecibo some years ago showed to our surprise that that is not the case and that as mercury swings by the Sun in a very elliptical orbit by the way each time as as closest to the Sun it presents an opposite hemisphere to the Sun this is called a resonance it comes about because of Kepler's third law for those of you who know that which says that in an elliptical orbit an object as it approaches the closest point to the star moves very rapidly now it not only moves very rapidly but what's important here is that as it gets close to the star tidal force has become very strong the tidal forces go as the cube of the distance of the star on the inverse cube and this means there's a tremendous tidal force on the star as it zooms by on the planet as it zooms by the star and what happens is that title force tends to make the star or the planet keep one face towards the star whenever it passes close to the star and to do that it must spin at such a rate that it's not in synchronous rotation and in fact in the case of mercury it turns out in the balance point where the torques due to tides are averaged out to zero in the course of an orbit occur when the object presents one alternate faces to the star in our case the Sun each time it passes closest to the star this could well happen to many perhaps all of the red dwarf planets in which case there is no cold side to them on each close passage they will present an opposite hemisphere to their star just as mercury does and this too will aid in evening the temperatures and making life possible now that's important because for every sun-like star there are almost eight red dwarf stars and so if now the red dwarf stars are perhaps more promising as abodes of life than the sun-like stars it means the number of potential habitable planets has grown enormous ly in the galaxy now this is a diagram that shows you how this work works in a way it shows you two of the newly discovered planetary systems superimposed on a diagram of our solar system on the left is the system of 47 Ursae Majoris which actually has three planets one of them is very close and hidden in the image of the star in the center here circle planets are nearly circular so this is very much like our system on the right is the system of sixteen Cygnus sixteen signe which has two planets one I'm wanting very close again and one of them far out as you see with a very elliptical orbit this is the type of orbit that would lead to that phenomenon I just described to you of the planets in the red dwarf stars presenting alternate faces to the stars they go by but there's another point in showing you this and that is that in the planets we have discovered the great majority have very elliptical orbits much more so than in our solar system now that ellipticity is required to create the mercury rotation phenomenon but quite separately it is evidence for phenomena happening in these systems which are very important how do you get elliptical orbits when you start out with a disk of dust as I showed you where everything is rotating in very circular orbits well what happens is objects collide with one another and they make planets and if you make enough planets they will be orbiting in orbits close enough to one another that their own mutual interactions will perturb the orbits alter them so the planets don't follow the same orbits all the time and one has shown with computers that given enough time this alteration of planetary orbits can result in one planet crashing into another or making a close passage to another and the end result is a destruction of a planet or and this is what's really surprising the ejection of a planet from a planetary system so what you see here is an artist's depiction of the sort of event which created our Moon a very large planetary size object crashed into the earth actually and ejected enough material that it became the moon and that's how our system came about but had that object narrowly missed the earth it could well have been accelerated by the gravity of the earth to such a speed that it would escape the solar system and in fact the computer modeling shows that this must happen very often in fact most of the systems we have found have as many planets as they can hold and what's left there are in elliptical orbits and this suggests that more planets than they could hold have been were created and some of the poor unsuccessful ones have been thrown out of the system to travel in the intergalactic space forever an amazing thing and in fact there should it be a probably about one of these so-called runaway or rogue planets ejected from every system and this can mean that there are as many lone planets nomads of space orphans of space traveling in our galaxy as there are stars and yet we have never seen one they have to be there we know they're there despite the fact that we have yet to see one now of course that's interesting you might ask why haven't we seen one it turns out it's very unlikely that one would have passed through the solar system during the history of mankind and therefore there it hasn't happened since we were here to observe it but you could ask the question could there be life on the rogue planets and there's many rogue planets as traditional planets like Earth and your first thought was of course not they're sitting in the darkness of space for billions of years how could there possibly be life there but in fact it could be here's a dumb artist's conception of a rogue planet