This is the second of the talks sponsored by RDF Few Years ago. I was at a conference and taking questions at the end and I Don't usually get hostile questions except from religious people, and they're extremely easy to handle But then I got a hostile question which was not so easy to handle It was a very tricky and a difficult question, and I thought who is this? It turned out to be one of those I'm an atheist, but questions, which are always the most difficult to deal with it was of course I have enormous respect for what he's doing in the field of public [understanding] of science, which is the field that I recently retired from Professing he is of course [a] most distinguished physicist author of many books he also interests himself in Science generally and in the promotion of the understanding of science generally He's recently moved to Arizona to [start] what I think is an [extremely] exciting initiative he is Associate director of the Beyond Center and co-director of [the] cosmology initiative and director of the new origins in Initiative at Arizona State University [so] the study of origins origins of all kinds right across the board from the origin of the universe To the origin of life to the origin and everything you can think of what a what an amazingly exciting Initiative to get started at A University, [I'm] delighted that lawrence is talking to us today, please welcome Thank you. Can you hear me now? Can you hear me? No, okay? Good? thanks, Richard actually it's let me just say that my friendship with Richard has been a Unique one in many ways, but one that's caused me every time we're together to think about things slightly differently I hope mutually and [and] a true pleasure and honor to to to be here Richard asked me to talk about cosmology [and] I originally Gave I talked to this cornwall who was organizing this and told her what I was going to talk about it and and gave her several titles and she Thought they were too depressing so she said why don't you just make it? We're all fucked, but uh but I decided not to use [that] title um the I Put this quote up here. Well I like to have quotes from people when when I'm being introduced so people have something to read but uh It's kind of useful. I think because I want to I'm going to talk about our modern picture of cosmology and how has changed our view of the universe the past and the future and In some sense, how that picture is Clearly remarkable and far more remarkable than the fairy tales that are made up in most religious situations and But the key point is mystery. That's one of the things that makes science, so special. I think is that scientists love mysteries They love not knowing That's a key part of science the excitement of learning about the universe and that again is so different than the sterile Aspect of religion where the excitement is apparently knowing everything although clearly knowing [nothing] Now in any case, so so that's one of the reasons. I put this quote up here but but I am going to talk to you about a mystery story, so Now I live in in Phoenix now and people know what these are I used to live in Cleveland and then I had to tell people these were stars and And this is a picture of globular cluster, and it's a beautiful thing on a nice clear night But what I want to talk to you [out] is how [our] picture has changed the universe so much that the really important stuff in The universe is not the stars and galaxies, but the stuff you can't see the mysterious stuff that dominates nature [okay], so it's mystery story, so let's begin. It was a dark and stormy night and Einstein had just developed his general theory of relativity in 1916 an Interesting time because he had developed that theory which was the first theory of not just how objects move through space But how space itself could could expand and contract and be dynamical a remarkable theory that told us that space Curves in the presence of matter and it was beautiful, and he kind of knew it was correct but at the time it disagreed with observation which used to bother physicists in the old days and the Via And the observation was that the universe was static and eternal that was the conventional wisdom in science at the time that the universe had been around forever and would be around forever and His theory didn't agree with that because his theory general relativity suffered from the same problems that grant Newtonian Gravity suffers from Gravity sucks It always pulls it never pushes and if you put stars and galaxies out there, they will not just stay there Gravity will produce a universal attraction that will pull them together and So he he tried to figure out what to do and and he was able to change his theory slightly consistent with the mathematical Symmetries that allowed him to [develop] it so I wanted to show you how he did this so I'm having equations Which is a good thing to do at 9:45 in the morning or whatever? But I do have them in a user-friendly fashion here Okay This is for the biologists. No. I'm just joking it is but uh the So it's not completely facetious because the the [left-hand] side of Einstein's equations tells you about the geometry [of] the universe How things are curved in the presence of the source of curvature which in this case is the energy and momentum of the universe? So that's fine, and in fact. I [I'm] a theoretical physicist so I have to write the actual stuff the greek letters That's much more illuminating to you. I'm sure ah But so this was the theory that didn't work [that] explained the universe we didn't live in Or so he thought and so he was able to change it a little bit by adding an extra term [to] the left hand side Which he called the cosmological term That this term on the left hand side would produce a small repulsive Force throughout empty space so small that it wouldn't affect the Newton's laws which of course that described beautifully are developed in fact to describe the motion of the planets around the sun And you wouldn't want to destroy that so so small. You'd never measure it in the solar system But it could build off on the scale of galaxies and hold galaxies apart And so that's what that's how he thought he'd saved his theory now shortly after he introduced this term [it] became clear that it was a problem and in fact It here's a postcard. I got when I was on leave once and in switzerland in Zurich and it's from Einstein to to Hermann vile Who's a very famous mathematical physicist and it's in German and some of your german is better than mine But this basically says it's already 1923 and he's already saying if you get rid of a quasi-static universe then out with the cosmological constant Because he realized that If the universe is really expanding which is what we now know and I'll talk [to] you about How we know that then you don't need a cosmological cost anymore if the universe is expanding Gravity can be universally attractive and just slow the expansion and the big question of 20th Century cosmology became is There enough gravity to stop the expansion how will the universe end will it end with a bang or a whimper will it end with a big crunch the reverse of the big bang or will expand forever [in] fact and that's the reason why I as a Particle physicist got involved in cosmology because I I want it to be the first person to know how the universe would end it seemed like a good [idea], and you'll see where that came from but so in 1923 Einstein said you know I wish I'd put it in and threw it out but but it was really not 1923 but 1929 When we really knew the universe was expanding and this is the person who convinced us? This is someone and I always say this so some of you may heard me say this before, but it's true He this guy always gives me faith in humanity This is Edwin hubble, and he began life as a lawyer and became an astronomer, and so there is hope [and] He made of many discoveries, and I think as I'm a little short [of] time I won't talk about the biggest one [of] the ones he made but the biggest one he made of course was the discovery that the [universe] is in fact expanding and it changed everything and He this is what he discovered