Public Lecture—Our Lopsided Universe: The Matter with Anti-Matter

yeah good so good evening ladies and gentlemen I'm delighted to see such a full auditorium on such a warm beautiful summer's evening so but I'm not surprised because tonight we have a draw something which you won't forget this is the third of our public lectures the first two in fact the tonight's public lecture is a lecture really about contrast it's about matter and antimatter two extremely different varieties of matter this mirrors the public lecture series we've been giving so far because the first two lectures were given by dr. Hermann Winnick myself both of us gray bearded and holding tonight we have the other extreme we have Steve schooler who as you see is young and also wears a tie which is something quite rare on the good he's off to a great start Steve is one of our stars here at slack he has just finished his doctorate he was awarded in March I think this year he's now at MIT Massachusetts Institute of Technology continuing on to do a postdoc job there and I'm sure he's got an extremely bright future ahead of him in the world a strange world of particle physics steve has worked at sac for for some time and during that period he was one of our star guides and helped us a lot showing people around so I'm delighted tonight to be able to pass over to Steve schooler who's going to talk us about the lopsided universe thank you Steve it's my pleasure tonight to present to you a story about the universe as we believe that existed and as we know it now exists and our ongoing quest to understand the truth behind why the universe turned out the way that it did and that story begins with two ideas matter and antimatter now let me say first that this lecture is made possible by a number of things the Department of Energy the United States Department of Energy's Office of Science provides all the funding for all the research that goes on here so any of the research any of the technology you see here tonight that's made possible by you okay the folks of the United States Stanford University manages and operates the laboratory on behalf of the Department of Energy and so we couldn't be here either without Stanford University has provided so much over the years to make this a world-class facility I'm going to begin tonight with the first chapter of the story which is matter and antimatter and I can't go into this too far without giving you an idea of what these things are now matter is supposed to be a fairly familiar concept matter is what you deal with every day and so what you're made of it's what the earth is made of as what the stars are made of around here it's what the planets are made of as far as we know everything in the solar system is made for matter but it turns out that in the universe there's not just matter but there's also something which is exact intrinsic opposite and that is antimatter and this illustration here is meant to give you an idea of the symbology behind the concept of matter and antimatter yin and yang two opposites which you cannot have one without the other when they meet each other they destroy each other completely leaving pure energy behind it's the most perfect way to release energy that the universe has ever concocted now Albert Einstein can't give a public lecture without talking about Harvard Einstein we owe him so much Albert Einstein he taught us a great many things and one of the things that he taught us was a very simple little equation now I promise you this is the only mathematics I'll have in my talk tonight it's a beautiful equation and it's an equation that lets us relate to things which for the longest time science people believed were two completely different things solid matter mass m and energy something which is transferred between bodies and allows them to do work but it turns out that Einstein discovered that they are not different concepts that mass is another form of energy and that energy and mass are equivalent to each other and you can go from one to the other by multiplying the mass M by a very large constant C squared C represents the speed of light which is the fastest we believe anything can go in the universe now what this equation tells us is that you can take matter and you can convert it to energy and if you start with pure energy you can get solid matter out of it as long as you don't exceed the amount of energy you start with that's one of nature's little principles you can't get more than you put in Paul Dirac is another famous physicist and in many ways he is the father of antimatter he received the Nobel Prize in 1933 for his work with the electron near the electron is a tiny little particle that's found billions of them and billions of them in all of you they run around the outside of every atom in your body and they cancel out they have a negative electric charge and they cancel out the positive electric charge that is the product the property of the nucleus of every atom in your body now mister Dirac was interested in understanding the behavior of electrons as they're flying through space seems like a very simple concept but the more he worked with these ideas and the more he laid down his mathematics the more you realized that he had a little problem every time he tried to understand the electron he inevitably got this other particle that had an opposite electric charge when it met the electron on paper they destroyed each other and he thought well that's that can't be right he'd try to explain it away tried to explain it as the proton but it didn't work and years later in the late 1920s after he'd done his original work the opposite of the electron the positron the antimatter electron was discovered confirming his discovery that if you're going to study matter you have no choice but to also accept the existence of antimatter the matter the existence of one baguettes the existence of the other its opposite antimatter is not something which is that's unfamiliar to you I suspect yeah that's what I thought yeah your a lot of you are like me okay some of you may even own this book like me antimatter makes its face pretty well-known in popular culture Star Trek is a fantastic example of this hiia can't go anywhere in the universe without smashing hydrogen and anti hydrogen together to make an extremely hot plasma which you can pump to your warp coils warp the fabric of space-time and zip around the galaxy in 60 minutes okay this thing here that appears in the Star Trek next generation technical manual is a schematic for a matter antimatter reactor assembly where hydrogen is at the stored in a tank at the top and anti hydrogen at the bottom and they're pumped with magnetic fields to the center where they react and dilithium you know regulates the reaction and and boom they go off the power transfer conduits to the warp coils and off they go antimatter in this context is drama it provides a dramatic basis for the storyline and it all begins with engage anti hydrogen and hydrogen meet each other and boom off of the speed of light or faster as the case may be in Star Trek drama but there's more to antimatter in your everyday life than TV and fiction especially if you've read anything by Dan Brown lately if you've ever had a PET scan has anyone here ever had a PET scan before yeah one if yep two said if okay several people if you've had a PET scan you've benefited from antimatter a PET scan starts with the injection of sugar into your bloodstream now this is a special sugar the sugar has had atoms in its molecule replaced with radioactive versions of the same atoms your body needs sugar so it starts to distribute that sugar that's just been injected to parts of the body that require it these images here are regions of the brain that at the time when these activities were taking place like looking listening thinking remembering and working the brain needed sugar and so it took the sugar in and started using it up but because the sugars slightly radioactive when