The Biggest Ideas in the Universe | 18. Atoms

hello everyone welcome to the biggest ideas in the universe I'm your host John Carroll this is idea number 18 and we are continuing to sort of build back up the universe of our everyday experience from these fundamental ideas that we've been talking about so the ideas we've been talking about so far often go under the rubric of fundamental or elementary physics and that doesn't mean fundamental in the sense of more important or more interesting or worth more money or anything like that it just means that the stuff we've been talking about makes up the stuff of our everyday life it's sensible to say that protons and neutrons are made of quarks that atoms are made of electrons and protons and neutrons but it doesn't make sense to say that protons and neutrons are made of atoms that just wouldn't be true so the fundamental physics we've been talking about so far is sort of the base level stuff and then you put it together to make bigger things and it turns out that in the process of making bigger things a lot of incredibly cool stuff happens it's not always personally my area of expertise so I can't do it justice as well as some other people might but there are some very clear big ideas worth talking about in that journey back to our everyday world and today's big idea is atoms now atoms might sound a little down-to-earth you might feel like well I know about atoms I don't need to watch this one right you might not know about the spin statistics theorem or gauge Theory but you know what the little picture with the protons and the neutrons and all the electrons going around it I'm using the catch-all word atoms as usual to describe some deeper things what I want to describe is how you start with the rules of the standard model of particle physics or really the core theory that also has gravity in it and how you end up with the stuff that actually makes up you and me why these particular atom so I'm not necessarily telling you what an atom is and expecting you be surprised I'm explaining why atoms are that way so where we really start is with the standard model of particle physics and I'm just gonna call it the standard model even though including gravity for reasons which we've already talked about and you know that what's in the standard model are fermions which make up the matter particles okay and fermions come in two different classes there are quarks well it just let my mind there for a minute quarks quarks which are colored they have red green or blue colors and they're subject to the strong nuclear force quantum chromodynamics pushing around the colors and then leptons which are just particles that are fermions and do not feel the strong nuclear force both the quarks and the leptons feel the weak nuclear force they feel gravity most of them feel electromagnetism and so forth so you have the fermions and then you have the bosons and the bosons also come in two very different classes they're the gauge bosons the sort of traditional force carrying bosons for the electromagnetic force we have the photons for the strong force we have the gluons for gravity we have graviton sand for the weak force there are the W and Z bosons and there's the Higgs boson and you know in some sense the Higgs carries a force but it's incredibly tiny short-range very weak force so you don't notice it all the time but it's a boson but it's not a gauge boson it is a spin zero scalar boson the Higgs is responsible for the symmetry breaking and the weak interactions that we've talked about before but it's definitely there we discovered it I wrote a book about it you can read the book so we'll definitely include it in the standard model lots of people have tried to figure out fun geometric ways to present to you what are all the particles in the standard model I think they are all kind of artificial looking a little bit ad hoc so I'm just gonna make a little plot and the plot will be mass of individual particles and on the horizontal axis we will have the charge of the particles ok the electrical charge different ways to do it I think electric charge is very noticeable there and let's you know talk about what we call matter particles there's also antimatter particles we'll get to those in a minute but basically there's just four every for most of these matter particles there's also an antimatter particle so we'll list the charges that we have as minus one like the electron there are ones that are minus one third like the down quark there are particles that are charge zero and there are particles that are charged two thirds plus two thirds so these are not equally spaced but you get the idea these are the ones that be important for the standard model as far as mass is concerned you know the highest mass particles in the standard model the top quark is the most massive at around 174 GeV GeV billion electron volts okay a proton is around 1 GeV just for scale so I'm not gonna be very detailed I'm not gonna get bogged down in the five-digit decimal place accuracy of what the mass of the different particles are so to me the mass of the top quark is around 100 GeV 174 is around 100 by today's standards so let's put a hundred GeV up there and then let's look at there are also particles all even put a tilde there to let you know that we're just being order of magnitude ish there are particles around 1 GeV there are particles around 1 MeV that's a million electron volts ok 10 to the sixth electron volts there's a huge gap and there are some particles around 10 to the minus 3 electron volts that's a little MeV milla electron volt and then there's another a huge gap that it won't even draw because there are other particles around 0 electron volts massless particles right then we can go through we can go through the different possibilities so let's do the bosons first why not okay so we have the Higgs boson Higgs is charge zero and mass 125 which by my standards now is around 100 so here is the Higgs the other massive bosons are the W and the Z they get their mass from the spontaneous symmetry breaking caused by the Higgs boson so roughly speaking they're also at that hundred GeV level the W I'm gonna put in the minus one charge column W minus there's also W Plus which is its anti particle the Higgs are sorry the Z rather just has a single particle the Z zero it is neutral okay so that's where the massive bosons are the massless bosons you know what those are you have the photon that's charge less zero mass you have the gluon which I will call G and you also have the graviton which I will call H why do I call the graviton H well there's two reasons one is I already used G for the gluon so H equals graviton and why is that well it's because when you think about what the graviton is it's a oscillation right it's a fluctuation a tiny little vibration in the gravitational field the gravitational field is given by the metric tensor G mu nu you talked about that a little bit and so if we're looking at a fluctuation of that what we generally do is write the whole metric G mu nu as the background and the traditional symbol for that is ADA the Greek letter ADA is the flat background Minkowski space special relativity metric tensor then plus a perturbation and since we've already used G we call the perturbation H mu nu okay so it doesn't matter whether you think about H being the graviton because it's an expansion of G and H is the next letter after G or just because we already used G in our table for the gluon this is why all right am I missing any other bosons I think that's all the bosons why don't we do some fermions well we have two leptons let me see if I can make this different color okay leptons we have the electron that's around half an MeV so by my standards today that's at 1 MeV and the electron is charged minus 1 then the electron has to heavier cousins right it has the muon and has the towel and these basically go right here there's the MU there's the tau at around 1 GeV and then you have the much lower mass neutrinos neutrinos are also leptons there are three of them and we traditionally classified them as the electron neutrino the muon neutrino and the town in torino and roughly speaking this is not exactly true but roughly speaking electron ness munis and Taunus are separately conserved so when a particle decays when a particle which has no lepton number decays into let's say let's say the W - ok it can decay into an electron and an anti-neutrino it has to be a particle and an anti particle but the electron has charged minus 1 neutrinos charge 0 so that works but the electron has chart has electron number plus 1 so the neutrino better have a lek number minus ones that's an electron neutrino that you make it would not be a muon neutrino or a Tau neutrino so the tree knows are the ones that are around 10 to minus 3 evey again we're being a little sloppy here because we actually haven't measured specifically what the masses are in fact we're being sloppy because there are three neutrino mass states which are combinations of the electron neutrino the town neutrino and the muon neutrinos so guess be very messy neutrinos can mix people live their whole lives just studying neutrinos and it's a a word the occupation to study but for now our study consists of writing down the symbols nu e nu mu and nu tau we're not even sure with individual masses ours let's just group them there roughly 10 to the minus 3 