run away planet far from a star still very young with lots of volcanic activity and here again our own system has revealed a phenomena which makes it so that rogue planets could support life now probably not intelligent life but primitive life how can that be well we look at our Jupiter and Saturn and we have discovered to our surprise that they release much more energy than they receive from the Sun in both cases well in case of Jupiter about twice as much energy as we would receive from the Sun a case with Saturday's much so the energy coming off from Saturn too is generated within Saturn actually from a sort of helium rain if you wondering how oh and only one third is created by his sunlight so if you took that planet made it a rogue planet threw it out of the solar system out into the interstellar space so it no Lori had sunlight it would cool down but it turns out not much about ten degrees and this is after four and a half billion years there has been that much energy available from the interior of Saturn or Jupiter to keep it nice and warm for long enough to evolve life so these objects the rogue planets and this is now shown very nicely have enough energy coming from their interiors to keep them warm warm enough for liquid water for literally billions of years and so even there there are possible abodes of life well I've spent a lot of time really on one factor here which is the number of planets in each system suitable for life and what we've learned in 44 years is that we didn't know nothing 44 years ago there are all these other possibilities and that the number of habitable planets is probably something like 10 times what we thought 44 years ago now that's fine but there's some other planets I'll just mention them for completeness actual planets of terrestrial mass which company pulsars neutron stars we don't think there's any life there but it's kind of nice to look at their pictures because they're kind of pretty mmm they're bombarded with x-ray and gamma radiation so they sort of glow in the dark not through their own heat but because of that radiation but what about the earth in its earlier days when it was very active with lightning greenhouse effect volcanic activity or Mars which in its early days had an ocean and looked something like what you see here and this brings us to the factor and in the equation and having to do with the origin of life what is the fraction of potential life bearing planets which will give rise to life well here we had good ideas even 44 years ago there had been experiments done in which we simulated conditions in samples of the primitive atmosphere of the earth as we believed it to be then and as well as atmospheres simulating the atmospheres of other planets such as Jupiter and Saturn you take a mix of chemicals carbon or methane carbon dioxide water co2 you put them in a flask introduce energy in this case an electrical spark see what happens and what happens is you create large organic molecules and in particular the basic building chemical building blocks of life now it doesn't take much to make life as we know it here on earth actually only 28 building job you just need twenty eight parts bins you need five hearings and pyrimidine x' 20 amino acids sugar deoxyribose phosphate in water and that's all it takes basically to make life of course not sophisticated life that invents other things that are make it much things much more useful but basically that's what you need and all that stuff is cooked up in these kind of experiments always and this has said that there are many many chemical pathways to life in a primitive atmosphere like the earth now the old idea was that he's got captured in the ocean and created a sort of primordial soup there was nothing living to eat it so it stayed sterile it didn't spoil it just got thicker and thicker and thicker and Darwin himself proposed that this would accumulate and what he called a warm little pond and the chemicals would react and out of it would come living things now just what happened has been probably explained a little in a way more closely to the truth by our DNA analyses of the history through time of the evolution of life on Earth this is the tree of life the famous Tree of Life which has three branches the bacteria the Archaea and the eukaryotes we are at the very top there on the left the animals the most sophisticated with the most complicated genomes as you go back down this tree you go back in time and when you get to the very bottom you see a word there thermophiles that means friends of heat and these objects they're very primitive micro and microbiology are things which like very high temperatures they live at temperatures of boiling water for example and this suggests then that the warm little pond wasn't just warm it was really hot and where do we find that on earth we find it at the black smokers the deep-sea hot deep-sea vents in the ocean and all of this supports in a funny way a smoking gun there it is and that life was born at the deep-sea vents that this is somewhat controversial there's some thought that it was born in colder water and migrated to the deep sea vents because they were so full of night nutrients and maybe that so but in any case this is good news because we're in any water covered planet we can expect deep-sea vents to people there and there for life to arise and what this has said is that the fraction of potential life bearing planets that give rise to life is probably 