Carl Sagan Christmas Lectures 6 - Planetary Systems Beyond Our Sun

[Music] [Applause] thank you this is the sixth and last of this season's Royal Institution Christmas lectures on planets and today our topic is planetary systems beyond the Sun beyond the one that we live in we have in previous lectures talked about most of the other planets in the solar system certainly from Mercury to Saturn we've said a little about Uranus almost nothing about Neptune and Pluto and we've touched on asteroids and comets now all of these objects except for the Comets are in a kind of flat plane which is also the plane that the Sun rotates in and that system is called the solar system and it's a lovely system of star in the middle and the planets strung out like beads on a string and we note that there are other smaller systems that look a little bit like that the moons of Jupiter for example are similarly strung out in the equatorial plane of Jupiter likewise the moons of Saturn likewise the moons of Uranus it looks a little bit as if whatever process it was that made the solar system made some miniature solar systems as well back four-and-a-half or five billion years ago when the solar system was formed and the general idea which is mostly accepted by astronomers on how planetary systems form is that there are great gas and dust clouds in interstellar space and that here and there there are condensations places where there are more matter more gravity material collapses while rotating and big lumps become so hot during this collapse that they have thermonuclear actions which convert hydrogen to helium release energy and that lump turns on and becomes a star smaller lumps form at the same time but not as massive don't have high enough temperatures for thermonuclear ignition do not shine by their own light our dark objects shining by reflected starlight and those are called planets now if that's what it's about there ought to be lots of planetary systems planetary systems would then clearly be connected with stars and so let's just spend a moment talking about the life cycle of stars stars are born they live they die and there are an awful lot of them as this picture reminds us here is a photograph of a naked-eye object the Orion Nebula it is the middle star in the sword that's hanging from the belt of Orion who's a hunter and in that psychological protective test but this is the Orion Nebula which is a kind of stellar nursery a place where stars are forming recently in the last millions and for tens of millions of years and for all we know planets are forming rapidly here as well stars live for a sizable period of time our Sun has a lifetime in its present stable state of about 10 billion years and then they die here is the product of the old age of a star more massive than the Sun a great nebula a star which has blown its top blown its outer atmosphere out and we see the remains of that outer atmosphere surrounding the star which is in the middle of this nebula and there are even more colossal explosions this one is called the Crab Nebula and it is a star which blew itself up in Titanic explosion which would surely have vaporized any planets that were around it at the time now the Sun will not go through such Titanic explosions the Sun will some five or eight billion years from now gradually grow become an immense distended cool red star called a red giant it'll become so large that it will engulf the planets Mercury and Venus and possibly even the earth but even if the earth does not wind up inside the Sun there will be so much Sun in the sky that the oceans will boil the atmosphere will run away to space and the earth will be slightly more unpleasant than it is today however since that is going to happen five or eight billion years in the future it is not our most pressing problem and for all we know human beings or our remote descendants will be equal to the challenges of that time after that the Sun will slowly contract and become a hot dense white object called a white dwarf which will gradually decay cool and become a cold black object in space there are many red giants and white dwarfs in the sky and here is an artist's conception of a planet in foreground which is circling a double star a red giant and white dwarf which go around each other and the planet going around both of them each object casts two shadows one white or anti white one anti red and that's a kind of different place you would immediately know you were somewhere else if you found yourself miraculously transported to that planet and here is another artists view of a red giant white dwarf double star and there are lots of them in fact most of the stars in the sky are members of double or multiple star systems so a single star like the Sun is a rarity an anomaly occasionally there are double stars which are so clothes that they touch and starstuff flows between them and around them they are called contact binaries and there are a lot of them now in the immediate neighborhood of the Sun there are lots of stars and most of them are double or multiple stars and there are a lot of red giants and white dwarfs among them but more stars like the Sun and I'd like to do a brief pointing out the stars in the neighborhood of the Sun we've made a model here which shows my no means all of the stars near the Sun but at least some of them will need the overhead lights down to really take a good look at this and so that we will have no trouble identifying the Sun we've made a lot of spikes on it it's this funny looking object the Sun doesn't really look like that but that's just so we won't lose our way in interstellar space the nearest star system to the Sun which is here is a triple star system right here two biggish stars and one small one this system together is called Alpha Centauri and the little one which circles the two big ones is sometimes called Proxima Centauri Proxima fournier because at certain points in its orbit it is the nearest star to the Sun this