To Infinity and Beyond - Professor Ian Morison

um this title obviously comes from Buzz Lightyear and he was slightly pompous I think or meant to be and it was meant to be something that was obviously absurd I'm not sure that it is absurd and I hope that by the end of this lecture you might agree as well well the subtitle for this lecture is the origin and evolution of the universe in 60 minutes which is fairly tough but one thing I would say I have over the past year or so given lectures which fill out quite a few of the things that I shall that I shall cover but not in the detail I have in the past so you can learn more about Einstein with the lecture entitled proving Einstein write more about the expansion of the universe and how Hubble found that out in Hubble's heritage about the Big Bang in the violent universe about dark matter and dark energy in the invisible universe and all about the cosmic micro background in the title the arthur globe creation so if you can look back at those you should be able to get some you know more details i've got rather more words in the PowerPoint that I normally do it actually makes a precis of the whole talk but if you want to I think the transcript was about $9,000 words and I hope that will give you quite a good feeling of what's going on well let's start the universe as a whole must be beholden to gravity because it's the only infinite range force that acts on neutral matter electrostatic forces tend to be short range because matter on the large scale is neutral and of course the first theory of gravity was Isaac Newton's and a lot of people say well that's obviously wrong in fact it only does fail under extreme conditions and the only case I think it fails in our solar system is to do with the precession of the major axis of the orbit of mercury it doesn't get quite right that problem was eventually solved by as you know Albert Einstein way back in 1905 in what perhaps we could call his annus mirabilis he produced two incredible papers the first one was about the photoelectric effect in sunsets is one of the foundations for quantum mechanics which ironically Einstein did not like at all and that was what he got his Nobel Prize for nothing to do with relativity and then his second paper and action was a supplementary paper as well was to do with what we call special relativity and a fundamental part of special relativity is that light travels through space at a constant speed you will know that but the important thing is that no material thing nor any information however it's carried can travel through space faster than the speed of light I've highlighted the word through there because it does not say you cannot travel faster than light you can if you're being carried by the expansion of space this happened very early on in the life of the universe as we shall see think of a current bun you take some dough you put some currants in it put it in the oven gas mark 4 for 20 minutes or something it comes out hopefully a bit bigger so those little currents will be further apart they have not moved through the dough they've been carried apart by the expansion of the dough and that's the idea you have to think of well in 1915 Einstein produced his theory of general relativity which is essentially a theory of gravity the theory is pretty complex it's couched in tensor calculus and even that wasn't in a level mathematics when I did it almost exactly 50 years ago I realized as I was coming down on the train this morning and so nice things to say about it there's a man that we should know about but perhaps don't very much called shame Wiseman he in fact he was born in Belarus oh he came to the UK he became a lecturer in chemistry at Massey University my own University in 1904 and in fact he invented the way of producing chemicals using bacteria in particularly acetone I think that made him very rich but then he became a Statesmen and he was the first president of Israel so he was really quite a man I think it was in 1922 he accompanied in Stein on a transit lecture a transatlantic voyage to New York I should say this is the Aquitania and not the Titanic which had gone down before which could well have been the boat that he was on I did try and research this a little bit okay now anyway at the end of that voyage this is what Chaim Weizmann said Einstein explained his theory to me every day I don't need to say and on my arrival I was fully convinced that he understood it I as a lovely a lovely quotation well thanks for laughing anyway now there's another nice story which i think is true rather than apocryphal and this is the best picture I could find of Einstein with Arthur Eddington and you may know certain if you go back to the Einstein lecture that Eddington led the expeditions to try and prove that Einstein was right by looking for the deflection of stars close to the Sun during a total eclipse about nineteen I think it was 18 a journalist came up to Arthur Eddington dr. Edison professor might have been there and said sir I believe you're one of only three people in the world apart from Einstein who understand his theory and Eddington did not give a reply after a bit the Johnson will that's a perfectly good question isn't it anything said well yes I'm just trying to think who the other two are so it's not the easiest of theories I'm Stein's theory predicts that mass will distort space-time around it and that gives the surrounding space what we call positively positive curvature which means that anything traveling through that space goes in curved lines to try and explain what it might be let me try and give you an analogy which I did give some years ago you have to imagine a very odd planet quite big the lower half is normal people live there but everything above the equator is covered with ice which is a particular sort of ice it has no friction the people on that planet are totally convinced that they're living on a flat surface they're members of the flat world Society and they cannot be shaken from that commission I know it's silly you have to accept that two explorers decide they will try and investigate what happens above the equator they get on two sledges ten kilometers apart and they basically fire them off simultaneously at the same speed so they'll travel northwards over the surface of this of this ice no friction remember now they will think that they would remain ten kilometers apart that's what would happen on a flat surface they will be therefore slightly upset when they crash at the North Pole now if they insist on believing that the surface of their planet is flat the only way they could explain that is to suggest that there was a force that they might call gravity has actually pulled them together you see that so gravity is a force that we make up to explain what happens in a curved space if we actually think it's not curved because we can't appreciate the fact that space is curved so maybe that helps a little bit and this is rather lovely John Wheeler great possesses to the last century and matter tells space how to curve space tells matter how to move well Einstein wanted to solve his equations for the universe that he saw what existed at that time a so-called static universe unchanging