The Mystery of Empty Space

welcome to Adams tax raise the series that brings you the wonders variety of research in physics chemistry and mathematics here at the University of California at San Diego this series has been developed so we can share the excitement of exploration and discovery and the promise which at discovery holds for our future a mark Siemens Dean of UCS DS division of physical sciences and I'm proud to dedicate this series to the memory of my friend and colleague professor Kent Wilson through his innovative approaches to learning and teaching can open new windows of understanding for all of science as well as for generations of students we hope we can open some windows to the world of the physical sciences for you too as you enjoy this edition of Adams to x-rays what I want to talk about today is the mystery of the importance of empty space the vacuum the voi nothingness of course philosophers have discussed and thought about nothingness for millennia what's kind of surprising is that modern physics has a lot to say about this subject and in fact what's also surprising is how important the subject has become this is a picture of the Keck Observatory on top of an extinct volcano Mauna Kea in Hawaii in this observatory astronomers are measuring the tiny flashes of light from distant supernovae supernovas billions of light years away and what they're trying to do is understand the vacuum what happens in the vacuum here here's a picture of of the CERN a particle accelerator near Geneva Switzerland that's a 15 mile long underground tunnel there and what the particle experimentalists are trying to do here is to create tiny ripples in space-time called Higgs bosons and the purpose is the same to understand what's happening in empty space so both those group of scientists have similar goals they are testing predictions of some absolutely bizarre theories of how what happens in the vacuum okay super string theory particle physics cosmology astrophysics these may seem like separate subjects but in fact the current theories have forced those theories together and if you want to understand Stan these things you have to work on both the smallest scales like we here the particle accelerator experimental stew and the largest scales so that's what I want to talked about today and let me start by talking about particle physics on the smallest possible scales one way of looking at what the goal of particle physics is is to understand what the most fundamental building blocks of nature are that's what they kind of do and over the years the method has stayed the same what you do is you take something and you smash it as hard as you can and you see what it's made out of okay so starting here you start with like a block of ice and you mash it and what you're going to get is water molecules okay no matter how hard you hit that with a sledgehammer you're just going to get water so you say okay ice is made of water but in fact if you then take those water molecules and you take some other instrument and smash them even harder you'll find that they break up into hydrogen and oxygen atoms and so you say okay that's the most fundamental thing atoms and this has been very successful for hundreds of years in fact and in fact all of the elements everything we see in the world in the world are made of the 92 elements of the periodic table so in one sense we could stop here and say okay we're done right everything is made of atoms okay but that's not really true because if you go back to the atoms and you smash them even harder with a more powerful Smasher okay they break up into protons neutrons and electrons and in fact we now know that everything in this room is actually made of protons neutrons and electrons that seems like a very simple place so maybe we should stop there it'd be nice to stop there but unfortunately or fortunately if you take your protons or your neutrons these are neutrons and you smash them together even harder and you can need this you need more and more powerful smashes to do that that particle accelerator I showed you in the slide is the world's most powerful Smasher okay what you find is that the protons and neutrons are made of quarks up and down quarks okay so this is this goes on and that's how far we've got so the question is can you understand the most basic building blocks and I'm not going to review all the particle physics but to suffice it to say that after decades now smashing and theorizing and synthesizing we are now in the position of having the standard model of particle physics in other words we have figured out what the most basic elements of matter are given the level of smashing that we can do and and this is it it's a it's a very successful theory it consists of some fundamental particles quarks up and down quarks and leptons like electrons and neutrinos they come in a mysterious triplicate of three generations no one knows why exactly that we'll get to that at the end it's a quantum field theory and the quantum field theory has symmetries in it that tell how to combine these together to make protons and neutrons and everything else we know those same symmetries associate with different force particles the photon is the force of electromagnetic we have strong forces those same symmetries say how these things interact and build everything else out it's a very complicated theory has lots of math but with this theory you can make thousands of predictions and thousands of experiments have been done testing it and in every case the theory agrees with experiment so whether you like it or not this standard model of particle physics is the best description we have of nature and it works so we are forced to kind of use this model by experiment that's how science works now you could ask if the theory works so well why are we still working so hard excitingly to build these particle accelerators and test this theory I said it worked