The Search for the Theory of Everything - with John Gribbin

some of you may want to get up and leave when I tell you this is not about the theory of everything that's the subtitle it's about why we don't necessarily need to worry about a theory of everything because the combination or separate pieces of quantum theory and the general theory combined to tell us that something really fundamentally true and accurate about our understanding of science and the book is in two parts the first part is about stars and how we know the ages of stars and the second part is about the universe and how we know the age of the universe I can't cover all of that here so I'm going to very very quickly skip through some of the stars story and then concentrate on the universe story and so this is where we live talking about the universe and to put that in immediate perspective you can compare it with the size of the Sun and in round numbers about a hundred earths would stretch across the diameter of the Sun and as everybody knows volume goes as a cube so that means the size of the Sun in terms of volume is a million and a bit times the size of the earth and the Sun is a very ordinary boring star with nothing special about it except that it's our local neighborhood star I'm sure you know all that already but the story of how we know about stars in general and the ages of stars starts with the Sun and it starts with this which is spectrum of the Sun and the pretty rainbow colors and across the rainbow colors you get these dark stripes which are caused by atoms in the atmosphere of the Sun absorbing light coming out to us and these are distinctive you know fingerprints or barcodes or whatever you want to call them which tell us what Sun is made of so you can work out the composition of the Sun from this evidence and something that I think people may not appreciate is how recently we've started to know these things it was the end of the 1920s in much less than a hundred years ago that people started to be able to use this evidence to work out the composition of the Sun and even then as I explained in the book it took them a bit longer to get the the numbers exactly right the other thing that's important about Suns spectrum sunlight is that it follows very nearly what's called a blackbody curve which is the pattern of radiation from what's known as a perfect radiator and it may seem strange that a perfect radiator of energy is a blackbody but it gets the name because an object that is perfectly absorbing and absorbs all the electromagnetic radiation that falls on it if it's hot enough it will then radiate all the radiation out in this characteristic sweeping curve which is the blackbody curve and the peak in the curve tells you the temperature of what's doing the radiating in this case says 5000 K I think it's a little low for the Sun this diagram but what matters and comes into the story later on is that if you can measure this curve and you can measure where the peak is then you know the temperature of the radiation that's involved this tells us how hot surface of the Sun is and you can even use it to work out how hot the temperature the surface of other stars are and if you know how hot stars are and you know their masses which is easy for the Sun because it's worked out from the way the planets orbit around it and it turns out to be quite easy for some stars because they're in binary pairs and the gravitational influence of one star on the other tells you how fast they're going around and you can work out the message from that then you can put all that together and you can work out how hot they are inside now this is something that was again only done in the 1920s ish sort of time and just at that time people were starting to develop an understanding of how atoms and nuclei interact and it was appreciated that the only way stars could be kept hot was by nuclear fusion essentially by sticking hydrogen nuclei together to make helium and basic laws of physics pre quantum physics said that the temperature in the middle of a star like the Sun which is about 15 million degrees was not enough to allow these things to stick together what happens is you have hydrogen nuclei protons both positively charged they charge towards one another the electric repulsion pushes them apart before they can actually collide and fuse to make something else and what happened was that as quantum physics was developed it was appreciated that there is a purely quantum phenomenon which allows this fusion to happen at the temperature at the heart of the Sun and it's to do with Heisenberg's uncertainty principle and the idea of particles being not pure particles but also waves and one way to think about this is that instead of your two little hard particles charging towards each other and not quite touching they're actually sort of waves and that once they get that close they can hug each other okay but the important thing is that it's purely quantum physics that allows this to happen and I won't bother going into great details about this but this is called the proton-proton chain it's one way that you can stick hydrogen nuclei together to make helium and there's another way which is important in stars that are a bit bigger than the Sun which is called the carbon cycle or carbon nitrogen cycle and it goes round around in a loop and if you give you a couple of minutes to study the loop you'll see wherever you start you go round the loop and what's happened in effect is you've taken four protons for hydrogen ucae and turn them into one helium nucleus and then you got back to where you started and so it keeps going round and round all the time but the really really important single thing to take away from all this is that this only happens because of quantum effects because of tunneling as it's called now there's something