inside and this was the general consensus among astronomers in the early part of the last century now there's a fundamental problem with this supposing there were just two things sitting there like that and everything is just stationary what will gravity do it'll make the whole lot collapse down so he had to invoke a constant called lambda or sometimes the cosmological constant which was in effect an anti-gravity term which has the interesting effect that it's actually stronger the further things are apart as opposed gravity which gets weaker now if you have a force like that you can see that if you have two objects that are just the right distance apart the anti-gravity lambda force can exactly compensate for the gravity and the thing remains steady however this is a totally unstable system if they get very fractionally closer together gravity wins they'll fall together if they get slightly further apart anti-gravity the lambda term wins they were fly apart so it was an unstable universe and Einstein when he realized this called it the greatest blunder of his life well maybe he wasn't quite so wrong as he thought so it certainly wasn't that particular universe and as you heard I think in my last lecture in detail Edwin Hubble showed that the universe was expanding let's quickly look at how he did that first of all someone called Vesta slifer who doesn't really get the acknowledgment he really deserves he measured the speeds of approach or recession of galaxies by measuring the blue if they were coming towards us or the red if they were going away shift in their spectra you've all heard of the redshift it turns out that three nearby galaxies were coming towards us but the majority of them the remainder were receding from us so he had measured the speeds of approach or a session of quite a number of galaxies now at that time there was a real debate about whether the so-called white nebulae what we now call galaxies were beyond or within our own Milky Way galaxy Henri had to leave it gave the clue as to how to solve this problem she had observed a type of very bright star there called Cepheid variables after the star delta cepheus discovered by john good rick an englishman these stars increase in brightness quickly fall away more gently increase fall away so it's a very rhythmic oscillation of the star going in and out these are very very bright stars some of the brightest stars we have which means you can see them at great distances that's good she observed a whole range of them in what is called a small Magellanic Cloud which is down here we're here so they were all at about the same distance and she discovered that in fact the brighter ones were breathing more slowly which is not really surprising a bigger object he's likely to be brighter if you took a big Bell and the little Bell the big Bell would actually have a lower tone than the little Bell so the bigger stars are oscillating a little bit more slowly than the smaller stars and those that oscillate when the period of about 30 days are typically about 10,000 times brighter than our Sun and obviously this arrangement that's particularly useful 130 days the first major discovery that Edwin Hubble made was by observing our nearest giant galaxy the Andromeda galaxy he observed what he first thought was an n-type star here but then realized it was a variable star it was a Cepheid variable this was in the 6th of October 1923 and from that he was able to compute the distance of Andromeda and showed it was way outside our own Milky Way galaxy the universe became vastly bigger effectively on that day well he then measured the distances using that technique of all the galaxies that had been observed by West Oh Slifer and he made a plot here is the distance this is a very big distance and that's quite as big twice as big a big distance along that way that's a mega parsec which is a million parsecs which is three point two six million light-years it's a long way now he noticed that galaxies at about one mega parsec distance were going away from us at about five hundred kilometers per second whilst those that were two mega parsecs were going away at a thousand kilometers per second now you might say that's a bit of a guess really that that's a straight line but he then bit later on 1931 with his assistant human huh Merson they extended the Hubble plot to a much greater distance and I think you'll agree that that's not a bad straight line that tells us something totally significant it tells us that our universe is expanding and I've made this very simple universe perhaps to try and explain that we've just got three objects red green and blue they're each 10 miles apart we will let that quote universe expand by a factor of two in just one hour so at the end of that hour can you see we've got a distance of 20 miles and 20 miles everything is twice as big if you look at the green one from the red one in that hour it has gone 10 miles so it's average speed of recession is 10 miles an hour if you look at the blue one from the red one in that hour it will have gone 20 miles average speed of Accession 20 miles per hour and if I extend this to many many more you'd find that the more distant ones appear to be going away from us at a speed that is proportional to their distance and that's exactly what Hubble had observed in the galaxies and that told him and tells us that our universe is expanding that's exactly what I've said there and I just want to say something about the redshift of these distant galaxies they're being carried away from us by the expansion of space they're not moving through space but when we look at a very distant galaxy we're seeing it at some time in the past could be a very long time in the past and if we have an expanding universe at that time the universe would have been smaller as since then the universe has expanded so the wavelengths of the light being carried through it expand by the same ratio so they become red reddened and this is what we call the cosmological redshift so from this Hubble produced what we call Hubble's law the velocity of recession due to the expansion of space I've written there is proportional to the distance and related by Hubble's law which is in fact the velocity is equal to a constant which is Hubble's constant times R we put the zero there because it's actually the value of Hubble's constant now over time if the rate of expansion as we will see has changed then in fact Hubble's constant isn't really a constant it's something that's actually changing with time but H naught is the current value and remember I talked about a galaxy one mega parsec away traveling at about 500 kilometers per second so the value of H naught that Hubble got was 500 kilometers per second per megaparsec okay so now a bit more cosmology and we know now that the universe is expanding in fact prior to that knowledge Alexander and I have spelt that correctly I think Friedman solved Einstein's equations to produce an infinite set of models of expanding universes now I've tried at least in the PowerPoint to use a small you when it's universities in general and a big you when it's our universe I hope I've been consistent they're called the Big Bang models because they all