in fact it's because there's a troublesome part of this theory and it has to do with this big Higgs H over here and when people first worked out the symmetries in this theory and how to use those symmetries to predict how things go together there was a troublesome point and the Troublesome point was that those same symmetries implied that every fundamental particle is massless has no mass okay now massless particles that exist particles of light photons coming out of the light bulb there are massless and of course it particles of light move at the speed of light in fact the what is the case is that any particle that's massless has to move at the speed of light ok electrons have a mass the atoms in my hands have mass and the reason I can move my my hand at a foot per second like that is because I have mass if I didn't my hand would have to move at the speed of light ok so the theory that the fundamental symmetries that make this theory work say that every particles massless sounds like a something terribly wrong with this theory so what to do about that well in 1964 this guy Peter Higgs and some of his friends came up with an idea a very possible but very weird solution he said it's called Higgs mechanism okay let's suppose the particles are massless fundamentally massless no mass okay but take the universe and fill it completely fill it with a quantum field a smooth field that acts to slow down the particles okay so it's kind of like imagining this room full of water and I move my hand and I have to move it through water and that slows my hand down okay so this is the idea of the Higgs mechanism the universe is filled with this all-pervading omnipresent field called the Higgs field if it wasn't for this field things would move at the speed of light in fact intrinsically that the electrons in my hand want to go at the speed of light but they can't because they keep interacting with this Higgs field okay so pretty weird pretty weird what makes a difference why are some things heavier than others well in this theory everything is massless pretty much except that heavy things interact more strongly like moving a pencil through water is easy moving a ping-pong bottleless ping-pong paddle is hard right so how heavy is something is in this theory it's just how strongly it interacts with this omnipresent Higgs field okay now can you feel this Higgs field I mean this is what the standard model says this room is filled with it can you feel it well in a sense you can feel it because otherwise your hands would be moving fast the weight that you feel is in fact interaction with the Higgs field so we are swimming in this visible invisible field now there are other invisible fields here right like the Earth's magnetic field is right here in this room you can't really feel it if you have a compass it would line up and you could do it the radio transmitters around San Diego are filling this room with electromagnetic waves you can't feel them right they're going right through your body but you take a radio in here and it'll move the electrons and you can pick up you could feel that those fields okay now and even the light coming out of this light bulb is in fact electromagnetic radiation ripples in that electromagnetic field but there's a big difference between these fields and the Higgs field if I turn off the lights if I turn off the radio transmitters if I stop the dynamo action in the Earth's center then in fact the electromagnetic fields will die away we have no electromagnetic field here the Higgs field is different the Higgs field is there even without sources you can't turn it off if you could turn it off everything would start moving at the speed of light okay so you can't turn it off so we say it's there even with no source it's a vacuum field it's there in absolutely empty space okay so empty space what we mean by empty space is when you take out everything else take out all the particles and all the fields that you can remove the Higgs field can't be removed it's a vacuum field okay so electromagnetic field is is zero in the vacuum but the Higgs field does not this is weird but it's true according to the standard model now what if you could fiddle with this Higgs field let's suppose you could turn it off what would happen well the electrons in your body would suddenly start to move at the speed of light the protons would would just change beyond description they'd come unglued perhaps they would just discombobulated so what a weapon you would have if you could control the Higgs field if you could point at something and turn the Higgs field off in that region that thing would just discombobulated completely even better suppose you could turn down the Higgs field like a dimmer switch on a light bulb okay well what would happen things would get less massive right so hey what a way to lose weight without dieting right let's turn down the Higgs field but of course it's much more serious than that because the mass of the electrons determine the properties of the atoms and molecules so if you change the Higgs field even a little bit all the molecules would change completely chemistry would be completely different materials would be completely different if you want to see really new materials different than you can make out of the 92 elements that are known you change the Higgs field okay so this would be an amazing thing if you could do it but can you do it well no one's thought of any way of doing it okay maybe impossible we don't know how but we do know something that just after the Big Bang the Higgs field actually was turned off it wasn't turned on and in those days those picoseconds the universe was a very different place there were no protons and neutrons they couldn't hold together it was just quarks and leptons in a soup every particle is moving at the speed of light you couldn't build any structures you couldn't build anything in days and then about a picosecond