How the Universe Works (2010) s06e11 Episode Script

Blow your Mind of the Universe

[Music] what is our universe made of it's the biggest unanswered question in science despite the name space is empty space at all space itself is something there's a hidden structure and a force that exists within space itself space is very much a dynamic incredibly active medium a force that connects everything in our universe it's an active player and the game of life it underpins our reality tying together all of space and time since the very beginning we call it space-time it's everything space-time is what the universe really is space-time is how our universe works but what exactly is it and how does it control our past present and future we can't see it we can't touch it but without spacetime we wouldn't be here space-time is a fabric of our reality it shapes and governs our lives if we want to understand the story of the universe it's absolutely crucial we understand how space-time behaves space-time has been active since the beginning of everything and is the key to the evolution of everything we have to understand space-time in order to understand the history of the universe to understand how the universe began how it evolved and what's gonna happen in the future the story of space-time is the story of our universe to know how the story plays out how it will end we need to go back to the very beginning [Music] to a time when there was nothing no stars no space a time before there was time then all of a sudden our entire universe was born in the Big Bang it started in a instantaneous moment where from nothing our universe was created the very definition of the moment of the Big Bang is that space and time were created at that instant it is as far as we currently know that coming into existence of space and time itself the infant universe a tiny speck of energy and space-time materializes from nowhere then the universe suddenly expands the idea of inflation is that a very tiny region in an incredibly short amount of time far shorter than a second grew by many many many orders of magnitude so imagine myself suddenly becoming the size of a galaxy in a fraction of a second the universe grew from smaller than the size of an atom to the size of a baseball in cosmic terms that's like a grain of sand growing almost to the size of the observable universe the universe at the instant of inflation actually expanded faster than the speed of light it seems to be a violation of everything you've heard in physics may be thinking hey hey hey mister astronomy guy nothing can move faster than the speed of light it turns out that's kind of true but the rule is nothing can move through the universe faster than the speed of light in inflation its space itself that is expanding so there is no violation there is no paradox inflating fast the universe went through a phenomenal growth spurt at the moment of the Big Bang space-time was this entity that was flying out in all directions it was space itself that was expanding but the universe didn't expand evenly one spot in the universe was ever so slightly more dense than a spot right next to it and we're talking abo tiny tiny fraction of a percent one part in a hundred thousand but that was enough fluctuations in expanding space-time created areas with higher density conflation made these high-density regions larger and this allowed our universe to take shape when parts of the universe didn't inflate quite the same way as others all of a sudden things could start to come together as the universe cooled energy turned into matter and in the denser regions that matter started to clump together crucially these regions had more mass than others mass bends space-time so anything that is made of matter bends space-time and the more matter you have in one place the more you bend it in fact I've been in space-time right now when I flex I've been it even more because of my incredibly high bustle density I don't bend at the maximum I don't want to destroy the earth in the solar system but you know it's an effect it's a real thing if I had imagined glasses allowed me to perceive directly to space-time suddenly those hidden aspects of a curved universe are as visible as the hand in front of my face we'd see a curving grid of space-time moving and reacting to objects within it and we'd feel the curving of space-time as the force we call gravity gravity is different from all the other forces it is intimately connected with the curvature of space-time something that can bend space and time has gravity that's what gravity is the bending of space and time itself it's hard to visualize this but a good analogy is a trapeze artist and their safety net can imagine a trapeze artist falling into a net on purpose that net is flat and looks like a nice orderly evenly spaced grid but when they fall into it they distort that grid well that's a lot like space if you have matter in space it warps the framework when the trapeze artist is resting in the net they're bending that space-time grid a little bit if you had two trapeze artists in there double the mass in roughly the same volume you would get a bigger dip you have a bigger distortion and that's how space-time works more mass equals a bigger curve in space-time equals more gravity but understanding the nature of gravity and space-time there's no easy thing it's an idea developed by one of the greatest minds ever Einstein had the idea that space itself is something something that can be bent something that can be stretched that we are all bound together by space-time Einstein says that space and time have a geometry they have a life of their own they have dynamics those dynamics are what we call gravity the more dense the region of matter the greater the gravity the deeper the curve this connection is the foundation of our physical reality is the interaction between matter and energy and space-time that created the universe that we see around us today but that doesn't mean we fully understand it there's much more that we don't know and that's frustrating with the laws of phys can talk about how space-time behaves but it does appear to be something that stretches that contracts and that gravity is the embodiment of space-time born in the Big Bang space-time and energy combined to create our infant universe these basic materials were the foundations but how did we get to the incredible complex structures we see today how did space-time build our majestic cosmos [Music] our entire universe was created in the Big Bang 13.