electron volts okay and then we have quarks right the quarks we have the up quark now the up quark the way to remember it is in a proton or two ups and down protons are positively charged so it better be true that ups are positively charged and indeed an up quark has charged plus two thirds and the up quark is not that much more massive than the electron is like less than ten times as massive as the electron even though the proton is 1800 times more massive but we talked about that the proton gets its mass mostly from QCD from the gluon energies inside the proton not from the masses of its quarks so the up quark will go over here near the electron but in the plus two-thirds column so that's an up quark and then there's a charm quark at around a GeV and the top quark way up here with a W and the Z and the Higgs of order 100 GeV and then you have the minus one-third quarks and you have the down you have this strange and you have the bottom quark again around 1 GeV and that's it this is the standard model of particle physics plus the graviton is stuck in there and look you can stare at this chart for a long time like and it's frustrating because there are clearly some patterns there are three families or generations of particles right if you if you take the electron and it's neutrino as the lightest leptons then you have the up quark and the down as the latest quarks and then you have the next family which is the the muon and it's neutrino and the charm quark and the strange quark and then you have another family the tau and it's neutrino and the top quark and the bottom Clark but they're not exactly arranged perfectly here I mean there's this mismatch when minus 1/3 and plus 2/3 for the charges more interestingly the up is a little bit lighter than the down but the charm is heavier than the strange and the top is heavier way heavier than the bottom the bottom strange and down are comparable in mass to their charged leptons but the neutrinos are very very low masses and the plus 2/3 quarks are generally heavier than the other guys and so it like it doesn't really quite make much sense like there there's random numbers here it's not like these are related by the square root of 2 or something like that so a big goal on the part of modern particle physics is to understand this pattern of particles in the standard model we're not gonna do that today but just you know I like to give little homework assignments for the students out there who might be watching this figure out this chart derive this chart from first principles that would be a good homework assignment okay so what are we gonna do we're gonna talk about how you go from this chart to atoms okay like why do some particles appear in atoms and not others why do they are the atoms made of the particles that they are well there what's important is particles will decay okay heavy particles decaying the lighter ones that's because from a heavy particle you can create several lighter ones it's really the second law of thermodynamics at work the second law says entropy increases roughly speaking for particles can have more entropy than one particle can have one particle can only do one thing four particles can be arranged in lots of different ways so if you can have one particle that can decay into four it will but the question is can it and one question one point is it has to be you know more massive otherwise you can't decay while conserving energy the other is there can be other conserved quantities okay like electric charge is the most obvious one whenever you're going to decay some particles the total electric charge better be conserved but in addition to that you have two other conserved quantities I'm going to worry about I'm not going to worry about electron number muon number town number but I will worry about baryon number so the reason why it's called baryon numbers because remember the quarks have color either red green or blue and you never see color in the real world color is confined that it's confined inside other particles so a baryon is a collection of three quarks and the three quarks one of them is red one of them is green one of them is blue there are also mesons massan's are one clark and one anti quark so the color can be confined there because roughly if you think of red green and blue as combining to make white then the rule of quarks being confined is that the of the visible combinations of quarks that we see in our particle physics experiments are colorless so red green and blue counts as colorless so a 3-quart Berry on one red one green one blue that works that's allowed Amazon which is a quark and an antiquark will be red anti red blue anti blue whatever that is also colorless so those are the two obvious kinds of things you can make so anyway the reason why we talk about variant number rather than quark numbers because variants are what we observe baryons are these combinations of three quarks and each quark guess what has a bearing on number of 1/3 so baryon number plus 1/3 goes to all the quarks up down charm strange bottom top and then we also have lepton number for leptons the lepton number plus 1 is associated with an electron muon a Tau an electron neutrino muon neutrino and a Tau neutrino ok and this is going to be conserved both of these quantities electric charge baryon number lepton number and of course energy these are all conserved when these particles decay and if you have an anti particle of any of them then you have baryon number minus 1/3 for an anti quark or lepton number minus 1 for an anteye lepton there you go so those are the rules okay so we're gonna talk about how particles decay so decays and to do that we're gonna use Oh actually sorry before I talk about the decay let me mention again let me just write down here that the baryons are confined okay in two colorless combinations I should draw the picture because then it gets into your brain I said to the words so either had sorry and what I should say is quarks are confined that's why I was getting confused quarks are confined and gluons okay but the gluons just were to go along for the ride the quarks are confined to color those combinations and when there are three quarks we call them a baryon that's why I got confused so baryons are for example proton will be up up down and that has bearing on number plus one because you have three quarks mez ons are let's say up and tied down okay so this is a pi plus pi on how do i knows plus well up is plus two-thirds anti down as minus one-third there you go this has barium number zero so we can make pi ons very easily and you might think well doesn't a quark and antiquark don't they just annihilate and the answer is yes if they were exactly the same and up and anti up would annihilate very very quickly these guys do eventually go away but we'll we'll get to that okay so now we can get to the decays now I can talk about that so remember the rules are heavier particles go to lighter ones sufficiently lighter that the total mass of what you decay into is less than the total mass of the single particle that did the decaying so the reason why energy is conserved is because the decay adults have energy has ADD momentum in addition to equals mc-squared they also have kinetic energy okay and so the total energy the particles that the decay products are consists of must be moving at the right velocities so that the total energy of the combination of decay products adds up to the total mass at the original particle times C squared and lepton number baryon number and charge are all conserved I said all these things out loud clearly I was getting excited and couldn't resist do we got to the point of writing them but there you go okay and we're gonna discuss the decays in terms of Fineman diagrams okay so we're gonna draw the Fineman diagram lines the Higgs boson is special because the only spin zero particle in the fundamental standard model chart so it gets a dashed line it looks like that the fermions all of them kind of look the same in terms of fireman diagrams or just straight lines and I will draw Fermi on number as the arrow there so the arrow does not mean momentum this arrow does not mean the direction which the particles moving it means the direction which the Fermi on number is flowing so an anti particle will have the arrow pointing the other way and then you have the gauge bosons and those will be wavy lines because it's kind of like light right I like radiation gauge bosons so what I wanted to establish is that most of these particles just decay away and the ones that don't go into making atoms in some complicated way there is a rule in this game we're nature you know apparently Einstein once said that nature is subtle but not malicious but you would think sometimes that nature is malicious the way that things work out here in the standard model it gets very very complicated like every complication that you might worry about ends up actually being true in the standard model okay so let's go through and figure out how things decay and we're just going to go through all these particles and ask can they decay or can they not given these rules okay so the Higgs can decay certainly in fact it can decay in a few ways so the Higgs couples to both fermions and to gauge bosons in ways yeah the Higgs itself has no conserved quantities other than energy right it has zero charge zero spin zero lepton number zero baryon number I was