The Fabric of the Cosmos: Universe or Multiverse HD & HQ

lying just beneath everyday reality is a breathtaking world where much of what we perceive about the universe is wrong physicist and best-selling author Brian Green takes you on a journey that bends the rules of Human Experience why don't we ever see events unfold in reverse order according to the laws of physics this can happen it's a world that comes to light as we probe the most extreme real of the cosmos from black holes to the Big Bang to the very heart of matter itself I'm going to have what he's having here empty space teams with

ferocious activity the three-dimensional world may be just an illusion and there's no distinction between past present and future but how could this be how could we be so wrong about something so familiar does it bother us absolutely there's no principle built into the laws of nature that say that theoretical physicists have to be happy it's a gamechanging perspective that opens up a new world of possibilities coming up what if new universes were born all the time in this picture the Big Bang is not a unique event and ours was one of numerous parallel realities somewhere

there's a duplicate of you and me and everyone else else are we in a universe or a Multiverse the fabric of the cosmos right now on [Music] Nova major funding for Nova is provided by the following David H [Music] Coke and discovering new knowledge hhmi and by the Corporation for Public Broadcasting and by contributions to your PBS station from viewers like you thank you major funding for the fabric of the cosmos is provided by the National Science Foundation where discoveries [Music] begin and the Alfred P Sloan Foundation supporting original research and public understanding of science

technology engineering and Mathematics additional funding is provided by the Arthur Vining Davis foundations dedicated to strengthening America's future through education the US Department of Energy's office of Science and the George D Smith [Music] fund [Music] New York City they say there's nowhere else like it home to 8 million people countless structures monuments and landmarks every one of them unique or so we think uniqueness is an idea so familiar we never even question it experience tells us people and objects are one of a kind why else would we visit museums and collect great masterpieces yet a

new picture of the cosmos is coming to light in which nothing is unique not that the world's great masterpieces are fakes instead I'm talking about something far more profound a new picture of the cosmos that challenges the very notion of uniqueness one in which duplicates are inevitable and that's just the beginning there might be duplicates not just of objects but of you and me and everyone else but if this new picture is right where are these duplicates and why haven't we ever seen them [Music] the answer May lie outside our universe there was a time

when the word Universe meant all there is everything the notion of more than one Universe more than one everything seemed impossible but perhaps if we could go beyond our solar system beyond the Milky Way even Beyond other disant galaxies past the end of the observable universe will find that there's more a lot more that our universe is not alone there may be other universes in fact there might be new ones being born all the time we may actually live in an expanding sea of multiplying universes a Multiverse if we could visit these other universes we'd

find that some might have basic properties of nature so foreign that matter as we know it couldn't exist others might have galaxies Stars even a planet that looks familiar but with some surprising differences and if there are an infinite number of universes in the Multiverse somewhere there's a place where almost everything is identical to ours except for the slightest details like maybe there's another Brian Green who ends up in a different line of work if the Multiverse is indeed infinite then one is going to have to confront a lot of possibilities that are very hard

to imagine there'll be other places where there'll be Alan Goose will look and think and act exactly like me as well as many were Alan goose who look and think almost exactly like me but with some small differences is it science is it a part of metaphysics is it just philosophy is it religion physicists tend not to ask those questions they just say let's follow follow the logic and the logic seems to lead there however unfamiliar and strange the Multiverse might seem a growing number of scientists think it may be the final step in a

long line of radical revisions to our picture of the cosmos that is there was a time when we thought that the Earth was at the center of the cosmos and that everything else revolved around us then Along Came scientists like Galileo and cernus and they showed us that it's the Sun not the Earth that's at the center of our solar system and our solar system it's just a little neighborhood in the outskirts of a gigantic Galaxy and our galaxy it's one of hundreds of billions of galaxies that make up our unit Universe now all of

