The Limits of our Knowledge



so welcome everybody this will be my final lecture in wonderful series that I've enjoyed very much I hope the many of the followers and attendees appreciate this so I'm going to address today a definitive question about how far we we can go how far we understand the grander themes of the universe and I'm going to touch on various things that involve the past and the future the very long term future – but let me begin with a wonderful quote by Donald Rumsfeld as we know there are known knowns there are things we know we know you also know there are unknown unknowns but there are also unknown unknowns the ones we don't know we don't know and of course this got him a certain distance – in the past but I want to there's so much that we aren't aware of and that we are unaware we are unaware of if you like about the universe – and our future etc and I'll try to explore the stuff that we at least do know that we don't know in this talk bearing in mind there may be stuff that we don't know what we don't know okay so the our place in the universe I want to give you some feeling for that and then you know I I work on the the large the large things in the universe and basically what the ER is made of I'll touch on there the matter the energy and then greater things which I think could make a profound difference to humanity life felt the alien life and in the future of not over the next tens or hundreds of years but the very long term future for the earth that I'll give you some thoughts on that okay so let's begin with this wonderful drawing by Robert Fludd made around the time the Gresham College began really and he was a physician an astrologer mathematician the cosmologists Kabbalists resolution many things which one could be at that time it's harder now to combine all of these disciplines although I I can think of one or two people who try but anyway he he was profoundly influenced by the idea that man Humanity is at the center of the universe and this was at the time really when the Copernican revolution hadn't happened hadn't quite happened and so there was much debate about whether the earth was at the center of the universe etc and it got displaced by Copernicus around this time for the Sun being at the center and since then even the Sun has been completely Stitz just one of many many stars out there but the notion that we are central you know and our perception is that everything else out there maybe is humanity related perhaps we're very wrong there may be some very unusual interesting forms of life out there perhaps we've only come to realize this in in recent years I'll tell you a little bit about the logic behind that but the thought that man is central goes back a long way and it even influences us in cosmology because we feel many of my colleagues feel that it's hard to imagine a very different universe without which might be hostile to life emerging in it the conditions might be too hot too cold it's a bit like you know the story of the three bears you know call you lots of three bears that there is a place that's just right right all the point is just right the right temperature so it could be the universe is in that way connected to our presence and that's a theme that is very very common in cosmology we don't we actually don't know the answer to this but it seems that this is probably a way more of understanding a lack of the final theory of the universe because if we already understood the basic laws behind it we maybe might not need to put our presence in such a central role and our thoughts about you know the grand scope of the universe but but let's begin with this beautiful vision of which has been called the cosmic uroboros and so here you see all possible scales that we study and conjecture about and so let me take you from you know the many many millions of light years as far as we can see that it's a galaxies down to sub atomic scales okay and then the scales of humans over here meters scales that's what we sort of are on the scale of the Sun okay and then and the scale again of the very smallest scales getting down to microphysics the fundamentals of what maxims particles might be made of so from larger scales all the way down to stars galaxies then planets people sub subatomic stuff the famous Higgs boson discovered a few years ago the missing link in particle model of particle physics the fundamental model big unknowns like dark matter comforta moment all of this you know one one beautiful circle okay one has to understand all of it to make sense of any one of these actually that's the message behind this and we're sort of a long way from this but at least we can get some feeling for the general scheme of things okay so the maybe the greatest personality in all of modern cosmology was a very unlikely person a priest who got ordained after he got his PhD in physics studying black holes actually at MIT but there's a Belgian he went back to Belgium to live there and eventually he was became very well known in the Catholic Church he was the primary scientific adviser to Pope Pius the 12th and he in fact largely wrote the pious the 12th the famous text which describes the first views about the universe that said it's fine to have the Big Bang exaggerated so perfect world to combine science with them with religion if one sort of separates the beginning after the beginning with all the beginning that was basically the matrix you anyway in his notebook in the mid 20s he sketched his ideas about the universe based on the newly developed theory of gravitation by Einstein's general relativity and so in according to this theory one could figure out the possibly histories and possible futures for the universe and so these are a number of different models that the Metra sketched out in which the size of the universe is shown here and it's it's growing bigger and bigger and that means all the guys all the space we can see around us is growing but gradually slowing down in this model and then collapsing to here we call this now the Big Bang this would be to be Crunch that was one possibility a Big Crunch awaits us right which you know it might be bad but in a few billion years perhaps and then there are other models which keep on slowing down due to gravity and then but just keep on going forever and this is a bizarre place too because