hesitating there's a thing you've spin spin is also conserved but it can be it's part of angular momentum so it's not conserved by itself therefore it enters into the Fineman diagram is in a more subtle way that's why we're not doing it explicitly we don't need to use it for any of these purposes so eggs can decay for example I don't know pick whatever you want it can decay into electron and a positron ki + oops and here's H there you go that's the decay it could also decay into two quarks so here is a quark let me be careful about this I mean let me draw this picture a little bit bigger for reasons that will become clear so here's a quark here's an anti quark and here's the Higgs so the Higgs can decay into that the problem is the quark and the antiquark can't just go their own way all by themselves cuz quarks are confined right so you might worry that this doesn't happen or it just decays into a single mess on which is a quark antiquark pair but that can't happen because then it's one particle the Higgs decaying into one other particle the Mazon and that just can't happen unless those particles have exactly the same energy which they wouldnt which there's no mess on that has exactly the energy of the Higgs so what can possibly happen well one thing that could happen is one of these quarks could give off let's say a Z boson and then that can decay into an antiquark and a quark and now you have two mesons being produced okay so the here's of how the diagrams become more complicated because there's a million different constraints you have to satisfy when you ask how these processes actually happen and then what you would want to do is actually calculate the rate of this happening and that might be hard this doesn't need to be a Z in fact it's more likely it could be a Z but is much more likely to be a gluon right because gluons are strongly coupled QCD is strongly coupled whereas the W bosons or the Z bosons are weakly coupled so this is a much more likely diagram in fact it's so likely that you should probably be including a lot more gluons in there and becomes very very complicated very very hard to calculate again full employment for professional particle physicists and there are other ways you know I'm not gonna list all the possible decay modes of the Higgs but one thing that it can do is decay into two quarks as we said before I should draw the little arrows like I said I would on the quark lines on the Fermi on lines so here's a quark here's a Higgs going into a quark antiquark pair and what could happen is that they can spit off let's say photons there's a quark here's an anti quark by creating a little closed loop of quark I can label that Q or anti Q it doesn't matter because it's a vertical line which means it could be either going forward in time or backward in time if it's going backward it's an anti quark it's going forward it's a quark and then another photon comes out here so this is a way that the Higgs can decay into two photons again you see how complicated it gets in fact the Higgs is decaying two photons if I'm remembering it correctly this is not a very common way the Higgs decays maybe like one percent at the time but it sticks out above the background if we were doing a different set of videos talking about experimental particle physics someone else would have to do them but one of the biggest challenges is not just seeing things that you're looking for but making sure they are really statistically significant over and above other things other ways the same thing could happen so you know you don't ever see a Higgs boson in the Large Hadron Collider I know that you think that we found it what we've found is the decay products of the Higgs so we see two protons smashing into each other a bunch of particles come out and two of them are high-energy photons and you say well what would I expect the rate of that to be in the absence of the Higgs boson existing and I compare it to the actual rate and they say AHA there must be a Higgs boson there too account for that fact just this I know this is going off of off schedule here but as a function of energy so you could look for two photons being created in the Smashing of two protons together at the Large Hadron Collider okay and there's a jillion ways for that to actually happen and what you would predict is as the energy energy gets higher this is the total energy of the two photons being produced okay without the Higgs you'd expect it to be you know harder and harder to make high-energy photons there'd be some rate so this is the rate or the total number of events that you see in your detector okay you just run this for a very very long time but what you actually see is something like this you see a bump okay so you see what you expected plus an excess and that excess is at the energy of the two photons equals the mass of the Higgs 125 GeV that's how you measure the mass of the Higgs it's from the total energy of the photons or whatever that it turns into okay there's a there's a million complications in particle physics so we can easily get out of hand here but take that for granted the Higgs decays away very quickly one Zepto second is the lifetime of the Higgs boson for the W or the Z you've got a very similar thing let's just say let's imagine you have a w- okay so there you can't just decay into two photons because two photons have total zero charge and w- has charge minus one what can you do well you know what you can do you could have an electron let me get my arrow pointing the right direction here there's my electron so that's carrying the charge and then you went from zero lepton number 2-1 lips sorry to plus one lepton number therefore you better make up for it by making something with zero charge and minus one lepton number and you know what that is that is a lek tron antineutrino there you go and this can also happen very quickly you can play the same game for the Z bosons for example alright so where are we well we have quarks let's look at what the heavy quarks can do so the charm the strange the bottom the top by heavy quarks I mean anything other than that up and down okay and they can decay very very quickly roughly speaking you know when a heavy particle decays into lighter particles there's a rate at which that decay happens and there are two things that help you figure out what that rate is one is how strongly is the coupling that makes the decay happen so if you can decay through the strong interactions like over here that's why I did this gluon picture right here this gluon would be the primary way of having this thing happen because that's a strong interaction that happens all the time whereas if you need the weak interactions like the W boson decay needs that's a slower kind of decay so that's one thing you need the other the other thing that goes into it is how much room do you have to decay so if you're a massive particle decaying into a set of particles with lower mass do the total masses of the particles you're decaying into come close to what your mass was that means only have a tiny little window in fact what we say is you have a tiny amount of phase space to decay into and that makes your decay slower whereas if you can decay into much later particles then you have a lot of phase space a lot of different ways to distribute the energies that came from your e equals mc-squared into your decay products and that lets the decay go faster so the top quark and the bottom quark for example decay by very similar ways but because the top quark is so much heavier it will decay much much faster so what's a typical decay well the top quark for example could turn into a down quark let's remember top quark is charge plus two-thirds down quark is charge minus one-third okay so the charge has to go somewhere plus 2/3 1/2 minus 1/3 let's imagine that what happened is a w+ got made and that w plus well that can decay then let's imagine that decays into a neutrino and a positron the anti particle the electron right which has a charge plus one things like that this is just one example of many many many but anyway all these quarks can decay very quickly likewise the heavy leptons can decay very quickly the mew and the Tao the mew actually can't decay that quickly is it's pretty light and it can only decay through the weak interactions it's for both the weakness of the interaction and the amount of phase space it has there's not that much this it's hard for it to decay so it leaves a relatively long lifetime by the standards of elementary particles but it can decay so here's a mew - and it can decay for example into neutrino the muon neutrino by emitting let's see well it went from minus 1 to 0 charge so it had better emit a charged particle like the w- then guess what the w- can decay for example into an electron and an anti-neutrino and likewise the Tau the tab decays also pretty quickly because it's heavier than the muon finally so the neutrinos themselves can't decay they can turn into each other there's no lighter lepton right there's no lighter Fermi on than the neutrino and since Fermi on number is conserved there's no word for the neutrinos to go but they can because neutrinos mix with each other appear to change into each other right a muon neutrino and a town something can be created in the form of a muon neutrino and be detected in the form of the Tau neutrino of conditions in between are correct but we're gonna ignore that it's