Starship Congress 2017: Miguel Alcubierre, "Faster Than The Speed Of Light"

[Music] all right I don't know that the the next speaker I don't know that I can do the appropriate introduction really because when we were talking we became I think we became a gauge so because of politics I mean like we started yeah yeah and then and then for seems like a couple years we've been engaging in Twitter and then having a conversation then I asked this year I said Miguel if I ask you to attend starship congress would you be how would you be okay with that he's like yes you may ask me like excitement level came out like here and I said Miguel Cuvier we can be erhu you please a tent would you consider attending and speaking as stars of Congress 2017 and when he said yes I was like okay I'm a fan boys I'm like and Andre said what so Miguel could be here of course wrote a paper 94 I bought drive and introduced the concept of a working warp drive to the world and since then he you were a where you post grad PhD student when he wrote that paper and then had famed thrust upon him so since that time that the paper has has withstood the test of time has become the the it's the we now refer to warp drives as a Cuvier drives in fact it's permeated pop culture so much that in interstellar the movie was written around it the Scot man leaves in the back who plays Kerbal space program his one of his most popular episodes is the Kerbal space program video using the UH Cuvier drive this is Miguel a Cuvier thank thanks thank you well before I start I'm just gonna tell you a little bit of our way what actually do for a living you've heard about my wardrobe paper but I was only one paper written in 1994 and I haven't been back to that subject since okay so just to let you know what I really do normally I'm not going to talk about that today but I study black holes in gravitational waves that's really what I do I'm an an astrophysicist not so much as you I'm sort of in the boundary because I'm I do a general relativity which is not so much on the line of astrophysics and I do gravitational wave so this is my gravitational wave tie if you saw the discovery of gravitational waves a year ago this is the signal well today I'm going to talk to you about how to travel faster than the speed of light what what are the possibilities why we think it might be possible and why why people think it's not possible as well because that's important so I'm going to talk about physics initially this is the one so you've heard it everybody knows it in principle you cannot travel faster than the speed of light we know that since 1905 with a special theory of relativity relativity is now an integral part of our understanding of the universe is one of the two pillars of modern physics relativity and quantum physics that's the whole modern physics there light is really fast you know that it's so fast and in everyday life we don't really care about it but the universe and I don't need to tell you that here it's really big so if you want to get anywhere and you can't reach the speed of light then have a long wait it's even a problem in our sorry this jumps really fast okay it's even a problem in our own solar system because this is already large enough that it takes hours for signals to get to another planet it takes eight minutes for the light of the Sun to reach us it takes several minutes to reach Marsh when it's on the same side of the Sun are if it's on the other side of the Sun it takes about half an hour or signal to reach Mars so if you want to control curiosity you have to tell it a long time in advance what to do because you cannot control it in real-time because of the limit of the speed of light even worse if you go to the outer planets so why white can't we travel faster than light so I'm gonna give you a crash course in relativity in the next ten minutes just some of the details of relativity it's not because Einstein said so okay that's not how science works it's not a principle of authority is because of the laws of the universe so what is relativity it's interesting maybe you don't know the idea of relativity is not an Einstein it comes from Galileo it wasn't called exactly that but the idea relativity is really simple movement is relative speeds are relative you how do you have to say you're moving with respect to something the first one to thought about this was Galileo he made a thought experiment he was thinking you're in a ship at sea in a room with no windows far away from the continent and the question is can you do any experiment in that ship that tells you if the ship is moving with respect to distant land or if it's still with respect to distant land and the answer is you can't there's absolutely no way to know within the ship if it's moving with respect to land okay that's relativity okay there is no absolute speed speed is relative the laws of physics are independent of the speed of the observer they are the same so this comes from Galileo and of course it's perfectly satisfied by Newton's physics okay Newton also knew about this and it's satisfied by Newton's physics so what happened what happened between Galileo and Einstein that meant made Einstein so important what happened this electromagnetism okay and in the 19th century we discovered the loss of electromagnetism people like farad Rin Gauss and unpair and Maxwell was there this is natural and but the problem with the loss of electromagnetism is that they seem to violate the idea that motion is relative they seem to violate their principle of relativity of Galileo and that was a big problem for example you've probably heard that a moving charge produces a magnetic field an electric current produces a magnetic field so if you have an electron that's moving it produces a magnetic field but who decides if it's moving that's all your motion is relative so if I move with you're with the electron then the electron is addressed with respect to me then there shouldn't be a magnetic field it's a question is there a magnetic field the reason there that's a problem okay the magnetic force on a particle depends on its speed who measures that speed the speed of electromagnetic waves is actually the speed of light because light is an electromagnetic well beautifully call it see it comes out of the equations independently of any reference frame so again who measures that speed with respect to whom it's supposed to be measured all those things were it's physicists at the end of the 19th century it these things apparently violated the relativity of motion and people like Wonka Ray and Lawrence were really worried and we're really thinking about these things in the last decade of the 19th century and we're trying to find a way to understand this they even invented something that we call the ether that now we don't believe and even worse experiments showed that the speed of light in the laboratory was completely independent of the motion of the earth now the earth moves very slow compared to the light that's true but you can measure it the apparatus at the end of the 19th century we're already good enough that you should be able to measure the effect on the speed of light due to the rotation of the earth around the Sun and they couldn't measure anything we came out zero that didn't make any sense so that's why I'm sign is important my ascent appeared in 1905 by the way this is the Einstein of 1905 it's not the old guy you'll remember is the young guy he was 26 and he tried to reconcile Galileo's principle of relativity with electromagnetism actually his paper on relativity is called on the electrodynamics of moving objects it's a paper about electromagnetism and he says okay let's assume that Galileo is right motion is real the laws of physics are absolute independent of the speed of observers but let's assume something else that the speed of light is also absolute this is strange it sounds contradictory because this principle number one tells you speeds are relative number two tells you weight one speed is absolute okay it seems that it doesn't make any sense it actually does he figured out