start with what is termed a singularity and it is said that was a derogatory term given them by Fred Hoyle who opposed them as we shall see shortly in fact I think in his later life he said it wasn't really that it was just a name he made up it's a good name by the way there's a lovely book about Fred Hoyle just published by Cambridge University Press written by Simon mittens anyone seen it I was lucky I got a copy to review so it doesn't cost anything anyway it's a good book and I thoroughly recommend it to you it's a very very good book now in the Freedman models the universe is all begin in a point singularity and those that came to my lecture about the Big Bang know that I do not like singularities I say it is simply when the laws of physics of that particular Theory breaks down which is certainly true in Einstein's theory in fact I would say that means the standard Big Bang models could not in fact be correct which we shall find out is the case but for the moment just imagine that all the matter of the universe was concentrated at a very very small point the initial high rate of expansion Falls with time due to the neutral gravitation of all the matter in the universe just in the same way if I take a ball I throw a pardon up into the air the velocity speed going upwards slows with time that's just the gravity of the earth acting upon it and these are the models it depends upon how much matter is in the universe the density of matter as to what happens if there is enough matter in the universe the universe will expand to a maximum size and then collapse down to a point that we call the Big Crunch and of course there are an infinity of models in here like that like that like that like that and so on so that's an infinity of what I call closed universes they are ones which will eventually come back to a big crunch on the other side we have an infinite number of open universes where in fact the expansion carries on obviously faster and it will never fall back to a Big Crunch but there is one individual case between all of these and all of those which is called a critical universe sometimes called the flat universe as we shall see where it's just like the escape velocity of the earth given nothing else in space a rocket leaving the earth with escape velocity would leave the earth it would go slower and slower and slower and slower but never actually stop until it gets to infinite distance so that's the so-called critical universe it will expand forever at an ever slower rate the critical or as we shall see flat universe is the boundary between all the open universes and all the closed universes the universe is then said to have a critical density if the density is greater that means there's more mass we get the closer universities ending up with a Big Crunch the ratio of the actual density that's what the universe really is to the critical density is a factor it's called Omega if Omega is greater than 1 I were denser than critical we have closed universes and in fact in those universes space on the large scale is positively curved come back to that in a minute if Omega equals 1 we have the critical universe and they say and I don't like it the space is flat which almost implies it's 2-dimensional it doesn't what it means is in such space Euclidean geometry holes way if you have any triangle in any orientation in this Euclidean universe the angles inside will add up to 180 degrees and two laser beams starting off parallel will remain parallel forever and finally if Omega is less than 1 we have open universes and in these space is negatively curved and I will use this idea later on to try and show you why we believe in fact that space on the large scale is flat and that's just a two-dimensional analogy there's our flat universe omegas 1 triangles 180 degrees on a positively curved universe Omega graceland 1 these angles add up to more than 180 and on a negatively curved space like on a saddle the angles add up to less than 180 but we'll come back to that later on I do want to make that point now though now this is quite interesting if you assume a constant rate of expansion which is not true in any of those models but supposing you do then you can extrapolate backwards in time until the universe had no size its origin and that time or that age is called the Hubble age or the Hubble time both of those terms use and you get it simply by going one over the Hubble constant it's very simple well it takes a page to do it but don't worry about it all you need to know is it's 2 billion years if you take Hubble's value 500 kilometers per second per megaparsec expand out it comes to 2 billion years now in fact that is this this is now that's the value of Hubble's constant now H naught you backtrack in time and you get 1 over H naught which is that time now if you think about those Friedman models I've just shown you all of those began with a greater rate of expansion this is in fact the critical one so can you see that the Hubble age is bound to be bigger than the real age is that it's not obvious somebody say yes yes ok so in fact if it is the critical or flat universe it turns out that in fact the actual age is 2/3 of the Hubble age which is about 1.3 billion years and so that was the value they got basically around 1929 now that may worry you I hope it will worry you because we know that our oath and people beginning to know the age of the earth about 4.5 billion years and calculations significant made by Fred Hoyle and others on the evolution of stars for which these gentlemen launched have got the Nobel Prize basically showed that at least some stars had to be really greater than at least eight thousand years eight billion years so essentially the universe things in the universe cannot be older than the universe itself so obviously there was something wrong and theoreticians plenty of them said well could the Big Bang Theory's be wrong and as many of you will know in 1949 Fred Hoyle Thomas golden Hermann Bondi produced a rival theory of cosmology called the steady state theory or the theory of continuous creation now in this theory they extended what is called the cosmological principle so all cosmologies adhere to the cosmological principle which is what one would see on the large scale at a specific time will be the same everywhere in the universe so no matter where you are the universe if you all look at the same time relative to the origin it will look the same and that actually has been very nicely proven by the hubble space telescope it's made the Hubble ultra-deep field north in Ursa Major which is this picture here the Hubble Ultra Deep Field south somewhere in the southern hemisphere almost opposite in direction and essentially the universe in those very distant locations well away from each other look the same they extended that theory to basically produce what they call the perfect cosmological principle and all I've done is to add three more words it's the same everywhere in the universe for all time the universe would be unchanging on the large scale now they knew that the universe was bandung so that would mean that the galaxy's would gradually be moving further and further apart from each other but their nice idea was that in the