not really the total number of neutrinos isn't changing when those decays happen the final thing that can happen is that the quarks that do get together can get together in combinations that don't live forever right so mesons can decay in fact there are no completely stable mesons I said let's take the PI plus the positively charged PI on there's a pi minus a PI 0 pi plus these are the lightest mesons out there and the pi plus is just an up quark and an anti down okay that's the combination that it is and what could happen is the down is a little bit lighter than the up but these can come together it's a true fact that down a little bit later but it's irrelevant to what I'm about to say what could happen is that you know in the world of Fineman diagrams you know that the intermediate lines in Fineman diagrams represent virtual particles so they're not real particles so I can temporarily have them be any energy I want it's not that energy conservation is violated it says they can have whatever energy I want so I can create a virtual W boson so I can imagine these two particles come together to make a W it it better be a W plus because I have a positive charge flowing through this diagram and this W Plus virtual W plus can have exactly the right energy to be the PI on as long as it then decays so it can decay the way that we've seen the W plus decay over here into let's say an electron neutrino and a positron there you go so a single Payan can just decay just like that into a electron and neutrino and you see that even though the Payan is a strongly interacting particle even though it's Amazon it has net very on number zero because of the quark and an antiquark likewise its decay products here have net lepton number zero because it's a lepton in anti lepton so all the conservation laws are being perfectly well respected ha so as you see most of these particles decay away in fact they decay away pretty quickly what are we left with well it's a pretty familiar story we're left with the massless unconfined gauge bosons the massive gauge bosons the W and Z s decay the massless gluons are confined inside hadron so in terms of the particles that you see you can see massless unconfined gauge bosons namely the photon gamma and the graviton H graviton I'll remind you I know you don't see gravitons but you see gravity which is can be thought of as the collective force due to many many many many gravitons you also get neutrinos they're allowed to stick around NUI new Moo new town you have electrons remember your tree knows concerning to each other they don't actually decay electrons just sit around there you go II - they're heavier cousins do decay into them and then you have up and down quarks confined into hadrons in fact hadrons remember hydrants are the collections of sorry baryons are collections of three particles hadrons that's that's I wanted to say these combined are called hadrons okay hydrants are any collections of strongly directing particles namely quarks and gluons and these are confined to headphones in particular I didn't want to say hey drones I want to say they're combining to light a particular kind of had drawn light colorless baryons namely there are two of them the proton up up down and the neutron up down down okay so these are the two that can hang around now there's a subtlety because like I said there's a million subtleties going on here the neutron proton you might say to yourself well wait a minute the down is heavier than the up and you told me that heavier particles want to decay so shouldn't the lightest baryon be three up quarks isn't that the lightest thing that you can make there are particles with made of three up quarks there's the there are Delta baryons okay but remember the Polly exclusion principle you can't have two particles in the same state and so if I have two ups and a down their wave functions can be the same because they're different kinds of particles they're not identical particles and up and down are not identical but two up quarks are identical so it turns out I'm skipping some steps but it turns out if you try to squeeze three up core into the same baryon you can do it but only by having them be a little bit more energetic than they otherwise would be in particular their spins have to be pointing in the same direction so it costs a little bit more energy that's like the heavier particle so the masses of baryons are not just the sums of the masses of the quarks they're made out of it turns out in the real world the lightest baryon is the proton with two ups and a down but what about two downs and up I mean that's not the lightest very on neutrons are heavier than protons so shouldn't they decay the answer is yes neutrons do decay and then your question is well why don't or rather why do we see neutrons all over the place why do we live in a world which is you know literally the earth or I'm pretty sure that your body is most of its masses in the form of neutrons not in the form of protons or electrons why is that well let's first explain how they decay a neutron and zero is an up a down and another down okay it's a collection of those three quarks and the way it decays is that one of those downs turns into an up okay which we know can happen by the W bosons so just imagine this this this here are your particles your quarks carrying their Fermi on number but the down which is charged minus one-third admits a W minus to become an up quark and now you have two ups in a down and this is called a proton and the W minus does its thing it turns into electron and electron there you go so this can happen absolutely neutrons do decay but here's the thing the total mass of proton plus electron plus neutrino is less than the mass of the neutron but not by much so you go to the details here let me see I looked it up I don't remember these things the mass of the neutron minus the mass of the proton plus the mass of the electron plus the mass of the neutrino divided by the mass of the neutron is about 0.1% it's a tiny number so the phase space for a neutron to decay is very tiny and the decay happens via the W boson which is a weakly interacting particle so the decay is very slow so the lifetime tau Neutron again I don't know the exact numbers but it's about 10 minutes which is very short on the timescale the age of the universe but hugely long on the timescale of most elementary particles the Higgs boson decays in a Zepto ii remember so that's because of this conspiracy where the neutrino with the neutron is just a little bit heavier than the proton so neutrons can live a long time again you know cosmologically speaking that's not a long time but that's why you can find neutrons out there in the world and before going on so the thing that will go on to is to say that once you can combine neutrons with protons then they can live forever in the right circumstances so the you can have neutrons more than ten minutes past the birth of the universe okay but what I want to mention is that you know this is a weird fine-tuning in the laws of nature you know I'm not gonna say that God did it because I don't believe that's true but I'm not gonna hide from the fact that in the standard model of particle physics there are some weird coincidences going on and these weird coincidences seem to us to help us exist there's some other weird coincidences have nothing to do with our existence so you know and it's not don't make too much of it but what if you know what if the masses of the particles were just slightly different where the interaction strengths were slightly different so that the mass of the proton was greater than the mass of the neutron right now the mass of neutron is a little bit bigger than the mass of the proton what if it were the other way around it's very easy to imagine jiggling with the masses of the quarks to make this happen okay because we have no principle from which to derive the masses of the quarks so we can at least easily imagine a universe in which neutrons are a little bit lighter so in that case protons would decay into neutrons because protons would be heavier if the protons were you know enough heavier they could spit out a positron and turn to a neutron and that would happen and the positrons that were created by decaying protons would annihilate eventually with any electron so we're out there and then you be left with a world of neutrons there would be no protons around so because neutrons are a little bit heavier than protons you end up with a rule where there are both protons and electrons and then complicated things happen to make sure there are some neutrons lying around also but at least there are two different kinds of particles protons and electrons that have electromagnetic interactions and that's as we're gonna say soon that's what makes the world an interesting place if neutrons were lighter than protons you would have no charge particles lying around you would just have neutrons and then the question becomes can you make stars can you make life can you make anything interesting in a world that is just made of neutrons and the answer might be no but you know but I don't know for sure like you can't make life as we know it if the world were nothing but neutrons but could you make other things that I cannot quite conceive of because my brain is too tiny and I don't have the ability to envision what life would be like in a role was nothing but neutrons I don't