MONDAY [INLINE] 22 Feb 1999 [INLINE] [INLINE] Online BBC Homepage BBC Site Map [INLINE] Services Web Guide TV Listings Radio Listings Feedback Search Help [INLINE] Horizon [INLINE] Home [INLINE] Archive [INLINE] Contact [INLINE] [INLINE] Other BBC Science Sites [INLINE] Tomorrow's World [INLINE] Royal Institution Christmas Lectures [INLINE] Horizon navigation bar This week's programme script From Here to Infinity Thursday, 28th January 1999 [INLINE] NARRATOR (JEMMA REDGRAVE) In billions of years' time if you look out into the night sky you may see nothing, absolute darkness. A new discovery about the fate of the universe has sent scientists into turmoil and challenged their understanding of the fundamental laws of physics. MAN I was stunned by the results. I didn't believe them. MAN I really think deep down in your heart you know it has to be wrong, but this is not a good way for the universe to go. NARRATOR Saul Perlmutter is a physicist, an outsider to the world of cosmology. In 1987 he left behind a field of particle physics for astronomy to try and answer the ultimate question about the fate of the universe. DR. SAUL PERLMUTTER (Lawrence Berkeley Lab) The question that's been really exciting me is whether the universe will last for ever, do we live in a universe that, that is infinite, or will some day will come to an end. NARRATOR The quest Saul began 10 years ago was to lead to a discovery that would shatter our understanding of space and time and finally answer the burning question: will the universe last for ever? To discover how the universe would end Saul had to look back at the extraordinary way it all began. It started from nothing with the Big Bang. A hot, dense fireball in which time and space began 15 billion years ago. From this very first moment in time the universe has been expanding with stars and galaxies rushing apart in all directions, and in the deepest reaches of space distant stars billions of light years away are the stars that were born soon after the universe began. They would unlock the secret of the end of the universe. SAUL PERLMUTTER As you look at more and more distant objects you're seeing light that's been travelling for a long time to reach us and so you're actually seeing things way back in time, in a much earlier time in history. NARRATOR When Saul entered the world of cosmology he found two groups of scientists who had long been trying to discover how the universe would end. There were the theorists, who were using equations, and the observers, who worked through the night studying the stars through powerful telescopes. PROF. ALEX FILIPPENKO (Observer) Observers go out and measure properties of the universe. They do experiments, they do observations of distant stars and supernovae. MAN Kostos, we're all set to move. ALEX FILIPPENKO PVIR set up? MAN That's OK. PROF. ROBERT KIRSHNER (Observer) Observers are people who have a high tolerance for boredom. MAN 6.82. ROBERT KIRSHNER Don't mind being cold, are willing to work on something for a long time without any result. The theorists tend to be very intelligent, but also very impatient and they have no tolerance for personal discomfort, and they have a very high regard for their own aesthetic view, that is they seem to have a good sense of what is beautiful and what must be right, what must not be right. NARRATOR Far away from the telescopes the theorists have long been trying to make sense of the complexities of the universe. MAN I'm a theorist and even my mother doesn't understand what a theorist does. PROF. ROCKY KOLB (Theorist) A theorist tries to understand the universe by looking at equations, by working with a piece of chalk or a pencil, or at a computer. An observer tries to understand the universe by looking at it. They open the dome and look out in the telescope and they use their imagination that way. To me the universe consists of equations and symmetries and the laws of nature. To an observer the universe is something that's out there. To me the universe is something that's sitting in my office. NARRATOR Both the theorists and the observers have been trying, and failing, for 70 years to answer the question: what is going to happen to our universe? They felt there were only two ways an expanding universe could end. PROF. MICHAEL TURNER (Theorist, University of Chicago) We know the universe is expanding today but will it keep expanding, or will it re-collapse? That's one of the biggest questions and the whole fate of the universe hinges on that. NARRATOR Whether the universe goes on expanding for ever or re-collapses depends on only one thing: gravity, the force that pulls everything in the cosmos together and the only force that could halt the expansion of the universe. Gravity's an amazing force. It holds everything together, it keeps our feet on the ground and keeps the planets in orbit. Gravity pulls stars and galaxies towards each other. The more mass there is in the universe the stronger the force of gravity acting on it pulling it all back in. MICHAEL TURNER The universe is expanding, but gravity is pulling on it and trying to slow it down and trying to cause it to fall back on itself, but there's a lot of stuff in the universe, gravity will be very strong and it will pull the universe and cause it to fall back on itself and there'll be a big crunch. ROCKY KOLB If the universe re-collapses then distant galaxies will start approaching us. Eventually