100 percent we're looking now or we'll look soon for life underneath the surface of Mars to see if that insulating surface has kept temperatures suitable to keep life alive at the necessary depth which isn't that far down 100 meters or so down where water would be liquid on Mars not far down for us on earth but very far down for any kind of spacecraft to dig and that's one of NASA's great challenges know what about F sub I evolution this is the most controversial still part of this whole subject there are paleontologists that look at the fossil record look at our earth today and make what I think is a dreadful mistake beef right up front with you about that they look at Earth and they say oh there have been literally hundreds of millions of species in the history of the earth and only one became intelligent doesn't that mean intelligence is rare well that has to be wrong and I can tell it to you in a way which I think you will accept life clearly it takes a good length of time to evolve an intelligent creature we're very sophisticated we need big brains we need very large biological physiological structures to handle it or to produce intelligence so it happens slowly in our case of on the earth it took four billion years for intelligence to arrive but there is no certainly not just one path that can lead to intelligence there may be many paths leading to intelligence and intelligent creature different species but they I won't all arrive there at the same time one of them will arrive first and so in every planet at some point there will be just one intelligent species that's the only way it can be and so when that intelligent species is smart enough to look and know something about intelligence it shouldn't be amazed that it's the only one it's the only possibility and any of you want to argue with me about that I would be glad to but I think that particular argument is pretty strong the fossil record supports this by the way it shows that there have been there's the one thing that is always increased in the fossil record is the size of the brain so being smart is good for you it tells us and here's an example of one creature that was on its way to being intelligent perhaps before we became intelligent it's a dinosaur it's name is tenon X or Z Nicholas hope you all got that that's going to be on the quiz in that astronomy course that Andy was talking about or it's a thousand dollar question on Jeopardy if you're ever on Jeopardy standing to Casares any galas it was about our size weight about a hundred pounds stood about five feet tall could grasp things with his forepaws it was bipedal it even had binocular vision which was very rare in dinosaurs but most interestingly its brain was much larger than was typical of hundred-pound dinosaurs hundred-pound dinosaurs actually had brains about the size of a pea they were really dumb folks but not this one this one had a brain whose brain mass was approaching that of a human infant and so it has been speculated it lived by the way 65 million years ago it has been speculated it had it blasted a few more million years it might have evolved into what you see in the foreground here the first intelligent creature on earth and this would have been your mother and her your father and your boyfriend or your girlfriend and you would have loved them just the same but that was not to happen because this is courtesy of professor Morrison who was sitting here in the front row he's the Godfather of doom on planet Earth well he has known as Doctor Doom at the NASA Ames Research Center he's the expert on asteroids that collide with the earth and 65 million years ago ten kilometer asteroid it'd collide with the earth created a tremendously devastating event spraying molten rock all over the earth set the earth on fire created a cloud of dust which last for months killed all the large artists disrupted the food chain so terribly that all the large creatures on earth perished and with that went those dinosaurs this is what a really mad dinosaur looks like here comes the fireball and what do we do about it when the great catastrophe was over the dust settled and finally the Sun came out again there were some creatures who had made it through the long night they came crawling out of holes in the ground out from under logs and they were our ancestors they were little shrew-like characters the mammals of that time the largest mammal you could be or any larger the dinosaurs ate you but now they weren't there anymore and so you could grow and become big big boys and girls and 65 million years later them is us folks well I think that story says that given enough time you will get an intelligent species but as I said this is still controversial still controversial no on earth as soon as you had an intelligent creature that could manipulate tools namely us technology appeared independently in at least five places and this tells you that intelligence quickly learns to a debt use its physiology to become a tool maker and it's only an instant in cosmic time from the simplest tools to motorcycles and videotape recorders automobiles jet planes and all the rest all of that has happened as you know and something like a thousand years out of the four billion year history of life on Earth so that tells us that the F sub C the fraction which developed technology is very large as long as they can manipulate tools which probably means they need to be land animals probably not intelligent creatures in