that there is one mathematical solution that allows for that you can have one you can say all speeds are relative except one that works and that one is the speed of light so we did the math and out came relativity own relativity theory came out of those two postulates so modern theory of relativity is a theory that tells you speeds are relative but there's one there isn't the speed of light is not relative it's always the same it doesn't matter how you measure it the speed of light is the same independently of the speed of the source of light independently of the speed of the observer who measures the speed of light it's the same number always which doesn't make any sense because if you take Newtonian physics you can show that speeds add up you can add speed it's okay they're additive but the speed of light is always the same tells you that you know you cannot if you add anything to the speed of light it remains always the same so something is wrong so an in theory you showed that they add up just because of your definition of space and time so if they should be additive by your definition of space and time and there's one speed that violates that there's only one possible conclusion your definition of space and time is wrong what you thought of space and time is wrong you need to rethink space and time okay so that's the whole content of the theory of relativity space time are not what Newton saw space and time are something different so that's how it gets boring now there's a lot of interesting things Einstein showed really quickly now that's one one other thing if I go there it's called the theory of relativity right but it's based on two things that are not relative it says the loss of physics are absolute the speed of light is absolute why don't we call it the theory of relativity if it's based in two things that are actually absolute well we call it the theory of relativity because other things come out to be relative the price you pay for taking the speed of light to be absolute is that other things we thought we thought were absolute are actually relative flow at time is relative you have time dilation distance is a relative you have contraction of distances when you move very fast similar 1080 is relative this is crucial I want to come back to that one mass and energy are equivalent that also comes out of it that actually came in the second paper the famous equation e equals mc-squared and of course nothing can travel faster than the speed of light this all comes out of relativity okay all of modern physics is based on special relativity all of modern physics if you say if you violate special relativity the whole building of modern physics physics collapses okay so and we've checked this and rejected and we've done thousands and thousands of experiments in the last 100 years and it's never failed okay so it's not just a theory okay we've checked and rechecked now 1908 something interesting happened this guy here Minkowski who was a mathematician he was actually a science teacher at the university discovered something really crucial this is a quote from him from his paper he says hand sport space by itself on time by itself are doomed to fade away into mere shadows and only a kind of union of the two will preserve and independent reality and what he meant is something that I put the equation there don't worry too much about it but what he discovered is what that Einstein's special relativity could be recast as a theory of geometry but a theory of geometry in four dimensions not in three four dimensions being the three spatial dimensions we know and time time is a fourth dimension and he discovered that everything that Einstein had proven could be understood by thinking that in four-dimensional space-time there was a measure of distance that was absolute okay so if you remember when I was theorem so the square of the size of the triangle is equal to the square of the height well it works also in 3d in 3d you can have the distance when it's between any two points in 3d you can decompose it in the distances in three dimensions square it and then that gives you the total distance squared well it also works in four dimensions except that there's a weird funny sign here the four dimension comes with a minus which is a very strange form of the Pythagoras theorem in plus plus plus minus but that gives you a measure of distance in four dimensions and it's absolute it's absolute everyone will measure the same thing it doesn't matter how fast you move it doesn't matter what you do it always comes to the same number there is a measure of distance in space and time that is absolute we call it the interval or the line element or many other names we don't like to call it distance because of this - these words this is Frank okay what it works so this geometry in four dimensions space is relative time is relative but space time is not relative space time is absolute space time has an absolute business this is the great discovery of Minkowski in 1908 and everything Einstein said before can be shown to come from this this is the basis of special relativity so special relativity is a theory of space-time in which you have a distance in space-time that works sort of like the high-poverty remover the - in here okay so this is the great discovery initially I didn't like this I'm Stein thought this was very abstract and he thought Minkowski is crazy what he's saying is probably true but is very abstract then he changed his mind okay quickly now what is implying this implies that there's something very important in space-time this - is crucial it tells you that in space-time there's an absolute structure and that absolute structure actually has to do with causality okay causality is the fundamental property of space and time and this can be illustrated by something we call the light cone you manage imagine you have an event here something is plot for example a big supernova explosion then you make a diagram in space on time time goes up space goes like this and then you plot in this diagram light rays light rays move for example the right and to the future and they move along this trajectory and to the other side and backwards in time and this gives you a count okay I count to the future we call that the line daylight count the light cone is all those events that can be reached from a given event at the speed of light okay to the future or to the past that's called the light Coney and know everything our travels slower than light moves inside the light cone this is light and if you want to move outside the light cone you have to travel faster than light since the speed of light is absolute the light count is also absolute every observer no matter how fast he moves has the same will agree with the light cone okay so was the same one oh sorry this just really fast now another thing you find is that observers that move respect to each other do not agree and which events happen at the same time as I mentioned before simultaneity is relative if I say two things happen one over there and one over there and they happen exactly at 12 o'clock somebody that's moving with respect to me very fast well saying that's not sure what happened before the other and happen after and somebody moving in the opposite direction would see them the other way around which is really nice okay simultaneity is not absolute we cannot agree on things that happen exactly at the same time that's one of consequence of relativity but they always agree on the light come now this is a problem this is a problem okay so Benjamin here if imagine two events one here the explosion and another event in the future say somebody explodes over there there's a brick lined in my direction and it hits me here and it kills me okay so this is clearly the consequence of that it exploded it killed me yes does cause and effect I know that a happened before B okay and everybody has to agree that a happened before B they move very fast they have to agree okay well what happens if I have events like here a and B they happened exactly at the same time a a and B happened at the