triple system of Alpha Centauri which you can see in the southern hemisphere is about four and a half light-years from the Sun the nearest single start of the Sun is this little fellow right here this one I'm going to touch it and make it move there he goes that wobbly one is Barnard's star and as I'll show you in a moment it is wobbly in more ways than one over here is Sirius the brightest star in the sky and over here is tao-tsay tie which is the nearest star that is more or less like the Sun and that's a single star and we talked about Tao Zi in the first lecture when I try to imagine a constellation of the unicorn in somebody else's sky and that's how far we had to go almost 12 light-years from the Sun in order to have the configuration the perspective of the stars change a little well the typical distances between the stars are several light years and the galaxy the Milky Way galaxy is much wider across than that is roughly a hundred thousand light-years in diameter now suppose there are planets around the nearby stars as we might well expect how could we detect them you can't just look out and see a planet because the planets small dim hidden by the bright light of the star nearby you have to do something special now there are several kinds of special things that we could do one thing that might happen is this we might have a device out of telescope which measures accurately the amount of light coming from a star suppose this is the star suppose the planet where to pass in front of the star we couldn't see that just by looking at the just by looking at the star but the star light is dimmed a little bit when that happens so if we connected our photocell to some ammeter like when we used before then when something passes in the way the current goes down and this now is a very big planet which is passing very close to the star so there's a big deflection of our needle in a more likely case there is a very small planet which is a much bigger distance from the star and so will be a just a tiny deflection it requires very sensitive measurements but certainly can be done and this is a kind of way of searching for planets around of the stars which is just beginning to be done now we can think of a second way I'm going to mention three ways there in fact more but just want to give you a sense of how it can be done a second way is this this the planet after all shines by reflected starlight but because it's so close to the star from our point of view it is swamped by the bright light of the star if we could somehow shield our eyes from the star we might be able to see reflected light on the planet that's called a coating or hiding the star so over here we have a planet which is not shining by itself next to a bright light which will represent a star which is shining brightly probably be several people who will have to squint as a result of this and so here we can see that the star is clearly visible but no trace of the planet because it is swamped in the light of the star now as mr. Coates slides and a coating object in front of the star we see the planet sitting there revealed for the first time and now if we take the occulting device away we can't see the planet again at all thank you both now how can we actually do this in in a real situation well the best way is to use a steady large sharp edge that's already in space to hide the star and if we're lucky reveal the planet and there is such an object it's called the moon and if we could get in the right angle the moon could just barely blot out the light from a star we might then we had a sensitive detection device see the light of the planet which goes around that star this requires space vehicles to get at the right position so that the edge or limb of the Moon our coats appropriate stars that is a second technique which is about to be exploited in the next decade there is a third technique which has already been been put to use and it doesn't actually involve a trolley but we have a Charlie here for a reason and I will shortly need a trolley assistant but not yet and let me say how this works this yellow sphere is of course intended to be a star and this black sphere is intended to be a planet you can see the star but not the planet the to go around a common center of mass so in space they move like that and imagine that we're lucky and that they are at this angle to our line of sight now you can't see the black planet but you can see the yellow star and so the yellow star is doing a kind of bobbing motion but stars also move with respect to other stars and now I need someone to help me pull up yes right here now this is very easy the only trouble is that this string tends to come up now if you would slowly pull this well I tend to good that's good you will see that the star tends to make either a spiral or a sine wave in space thank you very much now could you just push it back here thank you you have just moved the Sun there are very few people who get to do that thank you very much now that kind of motion to really pick it up you have to see a few revolutions of the planet around the star Jupiter takes 11 years to go around the Sun so you have to be very patient and make very precise motions very precise measurements well that has been done for Barnard's star and while there is still some debate on the data there are two groups who have worked on this data and each group seems to find such a motion well the two groups don't see the same kind of so they're still arguing with each other and if that is the case they have found one or more planets around Barnard star which let me remind you again is this tiny little star called an M dwarf we sort of feel sorry for it just because of the name but around it if these results are right are one or two planets of Jovian mass like Jupiter and if that's true it is a most important discovery because it's the nearest planet where we have a chance of finding such a thing because a planet going around more than one star