else that secured your quantum effects and that comes into the age of the stars and that's the process of radioactive decay which I'm sure everyone's heard about the dear of half-life if you've got a sample of a radioactive material in a certain amount of time half of it will decay into something else and then in the next interval the same size another half which 1/4 of the original will decay and so on and some things decay in fraction of a second some take thousands of years some take millions of years and some of the ones that take millions of years to decay are seen in some very old stars and because you can measure the proportions of the different things that it decays into you can work out how long the decay has been going on and this is what tells us is the end of my brief introduction to stars this is the end of part 1 of my book the oldest star that we know of the best oldest star has an age of thirteen point two billion years there are other stars with similar sorts of ages and much more uncertainty in the measurements cause it's ugly quite difficult to measure the abundance of uranium and thorium and things like that in a star that hundreds of light-years away can be done using spectroscopy back to the beginning but the really solid time that is the thirteen point two billion years so to keep that one in particular in your head while I tell you about the age of the universe okay well our home in space and there our local neighborhood I showed you the Sun and this is a galaxy very much like our Milky Way as it would look from outside and this is typical of the components of the universe there are hundreds of billions of galaxies like this scattered across space and it's the way these galaxies behave and how they seem to be related to one another and how they are separating from one another I don't need to tell you the universe is expanding I'm sure I'm not giving too much away is what tells us the age but this is this is the sort of thing this is the smallest thing that cosmologists are interested in okay and I was very nearly a cosmologists fact I was advised not to be I when I was an undergraduate I had the opportunity to meet Hermann Bondi who is one of the progenitors of the steady state theory of cosmology and I was wondering what to do after I finished my degree and I went to see him and I said I'm really interested in cosmology professor Bondi you know how do I get into it and he advised me that I should do something sensible first so I did I never did get to be a cosmology so I'm never sure if that was good advice or not I've done I've done okay but cosmology got much more exciting a few years after he told me that anyway and this is the top page on and the dark line through there is sort of dust and stuff and I wouldn't tell you this the Sun is sort of 2/3 of the way out towards the edge of a galaxy like that in a particularly unspectacular ordinary region and in the plane where you see that dust that's wearing relatively interesting things happen because that is largely made of they breed from old styles that have run through their life cycles and exploded and spewed out material into space and then that has made the stand new stars and planets and at least on one planet people and that is we all know we're all made of Stardust except for the odd bit of hydrogen in your body so how do we know about galaxies and what they're doing and so on we know the distances to galaxies because they contain these stars which are very in a very regular fashion which are called Cepheid variables and they have different periods to get between the peaks in the periodicity depending on how bright they are and this enables you to work out their distances again this is something that wasn't known about until in this case just over a hundred years ago I think it was about 1912 that the Henrietta Swan is pictured here she discovered she feeds in all more or less the same distance from us which is the key it's no good knowing that their brightness is related to their period if you don't know how far away they are two sort of calibrate things and start things off and the Milky Way galaxy that I showed you has some companions around it and these companions the two biggest ones are called the small and large Magellanic Clouds because Mandela and spotted them when he was sailing south of the Equator and no European had seen them before the few people who had seen them before but they didn't count as far as maining was concerned and they're so far away from us that for all practical purposes all the stars in them are at the same distance so even from one side of the cloud of stars to the other is a small fraction of the total distance so Henrietta Swan noticed while she was doing a very boring cataloging job of sort of counting stars and measuring their brightness and looking for periods and so on she realized that these stars were all essentially at the same distance and then she spotted that the brightest cepheid's had a different periodicity from the dimmer cepheid's and this is actually her data prettied up it's a modern plot but these are actually her numbers so you can see that the how many days of star of a particular brightness paid for its oscillation up and down and so then all you have to do you can find the feed is to measure its period and then that tells you how bright it really is and then you measure its actual brightness seen from Earth or its dimness if you want to think of it that way and that tells you how far away it is if you've got a 100 watt light all you know the end of the street you could measure the output reaching your your photo multiplier and work out the length of the street so it's a very simple technique in principle it's made much harder by doing things like there being dust in space so some of the light might get blocked out by dust and that