Before the Big Bang 6: Can the Universe Create Itself?

Video Statistics and Information

Video
Captions Word Cloud
Captions
the universe has been expanding for 13.8 billion years but the beginning of that expansion is still shrouded in mystery [Music] in this series we explore competing models for what happened at or even before the Big Bang but whatever the cost was for the universe one can still ask what caused that and what caused that and what caused that is there a way out of this problem is it possible that the universe has no first cause could the universe create itself the very notion may seem outrageous but some scientists have argued that Einstein's theory of general relativity may allow the universe to bootstrap itself into existence one of these scientists is Princeton University's professor Richard Gott grew up in Louisville Kentucky and I got interested in astronomy while I was eight years old and I was very excited about the Big Bang even at that time before had it been proven by Penzias and Wilson discovering the Cosmic Microwave Background and interestingly I got to work with them when I was a graduate student and and got to run the telescope that discovered the microwave background all night and I would occasionally turn it over and look at the moon I'd see the thermal radiation Einstein's theory of general relativity with its curving of space-time leads to a radical revision of how we understand the passage of time time does not have a uniform flow like Newton thought it's variable and depends on how fast you're moving depends on how deep a gravitational well you're living in clocks on the earth tick slower than time clocks at high altitude and so this is important in your GPS satellites they put this general relativity effect in if you didn't put that in your GPS would tell you the wrong location literally I am here but you consider your location as here so we recognize that the notion of here is subjective what relativity tells us is that the notion of now is also subjective the past doesn't disappear when you leave it just like your location doesn't disappear when you leave it this is because the speed of light is the same for all observers speed is simply distance over time and if the speed of light is absolute then distance in time must be relative this leads us to a new view of space and time known as the block the universe time is like a fourth dimension what about now two observers traveling on rocket ships at different speeds in special relativity have different ideas of simultaneity so I say these events are simultaneous the rocket guy has these events are simultaneous it's like you have a loaf of bread I slice it like American bread okay that's one instant that's another instant that's another instant okay the moving astronaut he slices it on a slant like french bread okay and he he those events are simultaneous those events are simultaneous he and I disagree on which event occurred first of distant events and so forth the loaf is the same we can both agree on the loaf this idea of the block universe has been very productive it's given us equals MC squared it's given us all the results of special relativity faster an object travels the slower it's clock will tip travel at the speed of light and time stands still if you could travel faster than light then you move backwards in time it was a young lady called bride who traveled far faster than light she left one day in a relative way and returned on the previous night so there's one trouble with that Einstein showed you in special relativity he couldn't go up build a rocket that would go faster than the speed of light so in 1915 though he invented the theory of general relativity curved space-time so now there's a little pole you can you can beat a light beam by taking a shortcut going through a wormhole or going around a cosmic string in the 1930s when many academics fled Europe due to growing anti-semitism both Einstein and mathematician Kurt girdle found themselves at Princeton the two of them would go for long walks presumably discussing relativity as curved girdle in one of his few contributions to physics found solutions to Einstein's equations that could allow time travel into the past these have become known as closed time light curves many decades later Richard Gott carrying on this Princeton tradition has found other ways to travel into the past these are closed timelike curves it's time travel to the past these are general relativity solutions that are sufficiently twisted that they allow the time traveler to circle back and visit an event in his own past so this started out when I found an exact solution to Einstein's field equations for a cosmic string cosmic string is a is a thin piece of vacuum energy left over from the Big Bang it has a negative pressure along the direction of the string and a positive energy density and this is like when the vacuum decays it's like snow melting and you're left with a few snowman Stan and we're looking for these we haven't found them yet but they're predicted in many theories when the strings move fast enough but still slower than the speed of light but close to the speed of light you could circle them and come back to an event in your own past so this was a time travel solution like a number of time travel solutions in general relativity there was originally kurt gΓΆdel found a rotating universe that had closed time light curves that like this in it and a Kip Thorne and his collaborators Morris