these ideas sounded outrageous when they were first proposed but today we don't even question them the idea of a Multiverse may be similar it simply may require a drastic change in our Cosmic perspective on the other hand some scientists think that the Multiverse is nothing but a dead end for physics I'm very uncomfortable with the Multiverse to become solid science it's got a lot lot of growing up to do you know it exists in the same way that you know Angels might exist we have to make our bets and I think right now the Multiverse

is a pretty good bet I think there's a good chance that the Multiverse is real and that 100 years from now people might be convinced that it's real so where did this idea come from and what's the evidence for it well several surprising discoveries suggest that we really may be part of the Multiverse the first of these discoveries has to do with the generally accepted theory of the origin of our universe the Big Bang according to this Theory our universe began some 14 billion years ago in an intensely violent explosion over billions of years the

universe cooled and coalesced allowing the formation of stars planets and galaxies as a result of that explosion the universe is still expanding today but if you could run the history of our universe in reverse all the way back to the beginning you'd find that the Big Bang Theory tells us nothing about what sent everything hurtling outward in the first place it's called The Big Bang Theory but the one thing that it really says nothing about at all is the bang itself uh it says nothing about what banged why it banged or what happened before it

[Music] banged so what fueled that violent explosion what force could have driven everything apart the quest to figure that out would bring scientists face to face with the Multiverse one physicist whose work unexpectedly helped lay the foundation for the Multiverse idea is Alan goth today he's a professor at MIT but back in 1979 Guth and a colleague Henry Tai were pursuing a new idea about how particles might have formed in the early Universe Henry suggested to me that we should maybe look at whether or not this new process that we were thinking of would influence

the expansion rate of the universe goth and Tai hadn't set out to investigate the expansion rate of the universe in the first moments after the big bang but Henry Tai's question caused goth to review their calculations one more time I stayed up quite late that night and went over the calculations very carefully trying to make sure everything was correct as the night wore on goth discovered something extraordinary in the equations describing how new particles might have formed in the early universe and came to the shocking conclusion that these new fangled particle theories will have a

tremendous effect on the expansion rate of the [Music] universe the kind of process Henry and I were talking about would drive the universe into a period of incredibly rapid exponential expansion what goth found in the math was evid that in the extremee environment of the very early Universe gravity can act in Reverse instead of pulling things together this repulsive gravity would repel everything around it causing a huge expansion I immediately became very excited about it and scribbled out the calculation of my notebook and then at the end I wrote spectacular realization with a double box

around it so I realized that if it was right it could be very important by discovering this repulsive gravity Alan goth had unintentionally shed light on the very beginning of the Big Bang described mathematically this force was so powerful it could take a bit of space as Tiny as a molecule and blow it up to the size of the Milky Way galaxy in less than a billionth of a billionth of a billionth of a blink of an eye after this incredibly short outward burst space would continue to expand more slowly and cool allowing stars and

galaxies to form just as they do in The Big Bang Theory Guth called this short burst of expansion inflation and he believed it explain what set the universe expanding in the first place the powerful repulsive of gravity of inflation was the bang in the Big Bang but despite having made a momentous breakr Allan goth had an even more pressing concern I had no idea what my employment might be I was really looking for a more permanent job the inflationary Universe scenario looks very exciting so I went on actually a pretty long trip giving talks about

this I call the inflationary suddenly uh this idea caught on talks about inflation were were packed with people from all areas of physics lots of astrophysical theorists including me got very enthusiastic it was a very very exciting time if you have a really good idea that allows other people to move the field forward people are going to pay attention an amazing feeling that suddenly I had crossed that Gap from being an unknown post talk to being one of the major players uh and it uh uh it was very hard to absorb but certainly felt good

one reason inflation was so exciting was that it made predictions that could be tested through observation scientists realized that if the theory were correct evidence for it should be found in the night sky imagine that we could shut off the sun and take away all the stars if our eyes could detect the rest of the energy that's still there we'd see a warm glow everywhere in the cosmos this sea of radiation is called The Cosmic microwave background it's the last remnants of heat from The Big Bang itself Theory predicted that the violent expansion of space