space between the galaxies new matter in the form of hydrogen was being created and rather nicely you could never possibly detect that rate of creation so it's good when you can't test these but we'll see there was another way anyway that hydrogen would eventually form galaxies so the average density of the universe would remain constant even though the universe was expanding the rate of creation of new matter as I've said is too low to observe there is a bit of a problem though they said that you'd only make hydrogen and there's quite a bit of helium in the universe about 25% increasing now actually and essentially they thought that happened in stars and in explosions and really doesn't look as though you could actually make the amount of helium that we see but the really important thing was that the theory was in fact testable and it's actually a very easy thing to do this is the universe this is our Milky Way galaxy this is the space nearby and I can take a volume of space a hundred cubic mega parsecs or some big number which acclaims lots of galaxies and I can measure the density fair enough I know how many galaxies there are per cubic mega parsec I can now look right back to the origin or near the origin of the universe perhaps eight thousand million years and I can take the same volume of space and I can measure the density of the galaxies in that if it is steady state the number I measure nearby will be exactly the same as the number I measure far away far back in time because the universe is unchanging however if we have the Big Bang models the universe getting bigger with time then in fact I'll find more galaxy's per cubic mega parsec here than I will find there does that hopefully that's fairly logical so that's a test poor thing and in fact Martin rile previous astronomer royal at Cambridge set out to do this by observing radio sources now in those days the early sixties we can actually see more distant objects I think in the radio part of the spectrum than they could in the optical things have changed now we're equal II good but in those days radio was somewhat better so he built an array of antennas actor Cambridge to try and do this in fact that's Martin rile this is Francis Graham Smith who was the director of Jodrell Bank of many years I make most of his PowerPoint presentations for him actually that's my one of my roles in life these days anyway um it happened that royals results the first set showed a great excess of distant sources over nearby ones steady-state was rubbish now look if you read this book about Hoyle you find that he and Ryle didn't get on too well even before this happened now the trouble was Rathod steady-state useless but then the people actually in Australia said rile most of your radio sources aren't real and therefore your results aren't any good and you can imagine what Hoyle felt when you heard that and there are seriously worse in pretty enormous rouse I'm not sure like it's quite subtlest I'll try and explain it what went wrong with the Royal results could you imagine three stones dropped into a pond simultaneously can you imagine a bit of water splashing about where they are imagine those are radio sources but those impacts would cause ripples wouldn't they to run up out across the pond and there will be places where the ripples from all three or even more can you see there sometimes add up sometimes don't there'll be some places where there was a little bit of a bump of water just due to the combination of the ripples from the real from the real three stones you see that well it's not exactly that but that's the same sort of idea that the way they were doing things a point-source would have a pattern of ripples around it and occasionally these could add up to make you think there was a source where there wasn't one we call it confusion that's the word the word well they had another go and another go and finally on the third go they got it right but can you imagine Hoyle didn't believe a word of it the data still showed that radio sources were more closely packed in the early universe Hoyle was not convinced not long after though there was a final knockout blow to the steady state theory but even that in fact Hoyle didn't really agree with but let me explain what it was we need to go back in time a little bit to a rather wonderful physicist called George gum off and I was lucky enough as a first-year postgraduate to be taught by him for a short while and he was the first to point out that if the universe had been very hot at the beginning in the Big Bang then this should still be some radiation left over that would pervade the whole of the universe and the point was this if you put a thermometer in the middle of nowhere in the universe as far away from anything you could get it would not say absolute zero it would have a temperature because as the universe gets bigger that temperature will reduce but will not go to zero until infinite time and in fact he wasn't him but his two students worked out it might be about ten Kelvin we call the radiation left over from the Big Bang the cosmic microwave radiation it turns out and in the first 380,000 years of the life of our universe it was too hot for atoms to form because if you had a proton and electron a photon comes along kicks electron off and so it's what's called a plasma you have free electrons the matter and the radiation were interacting which means they actually have the same effective temperature and also because the light and radio waves for that matter being scattered off the electrons it is just like light being scattered off water droplets in a fog or in a cloud the universe was opaque finally about 380,000 years after the origin it was cool enough atoms to form and at that point no free electrons the universe became transparent and so that as far back in time as we can see we know at that time the temperature of the universe would have been about three thousand Kelvin we also know it would have had what's called a blackbody spectrum it's the same like the spectrum of the Sun which is because the light and the matter were in thermal equilibrium since then the universe has expanded by about a thousand times as a result the temperature should fall in fact by just the same ratio it should be about three Kelvin and that's the idea I've mentioned it earlier that as the universe expands so the radiation wavelength when it expands by just the same ratio this was the blackbody radiation 400 thousand just under years after the origin peaking in the yellow part of the spectrum the universe would rotate on a yellow orange 3000 Kelvin this is what you'd have now it doesn't peak in the visible it Peaks in the far infrared and the radio which is good for radio astronomers because it means that to study the very early universe you can't be an optical Astronomy can be a radius from excellent ok as we'll see so the CMB now pinks in the far infrared and the very short radio wave part of the spectrum and we now have one of these rather lovely serendipitous discoveries I know I've mentioned it before but many of you here might not have been to that lecture but very briefly it's this the telescope you see in the back there at Holmdel in new jersey owned