the universe will become so dense that all of the galaxies that we see today will merge into one giant firebomb and micro-seconds before the final collapse the universe would only be this large. Then the universe will continue to become smaller and smaller with all of the matter, all of the energy in the universe packed into an ever smaller volume, eventually reaching an infinite density and then space and time as we know it will cease to exist. MICHAEL TURNER On the other hand, if there's not very much stuff in the universe then the pull of gravity will not be able to overcome the expansion and the universe will just expand for ever, getting cooler and cooler and darker and darker. NARRATOR Scientists were convinced that the universe was slowing down, but to measure how fast it was slowing down and so discover its ultimate fate, they needed to compare the speed the universe was travelling early in time to how fast it is travelling now. ROCKY KOLB For 70 years astronomers have been trying to measure the change in the expansion rate of the universe. Every reasonable person expected that in the past the universe was expanding more rapidly than it is today, every reasonable person came to the conclusion that the force of gravity from all the mass in the universe would cause the universe to slow in its expansion. MICHAEL TURNER One way to determine the ultimate fate of the universe is to try to measure how much the universe is slowing down. We know it should be slowing down due to gravity. If we can measure that slowing then we can determine the ultimate fate of the universe, but to measure this slowing is very, very difficult. NARRATOR Into this world of cosmology stepped Saul Perlmutter. Like everyone else in the scientific community he knew there was one way to measure the slowing of the universe. He was aware how difficult it would be and knew many others had failed, but he was determined to crack it. If Saul could measure how fast stars were moving soon after the Big Bang by studying stars billions of light years away and compare them to how fast stars were moving now in nearby space, he could measure the difference in speed between the stars and that would tell him the rate at which the universe was slowing down throughout its history. But to use stars as markers throughout the cosmos he needed to find a certain type of star, a star that always burnt with exactly the same brightness, a constant beacon. That way he could tell precisely how far away it was in space and time. The dimmer the star the further away he knew it would be. SAUL PERLMUTTER Once you have an object which appears to be identical, or you can recognise it every time and if you can find them at great distances then you really have an unusual opportunity 'cos then we can use them to measure these great, vast distances across the universe. NARRATOR To see these identical stars, these constant beacons right across the universe Saul also needed stars so incredibly bright that however far he looked into distant space he would still be able to see them. The problem was finding anything that was constant in this ever-changing universe. MICHAEL TURNER The universe is filled with incredible things. It's like the most amazing zoo that you can imagine, so you look out there and you see stars exploding, stars being born, neutron stars that spin around 1,000 times a second. It's just a zoo that you could wander through for the rest of time. NARRATOR In the whole of this cosmic zoo there is only one type of star that is always the same and that shines with such an incredible brightness: supernova. Supernovae would be the key to measuring the expansion of the universe and reveal how it would all end. ALEX FILIPPENKO Supernovae are the colossal, gargantuan explosions of some very few stars at the end of their lives. They become as powerful as like 10 billion normal stars all shining at the same time, so a single star will blow up and put out as much energy as 10 billion normal stars. NARRATOR Very rarely across the universe a star explodes as it dies. As it steals matter from a companion star it becomes denser and denser, finally reaching a critical density. The consequence is dramatic. Compressed by the force of gravity it erupts in a cataclysmic explosion which can only be seen for a few weeks. As supernovae only ever explode when they reach this critical density, they always explode with exactly the same power source, exactly the same brightness. SAUL PERLMUTTER And what's really striking about supernovae is that in this explosion at the end of the star's life it, it becomes brighter just for this fleeting moment, for this few weeks it becomes brighter than the entire galaxy of 10 billion stars in which that one star lived and it's a chance to actually look at a single event that can be seen across the entire universe and I think that's a remarkable moment of time to be able to watch. NARRATOR For astronomers to use supernovae to measure the slowing of the universe they need to be able to recognise them out of all the billions of stars in the night sky and they can do this by analysing their particular spectrum of light. ALEX FILIPPENKO If you look in detail at a spectrum you'll notice that some colours appear fainter than other colours. That's because the light at those colours is being blocked by atoms of chemical elements in the supernova, so the spectrum of the supernova tells us what kind