would have a very complicated motion and it would be less easy to find out what it's about now we will I believe in the next decade or two have made a very serious and thorough search for planets around nearby stars sufficient to tell whether they're there or not if as we think they are there we will have then extended the Copernican perspective and discovered that planets are a frequent if not invariable accompaniment of stars if we find no or few planets there it will say that to our surprise is something special or unusual about planetary systems in space and that's also of course important to know now there's another approach to this problem that's theoretic we can put in the kind of physics that we think is important for planetary systems forming out of a gas and dust cloud and let the computer make all kinds of parts collide and see what happens at the end so let me show you in a moment the result of a computer program at which we've used at Cornell University which does just this it imagines a big dust cloud in which there are tiny little lumps of matter which go through the dust every time they collide with a dust particle with dust particles sticks when the growing mass becomes big enough it's gravity attracts gas when two of these growing planets collide they stick and the whole process is continued - all the gas and dust is used up what are the results well the next picture shows our solar system in a way which will be useful to understand the computer results and we have the various planets lead out for us from Mercury here Venus the Earth Mars the biggest asteroid those are the terrestrial planets and you can see their little guys and they're in close around one astronomical unit an astronomical unit is the distance of the Earth from the Sun then there comes Jupiter Saturn Uranus Neptune these are planets that have been shaded they are bigger than the terrestrial planets they're the gas giants and you can see they're out at roughly 10 astronomical units well that's the kind of system we have here what does the computer make well under some circumstances the computer makes systems like this and you can see it's almost identical to rest you'll planets enclose it around one astronomical unit jovian planets further out at around ten Estrin ah Mical units these are cousins of our solar system they're very similar and while the computer requires certain starting conditions to wind up with planets like our own the fact that with such simple physics you can wind up with such planetary systems is encouraging now if the gas and dust cloud is very thin there's not much matter around then we don't form big planets we form something like a string of asteroids all the way out or if there's a lot of gas and dust we might form a system in which there is jovian planets close in and terrestrial planets far out that's very different what they have here this is a reminder sort of system we have here and we might even have a system if we had a lot of gas and dust to begin with in which planets of such large massive is that they are stars so the computer also makes double or multiple star systems in the appropriate cases now if it is true and we don't yet know it is true but it's beginning to look as if it's true that planets are a dime a dozen you don't have a dime a sixpence a dozen we have previously found that the steps necessary for the origin of life seem to be very easy requires only the most common cosmic conditions we know that for evolution we need time but we have a lot of time there are stars which are twice as old as the Sun we know that the development of intelligence the evolution of our kind of thinking on the earth has taken a long time to come into being but it has come into being only halfway through the history of the Sun and other things being equal it is probably better to be smart than to be stupid and smart means being able to deal with the environment since we know that the laws of nature are by and large the same throughout the universe then beings that evolve everywhere must be funneled in some kind of intellectual sense if they think about the universe more or less in the same way there will be limitations of course some extent that should happen this kind of thinking suggests that not only might there be life on other planets countless other planets but also intelligent life beings as wise as we as artistic as ethical as technological interested as much as we in novels or music and perhaps lots of other things as well there should be some many that are more backward than we but because of the immense vistas of cosmic time there should be many much more advanced than we and if that's the case it would be nice to say hello to those fellows they should not look like us they will have evolved differently on a different planet and we know that evolution as a strong or random or stochastic component to it but they may think enough like us to be able to make contact well there are various ways of doing this a very slow and not not fully serious way is to put a message on a spacecraft which will wind up in interstellar space it's a little bit like throwing a bottle into the cosmic ocean the chance of it being picked up is small but it is at least psychologically good for the stranded dweller on the desert island he's making some effort to contact the cosmos the first attempt to do that was on a spacecraft called Pioneer 10 and 11 and this is a plaque affixed to the exterior of that spacecraft and let me just very briefly say what this is about this would be very brief this says here's our unit of time and space in terms of the hydrogen atom and down here it says here's our solar system Sun and lots of planets strung out the spacecraft was launched from the third planet passed by the fourth came close to the fifth and then went into interstellar space and there it is over here is a map of the positions and periods of regularly pulsing cosmic radio objects called pulsars and this part of the