same time simultaneous okay some of that moves for it with respect to me will say no that's not true a happened before B and somebody that moves in the other way will say that's not true P happen before a now this is complicated because if he thinks a happened before B he might be able to say well then a Myka might cause B but this guy saw it the other way around he said no no it can't cause B because b happened before a so it doesn't work okay so if things though if you don't agree in simultaneity then you have a serious problem you might break causality if you can't agree in the order of events in time which one happened before there's a risk of destroying causality there's only one way out the way out is to say that nothing can travel faster than light you use the light cone the light cone is the only thing that's absolute so you say Kosala t is always contained within the light cone okay this is a solution Lancope the light cone defines causality different observers do not agree on the time order of events that are outside the light cone but they always agree on the order of events inside the light cone because the light cone is absolute and as a consequent consequence if any object to travel faster than light that is outside the light cone then it would violate causality because if I move from here to here faster than light then there's some very reasonable observer that would actually see me arrive before before I ever left which makes no sense destroys causality okay traveling faster than light destroys causality traveling faster than light allows us to travel back in time which makes no sense so that's why we can't do it I think faster than light travel violates cross salad faster than light travel with allow you to travel back into the past which is why it's forbidden it's not because Einstein says so it's not because we don't have the technology is because it destroys causality and we don't like salad to be in destroying we haven't never even seen it nothing has haven't traveled faster than light in our universes or we can see there's no experiment that has shown anything fast traveling faster than light or seems to work this seems to really represent our universe okay so that explains why okay it's not because Einstein said so it's not a problem with technology it's not a problem with ideas no no it's a problem in the way our universe is built okay so we can always travel faster than sound people said oh you couldn't travel faster than sound and you can but that was just technological problem things have traveled faster than sound forever we've been able to move objects faster than sound but at least 500 years they're called bullets they travel faster than sound the problem was to build an airplane that's a engineering problem we cannot travel faster than light not because of an engineering a problem is because of the way the universe is built okay it's because of the basic properties of the structure of the universe is because of minkowski's distance so that was the situation and that's it then I would finish the talk here something else happened in 1915 a second huge contribution by Einstein i shouldn'ta served at least three novel prices I think he only got one and he only got it for something that's nothing to do with relativity it comes from quantum theory 1915 he did something else he actually discovered it really early on we have a theory of gravity we already had a theory of gravity since Newton at universal gravitation which was pretty well okay we still use Newton's theory to send probes to Mars and Jupiter we don't need relativity we use it to it with Newton's theory but there was a big problem with Newton's theory according to Newton's theory the speed of gravity is simple it gravitates instantaneous speed of symphony okay that's a problem that was even a problem Newton style people complained about that Newton they told him this action at the distance doesn't make any sense and he said I know it doesn't make any sense if you have a better idea tell me and of course nobody did nobody had a better idea for 300 years but but he knew it was a problem but it became a serious problem with Einstein because if gravity travels at an infinite speed it violates relativity I just told you nothing travels faster than life not even gravity so if gravity travels faster than light then it's wrong Newton's theory of gravity is wrong so Einstein dedicated the next 10 years of his life to find a new theory of gravity that would not violate relativity it turned out to be an extremely complicated theory it took much longer than he thought but he eventually found it he was guided by a nice thing and I'm gonna divert myself a little bit here I'm gonna take some time he used a very beautiful idea that also comes back to Galileo it's called the principle of equivalence he actually called it at one point the happiest thought of his life actually the best idea he ever had it's called the principle of equivalence and this the observation of Galileo is that if you have gravity and you let objects fall they always fall with the same acceleration go to the roof of the building and to throw a little pebble and a big ball of metal they fall at the same rate it's not true that the heaviest one falls faster they fall at the same rate this was discovered by Galileo but Einstein turned it round understand said okay this is this is the key property of gravity and he postulated like this the laws of physics in free fall when you let yourself fall are identical to those in the absence of gravity if you let yourself fall gravity disappears so this is Einsteins contribution it comes from an observation of Galileo and he used that to build his theory it took him still another eight years as you can see but and this is by the way the reason why astronauts floats in space if they ask you why do astronauts float in space and you answer because there's no gravity there you're wrong there is gravity there the International Space Station is only about 400 kilometres up which is nothing compared to the size of the planet so of course there is gravity there is about 95% as in tenses here it's almost the same as here but they float why do they float you know the answer they're falling exactly they float because they're falling they're falling around the earth all the time they're always falling and if you fall if you fall then there's no gravity okay so you float because of the principle of equivalence you can absolutely do it on earth you don't have to go to space you can go in these beautiful planes that go up in a parabola and then let themselves fall down and freefall and then you float the difference is if you go to space you can float for months and if you do it in an airplane you can only do it for about 30 seconds before you crash into the ground so but you can do it the skull parabolic flight is how they train astronauts and I was lucky enough thanks to a few friends one of them was sitting way up there who say we're crazy enough to take us to Russia and one of these planes this is a movie can you click it and click the play that's me you can see us float that's another friend of ours there's another friend cuz there was somewhere in the back he's not in this hay but but he was there in the same flight on the same plane so I show it to you because I think this is the closest I'll ever get to space myself okay this is this is the principle of equivalence if you let yourself fall gravity disappears okay Einstein took this idea and he used it to build a new theory of gravity this new theory of gravity is general called general relativity and what he discovered is that he could use this idea of Minkowski that relativity was geometry but he needed to change the geometry so we needed to make space-time curved okay so basically that comes from the principle of Coulomb's I'm not gonna get into any detail but the theory of real general relativity it's it's called general relativity because it takes the theory of relativity of Minkowski and his space-time and it generalizes it to a curved space-time that's why it's called general