and yurt server found time travel solutions with a wormhole just flat space-time time is going this way spaces are going this way and and here's my world line I'm going straight up here toward the future I'm just staying home ok but this spacetime could be twisted around like this so that it's so that my world line always is going toward the future toward the future towards the future and yet circles back and visits the past this is just like what happened when Magellan's crew went west west west around the world and found itself back in europe so if you're a time traveler like this you always going toward the future but like a loop-the-loop on the roller coaster you're finding yourself looping back into the past because space-time is curved so a closed timelike curve can allow time travel to the past but in order to understand how this relates to the universe creating itself one needs to understand the history of the early universe according to most cosmologists the universe underwent an exponentially fast expansion known as inflation this was first described by Alan Guth who we interviewed in Episode four of this series the overall effect is gravitationally repulsive and this explained like how the universe started expansion and also explained how the the microwave background radiation was so uniform because there's a little extra time in there for different regions to get in causal contact but Guth wanted the this vacuum state to decay into normal particles so we'd have a normal expanding Big Bang model and so he wanted this to decay all at once so be in a form and that's like putting on water on the stove and having it just turn into steam all at once but he realized that there was a problem with that and that was that when you actually would do that it would form bubbles of steam just like when you boil water I wrote a paper 1982 saying the answer to this problem was that we lived in one of the bubbles we lived in a bubble universe our universe was one of these bubbles and from inside the bubble everything looked to uniform and so that solved this problem beyond our universe we expect to find other bubble universes and within a very short time after my paper appeared paper by Linda and Albrecht and Steinhardt appeared that had a detailed particle physics scenario to produce this and this was called new inflation and it solved the problems in inflation so this was a geometrical picture of having a a a multiverse so we believe in inflation because it explains so beautifully the fluctuations that we see in the Cosmic Microwave Background Richard Gott is a world expert on relativity to understand the beginning he needed to team up with someone with a similar level of expertise in quantum mechanics I'm sitting my office one day and I get a letter from Chinese student Li Jing Li and he wants to come to Princeton as a for graduate school and he's included a paper that he's written and this is a paper Stephen Hawking had written that there were in a wormhole there would be some sort of affect where the fields would would build up and it would blow blow up Li Jing Li and invented the idea of putting a reflecting ball in between the two wormholes that would deflect these waves and not let them build up like this it was a it was a way to counter Hawking's objection to the wormhole of time machine of Kip Thorne I'd already read this paper it was in the Physical Review I really liked it I felt this was a fantastic paper and I said wow this is a student who would like to come so so I got him to come to Princeton time to come to Princeton and when he arrived we we worked on this time-travel a solution so I'm the general relativity guy and I knew he knew how to do all this fancy quantum mechanics stuff what people do we don't have a quantum theory of gravity but what we do is we we specify a geometry of curved space-time what this model is going to look like and then we apply quantum mechanics in curved space-time this is called the semi classical approach so we just apply this complicated quantum mechanics to figure out what the quantum vacuum state is that would go with this curved space-time the amazing thing about Steven Hawking is that he could do both the general relativity part and invent the quantum mechanics he was the first to do this applied quantum mechanics and curved space-time to do so so he could do both parts here together with the general relativity in quantum mechanics in place got and Lee were ready to present their model of the early universe this is looks like something dr. Seuss would invent this is inflation and Linda said that inflating universes could give birth to other inflating universe by quantum fluctuations this is like branches coming off a tree what lesion Lee and I proposed was that the universe could give birth to a branch like this that's circled back in time like these time loops and gave birth to itself because when you have this model you say well okay I got the branches but where did the trunk come from well a branch could branch off it expands and then becomes the trunk it expands by a factor of 535 so you can think of this as a one-inch branch branching off growing up into a 535 inch trunk that the branch comes off of so there's this so there's this time loop at the beginning and this universe gives birth to itself the great thing about inflation is that a little tiny inflating piece grows up to be an enormous inflating piece each little bit of which is exactly like the little bit that it