that means the future be incredibly diffused and cold no more stars could be seen whatever everything bits are far away and then an even more intriguing suggestion totally radical at the time was that in the future the universe might begin to speed up and get even bigger and bigger and then not only will you not see the distant stars who wouldn't even see our near as galaxy everything would have moved out of our possible vision region that we could even see and so these were three different possibilities and and so it took you know fifty years half a century and there were endless debates about whether this idea of an accelerating universe made these sense at all and so Einstein who famously could speak French among other things was exposed the metro told him about his theory in 1927 of solve a conference and Einstein said your calculations are correct but your physics is abominable okay so he just did not like this ugly notion that certainly after the past and the presence of the Big Bang the universe was so he begins speeding up again that involved a new force okay in nature but the maitre did persist with his theory and his and his and his arguments the first thing to do was come inside Stein that the universe even was expanding because at the time and I made this common the idea of a static universe seemed so natural there was no evidence you know that said that wouldn't be the case but eventually the case was made within very few years and you see Einstein this carefully post photograph with Edwin Hubble and on Mount Wilson looking at something who knows what a star or something and Hubble was the person credited with discovery that the distant galaxies are receding from us the expansion of the universe and and within a year or two Einstein and Lamech are going on lecture tours around California and after one of them Einstein said this is the most beautiful and satisfactory explanation of creation I have ever listened to okay that was Einstein's or the maitre sign Stein it was a flexible man he could change his views he realized the evidence said things are moving away you know static and he accepted that but there was one more part to the story which is do with the stuff that we don't see so I've talked to you know we all know there are atoms out there that make the stars that we see far away to make us and there is this stuff called dark matter I'll show you explain examples that in a moment but even more than dark matter there's a mysterious thing called dark energy which is what is causing this very relative recent speed-up of the expect of the universe and it's a mystery it composes most of the mass energy of the universe 73 percent or thereabouts and the sad thing about all of this is we have not the slightest understanding we think we understand atoms pretty much but we don't know what the dark matter is we don't even know what the dark energy is so this is one of the biggest challenges to our current understanding of physics okay so let me say a few words about this mysterious stuff which dominates everything we call it dark energy because we can't see it directly and it's got energy it's got it it acts like anti-gravity it's like these magic stuff they can push the universe apart and so the reason it is out there and does this is that what we think of being emptiness we call it the vacuum is actually not really a vacuum at all it contains a tiny tiny amount of energy because little particles come and go all the time but a timescale so short it isn't so sure that there are measurable and because they come and they go energies can surf we're not violating anything we just got measure it but they're effective they're coming that gives you a sort of a pressure we call this the pressure of the vacuum and it's a prediction of the quantum theory and so now pressure ordinary pressure gas pressure the pressure of a gas it does have energy and it it attracts it's like gravity but if I have but this mysterious quantum stuff is anti-gravity let me just try to explain why with this very simple analogy imagine a piston compressing a gas that you get more pressure but the volume is smaller so there's less of this mysterious quantum stuff but now if the piston goes the other way and you expand you get more and more volume okay so ordinary pressure goes away but there's mysterious new pressure from the quantum theory suddenly gets bigger and bigger and bigger and that is what the Metra speculated about and finally was measured half a century later by astronomers okay and so we believe it is accelerating but again this is you know we go in circles here because there's a problem with this it turns out that this weird stuff which is accelerating you knows is due to what Lemaitre called the cosmological constant is anti-pressure it's only coming into play now it's a tiny tiny pressure I'm in the present roughly the present age of the universe but the physicists who work on the very early universe extreme states of matter they can estimate the strength of this if this field and they think it should be enormous ly larger just from the way high-energy physics works and we've called this this over estimate it's its enormous it's many many factors of 10 I can't even count all these trillions for you but it's could being called the worst prediction or the physics what if this this acceleration should be and what we actually measured it to me so that's just one more example of how little we know and the response of the scientists has been you know that we need a new theory that combines gravity and the quantum theory so far I had no success Stephen Hawking spent much of his life wandering wondering about this and didn't get anywhere on this theory Eddington before him likewise and Einstein even too so we're waiting perhaps for a new genius to emerge who will tell us what what where all this may be coming from and you know if you think about this all of these figures you know basically the past century so we have a long way to go I'm I'm optimistic we'll find the solution and we'll come to how long a time skill we may have to wait in a moment before then let me tell you about the other mystery that perturbs astronomers greatly because we measure these things out in the sky we measure their effects but we don't know what we met what we're actually measuring so now let's get on to dark