the sea so we have things such as this the Arecibo radio telescope and other civilizations can have this too this by the way is the strongest sign of our existence on earth it has a 1 million watt transmitter and that large sort of hemispherical thing you see in that slide and then this one and that one megawatt 1 million watt transmitters power when concentrated into a narrow beam by the big dish creates a beam so powerful that it outshines our Sun by not a little bit but about a million times within the frequency band of the transmitter now that signal is detectable by another telescope like our own from a distance of the far side of the galaxy so from any civilization in our Milky Way which has a system like this pointed at us we can detect it this has just recently been upgraded for use it's in SETI there's now has 7 beams and is by far the world's most powerful instrument for searching for signals the only problem with it as a SETI detector is that it's used for other things and is only available to say in essence a few days a year although it is used regularly to capture the data that's used in SETI at home for those of you who use that system on your personal computers so we are an example of an intelligent civilization this is what the large bowl it and Arecibo it looks like and if we look at ourselves and use ourselves as a model which is all we can do we have been detectable for about 50 years and now I'm addressing that very last factor in the equation the L factor longevity we have been detected well for 50 years primarily through our television and radar transmissions how long will that continue we wish we knew because that is the key factor in we'll see in a minute in estimating the number of civilizations to be found in our galaxy this one is the big unknown and unfortunately we cannot know what it is till we found another civilization because we're we don't think we can use ourselves as a model we're too much in the beginner phase and in fact we already see signs in our civilization of our civilization heading towards becoming less visible or perhaps even invisible that our longevity as a detectable civilization may end much sooner than we expected for example this is really scary to people like me what is this you've all used that you just didn't know it this is a synchronous satellite which is used to transmit television programs to earth it's used for DirecTV Dish Network is used for the old large dishes it's actually used these days to transmit even cellphone messages to and from the earth and why is this bad news to people like me well are as I just mentioned Arecibo transmits a million watts a typical conventional television transmitter as you find on Sutro Tower in San Francisco transmits about 3 million watts in fact there's 30 million watts of power comes out of the Sutro Tower in the form of television programs that is the main sign of our existence but what comes out of one of these it's beamed carefully down on the earth here's the actual parameters and if you look about halfway down you'll see the kayuu band payload that's actually the channels that are providing the signal to the little dishes many of you have the 18 inch dishes and what's the power 75 watts and not much less than a million watts or 3 million watts you see some others or 20 watts and that's all it takes to send us a signal from 22,000 miles above the earth to a little 18-inch dish on your back porch or whatever and give you a very fine television picture it's one of the most amazing developments in the history of technology not only that this is the pattern of the radiation as it's directed on the Earth from the satellite you can see they actually are capable of tailoring it so it matches the contours of the places where the people are that received to pay the bill for the signal it matches the continental United States you see a little finger reaching out to Puerto Rico another one to Hawaii and this is brilliant engineering but for us very bad news because not only is it only 75 watts but almost all of that falls on the earth and is absorbed the actual power going out into space is probably not more than 10 watts and that's a lot less than a million if this becomes the way to to transmit television the earth will become much harder to find but we search on other things the cell phones affordable even by core people all over the world and they radiate a power of only a few watts and yet they work we don't need high power to make that work again a step higher our trick in our development of our civilization leading to less visibility so what this says is well we don't know what L is we could only guess we might guess there are other things which will keep L a large number for a long time but we don't know what those are I'll show you a couple examples and impossible examples in a minute but that allows us now to take a look finally at where we stand today this this is actually a page that I did not invent it's actually from the notes for a course at the Pennsylvania State University I just picked it because it's an unbiased estimate of all the factors in the equation you can see them here mean rate of stars one to ten a year fraction of stars point one to 0.5 I mentioned point five number of earth-like worlds one to three that's about what I said a fraction of those were life develops from point one to one I said it was about one intelligence somewhere between 1% and 1 so on the lifetime here estimated at