started with so what if one of those little bits was actually the bit that it started with then it could give birth to itself something funny had to happen at the beginning of the universe and time-travel of solutions and general relativity seemed supremely suited for the purpose this spacetime here where it's a cylinder I've called this groundhog day space-time because it's a flat space-time but it just you just keep repeating the same day like Bill Murray did in that movie you can have what's called a Jin particle this is one that has a circular world line and that person was never born you have a place where your world line starts that's when you're born where it ends that's where you die but this one just goes around in a circle if the universe is in a time loop why doesn't it go around forever how does it get out well this is a this a very good question the the groundhog day universe that's flat space-time and it just curls around the cylinder nothing interesting happens it doesn't get out of the circle okay but we're talking about an inflating universe this is called the sitter space and it's curved so it does break out this is a diagram of the sitter space it's a map of de sitter space and the center spaces is a spherical universe little tiny thing that you saw before with the with the bubble universes and it just gets bigger and bigger so this is the this is the South Pole of the sphere this is the North Pole as you go up here this just makes an expanding gets bigger and bigger and bigger bigger and this is the infinite future here the only thing that's real in here is this region that's colored in because I'm taping this to this and everything else is gone but this opens out you see into a big and flay infinitely large inflating region here in the far future and then you can form your bubble universes there this is a picture where you end up with a time machine at the beginning of the universe that quits and then we have no time travel after that to turn ideas from theoretically plausible to accepted fact they must be empirically tested so how can this be done for the Gotham knee model okay let me give you a humorous answer first okay when they were about to select the new pope I wondered well who might they select like everybody was wondering and so I thought to myself well you know South America is an important area for the Catholic Church that's been growing greatly and so they've gone outside Italy before I think they're gonna go with a South American Pope and if it was a South American Pope well poverty is a big issue in Catholic Church in South America and so the Pope would pick an that would be relevant to that st. Francis you know so I said to my wife I think I'll tweet this the next pope I think is going to be a South American and he's going to name himself Pope Francis okay and she said she always gives me good advice she said oh don't do that you'll make people mad you're not it you're not you know empowered why am i discussing this well there were a couple of guys I think I think they were from MIT as I recall they decided to experimentally test time travel by looking for time travelers among us okay so they looked for a couple of words a couple of phrases on the internet that couldn't possibly have been known ahead of time I imagine if you will that I'd made that tweet and oh here's somebody who said Pope Francis oh my god it's so wonderful oh my lord the serious answer is one of the things about inflation is that it forgets its initial condition its fans but so much is it says forget its initial conditions so it's hard to tell which which one of these different different models would it would have been correct and and and that's a difficulty but you can have what I would call an indirect answer many people today believe that we live in a multiverse with like the many bubble universes why do they believe that well because we believe in inflation because it believes it it does things we can test like the the Cosmic Microwave Background the fact that we're seeing inflation occurring today inflation is testable these early universe models will be tested if we get the string theory to finally produce what we call the theory of everything that we're looking for the important thing about that theory is that as these extra tiny dimensions that are curled up in tiny well inflation tells us that the big spatial dimensions that we see today the three big large spatial dimensions used to they were tiny here all the spatial dimensions are curled up in tiny in the early universe and ours just goes one step further there's a curled up dimension of time here so this seems to fit in very well with super string what super string theory might produce and I think ultimately when we get a theory of quantum gravity there'll be other testable predictions that makes and then you'll look at the solutions of those equations in the early universe and you'll see if you get a model like this Stephen Hawking has put forward the chronology protection conjecture implying that time travel to the past he simply disallowed by the laws of physics otherwise what would prevent you from going back in time and killing one of your grandparents one one wag once said you know you know why the Titanic sank it was because of extra weight of all the time traveler you know people on board you know or another way to say that is if you went back and tried to warn the captain the Titanic iceberg you know he'd ignore you like you ignored all the other