matter which is a bit more tangible than dark energy because dark matter is everywhere we think it's in the Milky Way in our galaxy or if dark energy is so small it's locally I measure it only comes to play on very very far away but dark dark mass matter is there and so this is a for example an image of a galaxy like our own and all this stuff around it is dark okay and so that we know this because we measure the speeds of these stars and they basically are simply moving fast and they should be being accelerated by some stuff around us and so these are the two pioneers of whom first invented measured this effect way back in the early 50s a ver Rubin and more Robert she used optical telescopes when the first women to basically go into facilities on top of high mountains Mount Palomar where there were no facilities for women actually so for her it was really hard work she had to go down every night and Roberts who was a radio astronomer measuring much the same thing but further away from the galaxies measuring this weird extra force that seemed to you know soon became alleged to be dark matter and so that's the evidence for it and there was another astronomer way ahead of his time very unusual person a Swiss American called Fritz Vicky subtly pastino eventually who measured these things so this is this is a galaxy hundreds of thousands of light years across this is a cluster of galaxies many many galaxies these are millions of light years across not again these will fly apart were it not for dark matter so dark matter seems to be pervading stuff it dominates all the ordinary stuff they already stars it's out there we and our mystery is today that we don't know what it's made of so let me just explain very very briefly how we measure how we're so certain it there there's simply no challenging this so Einstein is one of his great predictions was that when you look with with a telescope the skater Space Telescope in addition star then if this if there's an intervening galaxy full of dark matter basically the light gets bent that light paths get pushed around by the dark matter just like a lens dark matter acts like a lens because it basically dark matter bends light paths and that's you know that's what you know geometry is a manifestation of gravity that was Einstein's great thing okay and so but they're practically proof of that this example is that he predicted that you should then see this galaxy imaged from this side and from this side and if you think about it what you expect to see is a circle in the sky and so we've measured these just in the past few years it took a century to get to this point roughly with exquisite telescopes post Einstein right and finally we've measured these amazing we called mine Stein rings which is due to the dark matter in this galaxy here bending the light from one galaxy way behind it and you see this beautiful circle in the sky and we see this now not just on the scale of galaxies but also on a whole cluster of galaxies again thousands of galaxies orbiting around each other like you know a swarm of bees or something if you were but held together by gravity and we know it it's there because again we can see this amazing from one galaxy if you look right get the geometry right you see this amazing ring and the other original distorted too so it's it's it's an amazing story the dark matter has to be there but the sad thing is that we have no theory as to what the dark matter is made of it's most of the matter in the universe it's surely some elementary particle but it must interact really weakly with ordinary matter we imagine because you know we don't have huge amounts of it on the earth right it's very very sparse in the solar system but out there in the largest basin it's the dominant form and we just do not know what it is we're looking for it desperately but so far we haven't seen it that's another example of our lack of knowledge at the moment but again you know we've only been doing this for a few years looking for it for a decade or there abouts and there's a lot of time ahead of us again I'm optimistic that we're going to be seeing this eventually okay so they'll let me take you to another mystery part of which we have made a lot of progress in and this is the birth of a star and eventually the birth of a planet and the birth of life okay so let's just begin with a star so what you're seeing here is a dark cloud in the Milky Way it's dark because it's full of dust and very very cold lots of gas and this is the womb for stars to form and we know this because we're the special telescopes designed to peer through the dust by looking at me infrared we can see tiny stars forming and this is an example of one of them not in this particular cloud but just I said proposed it for you and you can see this actually is is a disc around this bright thing in the middle moverá it's gonna condense we think into planets so it's the birth it's a star actually being born we're convinced and we can see this many examples of this around us now and so this enables us to understand you know pretty much how stars are made and then the next thing we've been looking for a planets around all these other stars so you know we have a few planets around the Sun right the earth being the one that we know has got life on the only example of life on a planet in the entire universe that we have at the moment okay and you know we're on it we're in it we're the logical end product of that in the solar system there are a few other planets but we don't think they're very congenial for life mercury for example you know it's like an oven basically you can possibly imagine live venus bit further out a bit less hot but you have clouds of sulfuric acid it's a nasty place to be I don't think there's any life on Venus the earth that's great Mars you know no atmosphere it doesn't know water there is evidence there was once stuff in the past water rivers maybe there was life on Mars a long time ago that's why I want to go to Mars nothing much on the surface but we have to dig deep in the surface of Mars and maybe we'll find evidence for fossil life who knows one of the grab but then beyond Mars we've got you know giant planets like Jupiter that's just a gigantic ball of methane and ammonia and stuff like that not exactly where you'd think any life could be and so on and so forth