Science & Technology Q&A for Kids (and others) [Part 129]

Foreign. Welcome to another episode of Science and Technology, Q and A for kids and others. And I see all kinds of questions here of different types. Let's see, I notice one here from Katie. Why is it important that the periodic table is structured as a table rather than a list of elements? Well, let's talk about what the periodic table is. It's essentially a list of all the kinds of atoms that can occur in nature. So atoms have a nucleus that contains protons and neutrons, and then outside the nucleus, far away from the nucleus actually, are electrons. And the chemical properties of materials are all concerned with the way that the electrons interact with each other. The nucleus sits there as a tiny little thing. It's like if you have a hydrogen atom, for example, which has just one proton usually at the center, and an electron kind of sort of in this cloud around it, the size of the whole hydrogen atom is 100,000 times larger than the size of the proton in the middle. So it's most. But the question of how atoms kind of behave is determined as far as chemistry is concerned, is determined by the way that the electrons from different atoms interact with each other. When you. When you push two atoms close to each other, there might be. The electrons of those two atoms interact in various ways because they're kind of the outer part of the atom, and they're. What kind of get to bump into other atoms? Well, the. The big thing that determines how atoms behave is how many electrons they have. Do they have just one electron? Two. Up to. In the case of the elements that are reasonably stable, up to 92 electrons. Well, the thing that determines when you have just an atom sitting there on its own, an atom of some particular chemical element, what that the nucleus of the atom will have a certain number of protons, certain number of neutrons. Also, the protons have an electric charge of plus one unit. Electrons always have an electric charge of minus one unit. So in an ordinary neutral atom, just isolated, separated from everything else, you'll have an equal number of protons and electrons. So, for example, for hydrogen, it's got one proton in the center, and that means it has one electron normally. And helium has two protons in the center, so two electrons normally. And so then the question is, what determines the properties of atoms in terms of their chemical interactions? That is, atoms just sort of sitting next to each other with their electron clouds kind of touching. That's determined by the number of electrons in the atom. And the whole story of chemistry is the story of how different kind of clouds of electrons from different atoms interact with each other, whether it's in making water, H2O, for example, that has an oxygen atom, and that has a couple of hydrogen atoms. And the kind of electrons of the hydrogen atoms interact with the electrons in the oxygen atomic. Okay, so there's a very typical question which is sort of how roughly are the electrons arranged around the atom? And electrons get arranged in what are called shells. And it's a little bit. There's a bit of, sort of conflict between the very abstract way of talking about it that's kind of more kind of scientifically correct, and the way of talking about it that's easier to understand, and that works just fine for, for most of the kind of reasoning you have to do in thinking about how chemistry works. But let me talk about the kind of more scientifically correct version of it first. The first thing to understand is that an electron is. Well, in traditional physics, people have thought that electrons are just perfect geometrical points of zero size. Protons are not protons. Everybody knows. Well, people know that a proton is a thousandth trillionth of a meter across, 10 to the minus 15 meters across. That's the size of a proton. It's got quarks and all kinds of other stuff inside it. It's got a definite substructure. But electrons, so far as people have been able to tell, electrons are just points with nothing inside them. And what we know right now is electrons are certainly smaller than 10 to the minus 21 meters across. Well, in the theory of physics that I've been involved in developing the last few years, electrons are no longer thought of as precise geometrical points. They actually have a substructure. But their substructure might be at 10 to the minus 90 meters or something as tiny as that. So really, really tiny compared to everything else we're dealing with. So electrons as individual things, they're like point objects. But when it's very hard to pin down an electron, it's very hard to know, oh, the electron is right here and it isn't somewhere else. And this is kind of partly the story of quantum mechanics, that quantum mechanics kind of says you don't actually know precisely where things are or what things are doing. You just have a whole collection of possibilities. And only when you kind of observe it, only when you choose to make a measurement, are you actually sort of in some sense nailing down, well, this is the definite place where it showed up right now. So what happens in an atom is that they're electrons and each individual electron is like really, really tiny. But knowing where each electron is, you don't really know. So you kind of think of the electron as being in this kind of cloud of electronness. And if you really poked it in the right way, you could say, well, right now when I poked it, the electron is right here. And it's not quite a question of, oh, right now it's here and now, and then it will be somewhere else later. It's really a one shot thing. And that comes up in our theory of physics because in fact, the whole universe is branching into multiple different histories. One history in which the electron is in this place, one history in which it's in that place. And when you kind of think to measure it, your mind is effectively picking a particular history, more or less. And so that's kind of how it works. It's not like it was first there, then it's there. It's like it's in all those places. But when we choose to measure it, when we decide this is our measurement, our mind is kind of homing in on one of those possible branches. But any case, so in the usual kind of theory of physics that's existed for about the last hundred years, there's this notion of a so called electron wave function. The electron wave function is essentially giving you more or less the probability that an electron is at a particular position in, for example, an atom. So relative to the hydrogen, in a hydrogen atom, there's a nucleus at the center, maybe it has a single proton in it. That's the most common case. Then there is an electron wave function. There's an electron, essentially, probability distribution. I'm hedging a little bit because the probability distribution is actually the square of the wave function. And there's a bunch of fancy stuff about the individual so called quantum amplitude. But let's ignore that for now. It's not really relevant for what we're talking about right now. Then the question is, well, where does the electron typically hang out? Where's the highest chance that it hangs out? Well, it hangs out in a hydrogen atomic at a distance that's called the Bohr radius. On average it's about 1/10 billionth of a meter, 10 to the minus 10 meters. And so if you look at the chance that you find an electron somewhere, the chance goes right close to the nucleus, it's not very high, goes up around 10 to the minus 10 meters away from the nucleus. It's at the largest value and then it drops off. It actually drops off exponentially as you go further out. And so in a hydrogen atom in its most normal state, that's just. That electron is. It's got one electron. It's just kind of hanging out. And the chances are it will be found roughly 1 Bohr radius away from the hydrogen nucleus. It doesn't. It's not. That's. So what happens in quantum mechanics is that there are different possible states of the hydrogen atoms. So the state that has the lowest energy is the one I just described, where the electron is, on average, this Bohr radius away from the nucleus. Well, the hydrogen atom has a collection of discrete energy levels. And you can think of them a little bit like the electron has this constraint that at infinity, if you go far enough away from the nucleus, the chance that you find an electron is essentially zero. And it sort of also has a constraint that it, well, doesn't quite have the constraint that it can't be at the nucleus, but it has a constraint that you're kind of getting into the center. And there's no volume at zero radius. There's sort of no volume in which it can exist. It's only as you go further out that there could be. There's sort of space for the electron to be there. So there's constraints on the electron wave function. Those constraints are somewhat similar to the constraints you might have. If you have a string, for example, and you've attached the two ends and you pluck the string. You can pluck the string in such a way that the string bows out just once, in such a way that the string bows out twice, bows out three times. It always has to bow out a whole number of times. But you can get different bowings out