8 billion years ago everything came from nothing but our modern universe is a complex mosaic of matter I mean Marvel through our telescopes that the fantastic structure of our universe and it's galaxies if you ask where did that come from matter in the universe arranges itself on a vast cosmic web galaxies and galaxies clusters are strung out on sheets and filaments it seems this intricate web is organized by a cosmic architect space-time it shaped everything from planets to galaxies atoms to cities the universe is made of space-time whatever the substance is time and space bound together that's expanding and creating the universe we see around us it's everything space-time is what the universe really is it's a hard concept to grasp and even harder to visualize scientists observe the universe in different wavelengths of light this is the Sun in visible light x-ray and ultraviolet now imagine if we could see it in the space-time spectrum we would see space-time distorting as objects move through it spacetime can warp and push things around it can expand and pull things apart but it's the shape of space-time that dictates how we experience i imagine you're in your car you go up hills and you go down hills so the shape of Earth's surface determines how you travel across our surface in the same way the geometry of space-time determines how light and matter move through space-time the rules are simple matter in fact any object tells space-time how to curve the curvature of space-time tells matter how to move because the shape of space-time tells matter how to move what we call gravity this means that gravity and the shape of space-time tells matter how to clump together and form larger and larger structures but at the beginning the space-time landscape was very different from today's and the very first matter started to change the shape of space-time so this space right here has a tiny bit more matter in it than this over here wherever there was a little bit of extra mass that would Bend space a little more well if you're bending space a little bit more then more mass would collect there in the early universe the denser regions of matter created deeper curves in space-time and as the mass gets bigger as stuff falls into that well it gets deeper and deeper and deeper and attracts more stuff it's just a runaway process gravity increased pulling in more and more matter more times got more dad's got more downs and then before you know it you've got a star and you've got a bunch of stars and you start to make a galaxy and these stars evolved and began forming large structures they sort of burn through all their nuclear fuel and exploded and they made all the heavier elements and with time we got down to having things like planets atmospheres people all the things that we care about today all of this started out as energy fluctuations in expanding space-time these at first very tiny fluctuations became these gigantic structures that we actually see today and over billions of years that material began to coalesce into individual galaxies stars planets and you fluctuations in the expansion of space-time laid out the pattern of the universe the curvature of space-time controlled the evolution of everything we see today if space-time didn't have that property and bringing mass together then all we would be is a thin haze of hydrogen gas not a very interesting universal if space-time didn't curve because of matter inside of it the universe would be a really weird place I mean there'd be no gravity there'd be nothing to make things stick together no force of gravity means no stars no planets and no people we owe our existence to space-time but even scientists struggle to understand it I wish I knew what space-time is we know things about space-time but at the same time we feel like we know almost nothing about space-time then in 2015 we caught a break and for the first time we heard ripples in space-time generated by one of the most violent events in the history of the universe [Music] the universe is filled with space-time we think it's been around from the beginning of everything quietly pulling the strings of the cosmos [Music] and sometimes we get a glimpse of this elusive puppet master in action 2016 astronomers witness a strange optical phenomenon a weird circle of light like a cosmic halo this is actually what you would see in the sky if your eyes were as sensitive as a telescope they're real this is not some artifact of how we adjust the images something is actually bending space and time itself into a lens that something is a red galaxy which is over 7 billion light years away from Earth it's bending the light from a blue galaxy which should be hidden behind it it's called gravitational lensing gravitational lensing is an amazing phenomenon because it demonstrates explicitly what Einstein told us that space is curved and space acts like a lens just like the lens in my glasses act and when you look out