iceberg warnings because we know the ship sank it's one four dimensional sculpture it does not change okay so if you went to the past and did something you you you you're already part of history or you're already on the roll call with people around the Titanic so the other solution is the many worlds theory of quantum mechanics this where you have many parallel worlds that are like trains and a train track junction and there's a world where world war two never happened and there's a world where people never landed on the moon and every time you make a decision or you make a measurement and new world branches off so if the time traveller went to the past size grandma killed her he's killed the grandmother in another parallel universe and the parallel the universe were she was born and you lived on two you should give birth to you to your mother into you that that parallel path still exists so there was no paradox so the grandfather paradox has has two separate solutions we don't know which is correct cuz we don't know whether the many worlds theory of quantum mechanics is correct but you do not have to rely on that he's assuming that some law of physics will discover in the future will prevent them okay we don't know of anything that'll prevent them so far in the mid-1960s hawking wrote a very important paper it said let me assume two things let me assume that there are no closed timelike curves and let me assume that gravity is always attractive now let me look at the expansion of the universe that we observe and let me trace that back in time I can prove then that there's a singularity at the beginning they're very effective but you know what by assuming those two things he missed discovering inflation because inflation is gravitationally repulsive we observe dark energy doing this in the universe today hawking didn't know that so that violated the conditions of his thing we have to remember that it is a conjecture and the conjectures don't always have to be right one of the things Hawking says in on television and he knows this as a joke well we're all the time travelers like at the Kennedy assassination you know the idea there is that well if you wait long enough technology will advance enough for them to come back to the present epoch well Hawking knows perfectly well that the time kind of time machines the Kip Thorne and I are proposing there's a time loop that's created up there in the future where you you're moving strings or you're moving wormhole mouths up in the year 3000 and the there's a Koshi arisin where the time travel starts okay and before that there wasn't any time travel so if you create a time loop let's say in the year 3000 you may use it to go from three thousand and two back two three thousand and one but you can't use it to come back here the laws of physics seem to be time reversible at a fundamental level and yet we see a definite arrow of time we remember the past but we never remember the future we would easily notice if a film of a clock face was running backwards but it's not so easy with a film of a pendulum the laws of physics seem to be like the pendulum whereas our experience is more like the clock faced with the definite arrow of time so an ideal feature of a cosmological model would be to explain how this arrow of time emerges an unexpected property that we found about our model we didn't build it into it at all is that it gives you a natural arrow of time here's a close-up picture of space-time this time goes this way here's a here's a particle and electron let's say I shake it here electromagnetic waves go out toward the future I mean they would get to Alpha Centauri I was four light-years away they get to it four years later and the people on Alpha Centauri would see this signalling we'd sent them we observe this we do not observe this this is called an advanced wave and when we shake a charge we do not observe electromagnetic radiation going off to the past that would look to us like every time you shook a charge before that you saw electromagnetic waves coming toward it this is the right time and then it would then it would do this we know that electromagnetism is a theory that is time symmetric general relativity is a theory that is time symmetric so why do we only see this solution and not this solution okay well in our model there's a very easy and interesting answer to this if I may send a photon out here toward the future it just it just goes out on toward the future harmless okay no trouble but if it goes toward the past it goes down in here goes down in here circle this time loop notice that the universe is contracting the way it's seen this causes it to blue shift this causes it to become more and more energetic and more and more energy circles this an infinite number of times and it creates an infinite energy density it blows the thing up okay that's not the geometry you started with that would change the curvature of but that would be a different curvature of space-time than you had so that would be like killing your grandmother that's a that's what would what would happen here that's not a self-consistent solution of this geometry notice what happened if you go the other way around though let's say I had a photon that was going around this way or a graviton that was going around this way um it would go around here and every time it circles the universe is expanded by a factor of 535 it's been red shifted by a factor stretched by a factor of 535 it's lost energy by a factor