depending on how you. How you sort of how you excite the string. Same kind of thing for electrons and hydrogen atoms. What happens is there are these different. What are called eigenstates of the hydrogen atom, where you get these different arrangements of electron wave function. And you'll get ones where the electron is always right in this particular configuration, ones where it's in a different configuration, and so on. And there are a discrete set of these, the discrete collection of those different possible states, the equation in the mathematics of these things. When you look at the equations that are satisfied by this sort of position on a string, that's the thing called the wave equation by the electron wave functions. It's a thing called the Schrodinger equation, invented by a chap called Erwin schrodinger in about 1920, around 1920. In any case, what happens is there are these discrete possible states of the hydrogen atom and the way that they are characterized. Well, let's see. Just like a. Roughly. Okay. And this is, you know, the mathematics is very well defined for this. The intuitive explanation is a little bit fuzzier, but one can sort of describe the different possible modes of the hydrogen atom. The lowest energy one, then the one that's slightly higher energy, where the electron is kind of running around a bit more quickly in some sense, and so on. And very roughly, those different states are characterized by roughly how much whether. Whether the electron is just sort of on average at any. At any orientation relative to the nucleus. So the lowest energy configuration is so called spherically symmetric. It has the. The probability that the electron is any. In any particular position relative. It's like if you had had the. The Earth, for example, as. As if you had the surface of the Earth and you were thinking that the center of the hydrogen atom is the center of the Earth, you could say, what's the chance that you find the electron at a certain longitude and latitude? Well, in the lowest energy state, it has an equal chance to be found at any longitude and latitude. As you go to the next state, the electron is kind of roughly like it's kind of running around more quickly, and it's running around in a definite orientation. So it's either sort of running around the equator of the Earth or it's running around north pole to south pole and so on. And that is the fancy quantum mechanics version of that is it has what's called orbital angular momentum. And you can roughly think about it as kind of spinning around one way or another way. Because of the story of quantum mechanics and the story of the fact that you only have these discrete possible configurations, it basically has, in the case of sort of running. Okay, when it's in the lowest energy states, sort of not running around at all. The next energy state, it's kind of running around in one way and then the one after that, it's kind of running around sort of in twice as many possible ways and so on. Okay. The end result of all of this is that in the case where it's sort of running around in one way, it turns out there are sort of three possible distinct states of the hydrogen atom that more or less correspond to the three different orientations of the. Of the way that the electron is kind of orbiting around, It's a very rough approximation. The mathematics is a little different from that, but that's sort of a rough, intuitive explanation. So there's the sort of lowest energy state and the lowest energy state, it's kind of all directions are equivalent. The next energy state, there's kind of one preferred direction and it can go kind of in any of the three sort of coordinate directions in three dimensions. Okay? Then you get to the next state and it has five possible, that there are five possible configurations, so to speak. The next one, there are seven and so on goes up by odd numbers. Now you might be trying to ask me to give a, give an intuitive explanation. Oh, let's see. The mathematics is not, well, I can say the words of what's actually going on. These are, well, different ways to say it. I mean, they're the representation of the rotation group. They are different. Let's not go down that path. I can explain that if people are interested, I can explain why it goes up by odd numbers and so on. But the basic bottom line is there are the number of possible configurations of electron with lowest energy. One with its next higher energy is 3, next one is 5, next one is 7. Okay, so that's how that works. Those are okay. The next important fact is a thing called the exclusion principle, which says that if you're putting more electrons, if instead of one looking at a hydrogen atom, one looks at a carbon atom, for example, one like looks with six protons in its nucleus and six electrons that would sort of naturally be. Around it. Did I get that right? Let's see. Hydrogen, helium, lithium, beryllium, boron, carbon. Yes, carbon is 6. Nitrogen, oxygen, fluorine, neon, et cetera. So in the case of a carbon atom, there are six electrons that you have to kind of put into these different possible states. So there'll be electrons that are in that lowest energy state. And then you can put electrons into other states. Okay. Important fact about electrons, they don't like each other in the following sense. Once you have one electron in a particular energy state, no other electron is prepared to go into that same energy state. Actually, it's a little bit trickier than that because an electron has two different so called spin states. Roughly, the electron can be oriented so that it is sort of spinning on its axis in some sense, except it doesn't really have an axis, it doesn't really spin. But it has a thing that's called spin. It has a property that's called spin, and it can either be sort of in the up direction or the down direction. There are two possibilities. So when I say there's that no two electrons could be in the same state. Actually, if you account for the fact that the electrons can be either in their sort of spin up or spin down configuration, it means two electrons can go into a single one of these energy levels that I described. So lowest energy thing, the spherically symmetric one, there can be at most two electrons that go in there. And that one can, that is sort of the lowest electron shell is the electrons that will sort of go into that lowest energy configuration. Okay, you put another electron in. Where's it going to go? Well, it's going to go to the next kind of energy level, which is this thing that I described that has three possibilities. That is kind of the electron with a certain, with essentially one unit of orbital angular momentum. And so for that shell, there are. Am I getting this right? That shell there should be the. That there should be six possibilities. Yes, I think that's right. And then the next one up, that has five possible configurations. Okay. There are, there are two possibilities for each electron. So there's 10 possible configurations of that and so on. So as you keep trying to have atoms with more and more electrons, those electrons are sort of going into these higher and higher shells. They are going into energy states that correspond to sort of. They're going to these sort of higher energy states that progressively a little bit further away from the nucleus and have these other characteristics. Okay, so what is the periodic table? Well, the periodic table, not that Mendeleev knew this when he made it. He just made it based on sort of the properties of chemicals and so on. But what it ultimately is, is it's something where you're lining up cases where the number of empty slots in the outer shell of the atom is the same in a particular column. And why is that important? Well, because in the chemistry of atoms, what matters is these atoms kind of bumping into each other and trying to form so called bonds, bonds, the most common kind of bonds, so called covalent bonds, come about because essentially electrons in these two atoms are kind of getting exchanged with each other. And that happens because there's a kind of a, in this outer shell, kind of an electron from the other atom could go. If there's a hole in that outer shell, if it isn't quite full, then an electron from the other atom can kind of like spend a little bit of its time. If those atoms are right next to each other, can spend a little bit of its time in the position of the place where it would be for the other atom. But if the shell is filled, then there sort of isn't a place for another electron to get in and kind of have that other atom sort of poke its electron into the electron cloud of the other atom. So when you have a closed shell, it's kind of very hard to have a chemical reaction with something that has a closed electron shell. And in other words, when all the slots are filled, the only way that you can sort of add an electron to that atom is to go to the next shell, which requires you to have a higher energy electron and so on. So that means that atoms that have closed shells tend to be pretty non reactive. And if you look in a periodic table, on the right hand side of the periodic table are the noble gases, which are helium, neon, krypton, xenon. Am I missing one? Those, I think those are. Am