of chemical elements are in them. The spectrum of the supernova is really the supernova's fingerprint. NARRATOR Although astronomers knew how to recognise a supernova, the problem was that they were incredibly scarce. SAUL PERLMUTTER These distant supernova are really rare. They only explode a couple of times per millennium, so you either have to be really patient and watch one galaxy for 500 years or you have to come up with another strategy. NARRATOR To measure the slowing of the universe and its eventual fate Saul needed to find many of these rare beacons, but it was like finding a needle in a haystack. For years astronomers had tried to find them, but as they could not predict when and where a supernova would explode they never knew which part of the sky to search at just the right moment to catch sight of one. SAUL PERLMUTTER It's very difficult to plan to observe something which will just go up at some random time or explode, you know, any, any old time and you can't predict and guarantee that that you'll have a supernova, so in the early stages it really seemed like a very difficult proposition. NARRATOR But Saul knew he would need to find about 50 supernovae scattered through distant space, so he could use them to measure how much the universe had been slowing down throughout its history and answer the fundamental question about the fate of the universe. To get that many markers he would have to find these incredibly rare supernovae explosions on demand every time he went to the telescope. ROCKY KOLB The discovery of supernovae were rather haphazard. They would be discovered more or less by accident. People couldn't say I'm going to go out next Tuesday and discover 20 supernovae. MICHAEL TURNER The astronomical community was absolutely convinced that Saul would not succeed. They couldn't believe that an outsider, a physicist, would come in and do what they couldn't do for 70 years. SAUL PERLMUTTER There were lots of good reasons why it was going to be an impossible job to do and why we, we shouldn't even try, but privately we did want to know the answer to this question. I wanted to find out whether or not the universe was going to last for ever, I wanted to know, find out whether it was slowing down in its expansion and there weren't very many ways to do it. This was about the only tool available that we saw and I wanted to give it a try. NARRATOR What he didn't realise was that finding the supernovae would lead to the discovery of something else as well, something so mysterious going on deep out in space it was almost impossible to comprehend. In 1987 Saul and his team set out to find the technology they needed to hunt for supernovae. They came up with a strategy to increase their chances. SAUL PERLMUTTER What we wanted to do was look at thousands of galaxies at one time and that gives you reasonable odds that there will be a supernova exploding in one of those thousands of galaxies. The way to do that then is to build, design a new piece of equipment that would allow you to bring thousands of galaxies in a wide-angle image down onto a camera that could see all these thousands of galaxies in one shot. NARRATOR There was already a specialised wide-angle camera which Saul could modify, but it wasn't capturing enough of the sky to find supernovae on demand. He suspected this was because it needed much more powerful film. SAUL PERLMUTTER Once you have a wide-angle camera you need to find a CCD detector which acts as the film for this camera. NARRATOR Incredibly sensitive microchips, called CCD detectors, were being used at the time, but they were not strong enough. The needed one 10 times more powerful. But all was not lost. A group of astronomers in England had come up with the idea of using several of these chips at once in a mosaic of detectors. SAUL PERLMUTTER This new detector made it possible to capture more galaxies in a single explosion, in a single shot. NARRATOR When after several years the team finally assembled the camera it was capable of photographing hundreds of galaxies every 15 minutes. Saul and his team now felt sure they could find the supernovae they needed. Others were doubtful. MICHAEL TURNER When Saul started out many of us, including myself, were sceptical. After all he wasn't a real astronomer, he wasn't an expert on supernovae. People had tried the automated technique of finding supernovae before and had failed, so why should he succeed, but he was so self-confident and he was, he thought he could do it, so he had to weigh the scepticism that he was a rank amateur with this confidence and that he was going to bring in a new technique and he did have a better way of doing it. NARRATOR Saul and his team now faced another hurdle. SAUL PERLMUTTER Once you have a way of collecting thousands of galaxies in a single exposure, now you would need some way of being able to study those thousands of galaxies. NARRATOR The team's new camera produced a vast amount of complex images, so they needed computer software that could process pictures of billions of stars so fast that they could pinpoint a single dim supernova before its light faded from the universe for ever. SAUL PERLMUTTER We had to actually develop all the software from scratch. There was very little available at that stage that would do the different parts that we wanted and so we were writing codes that would do each of these different steps of the analysis. NARRATOR