during inflation would leave an imprint on this radiation these Telltale fingerprints would form a precise pattern of temperature variations slightly hotter spots and slightly colder spots that would look something like this but it would be about 10 years before the technology was sensitive enough to test this prediction Del then in 1989 NASA launched the cosmic background Explorer satellite followed by a second satellite W map in 2001 that would put inflation to the test the missions measured the radiation with tremendous precision and the results were stunning the temperature variations found in the cosmos or an almost

identical match with the predictions of the theory of inflation it's just a theory mathematics on the page until it makes predictions that are confirmed W map found what the math of inflation predicted that is enormously convincing so inflation has had a number of chances now to fail it made predictions data came in and inflation has come through with flying colors guth's work on inflation along with that of other physicists was hiled as a milestone toward understanding the origin of the universe in the process it expands but soon two Russian physicists would discover that the equations

of inflation held a shocking secret our universe may not be alone one of these physicist was Andre Lind who had already made pivotal contributions to inflationary Theory the other was Alex venin who happened to attend one of the talks Alan Guth gave during his road trip [Music] gave a wonderful talk I haven't met him before but uh what I heard was rather unexpected in its early period in one shot inflation explained very well many features of the big bang and was quite remarkable why the universe is the way it is so I went home greatly

[Music] impressed Alex Lankin was so impressed that for months afterward he couldn't stop thinking about inflation usually I have my thought of the day in the shower which I tend to take long the more Val Lankin considered the process of inflation the more he wondered about what would make it stop how would a region of space transition out of inflation what EX exactly what happen at the moment inflation ends as I thought about it it turns out that the end of inflation doesn't happen everywhere at once the Lankin suddenly realized that if inflation doesn't end

everywhere at once then there's always some part of space where it's still happening so in this picture the Big Bang is not a unique event that happened there were multiple banks that happened before ours and there will be countless other banks that will happen in the future it was a striking and unexpected new picture in which inflation would stop in some regions but always continue somewhere else new Big Bangs are always occurring and new universes are always being born yielding an eternally expanding Multiverse Linda and bankin in particular pushed the idea that inflation might never

end that this ballooning process could happen over and over again giving one Universe after another after another so was this a revolution in science or a theory that's full of holes the idea became known as Eternal inflation and you can picture it something like this imagine that this block of cheese is all of space before the formation of stars and gas galaxies now according to inflation space is uniformly filled with a huge amount of energy and that energy causes space to expand at an enormous speed as it does here and there the energy discharges sort

of like a spark of static electricity but this is like static electricity on a cosmic scale and when it discharges all that energy is rapidly transformed into matter in the form of tiny particles that process is the birth of a new universe what we have traditionally called The Big Bang inside these new universes which are like holes in the cheese space continues to expand but much more slowly and sometimes galaxies Stars stars and planets form much as we see in our universe today meanwhile outside of these new universes the rest of space is still full

of undischarged energy and is still expanding at enormous speed and more expanding space means more places where the energy can discharge into more big bangs and create more new universes and that means this process could go on forever in other words when it comes to Eternal inflation that cheese is more like swiss cheese in which new universes endlessly form creating a Multiverse the Multiverse a profound implication of Eternal inflation but as Alex Fain would soon learn one that would not be easily accepted I thought I realized something important about the universe and I wanted to

share this with my fellow physicists and uh one of the first of course had to be Alan G now they know that Quantum fluctuations in the scal of field are different in different regions in space mhm I thought he would be excited about it as a result in some regions but actually this in count it didn't go as planned inflation will last longer than in others the delay of inflation as I was uh describing to him my new picture of the universe inflating regions and so forth expansion I noticed that Alan is beginning to doze

off a little bit actually I I was of course very unhappy about that so I um I thought that I probably should [Music] go one problem with the concept of a Multiverse was that there seemed to be no way to detect it not only is each universe expanding but so is the space in between them and that means that nothing not even light can travel from any of the other universes to reach us physicists did not uh really respond very well to this idea of Eternal inflation once I said that I'm going to tell them