relativity in my view is not a very good name because it's actually a theory of gravity and it doesn't say so anywhere in the name but that's that's your historical name okay but that's that's that's a reason okay generalizes special relativity to curved space-time and that curvature is gravity okay so general relativity is a new theory of gravity a combined special relativity and the principle of equivalence and it postulates that gravity is a distortion in the geometry of space-time a curvature in space-time okay that's the reason of the name so from general relativity we get black holes we get gravitational waves we get the Big Bang Theory we get all of modern physics in space okay love all of modern astrophysics comes from general relativity it is a theory of gravity today even if we still use Newtonian theory because it's easier when we don't need the full fledged fear of gravity the theory of gravity we have today it's general relativity these are the equations of general relativity I'll show them to you in a minute the written here nicely in a notes train somewhere in Tina no sir someone in Bolivia sorry this is all train rusting out and somebody went there and wrote answer questions in the words of a famous physicist who died about 10 years ago a bit less John Wheeler space-time tells matter how to move and matter tells space-time how to curve those are equations of a nice time these are the equations again these are einstein's equations when a physicist thinks of Einstein's equations we'll think of this ok e equals MC squared is not Einstein's equations it's just a simple relation these are intense equations the equations that tell us how curvature how space curves okay don't it doesn't matter if you don't know it standing all I'm gonna say about them is that the right-hand side is T we call it the stress-energy tensor it represents the distribution of mass and energy in the universe or in space the left-hand side is G we call it Einsteins tensor einstein's curvature tensor and it represents the geometry of space-time okay so geometry equals distribution of matter and energy the equations are really beautiful actually these are more complex than you need you can cross out this term this term is the cosmological constant it's only important for cosmology so if you're thinking about about just black holes and things like that this is 0k these are the equations but I'm gonna talk about about this question in a minute okay so a little bit about them so they're extremely complicated equations for those of us of you who understand a little bit of mathematics there are partial differential equations second-order partial differential equations in four dimensions coupled and nonlinear worse they have thousands of terms they look very innocent actually when you write them out out completely with every single term they have literally I'm not exaggerating about 3,000 terms you just put them in Mathematica or maple and expand them it's about three thousand terms it's true so they're complicated okay difficult to solve how do we solve them how do we normally solve them if we are doing astrophysics if we want to study the origin of the universe if we want to study black holes anything like that what we do is this we give a reasonable distribution of matter energy we say there's a star there or there's a galaxy there's a black hole or we have the whole universe with matter distributed so we give a reasonable mass energy distribution we plug that into the equation solve the differential equations which are really complicated and obtain out a physical space stamp geometry the geometry of space and time this is the way we do it normally that's the way we get Astrophysical relevant solutions okay keep energy and distribution as an energy obtain geometry but the thing is you can do it the other way around and that's what I'm gonna come back to that in a second you can cheat so you can go back and say no no I'm gonna give you a nice space-time geometry that I like for some reason I like the geometry so I put it here work from left to right and read out the mass energy distribution I mean okay that's called designer space times you design your space-time the way you like it and read out the energy distribution most of the time this makes no sense it's nonsensical okay when you work this way you say you solved Einstein's equations when you work this way you say you just gave a model for a nice geometry this is not a solution of Einstein's equations is this okay and that's important because the rest of the talk I'm gonna go this way now once you've accepted the fact that you can change the geometry of space and time and you can use that to cheat Einstein so you can use Einstein to cheat Einstein you can use that to figure out geometries that allow you to travel faster than light and that's that's a nice thing the easiest thing to imagine that the first people thought up is you can make a tunnel imagine you live here this is Earth and you want to go to a distant galaxy which is over here so if you could bend space and then make a tunnel if you go this way it might take you thousands of years but if you go this way it might take you just an hour okay this is easy you can draw the geometry really easy that's it I just threw it okay this is called the wormhole it's also called an einstein-rosen bridge why because Einstein and Rosen we're the first wants to figure out a geometry like this in the 1930s so even Einstein himself already knew about this okay this wormhole we've known about these things for 80 years or more this is a simple geometry now are they allowed in general relativity actually yes they are allowed in general relativity the very first solution of the equations of Einstein was found in 1916 by Croatia this is interesting because when Einstein first presented his equations in November 1915 they were so horribly complicated they are very complicated but Einstein saw them and I thought these things are so horribly complicated and nobody will ever find a solution so I'm gonna work on finding approximations and that's what it did but two months later controversial in February 1916 discovered a true exact solution so Einstein was wrong you could actually find solutions the first one was discovered 1916 this solution now we know represents a black hole at the time they didn't understand it very well but it represents a black hole and it turns out to have not only a black hole or a wormhole inside now black holes and wormholes are different things okay a wormhole is this tunnel and a black hole is this thing you get at the end of the life of a large star when matter has collapsed those itself to a point so there are different things but inside a black hole you have a wormhole which is weird and nice is this wormhole inside the solution so complicated that nobody could figure it out completely and it took 20 years before Einstein and rose and discovered that inside that solution there was wrong they called it the tunnel and because of that they're called today einstein-rosen tunnels so it's there in the solution it's a mathematical solution but this one is not very useful it's actually not useful at all this wormhole inside a black hole is dynamic it means it closes up it opens and closes it closes up so fast that makes it impossible to traverse it even even if you're going at the speed of light it will just collapse on you and they connect to a different universe even if you could go through you'll end up in a different universe not in another part of our universe which is not particularly interesting but it's been used in science fiction as you know Carl Sagan used it his novel contact he actually contacted Kip Thorne was a friend of mine to ask him about these things Carl Sagan wanted to use a black hole in his novel to travel to other stars and keep thrown to him black holes on work would use a wormhole and that worked so it's been all over the place in science fiction there's another this is Stargate so they have wormholes this is deep space 9 dr. T space nice they have wormhole all over the place in science