After 5 years of hard work the team felt they finally had the tools they needed to increase their chances of finding distant supernovae on demand every night they looked. But more trouble lay ahead. SAUL PERLMUTTER You had to convince people to let you use these large telescopes which are very precious commodities and you couldn't find the supernova until you had actually used these big telescopes. On the other hand, you couldn't get to use the biggest telescopes until you'd showed, proven to people that you could find supernova, so there's a real chicken and egg problem. NARRATOR Finally in 1992 they were granted two crucial nights at a telescope to test their technology. If it worked it would be the first step to finding out the fate of the universe. Saul's international team of scientists, including the British, were at telescopes around the globe feeding information to him down the internet. That night they set to work to find a supernova. They performed the crucial telescope run ending up with hundreds of images of the night sky. Back at the lab they had to process enormous amounts of data. They had to analyse every new spot of light the computer had identified to determine which one might be a precious supernova. They found nothing. SAUL PERLMUTTER We'd been working for hours and hours trying to analyse this data and nobody was finding anything in the data that looked really likely. Everybody went home rather frustrated, so I just said OK, I'm just going to sit here and keep going through the data sets until I can find that supernova. It was the time when the laboratory gets empty and, and quiet and I remember going down to the basement to use my computer there where the graphics displays were available and what I had to do was go through every one of the images that the computer had identified as an extra spot of light that it could find one image that we'd taken just the night before that wasn't there weeks earlier when we'd taken earlier images and every one had something wrong with it. You find well there's a spot of light there, it's true, but it's, it's clearly just a, a flaw in the, in the camera or this spot of light would look fine except for the fact that it's, it's clearly an asteroid that's pretending to be a supernova that just goes by. Then it must have been about 1/2 in the morning that I finally came across this one example where the computer showed a spot of light that I couldn't find anything wrong with. It looked like a supernova should look and I remember noting down what it was and the following morning when the team came in I showed them what, what I had and they said yeah, it's looks so to them too. NARRATOR They had found their first supernova. They had done what many thought impossible. They had found a reliable way to capture a supernova on demand. Saul now felt sure his team could find all 50 of the markers they needed to measure the fate of the universe. Horizon followed Saul and his team on a supernova hunt to see if they really could capture these rare exploding stars on demand. SAUL PERLMUTTER We have a colleague here, Wayne, who's up at the film. Hi Wayne. WAYNE Hi Saul. SAUL And he will be pointing the telescope for us. We'll ask him to look at a certain patch in the sky and once he is on the target to tell us. We'll then turn to the instrument panel here and start controlling the camera. The idea is it's essentially just turn it and open the shutter for a long time-lapse exposure. We usually do that 5 minute exposure and then once the shutter closes the image gets read out into one of the computers back here and Greg and Rob and their colleagues on computers will then be analysing the data and trying to determine whether or not we have a good enough image to be able to use it to hunt for the supernova. NARRATOR That night the team photographed hundreds of galaxies, billions of light years away. The next stage was to wait 3 weeks and take pictures of exactly the same patch of sky again. The team would then compare these two sets of images hoping that a new spot of light had appeared during the 3 week gap: a potential supernova. SAUL PERLMUTTER The first night was out at Hawaii where we observed thousands of distant galaxies in very, very deep images. This night, the second night, we're back in Berkeley and two members of our team, Peter and Greg, are in Hawaii sending us data that they're collecting of the exact same galaxies, exacting images over again, and the reason is that now here in Berkeley we will analyse it with the computers to find spots of light that are visible on the same galaxies now that weren't there 3 weeks before because those spots will be the supernova explosions that have occurred in those galaxies. (ACTUALITY CHAT) MAN Something is still confused. SAUL PERLMUTTER Yeah we think it may be the tube is too long. MAN Now there's two switches on the back of it. SAUL PERLMUTTER The data came in from the telescope back to here in Berkeley last night. We've been having the usual ups and downs of analysing it. We had the computers go down, the computers came back up again, but now finally we have the analysis completed, at least the computers' part of the analysis, and it's beginning to show us on the screen what it thinks might be a supernova and then we have to make the final decisions as to which ones we really believe are, are likely supernova then, so here the galaxy in which one might find a