message says a little bit about when and where we are and then over here at the right is the most obscure and mysterious part of the message a man and the woman they of course are apparent to us but only because we happen to live here it's very unlikely that there are human beings anywhere else and so if they're any recipients of this message they will wonder very much what this is are they holding it right-side up and it will not at all be obvious that these are the creature that launched the spacecraft we because space is so empty pioneer 10 and 11 and Voyager will never enter any other planetary system so we do not know that anyone will ever pick it up and in fact it seems unlikely but one of the major reasons why we send such messages is not just to contact intelligence out there but also to contact intelligence back here to raise the cosmic consciousness of human beings and here is an indication that at least on earth the Pioneer 10 greeting was received with some degree of friendliness this is a billboard in Pasadena California now a more elaborate attempt to communicate but along the same lines was on the Voyager spacecraft as I mentioned before and what we'd like to do now is to play an edited portion of a small part of the Voyager phonograph record phonograph record you may remember has greetings in many languages of human beings and also of whales to the cosmos it has 116 photographs on the record in audio form about what the earth is like it has an hour and a half the world's music and it also has an elegant sound essay of the sounds of the earth devised by M GM of the United States and we'd like to play a little bit of that greeting to the cosmos and I think I would like maybe two people to come up here and listen to it with me I think I'll go around the front if I can and what I'd like you to do is to give me your impression of what the sounds are you will have some bias because you will be human beings having grown up on the earth and you'll know sounds better than extraterrestrials but still interesting to see how well you can do oh I see so many eager faces I don't know who to choose um can I pick you right here in the jacket [Music] you right there in the red sweater with the pullover please and let's start the Voyager sounds of our record tell me what it sounds like Laurie let's listen water bubbling boiling water explosion a house falling down a submarine that this isn't what we intended at all and if humans can't get it extraterrestrials never will jungle good we'd be on that that well we certainly have the sense of some kind of life there [Music] chimpanzee is the suggestion baboons we're certainly into primates into monkey fillings remember the city aren't talking to the cosmos chimpanzee it's proposed now the wind starts up and someone is crying a wolf wild dog there's a background noise what's that a heartbeat the first human now what it's a dog so we had a wild dog before and our domesticated any idea what this is that was actually an anvil first making of metal Morse code good you [Music] ships on pluggin some machinery is true but what a new car or an older over [Music] you think that was a crash of the car that was a jet airplane [Music] as the man said we happen [Music] and you guess that is well that's the end of this edited part of the sounds of earth I'd like to thank both of you for your help I would say that about half of what we hoped the extraterrestrials to figure out you figured out which in a way is disappointing to us because you people have a big head start being from the planet Earth but on the other hand you've just given your very first impressions and if anyone did find this in space they would be giving very close scrutiny that would work on it for many days weeks and months thanks very much for trying to interpret a signal from an exotic and distant planet in fact the general idea of that sounds of Earth wasn't perfectly done throughout was the evolution of the earth so we started out before life with volcanoes and earthquakes and rain and then the evolution of life and then up the evolutionary tree and then human beings coming in and then technology then rock it to interplanetary and eventually interstellar space and then the last sequence was a kiss very important a baby crying a heartbeat and other vital signs of the human being and then the last sound was the sound of a pulsar a cosmic object which regularly sends out a signal and is in some sense indistinguishable from the beating of a human heart a sense of tying up of human beings and the cosmos now these are fun they are not extremely rigorous ways of communicating with the cosmos one point which we might remember is that it's probably not up to us to send signals out to those other fellows since we have just achieved the technology to do this it's much more likely those other fellows are sending signals to us messages to us now what's the way to do that spacecraft traveled very slowly light travels radio travels very fast do you remember this hello universe that was I don't know if person said that is through here but that was said at the at the first lecture and maybe you remember that there was a single from the earth which we imagine going out at the speed of light by the end of the first lecture it had passed the orbit of Jupiter and by now that signal has gone about a thousand astronomical units an astronomical unit the distance between the Earth and the Sun 150 million kilometres it's got an immense distance far beyond Pluto out to the realm of the Comets it would take a typical interplanetary spacecraft about a thousand years to go to go that distance and radio has done it in just a few days between the 1st and 6th such lecture radio is the way to communicate it's fast it's cheap you can send an enormous amount of information on it and we already have large radio telescopes on the earth which are capable of communicating over immense distances this one chosen because we are in Great Britain is the