now. These are not sperm these are galaxies these are again for the biologists um the So our Galaxy is here, and when we look out We see what he discovered was that all other galaxies are moving away from us on average and those are twice as far away are Moving twice as fast those are three times as far away or moving three times as fast etcetera and so and we codify this saying velocity is proportional to distance and Now what does this tell you okay? Well it obviously tells you we are the center [of] the universe okay, and actually does and in fact my wife reminds me of that on a daily basis and It really really means is that the universe is expanding Uniformly in all directions now. Why does [that] why does this ridiculous observation that where everything is moving away from us? Tell us that and I've spent a lot of time trying to think of different ways [to] explain this none of which have been Particularly satisfactory, but I this this I think the only way to understand that is [to] get outside the universe we're in California it's easy to do that here, but uh But but let me do it this way. Here's the universe that's that's [two-dimensional] and that you can stand outside of and Here's you know I've put the galaxies at nice uniform distances here and and again here And you can see at a later time the universe is bigger the galaxies are a little bit further apart [so] if you were standing outside of that universe would be obvious that it was expanding uniformly in all directions now what would you see if you're on that universe well just pick a gal see any galaxy [and] The way we can figure out what you can see from the Galaxy is to superimpose this image on top of this one placing this Galaxy on top of itself okay, what do you see you see precisely what? Hubble saw every Galaxy is moving away from this galaxy Those that are twice as far away of moved twice the distance at the same time those are three times as far away blue three Times the distance and it doesn't matter which galaxy you're on everywhere you see the same thing everywhere you think you're the center of the universe, so Depending upon your mood either every place is the center of the universe or no place as the center of the university doesn't matter The universe is expanding and that really did change everything and by the way it had profound religious implications for at least as Meant some of you may know that it in response to this and other things that the pope at the time and gave an encyclical that science had proved genesis and the interesting person the first person [that] actually showed there had to be a big bang was a belgian priest who was also a physicist named George lament and The really interesting thing about lament is when is when the pope said that? [nomad] him a letter and said stop saying that Just really amazing for a priest because he said this is a scientific theory You can take it if you believe in God and believe in Genesis to validate your beliefs But you can also take it To mean that in fact the laws of physics take us right back [to] the beginning of time without God What you take from it depends upon your religious and metaphysical beliefs But whether whatever you say the big bang happened and I think that's that's if we could [just] convince a lot of people of just that that simple thing that the universe is the way It is whether we like it or not I? Think we had overcome a lot of problems in this country, and I have to waste far too much time on [that] anyway Okay, but this is a science talk although. I'll throw in little bits of commentary throughout. I suppose How do we know the universe is expanding? It's such an important thing. I want to spend a few minutes on that Well, we do [buy] as these two guys on the on the plane out there in near Arizona say to one another [I] Love hearing that lonesome wail of the train whistle as the magnitude of the frequency the wave changes due to the doppler effect now What they're pointing out? Is that when a train comes towards you the train whistle sounds higher? when a train moves away from you train whistle sounds lower and that same principle was used by Hubble and others the same is true for light for very different reasons so when we look at Distant galaxies If they're moving away from us the light which is a wave gets stretched out the longer Wavelength part of light or the red end Of the spectrum, so it's called red shifted and galaxies are more and more redshifted the further and further They are away from us. So that's how we know their velocity The velocity is easy. How do you know distance that's really hard the universe is a big place and we [don't] have take measures that are that big we have to find some a way of determining distance without actually going to a place and that's hard and in fact The one of the ways well we of course the way. We do it is we use physics we could determine the distance to the back of the room if I turned out all the lights and only one light was on and I knew it had 100 watt light bulb by having an old-fashioned camera which none of us have anymore that had light meter on it and If there were 100 [watts] there, and I was receiving one watt of light here I know how that light spreads out is one over the square of distance and so I could determine By how much wattage I was receiving here knowing the wattage of that light bulb How far away it was okay does undergraduate or high school physics exercise? The problem is the universe isn't full of underwater light bulbs if it was life would be easier So we have to try and find the equivalent. We have to try and find what's called a standard candle something whose intrinsic brightness we understand and Therefore when we look at it through a telescope We see how bright it appears through the telescope, and we work backwards [to] figure out how [harder]. How far it is That's the hard part That's why it's been so hard to determine the rate of expansion of the [universe] because it's hard to and standard candles this is this is Hubble's original data from 1929 and This is one of the reasons He was such a great scientist because he knew to draw a straight line through this data set which itself is already not so clear it's not not obviously the right answer and He and but what he found was in fact that velocity is proportional to distance, okay? And the great thing is he got the answer wrong by a factor of 10 which Which was an embarrassment at the time again? I'll throw a little commentary in it because if the universe were expanding this fast you could [calculate] its age and its age would be 1.5 billion years old that was in 1929 now as anyone knows if you rear any of Richard's books you would know that well but by 1929 we already knew the [earth] was older than 1.5 billion years old and So it was embarrassing that the universe was younger than the earth One of the many embarrassments in cosmology that's happened over the [years] and in fact taken by some people to once again Argue that science didn't know what it was doing But the problem was of course he wasn't a bad astronomer about scientists the problem was trying to measure Distance because he didn't have good standard candles And that's as I say been the the holy grail if you wish of his cosmology over the last century And we now have standard candles here's here's one. I wish there was better resolution on this projector It's a beautiful picture from the hubble space telescope [of] a distant Galaxy Far far away and long long ago, and and there's a whole galaxy. It's about a billion light years away We're looking at it as it looked a billion years ago so so many of those stars no longer exist and Here's an object that's just as bright as the whole center of the Galaxy [you] think it's a star That's near in our galaxy that just got caught in the picture frame it's not it's a star in the edge of that galaxy that has exploded and exploding stars shine with the brightness of 10 billion stars so the brightest fireworks in the universe, Supernova and They're remarkable and I Keep having asides. Maybe I'll get to my point eventually but the This is something that that I wrote a