Pluto another ball of ice out there but what we'd like to do is to look at other stars to get more examples okay and so there are wonderful techniques now with new telescopes to look for planets around other stars we call them exoplanets and it's been a field that's developed incredibly rapidly over the past 20 years and so you know the first exoplanet was discovered around yeah just just 20 years ago actually and now we're up to several thousand of these planets around nearby stars and we find them just because with exquisite position you can see a dark spot you know particularly as a star that's one example occultation in other ways the star move wobbles slightly and infer it's you know it's due to a companion that you don't see we just planets eyes and so forth so lots of these planets now some of these planets are much bigger than the earth and some of the planets are smaller than the earth but there are an awful lot of stars out there so this is a recent map by a satellite called Gaia which map the positions in detail of billions of stars in our Milky Way galaxy so each one of these stars most likely has many planets just as the Earth's our Sun as many planets so we're talking about in our own galaxy they've learned all the other galaxies out there you know there are many other billions of galaxies too but in their own galaxy within reach as it were of some you know future capability in rocketry advanced rocketry you can pretty much reverse our galaxy in if we wait long enough we'll do that in the future there should be a lot of exoplanets around each of these stars and the question then how many of these are going to be like the earth so here's an example of comparing the sizes of these planets so you don't want the planet to be a massive ball of cold gas like Jupiter or very hot rock like Mercury and you want it to be roughly the right distance so this just shows you the range that we have at the moment to compare the earth these are the size of the earth compared to Jupiter Mars etc so here are the sizes of lots of these planets have been discovering over the past them 20 years and you can see we're just getting down to the point where we finally have the ability to measure earth-mass planet so but the early ones with Jupiter type Cupid which we're not interesting for life searches but now we can measure earth mass planets we have a few quite a few of those but that's not good enough right what you want are twins of the earth okay you want planets which are at the right distance from their host Sun the host star to be not too hot and not too cold right and basically also but that's the Louie one that's that's a starting point you want them to have oxygen atmospheres and so forth and and water liquid water and then when you have all of this stuff present which in principle we have ways of detecting by searching for these signs on these planets very carefully then maybe we would get closer to understanding if the the right conditions for life elsewhere okay so that takes me to my next theme which is that we would very much like to know how pervasive life is in the universe there is to say are we unique on the earth did it happen just once or is there given the right conditions and with all these exoplanets some are going to have the right conditions that's that's completely the same as the earth did there for sure hundreds thousands of them probably not not the billions that many of them are too onto gold but we certainly have a few thousand out there that have potential you know harbors of life if life could develop and we have not the slightest idea unfortunately what basically triggers life so first of all this is the Goldilocks issue but this is not a problem you want to make sure that you find a planet and they're beginning to find them now where conditions are just right in what we call the habitable zone around their parent star which not too cold and it's not too hot and the planet you know typically is going to be roughly Earth's are just going to be a rocky planet not a ball of gas which it might be further out full of ice etc so you know with beginning just now to find these things okay so but we want more so that's possible for life so I'll come in a moment now to what it takes to make life but what we really care about is not just life okay it's fine we find a planet full of you know bacteria or viruses that's not terribly interesting what we want is intelligent life because we'd like to communicate with other you know beings in the universe if there are any aliens out there be great to develop something we could learn a lot more science more rapidly maybe because think about it you know the Sun billions of years old but our there are stars out there there are billions of years old in the Sun many most stars old in the Sun the Sun is you know roughly an adolescent on the you know compared to our galaxy there are older stars out there many of them which would have planets and those planets would have a big advantage over the earth so if we know life happened once on the earth okay it occurred once but the question now is you know more commonly and if it were more common then it could have a big advance over anything that happened on the earth except for one rather sad possibility that we are rapidly destroying the earth as we all know right so you know it's not clear that we will leave the earth behind with finished polluting it etc etc having nuclear Wars or whatever may happen you know in the next century or two that we will have a very stable you know an advancing you know civilization we have we don't know okay right so let's now come back to the story of how likely life is so the pioneer was Darwin of course and this is a sketch that he made on his initial cruise around the world apricots and other places in which he invented what we now called The Tree of Life he called it the Tree of Life too and so the idea is there was some Universal common ancestor and from that that would have been some simple organism actually and from that developed all these various more complicated things from bacteria to fish to mammals eventually to man so so let me here's a beautiful quote from Darwin so he he imagined this this warm little mud pond with all sorts of ammonia and phosphoric sorts light heat electricity and the protein compound was chemically formed