gives you a false reading and so you need more and more and more of these things to try and get accurate measurements and that's one of the reasons why it took a long time to pin down crucial distances to galaxies and and things like that and this has been superseded and bored to date by a satellite which operated a few years ago called Hipparchus which measured millions of stars and calibrated this relationship very very accurately and really pinned down what we know about the relationship between the period and luminosity pacific so you could measure distances but this is the first step so everything else measuring out across the universe depends on knowing this okay there's no other way of getting out from our galaxy to other galaxies reliably to set things off so you have kind of like an inverted pyramid you know you look at modern measurements of things you know and they're measuring all kinds of clever stuff and supernovae and things like that I'm sure you've heard of but that all depends on calibrating things using using this stuff so thank thanks to Henrietta Swan that we know what's going on so people didn't know that galaxies which are called nebulae at first didn't know for sure that they were something outside our galaxy that they were other galaxies like arrow until the late 1920s there was been a debate about it they've been speculation but there was no proof until guy called Edwin Hubble took this photograph of a relatively near neighbor the Andromeda galaxy which was called the Andromeda nebula in those days and it's a negative because astronomers in the days when you worked with with actual photographic plates big glass plates preferred black on white because it's easier to pick out individual stars in that way and he got very excited when he saw this and that wrote up there initially put in because he's already seen a nova in for nova a bright star that flares up and then he took a picture a few days later and it was a different brightness and then it came back again so crossed out the end remote VAR exclamation mark variable so that was I think it's October probably stood up there October 1923 and over the course of the winter he measured the variations in brightness of this star he discovered it was a Cepheid he knew its periods because he had measured it he knew its brightness because Henrietta Swan had worked out what brightness assited with that period must have so he knew the distance to the whole Andromeda nebula which turned out to be a galaxy beyond the Milky Way another galaxy in its own right just as big in fact slightly bigger than ours hundreds of billions of stars forming what became known as an island in space so that was the first stepping stone out into space beyond the Milky Way and as I say depending entirely on the Cepheid measurement now when Hubble measured this time in the mid 1920s there'd been some measurements made by a guy called Vesto Slipher and he measured nebulae not knowing what they were but he measured the overall light from them and he discovered that they have typically that the light is shifted towards the red end of the spectrum you can tell this remember back to the beginning the spectral lines that tell you what the sun's made of their precise wavelengths and he found that most of the nebulae he could measure which was thousand twenty sort of things like that with the telescope he had they were shifted towards the red couple was shifted towards the blue in particular Andromeda and a simple explanation of this was that it's a Doppler effect caused by things moving through space so the Andromeda nebula moving towards us most of the others moving away from us it's not a dot perfect I'll tell you about that later on there was already this idea that most nebulae seemed to be moving away from us most that he could measure with the telescope at his disposal and Hubble was very interested in using this as a tool to work out distances because there was a hint that fainter nebulae had a bigger redshift and fainter ones guessing meant their further away the logical guess so Hubble wanted to work out a way to measure distances he didn't care about the redshifts and velocities or any of that stuff he just wanted to know how far away galaxies were and measured the universes as he would have put it so to do that you need somebody to help him and he needed the best telescope available and luckily he had that he was working with a 100-inch telescope which was the best one available at the time but it was too much work for one man so he got this guy to come in and help him to measure the redshifts and while he measured the redshifts how will himself measured the distances using initially cepheid's and then calibrating other things like using cepheid's he could work out that certain other things in galaxies were all roughly the same brightness and some of those things were brighter than cepheid's so he could apply them to galaxies further away where you couldn't see cepheid's and it's a bit rough and ready you know but it worked and he began to measure distances put them together with humans redshifts and by the end of the 1920s they had enough evidence also although Hubble was a great self publicist and he and he liked to take the credit for everything he didn't bother mentioning that he used in his first publications on what became known as the redshift distance relation a lot of slippers work he just didn't bother acknowledging Slipher but putting summer slippers work together with his work and who muslins work he had this relationship between what he called velocity and distance and it's you know it's an optimistic kind of straight line through some fairly dodgy data but it does go up at one end and down at the other which is about all you could say in those days so this led to the whole idea that the universe was expanding