I missing one? I may be missing one. But any case, those atoms correspond to the filled shells, to cases where the number of electrons is enough to fill a shell and those atoms are not reactive because another atom, when it comes near it can't poke one of its electrons into the, into a sort of an empty space in the electron shell. So in general there's this notion of valence. And valence is kind of the number of holes. Oh, I thank you. Somebody pointed at argon, I forgot argon. My apologies. The. So in any case, the, the, this question of sort of how many, how many holes are there in the outer electron shell is what determines kind of how much poking there can be from another atom. And roughly that that ends up determining the so called valence of the. I think that the way to think about this probably is maybe the other way around of kind of how many electrons are there kind of hanging out in that outer shell where there's still holes left in the outer shell. But any case, so hydrogen has valence 1, carbon has valence 4, for example, et cetera. And that determines that that's sort of basic chemistry, determining kind of what chemical compounds are easy to make. You can have kind of carbon and it can have four hydrogens sort of being nearby because the electrons from those four hydrogen atoms are kind of sticking themselves into the kind of holes in the outer electron shell of the carbon. Does it actually work out that way? Let me just think about that for a second. I'm not sure I've ever worked it out quite like this. Let's see. Carbon has six electrons, and so it has. Of those six electrons, two are in the inner shell. So then it has, it should have four electrons in the next level out and there should be. In. There are three. That doesn't quite work out. Something is slightly off here. I need to. But I'm giving you at least a qualitative explanation of what's going on? I think my. Either my arithmetic or something was off a bit here. But in any case, the. So the point of the periodic table is it's kind of this map of how many sort of how, how many spaces there are and how many extra electrons there are in this kind of outer electron shell at. For each kind of atom. And that determines kind of how those atoms will interact with other atoms, because it's the outside of the electron affects this sort of electron cloud that bumps up against other atoms and is important for chemistry. And so the arrangement of the periodic table is all about that. And the reason, you see, the thing has sort of a small number of. On the successive rows correspond to the filling of successive electron shells. And so at the very top, you've got kind of hydrogen, helium. That's the very first electron shell. And there's just two elements there that. Then you get to the next electron shell and you should have more elements across. And I'm not visualizing my periodic table very well. And that's the next electron shell and you keep going down. And of course, when you. As the number of electrons that fit in the electron shells go up, it means you'd have to have more and more and more things across the periodic table to represent all the different possible numbers of things that can be missing in these electron shells. And so that's why this sort of, this extra pullout of the lanthanide series and the actinide series are kind of these things from one of the larger electron shells that has more slots in it, and you're kind of representing all the different configurations there. Now there are some more details because there are, oh, there are subshells as well that are important for the way that these atoms can interact with. So one thing, the one comment about this is you might ask, well, these atoms with all these electrons and all these complicated electron configurations, how do you work out how these all work? The answer is it's really hard. For the hydrogen atom, it was figured out 100 years ago how the electron, the probability distribution for an electron and a hydrogen atomic, by the time you get up further down the periodic table, where you've got, you know, let's say 50 electrons in, in the atom, it's really difficult to figure out what the probabilities are for the positions of all of those electrons. And it's been a major kind of challenge of, of computational chemistry and so on to be able to work all that stuff out. It's. It's still really hard to do. And the, the thing that, and the reason it's hard to do is if it was just asking, where is a single electron going to be in sort of the excited states of a hydrogen atom? That's, that's easy. The difficulty is when there are many electrons that are all interacting with each other, they all have electric charge. Not only they have electric charge, they also have exclusion principle idea that prevents the two electrons from sort of ever being in the same state together. Taking account of all those things makes it a really difficult computational problem. And it's been really hard to work out the full kind of details of all of these different electron configurations. And it's sort of something of a black art to figure out. If you have, for example, one would like to be able to ask, I got a bunch of atoms, are they going to all bind together to make a chemical compound? And what chemical compound will they make? How will the atoms be arranged in the chemical compound? That question is answerable for small numbers of atoms, but by the time you're above 100 or so, atoms becomes really hard to answer in a precise way. It's answerable when you make certain approximations. For example, if you just say, like, in your average kind of sort of theoretical chemistry kit, you'll just have a bunch of balls with a bunch of sticks that correspond to the essentially valence electrons that can be sort of exchanged with other atoms in that kind of model, you can say, oh, yeah, you've got this thing where you can arrange. It's kind of, you know, there's a carbon and there's two oxygens or something, and that makes carbon dioxide, and that's all good. Or you can make oxygen and it has two bonds between two oxygen atoms, and it makes O2 the standard version of oxygen. But the. Then there are all kinds of exceptions, like, well, how exactly does ozone O3 work? How does some, oh, I don't know, xenon hexafluoride. It's a compound of xenon. Xenon is a noble gas which supposedly doesn't make compounds because it just has this closed shell and so on. There are all kinds of weird exceptions. Those weird exceptions that don't work according to the standard kind of high school chemistry rules come about because the actual story of where the electrons are going is considerably more complicated than just this counting of valences and things like this. And that's the thing that is difficult to work out computationally and still challenging. And if you ask the question, can there be a compound? I don't know. Can there be a gold compound? I don't think they're any known, but maybe there are. But xenon, for example, one might not have known that it was possible to make a compound, to make a molecule where something had stuck onto this xenon thing. But it is. So let's see. Well, that was a bit of a long story about periodic table and people. The real point of the periodic table is that things in a given column sort of behave in some chemically similar way because they have a similar number of kind of valence electrons hanging around or similar. And that's the main story of the organization of it. And you can ask questions like, okay, are there things like periodic tables for other types of things? For example, what about atomic nuclei? So we talked about what happens when you have electrons, when you have chemistry. Chemistry is about whole atoms with their electrons bumping into the electrons of other atoms. But in nuclear physics, one's concerned with nuclei. And for example, one might be concerned with what happens when two nuclei bump into each other. Most of the time, nuclei are kept far apart by the electron clouds in atoms and so on. When you're, you know, if you want to have nuclear fusion, for example, the whole thing that's happening, for example, what powers the sun and so on, is that nuclei can get crushed together and then fuse. And so you can ask questions like, well, are there analogs of the periodic table for nuclei where you can say that the properties of nuclei will be the same for particular nuclei would be the same as other ones. In atoms, the most important thing is how many electrons are there. For nuclei, there are two important things. How many protons are in the nucleus and how many neutrons are in the nucleus. And roughly, there are a bit more neutrons in a nucleus than there are protons, particularly when you get to heavier elements, kind of like the protons, they're all stuck together. I think I've talked about this another time. By the strong nuclear force, and they're all pushed apart by electrical forces, electrical repulsion. But the neutrons kind of are hanging out along with the protons. And I think they're usually maybe one third more neutrons than there are protons in sort of the heavier elements. In their most stable form, different isotopes correspond to different numbers of neutrons. With a fixed number of protons. The number