"14 billion years ago there was nothing." "No stars, no galaxies, no planets or people." "Then suddenly, without warning, everything exploded into existence." "The universe was born." "That is what science says actually happened at the moment of creation." "Everything was created from nothing." "It's cosmology's greatest achievement, the discovery of how we came to be." "The atoms that make up me were once created inside a star." "Not only am I in the universe, but the universe is in me." "Cosmologist's have uncovered the universe's deepest secrets, revealing strange and exotic events only dreamed of before." "Events that formed the night sky." "But a new generation of cosmologists are questioning our basic understanding of the universe." "We need to understand what's the origin of time and space." "What was the universe actually like?" "I think these are the big questions." "I wish I knew what dark matter was." "Actually, I've been worrying about it for years." "They are beginning to wonder if there is a greater reality." "It's some kind of proxy for a deeper idea." "Too crude to be the real thing that really happened in the early universe." "Could it be that everything we think we know about our universe is wrong?" "Somewhere out in the universe there seems to be a disturbing force that we can't explain." "A force of astonishing power that appears to have bent trillions of stars to its will." "Gripping not just galaxies but whole clusters of galaxies spanning billions of light years of space." "And it's dragging everything towards a single point." "This mysterious phenomenon is known as dark flow." "And it shouldn't be happening." "It seems as though a very, very large region of the universe around us, about a billion light years across, is moving at a phenomenal speed in the cosmos." "It's an unsettling discovery, a unique movement on an unimaginable scale." "Galaxies simply aren't meant to race across space in the same direction." "It left us quite unsettled and jittery at times because this is not something we planned to find or expected to find in any way." "Dark flow is a new enigma." "It's the latest in a long line of mysteries that reveal our universe is far more exotic than science had predicted." "Anomalies that have to be resolved to reveal the true nature of the universe." "There are a lot of things we know more than ever." "At the same time there are big mysteries that we don't really quite know what's going on." "Cosmologists have come up with a series of controversial theories designed to make sense of the universe." "Like the theory of inflation, which claims that the universe suddenly expanded a quadrillion, quadrillion times." "We don't know what caused the universe to inflate." "We don't know what kind of energies, what kind of stuff was around in the early universe." "Or dark matter theory, which says the cosmos is filled with matter that's totally invisible." "It's cheating in this sense that maybe it's not like that." "And maybe we should just take things face value." "And even dark energy." "The strange energy of nothing that dominates everything." "It is a very unwelcome actor on the cosmic scene." "Nobody asked for it, nobody wanted it, nobody understands it." "Despite these uncertainties, scientists have written their own version of the greatest story ever told." "It's the story of creation and it starts with a bang." "The big bang." "The most violent explosion there has ever been bought everything into existence." "This early universe was hot, so hot, it contained only raging energy." "After just one second, some energy was transformed into the seeds of matter and the universe filled with a dense fog." "400,000 years passed as the universe grew and eventually the fog settled to form atoms." "There were no stars to shine just vast clouds of gas." "After a billion years one cloud became so dense, it burst into life and the first star was born." "Stars grouped into galaxies and finally, the night sky looked as it does today." "It's a great story, and for cosmologists, it's no fairytale." "This story of creation has been built with the most important tool in science." "The ability to turn physical events into mathematical equations." "Mathematics is like Plasticine." "It's flexible, it allows you to take ideas and move them around." "It allows you to explore them further." "The power of relating physical phenomena and converting them into an equation is that it lets you apply these relations in different situations." "By creating equations that describe how things work today, the cosmologists could then change their formulas to see how the universe behaved in the past." "Traditionally, we use physics to start with a present that predict the future." "You can also do it backwards and start with what we see around us in the present day and calculate what the universe must have been like in the past in order to end up like this." "And that's exactly how we've come to the conclusion that there was a big bang." "This has allowed cosmologists to create a mathematical replica of the universe." "It's called the standard model of cosmology." "The standard model of cosmology describes the entire evolution of the cosmos from an instant after the big bang, to the present day." "The standard model allows cosmologists