know that's it's interesting and worth thinking about but this is a feature of the world is that the proton is a little bit lighter than the neutron and thank goodness for us being here okay the in the real world this is the fake world the world neutrons in the real world neutrons can be stable if they're inside certain kinds of atomic nuclei so stable I mean never decays nuclei are just collections of neutrons protons stuck together with it's basically we're not gonna go into this but again another whole area of physics that many many people devote their lives to is nuclear physics right all we've said is that protons and neutrons are made of quarks and if the quarks inside the protons and neutrons are held together by gluons but what that leaves is a little bit of extra force that can actually stick protons and neutrons together so it's much like even though atoms are neutral even though you know two hydrogen atoms are neutral you might say well they're electrically neutral there's no force between them but actually is a tiny force between them because a little leftover remnant force the two hydrogen atoms wanted to come together as well discuss in just a second likewise even though to a neutron and a proton are colorless there's still a little bit of remnant nuclear force that wants them to come together in fact it's pretty strong as it works out so that's how you can make atomic nuclei so for example the deuteron here's an example of a deuteron which is one proton and one Neutron stuck together you can never accurately draw this deuterons are actually very very close to spherical neutron and the proton are sitting right on top of each other in the deuteron they're not like here's the proton here's the neutron and some dumbbell shape okay but it's hard to draw that so you always draw it this way this is the deuteron it's a isotope of hydrogen you know I'm not gonna remind you of all the chemistry in the world but we classify nuclei by the number of protons and so this has one proton and it's as a kind of hydrogen the deuteron and you can figure out you can actually go either measure it or do ab initio calculations and nuclear physics and you find that the mass of the deuteron is I gotta look this up one eight seven 5.6 MeV okay close to twice the mass of the proton or twice massive neutron but not exactly and then you can say well can it decay right this is the game that we playing say like well can the neutron in that proton in that deuteron decay well it would decay into a proton presumably and then you have two protons and two protons cannot stick together that's a lot more energy than just two protons individually because they have electromagnetic repulsion the strong nuclear force would like them to come together but two protons without any neutrons hanging around the strong nuclear force loses that battle and the electromagnetic force pushes them apart so that Neutron has to decay into a proton and that proton has to go its own way so they have to be separate so you compare the mass of the neutron of the deuteron to the mass of a proton Plus what the neutron decays into proton plus an electron plus an anti neutrino and that works out to be one eight seven seven point 1mev so in order for the deuteron to decay would have to decay into particles that are heavier than it is which means it doesn't happen which means the deuteron is stable that's why and you want to say well why is the master on that that's too complicated that's above our pay grade for these videos but it's the the combination of many many things going on inside the Deuter on the strong nuclear force the weak nuclear force the masses of the quarks the whole shebang the point is that under these circumstances and in heavier nuclei as well the deuteron can in fact be stable and in fact logic like that leads you to all the isotopes all the isotopes in the periodic table the elements right so what we care about here you know the periodic table is what you care about if you're a chemist because the periodic table the columns in the table are telling you something about the chemical properties of the atoms but if you're just dealing with the nuclear physics it's the isotopes that matter to you not the individual chemical elements and it turns out and I had to look this up how many stable isotopes are there would you guess do you know any nuclear physicists out there in the audience there are about 250 stable and I'll put stable in quotes isotopes and that's because why is stable in quotes because you know this is a really close battle as you see from you know the closeness of these two numbers for the deuteron and it's its purported decay products on the one hand when you try to make a nucleus you're already fighting against the fact that protons are positively charged and neutrons are neutral so there's no negatively charged particles in the nucleus so there's a repulsion like charges repel protons do not want to be brought close to each other that's why nuclear fusion is hard and why we do not have effective cheap fusion energy powering our reactors ok because getting the protons close to each other is very very difficult on the other hand you have the fact that if it works the energy the mass can be a little bit lower so they want to be there so they want to be there but there's a barrier that's why nuclear fusion is hard and when and when I say they want to be there it's not by a lot like the deuteron is not that difficult to break apart you know a strong gamma-ray hitting a deuteron can just break it apart pretty easily so the there's this combination where the strong nuclear force wants the baryons to come together the electromagnetic repulsion pushes them apart you need some neutrons in there because neutrons will give you some extra strong nuclear force but too many neutrons will just decay because neutrons want to decay so there's all this combination this complicated combination of forces counteracting each other and that's why you know that it's complicated to do nuclear physics and the reason why to finally finish this sentence the reason why it's 250 stable nuclei is there are 250 isotopes rather 250 isotopes that as far as we know would never decay in an observable amount of time okay we think though that only 80 of them or so are truly stable so by which we mean there's another you know 170 which will linger around for many many many many many years and then eventually decay that is what we think will actually happen anyway that's this is the reason why I'm doing this is because these are the low energy allowed stable particles in the standard model particle physics so well we're left with is I said what we're left with is this stuff right but then we had to go into some details about how the baryons get together so the world the world of you and me and the tables and the Sun and the moon and stars is made of electrons around 250 stable isotopes neutrinos you know they exist they're out there but they pass right through you writing you probably heard this fact like a neutrino that it comes out of the Sun will probably pass right through the entire earth without ever being stopped because it's nuclear it's a weak nuclear interaction is so weak so even though neutrinos are there they don't affect our lives very much and so let's let's get down to the physics of our everyday lives literally the table and chairs our biology and things like that so forget about the neutrinos forget them and then you have this is the matter of the world and then you have the forces which are electromagnetism right photons and gravity and those are the forces and that's it that's the world this is the world again that you and I are made out of there are we're relieving some bits out in this very very simplified discussion because they're basically what we're leaving out is the weak nuclear force and neutrinos because they're very rare and they don't have a lot to do with what we're what we care about everything else everything else that you make from the standard model either decays away very quickly or interacts with us very very weakly so we don't need to worry about it so it's interesting that this is sort of the leftover low-energy remnants of the standard model of particle physics it was it's a complicated story to get there that we just raced through an incredibly high speed but you know everything in the world that you encounter in your everyday life unless you're a working physicist is made of this stuff so you know not just tables and chairs volcanoes and hurricanes and bacteria and plants and people psychology art literature music sound and light it's all some combination of this stuff in interesting ways of course the ways are very very interesting and if someone said you know write a sonnet or write a symphony you would not start with the standard model of particle physics and try to drive it from first principles that would be another video that we'll talk about but these are the ingredients this is all you need and that that's kind of amazing I'll name one more fact I want to talk about mostly some put that putting things these together now to get atoms and so forth but an extra fact is there is an asymmetry in imbalance between matter and antimatter thing is fact right there's more matter in the universe than antimatter in fact you know we don't even know that for sure you know it's really a symmetry and baryon number that we know about