by Bell Telephone labs was actually used in some of the first satellite radio transmissions television transmissions when it was completed its use for that it was given to two astronomers two radio astronomers Penzias and Wilson pendous have built a superb receiver and they put it on the back of the hall inside the little lab at the left there and started to test it out and they got a bit unhappy because it was producing more noise than it should have done if you put the sound coming out onto a loudspeaker it just sounds like white noise a hissing sound that sound was just a bit too strong it wasn't the receiver they tested that separately it didn't matter where they looked it was the same that implied had to be something in the horn antenna well there was something just close to here where it was warmest a pair of pigeons were roosting and pigeons are warm-blooded animals so they have a temperature room temperature effectively or outside temperature they radiate radio waves so they're very good they brought a have a heart pigeon trap and look I kid you not this this I picked up off the web two days ago have a heart and here we are you've a feral cat this is a raccoon trap they're all much they I did not find pigeons down there actually but I assume they do so that was a have a heart trap that trap by the way is now in the Air and Space Museum in Washington over two days as he said they captured the two pigeons what to do with them well Bell Telephone labs had a laboratory 40 miles away place called Whippany they put them on a little track that was going there for a daily little trip and arranged one of the technicians to release them which they did and of course they flew straight back so they shot them so they were shot so that was all right except that while they've been in there they had left the interior of the horn covered with what they said actually in their paper and science was a white dielectric substance guano or something they got rid of that it didn't really make any odds frankly well Wilson was traveling on a plane from Boston to New York or maybe New Jersey to be honest on that plane by chance he met someone that my colleague here and I know quite well called Bernie Burke he was a research fellow at Chandra Planck for some years and he asked Bernie Burke well Bernie Burke asked him you know what's the problem have you got any problems and he said yes we've got this noise we don't understand Bernie Burke knew that at Princeton someone called Richard Dickey was building all his students were building a whole antenna on the roof of the physics department because Richard Dickey had also realized that the universe would be full of radiation and that you could detect it using radio technology so that's what he was trying to do Bernie Burke told Wilson when you get back ring up Richard Dickey they rang him up while there his group Rich's group were having tea and Dickie put the phone down and said we've been scooped and the next day they went across to Homme dale and said yes you have discovered the Cosmic Microwave Background which of course they got the Nobel Prize I feel it's slightly sad that Richard Dickey didn't either but that's the way it goes sometimes now to be honest that was a measurement at one frequency to be totally sure it really had come from the Big Bang you really had to have that blackbody spectrum and it wasn't action until 1992 that a spacecraft called Kobe with a thing called fire asked the far-infrared absolute spectrophotometer was able to show that the power spectrum of the radiation left behind was perfect the error bars fit within the theoretical line and I think it's fair to say that since that date no one has disputed the fact that there was a hot Big Bang I think that's absolutely solid so to summarize that Penzias and Wilson discovered the CMB in 965 it was shown to have a blackbody curve and there was a big bang um we had Hubble's constant that started all the the steady state theory of well basically it turns out there are two types of Cepheid variables and the ones that Hubble was observing the Andromeda were in fact brighter than the ones that Henrietta Leavitt had observed so all the numbers were wrong gradually over time that value of Hubble's constant has improved we now believe is about 74 kilometers per second per megaparsec very quickly there used to be two groups one group reckon it was a hundred another group reckoned it was 50 and they would shout at each other at conferences and then at George will Bank using something called a double quasar and one or two others we came up with a completely independent way of calculating it and got about 68 it's been wonderful c2c since that time many years ago how the hundreds have come down to 70 in the 50s have come up to about 65 and that is because they now know what the right answer was but even if you take a value of Hubble's constant of 74 which is about plus or minus a teeny bit the age in the Friedman models is still only ten billion years and I think more modern computations of stellar evolution suspect that some stars are distinctly older than that so I still think that this is another reason why the standard Big Bang models cannot be correct the universe in them is not old enough so problems with the standard Big Bang Theory's the first one is that as far as one could measure and I'll actually show you how it's done a bit later the curvature of space in our universe is essentially very close to zero ie flat space now remember that was just one possibility in an infinite number of solutions why should it be that close by chance in fact that value of Omega which is one in that case would have had to have been in the range of that to that one second after the origin of the universe for it to be close to one now because any deviation from one actually gets bigger as the universe ages that is incredibly fine-tuning there's nothing in the standard Big Bang models to explain why that should be so the second is called the horizon problem now we are here and that CMB that the Holmdel telescope looked essentially 14 nearly thousand million years back in time and that duration that radiation is just reaching us and it measured the temperature 2.75 three I think you look in that direction that radiation is just reaching us you see exactly the same temperature but the point is that no radiation from there has had time to reach over there do you see that the universe is nolde enough so how on earth does that bit of the universe know the precise temperature of that bit do you see there's a problem there and I want to give you an analogy I'm on a British ship and that's that I think the Red Ensign all right now over the horizon I see another ship is black so it's obviously not a nice ship it's got some sails and it has a flag so I can't actually see the base of it to be honest I'm really just looking at the top part but I see it there over the horizon and because I'm an astronomer I go up the mast with my telescope and I look out at the ship and I can actually see it I've blown the flag up just so it's got a flag the Pacific flag now while I'm up there I happen to look in the opposite direction and I see another ship and I see it's got exactly the