and popularized the idea that galaxies are moving apart from one another but he'd been preempted in two ways first of all in the beginning of the 1920s russian guy called alexander Friedman had been playing with the occur the general theory of relativity and he had found that the descriptions of the equations described a variety of possible universes they allowed for the possibility that space itself was expanding or contracting or going up and down or coming down and up and he published this as a really a mathematical curiosity he wasn't seriously suggesting it applied to the real universe that we live in but he was the first person really to use the general theory in the way that cosmologists then did later on he died young so so he wasn't able to develop the idea the the official story is he died typhoid in an outbreak in I don't know early 1920s guy called George a moth who we meet later who was one of his students always said that he died because he gone on a high-altitude balloon flight for meteorological observations and caught a chill and died as a result of that which is a and in a sense a more romantic story but George Gamal was always entertaining but almost always unreliable so believed whichever version you like but partly because Friedman wasn't on the scene somebody else came along is for Hubble and Humason had published their results and using slivers data in particular this guy George Lamech had solved the same equations that Friedman had solved the entirely independently he didn't know about Friedman's work which had been published in Russian journals and he also found this family of relationships about expanding and contracting universes and so on but the crucial difference is that the mature said that this could explain what our actual universe is like because there is a relationship thanks between redshift and distance which says that galaxies further apart are moving away from us faster and that fitted one of the possible solutions to Einstein's equations so he thought this out he had the redshift distance law that I just showed you that Hubble and Humason had got essentially exactly the same law though he had slightly less data to work on and he published it all before they published any of their stuff but he made one crucial mistake he's Belgian and he published it now that's that not entirely understood and he published it in a French language Belgian Journal which nobody read or no cosmologists read anyway so a year or two later Hubble and Humason come along and humor sends a nice quiet self-effacing guy who gets on with the work but Hubble goes around saying I am the great Hubble and I've discovered this and the net got a bit miffed about it and complained in particular to Arthur Eddington who's the the top British astronomer at the time and famously one of the few people who was alleged to understand Einstein's theory of oh really there were quite a few and Eddington then got the paper published in English and it was generally acknowledged in the trade that Lamech er deserves at least equal credit but he still doesn't really get equal credit except in my book and and he also I mean as you can see from the picture interesting that he was a priest as Roman Catholic priest as well as being a cosmologists so what he did was to think in terms of the physics of what was going on and what this implied for the universe in a real physical sense as I say Hubble didn't care he never said what the redshift implied whether it was a Doppler effect whatever it was but he just wanted to measure distances it was Lamech who said well if you take this at face value what's happening is that the space between galaxies is stretchy space is expanding it's not because things are moving through space and then if you imagine going back winding the movie backwards what you say is that long ago everything must have been in one place which he called the prime primer atom which is a bit sloppy because it should have been primal nucleus but what he realized and to show you how empty spaces was that if you took everything that could be seen in those days all the galaxies as far as the best telescopes could see and you wound the stuff back to the earliest possible time but there would be a time when everything was the density of an atomic nucleus of an atom and would occupy a volume not much bigger than the Sun certainly no not as big as the solar system now that gives you an idea of the emptiness of space and indeed the emptiness of atoms because nucleus is a tiny part of an atom so this was at the time when people were developing ideas about radioactivity nuclear fission and so on working towards what became the atomic bomb and all that sort of stuff and so he had this sort of idea that the VIS primal nucleus which would be in some sense like a radioactive atom and would spontaneously decay split fall apart and the bits would fly apart because space was expanding and would gradually turn into stars and galaxies and all that stuff which wasn't a completely bonkers idea by any means and in the beginning of the 1930s and he developed this idea and it culminated in a book that was published in 1946 which was just at the time when it was ready to be picked up by other people and the story starts to come a bit more up to date so now the story splits in two and I have to tell you one bit and then backtrack and go up the other branch to tell you what's going on with observation and theory and this of course is what always happens in astronomy and in other aspects of science you do observations or experiments and you develop better hypotheses and theories and then that tells you another experiment to do or another observation to make and you know it goes along like that it's gradually builds up and up and up until you have a nice picture of something so observation the person who