after the Big Bang the Higgs field turned on and when the Higgs field turned on this this comes out of the math you can figure this out things could start to go slower now things suddenly became massive and then you could start to build protons and later atoms and all the structure of the universe okay so this weird Higgs field is an essential part of the standard model of particle physics but is it true is it really there is this room filled with it well we don't know the answer why don't we know the answer because we haven't discovered it yet that is what those guys those particle guys in this accelerator are trying to do they want to see whether or not the Higgs field really exists or not this is why there's so much excitement see there's a 15 mile long tunnel here they accelerate electrons in one way and positrons the other way and they smash them together at these these stations here and they are trying to form a ripple in the Higgs field because the standard model says if the Higgs field exists then you can form a ripple of it in it just like if you have water you can form a water ripple okay Faraday and Maxwell's showed that you could make a ripple in the electromagnetic field and that actually is called a radio wave or a light wave and in fact it since it's a quantum field the ripples are quantized and we call them photons and that's what's filling this room Photon the same thing happens with Higgs field you make a ripple in it and that's called a Higgs boson so the search here is for the Higgs boson that's what they want to do okay so for the last decade then people have finding the Higgs boson has been the absolute obsession of particle experimentalist they've tried for 10 years and they haven't found it here now they don't know it's a quantum field theory the size of the quantum isn't known for the Higgs field so they started making little ones and didn't find them so by now we know that if Higgs bosons exist they have to have amassed 100 times that of the proton okay that's the limit of this accelerator it can't really reach it Higgs particles bosons ripples are very difficult to make and to detect for a couple of reasons first it takes a lot of energy to do it and you need a big smasher like that okay second it's hard to get the energy into the ripple of the Higgs field it's much more likely to ripple the cork field to make quark particles okay third when you finally do create a Higgs boson Higgs ripple it almost immediately decays into normal stuff like bottom quarks quarks so then you have the debris and you have to reconstruct was there a Higgs boson created or not so that's why it's bit taken so long okay and it also takes a lot of events to do it so the story happens ten years in world's most powerful accelerator had been cranked to its max and hadn't found any Higgs bosons okay so they decided okay what we've got to do is take out this electron positron Collider use the same tunnel and put protons and antiprotons in which will give us a twenty times more powerful smasher 20 times more easier easier to create Higgs boson so they decide to do this and they were going to schedule to shut down last September okay in July something happened this experiment here the aleph collaborator this is what happens by the way they smash those things together this is the two pieces of the attempter the electrons come one way and the positrons come the other way and these things go together there's people to show you how big this thing is and they all the debris comes out into these things and then he try to reconstruct what happened and say was a Higgs boson was it a ripple in the Higgs field or not that was created okay so these guys Alif announced to the world that they had three or four possible Higgs candidates with this caused amazing excitement you know ten years people been looking now we've got it now they were scheduled to shut down in September so the management said okay run for another month okay so they ran for another month I actually want to show you here's what they saw one of the things they saw this is a picture of that same detector you know in and out of the board as a smashing and this is a debris and the different colors are the Jets that came out of it and this is very likely to have been the debris by carefully analyzing the energy and momentum it's very likely to be the debris from a Higgs boson there are other possibilities though unfortunately and so you have to have lots of these they're unlikely so you have to have lots of these to prove that you have a Higgs boson okay so they let them run another month and then they found some more and in fact Jim Branson a professor here at UCSD he is running one of the other not running but working on one of the other detectors they also found some possible Higgs candidates so it's looking very tantalizing so to say okay run another month now they've crank this thing to the max because it's its lifetime is about up right they're running away past the red line okay this things about ready to pop they have contractors paid for standing outside the tunnel saying you know we've got to dig this thing out and put in the new one it's costing hundreds of thousands of dollars a day to delay you know and so they run for another month and again you know they're finding that this signal for the Higgs but it's not sure so they make the decision they say you know what let's go ahead with our plan let's put in the more powerful machine that will prove it for sure okay so they shut the thing down in December okay happen last year you know a big disappointment to people like myself would love to know but because well the reason there's a disappointment it's going to take five years for the new machine to be ready to run okay and giving data so we're sitting here with nothing to do for five years right except it does actually give a chance to some us people at Fermilab they have built the at Fermilab