whole book about and someone asked me yesterday Why I wrote that book because it is the most poetic thing I know about the universe Richard wrote a great book called our To call our ancestors. What's it called testers tale? Yes? I want to make sure I got that right and I wrote a book that was a different ancestor still. It's called Adam But the amazing thing is [that] every atom in your body? came from a star that exploded and The atoms in your left hand probably came from a different star than your right hand It really is the most poetic thing I know about physics you are all stardust you couldn't be here [if] stars hadn't exploded because the elements the Carbon nitrogen Oxygen iron all the things that matter for evolution Were created at the beginning of time they're created the nuclear furnaces of stars and the only way they can get into your body is If the stars were kind enough to explode so forget, Jesus the stars died so that you could be here today Okay, and and anyway This is great Anyway, ah so that the point is the real point of what I reason I showed this [picture] Is that these objects these exploding stars are great standard candles we can actually observe them Amazingly even though only one occurs every hundred years per Galaxy there are enough galaxies that if you put your hand up in the night in away from La and Looked in a dark spot in the sky made a hole the size of a dime With a large enough telescope, you could see a hundred thousand galaxies and that means that even though stars explode once every hundred years per Galaxy in that little region with a hundred thousand galaxies on a Given night you'll see ten stars explode The universe is huge and old and rare things happen all the time including life and So it's an amazing thing and here's that we can observe stars exploding we can measure their brightness We can measure their colors and that has allowed us to produce a great standard candle and after 75 Years we now can determine the expansion rate of the universe This is [a] nuke bubble diagram much better than Hubble's was made after the discovery that on a log-log plot everything is a straight line and and but even even still we now know the rate of expansion of the [universe] to 10% not a factor of 10 and We therefore in fact we now know the age of the universe through other things extremely accurately to almost four decimal places 13.7 two billion years is the age of the [year] of the universe it's amazing that we can say that with a straight face and have Scientific reasons to support that okay great. So let's go back to Einstein the Einstein had this cosmological term he said I with my biggest blunder I want to throw it out get rid of it, but the problem [is] you can't get rid of it so easily Because using the miracle of Modern Mathematics you can rewrite that equation and Now this is this is [a] small step for a mathematician But a giant leap for physicist not because it's that hard to put this term over there most of us could do that But because it now represents something very different when it's on this side [of] the equations here It was somehow a geometric quantity when it's here It looks like a new contribution of the energy and momentum of the universe what could contribute a term like this And we know the answer nothing By nothing I don't mean nothing. I mean [nothing] if you take empty space And that means get rid [of] all the particles all the radiation absolutely everything So there's nothing there if that nothing weighs something Then it contributes a term like this now That sounds ridiculous. Why should nothing weigh something nothing is nothing The answer is nothing isn't nothing anymore in Physics because of the laws of [Quantum] mechanics and special relativity on extremely [small] scales Nothing is really a boiling bubbling brew of virtual particles that popping in and out of existence In a time scale so short you can't see them now [again], that sounds like philosophy like counting the number of angels on [the] head of a pin or religion or something Useless, I shouldn't say dan Dennett is here. I shouldn't say philosophies useless it um anyway, Bob Is Also friend but uh? The point is it we can't measure virtual particles directly, but we can measure their effects indirectly and in fact They're responsible for the best predictions and physics Here by the way is actually An animation that was shown at the Nobel prize ceremonies about five years ago by a friend of mine who able to win the nobel prize for developing the theory that produces This is the space inside of a proton the empty space inside of a proton not where the quarks are the empty space between the corpse and This is not an this is an animation, but it's an exact animation coming from Physical calculations This is [what] the space looks like now How do we know that well there are a lot of reasons? But one of the things are it turns out most of the mass of the proton Comes not from the quarks within a proton but from the empty space between the quarks these fields popping in and out of existence produce about 90% of the mass of a proton and since protons and neutrons are the dominant stuff in your body The Empty space is responsible for 90% of your mass So these empty space is vital to science and these calculations are vital to understanding not just protons But electrons and atoms and produce the best Comparisons the and I will repeat this the best Comparisons between theory and experiment in all of science to ten decimal places in Quantum electrodynamics using these calculations We can get the right answer. [it's] amazing. So if that's the case let's calculate the energy of nothing Where there's nothing else and when we do that? We come up with a calculation Which is pretty bad it's the worst prediction in all of physics We calculate you can't even see it. I think there's a one at the end of that We calculate that the energy of empty space is a gazillion times the energy of everything we see That as I say is the worst prediction in all of physics. Which is why we didn't talk about it for a long time we calculate that empty space should have an energy of 120 orders of magnitude more than galaxies and stars and people and aliens and all the rest and Is that where the case we just wouldn't be here? So we knew something was wrong with this calculation. It's been around since I was a graduate student And we knew what the answer was Theorists always know the answer they just sometimes write the We knew the answer was zero because it's the [only] sensible answer because you know you can't count you Can't cancel a big number like this Let's say the energy of empty space was comparable to the [energy] of everything. We see well [we'd] have to [cancel] this big number to 120 decimal places and leave a finite answer in the 120 first decimal place No one knows how to do that in science, but zero is a number we can get beautifully in science we use math automatically symmetries things cancel equal and opposite things cancel all the time in science because of symmetries of Nature So we knew the answer we didn't know what the symmetry was? But we knew the answer was zero and we could go to bed at night [and] that was fine but you know the neat thing about cosmology is it's really a science and Science is empirical knowing the answer means nothing testing your knowledge means everything and So the question is we should test what the energy of empty space is and how can we do that will we weigh the universe How do we do that we stand on the shoulders of Giants? This is a picture I took in in an island off Sweden Which used to be an island [no] an island off Denmark now which used to be an island off Sweden the Island of Hven I think I said that right and This guy if you look carefully he doesn't have the end of his nose His name is tycho brahe hey and he he as many of you know Laid the basis for Newton's law of Gravity by doing nothing other than spending 20 years on his back a noble tradition Look in this case looking up at the sky without a telescope Measuring the positions of the planets around the sun, and then he was a crummy feudal Lord He got kicked off that