Jodrell Bank radio telescope 250 feet across it turns in azimuth and in altitude and points to different parts of the sky to see what's coming from that place in the sky it has never the best of my knowledge we used to see if there are signals from intelligent beings elsewhere being sent our way but it could be so used notice the scale it's a a very large object and there are little stairways here for example which are the size of a human being and this thing's so much larger the largest radio radar telescope on the planet Earth is the Arecibo Observatory in Puerto Rico which we saw once before and here it is now it's a thousand feet across and it is extremely powerful in its ability to send and receive such messages suppose there were some other civilization on a planet of some other star which had an Arecibo so we're not imagining that those fellows are much more advanced than we and we use our Arecibo the two are moved further and further apart how far apart are they when they can just barely communicate with each other the answer is they are many thousands of light-years apart a Lightyear is six trillion miles so we have at the present time the technological capability to communicate over immense interstellar distances if only we were to show to do that there are questions for example of what frequency or station to tune to and this slide is just to indicate that this is the vertical axis here shows the temperature the amount of noise in space and here we have different frequencies or stations that we could tune to and we see there is a place where there is a minimum of noise that's the place to listen to and it turns out that many molecules hydrogen for example or formaldehyde like to give off radiation in that noise minimum so by luck there are some natural frequencies at just the place where the noise is a minimum and so by sending signals some other civilization might communicate an enormous amount of data to us here we have a radio telescope sending a cup information as a symbolic picture information on a complex organic molecule in this case DNA to the stars we might receive such a message if we used our radio telescopes properly it might be an extremely rich amount of information with our existing technology we could send the Encyclopedia Britannica to a nearby star by radio in just about a week and wouldn't it be lovely to get someone else's encyclopedia Galactica and think of see how they think about the universe what is their society like what did they look like what's their organic chemistry life what are their planets like what do they like what are their ethics about their religion their philosophy wouldn't it be lovely to make contact with another civilization that has arisen and evolved independently well one thing you'd have to do first is to be sure you can understand the message why should we expect that beings that are very different evolved in a different place different period of time for evolution should be able to send us a message that we can understand and the reason I that I think that's likely is that they in the same universe as we they must deal with the same laws of physics chemistry and astronomy as we to test the idea that a signal could be understood we did a little experiment we can only use human beings it's too bad I wish we could use some other intelligent beings to make such a an experiment but we're restricted to people they're the only ones we know about and so what we did was to devise a complicated message which you can see here of zeros and ones the zero and one might be a long and a short radio beep beep beep beep or it might be two frequencies BP beep beep beep beep might be many things but it's a language of two letters and you can see there's an enormous number of zeros and ones in fact 27,000 and something of them here you can't tell just by looking at it oh my goodness I see what this is you have to think about it now the key to this is that the total number of zeros and ones is 31 times 31 times 31 31 cubed and it suggests that it's a pictorial message in three dimensions and if we were to write it in a sequence of 31 symbols then go to the next line then you see it starts getting a remarkable regularity and so what we did is to give this message not made simple in that way to some graduate students of mine at Cornell University they were told nothing about what was in it how to decode it and their job was to figure out what it said and here they are describing the the process they went through to figure out what the message was about these are all graduate students of mine who are reasonably clever and but none of them work on this particular problem we gathered together in the Mars room and stared at it and cursed volubly a point Cathy noticed that 31 divided into 27 thousand twenty-nine thousand seven hundred and ninety one and it was determined that the remainder 961 was thirty one squared which left us with a 31 by 31 by 31 sequenced and then we sat together six of us for hours transcribing zeros and ones screaming and shouting from one office in the next and complaining about the typographical herbs until we could get the sequence which is shown frames there they were making good progress they found some errors in the transcription of this that the BBC had made in fact but they figured out how to get around that it was not necessarily a three dimensional model at first it could have been a movie because what we see what eventually turned out to be the corner markers of the cube and the lines which drew the pattern of the cube could have been just frame markers for movie or a slideshow it could have been separate frames and it was only when we had drawn them out and looked at them that it became very uncertain with there was anything like that since it was a dull movie you figured it was really a three-dimensional well that was about the size of it so here we have some Plexiglas things so one will be represented by a black square and a zero by a