of protons determines which element one's talking about. The number of neutrons determine which isotope of the element one's talking about. But you can ask questions about, just like we talked about the way that electrons are arranged in atoms. We can talk about how are the protons and neutrons arranged in a nucleus. And again, there's a complicated story of shells and there's this idea of when you get certain nuclei have so called magic numbers and those correspond to cases in which the nucleons, the neutrons and protons can be arranged in these sort of closed shell type configurations. And those nuclei have special properties. They have. Well, they're sort of spherical symmetric, they're sort of known to be spherically symmetric. There are other nuclei which can be kind of elongated and which effectively are spinning around as a result of that. And that leads to all sorts of different properties. And you can make sort of a periodic table like thing for nuclei which determines their properties based on very much the same kind of shell counting type of, type of approach. Okay. Ah, well, Rudo is asking is periodic table just the table for the current state? Talking about the big bang and other things. All right, let's talk briefly about that. So there are, well, give or take, there are about 92 stable elements, actually a little bit less than that. So remember the elements going hydrogen, helium, lithium, beryllium, boron, et cetera, progressively more protons for each element. There may be many different isotopes, many different numbers of neutrons that can exist in the nucleus. But if you have too many neutrons or too few neutrons, the nucleus will be unstable, it'll fall apart in some way. If you have too many neutrons, the neutrons tend to decay on their own. If you have too many protons, you'll tend to have sort of the inverse of that reaction. And so, for example, in the case of hydrogen, there's protium, the isotope of hydrogen with just a single proton. There's deuterium, which is the isotope of hydrogen with a proton and a neutron. Then there's tritium, a proton and two neutrons. Tritium is unstable with a half life of, I don't know, 17 years or something. On average. On average there'll be half of all tritium atoms if you. Tritium nuclei, if you have them, will have decayed away and turned into, I think decays to deuterium and electrons. Yeah, the, the. No, no, it decays. What does it decay to. See? Electron. I'm not sure. Okay. In any case, it decays. One of the neutrons turns into a proton, an electron and an anti neutrino. But that leaves it with two protons and a neutron and that's not stable. So I don't know quite what happens next. The. Oh yes, it Is. I'm sorry, that is, it's helium 3. That's. That's correct. That's what it decays to. And in any case, the thing that when you put in more, you know, to, to have a given number of protons, a given element, there's the question of are there a number of neutrons that you can put in so that you will get a stable isotope of that element? And for the first 42 elements, there's always at least one stable isotope. There's always at least one number of neutrons so that the nucleus won't fall apart. Sometimes there are several, sometimes There will be 10 or more, but there's always at least one. Until you get to element 43, technetium. Technetium is the first element where there just isn't any stable isotope. There's no way to get a nucleus with a 43 protons and any number of neutrons that doesn't unstable and decay radioactively. So 43, there's a sort of hole in the periodic table for an unstable element. There's another one at 60 promethium and then the next. And that's kind of a weird thing that there are these sort of low lying elements that have fairly small numbers of protons that are unstable. Well then you keep going a long way and you get up to uranium, which is the next one, 92, which is also unstable, although it has isotopes that are stable for billions of years. So it is unstable, but not very unstable. And then everything beyond that, so far as we know, is unstable. Nobody's ever proved that there's no heavier elements that could be stable. People believe nowadays that there aren't any stable heavier elements. But nobody has proved that there isn't an element with 200 protons, for example, and 600 neutrons or something that suddenly will become stable. It's not known that that's not the case. It's believed that that's not the case. And there's pretty good evidence that that isn't the case because one's looked up to elements with 120, 125 protons and things and those elements get progressively more and more unstable. But it always used to be believed, 50 years ago it was believed that there might be an island of stability, a place where you would again get stable, stable nuclei. Hasn't been found, probably doesn't exist. So that means that the elements, as you go to larger numbers of protons, you're always just getting things that are very unstable. So the question then is, well, where do Those come from. Well, the answer is you have to make them by colliding together other pieces of other nuclei and so on to get sort of the extra protons to stick onto a nucleus for at least a little while until the thing blows up and, and decays again. But the elements that we have. So all the elements that we have were ultimately made in the previous history of the universe, in the Big Bang, at the beginning of the universe. Well, what happened was the universe was originally extremely hot, where none of these things like nuclei and even protons just there was so much energy, so much sort of heat, that any one of those kinds of objects would just get, would get, you know, smashed apart. And so all that there was at the very, very beginning of the universe was whatever the most elementary possible particles are. Actually, in our model of physics, it's a little bit more elaborate than that. The beginning of the universe not only were kind of all the particles broken up, but so was space. And in fact, space, instead of behaving as three dimensionally as it does now in our models of physics, space had. Space was infinite dimensional, we think, and space itself was very kind of bubbling around and not stable in any way. As it sort of cooled down, these little sort of lumps of features of space that turn into particles could be identified, and then it kind of went on from there. And so before, about one microsecond after the beginning of the universe, millionth of a second after the beginning of the universe, there was probably at most you would be able to identify some electrons, some quarks, and they're all sort of bouncing around. Then as the universe sort of got a little bit colder, the quarks would kind of form into protons, for example. The electrons are still bubbling around on their own. At about one second after the beginning of the universe was the possibility of nuclei forming. That was the time at which the temperature of the universe was low enough that if some protons and neutrons stuck together, they wouldn't be blown apart by heat associated with the heat of the universe, so to speak. The next big event in the history of the universe is that 100,000 years after the beginning of the universe, which is what's called recombination, which is where the amount of heat has gone down, the temperature has gone down to the point where the electrons and protons can form ordinary atoms, where it isn't the case that the things are being bashed around so much. An electron can't sort of attach itself around a proton to make hydrogen, for example, and that Instead, before that, before 100,000 years after the beginning of the universe, it would always sort of the electrons and protons would always be bashed around to the point where they couldn't form neutral atoms. That point 100,000 years after the beginning of the universe is an important point. It's the time of so called recombination. Shouldn't really be called recombination because these things were combining for the first time in the history of our universe. But it means combining the protons and electrons into neutral hydrogen atoms. And the reason that's important is because before that time, the universe was not transparent to light. It's more like it was like a plasma like fire where you kind of can't see through it. But 100,000 years after the beginning of the universe, the universe started to be transparent. And that means that any light that was produced at that time can just travel through the universe since that time without, unless it hits something, can just travel without being stopped. And that's important because the cosmic microwave background is that light in any direction in the sky, there is a small, there's a, at a very, it's effectively a low temperature because of the expansion of the universe. There is one is seeing this sort of primeval fireball, this, this original, the, the original kind of photons that were produced before the universe became transparent. So it's kind of the, the place where it became transparent was 100,000 years after the beginning. We get to see those photons. Okay, so in terms of nuclei, one second after the beginning of the universe, nuclei started to form. And the question is, which nuclei formed? Was it