so we know that in the observable universe there's a lot more baryon number than anti variant number why not because when you say matter and antimatter I mean you mean something like lepton number plus baryon number is matter anti lepton number and anti barian number is antimatter we know the baryon number of the universe because baryons are protons and neutrons and they're very easy to notice we can find them fairly easily but lepton number an anti lepton number can be hidden in neutrinos and the total number of neutrinos in the universe is very hard to count so what we know is that in the charged particles and then the strongly nuclear force interacting particles there's a big imbalance between matter and antimatter but maybe it's made up for in the neutrinos that we don't know but there's certainly an imbalance in baryon number we don't know why so there's two possibilities and one of them is not very plausible one possibility is that somehow the universe is born with a slight imbalance between baryon number and anti baryon number that's hard to imagine it being true you have to do it in exactly the right way because barring on number even in the standard model is not a hundred percent super-duper conserved under the right circumstances it can vary but also it just seem weird like why should there be an imbalance the other is exactly because we can imagine processes that do violate baryon number it's again full employment for theoretical physicists to invent what we call baryogenesis schemes schemes where in the early universe as it expands and cools there are particles that decay and interact with each other which end up producing a few more baryons than anti baryons you can run the numbers what you need in the very early universe is at very early times when temperatures were much higher than the mass of the proton there was a lot of both baryons and anti baryons and most of them decay away most of them annihilate with each other turn into photons or something like that as the universe expands and cools what you need is roughly speaking for if I'm gonna get the number right for every 10 billion anti baryons you need to have 10 billion and one baryons at very very early times so all but one of every ten billion baryons and anti baryons annihilate away and you're left with the tiny little remnant which makes up all the stuff that we see today so I'm not going to talk about that but that is something that you need you need to understand why all these particles why there's this imbalance there we don't really know ok so here now we're gonna reach sort of the punchline of really what I wanted to talk about so these are our ingredients for the physics of everyday life electrons stable nuclear isotopes electromagnetism and gravity ok the weak nuclear force is too weak the strong nuclear force is only in the isotopes don't need to worry about those the Higgs boson is far too weak the heavier fermions decay away this is what we're left with so there's only two kinds of matter right nuclei and electrons and there's only two forces two big long-range forces that are important in the everyday world so think about those forces just a little bit there are only two of them and one of them is gravity and gravity I'm gonna hate to say this but gravity is dumb I don't mean that it's dumb to think about gravity or to care about it I just mean that how gravity acts on the world is simple it pulls things together there's slight complications if you talk about dark energy or something like that or inflation in the early universe but again we're trying to understand the everyday world we're trying to understand what's happening right here right now in the room that you're in okay so the pen Falls toward the earth that's all that ever happens with gravity just tracks things together with an in square law it's incredibly simple okay whereas electromagnetism is interesting let's say it's clever I just made that up right now but I think it's true and the reason why you know the reason why is when we talked about gravity we talked about the principle equivalence right all particles fall at the same rate in a gravitational field not only is all the gravity does is pull things together it pulls everything together in exactly the same way whereas enm electromagnetism acts on you differently depending on if you're positively charged negatively charged or neutral so E&M can both push and pull it pushes it pulls things together if they've opposite charges it pushes them apart if they have the same charge so what that means is what electromagnetism can do has an infinitely greater variety than what gravity can do because you know gravity you you might think it's just like you know gravity does one thing and electro nate ism does two things so how much more important can it be but you can balance you can play them off against each other and in fact the world does that then the entire reason the world is interesting can ultimately come down to the fact that electromagnetism is clever because there are positive and negative charges in the world so this explains you know this accounts for electricity a Hall of electricity comes down to this fact electricity comes about because you know you have these atoms will pop at atoms in a second but atoms with these heavy nuclei and very light electrons and the electrons can be pushed around because they're much lighter than the nuclei and they're charged so they can be pushed around by electromagnetic fields so if you just gather together a bunch of electrons so you have minus charges on one side of something and then end or oops combine a bunch of positive charges on the other side but photons over here okay then if you put an electron in between it's gonna zoom over to the positive charges and we call that electricity okay so in the very very likely condition that you are currently watching this on an electronic device you should thank your lucky stars that there are positive and negative charges in the world because that's what lets us manipulate the electrons going through that device to create electronics and electricity okay it's ultimately because of this feature of the standard model of particle physics the other thing this explains is chemistry you can tell that we're not going to go into details in any of these higher-level concepts but I want you know to connect them to the underlying world beneath chemistry is again there's a push in the pole but in this case it's a little bit more subtle I mean electricity is very subtle also like once you had the superconductivity and all this stuff extremely subtle or even circuit boards for that matter but I want to talk about the subtlety in chemistry because it harkens back to our discussion of the pallidly exclusion principle right so just think about you know eg a hydrogen molecule so hydrogen molecule just two hydrogen atoms so the point is that let me draw it this way whoo it's not very good but okay there's a proton another proton and in this cloud or two electrons okay the point is that around one hydrogen atom you could imagine you can put one electron no problem around one nucleus there's still room for one more electron in there as we'll discuss in a second so in a sense there want to be two electrons hugging that single proton but there's not enough electric charge to make that happen right once you have the proton and one electron it's done attracting things roughly speaking but if you have two hydrogen atoms they're happiest the electron sort of wanted to combine the electrons want to both be hugging either one of those protons they want to pull them together but of course then the protons begin to push things apart right the protons have a pod electric charge and you know there's also the pala exclusion principle so you have to have the electrons lined up in the right way and what you get at the end of the day is you can have a potential energy and this is this are here is the distance between the two protons okay so you can say what is the what are the forces acting on the protons if they're very close together the protons push each other apart okay there's electrons but the electrons are all spread out around them so they're not going to help that much in ameliorating the electric repulsion between the protons so it costs energy to go very close by but also if they're far away they want to be a little bit closer so what you get at the end of the day is a curve that looks like this which says this is the potential energy between the two protons and there's a favorite place to live there's a favorite distance to have between those two things and it's all because of some complex interplay of electromagnetism and the pellet exclusion principle okay and so this is why you can get molecules sticking together while you can get two atoms that want to come together okay it's again ultimately because of quantum field theory in gauge theory and other things like that they wouldn't have told you that in your chemistry class but chemistry is just applied electromagnetism in a world that has the Pauli exclusion principle in it so let's actually let's let's talk about that in a little bit more detail let's finally get to atoms we're like more than an hour in and now we're into the to the video and we're finally getting to the to the title atoms so we have of course hydrogen atoms which is just one proton plus one electron the simplest one there can be