same flag now would you agree because of the curvature of the earth the people in that ship over there could not see that ship over there fair enough so how they got the same flag at some time in the past they must have been close enough to each other perhaps in the same harbor so someone could give them the same flag to fly that the theoretical term is they have had to have been in the past in what's called causal contact within a volume of space so that light could travel information could travel no faster than the speed of light to join them in effect together so they've got the same basic information can't travel fast in speed of light now how on earth therefore can that part of space know what that part of space is like well the idea was produced by a chap scientist called Alan guff for another problem I won't go into to do with magnetic motor tools I was awfully tough when I found this picture on the web and I've included because my wife is in the audience and I wanted to convince her that some people are probably somewhat more tile untidy than I am but there is Alan goth now his idea is this it's called inflation at some time in the past somewhere way back a little bit of space suddenly blew up it may have started as a quantum fluctuation out of effectively nothing but it blew up by a factor of around 10 to the power 6 T somewhere between 50 and 60 so eventually ended up as something about the size of a meter across it's called inflation and you don't get much better inflation than that and things by the way during that inflationary period were moving apart distinctly faster than the speed of light because it was a space expanding now that actually generated a vast amount of energy and we'll see what happened to that energy in a minute but the important thing is this if you expect took a balloon and blew it up by 10 to the power 6 T times would not the surface look flat so if you blow up our universe by that sort of amount what might have been initially positively curved becomes essentially flat so that forces the space in our universe to be flat but the other point is this that prior to the inflation everything that there was was close enough to be in thermal equilibrium so after it even though things have travel faster night things could all be at the same essential temperature we had a homogeneous universe which is why we see it now so inflation solves the flatness problem and also solves the horizon problem because all of the universe was in what's called causal contact before the inflationary period I talked quite a bit about the Big Bang in that lecture called the violent universe but very simply during that inflationary period a vast amount of energy in some sense was created half of it was gravitational potential energy which we'll call negative and the other half was positive and it's a bit like having a car on the top of a hill it has what's called potential energy if you push it down the hill it loses potential energy and gains kinetic energy the two are sort of equal and opposite ones positive ones negative and in fact the net energy would be zero so there was nothing the totality of everything in the universe if you could make it all fall back down together again the energy released by all the potential energy would exactly equal the energy that makes up all the matter so our universe is just a big sort of aberration from nothing and in fact that only happens in the case of a flat universe so that's another reason why the universe has to be pretty flat out of that sort of positive energy were created particles an almost equal number we believe of matter and antimatter particles but by Samuel asymmetry there was perhaps one part in eight billion an excess of matter over antimatter all the matter and the antimatter annihilated each other and that gave rise to all the photons that make up this Cosmic Microwave Background the normal matter particles that were left over mostly up and down quarks and electrons the quarks combine in groups of three to form an almost equal number of protons and neutrons but the neutrons by themselves are unstable with a half-life about 16 minutes so many of those neutrons turned into protons so the number of protons went up number of neutrons went down the only neutrons that remained were those that effectively captured to form helium nuclei and those were essentially the two major elements seventy-five percent hydrogen 25 percent helium that were created in the Big Bang as I've said it was so hot then the atoms couldn't form only after about 380,000 years did the universe cool sufficiently to allow the atoms to exist okay inflation predicts and observations which I'll show you shortly seem to require that space is flat if that is the case it's an easy calculation to work out the average density of matter in the universe it's about one hydrogen atom per cubic meter something like that it turns out that the normal matter that we can see stars etc ionized gas as well as things we can't see normal gas dust black holes whatever only makes up about 4% of the total mass energy content of the universe and as I talked about in that invisible universe lecture dark matter can help solve this problem and we have a vast amount of evidence now that dark matter must exist and one of them is this in the terms of planets go around the Sun the outer planets move more slowly that's called Keplerian motion and it was thought that the outer stars of a galaxy well out from the matter concentrated the center of a galaxy would be going round more slowly than the inner stars it turns out that's not the case if anything the stars near the edge of a galaxy are going round slightly faster certainly at the same sort of speed the only real way you can explain that is that the galaxy is embedded in a halo what's called dark matter whose gravitational effects obviously affect the motion of the stars and a great guy not well-liked by his colleagues called Fritz Ricky he observed a lovely cluster of galaxies called the Coma Cluster now if you think about it if you had maybe a thousand galaxies all sitting there doing nothing gravity will make them collapse down on the other hand if you made all those galaxies go very fast indeed they just fly apart the fact that that Coma Cluster still exists perhaps eight thousand million years after it was formed tells you something it tells you that the gravity that's trying to prevent them escaping is roughly comparable to the energy of their motion it's called the virial theorem from that if you measure the energy the motion of all the galaxies you can work out the mass of the cluster and it's several times more than what you can see so we believe that this is in fact the result of dark matter we don't know what it is yet there are lots of experiments going on to try and find it things call neutrally noes are quite likely a wimp is a weakly interacting massive particle that makes it very hard to detect and I said searches are actively taking place including at the bottom of the bull be mine in North Yorkshire where they have a lot of experiments so I can't tell you what it is and I've shown this before but I can show you precisely looks like but we still have a problem of all the mass