just hydrogen or was there more? Well, it's a complicated calculation. It was done in the 1970s, 1980s, so called cosmic nucleosynthesis, the formation of nuclei. And it was, that was what happened is, and it was a difficult calculation. And actually I, well, it was a little bit involved in some pieces of that. But the, the calculation implied that about, about a quarter of all nuclei that were made at the very beginning of the universe were helium nuclei and the rest were hydrogen nuclei. And there was just a tiny number of deuterium nuclei. So helium nucleus is two protons, two neutrons, usually the hydrogen nucleus, just a single proton, deuterium nucleus, a proton and neutron. So there's a whole zoo of different kinds of nuclei that were made in the Big Bang. But, and their ratios, one can compute based on working out kind of the rate of reactions between different nuclei and things like this. But there was almost nothing. If you go down to lithium or other heavier elements. Almost none of that was made in the Big Bang. According to the calculations, one can make about sort of the density of material and so on and how often nuclei would run into each other, all those kinds of things. Almost nothing beyond, well, maybe lithium was made in the Big Bang. So where did the heavy elements come from? Well, the answer is that they basically come from. Well, they mostly come from supernovas. They come from exploding stars where stars got sort of too big, they collapse, they, they kind of use up that the pressure that comes from all the nuclear reactions, like the sun for example, where there are hydrogen, hydrogen fusion is occurring, that all the hydrogen is kind of used up. And at that point there's no longer as much energy that can be produced in the star. It doesn't have as much pressure pushing it out. There's this sort of catastrophic moment when the star will collapse. And it starts at that point, it starts producing lots of much heavier nuclei confused together. And then it produces the whole spectrum of nuclei going all the way up to the very unstable ones beyond uranium and things like this. And that's where, for example, all the gold that we have on the Earth came from. Well, actually there's two mechanisms, but mostly it came from supernovas one way or another. Mostly came from this rapid process of the sort of the last few seconds of the collapsing star causing these nuclear reactions to occur that produce heavy elements. So the very early, in the very early universe, even probably the galaxies that the Webb Space Telescope can see, the first galaxies it can see, probably don't have much gold, for example, in them. It's only the later populations of stars and galaxies that have that in them. And the. So you know, because some stars, our sun will live 10 billion years. It's been around for about 5 billion so far. But there are other stars that live for only a few million years and produce supernovas quite rapidly. Larger stars, for example, often do that. And those stars as a galaxy forms, they're these kind of areas where lots of sort of short lived stars exist. They produce supernovas that produces material that can be then used to form other stars. And that's how the heavy elements are produced. Okay, so that's on the coming in, that's how elements get produced. Now on the kind of going out, what will happen sufficiently long in the future? Well, one question is, is a hydrogen atom just hanging out? Is it stable? Is it just going to stay that way forever? Let's ignore the question of whether giant black holes form like exist at the center of our galaxy and things like that, and just become essentially vacuum cleaners that vacuum up all the in the universe. That's a separate issue. Let's just talk about a solitary hydrogen atom. So in interstellar, intergalactic space, there's roughly one hydrogen atom per cubic meter. So there's not a lot there, but there's something there. But it's just a hydrogen atom. It's just hanging out, waiting for the rest of the universe to occur, so to speak. One question is, does it get to hang out forever or does it eventually decay in some way? So nobody knows. And there was a period of time about 40 years ago when people were pretty sure the proton was unstable. So we're pretty sure that a proton would eventually decay into a positron, an anti electron, together with neutrino and maybe photons and so on. And so people did these experiments looking for proton decay. You just have a big tank of anything, you know, fluid, and you wait and you see whether. Just all nuclei eventually self destruct, including hydrogen nuclei. And well, no such thing was found. It's hard to do that experiment because you have to have it in a deep mine, for example, where you're shielding it from the cosmic rays that hit the earth and so on, and cause sort of nuclear reactions to happen. But so people thought that the proton might have a lifetime around 10 to the 30th years. So let's see, a trillion, trillion, trillion, well roughly that years. That was a calculation done on the basis of so called grand unified gauge theories that the proton might have a lifetime of that order wasn't found. It set off a big sort of big soul searching and maybe panic in particle physics that it wasn't found because it seemed like all the sort of theory was aligning that that should be found, but it wasn't. So we don't know if protons are unstable or not. Protons could be unstable with a lifetime of 10th or 40th years or something. We don't know. The theory does still hang out there that yes, protons should eventually be unstable. There are several mechanisms that should lead to that instability, but it might be, but it hasn't ever been observed. So we don't know for sure. So then if you ask the question what's the universe going to be like? The biggest effect of the universe on very large times is gravitational, probably not the decaying of the protons, if the protons even do decay. It's much more that the different parts of the universe into black holes and black holes and black holes kind of basically time stops. The singularity of a black hole and you end up with the situation where that's what it looks like, black hole. But it's actually more complicated yet than that because black holes as a result of quantum mechanics eventually evaporate away. Although if it's a big black hole, it takes an absurdly long time for that to happen. But eventually they evaporate away and, and they kind of in a sense disgorge a ground up version of their contents. They produce lots of particles. So the picture of what the extremely long time limit of the universe looks like is a quite complicated question. And it has to do with exactly what the rate of expansion of the universe is. It has to do with all of these effects I'm talking about with black holes. It has to do with. Well, a thing people talked about a lot even 150 years ago was the so called heat death of the universe. Where kind of what's happened is everything is just a gas and all the molecules are just bouncing around quotes randomly and all the interesting stuff in the universe is over. That was a belief about how the universe would end up. That belief is surely not really right. I mean, gravitational effects and black holes and things kind of blow up that, that picture. And the second thing that blows up that picture is yes, it is true that the molecules in a gas bounce around in a way that for most practical purposes for us look random, but they're not really random. They are determined by the past history of the gas. And so the far future of our universe, which may have a bunch of molecules bouncing around that far future, is determined by our current existence in the universe. And in that far future, some encoded version of everything that we are now will exist in those molecules bouncing around. So while we, with our current kind of sensory apparatus, where all we notice is kind of big chunks of molecules and so on, with our current sensory apparatus we'll say, oh, it's all just random. In the far, far, far distant future to an entity with different sensory apparatus that, for example, can notice where every individual molecule goes. It may be, oh no, no, it's not random at all. It's this elaborate dance of molecules that is a representation of the future of all of this fancy stuff those, those people back in, you know, 2023 or something. We're doing. All right. There's a question here from Prab. How are we, how certain are we that the Big Bang actually happened? I think we're pretty certain that the Big Bang happened. We're pretty Certain that the universe was very small at the beginning. We're pretty certain back to the time of recombination, 100,000 years after the beginning, that at that time the universe was hot. And also, we know from kind of seeing, if we look in different directions in the sky, we're essentially seeing different parts. It kind of gets inverted what we see on the sky and what sort of this, this ball was like kind of inverted. But we're basically seeing the temperature, the effective temperature of different parts of that, of that kind of original ball of material. It's a little bit difficult to say ball of material because it's a ball of material that is the whole universe. It's not