of 535 every time it goes around it loses another factor of 535 in energy it could circle an infinite number of times and leave you with a convergent answer one plus one over 500 and plus one over 500 squared plus one over 500 cubed that sums up to a finite number in here in the time loop region the temperature is cold it's absolute zero in here there's no thought you don't see any thermal radiation if you lived here if if you would put a detector in here you would see it's absolutely cold this is a low entropy state and here once you cross this boundary you start to see the fact that you have a vender aizen's you can't see those other you know funnels and those other universes and so you emerge out here and it heats up and you see the Hawking radiation due to the event horizons that you're saying so the time you here you're seeing a hot that's heat that's thermal radiation consistent with this de sitter space that you would expect okay so it's going from cold initial conditions to hot initial conditions and that's an increase in entropy so this time loop is a low entropy loop because of its geometry and and that's giving the universe low entropy initial conditions this is what you need to have the entropy arrow of time always run downhill from there once you start out with it just rolls downhill so we get an entropy arrow of time automatically and we get a a causal arrow of time that that you shake something here and then later this effect occurs this normal causality we're getting with these retarded potentials we get these two things for free from this model recently physicist Aaron Wall has claimed that thermodynamics might spell trouble for closed timelike curves this is a picture diagram from from him and this is the wormhole that's being Illustrated here you got a wormhole mouth over here and you got another wormhole mouth over here and they're not synchronized so this line is a closed timelike curve where the guy comes along here and then disappears into this wormhole mouth and immediately appears back here so this is a Jin particle this is one that has a closed timelike curve what he noticed was that this time traveller here is not going to see a light signal it's coming along like this he sort of see trapped in the past and can't never this light signal never going to get to him so there's a there's a horizon here there's a kosher horizon here that that but but to him it's an event horizon seen from the inside this traps the region of time like curves he can't he can't see anything beyond this over here just like you can't see events that are occurring inside a black hole the regular time traveler what they would do would be they come all across here they come into this mouth they come out of this mouth they'd say hello to themselves then go on here to the future so that's not true for them but it is true for somebody that's trapped in one of these closed timelike curves now event horizons have a certain entropy associated with a certain amount of disorder that's that's proportional to the area of the event horizon so what he noticed was this area of this event horizon is shrinking that looks like a decrease of entropy and that would violate the second law of thermodynamics this is his point now the interesting answer to this is as far as our model is concerned when we go back to this picture right here here is the person on the closed timelike curve here here is this event horizon this person can never see past okay it includes the region of closed timelike curves here and so now that looks like it's contracting doesn't it so it looks like mr. wall is right but this is a curved space-time you got to remember that the scale is d is decreasing is where it's being shown it's smaller scale here so the truth is in this in this de sitter space this is not decreasing in area at all it's like a cylinder instead of a cone in fact if this person were living in regular de sitter space it wasn't multiple-- connected his world line would continue on up here on a bier to infinity and this would be the event horizon that he would have and that's a fixed constant radius in the sitter space so mr. walz argument interestingly does not apply to ours he would say ours doesn't violate the second law of thermodynamics I've said for many years and it's in this book the welcome to the universe so that did with Neil Tyson and Michael Strauss I've said about Jim particles well it's more probable for you to find like an electron that's a jinn then you find something complicated like you know Leonard Nimoy playing Spock as a Jan and those those happen in probably which of course with statistical mechanics you can have a violation of the second law rarely in modern physics empty space can still have energy this leads to different states of the vacuum a Minkowski vacuum is associated with flat space-time a Rindler vacuum with accelerated motion William hiss has argued that the vacuum state implied in closed timelike curves is unstable and therefore rules out who got any model um let's go back to Groundhog Day imagine this is Minkowski space it's flat space-time and that has a vacuum called the Minkowski vacuum and it's zero energy density and zero pressure is perfectly well behaved okay now now if you wrap this up to make the Groundhog Day you get what we call a wrapped or what I would call a wrapped Minkowski vacuum it's the same as a Minkowski vacuum here but everything you do here there's an image of it at beer and there's multiple images