fiction so remember they are allowed by the theory of relativity okay we don't know how to make them what they are allowed but there's another idea which is the reason I'm here it's actually more ideas but I'm just going to mention this one okay back in 1994 I had a different idea I was watching Star Trek which is true and I was I got me to thinking is if it was any way in which you could come up with a geometry of space-time that was similar to this idea of warp drive in science fiction that allowed you to travel faster than light bending somehow space so my idea was not to move through space but rather to move with space somewhat similar to what you do in travel lasers at at airports they just stand there and you move you didn't have to walk it just pushes you along so the idea was if space can do the work and I came to with up with the concept of what I call today a warp bubble I don't like the name warp drive even though I use it because drive gives you the idea that this machine okay gives you the idea that there's a ship I don't know anything about a ship I have no idea how to make it work so I prefer to call it a warp bubble it's a distortion in the geometry of space and time so the idea is if you're sitting in a region of Splatt space-time and somehow you can expand space behind you really violently that will expand space here it will move me away from the wall and if I contract space in front of me it will move me to us that wall so I can do that if I can expand space here and contract it here I'll move that way without would that happen to move at all that's a basic idea it's similar as I was saying to a travelator in an airport you're going in this in this Traveling Pants in an airport you can imagine that behind you the floor is being created out of nothing of course it's not what you can imagine it and in front of you floor is being destroyed and then you move along right that's the idea you have space being created expanded behind you space being contracted in front of you okay and you sit in an ice region in the middle or nothing is happening in a flat region so that's the basic idea of the warp drive or the warp bubble local expansion of space behind you and a local construction in front this idea is similar to the idea that we know of of the expansion of the universe we've known since the 20s that the universe is expanding okay the universe does expand so space-time can expand when you think about the expansion of the universe many people think think it wrongly because when you hear the Big Bang you think something exploded and think just flew off in every direction that's not the Big Bang okay that's not how it works when you people ask you where was the Big Bang but it was here it was there was everywhere the Big Bang is not an explosion in that sense the Big Bang is the creation of space that wasn't there we didn't have anything and then suddenly space up here and started stretching it's much more similar to the idea if you have one of this rubber surfaces where kids like to jump but it's really long and infinite and you start pulling it from the sides so then it will expand okay but everywhere at the same time so that's the expansion of the university space is expanding so we know that so of course it's allowed to expand in the same way you can sell out to contract and there's no limit to how fast space can expand it can span faster than light that's okay there's no problem that doesn't violate anything it doesn't violate anything in relativity space going to spend at any speed in fact that's true today if you go far away into the you probably know the expansion of the universe implies that galaxies that are further away from us move faster and faster away from us okay the further away a galaxy is the faster it moves it's the first question that comes into mind is it possible for a galaxy to be so far away that it's moving with respect to us faster than life yes we call that the cosmic horizon that's a place where galaxies are moving so far away so fast away from us they're actually moving faster than life does that violate relativity no that's actually a consequence of relativity that comes out of the theory of relativity so yes galaxies can move far away from us faster than light yes why because they're not not moving they're actually at rest what's moving in space space in the middle that's expanding space can't expand at any speed at once that's not a problem okay so that's the idea of the warp right okay if you want to see that the mathematics I just put it there is pretty simple that's that's actually the warp right there right there it's a geometry of space-time remember Minkowski the Pythagoras theorem so this is the two square two plazas on one - and on the other direction the direction you want to move you change it it doesn't really matter the details but you have to change it in one direction but it's a geometry what I wanted you see is this it's a simple equation which represents essentially Pythagoras theorem in four dimension it's just geometry that's all it is my paper is just writing this equation explain to the shrimps and and telling people what it means that that's the whole paper okay it's really simple I'm not going to go into the details but I just wanted for physicists in the audience that's it okay that's a paper now there's problems with the grow up warp right and with wormholes there's several problems now as I said before when when you solve Einstein's equations a real true bona fide a Astrophysical solutions of Anna's equations is tell me the matter distribution I will work through the differential equations and solve for the geometry of space-time that's the way to do it this is the other way this is I want this geometry I like it it's nice plug it into Einstein's equations see what mass energy distribution you need and what happens is that mass energy distribution usually is nonsensical doesn't make any sense the first thing you discover when you pull up that and do that for the warp right and also from work for wormholes is that you need something that faces is called negative energy okay purging it a lot and then you need something that's called negative energy now negative energy maybe it doesn't sound extremely strange to you but remember energy and mass are the same thing equals MC squared mass and energy the same thing so when I say negative energy I really mean negative mass negative mass that's a problem have you ever encountered something that wastes minus some number of pounds no right there's no negative mass there's no negative energy as far as we understand it has never been found in nature no known form of energy produces this it's another way to say we need under gravity okay negative mass would produce anti-gravity we've never seen anti-gravity in the lab we don't know of any kind of energy distribution that produces anti-gravity not even theoretically nothing it hasn't been found in any accelerator okay there are some quantum effects that might but that's another story if you have a question I might answer it but there's extremely tiny but it's on the other hand you've never found it we've never seen it but it's not forbidden there's no law in physics that says this can't happen as far as we understand so that's a problem okay it happens both in the case of the warp right and it happens also in the case of wormholes not only that you need negative energy and you need huge quantities of it the original version of the warp drive the one I showed you here I never did the calculation myself but somebody did it few years after if you wanted a warp bubble about a hundred meters in diameter with walls of about ten meters where this expansion and contraction are happening and you calculate how much negative energy you need it turns out that you need the equivalent in negative energy to the mass of the entire universe so you need negative energy and you need a whole universe of it which is ridiculous then people played with this and modified it and made some assumptions and eventually someone published a paper in which he showed mathematically