it that rating when it decays radioactively it gives off a little anti electron and that anti-electron doesn't get very far before it hits one of your normal electrons giving off to little photons to little particles of light the device that you're laying in at the time the PET scan is taken is meant to detect those little blips of light and tell exactly where in your head they came from or wherever part of the body they're scanning and so you can see here the red regions were hungry for sugar at the time that these images were taken and this is where the little bits of light were being given off and detected by the PET scanner positron electron positron emission tomography pet and one of the things I was asked to point out is that thinking it is a lot different from working okay and and hey mom and dad if you're listening apparently I am burning calories so now there isn't a whole lot of antimatter floating around on the earth which turns out to be a good thing because if there were we wouldn't even be here to have this conversation and that fat actually has deep implications for the universe as I'll talk about in a moment but if you want to use antimatter for instance to collide it with matter produce energy and study what comes flying out in the form of new matter equals MC squared you have to grow it yourself and the Stanford Linear Accelerator Center is one of the premier sites in the world for the production of positrons and their collision with electrons it begins here in this two-mile-long building which houses our microwave generators the microwave generators provide an accelerating mechanism for our electrons and positrons now what we do is we actually take the electrons that's all we start with and we slam them into tungsten metal now one of the things that Herman when it covered in his public lecture if you folk any of folks were here for that was that when an a charged particle bounces off of something it gives off radiation and equals MC squared takes over that radiation can turn into matter and in fact one thing that we've learned over the decades is that if you have pure radiation and it turns into matter it always produces matter and antimatter fifty-fifty every time now I want to illustrate this with a photograph a lot of people say that I'll get to this that in a moment a lot of people say that all particles how do you see these things on a moment you'll see how you see them these are minuscule little objects now to give you an idea of sort of that you know the utility of this slack has produced in 20 years okay point oh-oh-oh-oh-oh-oh two pounds of positrons if you converted all the energy in that time and turned it into electric electricity with no efficiency loss whatsoever you would be able to power a very low light bulb okay that's not going to solve any energy issues anytime soon but I'll tell you one thing it's more than enough to begin tackling questions about the origin and nature of our universe so how do you see these things there's a little story I want to tell you here these are this picture was taken with a device called the bubble chamber this is actually a liquid it's a liquid bath of hydrogen and what happens is electrically charged particles pass through the hydrogen it dumps a little energy into the hydrogen and causes it to boil or forms little bubbles in the liquid hydrogen and a picture is taken of that boiling process and you can see here the paths of electrically charged particles as they pass through the liquid hydrogen and were photographed by the camera now this photo was taken with a 40 inch bubble chamber that was running here at SLAC in the 70s and this photo was taken in 1971 now I I'm young I haven't had much experience with bubble chambers it's sort of an era that's a little before me so I spent some time poring through the Select archives trying to find some really beautiful photos illustrating photons turning into matter and anti-matter and I got a bunch of photos and a buddy of mine and I were sitting in the orange room here one night that's a conference room here at SLAC and we're looking through these photos and in walks a woman named sunny Parrish is she's just passing through she's going home for the night it's about 7:00 7:30 at night and she look to Kazaa ho bubble chamber photos I was a scanner here back in the day and a scanner these are the people that used to look at the photographs and try to identify the particles and the interesting events and all that was done by hand and I said well that's that's great she has what we were doing I told her we're trying to find some good photos and I said we're looking for production of matter and antimatter pairs and she goes oh no problem there they're there they're there and I'll highlight one of them for you so it was just this is one of these things I think everybody who's probably worked at this lab has had an experience like that where you're just sort of sitting along bumbling through not knowing what you're doing and someone walks in and unexpectedly has the answer you're looking for and in fact can tell you more than you really thought you'd ever know about these photos and I had that experience over the last week to meet with a lot of people who taught me a lot about this stuff now direct had a historical perspective which I learned as I was preparing for this lecture and I learned it by looking at his Nobel laureate speech from 1933 they have to read all this but the gist of it is as follows he says if we accept the complete symmetry between positive and negative electric charge similar to what I just said that whenever you start with pure energy you produce 5050 matter and antimatter we have to regard it as rather an accident that the earth is entirely made of a preponderance of electrons and protons and not their opposites also and so he speculated that it's quite possible that for some of the stars and by this I think he meant a great many other bodies in the heavens that in fact there may be half of each kind matter and antimatter now the signature for this would be quite striking we would look out at the Stars we would look at galaxies and we would see lots and lots of gamma rays resulting from matter and antimatter just destroying each other all the time from antimatter stars sprang off gas into matter stars planets colliding with other planets black holes gobbling up these things together and them just annihilating as they're coming in it would be a mess and there are number of the things you can look for out there that will tell you that it's 50 that there's 50/50 matter and antimatter out there but there's a little problem with that we just don't see it we've looked we've looked very far out into space with very sensitive instruments and we just don't see evidence in our universe well 5050 matter and antimatter from matter and antimatter cohabiting and galaxies it's extremely improbable that at the beginning of time they would have been thrown in completely opposite directions if you actually sit down and work those numbers out it's painful but it's it's extremely improbable now before I continue with this I want to talk a little bit about the nature of our universe its size distance scales time and what it means to be in this universe and to be looking out at the stars at night it's actually this constellation which was partly responsible for me getting involved in physics in the first place believe it or not I was actually going to be a novelist when I was in high school but I saw a special on PBS that kind of turned me around on this because it presented me with an interesting puzzle it said well let's consider the Big Dipper all right many of the stars in the Big Dipper are 80 light years away that means that it takes light 80 years to go from those stars to us on earth so we can see them light travels at 186,000 miles per second or 6 trillion miles a year let's put this on an earth scale if you have a beam of light that you could send around the earth it would go