transparent square here is a whole sequence of transparent squares that is this would represent a sequence of zeros now building up as the message requires first space is a one which is black second space other one which is black thirdspace other one which is black and in fact it's black ones all the way across the top line so top line there is a sequence of black ones next line begins with a black one but then there's a sequence of zeros represented by the transparent markers and then a one at the end now we have the similar pattern building up black edge transparent interior which goes for a number of lines further now the next line is different it starts out with a 1 has a sequence of zeros and then there are 3 ones in the middle then the same sequence of zeros and then a 1 so here is the black one at periphery then here are the zeros next are the three black ones and then there will be zeros and a black one there and the remainder of this frame fuels in like this so we now see the picture is a black border and a kind of maltese cross in the middle and everything else blank there are many other layers and when we build them all up we result in a pattern which we will shortly see and that is the answer we can tell this is the right answer because of how regular the geometry is couldn't have gotten that by accident so here is in three dimensions what the resulting model is like now let's see what the graduate students have to say about their interpretation of this funny-looking message well the first thing that came out of our analysis of that object we've got in profile strongly reminiscent of Mickey Mouse and in fact it's gonna clear with basic and although we know that you have a sense of humor Mickey Mouse was not our idea of joke so I had to be something else the only thing it really looked like was a molecular orbital type drawing of a molecule and the first one that came to my mind was formaldehyde and Kathy is in fact right this was intended to be a formaldehyde molecule although it does look a little bit like Mickey Mouse in which there is a carbon atom two hydrogen's and an oxygen now what could the significance of that be why go to all this trouble to simply say formaldehyde and the answer is that formaldehyde has a radio frequency attached to it and what all of this trouble is about is the message is saying don't listen on this station this isn't the station that's interesting listen on the formaldehyde station and that's where the Encyclopedia Galactica will be as soon as we get that message quick we turn the frequency of our radio telescope to the formaldehyde frequency continue to look at the same star we're looking at and then hopefully get such a message that's the general kind of idea notice that if we made a serious such search and succeeded the results would be inestimable we will have ended the isolation of mankind from the rest of the universe forever if we made a serious search and failed we would have determined something of the uniqueness fertility preciousness of human being and it seems to me either way we win and there are signs in the United States Canada Soviet Union perhaps other countries that a serious search for radio signals from civilizations on planets of other stars is about to begin now one often comes upon some other ideas about extraterrestrial intelligence namely why go to all this trouble with radio telescopes when the extraterrestrials are already here we sometimes hear such an idea the ideas are often expressed in terms of unidentified flying objects and in terms of ancient astronauts now there's nothing silly about being able to fly between the stars we are already doing it although in an extremely slow pace it's taking us about 80,000 years to go from here the nearest star with our present space vehicle it's a little slow but other civilizations more advanced than we might very well be able to to do it in much shorter periods of time so maybe we are or have been visited it's not ridiculous on the other hand it's such an important contention that we should demand only the most rigorous standards of evidence and my judgement is that on the ancient astronaut business what happens is people look at big buildings constructed long ago and say my goodness I don't know how that big building was built probably people from somewhere else built it yes maybe from Egypt but not from some other star the these ideas often show an ignorance of archaeology our ancestors were smart they could build big there is no artifact in early earlier human history so far as I know which requires extraterrestrial intervention likewise an unidentified flying object there are things seen in the sky which are unidentified that's what an unidentified flying object is it means we don't know what it is it doesn't mean that it's a space vehicle from somewhere else and there ought to be things in the sky that we don't understand if the sky is very rich in phenomena astronomical meteorological optical and man-made phenomena and therefore only a very reliable sighting of an extremely exotic object ought to be considered in any way relevant to our problem of life elsewhere and to the best of my knowledge there are lots of exotic reports but none of those exotic reports are reliable for example a 30 foot diameter metallic shaped object lands in a suburban garden a seamless door opens there's a fascination of seamless doors news story a metallic robot walks out picks a flower smells it pets the cat waves to a lady hiding behind her sliding glass door turns on his heels still smelling the flower enters the UF o the seamless door closes and it takes off into space now that I would call an exotic story no question about it but when we look closely into that turns out no one in all of Long Island New York City besides the one lady noticed that this had happened and the cat was unavailable for Karara Tori evidence and that's an example of an exotic story that isn't reliable on the other hand there are reliable