that you could find a modified version of the warp drive that would need about the mass of Jupiter in negative energy to push a spaceship not bigger than a car okay imagine a spaceship the size of a car you want to move move that about twice the speed of light you will need AK the equivalent of the entire mass of Jupiter in negative energy to power it up so you need negative energy and you need ridiculous amounts of negative energy that's really a big problem okay that's it's the another interesting thing that I just added this slide yesterday because people keep asking about it people tend to think that because space is expanding behind me in this warp bubble that means that the negative energy has to be behind me because it's anti-gravity and it produces it but that's not true when you do the math it turns out that the negative energy is actually located to the sides around you in a torus it's not behind you it's not in front of you around the that's what you needed this is a plot of the negative energy distribution in a warp drive with thick walls and when thin walls and it's the world probe is actually moving to the left to the right sorry left to right you see that the negative energies towards the sides okay that's that's interesting and that explains these you've probably seen this right this is a nice concept warp drive space spaceship designed by Mark rod maker so why did he put this strange lobes here because he knows that if you want negative energy it's around you so you need to have something that generates negative energy around you not on the back okay and that's the reason he put this in the design now please don't fall for the hype this is a nice concept based just on the metric but we have no idea how to build this at all we have no idea how to build a warp engine we don't have the negative energy and even if we did we would need an entire planets okay negative energy so that's not practical okay now another question those negative energy actually exist as I said we've never seen it but that's not in time and until this number should probably change down to about 20 years but until about 20 years ago we haven't never found any evidence of anti-gravity in the universe but 20 years ago something strange happened people were studying expansion of the universe and particularly they wanted to find out if the expansion of the universe is slowing down and how fast we call that the deceleration of the expansion how it decelerates if I throw this up it will eventually come back down so it's decelerates and then comes back so the same idea applies to the universities expanding it will slow down and maybe eventually come back out so they wanted to measure how how fast it's slowing down and for that they needed to measure the distance to very far supernovas and very very detailed and very carefully the distance a lot of supernovas really far away so it took them many years it was only people were only able to do it in the 90s because the technology just wasn't there before eventually they moved they measured it and big surprise the expansion is not slowing down its accelerating this is this is just as terrible as if I just threw this up and I saw it accelerate upwards instead of falling back down it's exactly the same thing just on the scale of the universe it doesn't make sense okay so the people that did this work initially thought they were wrong and decided not to publish it and start again from scratch and they did it again it took another two years and they got the same result again so they said they say they decided to publish it eventually they got the Nobel Prize for that but initially was really scary the expansion of the universe is accelerating the only way we can understand that today is if at the cosmological level there is something that produces anti-gravity we call it dark energy we don't know what it is dark energy is just the name for something that we don't know what it is but that constitutes 70% of the total energy content of the universe and produces anti-gravity so there is a hint of anti-gravity in the universe out there can we use it to create wormholes or what price we don't know it's still too early to know maybe not yes but who knows you can hope but maybe these will say that's my hope now there's another problem with the work right we should normally I don't talk about but there's an interesting problem it's called the horizon problem turns out that if you want a warp drive that moves speeds that are small you don't need a warp drive to move faster than life you could use it to move slower than life if you want that you need negative energy and that's the problem but if you want to use it to move faster than light and there's another problem it turns out that the from this is the the warp bubble again is the spaceship here space expanding back and contracting the front okay if it's moving faster than light it turns out there's a region in front of the bubble that it's completely causally disconnected from the ship it means the ship can't send a signal here it means the ship can't put the negative energy there even if it has it it can't reach it can stop it it can't do anything it's this region in front of the bubble it's completely out of touch with the ship which means the ship cannot control it you cannot even start it you cannot reach the front which means you can't do it you cannot do it from inside the ship you would be able to do it from the outside you could say somebody went there slower than light with a normal rocket and put negative energy generation master generators along the way and then somebody came behind it and these generators were we just switched on at the right time as this other ship was passing by and then you could do it but you cannot generate the watt warp bubble from the inside if you want it to travel faster than light it has to be set up from the outside that's called the horizon problem okay it's a very serious problem as far as I know nobody's been able to solve this one okay and of course as I mentioned at the beginning of the talk why we can't move faster than light because it breaks causality okay it turns out it's still true you find any way to travel faster than light even cheating with wormholes or what bubbles anyway you still can use it to build a time machine you can use it to travel back in time and this is not nice you might think it's nice if you like science fiction but from the point of view of the physicists it's not nice adorable time-travel destroys causality and Briggs brings with it many paradoxes I'm sure you've seen them if you want if you like science fiction the grandfather paradox travel to the past and kill a young boy who was supposed to be my grandfather if he's dead how was how is he my grandfather and he's dead how was it born Danny Boy was not born how did I go back and kill him it doesn't make any sense okay I like this one where's the watchmaker I like that one you've seen it probably in a movie an old movie from the 80s time at your time I think that it's an old man gives me a nice watch so I'm giving this talk and then mr. nice old guy from there he comes here says I like to talk I want to give you a present give me a nice watch and said nice take the watch I invented later I invent the trap time machine I travel to the past or 80 years to the past I meet a young boy five years old he likes the watch I gave it to him and this this little guy eventually grows up to be the old man that gave me the watch it's the same watch who built it who made the watch it was never made in any Factory it's just been going around nobody ever created the watch doesn't make sense okay it's worse you can do it because people have been it people say well the watch will eventually break down it's just going round and round it'll break down but you can do it with something that's not physical that's information I traveled to the past and meet an old and half that that deaf and very depressed the tavern was only wrote hate sinfulness and he doesn't want to write anything anymore so I just tried to cheer him up and I sing the