ready to undergo still more complex changes and that could be hell life began that was the vision and we still have that vision pretty much so first of all around the time of Darwin one of his fellow scientists developed this slightly more sophisticated version of the tree of life and and in it you can say we basically have you know plants and bacteria type things and animals and with man somewhere at the top of that tree and here's a modern more colorful view of the same thing where you see simple single-celled organisms and the bacteria which may be closely the most closely related things to the Universal common ancestor right of all life right the cells that form first life in this primordial mud pond on the earth you know okay and we need we need water that's critical to have the cells move around together to protect you from ultraviolet that's where the mud comes in and those are the sort of ingredients that are the proteins that makes them build up more complex stuff and eventually lo and behold you finally get up to algae and plants and one of these and the fungi which are truly very important in the in this school of things and then finally we have you know us emerging from all of this ok so fine so we cannot we do not know scientifically what the odds of this happening are but it's reasonable to speculate that you know it happened once that's for sure and given the conditions that I've imagined Darwin imagined it could happen on other planets and now we have all these other exoplanets twins of the earth out there we will have many more soon and there are probably millions of these possible sites for life in our galaxy so let's ask the following question suppose it were true we can't calculate this but suppose it were true that life really was common out there in the universe not other exoplanets and that you know it had in many cases a huge advance on us right millions even billions of years it didn't self-destruct life was clever enough to to survive an advance and become scientists became clever and clever of the generations the computers will come to the second got bigger and bigger etcetera so travel was no problem for them so the question is where are they right they should with they should be around here somewhere these advanced aliens and so this was first asked by a physicist called Enrico Fermi who was one of the fathers of the atomic bomb incidentally but you know he did other things too and he remarked don't you ever wonder where everybody is right if there are all these advanced aliens out there they should be propagating around the galaxy like crazy and highly advanced spacecraft and they would have come to talk to us maybe they wouldn't have a language in common but they might have left some artifacts that we know and so he then you know did a series of what we call back-of-the-envelope calculations and he said at the end of the day you know they should have been here many many times the fact that we haven't seen them and found no evidence of them means that they do not exist ok so that was the conclusion from the lack of visitations ok now over the years we've tried to make this argument more quantitative right to calculate you know how many generations there might be would there really be so many coming to the earth could it have been a rare a thing right so this is a radio astronomer Frank Drake wrote down an equation famously known after him and this equation purports to calculate how many advanced civilizations there are out there on distant planets distant stars and so it involves things like the number of planets like the earth the lifetime of any civilization on such a planet allowing for its possible self destruction and all the other various factors very not being too far from its host or etcetera etc and the trouble with his calculation is that you can imagine every factor in it except maybe they don't make the planets which is finally beginning to hold on every other factor is totally unknown so if you start multiplying you know unknown coordinates by unknown quantities you don't really get very far so that means that we just don't know how to calculate our response to Hermes question where are they maybe they're very few and of course another answer might be that these highly advanced civilizations have learned you know we're just a zoo for them you know the human Zoo and maybe we they've developed in such a way that you know we wouldn't notice them you know they would be communicating in some dimension that we cannot yet understand and being invisible to us that's another option that we have no no way around okay okay so there's another point I want to make so I've said you know could humanity be a unique fluke an accident that I've talked about is there alien life in the universe we've said a bit about that but there's another aspect to this which is intelligence and consciousness right which differs makes us different from animals and so if you want to explore the origins of life you have to you have to worry a little bit about not just whether they could be life out there whether how it developed you know intelligence etc so what I'd like to argue is that this is not really such a major problem I think but it's highly debated among my upon my colleagues and I'm knowing me by no means an expert I mean this is the realm of neuroscientist among others but let me just give you a brief overview and so the question is does the brain the human brain development of that eventually engender consciousness well obviously they go together but what about you know animals you know your pet dog is is your is your doggy okay conscious in the way can it you know recognize itself in a mirror I don't think so actually be self-aware that it's seeing another dog so his experiment that's been done on mice actually in the laboratory so you know in it in the brain of a mice which is much like our brain just a smaller version there are these brain cells and they fire electrical pulses called synapses and and you can study a mouse walking around with micro cameras etc this was done by the Allen Institute for brain science in the US and you count the number of synapses and the mouse brain as something like ten million of these flashes that tell fresh is going on or anytime and so that is the degree of complexity of a mouse the mouse sort of stops here and