much more than our experience ten thousand to a million well if you multiply these all together what do you get well I want to show you an abbreviated version of this if you take the most likely numbers for the first six factors they all multiply together very conveniently to a number close to one and this makes it easy to abbreviate this equation into something much easier to remember you can even put it on a california license plate if you want mystify all your neighbors what does that mean n equals L it's telling us that as best we can guess guess is the right word to use the number of detectable civilizations is equal to that longevity like the time on average they stay visible now you may wonder why this is written in such fancy letters and the scientists here know the answer to that it's then when you don't that when you don't really know something well in science it makes it more believable if it's written in fancy letters so N equals L well what is L we don't know and unfortunately people keep coming up to me and ask me when are you going to succeed when are you going to succeed and I used to say by the turn of the century but that was about ten years before the turn of the century and I found out that was embarrassing because pretty soon the turn of the century was there and we hadn't succeeded so and the right answer to this question is we in order to know how soon we will succeed we know that we need to know the value of hell but to know the value of L we have to have succeeded and if you say that real fast it sounds sensible but if that is not satisfactory to the questioner and they say wait a minute so okay what is L how're you gonna when are you going to succeed then the fallback answers the desperation answer is soon Tsun is not very well defined scientifically so you weasel out of it in that way don't ask me what soon is but soon as the answers to that question in case any of you are tempted to ask me that well what should we search for I've mentioned that we've been searching for radio waves we could search for the lights of cities at night this is a mosaic of photographs of the earth at night taken from satellites in space you can see the Northern Lights up there in the upper left hand side over on the far right the brightest country is Japan and if you've been there know that they love to put all kinds of bright lights on their buildings at night you see some strange things and lights in northern Siberia which are the hecka the waste gas from the oil fields being burnt at night same thing in Saudi Arabia here's the United States at night if you got good eyes maybe you can find your house I think you can probably find the Bay Area there and you can see in fact route 80 stretching from the Bay Area to Sacramento and you can see route 5 going all the way up to Portland and Seattle but little city's looking like beads on a string along the way well it turns out it would take it tell us optical telescope about five miles in diameter to see the lights of cities at night so we're not going to do that now but it's possible other civilizations do and they know all about us because they have been able to build such large telescopes in space undoubtedly or they have used their own star as a gravitational lens to make a giant telescope you can do that it makes a telescope with the lens of equivalent to the diameter of the star about a million miles so it's a very powerful instrument you can actually resolve cities on the planets of stars 100 or so light-years away and you might ask why aren't we doing that and the reason is the focus of the lens if it's a star like the Sun is about 500 astronomical units from the star which is about 10 times the distance to Pluto so it's not doable by us yet but it's in our future and it could well be that this is the standard way to detect and study civilizations you use the stars as gravitational lenses radio this is what we used in the first search in 1960 was an 85-foot telescope at Green Bank here's the equipment not a transistor or computer to be found it was 44 years ago but for those of you are old enough you will recognize over there on the right side a woollen sack tape recorder which we had attached to the equipment so that we could record the voices of the extraterrestrials when we captured them with our big radio telescope this modern one channel at a time it was used to search for signals for the two stars nearest to the Sun that are like the Sun toss SETI and epsilon aridity for two months no signals from those stars were her signals were heard but they were from us we've graduated through larger things such as the Arecibo telescope 1,000 feet in diameter with radio receivers which are far more sensitive than we had 44 years ago in fact this telescope can duplicate all of that first experiment all two months worth of the observations in about a tenth of a second that's all it takes so you wonder maybe why did we do that but you've got to start somewhere today we've graduated to the use of sophisticated computer electronics which allow us to observe not just one channel at a time as it was in 1960 but rather today we observe a hundred million channels at a time and at Harvard there is now a system which can observe about 250 million channels at a time and in our new system at SETI Institute we will be observing 120 million channels at a time this is a typical screen lots of noise each car is out of line here is one seconds where the data you see a