around the earth seven and a half times in a second extremely fast and that's the fastest anything can go in the universe that we know of what struck me about this was the following I will see the Big Dipper on the day as it appeared on the day I was born when I'm 80 years old okay that blew my mind that means that I'm seeing this thing as it appeared 80 years ago and I take a picture so who knows what it looks like now we have to wait 80 years to find out this universe is vast these are certainly not the furthest things away in fact we've looked out with telescopes back nearly 12 billion years and we can still see very young universes young stars now as he said earlier if there were 50/50 matter and antimatter cohabiting out there in galaxies we would expect to see evidence of them destroying each other all the time but we just don't and this is a real mystery because the best mathematical tools the best theories of nature that we have told us that it should be 50/50 the universe was created 50/50 and that's the way it should be today and that's a bit of a puzzle because those theories tell us a lot of things that are right but this thing is clearly wrong at least as far as we can see so we looked in many billions of light years in every direction and we just don't see evidence that these things destroying each other all the play all over the place certainly not even in our own galaxy so where did all the antimatter go something had to happen to it if the universe was created 50/50 and the stuff couldn't get far enough away from itself fast enough this universe would have self-destructed right away they would have been pulled back together smashed together boom no universe so what happened and this is a mystery which physicists here at slack and all over the world are engaged in right now trying to understand it with the best tools and talent we have now one of the interesting clues that we have from nature is that for every proton for the basis of every atom in your body there are 1 billion photons of light in the universe and that's an odd number why would that be that way well it turns out that if there was a lot of matter-antimatter annihilation at the beginning of the universe you could have produced a lot of photons that still be flying around today this image right here is actually really quite fascinating when the Big Bang occurred which is the theory we have now that we believe describes how the universe was formed after the universe started to expand it was a hot soup of its own building blocks so hot that light was trapped it would be emitted it would get stuck by another particle it would be emitted to another particle that we get stuck there it couldn't fly freely through space it just kept running into other really hot particles but over a course of many hundreds of thousands of years the universe cooled down and eventually hydrogen formed and the universe became neutral electrically neutral and when that happened light was free to travel as far as it wanted in the universe it was no longer getting hit by atoms that wanted to absorb it the universe had cooled too much at that point and that light has been traveling through the universe ever since the last echo of the Big Bang the moment light became free to stream through the universe and hit our eyes now currently the temperature of the universe is only a few degrees above absolute zero three degrees above absolute zero now absolute zero is the point at which all atoms in the universe stop moving it's the coldest anything can get and our universe on average throughout its entire bulk as far as we can see is only three degrees above that's very cold today this image was taken recently by the Wilkinson microwave and isotropy probe which is a satellite that sits far out in orbit around Earth is an image of that last wall of light that last burst of light that was freed from the Big Bang after after the universe was formed and much of this light we believe comes from originated in matter and antimatter destroying each other but if that were true they must not have destroyed each other equally there must have been an imbalance something which favoured matter over antimatter in this sort of cosmic galactic battle at the beginning of the universe what's going on is the universe lopsided in a fundamental way that somehow favors matter over antimatter and that's the question we've been trying to answer for several decades now but to answer the question we have a little quandary here if we want to keep looking out in space we're kind of stuck because at some point we're going to hit that wall the wall where light was no longer free to stream to us anymore and you can't see past that wall there's nothing to see light was not free to travel so what you have to do is you have to find a way to recreate the temperatures the conditions of the early universe in the lab to try to understand what was going on early in the universe millions and billions of a second after it was created now a famous physicist named Andrei Sakharov in 1967 he published a paper which turned out to be only a few pages long but is one of the most fundamental papers in physics in the last 40 years and in it he had gone through a great deal of thought about how one could get a lopsided universe what are the ingredients one would need in order to get the world the universe we live in today well first you need obviously some kind of imbalance between matter and antimatter they should have just destroyed themselves mutually and completely at the beginning of time you also need an abrupt change when the universe is very young sort of like a gas suddenly freezing into solid ice you need something which was so rapid and so sharp that it shocked the universe and kept these things apart from one another and in addition because we have an overabundance of protons which make up the atoms in our body there's a little catch in that they have to be allowed they have to be seen to fall apart at some point as far as we know right now the proton is one of the most stable particles in the universe your protons will never fall apart in your body which is good because if they were to do so all of a sudden you'd cease to exist now neutrons there they're slightly heavier cousin which are electrically neutral they fall apart all the time but protons protons are far we know are rock solid particles but he insisted well unfortunately if that's the case then we can't get the universe we we have today so something must be going on something must be fundamentally going on and what we're focused on here at SLAC is first ingredient actually going into the lab recreating conditions of the early universe and asking the question does matter get favored over antimatter early on when the universe is very young to answer this question we have to as I suggested go back toward the beginning of time as far back as we can at least as far as technology will allow us to go yeah sure you need all three in order to get it but the problem is do you have any one of them at all that we know of and that's not clear yet so the question was do you need all three of these in order to get a lopsided universe to get the leaners we live in yes to get it sorta lopsided you need you know one of them the antimatter matter imbalance is a critical one okay the universe is a bit lots of people talk about building time machines but it turns out that time machines have been around us all this time and I've already sort of hinted at that by talking about the Big Dipper and how you're seeing the Big Dipper as it existed 80 years ago you're seeing other things when you look at the meze existed millions and billions of years ago to try to solve this mystery with the considering the imbalance of matter and antimatter you have to go back in time beyond the sight of our most powerful instruments our most powerful telescopes and you have to study the universe at a very high temperature a very high energy I want to connect those two ideas