island. He gave the date went to prague gave the data to a hapless assistant named Johannes Kepler Who again spent 20 years without a [mackintosh] trying to interpret the data and and fudged it? We now know And came up with of course Kepler's laws which led to Newtonian Gravity and the point is we can use Gravity to weigh the Universe including The weight of Empty space now. Why do we care the reason [I] got into cosmology? General relativity tells us that space is curved and therefore the universe can be one of three different geometries Open closed or flat now. I can't draw pictures of three dimensional curved universes very well, so here are pictures of two dimensional curved universes This is a closed universe Sphere a surface of a sphere in two dimensions, but if we had a closed three-dimensional universe, it's very simple It'd be very similar if we if if our universe was closed, we would look if we looked far enough in that direction We would see the back of our heads light would go around the universe an Open universe will be Infinite spatial extents as a flat universe that sounds really nice But it's irrelevant the really important thing is in a universe full of matter a closed universe will expand and Stop and then [Rika] laps in a big bang in a big crunch to reverse the big bang An open universe will expand forever and a flat universe will expand and slow down, but never quite stop And that's why we wanted to know which universe we live in and as they say that's why I wanted to to learn about it because once I knew which universe we lived in I would know how the universe ended okay, and so Weighing the universe tells us what the curvature of the [universe] is and that's why we want to weigh so here I [wanted] [to] show you the next few minutes how in fact some of the most remarkable developments in cosmology, and then tell you how they completely changed our picture of the universe so we understand that the [universe] we live [in] is the worst of all possible universes to live in Okay, just so you [know], we're heading This is a cluster of galaxies Each dot in this picture is a galaxy again amazing to think about remarkable every one of these galaxies contains hundreds of billions billions of stars and perhaps Civilizations some civilizations that are mired in religious gunk other civilizations that have moved Beyond But and other civilizations are long dead because he said this is about three billion light years away Three billion years ago is when that picture was taken basically Now clusters of galaxies are the biggest bound objects in the universe [so] if we could weigh them we can weigh all the mass in the [universe] and we can weigh them then We can weigh them by using general relativity because in this picture is A remarkable phenomena that Einstein first predicted in 1937 though He said it would never be observed [underestimated] observers if you look at this picture, you'll see these blue things these weird blue things That is a phenomena that we now understand as gravitational lensing Einstein told us that a mass will curve space Around it and he realized therefore if you had a big enough, mass and you have a source of light behind that mask [the] light can bend around that object [and] come back and be Magnified just like my glasses magnify things or like [a] cut glass goblet if you look through it you [see] many I'd see many images of this room Mass can Act like a lens and magnify things and split images And that's precisely what we're seeing all of these blue things are different images of a single Galaxy located about three billion light-years behind this cluster Gravity is magnifying the image Distorting it and bending it remarkable Truly remarkable, but because we understand general relativity we could work backwards and figure [out] how much mass must be in that system, and where it is in order to produce that image We can weigh the system using general relativity and we do that. Here's here's an inversion by Tony tyson who's now up in Davis These are this is the [system] and the spikes are where well this is where the masses in the system? the spikes are where the Galaxies are But you notice most of the mass in this whole system of clusters of galaxies is not where the galaxies are it's between the galaxies It's where as nothing is shining About 50 times as much mass in this system, and in all systems we can measure comes from stuff that doesn't shine and physicists with their linguistic perspicacity have called it dark matter and we now understand that 90% of the mass of Galaxies and clusters Including [our] own milky way Galaxy is made of stuff that doesn't shine and that Isn't maybe that exciting because there's lots of things that don't shine you don't shine if I turn the lights out while those of you from Los Alamos might get the rest of you don't but the So it could be snowballs or planets or boring stuff, but it can't be because for reasons I don't have time to explain [we] know how many protons and neutrons are [in] [the] universe? We can actually measure that and there aren't enough to make up all this dark matter So we are pretty convinced that that dark matter is a new type of elementary particle something that doesn't [normally] exist on Earth and The great thing about that is [that] means the dark matter isn't just out there. It's in this room as you doze off [that's] early in the morning during this lecture It's going right through your body and that means we can do experiments here on Earth to look for it Which is remarkable and in fact there? I think I think well. I'll show you an experiment in a second, but By measuring these the masses systems and lists [dark-matter] Taking normal matter [+] dark matter and weighing it. We now have determined How much stuff there is in the universe when physicists have an important number? They give it a greek letter all the time, so we call it omega omega is the ratio of the total amount of stuff We know is in the universe divided by the amount of stuff [you] need [to] make a flat universe the boundary between an open and closed universe if it's less than [1] the universe is open if it's greater than 1 the universe is closed and We have now measured unambiguously that there's only 30% of the amount of material [in] the universe including dark matter to make the universe flat Ok we'll come back to that in a second [light]. I just want to show you that we actually do things in physics This is an experiment to look for Dark matter. It's a pool [of] germanium And [they're] experiments like this all around the world in [minds] deep underground because you want to shield out cosmic rays because They'll there are lots of them going through your body right now You want to only see the dark matter and the dark matter particles on average will go right through the Earth We think because they don't interact strongly and most the time right through this detector But every now and then one of them will bounce off an atom the nucleus of an atom of germanium Heating and the first thing. We do is we cool this thing down to one one thousandth of a degree above absolute zero which can easily be done Nowadays and if one of these dark matter particles bounces off this a nucleus of an atom [it'll] heat the whole thing up by one one thousandth of a degree and We can measure that and their experiments here in South Dakota in in in Europe all over the world looking for Dark matter We haven't found yet the other exciting possibility Which I should really indicate which is one of the reasons people are very excited this year is we may not have to wait for The universe [to] give us Dark Matter the large Hadron Collider Which is turning on this next month in Geneva before it creates a black hole that [will] kill us all is We think [actually] might by recreating the early conditions the early universe? Create the very particles which were last created at the beginning of time So we may first see the dark matter by creating it in Geneva. It's a race Okay, but to go back to this this number here. This is a real problematic number We now know the universe has only One-third the amount of matter to make it