to travel through time." "They can wind the maths back and see the universe as it was in the past." "It described the big bang and how the universe has expanded ever since." "It's a remarkable theory because it really does allow us to understand literally everything that we can see." "It works perfectly." "The problem is that it doesn't quite explain everything ." "The more cosmologists look at the night sky, the more they realise that their model isn't an exact copy" "In fact the standard model is something that's very, very simple, and that's its appeal, that's why it's lasted so long, that's why people really want to sign up to it." "Scientists do like things to be simple." "The problem is there are certain observations that we have that don't quite fit," "If the observations don't fit, it means the whole model could be undermined." "Now, a new generation of cosmologists are questioning the great model itself." "They think that the orthodox science could be very wrong." "Professor Joao Magueijo is a theoretical physicist." "We probably are on the threshold of a new era in physics and all these things are just symptoms that not all is well with the current theory." "Dr Kathy Romer is an astrophysicist who specialises in studying galaxies." "Everything that we've learnt, everything we've gathered is just a theory and it might well be wrong." "In fact, the fun is in the chase." "In fact, the greatest thrill of all would be to prove something wrong," "Max Tegmark is professor of physics at MIT." "We always have a love-hate relationship with the standard model." "We like all the predictions it can make for us when we're doing practical things, even though we mostly suspect in our heart of hearts that that's probably not the final truth." "Professor Pedro Ferreira, from Oxford, is a cosmologist." "I think we're at an interesting time where we're up against how perfect a model it might be." "Maybe the standard model is wrong and we have to come up with a better model." "For all its intricate mathematics, the standard model has flaws." "Built into it are a series of theories designed to explain observations that don't make any sense." "Theories that are incomplete and unproven but without which, cosmology's story of creation is just another story." "The standard model runs into its first problem when the universe is less than a second old." "The universe begins with a bang." "A mass of seething energy that expands from a single point." "It keeps expanding for just a quadrillionth of a second... ..when everything grinds to a halt." "Even though the classic big-bang theory of a hot expanding plasma early on explained a lot of things, it forced us to assume some very contrived initial conditions for our universe." "In physics, we hate unexplained coincidences." "If there's an unexplained coincidence in nature, it usually tells us that we're missing something, our theory is wrong or incomplete." "Big-bang theory says that the universe was created in an explosion." "But an explosion would produce a universe that was lumpy and messy, with patches that were vastly different temperatures from one area to another." "The real universe is nothing like this." "In all directions, the temperature appears to be almost exactly the same." "This temperature problem made the idea of the big bang itself seem completely impossible." "Something was very wrong with the standard model." "Re-writing the history of the universe is a daunting challenge." "But luckily, in 1980, one man stepped up to the task." "His name is Alan Guth, professor of particle physics, and his creation was the theory of inflation." "When I started working in cosmology there was a standard theory of cosmology, the big-bang theory." "We still, basically, think that the big-bang theory is correct." "But there are things that were just left out." "There's no understanding of the uniformity that we see in the universe." "The universe looks essentially the same if you look that way or that way." "No normal explosion would ever do that." "The problem is that all explosions produce a chaotic pattern." "Areas of extreme heat jostle with patches of cold." "And that doesn't match the smooth uniformity of our universe." "But Guth's theory of inflation has an answer." "Inflation gets around this problem, essentially, by varying the expansion history of the universe so that the universe starts out essentially dawdling with very low expansion rate for a period of time before inflation." "By allowing the universe to be small for longer," "Guth had found a way to let it all become the same temperature." "And it's during that time when the universe is incredibly tiny and not expanding that rapidly that it can come to a uniform temperature." "Then inflation takes over and suddenly magnifies that tiny region to become large enough to include literally everything that we see and very likely regions far beyond." "Guth's theory of inflation said that, out of the blue, our fledgling universe dramatically increased in size." "It expanded from something, which is quite small and crinkly, to something incredibly large." "It happened almost in an instant a very small fraction of a second." "Inflation says the universe started small allowing the temperature to become the same everywhere." "Then in an