supernova and in this case the, I'm showing you the image from 3 weeks ago that we observed when we were at the telescope and you can now see what happens if I put on the image from a few hours ago in which at the telescope you can see a new spot of light appearing inside that frame there and that's what we think is a very clear signature of a, of a supernova. If you compare this image to the previous image by just attracting off the light from 3 weeks ago the only light that will be left is light from that supernova and so that's what the computer does for us here and you can see a spot, the only thing in the frame that shows up that wasn't there 3 weeks ago that is there just now. NARRATOR While Horizon was there Saul and his team captured on demand one of the rarest events in the universe: the brief moment of a star exploding in a galaxy millions of light years away. This would not happen again in that galaxy for hundreds of years. MAN Saul and his group were the first people to be able to demonstrate that supernovae could be discovered on demand. MAN Before Saul's work it was not fair that one can find enough of these distant supernovae, but he tried, he persevered and he found several of them and that got other groups interested as well. MICHAEL TURNER Often in science a problem is just waiting to be solved, it's just there and somebody has to walk in the room, maybe a fresh face, and say hey guys, this is how you do it, bop, bop, bop, and that's what Saul did and once he showed he could be done then other groups were able to very quickly improve upon his technique. NARRATOR Suddenly the whole astronomical community was buzzing with excitement. Everyone started searching for distant supernovae on demand, fine tuning Saul's methods, viewing thousands of galaxies in one shot. Astronomers knew if they could find enough of these exploding stars they could answer the biggest questions in cosmology. The race was on, the competition was fierce. MAN Well let's see. North is... MAN Well we can figure it out (TALKING TOGETHER) MAN We can do it in our head. MAN 1, 2 and this is (TALKING TOGETHER). It's about 4 hours east. OK, so there's the supernova... MAN And these two are the (TALKING TOGETHER) Yeah, much more recognisable. MAN That's better. MAN It helps if you're on the right galaxy (TALKING TOGETHER) MAN OK, alright, put the (INAUDIBLE) ROBERT KIRSHNER Supernova observing is the most exciting kind of observing I've ever done because OK, to discover the supernova and then right away you have to communicate the data to the other observatories where somebody's waiting to find out where the supernovae are and how bright they are, so it requires co-ordination all around the earth, it requires a tremendous amount of rapid work. Everything has to work right. DR ADAM RIESS (University of California, Berkeley) I think the most incredible thing is that when these supernovae exploded the Earth wasn't here, the Solar System wasn't here and these little particles of light left the supernova 8 billion years ago and it's been travelling that entire time and while it's travelling the stars formed, our Solar System formed, the Earth formed and then light formed on the planet and people formed and technology developed and we built telescopes and we built the telescopes high up on mountains and we opened the aperture and at that moment the photon got here and it was travelling the whole time and we just developed the technology just at the right time to be able to catch that photon. SAUL PERLMUTTER During one of these nights of observing at the telescope we were highly concentrated on all the problems and all the technical difficulties and issues and it's only maybe once in a night that you have a moment of breathing room. You're there observing these objects all the way across the universe, you're seeing light from a, a star that exploded why two-thirds of the way back to the beginning of time and it's showing up here now with our telescopes and it's going to tell us something about the universe. I think these moments do keep you going. NARRATOR After 5 years of searching Saul and his team had found 42 supernovae. They felt they had enough of these cosmic markers to make a stab at the crucial measurements. SAUL PERLMUTTER We finally finished the last observations, the last pictures of the 42 supernovas that we needed. We were now starting to analyse and look to see whether the universe was slowing down in its expansion. NARRATOR They now had to calculate the speed at which all these different markers were moving to discover the rate at which the universe was slowing down at each moment in its history. They expected distant early stars to be travelling much faster than nearby stars. That would tell them the fate of the universe, whether gravity would pull everything together in a terrifying cataclysmic crunch, or not. The calculations were enormous. On massive computers they ploughed through millions of equations about distance, spectra, speed and light curves for each star to find the magic number, the rate of the slowing of the universe. DR PETER NUGENT (Lawrence Berkeley Lab) Just at this time I decided to go on vacation, yet Saul wanted to know the answer as soon as possible. Unfortunately I left him with my phone number - something that my wife has never forgiven me for. Every night when I checked into the hotel and got my PC all hooked up Saul would call me and ask