flat the problem is the theorists like me knew the answer The Universe must be flat Why? Well [there] two reasons. There's one. I normally say which is it's the only mathematically beautiful universe Which is true, but there's another reason. I don't usually say it talked about but I'll talk about here It turns out that in a flat universe the total energy of the universe is precisely zero Because gravity can have negative energy so the negative energy of gravity balances out the [positive] energy and matter What's so beautiful about a universe with total energy [zero]? well only such a universe can begin from nothing and that is remarkable because The laws of [physics] allow a universe to begin from nothing you [don't] need a deity you have nothing zero total energy and quantum fluctuations can produce a universe, so [if] the universe isn't flat we're worried because then you've got energy at the very beginning of time So that was another reason that people like me were pretty sure the universe was flat But the damn observers came up with the wrong number Well, this is a really crummy way to measure the curvature of the universe if you want why don't we measure it using geometry directly? so we Can measure the curvature of the universe? and to [do] that I want to ask you how would you measure the courage of the earth if you couldn't go? Outside the Earth and see it from a satellite Or you couldn't go around it [very] [simple] you draw a triangle and you [ask] a European high school student. What's the sum of the angles in a triangle? and and That will tell you 180 degrees, but you say that's fine. You learned your geometry from euclid, but [on] us on a curved surface It's very different on the surface of the earth. I can draw a triangle. That's very different I can go along the equator [I] can make a right angle go up the north pole make another right angle or come back to the equator and I have a triangle with [three] right angles three times 90 is 270 So if I made a big enough triangle on the surface of the Earth [I] could measure the curvature of the Earth I Wouldn't have to go around it now it turns out even though. This is a [two-dimensional] picture The same is true for [three-dimensional] curved universe if I had a big enough triangle and I measure the angles in a triangle I could measure the curvature of space and We've been able in the last decade to find a big enough triangle and I want to spend five minutes telling you about that because it's the most important probability observation in all of cosmology the observation of the Cosmic microwave background radiation the afterglow of the Big bang One of the many reasons we know the big bang actually happened What do we do when we [look] out at space? We look at galaxies that were say a billion [light-years] away, and they're a billion years ago But if we know that universe is fourteen or thirteen point seven two billion years old if we look far enough We should see the big bang right Well, we can't see all the way to the big bang because between us and the big bang. There's a wall So like this wall here Not really hard like that But the fact the walls opaque means I can't see past it If I go looking back in the universe it was getting hotter and hotter and hotter and at a time when it was a hundred Thousand years old the temperature of the universe was three thousand degrees warm slightly warmer than Phoenix this week and at that temperature the [radiation] is hot enough to break apart atoms hydrogen in particular and break it apart So the protons electrons are separated you have a charged plasma and a plasma is opaque to radiation So we can't see back will past this time simply because the universe is opaque But that's [ok] the reason [I] can see that wall Is that is it is that light bounces from those lights there off the [atoms] on the [surface] of that wall is? Reradiating but the air is transparent so [I] can see all the way to the wall If we run this foam forward as the universe is opaque opaque opaque and then it becomes neutral The atoms protons capture electrons neutral matter is transparent to radiation like this and that means I can see all the way back to that radiation coming at that surface a Prediction of the Big bang is there should be radiation coming at me from all directions? Coming from that surface called the last scattering surface It was 3,000 degrees then it's 3 degrees now, and it was the radiation that was discovered by accident in New Jersey of all places by [2] people who didn't know what the hell they were doing and They won the Nobel prize anyway Because they discovered the [afterglow] began actually another aside I can't help with this because this is amazing and if you ever want to convince kept you won't ever convince people of this you don't believe it anyway, but You've all seen this radiation at least those of you are old enough to be as old as me before cable TV remember when the TV stations used to end and Then they'd be static one percent of the static on Your TV screen is radiation from the Cosmic microwave background So you've all seen it [ok] but it's amazing we didn't even know about it till 1965 ok It was a in fact had been predicted by people like George Gamma But people have forgotten that in a case as interesting is that history is on this surface is a very important scale one degree Why one degree? Because that represents a distance of a hundred thousand light years Now the surface existed when the universe [was] a hundred thousand years old and einstein tells us no information could propagate faster than light So that means nothing that happened over [here] at that time could ever affect anything that happens over? But more importantly if I have a lump of matter, that's this big it knows it's a lump of matter so it starts to collapse But if I have a lump of matter, that's this big across at that time, it doesn't even know it's a lump because gravity can't have traveled across it so It's like [wiley] coyote and those cartoons when he goes off [the] cliff He waits a while before he collapses okay, and this as such large lumps won't collapse So the biggest lumps that can have collapsed at that time will be one degree across and that gives us a cosmic triangle Because we have a ruler that's a hundred thousand light-years across the size of the largest lumps a known distance away from us and in a flat universe light rays travel in Straight Lines And we can calculate the angle on our ice obtained by a hundred thousand light year across Ruler at that distance. It's 1 degree in An open universe light rays diverge as you go back in time And the [whole] thing might be half a degree the ruler will look smaller In a closed universe light rays converge as you go back in time the ruler will look bigger so we just have to look at that microwave surface try and measure the lumps and See how they [1] degree half a degree or [two] degrees we've been able to do that in the last Decade this was the first experiment that did it was a called the boomerang experiment in antarctica. It was a it was [a] Balloon took this microwave radiometer above the Earth's surface [to] [look] at this radiation Take a picture of it and this balloon went around the world which is easy to do in antarctica Okay, and it took a picture. It's really easy in the south pole. You just do this, but anyway and This is the image well, this is a false color image of that. I put it a super imposed on the original image This is the image Of the microwave background the hot spots and cold spots the microwave background and these are the lumps in the early universe and the question is how big are they and Here's a different false color image of the same region, and we can compare this with universes. We create a computer's Here's a closed universe where the lumps are bigger They should be this big across there 100,000 [light-years] across that you look that big well, that's bigger than these lumps Here's an open universe, and you can't see the resolution the screen is not good, but the average [sized] lump is about that big smaller than these lumps but just like goldilocks in a flat universe It's just right