instant it underwent a massive expansion that left everything perfectly smooth and uniform." "Inflation explained a lot, but it was still a hypothesis." "To try and prove it, cosmologists scoured the heavens for evidence." "Using satellites, they photographed light from the very early universe." "The pictures that emerged showed a special kind of radiation called the cosmic microwave background." "This cosmic microwave background, this CMB, as we call it, we think of as the afterglow of the heat of the big-bang explosion itself." "The remarkable images allowed cosmologists to see the universe as it was 13 billion years ago." "These photons allow us to construct an image of what the universe looked like, at 380,000 years after the big bang, which is an incredibly early time." "As expected, they found that the temperature was the same in all directions." "When we look at this microwave background, we see that it has pretty much the same properties, you know, one end of the sky to the other." "The temperature of the universe is almost perfectly uniform, except for some tiny variations of one ten thousandth of a degree." "Variations that were actually predicted by Guth's theory." "Inflation predicted not only the range of temperatures that should be present today, but also the distribution of those temperatures." "That's what this graph shows... in theory." "The real test came when satellites accurately measured the actual temperature of the CMB." "The data points lie perfectly on top of the curve." "It's an incredible match between theory and observation." "It's one of those things that you look at and on the one hand it's very satisfying, but also unexpected." "Its powerful evidence, but not conclusive proof." "The most basic aspects of inflation can't be explained." "The theory can't say what actually caused it." "We don't know how inflation happened, we don't know what drove the universe to inflate." "It's caused some to wonder if this is really what happened to the early universe." "Inflation is not really very deep." "It's something really simple." "In a way, it's too crude to be the real thing that happened in the early universe." "If inflation really happened, it would have needed a kind of force far more powerful than has ever been seen." "Right now, we're nowhere near being able to create enough energy in our laboratories to create inflation or anything like it." "Even Guth doesn't have all the answers." "I think it's important to understand that this is not something that any of us working on it would say we know for sure." "It is a proposal, a theory." "We don't yet fully understand the physics of these energies, we are making large extrapolations in what we're talking about." "Inflation seemed to happen by magic and then stopped just in time before it blew the universe apart." "I'm not a great fan of inflation." "Whenever I teach it in my cosmology class..." "I actually wrote in my notes, "Your lecturer doesn't really like this theory."" "I don't like it because it seems too much of an add-on." "But saying that, it's the easiest way for us to get from the standard model to some unexplained observations." "Inflation, in a way, is an acquired taste for cosmology." "It's something which, if you're really trying to explain the early universe, especially if you're very lazy and you just want to get papers out, it's perfect because it gives you an answer." "But the maths does appear to work." "It creates a universe that looks as neat and ordered as our own." "Inflation could be sending all of science down a blind alley," "But published in 1980, the theory has become a key part of the standard model." "The new story of creation still begins with a bang." "In a fraction of a section, inflation expands the universe a quadrillion quadrillion times." "As it cools the building blocks of matter are formed." "Then gravity begins to takes effect." "But it's at this point that the standard model hits another problem." "When the cosmologists look at the night sky, they see something weird." "Galaxies aren't behaving the way they should." "What's interesting is when you look at galaxies, they seem to be spinning around too quickly." "According to Newton's Law of Gravity, stars on the edge of a galaxy should move more slowly than those closer to the centre." "It's a process clearly seen in our solar system." "The further a planet is from the sun the slower it moves." "The planets' speeds produce a line known as a rotation curve." "Galaxies should produce exactly the same curve." "But they don't." "Remarkably, when the speed of stars at the edge of galaxies are measured, they turn out to be moving just as fast as those close to centre." "The rotation curve isn't a curve at all." "It's more of a straight line." "This should lead to disaster all across the universe." "The galaxy would just fly apart at these very high rotation speeds." "To make the galaxies work the way the laws of physics dictated, the cosmologists needed more gravity." "The only way to get more gravity was to add more matter to galaxies." "But they couldn't find any, so they decided to invent some." "And so dark matter was born." "A key architect of this idea is Professor Carlos Frenk." "When we look at the way things move in the cosmos, we soon reach a very profound