me what's going on with the data? SAUL PERLMUTTER Then we kept analysing more carefully and more carefully and doing each more, each of the steps of analysis that we had planned to do and as we did these steps it turned out that the data was homing in on an answer that was very different. PETER NUGENT Every time I looked I came back Saul this is what I got, this is the data, it's fake, it's not what we're thinking and he'd have me check it again and again and I'd ask Rob - Rob, is the data alright, have you reduced it correctly? MAN I sort of suspected that we were going to find some problem and it was going to turn out that it wasn't really right. NARRATOR They were seeing something quite extraordinary. The supernovae were 20% dimmer than expected. This meant that they were much further away in the universe than they should have been according to the known laws of gravity. PETER NUGENT I knew that the supernova weren't lying to me, yet another part of my brain was saying no, this is not a good way for the universe to go. NARRATOR They could not believe what they were seeing. They knew the universe should be slowing down in its expansion, that gravity should be tugging on it, pulling it in, but they were seeing something that defied the known laws of physics and all their expectations. SAUL PERLMUTTER The universe didn't appear to be slowing down. We, we thought that that's what we would see and it looked like the opposite was taking place and in fact the universe was speeding up in its expansion. NARRATOR The universe was speeding up, not slowing down. Even though gravity was pulling the universe in somehow the supernovae were still being pushed further away into deepest space. It made no sense. ADAM RIESS It's very weird. I mean it goes completely counter to our idea of what gravity does and what the universe should be doing. Gravity pulls on stuff. It would be like throwing an apple up and having it take off and go up instead of going down. I mean it's that weird. ROCKY KOLB I was shocked when I heard it, I didn't believe it when I heard it and I still have a hard time believing it. MICHAEL TURNER For 70 years we'd had, been trying to measure the slowing of the universe. Everybody expected the universe to be slowing down due to gravity and guess what, the universe is not slowing down, it's speeding up. If that's true that's got to be one of the most important discoveries of the century. NARRATOR At the same time that Saul Perlmutter announced this amazing discovery, Alex Filippenko presented his findings to the world of cosmology. He was even more convinced about his extraordinary results. ALEX FILIPPENKO I got up there and I said our team believes, at least right now, that the universe is expanding faster and faster and no-one in the history of astronomy had said with such conviction that they have good evidence for an accelerating expansion. What we've found is that the universe is pushing itself apart faster and faster. Now normally matter and energy don't do that. They pull on each other. That's what gravity is. It pulls, OK, that's what it does. We are held on to the surface of the Earth, for example, by gravity, yet here is an effect which over large distances pushes. That was quite unanticipated. It's as though the universe has presented a new face, nature has presented a new face toward us that we had not dreamt of before. NARRATOR Something was going on out there in space that no-one had expected. In desperation the theorists tried to make sense of it all. For months the blackboards were groaning with equations of possible predictions, permutations and assumptions as to what was going on. If the universe was speeding up against the force of gravity it could only mean one thing. There had to be some unknown and mysterious energy out there in the cosmos pushing everything apart, fighting against gravity. What could this powerful energy be, why had it never been seen before, what generated it and where was it hiding? The theorists' extraordinary conclusion was that this unknown energy came from the very vacuum of space. MICHAEL TURNER Now that sounds a bit crazy because a vacuum is supposed to be empty, but we know that the vacuum is not empty. Nature's vacuum is just seething with particles coming in and out of existence. ROCKY KOLB And this effect of the creation of particles and anti-particles at every point in the universe leads to an energy in the vacuum. NARRATOR The theorists believe that the universe is buzzing with particles which appear and disappear in and out of the vacuum of space, in and out of existence, leaving behind a huge, unexpected reservoir of energy and this bizarre energy accumulates over vast distances of space pushing against the force of gravity, flinging the universe apart faster and faster. ADAM RIESS It's got to be the weirdest idea in the universe, but the first thing you learn in science is if you have a vacuum that means there's nothing in there, you tell all the particles just get out, you clear out this space and that's nothing, it's a vacuum, but to learn that actually there might be stuff going on in that vacuum, there might be virtual particles which appear and disappear and are pushing on the outside of this space trying to make it bigger all the time, that is a very strange idea, very difficult to grasp. NARRATOR But when theorists reached back into the history books they found that one great genius had