something about uh things beyond our Horizon that uh cannot in principle be observed most of them just lost interest right there Alex valanum thought he was on something big but others were skeptical so Val Lankin reluctantly tried to put his work on internal inflation out of his mind who wants to talk about a universe you're never going to see the Multiverse can't make predictions it can't be tested you could make the case that it's not really science how can you ever be confident of it when you can't see the other parts of the Multiverse we

can only see our little patch our little expanding cloud of gas galaxies uh how are we ever going to know you can't prove the Multiverse exists it's not wrong you can't prove that it doesn't exist so why should we believe it Alex fenin tried to stop thinking about the [Music] Multiverse with no hard evidence to support it the idea seemed to have hit a dead end many people thought that is just not science to talk about things that you can not observe so I did not return to the subject for almost 10 years meanwhile B

Lenin's Russian colleague Andre Lind kept the flame alive he had independently come up with his own version of Eternal inflation but unlike the Lankin he would not be deterred maybe I am a little bit more arrogant when I got the idea for this Multiverse I understood that this may be the most important thing which I ever do in my life and then if somebody doesn't want to hear it that's their problem Lindy published more than a dozen papers but his work would meet an equally chilly reception it seemed no one wanted to hear about the

idea of a [Music] Multiverse if the equations of Eternal inflation were the only Clues pointing to the Multiverse that's where the story might have ended but the Multiverse idea would gain some unexpected support from two completely unrelated areas of science one was an idea called String Theory designed to explain how the universe works at the tiniest scales the other was an astounding discovery made by astronomers exploring the Universe on the largest scale a discovery that's utterly mysterious serious if there's only one universe but if we're part of a Multiverse it's a whole new ball game

it has to do with the expansion of the universe and it's easy to explain using a baseball now if I toss this ball up in the air we all know what will happen as it rises it slows down because of gravity now astronomers knew that the Universe was expanding and the they assume that the expansion would slow down because of the gravitational pull of stars and galaxies just as the ball slows down because of the gravitational pole of the Earth but when they actually did the measurements they found something astonishing something that rocked the foundations

of physics they found that the expansion is not slowing down it's speeding [Music] up it's as if I took this baseball and when I throw it instead of slowing down as it rushes away it speeds up now if you saw a ball do that you'd assume there's some invisible force set counteracting gravity pushing on the ball forcing it to speed away ever more quickly astronomers came to the same conclusion about the universe that some kind of energy in space must be put pushing all the galaxies apart causing the expansion to speed up because we don't

see this energy the astronomers called it dark energy it's among the most important experimental discoveries ever in the history of science it took most of us completely by surprise and so we're still trying to come to grips with that discovering that dark energy is pushing every Galaxy in our universe away from every other other at an accelerating rate was shocking enough but even more surprising was the strength of that dark energy for over a decade scientists have been unable to explain why such a peculiar amount of it exists in empty space but that mystery seems

easier to resolve if we're part of a much larger [Music] Multiverse now the idea that space contains any energ at all sounds strange but our theory of small things like molecules and atoms the theory called quantum mechanics tells us that there's a lot of activity in the microscopic realm activity that can contribute in energy to space and according to the math the amount of energy generated by that microscopic activity is enormous the problem is when astronomers measure the amount of energy that's actually out there the amount of energy required to force the galaxies apart at

the accelerating rate that's observed they get a number like this a decimal point followed by 122 zeros and then a one an incredibly tiny amount very close to zero and nothing at all like what the theory predicted in fact it's trillions and trillions and trillions and trillions of times smaller colossal Miss match we have tried everything to explain why the dark energy is as small as it is we' have tried everything and everything fails hopeless I I once called this the worst failure of an order of magnitude estimate in the history of science does it