isotopes there can be ions you know all that stuff we're often get into that but basically it's the simple thing you know the electrons have wave functions as we discussed before but you know what hydrogen is about helium okay so by the way for hydrogen if you have a deuteron instead of a proton so if you have the combination of the neutron and approach you get basically the same hydrogen you get what we call deuterium but chemically it's the same it's the electron that is doing all the chemistry this is the point of this little monologue up here is that the electrons are doing the work in chemistry the protons are being pushed and pulled but it's the electrons that are doing the pushing in the pulling the protons interacting themselves or just going along for the ride so so hydrogen with a deuterium in the in the middle the Deuter on in the middle sent mr. proton is pretty similar a little bit heavier heavy heavy water right heavy hydrogen helium two protons two neutrons two electrons and something is already happening interesting with helium because of physics because of the power of the exclusion principle right so the poly exclusion principle remember says that two identical particles cannot be in exactly the same quantum state okay so if you have a helium nucleus this is our little helium nucleus two protons two neutrons and I'm just gonna like do this terrible sort of Rutherford atom kind of picture that you know is not right but it gets the point across two electrons like that okay really the electrons have wave functions really the electrons want to be in the lowest energy wave function they can be in but they can't be in exactly the same wave function because that would violate the Pauli exclusion principle because electrons are indistinguishable particles okay happily happily for life and for chemistry sorry poly solution principle no two identical particles can be in exact same state happily electrons head spin okay so these two electrons have two spins and all you need to do to put them in the same shape of the wave function is to let the spins be oppositely aligned one spin up and one spin down or as you know from our explorations of entanglement you could say spin right and spin left but they're oppositely aligned they're entangled with each other in opposite directions so the electrons in helium have opposite spins so you can put two electrons with wave functions that have the same shape as long as their spin wave functions are different that is satisfying the solution principle okay but then you're done in terms of this thing that electrons can do you can't put a third electron in there doing the same thing there's only two values for spin spin up and spin down you've used it up the electron is a spin 1/2 particle ok so now this is the origin of why Heydrich of why helium is a noble gas why helium does not interact why there are not helium molecules the helium has its electrons filling the thing that they can fill the those two electrons are in their lowest energy state the lowest energy shell as we would call it and that's all you can fit there there's no more room for interesting chemistry the electrons don't want to be in someone else's orbit or anything like that like the hydrogen atom did the helium electrons are perfectly happy where they are so helium is roughly speaking non interacting chemically but we can keep going what's the next one beryllium three beryllium three four three protons atomic number three okay in fact I'm not gonna do believe me I'm not gonna do the whole periodic table the elements from beryllium up to neon okay this is filling the next shell of electrons and we can actually roughly appreciate why that's true you know any now I've been previously apologizing to mathematicians and particle physicists now I will apologize any chemists in the audience because we're not going to do justice to all the complications here but roughly we can understand why this makes sense the point is that when we did electron wave functions right the electron wants to be close to the proton and so what we can do is to plot as a function of distance from the proton we can plot the electron wave function Tsai and the lowest energy one looks roughly like this okay and that's both of the helium electrons are gonna be doing that in space Tsai as a function of R so what's next what is the next highest energy thing so we cannot put any more electrons in that lowest energy level and it turns out there are two different things that you can do so what you might guess is that you you can sort of let the thing what should I say I'll just tell you the answer and then I'll back up and justify it okay here's the answer what I will plot here is a wave function that actually looks like it shouldn't be the next highest one and then I will separately plot over here a different thing but instead of R which is just the distance from the center I will write X because what I mean is the specific direction in space X and then I will plot what you probably were expecting so this is a wave function here that only crosses zero once the yellow one over here crosses it twice and so what you're thinking is well it costs energy for a wave function to change for a wave function have a gradient okay so when an electron wants to be in his lowest energy orbital it wants to change is gradual as possible its wavefunction so that's clearly what the white one does it changes very very smoothly the green one changes a little bit more the yellow one changes a little bit faster and as you go up and up and up at energy you'll get more and more Wiggles in the wavefunction that makes perfect sense but it turns out that the yellow and the green are of approximately equal energy and the reason why is because the same reason why I wrote R over here and X over here this yellow wave function is symmetric you notice that as you send R goes to minus R it looks exactly the same and in fact it can be spiritedly symmetric so it can vary in the r direction but there's no variation going on in the XY or z directions it's a perfectly spherical e symmetric thing whereas this green one over here changes sign as you go from left to right so it can't be spherical e symmetric and very roughly speaking if you've ever seen the pictures of you know the nucleus and then different electron orbitals so there's an orbital these orbitals look like this and if I can do it correctly well I can't do it correctly here but it's spherically symmetric that's all I'm gonna get across whereas these orbitals you've seen pictures that look like this where they're like P orbitals oops that's not the one I wanted they look like they're double-lobed ok and guess what they can be doubled in 3 different directions so if I count how many ways so there are two orbitals like this two states why because they're two spins only one spatial wave function but two different spin alignments here there are three different orbital wave functions one with the two lobes in the X Direction y direction and Z direction and then there are two spins for each of them so there are six states for this so there are a total of eight states for the electrons in these next level orbitals so when I hope is that the numbers work out correctly so I said that hydrogen is one helium has two electrons and this next shell goes from beryllium to neon so that's from three to ten inclusive so that's eight different elements and exactly what we got the eight states there okay so all this is a very very fancy way of saying that all that stuff you learn in chemistry is ultimately because of features of particle physics in some sense now you don't need to know all these features of particle physics typically in high school people take chemistry before they take quantum mechanics but there is some relationship there it's not completely separate okay and from there you just keep going you just make things more and more complicated and there's a complicated story of how the different electron orbitals get filled etc and that's you know the life of a chemist so just show you one example carbon which has six protons so if the six protons have six electrons attracted to them two of those electrons will be in this lowermost helium like orbit or hydrogen like if you want and then four of them will be in the next shell the next set of orbitals and so if you have four in four of these eight are filled so you have four filled electron states in the orbitals and four open open for business and that's why carbon is interesting that's why carbon is the backbone of life because it has the most number of interesting things going on it has split its electrons it has four electrons to play with and it has four electrons it can take so it's sort of maximally interactive so you end up doing what what is called organic chemistry okay so you have you know carbon atoms sticking to each other and then also other atoms so typically the simplest thing in the world is to put hydrogen atoms everywhere right to get hydro hydrocarbons but you can do other things you can put like an oxygen atom and if you go through the little thing that we did there oxygen has two open slots and you can finish that so that's a nice little example like this is a very famous molecule that you could look up of an organic chemistry molecule we're not gonna do organic chemistry any detail we're not gonna do chemistry in detail we're done with chemistry that's what I