at the universe we see all of that it's remarkable mass from the foreground galaxy creates curves in space-time which we know is gravity light follows those curves and is warped so it bends around the galaxy massive objects like clusters of galaxies can bend the path of light through space-time a lot like a piece of glass can bend the path of light so when we look at a distant galaxy as the light passes through a galaxy cluster we see multiple images of the same galaxy we see arcs in circles as if that galaxy cluster were made of glass we are seeing the warping of space-time literally played out in front of our very eyes gravitational lensing gives us a way of seeing the effects of space-time on light but it's only an indirect observation of space-time could there be another way of experiencing space-time right here on earth not everything that happens in space can be seen sometimes you have to listen for it as well believe it or not space is a material much like this iron sheet and like this iron space can distort if I put a very heavy weight on this sheet of metal its shape is gonna change and it's gonna distort amazingly space can carry waves and so can this iron sheet but to get this sheet wavy you need something really powerful something like me and my hammer did you see those ways to travel to that iron sheet well waves pass through space in exactly the same way we call these gravitational waves gravitational waves are vibrations from cosmic events transmitted through the material of space-time to set off waves in space you need the biggest baddest most powerful events in the universe something like the collision of two black holes when two black holes collide the energy released sends shockwaves through space-time across the universe by the time they reach Earth they're so small they're immeasurable almost in scientists at the LIGO Observatory made a groundbreaking observation [Music] they detected ripples in space-time gravitational waves rumors began flying but became clear after a while that this was indeed the first direct detection of gravitational waves seen by man-made instruments on the earth when we discovered gravitational waves it had been so long that we've been waiting for signals not only did most of us not believe it I went so far as to be so skeptical as to look into all kinds of conspiracy theories for ways it could be faked when I saw this data I still think back on it now and the emotional impact it has on me the only thing comparable is when I saw my daughter's face for the first time after she had been born it was that kind of an emotional impact just having all of this things that we had worked for coming to fruition in one moment it's mind-blowing we can actually hear these gravitational waves on earth part of what makes us so amazing it's a bit of a coincidence but it's a really cool coincidence is that the signals that LIGO actually measures are in the same frequency band as the sounds that the human ear is sensitive to we can hear the waves change frequency as the two black holes get closer and collide it's a swoop up in frequency that sounds like what we were hearing in that what were two black holes that are orbiting around one another and then coming together that was it listening to ripples in space-time has given us a powerful new tool to investigate the universe we are now hearing things in gravity for the first time it's a sense that we have never been able to apply to the universe and we're beginning to learn what is out there the observation of gravitational waves from black holes is one of the most significant findings in astronomy by anyone in the recent hundred years it's hard to overstate the importance of gravitational wave astronomy much like when Galileo first pointed his telescope at the stars to see something new we now have an entirely new window into the universe gravitational lensing and gravitational waves offer us an insight into the complex relationship between gravity and space but what about the other half of the equation time but it turns out you know it's space time gravity not only distorts space it actually distorts time too we think of time is something that can't be changed it simply flows ahead at a constant rate but that's not the universe we find ourselves in and some crazy circumstances my time might even according to you stop [Music] it might even be possible to travel through time and go back to the f you [Music] for sci-fi fans space is the final frontier for scientists exploring time is a much bigger challenge originally we thought of time is the same thing as the Sun rising and setting but now we've come to realize the time is a more fundamental concept than that time isn't just something that passes time is an essential part of our universe it's part of the fabric of space-time the Big Bang was the beginning of space and time since then space has been expanding and time has been ticking forward it's been doing this for 13.