right away so that it's equivalent to studying when it was young very dense packed a soup of its own building blocks and extremely high temperature right now we believe it's been thirteen point seven million years since the creation of the universe and we believe this on based on strong experimental evidence and the temperature right now in Fahrenheit is negative four hundred and fifty five degrees on average throughout the universe it's a little warmer here thank goodness but not out in space not out in space now at the time when the when the light was free to stream to us and become what is called the Cosmic Microwave Background this last echo of the Big Bang that was 380,000 years after the universe was born and that was at a temperature of 5,400 degrees Fahrenheit where we're going is before we're going to an era after this thing called inflation but a tiny fraction of a second a tiny fraction of a second after the universe was born when it was this dense soup of its own building blocks so what we do here at slack we collide matter and antimatter electrons and positrons fifty-fifty and the electron and the positron meet they destroy each other and they leave pure energy behind a dense little pocket of energy equals mc-squared takes over that energy is free to then turn into solid matter and we can look for that solid matter that comes flying out of the energy using powerful instruments called particle detectors the collider is what smashes the electrons and positrons together the detector is what looks for what comes out yeah what's that out of what okay so the question was out of what is that solid matter made energy and solid matter are the same thing you can almost think of matter as sort of extremely bound up slow-moving energy that's stuck in one point in space so the energy just in some sense condenses into solid matter with weight mass and then comes flying out and it's a process that we've actually shown you in a moment some some pictures of this happening hopefully in real time and this actually this image right here which is a static image but I want to show you some some pictures we're doing right now with our experiment this picture which is a picture taken by our particle detector called Babar and I'll explain that in a bit Babar took this snapshot what's going on is it coming into the screen and and going out of the screen are the beams of electrons and positrons and they meet every four nano seconds every four billions of a second right here at the center they annihilate each other and then what comes streaming out are other particles other building blocks sometimes their electrons sometimes they're heavier cousins of the electron like muons and Tau's sometimes there are other kinds of building blocks the stuff that rattles around inside the proton in the neutron clark's and they come flying out in pairs and triplets and slam into the instrumentation in our particle detector it's no different than your eyeball the reason I'm able to see you right now is because lights coming off the lights and the ceiling bouncing off of you it's hitting my eye my eye converts it into an electric signal which is transmitted to my brain and over the course of my life I've learned to interpret that as vision depth contrast color and so forth that happens all right away after you're born you can learn to interpret that right away we've taught our computers to interpret these strikes in the wires and strikes in their silicon and depositions of energy and their crystals and so forth as particles and we assemble that code information in the computer and we can make images like this of what's going on we currently at SLAC with our electron positron Collider we recreate conditions at a temperature of 120 million million degrees Fahrenheit that's one billionth of a second after the Big Bang so these could be termed we're not we can't get to the big bang that takes way too much energy but we can get ya in the neighborhood yeah if however the universe will tell you that you're not even close with this but it's more than enough to understand what the universe is going is doing at that time here's our particle detector this device and here's a person on the left here for for size reference okay this detector is called Babar I'll explain the name in a bit it's and it's a cylindrical arrangement sort of an onion skin layering of detector systems that are meant to look for different things all the way from the center of the collision all the way out to the outside until you get to these massive steel and and electronics chambers out here these structures on the left on the right are the doors that we closed while we're taking data they're open right now so that an access can be performed on the experiment and this is the machine that we use to take these images we have overlaid that image from the previous slide on here so you can see you know these these particles are really traveling far and fast and then they're being absorbed by our detector here and these green blobs are where they deposit lots of energy and I think what I'll do at this point is actually switch to the movie portion and give you an illustration of this this is a computer-generated image of this whole process of accelerating the electrons and positrons in the 2-mile linear accelerator feeding them off into our set of storage rings where we can actually store the electrons and positrons for our hours circulating around the Rings and every four nanoseconds they're brought into collision inside the bar and we try to capture useful images that come flying out of that so let me go ahead and play this and I'll try to narrate it as we go along here it begins with acceleration in our two-mile-long whoops that's interesting let's let's try that again okay well I guess there won't be a movie portion my computer is not behaving it's here let me try this again I may have to scram this but let's see yeah I apologize I apologize if I could get it up on there I would I'd show it so I know disappointment oh I can bring it up to the end and show it when there's a little more time I think you can learn a lot from a cup of coffee anyone who's in the back of the room here who knows me that guy right there for instance knows that if I have one vice it's that I love my coffee but it turns out there's a lot of physics in a cup of coffee not just the things I'm going to tell you here but also if you ever you know go to Starbucks or Pete's you know I don't want to or your your private coffee house everyone has their favorites and you get yourself a nice hot fresh cup of coffee and you're poor half and half 1% you know whatever you like into it you'll see that it looks like there's sort of a bouncy clouding going around inside of the the cup of coffee and actually that's a motion which is called Brownian motion that self mixing due to the the stuff the atoms bouncing around inside of the coffee and actually that turns out to be one of these fundamental things that Einstein taught us he explained what Brownian motion was and how it could be caused and it was more evidence for a solid footing for the atomic theory of matter it's all made of atoms and building blocks and so forth now if we were to zoom in a billion times into this little cup of coffee we would start to enter the realm of the atom itself and the atom would be a blurry racing shell of electrons zipping around its outside and deep deep down inside at the center of the atom would be a hard core called the nucleus the nucleus is made from positively charged particles protons and neutral particles called neutrons that are tightly bound together now one of the interesting things is that like charges repel and opposite charges attract so the electron is attracted to the positron stays in orbit around the electron is attracted to the proton stays in orbit around the proton where protons don't like to be near each other in fact these things are packed so tightly it's absurd that they're even staying near