conclusion." "There isn't enough gravity in the stuff we can see, the stars or the galaxies, to explain how objects move in the universe, there must be something else, that is responsible for these movements, and that is what we call dark matter." "The new matter was called dark because they couldn't see it." "There has got to be something extra in these galaxies bulking them up, so that there's enough stuff for there to be enough gravity for them to be spinning around." "But this stuff is dark, this stuff is dark, it's invisible." "Dark matter explained the flat rotation curves and meant that the laws of physics still made sense." "Dark matter is the easiest way to explain why the galaxies work, the way they do and everything else." "When the calculations were done to work out how much unseen matter the universe should have, the results were shocking." "We expect that for every kilogram of normal matter, there's another five kilograms of dark matter and we expect that dark matter to be everywhere clustered around us." "The universe doesn't seem to be made from the same stuff that we're made from." "It's made of something else, something strange, something alien that we can't see." "Dark matter is wonderful stuff." "Wonderful stuff." "Without dark matter, the universe wouldn't look anything like it does." "Dark matter in general, I think, is one of the pillars of the standard model of cosmology." "It is needed - there's no doubt about that." "It's a persuasive theory but there is a fundamental flaw." "Cosmologists don't know what dark matter is." "All they know for certain is it can't be ordinary matter." "Because ordinary matter either emits light or reflects it." "Dark matter has to be totally invisible." "We have to not be able to see it at all wavelengths, so you wouldn't see it with an optical telescope, but you wouldn't see it with an X-ray telescope, or radio telescope either." "It really is dark at all frequencies." "But dark matter had to be more that just dark." "It needed to be a special form of matter, a kind of particle that had never been seen before." "What's even worse, it's not just invisible matter, it's exotic matter." "Things which are not atoms, which are not the things we know." "The idea of finding a new particles isn't as strange as it seems." "Physicists have found lots of particles over the years." "They all have different roles." "Some build atoms, while others make up light." "Particle physics has its own standard model, which catalogues these different particles." "Today, we have the standard model of particle physics, in which there are 24 elementary particles." "They all have their own values of mass, electric charge and spin." "They interact with each other in different ways so that in the standard model, these particles are grouped into different families." "It's just that dark matter can't be one of these." "None of the particles would be a good candidate for the dark matter because, essentially, the ones that are massive enough would not be dark because they would form into atoms that, in principle, could omit light." "But particle physics is also good at fixing standard models." "To make their model work they invented whole range of new particles." "If there was another set of 24 particles, identical to these ones, of the standard model, but with just one difference, the difference in the way in which the particles spin, this idea goes by the name of super symmetry." "Super symmetry predicts there are 24 new particles that have yet to be discovered by scientists." "And they're invisible...so dark matter could be one of these." "Not only are they invisible, they can pass right through solid objects." "Even stars and planets should be no barrier to dark matter." "Astrophysicist Dan Bauer is in charge of a special experiment." "He's hunting for dark matter." "He's not looking for it in space." "Instead he's buried his equipment ½ mile under the frozen plains of Minnesota." "It's strange at first, but you get used to it and once you pass through these doors it looks like any other lab." "You could be in one of those and not even know that you have a mile underground." "As dark matter should be able to pass through solid rock," "Dr Bauer has no trouble running his experiment underground." "You'd think it's easier to detect dark matter at the surface, why do we bother to come down this far, it's obviously inconvenient." "It's because that there's a lot of normal matter particles hitting the Earth's surface from space." "It would overwhelm any possible signal we could see." "But Bauer is facing a problem." "His dark matter detector is made of normal matter." "The kind of normal matter that dark matter passes right through." "If we are right about this dark matter particles streaming through us all the time, millions of them are passing by here every second, and they're doing absolutely nothing, in fact their passing through the entire Earth without doing anything." "Turn on the lights." "This massive block here is the actual experiment." "There's millions of dollars worth of the most advanced technology imaginable waiting to record the first evidence of the theoretical particles." "If they are real, and one of them so much as nudges Bauer's detectors, it would set of a signal that could provide the proof