a proton antiproton Collider it's only about three four miles around it's not as powerful as a new one's going to be but it started this month so hey maybe the US can take back the lead in particle physics and find something the problem of course is that this is not as powerful machine it's going to take them three or four years to get enough data to maybe see those same Higgs 'iz so again we are basically in suspended animation for the next four years or so when it comes to the Higgs boson that's too bad but most people actually let's go on though and say what can we do and then in the interim times before we really know for sure most people are pretty confident in the standard model it's never been wrong okay so we're pretty sure that this Higgs field is feeling all of space and as exist so we pretty sure and we've had some little clue there so let's suppose it's right let's suppose the Higgs boson is discovered and we know that there is this on the presents Higgs field there's a very serious problem with this idea okay because it's been known for 50 years that if you have this vacuum energy that's what the Higgs boson is it's fills empty space and it has energy okay it has a very weird effect on the universe okay Einstein's theory of general relativity shows that the universe has to either contract or expand and it's been measured that the universe is expanding okay if you take and it's the cause of the expansion is the matter in it if you take the universe and fill it with stars and galaxies and atoms and material dark matter anything it will expand and the gravity of those things in it will cause the expansion to slow down okay and by measuring the speed at which is slowing down you can actually measure how much stuff is in the universe people have been trying to do this for 50 years okay if there's enough material in fact the universe will eventually stop contract expanding and start to contract and go back to a Big Crunch so this theory is Big Bang Theory based on n Stein's theory of general relativity is really well well accepted in well-tested it explains many things it explains the Cosmic Microwave Background it explains the number of helium atoms in the universe it gives a very promising theory of structure formation and galaxy formation explains expanse of the universe it's basically the only game in town so we're really in the same way with the standard model particles we're stuck with this model standard cosmology but it's been known for a long time that vacuum energy has a very different effect on the expansion of the universe if you take a box or not a box but a region of the universe and expense it's full of atoms say and expands the number of atoms will stay the same and so the expansion rate will go down the expansion is driven by the amount of material inside a region okay now if you take that same region and fill it with a vacuum which of course it automatically is and now you expand you've got more vacuum if every cubic centimeter has vacuum energy you've got more energy the expansion rate will we'll go even more now it really takes solving general the theory of general relativity and a lot of math to show this but it's an absolutely inescapable conclusion of general relativity that if you have vacuum energy the universe will undergo a runaway accelerating exponential expansion okay now the standard model says in fact that the Higgs field it fills up the universe and it even tells how much it is the Higgs field in one cubic centimeter is more than a trillion tons that's how much it is a trillion tons per cc and can you feel that well as I said you actually do feel it because your hand is able to move slowly it's what gives you the mass but if you plug that number into instance equations you'll find in less than a nanosecond the universe should have expanded to a billion times its current size something is terribly terribly terribly wrong with this theory okay where is the problem okay well in fact there's a very easy but very ugly theoretical solution to this okay and it's one of the major unsolved problems in in in particle physics here's a solution okay the Higgs field fills all space with more than a trillion tons per cc let's take another field unknown ad hoc field that's never been invented just for this purpose we'll invent it and it fills all of space but contributes minus trillions of tons per cc and cancels it out now in regular life we can't have negative energy everything we have is positive energy but in quantum field theory the vacuum is allowed perfectly consistent mathematically is allowed to have negative energy so there's nothing mathematically or theoretically wrong with having this - vacuum energy except it's very weird that we have to take some ad hoc field and cancel out this stuff and it's even worse than this because lots of other fields in particle physics the quark fields for example also contribute vacuum energy and that has to be cancelled out - okay so this is called the cosmological constant problem because the vacuum energy cosmical constant is another name for the vacuum energy the madjoe cause that was introduced by einstein he later called it his laters blunder his biggest blunder it actually is here now and we'll see why in just a second so what's interesting is that that this cancellation has to happen and no one knows how it happens in fact some of the biggest names in particle theory ed Witten and Steven Weinberg have said that the most important unsolved problem in particle physics is the cosmological constant problem how to arrange this cancellation okay now there was a huge new wrinkle to this happened a couple years ago by people playing around with telescopes like this some of my friends at Berkley went out and said well let's see let's test this hypothesis let's see whether the universe is expanding well how is expanding and is it speeding up or slowing down is the universe filled of ordinary