wanted to tell you about chemistry what I wanted to tell you about chemistry is it all comes down to electromagnetism and a poly exclusion principle it's all just an application of that okay one final thing one final thought before I let you go for this video here and the final thought is I'm gonna write down very explicitly here because this gets very easily misinterpreted if quantum field theory is basically correct you know we never know right quantum field theory is by far and away the best currently applicable theory we have explaining the world at a fundamental level it might not be completely correct in fact what we know about quantum gravity suggests the quantum field theory is not completely correct but quantum gravity is very far away from our experimental reach so again if we're trying to explain the world at the everyday then quantum field theory seems to be a good way of doing it then we will never it's very hard to say never in physics but this is a conditional sentence if quantum field theory is correct then we will never discover new particles or forces relevant to everyday physics what do i mean by this by everyday physics I mean the stuff that you literally see around you right now given that I'm presuming you are not working in a particle accelerator or a telescope or anything like that the stuff that you're touching ok the stuff that you're made of yourself everything you're visibly seeing with your eyes or you know touching with your fingers that's everyday physics the physics of tables and chairs planets and stars stuff like that ok we know what that stuff is made of it's made of the list that I showed you before the electrons the isotopes electromagnetism and gravity that's what you need if you want to extend your definition of everyday physics to include you know why the Sun shines for example ok we can put the nuclear forces in there and you know that's fine we need neutrinos to make the Sun work etc but it's still within the standard model of particle physics and the claim here is that in terms of that in that very very narrowly prescribed area everyday physics we're done we have discovered the fundamental ingredients we're not going to find anything new now of course we're going to find new physics more broadly like we don't know what the dark matter is right we don't know why is a imbalance between baryons and anti variance in the world there's plenty of things we don't understand we certainly don't have same quantum gravity or the origin of the universe or things like that physics is not done but everyday physics has its complete set of ingredients so I don't even wanna say everyday physics is done because the way those ingredients combine is very complicated we don't understand it right we don't understand superconductivity for example there's plenty about chemistry or biology that we don't understand if you haven't noticed right so I'm not saying that all of those things are understood I'm saying we know the ingredients are I'm saying that whatever the explanation for high-temperature superconductivity or for biology turns out to be the origin of life it will not involve ingredients from fundamental physics over and above the ones we've discussed here and the reason why is because if there were new articles and forces and quantum field theory describes them and then we would have discovered them so there's a symmetry of quantum field theory called crossing symmetry and I think that I mentioned this in passing but maybe didn't give it this name crossing symmetry says if you have a Fineman diagram describing some interaction between particles and it has a certain strength so let's imagine there is you know here's an electron and this is an electron you know in your brain okay it's part of you part of your consciousness right and someone says well I think that there's another particle called the X particle and it interacts through some new force call it the Y force with electrons and understanding this new force is crucially important to understanding consciousness or the origin of life or why tables are solid or something like that okay yeah that's a perfectly legitimate hypothesis you can think that you can suggest it you could investigate it but we have a Fineman diagram so we can calculate the strength of this interaction how likely is it that an X particle will interact with an electron and crossing symmetry says I can take that diagram and I can rotate it by 90 degrees and I get another diagram which has the same strength which is just as noticeable as this diagram is and when I do that rotation of course particles become anti particles if they go from one side of the diagram to the other so this is saying that I could take an electron and a positron a minus and E Plus and I can smash them together to make a y boson which will then decay into two x bosons or an accident anti expose on and we've done that this is what we do is if a particle physicists love the dus smash particles together and look to see what comes out so we have very strong constraints on where particles are we know there are certain kinds of particles you can imagine existing that definitely don't exist so there's no question to get if quantum field theory is right quantum field theory is not right all bets are off but that was the presupposition of the argument of course there are particles and forces we haven't found yet but we know that because we haven't found them yet they're either particles that are too massive to be created okay in collisions like this up to Large Hadron Collider scales or they are too weakly interacting to be created and so this diagram may be it exists but the actual numbers attached to it are just incredibly tiny or the particles just decay away so fast that even if they're made you don't notice that they were made in any one of those cases there's no way for this new particle and forests had any impact on our everyday lives unless your everyday life is that of a theoretical or experimental physicist okay and this fact - you know sometimes I stated if you read my book the big picture I go into this fact I try to explain it I say the laws of physics underlying everyday life are completely known all the words in that sentence matter okay its underlying everyday life it's not of the emergent laws of higher levels I'm not saying you understand economics okay but I understand the electrons and the nuclei that economists are made out of and they're they're completely known in the realm of everyday life not in the realm of the universe I'm not saying we know where the universe came from I'm not saying that physics is done I'm a physicist how could I ever say that physics is done I would do something different if I thought the physics was done but the laws of physics underlying everyday life are completely known and this fact is reflected in technological advances okay now we sometimes think that you know doing work in fundamental physics is crucially important for technological advances and it is but only because we need technological advances to do fundamental physics and therefore the drive to do fundamental physics leads to new technological breakthroughs but the technological breakthroughs themselves do not involve new fundamental physics the last time new fundamental physics new particles or forces turned out to be relevant to technology was probably the 1950s you know the top quark in the higgs-boson these things are not things that affect technology in any way because they you need a billion-dollar accelerator to take them and then they decay away in ten to the minus twenty some seconds okay and that's gonna continue to be true there will be plenty of technological advances but the technological advances will consist of clever ways of arranging these ingredients electrons isotopes electromagnetism and gravity and that gives us constraints on what we can do again if quantum field theory is correct it means that you can't bend spoons with your mind no I cannot bend this pencil just by thinking about it other than having my mind you know say that my arm should go there and Bend it but there's no way that a force can be extended from my brain because the only forces that go over large distances are electromagnetism and gravity okay it means that tractor beams will be difficult to construct not necessarily impossible but you'd have to do them out of electromagnetism there's no new forces shields and you can put up around your spaceship to protect you from laser beams well if you can do that with electromagnetism that's great gravity is too crude gravity is dumb right electromagnetism maybe you can do it but there's no other forces no other particles that will be relevant to this sorry about that but you know it's our job here not only to discover cool new things about the world but to face up to them to accept what the world is teaching us so there is both a frontier of moving beyond everyday physics the Big Bang quantum gravity Dark Matter etc and there's another frontier of how these ingredients come together to form everyday physics logistical mechanics chemistry biology psychology all that stuff there's plenty more science to be done but we should also kind of recognize that some of the science we wanted to do we actually have done

Channel: Sean Carroll

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Id: yj_ckNi_DCA

Length: 82min 21sec (4941 seconds)

Published: Tue Jul 21 2020