of this so you can you can calculate the effects of this and and you find out that when you wrap this like this you get you get an extra vacuum which is like it has a positive energy density and a positive pressure okay it's small so you can ignore it but the in the case where you have a closed timelike curves if you look with a microscope but where the coachee horizon is occurring where the where the closed timelike curves and and the region without closed timelike curves begins you can see that generically this looks like a little piece of what we call Misner space and this is a space that looks like the groundhog day only instead of being a cylinder it looks more like a megaphone it gets narrower as you go over here and so you can wrap yourself around this and round this around this you go out to the short end and boom you're out you're into a region of non-time closed timelike curves and that's where the Cauchy horizon occurs so as this gets narrower this effect of of having this extra looks like therm it's it's light thermal radiation it gets bigger and bigger and it blows up when you when you're when you're leaving the space so his had been one of the people that that had calculated this originally and it was one of the reasons people thought that that crossing that Koshi horizon the quantum vacuum state might blow up okay so this is one of the problems that we were that we were addressing so solely jingly came in to me one day and he says I found the answer okay he said the man kept the the Minkowski vacuum is the wrong one to use it's really a Rindler vacuum an accelerated vacuum that's that's that's wrapped around this megaphone the Rindler vacuum has a negative energy density and a negative pressure intrinsically and when you wrap it you get the positive energy density and the positive pressure the two cancel out and you give you zero so it's flat space-time what you want that's the geometry you started with and as it goes over here both effects get bigger and bigger but they cancel out exactly meanwhile Hawking's student Michael J Cassidy had figured out the same thing from using a Euclidian analogy this you change one of the space-time has has three dimensions of space and one to time if you multiply the time by the imaginary number I Stephen Hawking has talked about this you can change time into Euclidean dimension and so this is Euclid is four dimensions of space no time you can work your quantum mechanics in this four dimensional Euclidean space and gives the same must give the same results as terms of calculating the energy density as you would get if you did it in the regular space-time here's what Cassidy discovered he discovered that this this Misner space like the megaphone with the closed timelike curves was just flat Euclidean four-dimensional space-time with polar coordinates where the two of the direction so like a longitude so one of your coordinates was a longitude that went around in a circle and if and you'd say well there's longitude there's there's a distance out from the center if you made that coordinate your time I multiplied it by the imaginary number huh then then what would happen would be that you would get Misner space here with the closed timelike curves and since this Euclidean space was the analog of regular space-time with zero energy density the mr. space must have zero energy density - so mr. Cassidy understood that Misner space must have a vacuum state that had zero energy density he just didn't know what it was but he knew it must exist and Li Zheng Li had already found the correct vacuum state it was a wrapped Rindler vacuum that gave you zero energy density so Cassidy's paper came out first and he got it and Hawking agreed that this must be true now now one of his Cox criticism he's he's my brother you know we both discovered the the exact metric for around the cosmic strength this he complained that when he did not just a simple scalar field which Li Jing Li had done but more complicated feels like a self interacting field or a massive scalar field that he found that it blew up and the reason he the reason he found it blew up was he was still using it when he renormalized it he was he was subtracting off Minkowski vacuum and that was incorrect when you plugged into the correct way of transporting it to Hiscox results all the terms canceled out beautifully and it gave zero so the the correct self consistent vacuum for Misner space is the wrapped Rindler vacuum and it does not blow up at the cause your isin it does not prevent you from crossing through there and entering the time machine or leaving the time machine and that's true of our model of the early universe as well another criticism of a model is that it requires delicate fine-tuning as the time loop would have to have a very specific length to make it work it's sort of like asking the question well why if you go to the North Pole and look at the longitude why does the longitude always add up to 360 degrees well if you perturbed it slightly Jesus has lots of perturbations there's mountain ranges things like that it's easy to perturb the earth but the longitude is always 360 degrees so the this this time loop would be of that length in two of our recent films we tackled the bizarre idea that in a multiverse random fluctuations of conscious brains would outnumber normal observers if this is the case then the multiverse would be an untenable proposal Alan Guth and Thomas fer tog gave several reasons why this idea is