In fact it's right now we know to an accuracy of [better] than 1% The Universe is flat it has zero total energy, and it could have begun from nothing and I've written a piece although of course I got a lot of hate mail Saying that in my mind this answers this crazy question that religious people always keep throwing out which is Why is there something rather than nothing? The answer is there had [to] be if you have nothing in quantum mechanics. You'll always get something It's that simple. It doesn't convince any of those people, but it's true now Great. We know the universe is flat, but if you've been awake you rely ten minutes ago. I proved the universe was open There's only [30%] of the stuff in the universe needed to make it flat where is that other 70%? well if you put energy in empty space So empty space weighed something you wouldn't see it. It's the empty space between the galaxies You're far away from the galaxies. [you] wouldn't see it But what would that empty space do if you put energy in it well? It produces a cosmological constant that would cause the expansion of the universe not to slow down over time as any sensible universe should do But to speed up over time in 1998 people measuring [these] Supernovae at large distances to measure the hubble diagram Tried to see what was happening at large distances to see if that if the universe was slowing while they all knew the universe was Slowing down they wanted to measure how much? This doesn't look like much, [but] it was a revolution in cosmology [I] can I can draw a straight line through [that] data set there and bring the whole thing down and make it horizontal And if the universe was slowing down these distant Supernovae should have followed this curve Much to the surprise of the observers the Supernovae Lie above a straight line and The [only] way to explain this well. There's two ways either the data is wrong. Which it usually is Or the universe is accelerating speeding up And if just for fun one believed it was speeding up and asked how much energy would you have to put in it empty space? To make it speed [up] by the amount we measure it It's exactly the amount we are missing Everything holds together our new picture of cosmology is that we live in a universe? dominated by nothing the largest energy in the universe 70% of the energy in the universe resides in Empty space and We don't have the slightest idea. Why it's there now That's what I just said Let me also put an aside before I get [onto] the rest in the last five minutes of the time This completes in some sense the ultimate copernican principle Copernicus told us we didn't live in any place special We now know Two things [well] one thing I'll tell you the second one in a second This tells us that we are a more insignificant than we ever imagined if you take the universe Everything we see stars and galaxies [and] clusters everything. We see if you get rid of it The universe is essentially the same we constitute a 1% bit of pollution in a universe that's 30% Dark Matter and 70% Dark Energy We are completely irrelevant Why such a universe in which? We're so irrelevant would be made for us is Beyond me Okay good. [I] want a little bit of applause now we can go back to the signs What what it really what I really want to spend in the last few minutes is telling you is that I was changed our picture of the future in science and the picture of the universe it has changed our picture of the future completely and I'm going to I'm going to rush through this so let me give you the short answer first This Kurt vonnegut is claimed as having said this at a private girls school when he gave a commencement address I've given two commencement addresses I've never had the guts to say it, but I'd love to he said things are going to get unimaginably worse And they're never ever going to get better again this was before the bush administration [too] in fact but but the the But that's art [that's] our [understanding] your universe. I want to tell you about it briefly [I] want to tell you about a few things that you'll hear about and some of the things that creationists and intelligent design people Promote as arguing somehow that there's design in the universe This is one of them, and I want explain you. I had nothing to do with design It is weird and strange That we live [in] a universe that looks like we do because this is a brief history of time This is the density [of] matter as the universe expands it goes down as one over the volume But it turns out the energy density of empty space remains constant as universe expands And we live today right here when the energy density of empty space is three times bigger than the energy density of matter? But when you look at this this is driven, physicists crazy because This is the only time in the history [of] the universe when these two numbers are about the same at All earlier times the density of matter was much greater at all later times the density of Empty space will be much greater Why do we live at this special time in the history of the universe? Well the answer that one of the answers has been given is that these things exist galaxies Why well let's go back to this picture and let's pretend the energy of empty space. We're 50 times bigger then these two curves [would] cross not now, but then Well when is then in this case, then is what time when galaxies first formed? But if the energy of empty space was bigger than the energy density of matter when Galaxies first then the repulsive force Would be greater than the attractive force galaxies would never have formed well if galaxies never formed Then maybe this is telling us something and this is reproduce something that I call anthropic Mania If there are many different universes people at physicists have argued and the energy of empty space can vary in each one Then only in those in which it's not much greater than what we measure today will galaxies form okay? but then only then will stars a planets form and only then will astronomers form So the universe is the way it is because astronomers are here to measure Now it not only sounds ridiculous, but it also sounds religious and some people have said the universe is fine-tuned if It were any different than we wouldn't be here. God clearly created the universe to be for us Now that's nonsense, and it's nonsense for the same reason that You learn so beautifully in Richards books why can bees tell the colours of flowers so they can find them? Not because God intended them to do it but if they did if they couldn't find the flowers they wouldn't get the stuff they needed to eat and they wouldn't be around it's natural selection and What risk is really telling us is kind of a cosmic [natural] selection Because all it's saying if it's true is that it's not too [surprising] that we find ourselves living in a universe that allows life Because of the universes that don't allow life we wouldn't be here It's just that simple so if you wish it's a kind of cosmic evolution Or cosmic natural selection is a better way of thinking about it. Now as pretty as [that] is I think it's wrong It's ugly and it goes against everything I think about 9'o about science science has told us the last 400 years why the Universes must be the way it is not why has to be something different In fact Einstein once asked question. He said it the wrong way put it here because He well, I wanted to quote him. He said what it really interests me is whether [God] and by God he didn't mean God Had any choice in the creation of the universe What he really meant to are the laws of physics fixed so that if you changed one parameter the whole you couldn't have a universe or Can you have infinite numbers of different laws [of] physics that all work and it just happens to be? The way it is if this anthropic picture is right then physics is really an environmental science Where there's no fundamental laws necessarily? We're just here by an accident and the laws of [physics] are the way they are not because there's some beautiful Mathematical theory that tells us they have to be just because if they were different, we wouldn't be here Now that I found