already predicted just such an energy. He'd called it the cosmological constant. MICHAEL TURNER When Einstein put forth his general relativity theory the first problem he sought to solve was that of the universe and his mathematical equation said that the universe should either expand or collapse, that it shouldn't sit still. NARRATOR At the time the scientific world was convinced the universe was sitting still, that it was static, so Einstein added an extra bit to his original equation to keep the universe from expanding or contracting. He called this the cosmological constant. His new equation stabilised the universe. ROCKY KOLB Then in 1929 it was discovered that the universe indeed was expanding and at this point Einstein realised that the reason he introduced the cosmological constant no longer existed and he called the introduction of the cosmological constant the biggest blunder of his life. NARRATOR But now it seems that Einstein may be right after all. The latest discovery means there really could be an extra energy, a cosmological constant in the universe, but not everyone agrees. The scientific world has been thrown into turmoil. ROCKY KOLB I don't think the universe is accelerating. Either the acceleration of the universe will turn out to be wrong, or it will turn out to point the way to really new revolutionary physics, new laws of nature and pointing the way to new laws of nature seem really too good to be true. NARRATOR After all the excitement had died down, Saul felt he had to provide firmer proof. Horizon followed him and his team to the telescope in Hawaii to look deeper into space than ever before. If he could find the most distant supernovae yet seen and it, too, was fainter than expected, it would add vital proof of an accelerating universe and a mysterious energy deep in space. SAUL PERLMUTTER If we open the shutter on this camera we're about half an hour to a time-lapse picture and after half an hour we close the shutter and read the camera out into the computer. Then it takes, well it'll probably take us another hour or so to analyse that data just to have a look to see whether or not it's showing these different colours that represent a supernova. MAN It looks like we've got the object. Keep an eye on it (TALKING TOGETHER) (ACTUALITY CHAT) NARRATOR As the night progressed the team finally found a faint object 10 billion light years away, a potential supernova. (ACTUALITY CHAT) MAN It's got moving space, it's a star. MAN (INAUDIBLE REMARK) MAN OK, let me know when we're guiding. NARRATOR Having found the object, the team now have an agonising wait ahead. They must analyse its spectrum of light to see if it has the distinctive fingerprint of the supernova. At dawn the computer revealed the answer. The team had found the most distant supernova ever seen, a star that exploded over 10 billion years ago when the universe was in its infancy and its light had only just reached us. SAUL PERLMUTTER We intended to find the most distant confirmed supernova and it looks like we're going (INAUDIBLE) supernova. That makes me feels good. NARRATOR Like all the other supernovae it, too, is dimmer than anyone expected. That adds strong evidence that there really is a mysterious energy out in space pushing against gravity, making the universe accelerate faster and faster. So what does all this mean for the fate of the universe billions of years from now? ALEX FILIPPENKO If the universe's expansion keeps on increasing with time, accelerating, then all of the galaxies will be pushed away from all the other ones and we will eventually become in a very empty region of space. All the other galaxies will have moved so far away from us that they will become essentially invisible. Now the universe will last so long if it continues to expand for ever like this, but the stars themselves will all burn out, so eventually when we look out into the night sky we'll see nothing but darkness - no stars, no galaxies, nothing, just darkness. MAN Can life go on? Well life as we know it won't be able to go on, but can intelligence go on? Maybe, maybe not. SAUL PERLMUTTER If you lived in those future days you'd go out at night and not see any of this rich tapestry of galaxies out there beyond our own galaxy. The world in fact becomes an emptier, lonelier place as I, as I see it and in some sense it'll become a colder, dying universe over the beyond. MAN Somebody turns out the light. The last star burns out and there's just darkness. SAUL PERLMUTTER We're describing a universe which may be infinite, it may go on for ever and already the mind has a hard time conceiving that things just go on endlessly, and to make it even stranger it originated from a period in which things were infinitely close together, they were, everything was infinitely densely packed and yet the universe was still infinite perhaps and the mind has such a hard time comprehending this sort of concept that the, that the name of the game is just to try to understand a little bit from this angle, or a little bit from this angle and see whether you can make some sense out of it at all and you don't expect really to understand it in the full sense that we think we understand the immediate world around us every day, but that little sense of, little glimpses of understanding I think are, are very exciting and, and make you feel like you're, like you're in touch with something that's a little bit magical.