ode to joy to him and he likes it and he writes the ninth symphony so who composed it it wasn't me because I heard it in a CD of the Tobin's music and it wasn't him because he hear it from me so there's a loop of information who invented that that that's an X n so time-travel is nasty ok we don't like it we don't like it at all that's the reason why Stephen Hawking Chile has a conjecture he calls it the preneur chronology protection conjecture which is complicated language just to say that the laws of physics prohibit time travel to the past day that's what it says it's a conjecture which means it I'm not has not been proven but there are actually very good arguments in its favor based on quantum physics yeah but it doesn't actually prohibit faster than light travel it only tells you that you cannot use it to build a time machine which is nice because if this is true then we might be able to travel faster than light as long as we don't try to use it to build a time if you try to use it to build a time machine something's gonna go really bad what could happen your time machine collapses into a black hole before you can use it for example or they explode in your face and that that wouldn't make sense oh I like this okay that makes gives me hope but finally and I'm gonna go back to the top by David Brin do we really need to travel faster than light well we need to travel faster than light you want to go back there and come back as ourselves in our lifetimes okay would we forget about that if we think just about the species humanity then we don't really need to travel faster than light okay traveling at 10% of the speed of light you can cross the entire galaxy side-to-side in 1 million years 1 million years is a long time for a single individual but it's not a long time at all for this human species you could actually colonize it to the very last star in less than about 5 million years David Brin said so in less than about five million years you could colonize every single star in the galaxy and you could travel of ten percent of the speed of light and 10 percent of the speed of light doesn't seem unreasonable at all seems pretty feasible there's nothing preventing us from doing that okay we probably have a spaceship doing that you committed the resources in about honey maybe less than 100 years in a few decades if we really have to the financial resources and the will to do it we could probably do it and we could colonize the entire galaxy to the last single star in a few million years so that that brings me back to the question of the Fermi paradox where is everybody because if we could do it in five million years why nobody has done it the galaxy's 12 billion years old nobody's done it you know 12 billion years nobody's happy idea to do it if a single species have decided to do it the galaxy would have been over wrong long and he hasn't been so that really worries me I don't that that keeps me up at night where is everyone really alone can we travel fast and light so special relativity tells us no because it would break causality general relativity seems to allow us to cheat but it requires anti-gravity negative energy and huge quantities of it planetary sized quantities of it and even if we could at least in the case of the warp drive we would also need to solve the harassment program which nobody knows how to solve if you have wormhole that's not a problem but nobody knows how to make wormans anyway and even if it turns out to be possible with all this ifs we still need to face the problem of time travel paradoxes which is really a problem so I don't really know the answer I think at least what has changed perhaps in the last 30 years for 27 years is that twenty-something years ago we would have said it's impossible forget about it today we think you could get around the laws of physics and do it but it's still highly highly speculative so I leave you with that point thank you very much [Applause] but well in time we can we can travel forward in time that's not a problem the easiest way to say it is we're traveling for in time now one second at a time what but you want to go faster you can do that as well there's two ways to do it you can go very very fast very close to the speed of light far away and back and then you use something called the time dilation it turns out that when something looks very fast with respect to you it's it's clocks slow down move say to Alpha Centauri at 99 percent of the speed of light and back then on earth Alpha Centauri is five light-years away so another would have been about ten years and for somebody on that spaceship it could have been a month so that's a way to travel forward in time you experience one month and you actually went ahead in time ten years you can do that another way to do it is to use another phenomenon called gravitational time dilation that's also being proven we know that gravity causes time to slow down that's also proven it's been measured without any doubt actually you measure it every day just whenever use this thing to locate your position GPS GPS is proof stand violation every single day because gravity slows down time which means time here on earth goes a bit a little bit slower than time up there where the satellites the GPS satellites are going around it so those we lose one second every thirty years because of the gravity on earth but that's that doesn't seem like a lot but it's perfectly measured you can measure it with atomic clocks and the GPS satellites are essentially atomic clocks so if you don't take it into account the GPS doesn't work you have to take it into account because GPS is based on having perfectly synchronized synchronous atomic clocks in orbit and if they're gaining one second every thirty years that means they're in distance that would mean there would be wrong by about a hundred meters every week which is a disaster for GPS so you measure it every night so you can use that but of course in the earth is really small you're just one second every 30 years it's not a very fast way to go to the future but you could go close to a black hole you go very close to a black hole there the effect is huge it essentially can become infinite at the sir at the frontier of the black hole it's a very bad idea to cross the frontier like oh you can't come back out you get close to it but stay away and then come out you could stay close to the very close to the black hole going around the black hole for a few hours and back out and you would find that outside decades or maybe even centuries have Gilmar that's a way to go oh yeah sorry yeah well my thoughts on the many worlds theory well I'm not a founder one of many universes I tend to be a fan of Occam's razor it tells you that you should multiply hypotheses when you don't need them and I feel multiplying universes is a bit too much so I don't really like it I don't that's an interpretation of quantum mechanics that I think it's not necessary at all I think quantum mechanics is a statistical theory it tells us what happens when you have a large number of experiments of similar systems but it doesn't really tell us what happened with one but that's it that you don't need an exchange interpretation I think what ponta mechanics tells us is that in nature at the fundamental level is non-deterministic it has a probabilistic aspect so the outcome of one experiment cannot be predicted but it has a statistical statistical properties you can predict the statistical outcome of many but not of one and I think that's all there is to function theory I don't think you need to invent the universe's when it's something like that yeah distorts the geometry space well the question is if we could have a essentially gravity drive if my collisions in the Large Hadron Collider if I understand them well but particle collisions what you do with particle collisions is just concentrate a lot of energy in a very small region of space that's what you do but it's a lot of energy from the point of view of particle physics so these big huge particle collisions in the Large Hadron Collider when you light these protons