energy required to make space flat we now think we've got four percent nor matter twenty three percent dark matter which is 27 percent if I can add up that leaves you 73 percent what can that be well we we say it might be dark energy and energy of the vacuum of space we have some evidence for it it turns out we can observe very bright objects called type 1a supernovae when they explode they're probably brighter than the whole of the galaxy that they're embedded in there the result in fact of a white dwarf being overloaded with mass so it actually collapses and undergoes a thermonuclear explosion and because the way this happens we suspect that all have the same peak brightness it makes some very good standard candles because if we see one a thousand times fainter let's say ten thousand times fainter than a nearby one same brightness the far object would be a hundred times further away so it's a way of measuring the distances to very very distant galaxies for example there's a supernova in this little faint galaxy here as seen by the Hubble Space Telescope and here a whole set the Hubble's done a wonderful job on this and I did mention this when I talked about the Hubble's heritage here this is before and this is after and someone's kindly put arrows on the sky to show us where the supernovae are you can see them here so we can now extend that Hubble plot out to vastly greater distances and there it is the supernova cosmology project has been doing that work and it's always been known because we do not expect the expansion of our universe to have been linear over all time and the Freedmen's it would be expanding more quickly in the past that plot would stop being linear when you go far enough back into time and it does these are not on that straight line and I can make it more obvious by making that horizontal line or so I line horizontal so I've just basically flipped that line here and made that go horizontal and here it fits pretty well down here it's way way but there's a fundamental problem in all those Freedman models the values should have been down here they should have been below the line not above and that tells us that now the rate of expansion of the universe is not decreasing with time as in those freedom models but increasing the time the rate of expansion is increasing we live in an accelerating universe in some sense now that could well be and at the moment all the evidence suggests that it is this cosmological constant term the lambda term in Einstein's equations that he thought was this greatest blunder that could do exactly what is currently observed so what do we actually know now let's just come right up in fact to about a month or two ago the density fluctuations the universe wasn't totally smooth when it first became transparent we can look back and see tiny fluctuations 100 or so microkelvin in the brightness the first really good observations were done with the boomerang spacecraft and basically they let it off at McMurdo Sound the American base in Antarctica and the winds take it all the way around in a circle and bring it back ten days later you know I've always had this worry about these people that sail around the world because really they go straight south whip round Antarctica the right way and come back up again I sort of feel you should go through the Suez and Panama canal's but anyway that's another point but basically the winds will take you around Antarctica I'm not trying what they do I just find it amusing anyway this is a map of those cosmic microwave fluctuations and you can see there's quite a lot of structure on a sort of a scale size this much which is about point eight of a degree now it turns out one can compute precisely what the sort of pattern should be and let me try and give you an example to show you what we think how this tells us what space is like imagine that the back of the room there was one of these patterned wallpapers you get an Indian restaurant you know repeating pattern okay the space between it and me was Schumer's flat light travels in straight lines I see precise to the angular scale of that pattern as was would you agree is exactly what it looks like supposing however the space is positively curved and I've got here coming out of an achromatic telescope I haven't got it back together going here is a very nice convex lens if I hold that up in fact I can actually see that things at the back of the room seem further apart can you see the scale is expanded because that's a convex lens that's what happens with positively curved space if I on the other hand put up a negative lens or concave lens we all look smaller and further away everything looks smaller so if we measure the scale of the fluctuations in this Cosmic Microwave Background we can tell whether it's what we expect smaller or greater which tells us what the curvature is and this is a simulation that was done those are the boomerang observations that's what you'd expect with positively curved space this is what you expect the flat that with negative and it looks pretty close and you'll see that's been even better in a minute or two this is the wonderful spacecraft called W map that has produced an all-sky map of these fluctuations and that's being analyzed in great detail and it gives you a plot now don't worry about this but basically this is the peak of the fluctuations is at point eight of degrees that's exactly what you'd expect with flat basse these Wiggles here tell you that inflation happened and the relative heights of these tell you how much dark and normal matters so there's an incredible information in this now this is all W map W map hasn't got great resolution so all these results are from ground-based instruments and the orange ones are from our own telescope up on Mount ID the Americans have the Very Large Array we have the very small array so that's done a great job I should then say that there's a planked spacecraft orbiting now it has got two receiver systems that we built at Jodrell Bank they're working all of them are working perfectly in fact it did actually show a little bit of data and that corresponds to this bit and basically we see the same things but with a factor of two or three greater resolution we will know that plot precisely in about a year or so maybe a year I've seen some of the data I'm not allowed to tell you what it's like okay yeah so we can take the data from the CMB observations with the latest values of Hubble constant about 74 we know what the universe is like now it is lumpy and bumpy it basically has voids and the galaxies are around it and all of that we get a very consistent model of the universe it's called the lambda-cdm lambda and cold dark matter the dark matter being relatively massive particles 4% nor matter 23% dark 73% dark energy aged about that the pressure produced by the dark energy is now making the expansion of the universe accelerate we've talked about that and this quite recent just a few months ago this is what w map tells us very quickly helium was present before star formation inflation happened there's no measurable deviation from that lambda-cdm model that looks okay space is flat within 1% and dark energy is within 14% of what you would expect if