bother us absolutely finding that the amount of energy in space is so much less than our theory predicts is not just an academic problem the precise strength of that repulsive gravity well that has profound implications for all of us for example if I were to increase the strength of the Dark Energy just a little bit by erasing four or five of these zeros I still have a tiny number but the universe would be radically different that's because a slightly stronger Dark Energy would push everything apart so fast that stars planets and galaxies would never have

formed and that means we simply would not exist and yet here we are so why is the amount of dark energy so much less than our theory predicts and also just right to allow the formation of galaxies stars planets and life we just don't know the mismatch between the theore itical predictions of dark energy and what astronomers have observed is one of the great Mysteries that science faces today but consider this if we do live in a Multiverse then the mystery of dark energy might not be so mysterious after all in fact if we're part

of a Multiverse the value of dark energy we've measured might actually make total sense hi reservation for green to see how the Multiverse might solve the dark energy puzzle imagine you're checking into a hotel and you get a room number like this 10 million and one hm thanks enjoy your stay 10 million in one would seem like a pretty strange room number and getting a room number like this would be surprising much as the value of dark energy in our universe is a number that scientists have found surprising but here's the thing if this hotel

had a huge number of rooms say billions and billions then getting room number 10 million in one wouldn't be so surprising in a hotel this big you expect to find a room with that [Music] number similarly if we're part of a Multiverse with a huge number of universes each with a different value of the Dark Energy then you'd expect to find one with the value as small as what we've measured if you think of each of these rooms as a universe and each Universe has a different value for the dark energy then most of these

universes won't be hos hitable to Life as We Know It the reason is that the value of the Dark Energy wouldn't allow the formation of galaxies stars and planets universes with much less dark energy than ours would collapse in on themselves and universes with much more dark energy than ours would expand so fast that matter would never have the chance to coales into clumps and form stars and planets so of course we find ourselves in a universe where the vi of the dark energy is hospitable to light otherwise we wouldn't be here to talk about

it so if we're part of a Multiverse the mystery of dark energy becomes not so mysterious but there's a piece of the puzzle missing how do we know if there's enough divver ivity within the Multiverse so that every value for Dark Energy including the strange value we observe in our universe can be found somewhere the answer would emerge from an entirely different area of physics I'm talking about a groundbreaking theory that comes from investigating the Universe on the tiniest scale we know that inside atoms are even tinier bits of matter protons and neutrons which are

made of still smaller particles called quarks but physicists realize that this might not be the end of the line these subatomic bits might actually be made of something even smaller tiny vibrating strands or Loops of energy called strings this set of ideas called String Theory says everything that exists is made of this one one kind of ingredient and just as a single string on a cello can produce many different notes depending on how it vibrates strings can take on different properties depending on how they vibrate creating many kinds of particles from this Theory came the

promise of elegant Simplicity a single Master equation that would explain what we see in the world around us String Theory would be beautiful it would be elegant and calculation from that very simple Theory would produce the world as we know it but for this beautiful Theory to work there was a catch the math of string theory required something that defies common sense a feature that would open the door to the Multiverse extra dimensions of space we're all familiar with three dimensions of space height width and depth but the math of string theory says these aren't

the only Dimensions the mathematics Works only if the strings move and vibrate not just in the three directions that we see but in those and say six more nine space dimensions in all so if string theory is right where are these extra dimensions and why can't we see them think about the cable supporting a traffic light from a distance it looks like a line one-dimensional but if you could shrink down to say the size of an ant you'd find another dimension a circular Dimension that curls around the cable and string theory says that if we

could could shrink down billions of times smaller than that ant we'd find tiny extra Dimensions like this are curled up everywhere in space at every point of space there's extra dimensions of space that are curled up into little tiny knots that you can't see because they're too small and the shape of those extra Dimensions determines the fundamental features of our universe just the way the airst streams that are going through an instrument like a French horn have vibrational patterns that are determined by the shape of the instrument the shape of the extra Dimensions determines how