8 billion years creating the universe we see today space and time are tied together they're that they're the same thing so when matter influences space time it's not just creating deformations in space it's also affecting the flow of time this is where space-time becomes really cool just as gravity bends space it also distorts the flow of time this isn't how we perceive time this is actually the rate at which time flows very massive objects can warp and twist space-time itself so not only is space distorted but time itself can slow down or even stop the stronger the gravity the greater the distortion what has the most gravity a black hole found in space near a strong gravitational tug from a black hole clocks can do funny things and this is where things start getting really interesting around a black hole space time warps and twists slowing time down scientists dream of sending a probe there to test their hypothesis there's a famous way of thinking about this called the twin paradox where two twins are born on exactly the same time right so they're the same age butfont color="#CCCCCC" them zips very very close to a black hole hangs out awhile and then comes back if I had an identical twin who stayed back on earth while I flew near a black hole when we had our daily video phone calls he would see me and I would see him talking to funny we would literally notice that time is running in a different pace for all the other one the closer to the black hole the slower time passes if instead of coming back home I accidentally fell backwards into the black hole my twin back on earth would see me slow down even more I go and completely dried the halls and seemed frozen on the event horizon time appears to stand still I would just have a sinking feeling that never would be able to come home again but if the twin could escape from the black hole he would be returning to the future maybe it's only been a few days or weeks experienced by the one that travelled to the black hole while the other is you know gray-haired and as grandkids by now as it lived decades here on earth the black hole warped space-time so much that the ultimate science-fiction fantasy becomes reality time travel is a staple of science fiction and we know that time travel into the past appears to be ruled out in our universe but time travel into the future i totally acceptable time travel is impossible just yet but space-time hasfont color="#CCCC very real effect on our daily lives it controls how we age the key to different rates of flows of time is gravity if you experience different gravitational environment you will have a different flow of time as I climb up these stairs and I put myself further away from the mass of the earth my own clock runs a little bit faster if you go down closer to the surface the more your clock slows down we have sensitive enough clocks that we can measure this different flow of time exaggerate this effect and we would see the flow of time change in front of us those closer to the earth would look slowed down those higher up the opposite which means the wealthy in their pent houses actually would age faster than people on the ground this is a mind-blowing concept but it's reality Earth's gravity even controls time high above the planet twelve and a half thousand miles up there's an array of global positioning satellites crucial to the navigation systems and our cars and cell phones we here on earth use the global positioning system as a way of getting around okay most people t days would be lost if they have to go more than about a kilometer from their house unless they have their GPS app on their phone to tell them where to go the GPS receiver in your cell phone bounces signals over four satellites to figure out exactly where you are it's an exercise in precision timing onboard each satellite is an atomic clock the weaker gravity in orbit means the satellite clocks tick fractionally faster than those on the ground if we didn't know to correct for the fact that the clocks and our satellites move at different rates the GPS system here on earth would not work it would actually lose accuracy at such a rate that the entire global positioning system will become useless in less than an hour we correct for that every moment of every day space-time has controlled every phase of the universe's evolution since its birth now we're discovering space-time will also dictate how the universe will die [Music] our universe started with a bang 13.
8 billion years ago it's been expanding ever since well this expansion lasts forever or will our universe come to a violent end [Music] for almost a hundred years we've now known that the universe is expanding everything in the universe is expanding away from everything else we can test this by measuring light from exploding stars type 1a supernovas all explode with the same brightness so scientists can accurately work out their distance from Earth for decades astronomers have measured this light being stretched by expanding space-time the universe is expanding and there's matter in it that matter has gravity and that is distorting the curvature of space-time so it made sense to us that as the universe expanded all of the matter in the universe would hold on to eachfont color="#E5E5E5" gravitationally if there's enough matter in the universe it can actually pull on itself enough that the expansion gets slower but in 1998 astronomers took new measurements and made a sensational discovery people had expected it to be slowing down to decelerate but instead they found the opposite the expansion is accelerating if expansion was slowing then these distant lights should seem brighter instead they were dimmer they were getting farther away much faster than expected it could only mean one thing that expansion is getting faster it's accelerating every d this discovery turned our understanding of the universe upside down for the first seven billion years of the universe the rate at which the universe was expanding was going slower and slower but then something crazy happened It was as if gravity had become the opposite instead of attracting the galaxies it was almost as if it was pushing them apart that's a very surprising result we're still struggling to understand it was gravity losing its power where was there something