that cosmology's been waiting for." "Occasionally one of these particles will however do something in one of the detectors buried deep within this pile." "It will cause a little bit of heat and charge." "If we're very lucky then we will have detected a particle that makes up dark matter." "Theoretically, millions of particles have been streaming through Dr Bauer's machine every day for the five years it's been here, but frustratingly they've always left no trace." "But then something did happen." "Just this last December we saw the first two events that have the characteristics we might expect from dark matter." "But it's too few events for Bauer to be certain he's really found dark matter." "Despite the years of research and investigation, cosmologists don't seem to be much closer to uncovering what dark matter actually is." "If I, If I knew the answer to the question, "What is dark matter?" I would already be sitting very comfortably with a medal, being from the Nobel Committee." "There is very little doubt that the dark matter exists." "The question is, "What is it?"" "It's cheating in a sense that maybe it's not like that and maybe we should just take things face value and in fact what's out there is what there is... there's no dark matter, no ghosts around the universe." "But despite the doubts, cosmology needs dark matter." "It's the missing ingredient that makes the universe work the way the maths predicts it should." "And it puts the standard model story of creation back on track." "Creation starts with a bang," "Inflation takes over and everything expands." "After one billion years the first star is born." "Then dark matter kicks in." "It creates the gravity that makes galaxies form." "The universe continues to expand." "As the epochs pass the expansion slows." "Soon, the universe will come to a stop." "The trouble is this isn't what is actually happening." "The universe isn't stopping at all." "At the top of a mountain range in New Mexico is a very special instrument." "It's a finely-tuned device that scans the heavens." "This telescope is measuring the universe." "It's designed to work out how space itself is moving." "And what it's discovered has shocked cosmology." "Using the Sloan telescope, astrophysicist Saul Perlmutter recorded a new phenomenon." "The big surprise that we found, 10 years ago now, was that the universe apparently has been speeding up in the last half of its life, for the last seven billion years or so, there's been an acceleration in that expansion." "Everyone had been expecting that the universe was expanding." "But the standard model said the expansion should be slowing." "The universe was meant to be coming to a stop, but it wasn't." "This was a great scandal and it was a great scandal in a way because you know anyone reasonable would have expected that somehow gravity is attractive therefore the universe should be slowing down." "The pull of gravity from all the matter in the universe should be acting as a brake, bringing expansion to a stop." "Perlmutter's observations told a different story." "It's rare that you get to catch the universe in the act of doing something which doesn't fit." "So having the chance to have seen the universe do something that's completely surprising is, is tremendous." "Inflation theory had already established the big bang was no ordinary explosion." "Now Perlmutter was saying it was stranger still." "The explosion hasn't stopped." "The big bang is still banging." "Perlmutter's discovery created a new mystery to be resolved." "It suggested a new force was powering the universe." "And it needed a name." "They called it dark energy." "What is dark energy?" "Well, I know, but I'm not going to tell you." "Well, it's dark and it's expanding." "I guess it's a pictorial way to describe dark energy." "We don't know what it is so we might as well say it's this." "Actually, no, I've no idea what it is." "I hope it goes away, I don't like it." "We have no idea what dark energy is." "Dark energy is basically a fancy word for ignorance of what makes up 75 per cent of our universe." "I wish I knew what dark energy is." "I don't know and nobody else knows either." "It is a very unwelcome actor in the cosmic scene." "Nobody asked for it, nobody wanted it, nobody understands it," "This ignorance didn't stop the ideas coming in." "What could dark energy be?" "Was it an odd kind of gravity?" "Dark energy causes this type of anti-gravity where distant things are repelled from each other." "Or something entirely new." "If the universe is accelerating, something must be causing it and dark energy is just defined to be whatever it is that's causing the universe to accelerate." "Even a weird bit of maths." "When Einstein proposed his theory of space and time, he proposed this thing called the cosmological constant, which is this constant thing that pervades all of space, which would counterbalance the pull of matter." "Whatever dark energy is, whether anti-gravity, weird energy or maths, it seems to have magical properties." "Not only does dark energy make the universe expand." "But the more expanded the universe becomes, the more dark energy is created to fill the gaps." "This could only mean one thing." "There must be something in nothing." "Although we used to think that nothing