sniffs or better moves on etc etc well one can upgrade this we have done experiments on the human brain but you know it's much the same many many brain cells many synapses and the numbers are a lot larger so it's about a thousand trillion ok synapses in the human brain millions and millions of times more complicated than the mouse brain ok so that's for sure but the point I want to make is that these flashes these electrical cells are something that we're able now to try to replicate with computers these numbers not are a border of what we can do artificially now it does get a little complicated because these brain cells are not randomly arranged there they're in there they're in lines and things and and north nerves actually that spread things out and so all this makes it very very complicated it's more than just what I'm gonna tell you is a highly simplistic version it's more than just counting numbers but to give you the flavor of the thing let's count numbers so here is the most powerful computer supercomputer on the earth ok it's in Oak Ridge Tennessee here at one of the u.s. National Labs the Chinese held the record the year before it's entered there hold it next year but right now it's the u.s. there's a record and this particular supercomputer can do more almost as many operations as the human brain in terms of these operations these synapses that I call them so basically it's let me try to get my trillions right this is ten thousand trillion bits bytes that this thing can do operations but multiplications if you like instantaneous aim time so that's one that so that tells you that right now the computer and this computer is the size of two tennis courts so we're not going to talk about stuffing this one inside the human brain but computers like this have similar power to the human brain except that it's more than just brute force of course the human brain as I said as these cell these snaps is carefully arranged it's much more complex than just doing random numbers but well you know we have to think about what the future may hold for us so this is you know 2019 that we're looking at this so I would bet you that within 20 years time for example if you remember will miniaturize this so remember the size of what was the most powerful computer and say 1950 when we first developed in the UK and elsewhere those computer filled entire rooms and they now can fit inside your mobile phone or less right so we've learned how to miniaturize so I would expect that within not that many decades we're miniaturizing supercomputers like this to fit inside you know the human brain or a brain or you know so one can presumably replace our brains eventually by by computer transport C etc so this gets us into interesting territory if you project ahead right now in brute force this may be compared to the brain in power brute power but nowhere at all it's the situation the fist occasion that's needed but that will happen in the future as humans grow more powerful so this leads us into the other related question which is weak one can imagine a future in which computers basically if you don't dominate everything so if you think of a human with an hour nod a computer brain it's a robot basically so robots at some point in the future within some people say within thirty years I would give it a few hundred years whatever will basically be able to replicate everything the human brain can do and do far more and that can only get more and more complicated in the future in the future so this leads us then to what would one do with these amazing amazing computing systems so this has led to the of studies of a field called nanotechnology which we're beginning to exploit in fabricating cosmetics for example various things but basically the idea of this goes back to richard fineman one of the greatest physicists of all time who realized that you can rearrange atoms in principle he didn't actually do this it was a concept he had the way you won and so this means that you can certainly if you can rearrange the atoms all the way down to atomic scales you can suddenly do things and so you can make mass-produce things identity sweet to each other you can Bruce factories basically that would make things anything you like if you can learn how to rearrange the atoms and this and so and everyone will be a perfect copy of everyone else so this concept has been called is called nanotechnology and it's been applied by thinkers about the future futurists to imagine how you would take advantage of this so that this for example what one idea was that these many factories of raised atoms able to to think and do things to take photos to do miniature operations for example could roam throughout our bodies invading cancerous cells rearranging their DNA they could cure cancer right the vaguely and they could also nanotechnology has been imagined you can make mini factories by having so many of these atoms replicate themselves and replicate machines you could imagine constructing buildings so imagine this they might swarm as a barely visible metallic sheen over an outdoor construction site in a few days and they're looking building would take shape every our entire factories no larger than a grain of sand might generate billions of machines like a massive dust streaming steadily from the factory door so this is the future of nanotechnology in principle we there's no law of physics that says happen and it just seems likely if you think what might happen in 100 years time now so we've discussed brains systems that are much more powerful than the human brain so the other thing you have to worry about is is this I showed you some advantages but this could be a bad thing – there are downsized this as well and and some of my colleagues worried about this so are they a threat to humanity or a boon to humanity and the aliens out there who if they are there would have had so many more millions of years and ask to evolve by this argument they should all be basically robots the word used is posts biological right they will have you know they were they will be out numbering any you know rare human type beings among them or so this seems hard to avoid so they've been various books about this recently in the past so that the trend began with Ray Kurzweil who is an engineer who works for Google actually and so he forecast that within