took up that the threads of what people are Hubble have been doing and tried to get rid of all the uncertainties in this redshift distance relation and measure the redshifts and measure the distances and use various kinds of these vertical proxy indicators like the brightest cluster in a galaxy and then the brightest galaxies in a group of galaxies and all kinds of things to get further and further out measure more and more redshift and really pin down this law which is still known as Hubble's law and it ought to be at the very least the Hubble the match law but this this guy Allan Sandage gave his life it's working life to doing this right through the 1950s and into the 1960s and he used the best telescope that there was before the hubble space telescope which was a 200-inch telescope in california 200 inch diameter mirror and and this was pushing the technology which gradually improved because you don't just look at photographs you hang things on the end of the telescope that that measure light in other ways and so he was able slowly slowly to pin down the actual value of the slope in this graph and it's the value of that slope that I showed you that tells you how long it is since there was the primal atom or whatever it was that was there at the beginning by winding backwards so he did an enormous amount of work and he pretty much got it right but there was always a lot of uncertainty in his work so he could tell you that the what's known as the Hubble constant which is that the the slope in effect of that graph was between 60 and 70 okay that that's the sort of area between 60 and 75 maybe which is phenomenal you know that we were even able to do that I mean that people are 100 200 years ago would never have imagined that and the way it works is that is telling you how fast the universe is expanding so the smaller that number is below longer the time since the beginning what we going to be called the Big Bang you know about this time so if the universe is expanding very quickly then obviously it hasn't taken very long to get to where it is now if it's spending very slowly it's taken much longer and that is important because as the other half of my whole story concerns stars even by the 1950s people were able to measure the ages of stars reasonably accurately not as accurately as we came today and the number that you got out of Hubble's law Lamech was law it should be called was telling you at that time that the universe was younger than the Stars which is obviously nonsense okay crucially rubbish so while Sandage was making measurements which gradually brought the value down which made the presumed age of the universe longer there was room still for a big debate about whether there ever had been a beginning whether there had been a primal Adam and that's where Hermann Bondi who I mentioned and Fred Hoyle and other people came along and said well maybe there hadn't been a beginning maybe the universe had always been expanding and always looked much the same and instead of one law that had expanded that as galaxies moved apart new galaxies appeared in the gaps and new galaxies would appear because occasionally an atom of hydrogen work whether actually a neutron which then decays into a proton and electron then becomes a net of hydrogen but essentially new atoms of hydrogen would appear in the gaps between galaxies and as Hoyle always used to say this is no more or less unlikely than all the hydrogen appearing in one go in a Big Bang which is where the name came from his turn and it's quite right as long as stars appeared to be older than the universe this is a powerful argument that what's called the steady-state model could be a viable alternative to what thanks to Hoyle became known as the Big Bang but that was ruled out because of what happened later on and one of the things that happened later on was this a Hubble telescope named after Hubble himself and it was named after him because the what was called the key project of the Hubble telescope was to measure distances to galaxies and register using cepheid's and give a definitive once-and-for-all answer to the question of how rapidly the universe is expanding how big or how small Hubble's constant is and therefore how old the universe is so the reason why the earlier studies are given the value that was too big related to the kinds of problems I mentioned when I talked about her near to Swan the bust in between the stars both problems calibrating this if it's right here in our own Milky Way and there's a problem because two kinds of stars which are very similar and they're they're called cepheid's and our Lyra variables and ones they've each got a relationship between brightness and period but they're slightly different and by bad luck some of the ones that have been studied by the earlier people had been obscured by dust in just such a way that they look like the other kind and then when you looked at distant galaxies you weren't looking through that dust and so you got the wrong answer so they're both kinds of problems you know which which persisted and they're the things that Sandage more than anybody else gradually eliminated one by one and found all all the problems and so on so this this telescope was a culmination of that traditional method of measuring the Hubble constant the Mattress pro con stantly age of the universe and so on and to give you a feel I was in any excuse to show these pictures you know a Hubble picture most of those things there are galaxies roughly comparable to our Milky Way some bigger some smaller and so on and this and this absolutely let that's sort of patch of sky it looks fairly crowded that's much more crowded every single fuzzy blob on that picture is a galaxy even more amazing it's called the Hubble Deep Field and it was found by choosing a part of the sky which looks completely