has extremely high energies have less energy than the energy that this gets run by falling into the ground it's much less energy than that from the point even at that collision the thing is that energy in just one pair of particles is a lot of energy for two particles but at La when you think of it at real but every day large scales it's not a lot of energy yeah but it's really not a lot of images it's it's yeah that's an acceleration coming from electromagnetic forces not gravity gravity is the weakest force of all right by far orders of magnitudes about 40 40 orders of magnitudes weaker than electromagnetic forces so you get a lot of energy there but electromagnetic energy to make it gravity the effective gravity is just yeah but the the way you can see it is to produce noticeable gravitational effects unit planets you need the energy of a planet to produce something like gravity that we feel so that's that's the measure to see to show you just how weak it is huge [Laughter] that's a good question I really don't know my hope would be that you could reduce the good find also not so much negative mass at some kind of energy field it has the effects of negative energy like an electric field around magnetic field but something much more exotic than that but it could manipulate like magnetic field so we know how to manipulate electric and magnetic fields so you could found an exotic field with negative energy but similar you would be able to learn how to manipulate that energy field it wouldn't be more like an energy field maybe this is a dark energy dark energy turns out to be a physical energy field that we can manipulate maybe then we could use that but but it's all speculation at this point let's just ice fiction actually in that case bad science fiction there's no barrier at the edge of the candy yeah yeah I mean well the question is complicated so she was asking if there's a source for the dark energy and we could so how could we have a whole source but the dark energy or something like [Music] [Music] not really we don't actually know what dark energy is so actually unfortunately it seems that the best explanation for dark energy is that it's not an energy at all it's just a constant is the cosmological constant that works pretty well and I say unfortunately because that's the explanation then it's boring but but if the pressure hasn't changed because it's a constant so dark energy is the density and pressure of the arc energy has been constant throughout the history of the universe it doesn't dilute that's what makes it weird but if it's a constant then it doesn't matter just a constant but it doesn't dilute matter at all silent as the universe expands the density of matter goes down but the density of dark energy doesn't which is the reason why there's now there's more dark energy than matter because the matter has been going down but we don't really know what the source of our energy is if it's an energy field it would have been there from the beginning of the universe it was created who knows how at the beginning of the intervention just sitting there and but if it's a real energy field and it's not a constant then it could be dynamic and that might allow you to control it another possibility comes from quantum field theory which one I like quantum field theory tells you that the vacuum is not actually empty these quantum fluctuations in all the fields in the vacuum electromagnetic and everything of field in nature is fluctuating in the vacuum that's a problem there's really no problem because quantum fluctuations have energy and you have quantum fluctuations in the universe of every single field you have a huge amount of energy in principle actually infinite that would destroy general relativity will tell you that the universe couldn't exist so it doesn't make sense and we've known that problem forever and nobody's just put it on the rug it's called the cosmological problem constant from quantum field theory so what people think is maybe what happens we don't understand quantum field theory enough and when we do we'll find that this energy is canceled out from the different fields and you have a lot of infinity actor in or infinity but large quantities they cancel out and you're left with just essentially zero or a very small value that would be another problem because it's a fine-tuning problem but but that's one of the ideas now this is true and you have many condoms cancelling each other in the vacuum then if you could manipulate them and change the value just one of them a little bit then you suddenly have a huge amount of energy coming from the vacuum and that would be interesting right but we don't know the thing is quantum field theory works exactly like a cosmological constant but the number is wrong I don't have you've seen it but they call it the worst prediction in theoretical physics because it's wrong by 120 orders of magnitude in the best case yeah I haven't read them in any detail to be honest but my initial impression would be that it's those yeah oh they're they're not interpreting things correctly I don't really believe them it would take a very very impressive things to make me believe that [Music] that's true it yeah that's Ramirez close back we don't live in a very dense region of the universe as far as galaxies go the Local Group of galaxies has only about 20 galaxies only three of those are big Milky Way is the second largest Andromeda is the biggest and there's another one I don't remember its name but it's only three big ones and I love little tiny ones and apart from that is essentially nothing around here all the way to the peer group cluster that has thousands of galaxies but it's already about a hundred million light years away so yeah we don't live in a very populated region of the universe but yeah your principal if you could travel the whole galaxy you could reach Andromeda not much more difficult than that it's not that far away and if you wait three billion years we'll be here so that's you really you don't know that but Andromeda is coming this way and it's gonna hit us in 3 billion years so be ready I'm the emergent gravity and I've heard about button I don't really know much about it there is speculation in a dark mark I didn't talk at all about dark mother I talk about dark energy dark matter is a different thing it has normal gravity it just you can see there's two ways to think about it there's some form of matter that we haven't discovered that explains it and that would be the easiest explanation your other explanation is our theory of gravity is wrong and you need to fix it so both avenues of research have been looked at most people today I think most of the physicists and cosmologists today and by most I think 98% 99% will tell you the first explanation is probably right dark matter is not some form of particle we just haven't discovered in the accelerators the other 1 or 2 percent will tell you gravity is wrong nobody's been able to come up with a new theory of gravity that explains dark matter and still explains everything else that relativity explains that hasn't been done it's not that simple I don't know how many questions organizers will get to tell me it's even worse it's it's it's worse because a wormhole is a change in the topology you have something that doesn't have a hole and then you make hole that joins two pieces together we have no idea how to change the topology of space-time we don't even have a theory about that because general relativity is not a topological theory it doesn't tell you anything about topology tells you about local geometry which is a different thing but apology holes and things like that doesn't tell you anything if you if you give it a topology then it can tell you if that makes sense but how to change the apology from one to another I know music with that we're gonna break for lunch I want to report a Tiffany Pearson has arrived yes you got [Applause]

Channel: Icarus Interstellar

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Id: 5q_z8BjiYng

Length: 73min 11sec (4391 seconds)

Published: Fri Sep 01 2017