expanding into something empty. It is the universe all sort of in that ball. But in any case, we can look at the cosmic microwave background and we can see just what is the temperature in different directions. And we can see there's about a thousandth of a degree difference in different places of what the temperature is. It makes a very elaborate pattern on the sky. And you know what those fluctuations are like? Well, they're partly explained. They're partly. And those are explained by features of kind of what happens in the gravitational processes in the very early universe. It could be that hiding in those wiggles in the cosmic microwave background is evidence for something associated with our recent theory of physics. Our recent theory of physics talks about the fact that the dimensionality of the universe starts infinite dimensional, gradually sort of cools down to three dimensional. But there will probably be dimension fluctuations that get left over where there are pieces of the universe that behave as if they're 3.01 dimensional or something. And that will be rather similar probably to the effect of gravity in those areas. We don't know exactly what those effects will be. It really has to still be worked out, but possibly hiding in the details of the cosmic microwave background are features, fluctuations in the temperature of the microwave background that could be a sign of dimension fluctuations and could show us that things about how this theory of ours works, which would be pretty exciting. But we have a pretty good understanding of sort of why the cosmic microwave background is something at 100,000 years, we pretty much seem to have a good understanding of that. Now. There were some mysteries earlier on. Like, for example, one of the things about the universe is that in a sense, we look in one direction in the universe, we see a bunch of galaxies, we see other things. We look in the other direction of the universe, we see something that's kind of comparable to what we see in the first direction. And if we look at the cosmic microwave background, yeah, it might differ by a thousandth of a degree out of 2.7 degrees. 2.7. It's the, the. The effective temperature now is 2.7 kelvins, 2.7 degrees above absolute zero. Originally it was 6,000 degrees, roughly 6,000, about 4,000 somewhere in that, a few thousand degrees at the time of recombination. But the expansion of the universe has caused the effective temperature to be much lower now. So the. But in any case, you know, what we see roughly is that the effective temperature looking in one direction of the universe is about the same within a thousandth of a degree, let's say, with the effective temperature looking the other direction. But yet that might seem very mysterious because how could it be the case that those looking in photons coming from those two directions, those photons have never had a chance to interact before. Those photons coming from those two different interactions, the first time they're at the same place is when they hit our eyes, so to speak. They never interacted before. At least that's the most obvious picture. And so there's sort of this question of how come the universe knows to be homogeneous uniform, given that it didn't get to interact. If you have a box of gas, for example, then if you have more gas over on one side of the box than over on the other side of the box, it'll eventually equilibrate and get to be roughly equal densities of the gas in the box. But it'll do that because molecules from one side bounce over to the other side. They bounce back the whole box. The molecules are able to travel from one side to the other and all interact. But if you're dealing with the early universe, it can be the case that there's a part of it that just never had a chance to interact with another part of the universe, at least if there wasn't something sort of funky going on. Well, the question of whether there could be some mechanism for interaction, one of the popular ideas is this idea of inflation. Actually, that idea, I think the very first place that. Well, maybe it appeared very early, at least in a footnote to a paper I wrote with another person back in 1979 or so. But for various reasons, we didn't believe that the amount of inflation would be enough to have a. We knew that it would have an interesting effect on the homogeneity of the universe, but we didn't think that the effect. It requires kind of super cooling the universe to the point where there are Things that should have happened. It's kind of like if you have some water and you cool it down below zero degrees centigrade and you keep wiggling the water around, maybe, or you keep. No, actually you keep the water really, really still. You might not form ice, but as soon as there's a little nucleus of ice that forms, kaboom. The whole volume of water will turn to ice. But there is an ability to super cool things as well as to superheat things. You can have water that is above its boiling point and until it nucleates, until you get the sort of bubble, you don't start to get steam formed. So you can have this super cooling process where you have taken something like water, cooled it below its freezing point, it doesn't start to actually freeze until some little sort of freezing nucleus, which could be a grain of dust, could be all sorts of things shows up. So the question was, could the universe be super cooled? And if it could be, and there was no inhomogeneity, gravitational inhomogeneity, for example, in the universe, you could potentially super cool it, but you have to super cool it over a huge range of temperatures. And if you did that, then the properties of the universe would be very different. The universe would behave as if it has, oh, weird negative mass stuff in it and all kinds of weird stuff. And the universe would have a period of very, very rapid expansion. And that would explain this whole question about why different parts of the universe can kind of see each other, because they were sort of in contact back before this exponential expansion and so on. This is a theory that I must say has gotten very ornate over the years. And people have had to add all kinds of different features and extra particles and all sorts of things that haven't been seen. And they're slow roll inflation and inflatons and just a bunch of stuff. And usually when you look at scientific theories, one of the things is you've got a certain set of things to explain and you've got a certain set of things you put into the theory, you win. When the number of things you put into the theory is really small compared to the number of things the theory explains. What's happened with inflation, I'm afraid, is not really that it's gone the other way. It's been in order to explain what you see, you have to pour in all of this weird things. You keep on patching things and so on. It doesn't, to me, it doesn't have the right vibe to be a correct theory. So in fact in our physics project, one of the nice things that comes out is that there is a theory of how homogeneity happens in the universe. It happens because the Universe was originally infinite dimensional. And that means you can think about the Universe as a big sort of graph. It has a bunch of points in space, and these points, they're not actually defined by a position in space. They're just defined by how they're connected to other points. So you form this big graph, and that graph in effect effectively defines the structure of space. So if the graph happened to connect everything to four nearest neighbors and each one of those to four nearest neighbors and so on in a grid, it will be sort of an effectively two dimensional space. If at the beginning every node was basically connected to every other node, that's effectively an infinite dimensional space. As you get fewer nodes connected to a given node, you get basically lower dimensional space. At the beginning, you can have infinite dimensional space. And at that point, sort of every, every node affects every other node. And so that means that sort of explains why one side of the universe, what's now one side of the Universe, was in that infinite dimensional state, something that was infinitely close to every other part of the universe. And that means that this fact that the different features of the universe are comparable on all sort of sides is very unsurprising in that picture, because the whole universe was just connected, you know, one step away from each other in kind of a moment, in one moment of time, so to speak. An effect could, could move from any part of the universe to any other part of the universe back then. But as the dimension of the universe decreased, that became more and more difficult to be the case to the point where now there can be that one photon. That was all these two photons which were emitted from sort of different ends of the universe, and they only meet now, but they will have met their precursors, which won't have been photons yet, will have met before when the universe was infinite dimensional, before the universe kind of cooled down to be, to be finite dimensional. So, but we don't know that's what happened. I strongly think that's what happened. But in terms of the sort of basic picture of the universe was