stories 200 people see something but they're not exotic it's a light in the sky there are no cases where 200 people see something as exotic as what I just said no cases where there's a piece of the spacecraft that someone captures and sneaks into a laboratory so we can investigate it no one has ever managed to steal the captain's logbook of one of the these supposed interstellar spacecraft and until that sort of thing happens it seems to me we must be very cautious and skeptical because extraordinary claims require extraordinary evidence it would save us a lot of trouble if those fellows would come here instead of us having to go out and find them I'm not opposed to it it's just that there isn't a smidgen of good evidence to support those ideas I wish it were otherwise and yet we live in a universe which is astonishingly rich and full of objects I keep stressing the number of stars the number of stars that make up the Milky Way galaxy is about 250 billion we don't have a picture of the Milky Way galaxy taken from outside because we don't know anybody who's been outside or at least I don't but here is a picture of the nearest galaxy like our own it's called m31 it's in the constellation Andromeda if this were our galaxy where would the Sun be would it be here in the middle where it's a central or at least well-lit that's not where we'd be we'd be out here in the galactic suburbs in some rural place where there's almost no stars not a very important significant place and there are many galaxies in fact it's not just one here there are two satellite galaxies of m31 but there are at least billions of other galaxies here is a photograph in which there are more galaxies beyond the Milky Way then there are stars within the Milky Way this is a galaxy that's a galaxy that's one that's what that's what that's why that's one there may be a hundred billion other galaxies more or less like our own if that's the case there are something like ten thousand billion billion stars in the accessible universe is it likely that our Sun is the only one of those stars which has an inhabited planet I think that that's unlikely now the time we live in is a very epical one it is a time of great transitions this is the first time in human history that we or at least our instruments are leaving the earth are going into space and we're doing this with small unmanned space vehicles very largely and here are some small unmanned space vehicles coming down from the top of the Royal Institution we have previously talked about the Viking Lander on Mars the Viking orbiter typical interplanetary spacecraft the last few years here is the pioneer of venus entry probe and the pioneer Venus orbiter to be launched this year and next pioneer 10 and 11 which had that little plaque on it right here out beyond Jupiter on their way to Saturn here is Voyager here's Jupiter orbiter with probe here is a new generation of spacecraft less noisy than Li here being described and worked on this is an ion drive to get to the outer solar system very fast and this object here looking like some great Linda mill in space is a crude model of a kind of spacecraft which is under development under study which will be a half mile or more across a solar sailing ship which will use sunlight as sailing ships use wind to travel in the space between the stars and for all I know in the first few decades of the 21st century there will be interplanetary regattas vesting with each other for the fastest time between here and Mars now this epoch of space vehicle exploration and discovery reminds me very much of the epoch of sailing ship exploration and discovery beginning in the late 15th century a tradition which England played a noble role in here is a galleon of the sort that was used to explore the what was then called the new world and what we now call the Americas but there are lots of truly new worlds awaiting exploration the benefits of this sort of exploration I think are many first off there are practical advantages we are stuck on the earth there are many Sciences having to do with whether climate geology and biology whose perspectives are profoundly limited by the fact that we only have had a single example to study when we look at other planets the powers of these formerly earthbound Sciences are tremendously increased I believe the entire cost of unmanned planetary exploration which is very inexpensive compared say to defense budgets is returned many times over by the ultimate practical advantages in addition we probe the deepest questions we ask about the origins of worlds and life we explore our surroundings in space every human civilization has asked questions about what is up there now for the first time we have a chance to find out and finally human beings are a curious inquisitive exploratory species I think that has been the secret of our success as a species we now have reached a point in human history when all the earth is explored there are no new places to explore on the earth the possible exception of the ocean bottoms at just this moment these spacecraft permit us in a halting tentative preliminary way to leave there and examine our surroundings in space an enterprise which I believe is in the truest human tradition of exploration and discovery we are as I said at an ethical moment our our machines and eventually ourselves are going out into space I believe that the history of our species will never again be the same we have committed ourselves to space and I do not think we are about to turn back I believe the time will come when most human cultures will be engaged in an activity which we might describe as a dandelion going to seed artifacts from earth are spinning out into the cosmos and human beings will never again be restricted to this one planet [Applause] you

Channel: mrnobodysprincess

Views: 56,007

Keywords: Carl Sagan, christmas, voyager, contact, aliens, alien life

Id: Vn-Njh1Iz7M

Length: 60min 0sec (3600 seconds)

Published: Mon Dec 12 2016