a decade or two artificial intelligence would overpower the human brain and he called this you know a threshold a future threshold and once one got into this production a lot of his intelligence things were then exponentiate was start doubling every year of you know there would be nothing to stop the rise and the spread of this increasingly perfected intelligence superior to her own he called this the singularity another of my oxford colleagues philosopher Nick Bostrom has worried a lot about the negative sides of negative aspects of this and forecasts doom and gloom because humanity as we know it would possibly be at risk the the downside of this might be to destroy certain things not everyone agrees here's one of my fellow aggression lectures who gave a lecturer lecture last week so you may have heard who has a very positive thing he thinks the positive aspects outweigh the negative aspects but the basic problem is what one is called the gray goo problem so let me just summarize this is the endpoint of nanotechnology so within a few decades machine intelligence will surpass human intelligence implications include the merger of biological and non-biological intelligence immortal immortality waits for us so that's Ray Kurzweil view but the bus from view is is more bleak we humans are like small children playing with a bomb he writes our demise may result from the habitat destruction and choose when our intelligence begins massive global construction projects using nanotechnology factories they'll just destroy the environment so we'll be left with it'll be the ultimate catastrophe for for what we know and love on the earth ok ok so let me sort of begin to close with the words of another great thinker about the future again let's take a more positive view about what this may hold so what any futuristic advanced civilization must use is energy ok and named after Freeman Dyson there are Dyson spheres and these are thought to be a way of capturing the energy from the Sun now the sun's energy is wonderful Solar is a great energy of the future but think about it most of its gets gets wasted it just goes off into space tiny fraction except the earth and in a country like Germany now we have 40 percent of their energy is now solar the UK is rapidly developing as solar cells become you know low despite the weather in Germany that seems to work but you know the future that's the way will go but if you could imagine the Vance civilization they would capture much more from their Sun and then we could look for these by seeing weirdly glowing spheres in space faraway stars that aren't really stars but are so much bigger than the host star buried inside that's Dyson Sphere of capturing devices that then recycle the energy but they would just have a different signature and so that this conversion of starlight into infrared photons be a way of looking for advanced civilizations we're exploring this option no one has found one yet but you know we are just beginning to develop our advanced infrared telescopes and then what about the aliens okay so how would they find us okay interesting question this is how the earth looks earth rise on the moon I imagine this is one reason you'd want to go to moon when hotels will be built there in 20 years time to spend a night and watch watch earth rise be an amazing experience I'm sure but the earth cannot hide okay so this is the earth at night so this is one way the earth will reveal itself as an intelligent base because this is not you know random fluctuations of fireflies right this is you know electric elimination of vast cities so we can't hide ourselves so again if they were advanced survivors out there they would certainly be able to okay so how do we cope with all of this well so here's one interesting story you could imagine immortality I said is one of the hopes eventually from you know eventually replacing up rains with artificial brains I mean that will come eventually I suppose but what about people now what can you do where there's a company in Boston that will offer to freeze you after you die and conserve you know of totally being you know have your ashes dropped in the sea or something that this is designed to create freezer and then wake you up a hundred thousand years later and there you are you'll be you know be reinvigorated no doubt by the advanced technology so of course this assumes the country doesn't go bankrupt in the mean time but nevertheless here's examples of these parts they actually have in Boston in this company and here's another example of my colleagues in Oxford who have paid a certain sum the company charged about fifty thousand dollars further for this and so that they've paid to be cryogenically conserved when they die and there's a cut-price for head only and you can see that two of my colleagues including nick bostrom majored earlier of you know just will just have their heads frozen later so anyway that that's one thing philosophers are doing these two philosophers two practical people to worry about how to cope with the future there okay so let me close with this these ideas go back a very long way okay about what else there is out there so I'm going to just quote a couple of very wise and Greek philosopher scientists it's in the highest degree unlikely this earth and sky is the only one to have been created nothing in the universe is the only one of its kind that was the critius and metrodorus also you know fourth century BC to consider the earth as the only populated world in infinite space is a as absurdist to assert that an entire field song with millet only one grain will grow so you know beautiful words we still cannot prove any of this be sure of any of this and the only answer I think is that we have to look okay so we have to keep on searching for these extra planets looking for signs of life on them eventually which we can do with advanced telescopes and who knows if we're clever enough we may even find signs there's more than just you know oxygen in the atmospheres there may be the signs such as you know lights flickering or whatever dyson sphere's signs of intelligent life we simply don't know we have to look so I encourage all of you to support our scientists astronomers are out there worrying about what else there is in the universe and maybe they'll tell us something someday so thank you you