was the simplest thing you could have, just complete emptiness, we now realise that there is no such thing as a completely empty vacuum." "If you take out all the air molecules from this space and take out all the light particles, there's still something left." "The very fabric of space itself isn't empty." "Deep space, the space between galaxies, is meant to be perfectly empty." "There shouldn't be anything there, not even the tiniest particle." "Instead, it seems this space is full of energy." "It might also explain the dark energy." "Maybe the vacuum itself has this energy which we can gravitationally measure throughout our space." "You take a space and you stretch it into more space..." "Well, that new stretched-out space has to have the same properties as the old space cos a stretched vacuum is still a vacuum." "It's yet another explanation for what dark energy might actually be." "So that's one of the prime contenders for what dark energy is - the energy of nothing, which is not nothing." ""Nothing" is taking over the universe." "It's creating more and more empty space, filled with even more nothingness." "Counterintuitive though it is, just like inflation, cosmologists need dark energy." "Even though we don't know much about it, it's the simplest explanation we have for some of the observations in the universe." "Like dark matter, dark energy isn't a solution, it's a description of a problem." "We're pretty much in the dark about dark energy." "There isn't a theory, a compelling theory." "There are hundreds of theories." "We don't know where it comes from, we don't know how it relates to the other particles in the universe, but that's an interesting challenge." "It means, you know, maybe this is going to be the next big thing." "The mystery is driving science on, making cosmologists re-evaluate what's really happening in the universe." "The dark energy seems to me really mysterious, and I think it's very unlikely that my generation of physicists will come to see the solution to the dark energy problem." "Mysterious though dark energy is, it's become an important part of the standard model." "It makes the maths fit with the real universe." "But more importantly, it seems to be the final piece in the jigsaw." "However counterintuitive the universe now is, it's the best model that we have, the most complete description of creation there's ever been." "The universe starts with a bang." "Then it suddenly inflates." "Dark matter forms..." "..and helps galaxies to emerge." "And the universe's expansion slows." "Finally, dark energy takes over, stretching the universe more and more." "After 13.7 billion years, cosmologists look up at the sky and understand the story of creation." "It's all thanks to the beautiful equations and elegant descriptions that make up the standard model of cosmology." "Today we have a very compelling standard model that describes a huge amount of observations and measurements." "Some pretty spectacular, like the fact that the universe was once hot, the fact that the universe is expanding, it explains why the...we're made of the elements that we're made, it explains where the atoms come from," "and it also explains, for example, where galaxies originate, how they ended up being the way they are." "So it's a very powerful standard model." "The unlikely combination of inflation, dark matter and dark energy has come good." "Cosmology's standard model works." "Except...that it now has a new challenge." "Another darkness to account for." "That new phenomenon, dark flow." "For Dr Sasha Kashlinsky, most days start the same way - taking the kids to school on the way to the office." "His office is at NASA's Goddard Space Flight Center." "Kashlinsky is a cosmologist." "What made me choose this career?" "I guess, in my childhood, it was reading too much science fiction." "I dreamt then of doing space travel and eventually instead of space travels," "I ended up doing cosmology as a desk job." "Say "bye-bye", gentlemen." "His desk job involves poring through pages and pages of data about the cosmic microwave background." "The picture of temperature differences in the afterglow of the big bang." "Hidden in these numbers, he's found something that shouldn't be happening." "This very nice map that they produced, is, um, is a nuisance for us, an obstacle." "Kashlinsky is looking for movements hidden in the map." "So we remove most of the signal that they detect, and then we concentrate only on about one per cent of this map associated with clusters of galaxies." "By stripping away the information, he's found distortions in the light coming from the microwave background." "Distortions that appear to show movement." "Whole clusters of galaxies seem to be moving in an inexplicable way." "It left us greatly puzzled when we found it, so puzzled that we, er, we didn't know what to do with it." "We sat on it for a year, checking everything, but ultimately it is in the data." "The CMB is the saviour of cosmology." "It had provided the evidence that validated the theory of inflation and allowed the standard model to work again." "Now the very same data could undermine everything." "It could easily point to something very exciting, a breakdown of our understanding of the universe." "Like dark matter and dark energy, these galactic