each other so there are forces in nature which are responsible for holding together the reality we call the universe the electrons that zip around the outside are responsible for you know the whole field of chemistry the way that they bond to other atoms and so forth the solidity of this table the solidity of any object is an illusion of the electrons repelling each other as you try to push your hand through the atoms in the table so solidity is a blessing of the fact that electrons just hate to be near each other now if you zoom in even further and a magnification factor of one with 13 zeros after it that's what this notation means 10 to the 13 is 1 with 13 zeros after it now you enter the realm of the of the atomic nucleus and here is a tightly packed arrangement of protons and neutrons and they are stuck together forming the core of the atom and if you go in even further one with 18 zeros after it you'll enter the realm of that of that which makes up the proton and the neutron the quarks for a long time we thought the proton and the neutron were the fundamental objects they were fundamental building blocks in the universe but experiments that were performed here at SLAC in the 60s and 70s illuminated the fact that the proton itself has structure the neutron has structure there's something rattling around inside of these and later we came to understand that these were what had originally been named quarks now a picture of the universe today is is fairly simple fairly simple the Greeks have us beat when the Greeks wrote down their you know four elements that make up the universe earth air water and fire that's about the simplest things I've ever been our picture of the universe today involves twelve building blocks six of which I've shown here and I'll talk about them in a moment and four forces that glue the building blocks together and weave the pattern we call reality solid universe our world around us the electron it's fairly familiar in fact the electron is something which you know every atom has it also has a little partner particle called the neutrino which has an extremely vanishingly small little mass we thought for a long time it had none at all just like the photon it had no solid mass to it whatsoever but recent experiments have shown us that it has a tiny tiny little mass and it has no electric charge and billions of these things are passing through your body every second and in coming from the Sun coming from electrically charged particles slamming into our atmosphere the electron has a heavy cousin called the muon it's a heavier relative and it lives for about two millionths of a second before it falls apart turns into other things its energy gets turned into other forms of matter it also has a tiny little partner called the muon neutrino quite often gets created along with the muon as a result of some heavier particle decay and then there's an even heavier one still another heavier covent cousin of the electron called the Tau the Tau is extremely heavy it's extremely unstable and it was discovered here in 1975 by doctors Martin pearl from slack and dr. Frederick Reines from UC Irvine forged work a discovery for which where they were awarded the Nobel Prize in 1995 and this along with the recent evidence for the tau neutrino which was postulated to exist but which only recently we've seen this completed this family of particles here called leptons the light little ones although these guys aren't so light at the bottom there are six more the quarks leptons and quarks are the two categories of building block the first row is the family that makes up the proton and the neutron neutrons contain one up quark and two down quarks and protons contain one down quark and two up quarks and those things rattle around inside the proton there are other relatives of these quarks however the charm quark which was found here in 1974 and also at Brookhaven National Labs in Long Island and that charm quark discovery in 1974 was a word of the 1976 Nobel prosit Prize in Physics to doctors Burton Richter and dr. Samuel Cheng from slackin MIT respectively the strange quark is a heavier relative of the down it was found in 1964 the top quark is the the heaviest building block that we've ever seen it's a single solid particle with a gigantic mass it's as if someone took all the mass of a single gold atom and compressed it to a point that's the top quark it doesn't live for very long and it was very hard to create and it was discovered in 1994 there's another another quark it's the second heaviest it's called the bottom quark it's another building block and it was discovered in 1977 and so far as we know there are only six of these and there are only six leptons no other in these categories have been discovered so far despite efforts to find them and the evidence that that led to the the interpretation of quarks as being the right thing to use to describe the proton a neutron that evidence was collected as I said in the 70s and 60s and was awarded the 1990 Nobel Prize that went to doctors Jerome Freedman dr. Henry Kendall and Richard Taylor from MIT MIT and slack respectively six and six interesting numerology and I guarantee you any one of you can figure out why that is Nobel Prize nobody knows why there are six of these nobody knows why there have to be six quarks why there have to be six leptons nobody knows if those are supposed to be the same number that's just something we don't understand about the building blocks of the universe although we can create them in the lab we can study their properties but we just haven't found any of their if they have heavier cousins we haven't found them we don't know why it ends at six so far there's more numerology here there's building blocks are useless without something to glue them all together house with no cement you're just asking for it okay well our house the universe is as far as we know held together by a variety of forces there are four of them that we know about gravity is the one you're probably most familiar with gravity is what keeps you from jumping and flying out into space it binds anything that has mass to anything else that has mass it holds galaxies together it keeps planets in orbit yeah responsible for the concept of weight another force that you're familiar with is electromagnetism it's carried by photons and it's the force that the electrons use to hold themselves in orbit around protons in the atom okay it's the same thing that gives you magnetism it's the same thing that gives you electricity this force is extremely powerful it's carried by photons the particles that love light and it binds anything with electric charge together chemistry's are a direct result of this force alone except for you attack in you need the fact you need a nucleus in every atom but as I said earlier protons in the nucleus don't shouldn't like to be that close to each other they've all got the same electric charge they should repel each other completely and we shouldn't even be here but thanks to a force called the strong nuclear force which overrides electromagnetism at short distances between quarks the nucleus is able to hold itself together first in two neutrons and protons and then they exchange forces between each other which stick the nucleus together into a solid mass and that results in the strength of the atomic nucleus so really critical force we wouldn't be here without it the least-known of these forces may be the last one the weak nuclear force and as its name implies okay weak nuclear force how important can that possibly be it's carried by very heavy particles which is why it's a weak it takes a lot of energy to create these things called weak bosons and it relieves to nuclear instability because what it does is it allows a quark of one type to become a quark of another type that makes neutrons and protons unstable if you do things like that so do radioactive decay which is the heart at the the process that's responsible for the burning