else pushing space apart there's another ingredient in our universe an ingredient that behaves very oddly the mysterious quantity called dark energy like space-time dark energy is all around us we can't see it but it makes up 70% of the stuff in our universe but what is it exactly dark simply means that we have no idea what it is we don't know what form it is in something is pouring energy into the universe causing it to accelerate we don't know what it is no clue whatsoever we don't have the slightest explanation it's the biggest mystery in science today dark energy behaves in mysterious ways ordinary matter is attractive dark energy is repulsive that's why it's causing an acceleration ordinary matter feels gravity it comes together but this stuff doesn't is dark energy a new force in the universe or like gravity could it come from space-time itself dark energy may very well be a property of space-time it may be that space itself has an energy and it's this energy that's driving it to accelerate in its expansion dark energy is a thing we don't really know exactly what it is but it will have a huge effect on the future changes in the universe so what will happen if dark energy keeps accelerating the expansion of our space-time universe because of the presence of dark energy it'll expand faster and faster and faster which means the universe is going to become a lonelier and lonelier place to be all the galaxies are accelerating away from each other the universe gets dimmer and dimmer and colder and colder everything gets darker and more desolate and right now that is the leading candidate for what's going to happen in our future eventually our space-time universe freezes the big freeze is the ultimate end game of the universe as we know it it is an ugly fate it's a depressing fate but luckily for us it's not until an unimaginably long time from now trillions of years from now the universe could end in a big freeze but a 2017 study hints at an even more frightening possibility dark energy might be getting stronger one horrible scenario for the ultimate fate of the universe is if dark energy eventually grows so strong enough that it can overwhelm the gravitational attraction of a galaxy itself it's even able to rip black holes apart the very fabric that holds everything together to be ripped apart this idea is called the big rip first clusters then galaxies like our own Milky Way will be torn apart then our solar system will break up and in the final half-hour of the universe the earth will explode in the final second atoms will vaporize everything in the universe would individually be torn apart by the expansion of space we don't understand dark energy is it constant is it getting stronger is it getting weaker at this stage we simply don't know the future of our space-time universe hangs in the balance will it end in a big rip a big freeze or is the end really just the beginning [Music] spacetime controlled the birth of our universe it will also dictate its death now we're discovering these two events may be linked a link that reveals a flaw in our understanding of the Big Bang everything we can now see all the matter all the energy in our universe was once contained in a region smaller than the size of an atom we call this tiny infinitely dense point a singularity singularities are predicted by the general theory of relativity but the universe is also governed by another set of rules quantum mechanics quantum mechanics is our description of the sub atomic realm of fundamental particles and fields and forces in how they interact [Music] quantum mechanics says that nothing can be infinitely small or dense so singularities can't exist singularity is a bit where everything kind of goes to hell because the densities become infinite gravitational forces become infinite things just sort of break down there in the equation sort of stop making sense no singularity would mean no Big Bang as we understand it so then how did the universe spark into existence scientists now think they have an answer a solution that works with both general relativity and quantum mechanics quantum space-time a successful theory of quantum space-time should answer the question of what really happened in the earliest moments of our universe hopefully the correct quantum theory of gravity won't have any singularities it will replace the Big Bang with something else if we only knew what that something else was we might have a clue as to how and why the universe began in a quantum space-time Big Bang there was no singularity bursting from nothing the universe formed from the remnants of another dying universe it's possible that before the Big Bang there was still universe there was still space and time but rather than expanding the universe was contracting perhaps universes don't end in rips or freezes perhaps they collapse an ancient universe expands but then begins to collapse under its own gravity crunching spacetime down to a spec but instead of forming a singularity space-time once again explodes as mater gets more dense than as the mater crunches down this force will push everything back out the universe would bounce and reignite in a new round of expansion a new Big Bang what we perceive as the Big Bang is the aftermath of that bounce this suggests that the space-time that dictates our lives today comes from the collapse of an old universe and we live in an infinite space-time cycle of birth death and rebirth a bouncing space-time universe if we live in a bouncing universe it's very plausible the universe is infinitely old that it's gone through an infinite series of bounces and there is no absolute beginning it could be that we are just one iteration of an infinite number of cycles in the lifetime of some meta universe we barely understand space-time perhaps we will never understand it completely but one thing is clear without spacetime we would not be here spacetime is something absolutely real it's really part of the fundamental architecture the furniture of reality to really understand the ultimate faith of our cosmos it's not enough just look more with our telescopes you also have to understand the basic nature of space-time you you really are right now living in a far more complex and beautiful universe than the human mind can comprehend [Music]