black where with ordinary telescopes you can see nothing at all no galaxies no stars no nothing they pointed the Hubble telescope at it for a long time hour after hour after hour and what you can do then this great thing about technology is is if you look with your unaided eye you go out in the dark and you look at the sky after a few minutes your eye adapts and you see everything you're ever going to see and you can sit there all night and you'll never see any difference you'll see stars going and moving across the skies with the earth rotate but apart from that you won't see anything that you couldn't see in the first half hour say because the eye is saturated but if you've got photographic plates or today electronic charge coupled devices things like that you can keep looking at the same place and the individual photons come in and each one is recording and it builds up and builds up and builds up so the longer you look the fainter the objects that you can see so this reason the sky is particularly dark away from any bright objects it's also small the area that's covered by the Hubble the field this is only part of it sort of square bit is the same size as if you had a drinking straw and ordinary drinking straw two meters long and you held it up to your eye and you looked at the sky and that's what you see if you had eyes like see see these the universe is full of galaxies and some of them are a very long way away and in that sense the light from them is very old but in another sense those galaxies are very young because we see them by light which left them of billions of years ago so we learn a lot about the universe not just its age from the Hubble telescope and what we get from it is the modern version of Hubble's law I have to use that word heated and and this is this is now giving you a number 68 kilometers per second per megaparsec and it says kilometers per second makes people think it's a velocity it's not it's got the units of velocity but it's the way space is expanding and what it means is that an object that is 68 that is one mega parsec away which is just over three million light-years is receiving because space is expanding 68 kilometers a second as if it's moving through space but what I love about this is this bit up here if I can press the right button whoops no I can't I'm useless okay this patch which looks odd called the Virgo cluster the Burgo cluster is a large cluster of galaxies a lot of galaxies that are held together by gravity like a swarm of bees it's the usual analogy but they're moving around relative to each other so some are moving towards us and some are moving away from us and the whole cluster is moving because the universe is expanding in what's sometimes called the Hubble flow so that apparent scattering there that looks like errors is a measure of how the Doppler effect is influencing the cosmological effect so you see that there is a lot of doctor effect as well as cosmological effect and that highlights that the redshift is not a Doppler effect so this is a good number this 68 is the culmination it's it's the number that we get from the Hubble telescope the key project and on its own would justify the existence of the Hubble telescope and all the pretty pictures and other things are just a bonus in the eyes of the people who designed it so that's as far as conventional observations can take us so what did what about the theory what was the beginning like what was the Big Bang this is what the match is saying in the mid-1940s that you go back and back in time you get to a beginning and the beginning was some kind of very hot dense state and it was team of American searches who pictured here and if you can't see the names on there there's Robert Herman on the left and well falfa on the right and George gamma four I mentioned in the middle gamma bind then was it was was in the States and the other two guys were his PhD students and he was very interested in the ideas that the Metra promoted and they were interested in what had come out of the beginning of the universe and gamma wanted to make all the elements out of hydrogen by sticking things together to make helium and then sticking helium nuclei to make carbon and so on up the chain and he set these guys the task of working out what conditions were like and they worked out but in order to make anything at all fairly obviously it had to be hot in the center of the Sun has to be hot enough to make - fuse to make helium so they calculated that there must have been as Hoyle put it a Big Bang in which the universe the early universe was very hot and very dense and they put some numbers in and they worked out that the temperature must have been a few degrees absolute a few K about minus 270 on the Celsius scale yam off didn't do this he was the supervisor but he was loved the idea and he promoted it very vigorously but he didn't he didn't think of it and you often see accounts which say that he invented it and he did the calculations he didn't he was absolutely dreadful at arithmetic and whenever he did do the calculation he got it wrong so these guys deserve all the credit alfalfa and Herman and and this is gamma off who got all the credit it was actually a fascinating person who did lots of stuff including stars and cosmology and he contributed to cracking the genetic code and all kinds of things but he deserves the credit for promoting the idea but he didn't promote it vigorously enough because it was forgotten and after the early 1950s hardly anybody remembered the idea except Gamal who would occasion these are when people hear and tell about it and Alpher and Herrmann went off to do other work and so they didn't promote it either and nobody remembered it nobody's significant remembered it until the mid 1960s and then these guys Arno Penzias and Robert Wilson they discovered