material in which case the expansion should be slowing down or is it filled with vacuum energy in which case it should be speeding up and you can do this because looking out in space is looking back in time if you see a galaxy a million light years away you're seeing the light took a million years to get to you you're seeing it as it was a million years ago so if you go out and find galaxies billions of light years away you can see what the universe is doing a billion years ago one more right so so we use a tech telescope use the Hubble Space Telescope to do this and what they do is they look at supernovas okay so they find these distant galaxies that's a supernova there it's an exploding star and they're wonderful they're all the same brightness and by measuring them very carefully you can see exactly how far away they are and how fast they're moving away from you so you can actually measure the expansion rate as a function of time there's another supernova there there's another supernova and these are some nearby supernova remnants the blast wave from the exploded star looks like this after a few thousand years but for the few weeks that a supernova happens that one star becomes as bright as the hundred million or a hundred billion stars in this galaxy I don't know how big that galaxy is that's why I had to say that okay so what did they find well they found in fact that in the past the universe was expanding slower that means today it's expanding faster that means the expansion is speeding up which means that vacuum energy is driving the expansion any kind of ordinary material would have slowed the universe down as it expanded but it's speeding up so we are actually going through this exponential expansion that I described we're actually in it right now okay this was a shock to the scientific world even though it was a theoretical possible building for 50 years people didn't expect it and and but it was called the science story of the year by science magazine in 1999 so it's an amazing discovery and one nice thing about it is that you can say okay I said the Higgs field was more than a trillion tons per cc these guys can measure how much is the vacuum energy and they can do it it's about 10 to the minus 29 grams per CC that's about one proton mass per cubic foot so this makes the cosmological constant problem even more acute you have to take this trillions of tons cancel it off and leave ten to the minus twenty nine grams in each cubic centimeter this is a very precise cancellation and nobody has a clue on what mechanism is causing that okay so this stuff even though it doesn't seem like much one proton per cubic foot there's a lot of space out there and in fact if you add up the stuff in the vacuum it's ten times more than all the atoms and everything known okay it's twice as much as the mysterious dark matter so this vacuum energy the energy of empty space we now know is the dominant substance in the universe it's driving the universe it's determining our fate okay so there we are well where we going to go from here okay how are we going to make progress we don't understand this well particle experimental experimentalist can maybe find the Higgs and tell us if this is right or not and there are other theoretical ideas such as supersymmetry that really helped in this cancellation astronomers can mention can measure the expansion rate more accurately and tell us very important thing is this vacuum energy changing with time or not the cosmos will constant is a constant with time the vacuum energy could change if they find it changing with time will be a great clue on what kind of quantum field is responsible we don't know what quantum field is responsible for the expanse of the universe now but what we really need here is a theory we need a theory that will predict what's going on here in the vacuum and tell us that if you think about what kind of theory could do this it turns out there's really only one that people thought of and this this is a brand-new theory not that new but theoretically new super string theory okay super string theory is the first consistent theory we have of quantum gravity it's a very speculative theory at this point but it held a lot of promise now you may know that Einstein wasted the last decades of his life trying to find a unified field theory he wanted to make electromagnetism and gravity all part of one unified theory and he failed miserably and it's clear now why he failed miserably he didn't know about the standard model he didn't know about gauge symmetries he didn't know about nuclear forces or quarks or any of the things you would need to put together a unified field theory but his dream of a unified field theory stayed on and finally maybe 10 or 15 years ago the super string theory came along and that is the first candidate we have had it's a very beautiful and elegant theory but unlike the theories I've talked about before which are well tested by experiment super string theory has no experimental tests so it's speculative okay so I'm shifting into a much more speculative place right now okay well in string theory there's only one elementary particle and it's not a particle at all it's a loop of string okay and there's only one force in string theory and that force is two strings can come together and join and then they can split apart that's it very nice huh very simple the beautiful thing is is that different particles that we know of like electrons and quarks and photons basically these are just the same loops of string vibrating or winding in different ways okay now one very elegant thing about the superstring theory is that it automatically includes supersymmetry this neat symmetry that helps with these cancellations okay but even more elegant and important is that it automatically includes loops of Springs strings that vibrate like graviton in other words it automatically include particles quantized particles