slanty line that is the most distant intelligent signal ever captured it was captured from the Pioneer 10 spacecraft which is at the edge of our solar system radiating a power of about five watts about the same as a cellphone from a distance of we still observe it today this was earlier a couple of years ago we observe it today it about twice the distance to Pluto and still easily detect that signal it just shows the power of the radio telescope to detect very faint signals from very great distances what else might we be out there may be creating lawns greater longevity greater L values space colonies might it be that this is what we detect colonies in space radiating to their home planet to other space colonies it's things like this which we can only wonder about things which can exist and which could create or maintain the visibility of civilizations for much longer time than we might presently imagine it's even been hypothesized that there is a Galactic Internet of interconnected civilizations with their interconnected beams transmission beams shown here as a sort of a spiderweb of energy going across the galaxy so although we see our own planet perhaps becoming fainter perhaps there are other things which keep civilizations visible things like this perhaps solar power stations in space who knows we do need to do a great deal of searching particularly in the radio so far we have searched 150 light a fifth 150 light year radius from the Sun and this diagram gives you a slight feel for how little of the galaxy we have actually looked at we have looked at thousands of stars and yet it is just a drop in the bucket we have hardly touched the cosmic haystack we want to move on now to a thousand light-years from the Sun several thousand and to do that we at SETI Institute are constructing a radio telescope and just north of Mount lassen in Northern California it will use 350 small antennas using dishes as you see here they're each 20 feet in diameter here you see actually ten dishes nested together being carried from the manufacturing plant in Idaho Falls Idaho all the way to Northern California on his truck where there's this tilting bed because um when you go under it needs to be tilted like this to not be too wide for the highway but it's now too high to go under under passes and so it has to be tilted up whore's not only have to bring the police and close the road whenever you go under a low over crossing and here are two of the dishes already in place at Hat Creek in this project which is a joint project with the University between the University of California at Berkeley Radio Astronomy lab and SETI Institute and here's some really happy people recognizing hey the dishes actually move and focus radio waves the way they should and here's a picture with three dishes in place and this is presently we're in the process of making a thirty-two dish array but the eventual goal is three hundred and fifty antennas in this system which is called the Allen telescope array named for Paul Allen the one of the cofounders of Microsoft which is provided who has provided major funding to the project this is what it will look like if all goes well enough and the funds are raised we do not have all the funds in hand yet this is what it will look like in the year 2007 and what we will use to continue the search the search will go on at Arecibo our Siebel cannot look at the whole sky and in particular could not look at the center of the galaxy which is one of the more promising places the Allen telescope array can look at the center of the galaxy and examine much more of the galaxy than the Arecibo telescope nearest e of a telescope has more sensitivity but the Allen telescope array will be able to look at some of the prime places in space so where do we stand we've learned that there were some things we were badly wrong about 44 years ago we've learned a lot more about where planets can be habitable there are far more than we ever imagined and in all other respects our assumptions of our guesses 44 years ago have turned out to be roughly correct and in fact we can expect a very large number of detectable civilizations in space so we should continue if we do not search we lose an opportunity to enrich the world with a wealth of new information and we'll lose almost nothing in material value it doesn't really cost a lot to carry out these searches at least not on the grand scheme of things some people think it cost too much this is just to say that's not true the opportunities are too great the potential benefit far exceeds any reasonable cost which isn't in any cases miniscule if we do search we may enrich knowledge and philosophy without bounds it will cost us relatively nothing all of Seti in the whole world costs only a few million dollars a year very small compared to other major scientific projects and perhaps most importantly scientists like all people have their dreams we all need dreams of a better future of accomplishing good things of having a better life and we will keep alive our dreams of learning of other intelligent life in space

Channel: SVAstronomyLectures

Views: 26,853

Rating: 4.6172247 out of 5

Keywords: Drake, Equation, astronomy, ET, SETI, Drake Equation, Frank Drake, life beyond Earth, extraterrestrial life, planets, stars, exoplanets, science, space, Aliens, astrobiology, intelligent life, radio astronomy, astrophysics

Id: mucWk4zjSBU

Length: 74min 33sec (4473 seconds)

Published: Tue Feb 19 2013