hot and small, yes, that really is pretty established at this point. The question of sort of what happens in the very, very early parts of the universe, I would say back to one second, maybe even a microsecond, we have pretty good knowledge of what was happening in the universe. The success of calculations of the different abundances of different kinds of isotopes are encouraging. Another phenomenon that was happening in the early universe I worked on quite a bit many, many years ago. Is that why there's more matter than antimatter in the universe? So just as there are electrons, they're also anti electrons, positrons. Just as there are protons, there are antiprotons. An antiproton has the same mass as a proton, but it has the opposite charge, opposite electric charge. And that's the general principle of antiparticles. Every electric charge like thing they have is negative for the antiparticle. So, for example, when two antiparticles meet, they electron and positron, they will be attracted to each other. Actually, there's even a weird kind of atom called positronium in which an electron is kind of going around a positron as opposed to an electron. Positronium is much bigger than, well, bigger than the hydrogen atomic. All right. Yeah, that's right. The, in any case, the, the, the thing that. So in the very, very early universe, There should have been an equal amount of matter and antimatter. There isn't. Now, back even 40 years ago, we didn't know whether there were anti stars or anti. Galaxies could have been the case that, you know, the Andromeda galaxy could have been made of antimatter. The nearest big spiral galaxy to ours could have been made of antimatter. We didn't know. It could have been the case that half the galaxies, just like, you know, half the galaxies rotate sort of clockwise in some sense, Half anti clockwise in some sense. It could have been the case that they. That half the galaxies were matter and half were antimatter. It seems not to be the case. It seems to be the case that matter and antimatter. There is an excess of matter over antimatter by about 1 part in 100 million. So there's about 1 part in 100 million more matter than antimatter in the universe at the point where things like nuclei and then galaxies and all that kind of thing formed. Why is that? Well, nobody knows for sure, but there's a model which again, I actually worked on back in 1979, 1980 for why this happens. And it's a pretty ornate story that is very connected to proton decay. And it is the things that would make that happen are the same as the things that would make protons decay. And it's a little bit embarrassing that proton decay hasn't been observed for some of these theories of how matter antimatter asymmetry occurs. But it's A slightly long story of how you get. Well, not so bad. It's okay. So matter and antimatter, the, the properties of, of an antiparticle, the charge is negated, the mass is the same. One of the things was discovered, oh, last few decades is that antimatter falls under gravity. It doesn't have negative mass, it has positive mass. It falls just the same way as matter falls and so on. So it works that way. Okay. Next fact about antimatter is that if you have an unstable particle and you have an anti version of that particle, the total lifetime of the unstable particle is the same as the total lifetime of its antiparticle. However, in a rather subtle effect, there can be a difference. If there are two different things that the particle can decay to, there can be a difference in the decay rate to one of those things. The other thing for the particle versus the antiparticle. An example where this is known is the K0 particle. It's a particle with a mass of about half the mass of a proton. It decays in about 10 to the minus 8 seconds. Well, actually it's a little bit complicated because there are two versions of it. One decays in 10 to the minus 8 seconds. One decays in 10 tothe minus 10 seconds. And it's a complicated story how those things decay. And one feature they have is if you were to look at how much of the short decaying versus the long decaying one of the K0 exists and you just go forwards in time from a given point. You say how much K0 are short, how much K0 are long. There'll be a certain amount of each one and there'll be some oscillations and so on. And you measure that and it's a certain form going forwards in time. Weird fact. If you were to reverse time, go backwards, those wiggles work differently. It's the example of so called time reversal violation. It's a small effect, about one part in a thousand in the decay of the K0 meson. And it's weird effect. It doesn't affect the full decay rate of the K0, but it does affect whether the K0 decays more into two pions or more into three pions. And that's sort of different if you were going forward in time than if you were going backward in time. That's a different effect. If you're thinking about the second order of thermodynamics and entropy and things is a slightly different effect. It doesn't really engage with those kinds of questions. This Is a different. This is a so called, well, time reversal violation. Also equivalent to a thing called CP violation. Oh boy. Getting into complicated things here. One general feature of physics is that if you take a physical process and you make a movie of it and it's doing what it does as a function of time, and then you reverse the. You know, you run the movie in reverse. The question is, could that reverse thing happen equally well? And the answer is this time reversal violation phenomenon means that there's a small effect whereby it doesn't happen equally well. But if you not only reverse the time, but also look at antiparticles and also invert space and everything that was spinning one way is now spinning the other way. Sorry, everything that was going one way is sort of going the other way. Spin works differently. And you do simultaneously charge conjugation, I.e. particles to antiparticles, parity, inversion, that's invert space. And time reversal, that's reverse the direction of time. If you do all three of those things simultaneously, that's what's called in particle physics, for example, CPT transformation, charge conjugation, parity, time reversal transformation. According to current theories of quantum field theory, Every process is unchanged by CPT transformation. So time reversal on its own. You can have something which looks different for time reversal. And then it will also look different for CP transformations. But if you combine CP&T, it will always look the same. Footnote to this. Nobody knows whether gravity satisfies CPT invariance. And it probably doesn't. But that's a footnote to this whole story. But the question of whether it does or doesn't is actually pretty subtle. Because of the way that one even sets up the notion of what time is in gravitational fields and so on. In any case, let's see, what I was explaining was how one gets this effect of how one gets antimatter asymmetry. And basically the answer that we came up with many years ago is that there have to be these particles that are very massive compared to protons. We've never seen them. We haven't been able to produce them in particle accelerators yet. And those particles decay in a way that violates cp. And some of the decay modes, some of the things they decay into, the amount of particles versus antiparticles of some part of what they decay into is different. That interacting with the way the universe expands Leads to the small asymmetry of matter over antimatter. Subtle effect. Subtle effect. Important for us because that's why we're here. If it was the case that matter and antimatter were in exactly equal quantities in the universe, probably all the matter and antimatter would have annihilated away and we'd just get left with a bunch of photons and electrons and positrons and we wouldn't have had heavier things and the atoms that we're used to and all those kinds of things. It's not completely certain that's the case. It could be true that you could have sort of a region of the universe that was matter and it was a region of the universe that was antimatter. And right at the boundary between them there could be annihilation happening and that could produce radiation pressure that holds the other parts apart. It's not completely clear whether that would work, but it doesn't happen in our universe so far as we can tell. All right, just maybe one more thing and then I probably to should wrap up soon. Let's see. Brady is asking what do you make of the very early galaxies seen by the jwt, the space telescope, which seemed to too large to exist so early? Yeah, I mean, I think there was a claim that there were some galaxies that existed only millions of years after the beginning of the universe. And I think that claim didn't survive. I think that will be a bit, a bit early. I mean, people kind of believe that there was a period when there wasn't a lot of light being produced in the universe because the original heat of the Big Bang had kind of cooled down to the point where it wasn't generating visible light. And yet there'd been no gravitational clumping that led to things like stars which could start to have fusion reactions which would lead to visible light. So