that look like gravity so it's automatically a quantum theory of gravity okay so it's great so it's a beautiful theory with lots of potential but it has some serious obstacles okay the first one is that these loops of strings are very very small 10 to the minus 33 centimeters they're so small that you'll never see these strings in the biggest accelerator that you can even think of okay you need accelerator the size of the galaxies in order to measure these things so we're never going to see these strings this is very bad for for physics which likes some data to prove things right the second interesting thing about string theory there's many but a very interesting thing is that the strings are only consistent if you have 10 dimensions 9 space and one time dimension okay now we know there's three dimensions one space dimensions two three three right angles in super string theory you have to have six other spatial dimensions to make the theory make sense okay well this would seem like this would rule out the experience there theory right now right because where are they right but in fact this may not be a bug it may be a feature because because these extra dimensions could exist and just be curled up so small that you can't see them and let me give you an example if you take a piece of paper flat piece of paper that's two dimensions right I could curl up one of the dimensions into a little tube right and if I curl it up so small and you were going along it maybe you'd only think there was one dimension you wouldn't see the little internal dimension and in fact I could take a piece of paper and I could curl up like a ball or I could curl it up like a doughnut the hole in it right so these six extra dimensions are hypothesized to be curled up into something so small that you can't see them now why this is a feature is it turns out that these the way these internal dimensions these extra dimensions curl up determine what particles are in the universe in fact you can show that the number like a doughnut has one hole in it that the number of generations turns out to be the number of holes in the curled up dimensions okay so if you go back to the standard model of particle physics you notice that there were three generations well that says that these curled up six extra dimensions have three holes in the internal collab il manifold okay well that's really cool so what that means then is that the now this is empty space I'm talking about curling up so once again we see it's empty space that's determining things the contents of empty space is determining the fate of the universe and the topology or the shape of empty space we have here like three generations nobody knows why are there three copies the muon and tau ER just like the electron except with a different mass why are they there well super string theory says well it's because the way empty space curls up determines the number of generations okay it turns out many of the other properties are determined by how this thing's curled up okay so so if this theory is correct the shape of the universe determines the most important quantities of the universe and the content for example in another universe these internal dimensions might curl up differently and maybe you would have only one type of electron or maybe you have 15 different types of electrons right or you could have completely different particles in another universe by curling empty space in a different way okay how about another universe where instead of six dimensions curling up leaving three big ones that we see how about if five of them curled up leaving you with a four-dimensional universe or maybe more with two-dimensional all these properties of the universe that we just take for granted turn out to depend in super string theory on how these extra dimensions curl up okay so this sounds like science fiction but what is true is that the properties of the vacuum are turning out to determine many of the most important properties of the world around us now I should stop here to stop here but I would like to finish by just asking whether all this bizarre stuff I've been talking about is actually important okay does anybody care does it matter if we know it or not is it ever going to be of any practical use okay well the honest answer is I don't know but it does remind me of a similar question asked to Michael Faraday by Prime Minister Gladstone of England a couple hundred years ago Michael Faraday was the most famous scientist of his day he discovered the laws of electricity and magnetism and some of them and how wires could move his inventions his discoveries led straight to electric motors generators and then pretty into pretty directly to radio and all electronics okay so Prime Minister Gladstone is touring the lab finishes turning the lab and he sees the Leyden jars and he sees the wires being moved he says Oh professor Faraday this is all very well and good but can you tell me is this electricity ever going to be good for anything and Faraday you know was a curiosity based researcher he had wasn't thinking about practical things he says I don't know so so I'll stop there I said there had to be this huge cancellation to have this of the Higgs to get to the little one well you need the Higgs boson field to be exactly as it says in the standard model in order to slow your hand down if you had that little tiny difference only your hand would be going way too fast and you couldn't get the masses of particles those masses are fixed by experimental quantities such as the mass of the W boson the Z boson other properties it's not a free parameter of the theory we know that trillions of tons per cc is not an adjustable parameter at this point because we've measured its measured what can we say okay he asked whether the present of the higgs field has a preferred frame of reference as you know Einstein says there is no preferred frame of reference but in fact