32 thoughts on “The Limits of our Knowledge”

  1. One of the most tedious lectures I have heard: nothing substantial, nothing new, nothing interesting was said.

  2. 35:22 – of course the claim they've not been here you would have to discount the massive number of alien sightings… some of which comes from incredibly credible and well respected sources… which include high ranking service personnel and civilian pilots… some of these sighting aren't merely something that can be natural.. light a light high in the sky… but are clear technological object, like large floating craft or flying discs performing complex manoeuvres. Now, it is entirely possible these are false… certainly some are… but can they ALL be false? Maybe… but they are a possibility. It might just be seen as highly irresponsible for any technology advanced civilisation to land openly and say "take me to your leader"… and their tech is so advanced that they are able to be here one minutes and silently gone the next in stealth. After all… if they can reach earth and safely travel through that much space, then they have a certain mastery over the laws of physics that we most certainly do not!

  3. Certainly shows that we know very little of releality. Maybe robots are already in charge. A handful of men owning more and more of the worlds physical resources, even less controlling information. I wonder how much science is being withheld.

  4. ok, but if we were the size of a nucleus and somehow could be sentient would we not find it strange that the mass of a nucleus was less than the sum of its parts? Can we clearly explain how a bunch of particles can be more massive than the whole form in a nucleus other than saying E=MC^2 and nuclear binding energy? Is it really necessary to have dark matter to make up missing mass?… if we accept a system can be very different to the sum of its parts on the atomic scale, then are we sure that new physics might not come into play for systems that are as bigger than us as we are than an atom? I think perhaps Newtonian physics is only really good for our size… obviously in the quantum world that falls apart…. would it be surprising that on a larger scale that world could be as vastly different as our's is to the quantum world? Our Newtonian calcs may be off. At the moment we seem to just be assuming quantum world, the big world we live in… two different types of physics. Might not be the case at all!

  5. If you're going to show and read the quote, you need to get it right. I mean for goodness sake, it's right there. When you mess it up you lose credibility, not a good thing at such an early point in a presentation.

    And of course, the problem is unknown unknowns, these are the things which we truly do not know, and we don't even know we don't know them.

    But then again, I think it was Ronald Reagan(or maybe it was someone else) who said something like, the problem isn't what we don't know, it's that what we think we know is wrong.

    The worst thing one can do is persist in doing/knowing the wrong thing simply because we believe it to be right, it's worse than ignorance. Ignorance is simply not knowing, something which can generally be corrected with education, what's harder is telling someone what they know is wrong, first they have to unlearn what they have learned(a very difficult task) before learning what is right.

  6. "Does your dog recognize itself in a mirror? I don't think so really." No, perhaps not. But your pig does.

  7. Its not absolutely impossible at this point that man STILL is at the centre of the universe and that this universe is made for us. I wouldn't want that…. I'd like to believe in aliens… a vast cosmos of life ready to explore and learn about. But, when you have a sample of errrr….. 1. Its very hard to know whether we are a random rare event… in an otherwise dead vast place. I think its more likely based on what we know we're not. Life started pretty quickly on earth! There is nothing truly remarkable as far as we know about our system…. but still… its not impossible that some random quantum fluctuation by a one in a trillion trillion chance formed a pattern of behaviour that lead to life…. and we'll only exist where we can observe ourselves… so here we are!

  8. Alien pilot to Alien commander. Sir, you are flying too close to the earthlings cameras, what if they see us?

    Alien commander: Don’t worry soldier, even if they see us they won’t believe they saw us.

  9. There is no physical life out there . There is heaven a spiritual realm . The universe was made for man with LOVE .

  10. the context of the universe is spiritual consciousness which flows from the top down creating physicality…as a secondary event a for detailed starting point leading to enlightenment.

  11. The universe had a beginning. Since the 1600s scientists believed the universe was eternal. Einstein's general theory of relativity predicted the universe had a beginning. Einstein did not like that and changed his equations because of His dislike for a beginning because a beginning requires a transcendent causal agent. This has been proved mathematically. Edwin Hubble's work at the Mt. Wilson observatory showed that the galaxies are moving away. Through interpolation our universe began about 13.8 billion years ago. The first sentence in the Bible says, "In the beginning God created the heavens and the earth." The answer is obvious. All you have to do is open your eyes and stop hardening your darkened heart.

  12. Most intellectuals beleive we live on a spinning globe. We think we have come a long way, but we know NOTHING.

  13. we do seem to be at the center of the qauntom universe .we alone doctate if its a particle or wave even both .simply by observation.

  14. What a beautifully delivered .. and quite frankly honest lecture! … Plenty of food for thought 🙂

    Thank you 🙂

  15. You quoted Donald Rumsfeld, a known warmonger of the Bush administration.  What we don't know is why you chose to memorialise such a war criminal.  [Aussie in BC]

  16. Lol. I think this "Unknown" saying attributed to Rumsfield actually predates his saying of it and is put in a more graceful form of prose. I am paraphrasing it here from my memory many years ago. It says: "There are things we know we know… and there are things we know we don't know which are far bigger (in quantity)… but there are things that we do no know that we don't know which is way by far the biggest."

  17. But what about bright energy and bright matter which are invisible and undetectable by all known methods, this bright matter and energy are the polar opposites of dark matter and energy and cancel out the effects of both, therefore another explanation is needed, this time try finding a scientific explanation instead of invoking magical undetectable fictitious entities.

  18. Actually the quote is from Werner Erhard decades prior, Rumsfield just repeated it during a press conference without giving credit and everyone mistakenly attributes it to him.

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