flawed richard gott has another we see dark energy in the universe today with a positive energy density and a negative pressure this is going to keep doubling and doubling in size it will approximate de sitter space which we've been talking about that's the same as the inflationary beginning of the universe only this is going in sort of slow motion if you look at that long enough and we're talking about 10 to the 10 to the 70 years you will see something strange a Boltzmann brain will appear it's like monkeys typing typewriter you know eventually you get Shakespeare's play it expands forever and so if it goes on forever there should be an infinite number of these Boltzmann brains in the future of our little patch of the universe if most of the intelligent observers in the universe are Boltzmann brains why am I not one of them the Boltzmann brains are always disappearing you know they're just a fluke you know and so you know I know that I'm not a Boltzmann brain because if you ask if you're in a conversation with a Boltzmann brain and it answers ten questions correctly we're giving it the Turing test to see whether it's an intelligent observer so I'm asking it questions I'm seeing if it's behaving like a human and so it answers ten questions correctly that's highly unlikely they disappear like that okay they appear and they disappear later they're noise on your on your TV screen let me count to ten one two three four five six seven eight nine ten Boltzmann brain can't do that if you see one that can count up to five it's quite of all the ones that can count up to five greatly outnumber the ones that can count up to six you're seeing photons from them it's highly likely when you see the Boltzmann brain it waves and says hello that you're just seeing photons there's no Boltzmann brains there you're just seeing photons that look like a Boltzmann brain these are dredged out of the vacuum by you as the observer okay and how do you know this well because if passing here's you you're passing through the same event is another rocket ship that's going at high speed with respect to you he has a different set of event horizons than you do and he sees different Hawking photons than you do he dredges different Hawking photons how did that same Gibbons and Hawking vacuum so you're likely to see a Boltzmann brain that's at rest with respect to you one going at high speed would be even more improbable because it would have more mass energy associated with it so if you say I see a Boltzmann brain the rocket ship passing right by you says I don't see anything they're not real those Boltzmann brains aren't real what's real is the photons that you actually detect you could see one but you're unlikely to be one so they don't bother me and there been other people have also put forward solutions like you're killed when the bubble collides with you before you can see a brain so and you should only concentrate on what you can see and I had a conversation with Paul Davies is one of the pioneers of calculating the the the vacuum state for the sitter space I had a conversation with him he says I exactly agree with you the only photons are real are the ones that you've detected quantum entanglement is a strange phenomenon that allows pairs of particles to interact instantly as if they are one system the problem is that there seems to be no limit to the distance at which this can be achieved how this is squared with relativities restriction on faster than light travel is not clear but a new way to understand entanglement may make time travel solutions more viable recently maldacena and Susskind have written a very interesting paper where they say that quantum entangled particles are seem to be may be connected with a wormhole now these are not ones with closed timelike curves in them that they're talking about but it sort of opens the door to think about easier ways to make wormholes into time machines some people have complained that the Hawking radiation there's a particle that's emitted and there's one that falls into the horizon and that astronaut going in might be burnt up by the Hawking photons on the inside of the horizon of so-called firewall and they showed that this this entanglement business meant that that vacuum didn't blow up and and you you could get inside the black hole so it's a very interesting paper and I think it it it makes it a little easier to realize some of these time machines one of the most important concepts in quantum physics is the uncertainty principle which states that there's a fundamental limit as to how accurately we can specify certain quantities and physics a theory of the early universe will likely need to unify these quantum concepts with relativity but richard gott claims that closed timelike curves would be an inevitable result of combining the two theories so why does he suggest this the measurements of time and space become uncertain the time interval between two events becomes uncertain and the spatial separation between two events becomes uncertain by the uncertainty principle so closed timelike curves would naturally seem to occur this is called space-time foam and it's multiply connected like we want multiply connected with all sorts of bridges going different places in time in different places in space it's always pictured as a as a sponge you know this is this is how space-time looks at that microscopic scale so that's why I said another model that takes advantage of quantum uncertainty is Ville incants