using the telescope you see behind them a weak hiss of radio noise coming from all directions in space became known as the cosmic microwave background radiation because it's at microwave frequencies and I should say they were much younger than this picture was taken later when they got some award or other they went back to have it taken at the telescope they didn't have a clue what they'd found famously they thought there's a fault with a telescope they cleaned it out their king pigeon droppings out of it they covered all the rivets with aluminium foils and said it would be smooth they kept finding this signal coming from all directions in space they didn't know what it was but just down the road at Princeton University there was a team who also didn't know about the work of alpha and Hermann and they had independently come up with exactly the same idea and they were predicting that the universe should have a background with a temperature of a few degrees K and long story about the two teams eventually got together and found that that was exactly what had been being measured so this was the moment really when the Big Bang Theory was taught came in from the cold if you like you know mid-1960s people that found the background radiation that had actually been predicted you know nearly 20 years earlier although it had been forgotten so what you find is you hope is a blackbody curve remember the radiation from the Sun the blackbody now that's what the theory says you ought to get if the universe is producing this hiss of radiation which is a blackbody radiation which is what it ought to be if alpha and Hermann and all the other people are correct so remember that's a typical that's a good plot in astronomy in those days you know this this is this is excellent you know and this much scatter you know you think at and wouldn't worry about that you know this is obviously a really decent straight line okay so it order to follow up as a technology improved a satellite was put up the end of the 1980s it's called Kobe Cosmic Microwave Background Explorer and Kobe looked at the sky from above the Earth's atmosphere and it measured the radiation and it found that and in case you can't see it but little blobs on there a 1% error bars the curve is a perfect black body and if you read the small print it says this is nine minutes of data so you put a satellite up and in nine minutes you have measured the temperature of the universe to better precision than ever before and you've proved that it is indeed blackbody radiation and people got Nobel Prizes for that hardly surprisingly people got very excited and say oh we need better satellites now so NASA put this one up it's called W map and a little bit later the European Space Agency but this one up NASA's was quicker not quite so accurate Lisa took a bit longer and measured even more accurately so there's really very little difference between them but Planck is slightly more precise so it's Planck data that I shall mention from now on and Planck could measure not just the overall average temperature of the sky those Coby ones 1% errors this is an actual map of the temperature differences from place to place on the sky and it's the whole sky you imagine you see a map of the earth sometimes spread out to make this kind of oval pattern and that's the sphere of the earth unwrapped well this is the same thing on the sky round from the inside unwrapped and laid out so that's the whole sky and the temperature differences are color-coded arbitrarily and just to make them stand out but the important thing is that the temperature difference is that Planck can measure are as small as a millionth of a degree so you got temperature which is an average 2.7 degrees on the absolute scale and you're measuring differences from place to place of a millionth of a degree and this pattern tells you how the temperature of the universe varied from place to place at a time when the radiation was released and that was roughly I explain why in the book I haven't got time now roughly 300,000 years after what we call the Big Bang and it was at that time that the universe cooled to about the temperature of the surface of the Sun today and that's the point this is why it's the surface of Sun the same reason at that point nuclei of atoms things like protons can join together with electrons and make electrically neutral atoms once the universe is electrically neutral the radiation can stream along without being affected but just before it was released it was interacting with the matter so this is also a map of the distribution of matter across the universe when it was 300,000 years old and everywhere was the temperature of the surface of the Sun today now I would need another hour to explain exactly why but if you compare the pattern of the distribution of matter then and the pattern now by looking at the way galaxies millions and millions of galaxies are spread across the universe you can see big patterns and you can work out how long it's taken to get from there to here essentially you start with a small thing and gravity pulls things together and the longer it takes the bigger things get but the important thing is that this gives you a completely separate way nothing to do with Cepheid variables or the Hubble telescope or anything like that of measuring the Hubble parameter double constant whatever you want to call it and thereby working out the age of the universe ok so this is how good the observations are and this is what's called a power spectrum and these Wiggles this is a temperature fluctuations and this is the size of the different patches of the sky that you look at so this is actually telling you how different size how how common different sized regions are across the sky and again you know they're down here there's a bit of uncertainty but you can hardly