it's this lambda term in Einstein's equations all really fits rather well and what's happened is that the age of the universe started off expanding quickly gravity slowly but then this dark energy is making the expansion increase at an ever-faster rate but one final problem so I'm going to be covering this over why is the universe fit for life the fact that I'm talking to you there are a number of parameters which have to be precisely right or very close to allow us to exist very quickly n 3 spatial dimensions if n were 2 you could not have complex life if n were 4 forces would fall off as the inverse cube atoms couldn't form another one is the ratio of the amount of mass that's converted to energy when you fuse hydrogen if it were less than point zero zero six is actually point zero zero seven helium and the heavier elements wouldn't form we couldn't be here if it were greater than or point zero zero eight there'll be no hydrogen left we wouldn't have any water so basically that has to be quite right along with another a number of other things two possibilities one a creator designed our single universe so it could support life there's no way of showing that wasn't the case or as people like Lord Rhys would say there are myriads perhaps an infinity of universes all with different properties some of which very similar to our own would be suitable for life one idea has come out of that inflation Allan gas idea they call it eternal inflation in which once started universe's per Sporn indefinitely it could be our universe is infinite in size and beyond that there are another infinite number of other universes so perhaps Buzz Lightyear was right not wrong string theories you've heard of they arose out of attempts to produce a theory of everything there were five competing theories ten dimensions six curled up two forms of particles how they vibrate they call Springs strings how they vibrate basically determines how they actually act ed Witten he may have heard of he showed that all these five fears were in fact just different manifestations of a higher theory he called m-theory and that has 11 dimensions and there could be an infinite number of universes all existing together but without anyone knowing about them and here's a very very simple analogy for that I've got thrilled that all of it this is meant to be good bread I've got three slices of bread and on them can you imagine I put some atlantes now they can sort of walk around on each side on one side should we say and can you see they'd sort of think they were in a two-dimensional universe it's very good bread they could live for quite a while actually on here now that's all they know and they would probably not know about the ants that were on this universal that one however we because we can think and visualize in three dimensions not two special dimensions can see they're just three two matching universes in another higher dimension it could well be that our universe is just such a thing that there are myriad small universes could be very close to us but in another dimension and that's exactly what I say one point about that is does it sort of explain why gravity is very weak they say leaks into higher dimensions well if you believe that you'll believe anything but that's probably true now I want just in fact to quote myself because I'm quite pleased about this okay now whenever I quote from people I always put a picture down to have you notice that so I thought I better put a picture of me but I scaled it so that my brain was about the right size relative to Ed Witten's anyway now if you read in the Gresham brochure the final words of this talk about this talk were that our universe could just be one small part of a multiverse that extends beyond our imagination now you could say I was waxing a bit lyrical could I quite like writing these twenty word things but in fact there's more to it than that what I was trying to imply and I think it's a fair thing to say was that the totality of the cosmos which is everything and the laws that govern it might well be beyond the ability of our human minds to grafters that suddenly it's a reasonable statement that is what I really felt and it's certainly true of mine now that to be honest was my own thought I'd never read or heard this thing anywhere I was very pleased when in the summer law oh no to the big picture gate Lord Reis he in an interview with The Sunday Times said the following and let they wrote this some of the greatest mysteries may never be resolved because they're beyond human comprehension according laundries president President strong rule and they didn't put the bit about past Gresham rest of a strongly which is unfortunate anyway you get the idea and he says that the inherent intellectual limitations for humanity mean that we may never resolve questions such as the existence of parallel universes and the like so maybe my thought wasn't wrong now he obviously never read what I'd written because that wouldn't been published till later on but at least I have the same basic idea so what's enough of that so very quickly our universe began as a big bang this is a tree ring of universe the rings are far apart but they're getting closer together the expansion is being slowed by the gravity of the matter within the universe and then about four thousand million years ago dark energy in effect overcame gravity became the predominant force and since then can you see the rings getting further apart the universe is expanding at an ever-faster rate it's interesting we live at the only time ish in the history of the universe when the magnitude of the dark energy in the dark of dark so the magnitude of dark energy and dark matter are comparable and also when we can observe the CMB as the universe gets bigger that gets fainter and fainter and fainter and all of this has allowed us to learn everything I've told you in this lecture we can also postulate of a future runaway expansion in the past you wouldn't have known about dark energy because there wasn't enough of it to observe in the future you'll know almost nothing because you won't see very much now is about the best time in the life of the universe in which to study it we can still see the CMB sufficient space to allow the dark energy to manifest itself as the longest-lived stars come to the end of their lives the evidence that lies at the heart of our current understanding will disappeared and as the clusters of galaxies move ever farther apart carried by the expansion of space will be less and less for astronomers to see so it's a great time to be an astronomer and a wonderful time to have been your brush and professor of astronomy thank you very much

Channel: Gresham College

Views: 56,297

Rating: 4.7530866 out of 5

Keywords: Cosmology, Hubble, Astronomy, Cosmology Lecture, Astronomy Lecture, Space, Star, Stars, Universe, Galaxy, Big Bang, Multiverse, Science, NASA, Jodrell Bank, Space observation, Space Science, Ian Morison, Gresham College, Gresham, Gresham Professor, Gresham Professor of Astronomy, Professor of Astronomy, lecture, talk, astronomy talk, astronomy lecture, education, free education

Id: BgpPYm0_dec

Length: 67min 11sec (4031 seconds)

Published: Sat Aug 27 2011