the little strings vibrate those vibrational patterns determine particle properties so all of the fundamental features of our universe may be determined by the shape of the extra Dimensions the way those extra dimensions of space are put together is in many respects like the the DNA of the universe they determine the way the universe is going to behave just exactly the same way as DNA determines the way a animal is going to look the problem was the more string theorist looked the more ways they found that extra Dimensions could be curled up and the math provided

no clues as to which shape was the right one corresponding to our universe I think the consensus right now is that that number seems to be astronomical there are published papers suggesting upwards of 10 500 that's 10 followed by 500 zeros uh different possible shapes 10 to the 500 different possible shapes for the extra Dimensions each appearing equally valid it seemed Preposterous especially for a theory that was looking for one single Master equation to describe our [Music] universe but then it occurred to some string theorists that perhaps there was a different way to look at

the problem and this different perspective would Breathe new life into the idea of a Multiverse 10 to the 500 different string theories this sounded like a complete disaster what good is it to have a theory that has 10 to the 500 Solutions you can't find anything in there well that left string theorists somewhat unhappy somewhat uh depressed my own reaction to it at the time is this is great this is fantastic this is exactly what the cosmologists are looking for enormous diversity of possibilities don't be unhappy about this this says that string theory fits extremely

well with with cosmology and with all the interesting ideas about multiverses turning what seemed like a vice into a virtue some string theorists became convinced that the multiple Solutions of string theory might each represent a real and very different Universe in other words string theory was describing a Multiverse and an extremely diverse one at that to everyone's surprise string theory was actually quite readily describing huge numbers of different kinds of solutions which Each of which corresponds to a possible universe so we just got this Multiverse for free both from string theory and from inflation you

have these universes that are produced these different universes would all naturally have different amounts of dark energy in fact according to the math the amount of dark energy would spend such a wide range of values from Universe to universe that the strange amount we've measured would surely turn up String Theory without even trying solved that problem so over a decade after lindai and blankin had come up with their ideas about eternal inflation the Multiverse was revived three lines of reasoning were now all all pointing to the same conclusion Eternal inflation dark energy and string theory

just the way it takes three legs to support a stool these three ideas taken together support the argument that we may live in a Multiverse when different lines of research all Converge on one idea that doesn't mean it's right but when all the spokes of the wheeler are pointing at one idea that idea becomes pretty convincing today the Multiverse is hotly debated in the pre the universe many critics remain David Grace is going to tell us no no no but Multiverse Advocates like Alex venin Alan goth and Andre Linde are no longer alone the tide

appears to be turning and now these ideas are accepted to a much larger degree uh Genie is out of the bottle you cannot put it back so what would it be like if we could travel to some of these other universes what would we see some might be vastly different from our own with properties unlike anything we've ever seen in fact some universes in the Multiverse might not have light or matter or anything recognizable at all and there might be other universes with features not unlike the familiar ones we know but where life takes a

completely different form perhaps communicating in ways we'd find utterly bizarre and the math shows that if we were able to visit enough of these universes we might eventually find ones like ours with a Milky Way galaxy a solar system and an earth except with some slight differences in one maybe the asteroid that killed off the dinosaur 65 million years ago missed an evolution started a new course and another there might be an Earth with people similar to us but better at multitasking but there's something even stranger Somewhere Out There we should find exact copies of

our universe with duplicates of everything and [Music] everyone how could this be how could there be exact duplicates of ourselves out there in the Multiverse to see how take this deck of cards it's made up of 52 different cards and if I deal them everyone will get a different hand but over the course of many many rounds eventually some of the combinations will start to repeat that's because with 52 cards there's a limited number of different hands you can deal so if you deal the cards an infinite number of times then repeating hands are inevitable

and in the Multiverse a similar principle applies that's because according to the laws of nature the fundamental ingredients of matter or particles are kind of like a deck of cards in any region of space they can only be arranged in a finite number of different ways so if space is infinite if there are an infinite number of universes then those arrangements are bound to repeat and since each one of us is just a particular arrangement of particles somewhere there's a duplicate of you and me and everyone el else this can be shocking it could be