of the Sun we wouldn't be here we wouldn't have the warmth that we do we wouldn't have stars without the weak nuclear force it may be the weakest of these except for gravity at large at short distances but it's extremely critical to the way our universe turned out today and one of the other neat things that we've learned is that at high energies it merges with electromagnetism to form a single force a single manifestation of an interaction between these building blocks called we call it the electroweak force the question is what happens you keep ramping up the temperature does the strong force unite with these does gravity unite with these we don't know the answer to that question either that's another Nobel Prize if you can figure out why that is okay yeah yeah what was that yeah sure so in order to transmit this force between one building block and another they have to emit a photon or a weak boson or a gluon that carries the strong force between them and that allows them to transmit information about momentum to each other so it's the particle that mediates the reaction between the building blocks without these particles you wouldn't be able to transmit the forces and the building blocks wouldn't know about each other at all they just fly freely through space and never talk to each other yeah the quarks are held together by the strong nuclear force so the strong nuclear force first binds the quarks in this case into triplets and then in addition it can also bind the nearby neutrons and protons together as well yeah yes right if a neutron suddenly one of the quarks inside of it changes it could turn into a proton that destabilizes the atom for instance yes exactly things like that exactly and in more exotic things bottom quarks be coming up quarks and so forth the fact that they can change between except that yeah that's a slightly did that isn't done by the strong nuclear force it's it turns out to be an intrinsic property of the neutrinos themselves very complicated to get into in short time but it's a little different than the strong nuclear force it actually winds up being related to the the behavior of the weak nuclear force in the end which is why it's so hard to observe it it's very rare I'm sorry I'm sorry I'm sorry I yeah you're right it's it's I'm sorry I miss I got myself confused between the strong and weak you're right the the weak the weak this is the same force that allows neutrinos to more from one type to another yes I'm sorry about that yeah I'm sorry I've got I've got this stuck in my head now so yeah it's so strong so the last chapter of this story is lopsidedness did we see it and i talked a little bit about the experiment that's been devised here in a complementary experiment that was also built in Tsukuba Japan to test for lopsidedness in the building blocks at the beginning of near the beginning of time what is Babar I've mentioned but bar several times here but what is it I've hinted it's a it's a particle detector but it's a little more than that it's a wonderful mascot this kingly elephant right here this is our this is our mascot with all rights reserved of course it's a particle detector I've shown you one end view of Babar but here's a front combined with a side view and a back combined with the side view here the positron is entering here and the electrons come out the front and the electrons come in the back and the positrons come out the back and they meet in the middle destroy each other and then hopefully we were able to take a picture of something interesting going on afterward these devices in combination with the particle collider that they reside on are referred to as be maison factories I'll explain what that means in a moment as well there are two B maison factories in the world that collide that that are built in similar ways to test similar ideas one is here at SLAC the other is that the KEK accelerator facility in japan and it's detector is called belt babar is also 600 physicists from 75 institutions in 10 countries it's a tremendous effort physicists engineers engaged I'm sorry this should be physicists and engineers I've just I've just I've just isolated a whole group of people I'm sorry I'm never gonna live that one down it's six under physicists and engineers to make sure that this experiment runs 24 hours a day 10 months out of the year except for shutdowns to do routine maintenance and to conserve electricity who do data analysis daily okay who put blood sweat and tears into understanding the nature of the early universe this is only a fraction of that 600 these are the people who are able to make it out during one of our collaboration meetings to get into the photo you see stragglers kind of running in from the bathroom and in addition Babar is part of what I call the slack of bee factory bee Maison Factory the bee factory is it's a combination of several pieces it's the two-mile linear accelerator from which we get our positrons and electrons it's a pair of storage rings that run here in a hexagonal configuration stacked on top of each other in one we store electrons and the other restore positrons we cross those beams in Babar bring them back out after wording we keep running them around the Rings and we can store these things for hours it's an amazing technical feat so we can use the same beams to keep recycling them and keep trying to bring them into collision collide collide collide and see what comes flying out and we currently have the world's largest database as a result of that CELAC houses a database which has hundreds of terabytes of data stored in at anytime and it's growing ever larger all the time and that's because what we do is we actually write out a hundred events per second from all of this we start with collisions there at 250 million collisions a second we skim out the interesting stuff the stuff we can get fast write that out to disk a hundred events a second and those are the events the physicists then go and pick through and look for the things they're interested in and what they're interested in in many cases is looking for B maisons that's why this factory was built this factory was built to produce particles called B maisons and I'll give you an illustration of what those are we actually produce with every collision one b and it's antimatter counterpart which we call the anti b Maison now physicists have this little notation where they take the letter that represents one particle and they put a little line over it a bar and that denotes it's antimatter counterpart so what we do it here is we produce B and B bar lebar that's where the name comes from what is a Maison I keep saying this word but what the heck is a Maison Amazon is a pair of quarks that's bound together by the strong nuclear force what I've Illustrated here is a massive bottom quark one of the six quark building blocks of the universe bound together with a Down quark it's an anti bottom quark and a down quark bound together to form what we refer to as the b0 Maison it has no electric charge so we put a little zero after it that's our Neutral B Maison so B Maison is any pair of quarks like this and we look for lopsidedness by making little universes that have 50/50 B and anti-b and then when they start out I mean actually go in and measure and see that they're 50/50 so we collide positrons and electrons they annihilate they produce energy little pairs of quarks come flying out of this they stick together and form B maisons which fly out from the collision point now this distance is exaggerated this is only two and a half human hairs diameter worth of distance so take two of your hairs take another half if you can do that align them up next to each other and that's how far these things travel we can see that we can see them fly that far from where they're created that's how powerful this instrument is the question we want to know is after they've traveled and after they fall apart to deposit their energy and other lighter particles that then strike