movements were another mystery." "So Kashlinsky decided to call them dark flow." "He immediately sought to find a cause for this strange phenomenon." "A new, unseen force that could power dark flow." "He came up with a theory for what this could be." "All he needed was another universe, one that exists outside our own." "So, therefore we believe that in order to explain this flow, we should be looking outside of our universe very far beyond what is the gasmological horizon of the universe." "For Kashlinsky, our universe isn't everything, it's part of an even larger whole." "This apparently crazy idea is actually predicted by one of the pillars of the standard model." "Alan Guth's theory of inflation." "In almost all versions of our theories, inflation never ends completely, it ends in places and in those places where inflation ends, normal universes happen, but in other places the inflation continues and then ends again and another normal universe happens." "Guth thinks our universe is part of a bigger structure." "We're in a small piece of it, a bubble created by inflation." "So we end up with a picture of a multiverse consisting of many different universes which we, in this context, tend to call pocket universes, ah, we would be living in one of these pocket universes." "Ah, but inflation tends to produce not just one pocket universe, but an infinite number for the same price as the one." "It could mean that dark flow is evidence that our universe is not alone." "This would make it one of the most important discoveries ever." "Despite large parts of the standard model being built only on theory, it won't be easy for dark flow to change the science and join the model." "I think it's good to have a healthy dose of scepticism, we don't want to be, jump on fly-by-night theories, um, we want to make sure that if theory is going to change, it's a change for the better, and by better, I mean it explains our observations better." "Many modern cosmologists have devoted their careers to trying to find theories that could replace the standard model." "They have even tried to change some of the fundamental principles of physics." "I work a lot on trying to come up with alternatives which don't have this dark universe." "I've been involved with varying speed of light theory." "You want to bring everything into contact in the early universe, raise the speed limit." "They are hoping to find a deeper truth that will reveal how the universe really behaves." "I think the way that science works is there's always one big thing that most people work on and then there are always these side projects that other people look at and every now and then, one of these side projects is right and the big thing is wrong." "It's just that these cosmologists haven't been very successful." "I would say there's no shortage of alternatives, it's just none of them is compelling in a way that might make the whole community change and start working on them." "These attacks have meant that cosmology's standard model has gone from strength to strength." "The more they fail, the stronger the model becomes." "You get famous in science if you can be the one who shoots down the theory everybody else believes in." "So if the theory has withstood all this artillery fire from a lot of smart physicists and experimentalists for many years, that gives it a lot of street cred." "This is the key test for a theory in cosmology." "It's the hurdle that must be passed to enter the standard model and it's where dark flow currently falls down." "It hasn't yet been pushed to the brink of destruction and survived." "You really have to be very rigorous, and anything that you come up with has to be corroborated." "It has to be demonstrated to be the case, not just by one measurement, one experiment but by many different groups." "That's the essence of the scientific method, repeatability, rigour, accuracy and relevance." "It's not enough to make one measurement, find one thing that looks strange and say," ""Ah, this is true so there's a problem."" "You have to come at it with many different ways." "A lot of these results are tentative." "Some of these results are inconsistent with each other." "So, I think it's premature to incorporate these results as hard facts about the universe as we know it." "I think it's fair to say that it's, it's controversial." "For a long time it was controversial among ourselves, in fact, we did not think it was possible." "But ultimately, it's the data that decides and the data, to us, show very unambiguously that this is there." "The battle between resolving the mysteries of the universe and searching for new ones has driven cosmology on." "It's been a struggle to explain the unexplainable." "and has resulted in a powerful tale built on mystery." "So for now, the standard model remains unchanged." "It's successfully described so much." "It tells us how the universe began." "How matter and energy formed." "How gravity created stars and galaxies and planets like the Earth." "It's the best we have, and it's so nearly a perfect fit." "It's just that it could be totally wrong." "There's a feeling we need an extra clue, and we don't have it yet." "And I think that's what we're waiting for, somehow." "Subtitles by Red Bee Media Ltd" "E-mail subtitling@bbc.co.uk"