it's not a preferred frame of reference it is the vacuum it is Lorentz invariant in other words more technically if you're moving along you can't tell the difference the vacuum is the same for every observer so yeah it's it's empty space really is yeah I know that doesn't sound too satisfying but hey what turned on the Higgs field in the early universe when the universe was very young it was very hot and what you can actually show is that when it was very hot and particles were interacting so fast that the potential that sets the Higgs boson field was actually turned off was symmetric okay and so what happened was the universe got to a cool enough temperature that the field theory could start to operate and vacuum the nature of the vacuum change we actually have this a lot in early universe we have the true vacuum and then we have the false vacuum so we were say we would say the nature of the vacuum changes as a function of temperature in the early universe that's again a subtle concept and you have to write down some math to show you what it really means yes is there any theoretical upper bound on the mass of the Higgs boson depends on your what you what you want to go with typically in normal particle physics yes it's around a TeV or a thousand times the mass of the proton that's what people think what happens if you make the Higgs boson more massive than that is the the beautiful standard model perturbation theory starts to break down and we don't have an all we can't explain why it works so well now it could be that something else by coincident makes it worse oh well so people have argued that but I think that around a thousand GeV is where it should be maybe two thousand you know around that and then we searched from zero up to a hundred so we still have the big window left to search and that's exactly what the LHC in Geneva is going to try to do and what Fermilab is trying to do could the Higgs field vary in the universe I mean this didn't used to be a question that anyone would even think about asking but now that we have measured the vacuum energy it's a worthwhile question to ask and the Higgs field probably not if the Higgs field did vary then things like the electron mass would vary okay so so but I don't think it's really been thought about the vacuum energy that we think if it's a changing vacuum vacuum energy then in fact it would vary in space as well as time so these are brand-new questions and they're good ones and this is where some of the theoretical work is going right now yes if you assume that the measurements at CERN have identified a Higgs boson that mass is inferred by those it's it's around a hundred a little more than 100 GeV so right near the top of there right at the limit of their measure ability I didn't even talk about the properties the quantum properties of the vacuum he said how does the Higgs field vacuum relate to the particle the zero-point energy you hear people talking about particles appearing and disappearing and that also creates a vacuum energy in fact in point particle physics that creates an infinite vacuum energy people have figured out that you're allowed to subtract that there's technical ways to subtract it it's the quantum vacuum is even are complicated again string theory seems to be the way to approach this and again it's part of the cosmos or constant problem the using the Higgs field shows you something you know exists this could be there it could not be there may be something more complicated that cancels that out supersymmetry for instance cancels out that kind of quantum vacuum if so I know that wasn't a very complete answer or very pure but that is another contribution to the vacuum energy that I didn't even discuss and it's it's probably there it probably has to it must also be canceled out to this extreme accuracy as well it's not infinite if string theory is right because strings are a finite size and so they actually there's a smallest possible thing and so a biggest possible energy you can have any any reason that the anti higgs field that cancels it doesn't affect our our masses and in fact it's not an anti higgs field it just has to be some other field with negative energy density so it's probably has nothing to do with the Higgs field if supersymmetry is right it may have something to do with some supersymmetric partner of the higgs field though it may not even in that case we don't know what it is it's just some other field that's the level of knowledge so how could you experimentally verify super string theory well you can't see the loops of string directly but maybe if you had a good theory you could calculate with it the main problem is you can't calculate if you could calculate that exactly what the masses of all the particles were that would be fantastic and that might be possible if you could measure the exact shapes of these internal dimensions there has been some very interesting they're not really confirmations but they've managed to calculate black hole radiation in string theory and get the right answer in a way that was completely independent of any way they did it before very exciting result that led people to think string theory might be right you could possibly calculate the number of space-time dimensions you could calculate you would like to be able to calculate from first principles this entire table and that's if you did that even without direct measurement of the strings you'd start to believe it plus if you could do that you may be able to calculate some things that haven't been seen yet and then predict them that would be the hope like maybe you could predict some other kinds of neutrinos some other funny things how the Big Bang happened something like that

Channel: University of California Television (UCTV)

Views: 596,605

Rating: 4.7776194 out of 5

Keywords: space, mystery, science

Id: Y-vKh_jKX7Q

Length: 42min 53sec (2573 seconds)

Published: Thu Apr 24 2008