our detector do you still have 50/50 matter and antimatter and the answer's no nature has a little bias in it nature when presented with 50/50 if you do enough times you'll find out that you dominantly wind up with matter coming out winning at the end of the equation you'll get rid of more antimatter than you get rid of matter you can actually run this experiment and do it go into the lab and do this test it and find out that oh my goodness nature has a bias built into it which means that in the very early universe this mechanism took over started to favor matter over antimatter and then when the mechanism was no longer in operation in the antimatter meant what was left the remaining antimatter met part of the matter they destroyed each other were left with a billion to one photons the protons in the end and that little piece of surviving matter is what we think was leftover to form the universe we just barely scraped by on that one okay why ah that's a good question we're getting to that okay that turns out to be a very tough question okay there are a couple of answers to that and let me get into that so this discovery made made headlines this is the New York Times article that was published when the announcements were made by Babar and Bell about their first observation of this lopsidedness using B maisons to study this now why is a very good question we start with Galileo I like Galileo Galileo was really the first person who introduced us to rigorous experimental science and he used the telescope as his instrument to understand to make sense of logical sense of the universe that he was presented with every day and he turned it to the Stars and he was the first person to observe that Jupiter had moons which is a tremendous discovery and similarly we use a tool a mathematical tool but a tool called the standard model to do the same thing to study things like be maisons and and other maisons like kay maisons pi maisons and so forth there's a whole zoo of these things the standard model it turns out does allow for a little bias between matter and antimatter but it didn't when we you know when these equations were written down it failed to tell us how much it was one of these things where you could actually see it in front of you but it was just a dial you could tune and you didn't know if that dial was zero or if it was set to a hundred percent okay you hope it's really big because it better have been big enough to get rid of enough of that antimatter well while we've discovered that that dial is not set to zero here at Babar and also at Bell striking evidence in fact time and time again that that dial is not zero it's not enough it's not enough to give us the universe that we have today it's not enough of an imbalance which tells us one thing the standard model which has been so successful at predicting so many things is not a sufficient description from nature it's not the end of the story we've been using it for decades now and it served us extraordinarily well but we started to go into the lab now with the intent of looking for places where it fails completely and this is one of them but we don't know why it fails completely because no other theory has been presented which can take up the slack and be a better theory of nature than this one string theory is something you've probably all heard of supersymmetry is something you've also probably heard of both of these allow for an even bigger matter antimatter imbalance in them but the problem is that while there they're neat mathematical theories they're great mathematical tools we've never found a way to actually go into the lab and test them now there are ideas in the next few decades to try to take some of the little predictions little I say things like extra space and time dimensions okay I guess that's not little but you can actually try to go into particle physics experiments and look for the presence of other spatial dimensions than the three dimensions we believe we live in or other dimensions than the time dimension we believe we're moving forward in okay yeah so in other words is it a relationship between the matter and the antimatter that tilts the scale in the end it actually turns out it's even more fundamental than a relationship between matter and antimatter this theory of nature has an built-in bias that immediately dials out the antimatter and dials in the matter so it's it's not that antimatter and matter colluded to get rid of one to get rid of the other in some way or that there was a that they influence that it could have walked to the other way as far as we know in this universe the scales were tipped one way and only one way and we don't know why but it looks like this universe wasn't an accident in that sense so yeah okay interesting okay well yeah yeah it's it's a it's a it's a it's actually one of the things I've found about the standard model when I was studying is it's a beautiful it's a beautiful mathematical theory the problem is it has a bunch of things in it that are not so beautiful yeah yeah okay I would I would I would worry that well I would worry so that the the question the point was made that the standard model is maybe a bit of propaganda that that it's not everything it's ballooned up to be and in fact what we've done is physicists or skeptics I'll be the first to admit that I was skeptical about the beauty and the power of the standard model first to the problem is we've been building experiments and running experiments for decades now and we've gone in and said okay the standard model predicts X do we see X and we see X out to five decimal places six decimal places which is the limit of our experiment that doesn't mean in the seventh decimal place the whole thing doesn't fall apart but we keep hammering it to see if it's nature's little propaganda right now in some sense yeah okay because everything else well well there what we've what we've learned especially recently there are a lot of things we don't know and I'm gonna talk about that in a moment the standard model is certainly not the be-all end-all theory of the universe although it's served as well this far it's served as well as far yeah okay the that's that's a okay the first of all the the force carriers themselves don't have anti particles because there's nothing to they are merely agents of a force so there's no anti force in that sense we don't know what dark energy is the question was it could anti gluons or something some anti force particle like anti-gravity for instance be what is called the dark energy and two things I'll say two that we don't know we don't know what dark energy is at all there are a lot of things that could be we have to go into the lab and test them to stay tuned in October I'm hoping you'll get to see a little glimpse of some of the current ideas that are behind what the dark energy and the Dark Matter will be and I'll put some information about that at the end yeah I said the universe this universe the fact that it seems to favor matter over antimatter it was tuned that way at the beginning but we don't know why so Dirac's notion was that well it must be an accident that here on earth we're all matter must be some other place where it's all an time there's an earth that's all antimatter our planet that's all antimatter and he said well you know could have gone any way it could've been 5050 we could have been made out of antimatter I think was is what he was saying there but in reality there's this in this built-in bias into the workings of nature that we don't understand we don't know why it's there we don't know why it's tuned where it is it but it's there and it does favor matter over antimatter so in some sense this universe wasn't an accident because something happened very early on to tune that number where it needed to be to get here I don't know why I don't know why that's it that's a tough question okay yeah right okay that's a good question if the bias were the other way around what would the universe