see the uncertainty in the measurements compared with the theoretical line so this is how well we understand the universe today and the theoretical line in this case comes from what's called the standard art model again whole whole other talk about that but that is something that you've probably heard about which involves three things it involves the the kind of matter that we are made of atoms and so on the kind of thing stars and galaxies are made of sometimes called baryonic matter it involves something else called dark matter which we know is there because we can see the way galaxies move that there's something holding them together by gravity and holding clusters of galaxies together that's called dark matter and then there's the other thing which is being in the news over the past few years which is dark energy which is a kind of springiness of space which is pushing the universe to expand faster and because of Einstein's famous equation e equals MC squared dark energy is also mass and affects the way things like clusters of galaxies develop in the expanding universe and the shorthand term for the dark energy is lambda is like the Greek letter lambda so this standard model is called lambda CDM lambda cold dark matter and everyday matter being taken for granted and put our place in the universe in another perspective very roughly unquote these figures exactly the amount of baryonic matter what we're made of in the universe is about 4% of the total density the amount of dark matter is about twenty-four twenty-five percent so we're insignificant compared even with dark matter and the amount of dark energy is about seventeen seventy two percent so most of the mass of the universe is actually this mysterious dark energy which is a huge project now going on to try and understand it and find out what it is and how it's affecting the expansion of the universe and there are other huge projects that have been going on for some time to try and find dark matter and looking for it in interesting places like the bottom of gold mines and under the mountains between Switzerland and Italy and so on but they're not what I'm particularly concerned about here what I'm concerned about is the age of the universe so this is the bottom line of what comes out of the observations with satellites and it is really really really good you know look look at how tiny this is the thirteen point seven nine nine plus avoids point zero to the uncertainty is in this bit okay it's less than two percent okay we know the age of the universe in the sense of being the time since the Big Bang to an accuracy at better than two percent you imagine what somebody like Hubble or Sandage even would have thought of that I mean that's one of the most profound and significant and amazing things in the whole of science and it deserves even more publicity than it gets but even better we've used quantum physics to tell us how old stars are we've used general theory of relativity in essence to tell us of all the universes and it turns out that the universe is just a little bit older than the stars so it's quite obvious that the stars formed after the universe after the Big Bang and that tells us that whether or not we've got a theory of everything which combines quantum physics and relativity theory we know that they're both telling us something accurate and true and profound about the whole scientific enterprise you know we're doing something right or these numbers wouldn't agree so that is really hugely hugely important you know in to in terms of of any understanding of what we're doing and what science is about and I get I used to get letters in green ink but now I get emails in block capitals and people say are you know Einstein must be wrong because you know and they sort of pull out one bit of Einstein and come up with some other theory and those kinds of people do not understand you can't do that with science you can't pick and choose you know it's all or nothing yeah there might be a theory somebody might develop which will be better than the general theory but it will be better in the same sense that the general theory is better than Newton's theory it will tell us everything that the general theory does because we know the general theory is right and it will tell us something new as well it may tell us something about you know what happens in the far reaches of the universe it may tell us that gravity was different long ago or something like that but it cannot contradict the general theory because we've tested it and tested it and we know it's right and the same with quantum physics there's a big puzzle people worries a few people most quantum physicists don't care they the expression is shut up and calculate now you've got the equations that work don't worry about why they work just do the numbers few people do care and they worry about the foundations of quantum physics as they put it what is it all about you know why do we have things like uncertainty how does a photon on that side of the universe know what a photon on the other side of the universe is doing there may be something beyond quantum physics in that sense but again it will tell us the same things that quantum physics does about all the things that quantum physics has already told us we know it's right and we know they're both right because of this so I think that's you know having told you that physics is right and I shall stop there and maybe take some questions if you've got any if we've only just discovered or theorized the existence of dark matter and dark energy is there room for another force

Channel: The Royal Institution

Views: 218,528

Keywords: Ri, Royal Institution, theory of everything, john gribbin, relativity, quantum theory, physics, theory, 13.8

Id: 8V669ohFOkI

Length: 53min 9sec (3189 seconds)

Published: Wed Mar 30 2016