tunneling from nothing where space and time tunnel into existence from a state of no space and time this tiny patch of space-time may have its negative gravitational energy balance it's positive mass energy and so could exist forever inflating into the universe than we see today tunneling quantum tunneling by definition has two ends there's a clap there has to be a classical solution here over on the other side if you're just coming from a mountain here you get a singularity that's what we're trying to avoid we think that in quantum gravity you don't get singularities quantum effects always smooth out a singularity so if you if you want no singularity or you've got to have a classical solution on the other side so he really needs that point like universe on the other side Li Jing Li and I were saying the universe isn't made out of nothing it's made out of something a little tiny piece of itself and you can do this with a with a closed timelike loop with a little time machine at the beginning so this is Ville Incans model Stephen Hawking has a model that looks exactly like this and same thing going on but but Hawking commented that the South Pole of this that point at the beginning is not really any different from the other point so you've just got a sort of boundary there and the universe is starting off with a boundary here space-time ends here and there's this little Euclidean section that's on the that's on the bottom these are both sculptures four dimensional sculptures that are just sitting there okay but they have causal things going on in them microscopically if you look at it you can see world lines of photons intersecting thing's shaking charges things like this and so um locally this model has a boundary at the bottom in our model has a periodic boundary condition at the bottom our model has has the property that every event has events that are preceding it ok mr. Diaz who compared these two models so they were quite complementary and he had analyzed the stability of our model our model is stable because if you sent a gravity wave around here it would just keep losing energy as it went around it would make a finite perturbation it wouldn't wouldn't disturb things so this is stable and he said it was quantum mechanically stable as well if this loop were small enough so he commented that these two were quite complementary it brings forward the idea that maybe if you looked at the final quantum theory of gravity these two models actually might look the same because time and space get confused when you get into the into the early days here but but our says space-time here and every event has events that preceded it that we would say were causing that things to occur there so it's sort of like this I'm sitting on this chair if you came along and sat on my knees what's holding you up well my knees someone else could sit on your knees there be a line of people but it's all held up by the chair and this is the usual case you've got a boundary condition at the beginning of the universe but suppose you sat on my knees and then people sat around in a circle and then we removed the chair and then the person I'm sitting on someone else's knees we're all sitting on sometimes knees so this is what the closed timelike loop is like you get the normal causality locally that we're used to seeing and local effects are important general relativity as local energy conservation it doesn't have global energy conservation ours is a finite past but it has no earliest event a universe with causes that no first cause may seem counterintuitive but our intuitions are based on our experience of time what general relativity tells us is that time can behave in ways that are very different from our experience especially when space-time curvature becomes significantly large thought and we have shown that this may be the key to explaining the mystery of our cosmic origins [Music]
Info
Channel: skydivephil
Views: 998,600
Rating: 4.5477977 out of 5
Keywords: cosmology, time travel, relativity, physics, science, astronomy, richard gott, stephen hawking, roger penrose, inflation, mulitverse, multiverse theory, cosmic microwave background, big bang, big bang theory, brian cox, neil degrasse tyson, string theory, parallel universes, universe, cosmos, before the big bang, closed timelike curves, boltzman brains, william lane craig, lawrence krauss, richard dawkings, creation, atheist, athesim, god, debate god, evolution, nasa, esa
Id: 79LciHWV4Qs
Channel Id: undefined
Length: 52min 26sec (3146 seconds)
Published: Fri Dec 29 2017
Reddit Comments

Simple analogy for this video... if no then no. If no then yes and if yes then infinity. Expansion! Bang! Universe gives birth to istelf every time.

πŸ‘οΈŽ︎ 8 πŸ‘€οΈŽ︎ u/TateDeanIsMean_16 πŸ“…οΈŽ︎ Mar 26 2019 πŸ—«︎ replies

Hahahaha I love this guy. He’s really enthusiastic.

πŸ‘οΈŽ︎ 6 πŸ‘€οΈŽ︎ u/NerdBrenden πŸ“…οΈŽ︎ Mar 26 2019 πŸ—«︎ replies

It looks like it would probably play DEC<CG second c one octave lower

πŸ‘οΈŽ︎ 2 πŸ‘€οΈŽ︎ u/Pumbaathebigpig πŸ“…οΈŽ︎ Mar 27 2019 πŸ—«︎ replies

Honestly was hoping it would be how to turn a sphere inside out part 3

πŸ‘οΈŽ︎ 1 πŸ‘€οΈŽ︎ u/LucianoLuckyHands πŸ“…οΈŽ︎ Mar 26 2019 πŸ—«︎ replies

Isnt it obvious that it created itself? Like no one else started big bang it exploded by itself.

πŸ‘οΈŽ︎ 1 πŸ‘€οΈŽ︎ u/Olasg πŸ“…οΈŽ︎ Mar 27 2019 πŸ—«︎ replies
Related Videos
Note
Please note that this website is currently a work in progress! Lots of interesting data and statistics to come.