be like it would be just like this one the trick with with ant like for instance if you have an antimatter star there's no way you can figure out that it's antimatter just by looking at it and in fact if everything around it is made of antimatter and you and I are made of antimatter we would call matter antimatter so it's a linguistic trick right that's that's the problem if you're in a universe where everything's turned around you don't know you just don't know okay alright okay oh yeah yeah there have been attempts and it the most successful so far we're making atoms of anti hydrogen but the problem is storing something like that is nearly impossible right now you need you need to keep it away from matter and it's almost impossible to do that yeah so yeah that's a good question though yeah yeah that's that's okay I now we're sort of bending toward philosophy yes in physics when you refer to nature you refer to that what you believe is that rational principle that you can understand that is behind all the workings of the universe that is nature we have yet to truly understand what nature's is at its heart and we may never but the whole point of doing these experiments is to see if we can understand it understand why the universe is the way it is it couldn't have been otherwise did it have to turn out this way and that's a lot of the rationale behind going into the lab and saying okay I've got a great idea let's test this and if the answer comes out Oh unsuccessful okay well that was clearly not right and you try again you try some other idea and this has been repeated for hundreds of years to build up what we believe we know now about the universe which may not be the end of the story in fact I hope it's not the end of the story I think there are too many things we don't understand for it to be the end of the story but but there's a lot of excitement in trying to go in and understand that rational principle behind behind the universe all right so I'm almost almost wrap up here and then those lots of time for questions right afterward we need something else to understand why the universe turned out the way that it did we need a better theory of nature we need to be able to go in and test that theory of nature put it to the task and say okay predict something ah you predict this let's go test it it's going to be a really oh it's going to be a while before we can actually start nailing down you know which theories are better than some other theories and so forth there are a lot of ideas out there about what could be the way that the universe really operates and it's impossible right now to discern between between which one's the better one which one's the right one the matter and anti-matter asymmetry seems to fall outside the realm of the standard model the standard model here is just not able to explain our universe and in a lot of other ways the standard model fails I don't want to get into those but recently we've we've we've learned even more about what we don't understand about this universe and I'm sure some of some of this I mean I've seen this on the news it was a scientific American frontiers episode very recently the missing portion of the universe recently we've really begin to quantify what we don't understand about the universe scientists are very good at conducting experiments which tell them how much they don't know but they don't know why they don't know it okay you can do this I'm not kidding it's not a joke it's it's really serious as part of the business is to understand what you don't know as much as you understand what you do know and what we found recently is that the universe is 94 95 percent stuff which falls way outside the domain of the standard model so-called dark matter and dark energy we don't understand what these things are but they seem to make up a large portion of the universe they seem to have allowed gravity to condense galaxies together they seem to be responsible dark energy now appears to be responsible we believe for pushing the universe apart faster than it's been moving apart in the past we don't understand that upcoming there will be a presentation in October on particle astrophysics which will talk more about the dark matter in the dark energy I would encourage you to stay tuned and come to that if you're interested I think it'll be very exciting and let me just wrap up here ok so there's what we do know is what we don't know ok I think what I want to press upon you is that great science is being done here we're really putting the known theories of nature the standard model to task we're pushing it hard we're trying to make it break in the lab now we know it breaks in very grand ways it doesn't explain the matter/antimatter of symmetry it fails to explain to us in a rigorous way with the origin of solid masses why do all the quarks have different masses why do all the leptons have different masses we don't know the quest continues to try to understand these things now in particular it seems that our lopsided universe is a result of something fundamental happening in nature a very long time ago not an accident as far as we know it's testable you can go into the lab conduct an experiment look for this lopsidedness and find it ok it didn't have to be that way it didn't have to be that way I could have been just been that we misunderstood the distribution of antimatter in the universe but there does seem to be a bias built into nature that prefers one over the other well what is this a result of what are we missing and this is where we need more ideas more fresh thinking and more experimentation to study those those thoughts to really nail this down if we can so to understand why we're really beginning to see that there's important reasons to connect the cosmic the grand the Galactic to the miniscule the particular particle physics high-energy physics and in particular physicists at slack and all over the globe are challenging these and many other issues and questions that have come up even in the last few months and years and so I hope that you will you know if you've been interested in this tonight that some of you will join us on this quest and try to test and push our understanding of nature to the limit in the hopes of one day making rational sense of the universe we live in thank you very much so Steve thank you very much indeed for this very illuminating but also entertaining talk then I don't think Steve is gonna have very much time to do physics going to be using all his time to give public lectures in the future please don't rush off home because outside we've got more real physicists who will be out there to answer any of your well not any question but specifically questions about physics any question you can answer and also you get a free coca-cola and some cookies so once again Steve thank you very much and let me just say that we upcoming in August 31st we've got metals molecules life and death understanding the role of metals in living organisms like ourselves and why they're a boon and a bane to our existence and how the Stanford synchrotron radiation lab is really trying to break new ground and understanding their role in life and then as I eluded a particle astrophysics lecture by Roger Blandford who heads up heads up or a carefully astroparticle Institute here a newly founded and that will be October 26th you can learn about I hope the connections between the mind you in a cosmic the connections were trying to understand and the ones we haven't made yet thank you very much

Channel: SLAC National Accelerator Laboratory

Views: 7,288

Rating: 4.5833335 out of 5

Keywords: physics, Department of Energy, accelerator, positrons, electrons, cosmology, dark matter, dark energy, Stanford University, science lecture, SLAC, atoms, subatomic particles, quarks, matter, antimatter, science video, physics video, high energy physics, particle collider, atom smasher

Id: mEympNqcBT4

Length: 66min 22sec (3982 seconds)

Published: Thu Jan 13 2011