that in Another Universe I was a rock star and my life is much better or much worse depending on your opinion of rock stars that means all those things that I've never found time to do are maybe being done by some copy of me somewhere else I was rather depressed actually this picture robs us of our uniqueness it is a consequence of the ideas and the ideas seem very well motivated yet critics argue the multi is just too convenient an explanation for things we don't understand like the tiny value of dark energy in our universe

and the huge number of possible shapes for the extra dimensions in string theory problem with that kind of reasoning is that it doesn't explain why dark energy is the way it is it just says it's random chance I don't find that satisfactory you can apply this kind of reasoning anytime you don't have a better explanation [Music] on the other hand supporters of the Multiverse point out that sometimes a better or deeper explanation for the way things are simply does not exist take for example the Earth's orbit around the sun we find ourselves at a distance

of 93 million miles perfect for life if we were much closer to the Sun our planet would be too hot for Life as we know it to exist and if we were much farther from the Sun it would be too cold for life so why are we in this sweet spot well starting in the late 1500s the famous astronomer Johannes Kepler asked that very question and he spent years trying to find a physical reason some law of nature that requires the Earth to be 93 million mil miles from the Sun but Kepler never found it

because it doesn't exist there isn't any physical law requiring the Earth to be 93 million miles from the sun it's simply one possibility of the many you'd expect to find in a universe we know is full of solar systems you might think it was an extraordinary accident it's not it's just that there are a lot of planets out there similarly some suggest that the true explanation for many of the fundamental features of our world will elude us if we don't consider the possibility that we live in a Multiverse clearly if we had a good physical

reason that would be great and we would understand it we'd be much happier we may have to live with that U there's no principle built into the laws of nature that say that the theoretical physicists have to be happy it's a hypothesis it's the leading hypothesis because nobody has another hypothesis which makes as much sense the Multiverse a tantalizing possibility but with no experimental evidence should you believe it we can't believe in anything until there's observational or experimental support but what we have found over the last few centuries is that mathematics provides a shooted Guide

to the nature of things that we haven't yet been able to see observe or experiment with math predicted things like black holes and certain subatomic particles long before we ever observe them and math is suggesting that there may be these other universes that doesn't mean it's right but often it's leading you to a deeper understanding of reality if you choose not to believe it that's perfectly fine because we have not given you any evidence yet and one of the wonderful things about science is it's about evidence it's not about [Music] belief and some scientists now

think we might just be able to find that evidence they propose that if our universe and another were born close together the two might have collided that Collision could have left its own fingerprints ripples in the cosmic background radiation the heat left over from the big bang my guess is yes that in a 100 years we will know one way or another whether these ideas are right 100 years from now it may be an amusing historical episode we don't know but if you only work on the things that are already well established you're not going

to be part of the next big excitement if we do verify the Multiverse it would change our perspective much as Cernic's did 500 years ago when he showed that the Earth is not the center of the cosmos and some might say that if our universe is just one of many our descent from the center would be complete regardless I think it's more important just that we're so lucky that we can understand the Universe I think it's a great ride and I think it's really good for physics that we have this tension I don't know where

I'm going to end up so what does this all mean are there infinite duplicates of you and me and everything existing right now in an infinite number of other universes is the Multiverse the next capern Revolution we don't know at least not yet but if the idea that we live in a Multiverse proves true we be witnessing one of the most exciting and dramatic upheavals to our understanding of the fabric of the cosmos major funding for Nova is provided by David H Coke and discovering new knowledge hhmi and by the Corporation for Public Broadcasting and

by contributions to your PBS station from viewers like you thank you major funding for the fabric of the cosmos is provided by the National Science Foundation where discoveries [Music] begin and the Alfred P Sloan Foundation supporting original research and public understanding of science technology engineering and Mathematics additional funding is provided by the Arthur Vining Davis foundations dedicated to strengthening America's future through education the US Department of Energy's office of Science and the George D Smith fund [Music] [Applause] [Music]