I find her pugna although it may be true, and I was going to spend time telling you about That but I'm really behind so maybe I shouldn't There let me just say that there is a theory that That suggests. [I] mean in such a picture if They're an infant number of universes then you don't need a theory of everything forget what I wrote there You need a theory of anything you just need an infant umber of universes and some theory that tells you anything can happen We have such a theory, and I didn't want to spend one minute telling you about it's called string theory Here's that here's the brief summary of it one person said [to] another I just [had] an awesome idea suppose all matter and energy is made of tiny vibrating strings the second guy says, okay? What would that imply and the first guy [says] I don't know so that's that's a history [of] string theory in the last 25 years and The point is it it is fascinating for many people, but one of the things it might predict Is that anything is possible, and if anything is possible? [it's] not clear you have a scientific theory at all But now I'm going to skip forward in the last minute. I had a good art joke about George bush, but I won't give it And I'm going to skip this I'm going to skip this forgive me it's really interesting, but I want to get to the very end which will really tell you about how miserable our future really [is] and It should put us give us a kind of cosmic humility. Which is the other thing that is I should be characteristic of science A Humility the recognition that we don't understand [everything] bill Maher talked about it last night what? Pompous assholes like Rick Warren who claim to understand everything are in anathema to science We should realize that that withers more we don't understand about the universe Than we do and I want to give you an example of this the far future What's going to happen in the far future remember a hundred years ago? We thought we lived [into] static eternal universe What will the future bring the amazing thing is? For civilizations that live in the far future, what will they see? Well the universe is accelerating that [means] all the Distant galaxies are getting carried away from us and eventually they'll move away from us faster than the speed of light It's allowed in General relativity They will disappear the longer. We wait the less. We will see in a hundred billion years any Observers Evolving on stars around our and there will be stars Just like our sun in 100 billion years any observers and civilizations are evolving around those stars. [we'll] see nothing except for our galaxy Which is exactly the picture they had in 1915 all evidence of the hubble expansion will disappear Why because we won't see the other galaxies moving apart from us So they will have no evidence [in] fact of the big bang. They won't see the hubble expansion They won't even know about dark energy, and I won't go into [that] They won't know about the cosmic microwave background It will disappear too. It will redshift away, and it turns out for Fancy reasons A plasma in our Galaxy and when the universe is 50 times its present age the microwave background will be able to propagate in our Galaxy [all] evidence of the big bang will have [disappeared] and those scientists will discover quantum mechanics discover relativity discover evolution Discover all the basic principles [of] science that we understand today use the best Observations they can do with the best telescopes. They will build and they will derive a picture of the universe which is completely wrong They will derive a picture of the universe as being one Galaxy surrounded by empty space that's static and eternal falsifiable science will produce the wrong answer in Fact I want to end with the good news We live in a very special time The only time we can observational e verify that we live in a very special time Okay, it's clear. I'm I'm clear I'm being facetious What it really should tell us is we have discovered this crazy picture of the universe That we don't understand at all it all holds together, but maybe [we] [have] evolved five billion years earlier there would have been observables We could have seen it would have [changed] that picture. Maybe five billion years in the future, it'll be different the Universe [remains] mysterious and that is great But I do want to say in the far future This is the picture We will be lonely and ignorant but dominant and those of us who live in the United States are used to that Let me let me end ok that's the end. Thank you Thank you On the one hand the woody allen of cosmology We've been privileged to hear and Witness the scientific mind at full stretch in all the excitement that it can bring and I'm delighted that we've had that this this talk today What grieves me is that at least in Britain and it may be true here as well young people going to university Are voting [with] their feet and not going into physics. They're going into media studies Despite the enormous excitement that is in physics and cosmology [despite] the fact that as as lawrence said the large Hadron collider is even now about to Revolutionize the way we think about ourselves There was a misprint in my book just finished the greatest show on Earth [I] Refer to the large Hadron Collider it got rendered as the large Hard-on Collider That's okay. That's okay because that's what physicists are getting right now. Yeah I am I spotted it, and I prayed that the Publishers Copy Editor the Publishers proofreader wouldn't spot it and she did and I pleaded with her to leave it in and she said it was more than her life is worth, so [Lawrence] thank you. We have a few minutes for questions Well, I think we do I mean it actually it's cutting into your book signing. Which we're all the paper I'd rather answer question okay? I'll be around all day, okay Well the question was are people who involved in general relativity more religious than other scientists which apparently Steve said in when Richard and he had a darling I've no memory [of] him saying that yeah, that's great and There are some great interviews you should watch of Richard one that was with me, but anyway um we had fun [uh] I Think that no. I mean there are a few there's a famous general relativistic. Who's now unfortunately command not named Frank tipler Who's [uh] who I've actually debated a [cow] right near here at Caltech a Few years ago And there are some but I don't think that's true in general. There are a few. There's one or two I I don't think there's any evidence of that. What is true and is interesting and I think I will answer in a more relevant way Is that general relativity unfortunately gives people the wrong idea about science and unfortunate I get a lot of letters from Crackpots because of it Everyone imagines Einstein sat in a room closed doors and thought of this picture and came up with this beautiful theory Independent of reality like string theorists okay, and And the answer is that's not true at all Einstein was guided by experiment Was guided deeply by experiment not just the thought experiments He did in his mind, but if you read what Einstein said after [he] general developed general relativity, okay? one of the first calculations he did was the was the orbit of mercury around the sun and the Orbit shifts a little bit this perihelion moves, and no one understood. Why that was and he said he calculated that What should happen general relativity it moved and it moved by exactly the right amount and he said his heart he almost fainted because that was the moment that he knew was the right theory and so it's not as if scientists are out of touch with experiment and come up with pictures like religion that are just beautiful that they [believed] because of their intrinsic beauty as Beautiful as general relativity was Einstein would have throwed it out like yesterday's newspaper If it had come up with the wrong answer for the [Parallel] [yin], work Yuri [my] question is probably easily answered but if Quantum fluctuations are able to actually produce universes Even that even though that may be extremely unprofitable [is] there ever a chance we