there was a sort of period where people have assumed that there's kind of a dark age where there isn't visible light produced in the history of the early history of the universe. They're, you know, quite. Where the first galaxies will show up is not known yet. But there were some claims of very early galaxies. It's kind of tricky to know, you know, how do you know where when a galaxy was originated? You know that because galaxies, because of the expansion of the universe, galaxies that were originated early are effectively their effective looked at by us sort of this late relative to when they existed in the history of the universe. The relative speed of us relative to that galaxy is very close to the speed of light and we are effectively seeing a very red shifted a very kind of like the way that you, you know, when you, when a siren goes past you and you hear it lower when it's going away from you. That same effect happens with frequency of light when things are going away from you close to the speed of light. And that's what happens for distant galaxies. You kind of know how far away it is by knowing things about the expansion rate of the universe and how low the frequency of light has got. So that's sort of the big measure is the so called redshift. It's usually called Z. And you know Z of 5. Well, people have seen galaxies out there, but you know, Z of, what is it Z of? Is it Z of 3,000, is that right? I think that's what it is relative to recombination. Or is it 2500? I've forgotten. Maybe it's 2500. So, you know, galaxies have been known for a while out to about Z of 5. There are things at least very galaxies that produce very intense radiation. But you know, getting to the very beginning, to the point of recombination, 100,000 years after the beginning of the universe, that would be much, much further out. And there's a question of sort of how far out can you observe? Let's see, It says the question here, Is it possible the expansion of space due to dark energy could eventually be fast enough that even atoms and nuclei come apart? Yes, I mean, in. There are certainly places where the structure of space time is so wild that every material object is pulled apart. That happens near a space time singularity that exists at the center of a black hole, for example. It's kind of a. It's very tricky business to get in naked singularity, a place where there's a singularity in space time, but it isn't surrounded by an event horizon that has the property that everything that falls into that event horizon can never signal out. But by, in a kind of subtle way, it's possible to get, well, sort of a temporary, sort of roughly place where there is a singularity in space time. What does that mean? It means that you can observe there's a singularity at the center of a black hole, but it's hidden behind an event horizon. What happens at that singularity? One thing that happens is that the curvature of space becomes infinite. And so what does curvature of space mean? Well, think about if you have two parallel lines and they're going along, they're next to each other, they stay parallel, they never meet. But if you draw those parallel lines on a curved surface, those parallel lines will eventually cross. And the fact that those parallel lines sort of approach each other is the same effect, according to general relativity is the same effect as the deflection of a particle's motion by gravity. So in other words, when there is a, the deflection by gravity is the same phenomenon as space not being flat, as space being curved. And so when one says, well, the curvature of space is getting very, very big, it's equivalent to saying there's a really big amount of gravity there. And so what happens at a space time singularity is that the curvature of space becomes infinite. There's effectively an infinite amount of gravity there. And that means that any material object, any, including an atom, its pieces will be essentially torn apart because the structure of space in which they exist is being torn apart. So yes, it is true that you can get from a gravitational effect, from gravitational singularity, you can tear apart you, you kind of the, the, the, it's, you know, you might say, well, there's a, there's a proton here, there's an electron here, but no, well, actually, where's here? Well, here is getting torn apart because the very structure of space is getting torn apart. And that's actually a clearer thing to see in our models because you actually see the structure of the graph that represents the structure of space, which is normally kind of bubbling around and rearranging itself and so on. You can actually get pieces of that graph become disconnected. And that's the sort of extreme version of how you can have something where sort of parts of different. So if one, if the electron is on one side of that disconnection, the proton is on the other side, then they are very much torn apart. So, Oh, let's see, There's a question here. How is the temperature of the cosmic microwave background measured? Actually, several friends of mine have been involved in doing those measurements. The. Okay, so the frequencies of light, frequencies of electromagnetic radiation that correspond to the cosmic microwave background are. First point is, if you heat something up, it'll eventually glow red hot, then it'll glow white hot, then it'll glow blue hot. What's happening there is, there's a relationship between the temperature and the typical frequency of photons, which determines their color produced by a. Produced by heating something up. So if you heat something up really, really hot, it'll produce X rays and all kinds of crazy electromagnetic radiation. If you heat something up just a tiny, tiny bit, it'll produce infrared, then it'll produce microwaves, and it'll produce other longer frequency radio waves and so on. Well, the cosmic microwave background. So for example, an incandescent bulb like the sun, it's heated up to about 6,000 degrees. At 6,000 degrees, you get roughly white light. You get roughly equal amounts of the different colors of light. So the cosmic micro background, it's effectively heated up to around 2.7 degrees Kelvin, 2.7 Kelvins, 2.7 degrees above absolute zero. And that's so, that's. So it produces a certain frequency of electromagnetic radiation that is in the microwave range. It's radio frequency radiation. The cosmic microwave background was discovered around 1964, if I remember correctly, when people at Bell Labs were trying to set up kind of microwave communications with satellites. And so they had a, you know, they had this whole assembly and they were, you know, they were trying to transmit signals to satellites. They were very early satellites. Mostly I think just these Myar balloons that would reflect radio waves. And they noticed that. They noticed, excuse me. They noticed that try as they might, they couldn't get zero noise in their microwave signal. They would always get some relic, some temperature, some effective temperature of random microwaves that were entering their devices. And actually they rather quickly figured out that that might be the relic radiation from the Big bang. So that was how it was discovered. In today's world, there are some exotic ways that the temperatures get measured to do it accurately to within a thousandth of a degree. There's a detector at the South Pole that does that. It's important that you don't have a lot of temperature around that can sort of produce. You're measuring it by measuring radio, radio waves. But you need your detector to be very cold, and you need everything to be very cold. It's good to be at the South Pole. If you're doing that, Even better is to be in space. There's a satellite called the Planck satellite that is at the, the Lagrange point in the Earth Moon sun system. So that's the place where it's. Let's see which Lagrange point is at. I think it's at the one that is kind of the one that's away from the Earth in an equilateral triangle with the sun. And it's sensitively capable of measuring the cosmic microwave background. And actually a friend of mine built some of the equipment for that. And it's one of these things where if you have your equipment at the Lagrange point in the Earth Moon sun system, unless it becomes a tourist attraction, it's just hanging out there for billions of years. And so if you kind of sign your little piece of apparatus there, it's kind of your signature is out there for billions of years, which is kind of fun. All right. I think think I probably have to wrap up here, although there are bunch of interesting questions about. Yeah, I don't think I can address these right now. Well, all right. We had a cosmology and well, we had a chemistry and cosmology day today. I never know what's going to come up here. It's always, always fun for me and hope you all find it interesting. We've talked about very different kinds of things in different times here. I've kind of had the idea that I might try and make these a little bit more definite one topic kinds of things because it's easier if people want to find these sometime in the future to find stuff about a particular topic might be easier than. But we'll see. Well, thanks, thanks for joining me and see you again another time. Bye for now.