might actually observe another universe being created? That's [a] really good question people wonder if you well actually is one of the questions people worry about with the large Hadron collider maybe you'll create the scenery and Whether you can create baby universes the laboratory is still an open question There's lots of evidence that suggests you can't you can't actually physically create the energy conditions necessary, but we don't know for sure it's one of these open questions [and] people like me get paid to think about but but interestingly enough, and this is one of the wonderful things about general relativity is if a baby university if a universe got created an inflating universe like the one we think we we began and It's really weird because from the inside it would look like it was growing exponentially From the outside it would look like we're shrinking to form a black hole So it's not so clear that we would know about that, okay now We do think in the current picture of the best picture of cosmology involves something called inflation right now And it suggests [that] Our universe that we see is just part of a multiverse in which there are other regions where there may be universe is [just] being Created now, but because those regions are literally moving away from us faster than the speed of light We will never know about them in periodically So it's not as if those inflating universes collide as fast as they expand the spaces between them is expanding faster and so unfortunately these are right now some sense metaphysical pictures and What we want to do is learn enough about the fundamental physics at places like large Hadron Collider to know if there are other Observable implications that We can measure just like we believed in atoms a long time before we saw atoms because all the other implications Agreed with experiment, so it may be that we never know about those other universes Directly, but we have a theory that tells us that explains the mass the proton the mass of the electron But it also tells us that those all the universities exist. We would be willing to accept them without seeing okay. Thank you sure Take a few more okay? Hi, hopefully. There's no stupid questions. So they're all stupid. I [mean], how do you wrestle with? Infinity for example. It seems like all your your Thinking and what laws but it has to do with [a] finite [amount] of matter [you] [were] talking about [multi-use]. Yeah, sure but [in] my head, but there's just one [universal] all those multiples well in a flat universe It's infinite in spatial extent right, huh infinity is a really hard thing to wrestle with yes, and in fact Let me give you I wrote in one of my books. I wrote about infinity because it's so fascinating and so weird the only way you can wrestle with infinity is unfortunately the [way] we physicists wrestle with many things mathematically and fortunately or [unfortunately] mathematics is the language of Nature and Therefore every time I give a talk or write a book I have to lie a little bit Because I put it in words the real explanation is mathematical, but infinity is so strange. [you] don't have any idea How strange it is so let me make it clear to you? How little you understand infinity, okay? No profit of a very famous Mathematician called Hilbert very probably the most famous mathematician in the early part of this century he almost discovered general relativity before Einstein Hilbert gave an example [he] [called] Hilbert's hotel, and I like to use it So let's say you go to las Vegas, and there's an infinitely big hotel ok and you go in and and and you're going to say I want a room and The clerk says well all the rooms are occupied Say ok I'll leave and said no no no I can like it's ok I can handle that here Let me [just] move the person from room number [1] in to [room] number 2 The room number 2 into room number 3 room number 3 and room number 4 and so on now all the other rooms are occupied But room number [1] is empty [ok] That seems a little strange, but let's take let's say you have a catholic family that's infinitely big And you go to the hotels I've got my infinite number of children here. I want to check in He says well the rooms are occupied Then you go ok no, no I can I can handle that I can handle your instant family even though I'm fully booked. [I] have an infinitely big hotel I move someone from room number one and room number to room number two into room number four room number three in the room number six and so on and now all [lean] even numbers are occupied and All the odd-numbered rooms are empty. So you have an infinite number of those so you see infinity working with infinities is really weird because adding and subtracting infinities produces strange things and unfortunately in physics we have to learn how to deal with that the universe may be infinite and There are many strange things one of the most ridiculous Unfortunately which I go to physics conferences I was just the one in France and this was talked about is if the universe is infinite and infinitely long old Then there's a puzzle We're here because we evolved but that makes us very special apparently because [if] the universe is infinitely big and in fully old quantum fluctuations will produce this room with all the people in it having all them having everything is exactly the same and incident number of times So we should be in this room, and [I] know it seems like it's taking infinite long amount of time But we we should be in this room, but most of the time We should never have evolved But we evolved That's cause some physicists to worry. I think [it's] a ridiculous. Worry frankly because in fact I Mean I hate to do this I'll answer your questions in Private later But zack because I want to let people you know go pee and stuff before the next thing But let me just say [too] close because probably this is the most important Moral of infinity And it comes from Richard [Fineman] who I've just written a book about Richard Findme used to go up to [people] all the [time]. I mean say You won't believe what happened to me today. You won't believe what happened to me and people [say] what he'd say absolutely nothing because we humans believe that everything that happens to us is special and significant and that And that carl sagan wrote beautifully about that in demon-haunted world. That is much of the source of religion [ok] We everything that happens is unusual and unexpected Likelihood that Richard And I ever would have met if [you] think about all the variables the probability that we [are] in the same place at the [same] Time a breakfast of the same whatever if you apply, it's zero Ok every event that happens has small probability but it happens, and then when it happens if it's weird if you dream 1 million nights and you Nonsense but one night you dream that your friend is going to break his leg and the next day breaks his arm ah Ok so the really thing that the the physics tells us about the universe is it's big rare events happen all the time including life and That doesn't mean it's special. Thank you very much Thank you, Lauren for wonderful you
Take a moment out of your day to watch this, words cannot do this video justice.
Wow...I'm gonna get high and watch that again.
"...so forget Jesus, the stars died so that you could be here today"
This video is life changing, maybe not really that extreme but it does break down what we know to be true from observation and separates all the fancy theories and quantum mumbo jumbo the average person doesn't quite understand.
Really great video, that hour went by pretty fast.
Awesome, I was just thinking "damn, here goes an hour" but I've already seen it. :D great lecture. Love Krauss
This is fantastic, thanks for this. Can anyone suggest any more talks like this? (Really clear to the layman yet fairly cutting edge new stuff)
Everyone should watch this. Once sober, once with the mind opening possibilities of dear old cannabis.
Knowing a billionth of nothing is better than believing 100% of nothing. HookLifestyle, you will never know how much your post changed me...and I'm a physicist and teacher.
Its like humongous big