[SOUND] Welcome back to my course on From the Big Bang to Dark Energy. And as I emphasized in the previous lecture, we have learnt tremendous amount of information about the universe over the past century or so. And the we'd like to address many basic questions about the universe, just like a little kid watching up the sky, being awed and impressed by the beauty of the universe. So naturally we all like to ask questions like how did the universe begin? What is its fate? What is it made of? What are its fundamental laws? And, why do we exist? In this universe how do we come to exist? And all of these questions are now coming into the realm of actual scientific research. So we asked the questions about how things are around us. there's just the fact that there's day and night, four seasons, and motion of planets and so on. Eventually, come all the way back to the beginning of the universe, when the universe was only 380,000 years old. Was a really baby universe that let so much light out, we can still get to observe that hot universe. Still today. But we would like to even move beyond that. So when we ask the question, how do we come to exist? Of course we need to understand where our material came from. We are made of atoms. So where did the atoms come from? At the very beginning of the universe even atoms didn't exist. It was such a hot and dense soup of elementary particles. Atoms actually did not exist. So we need to ask the question about the birth of chemical elements. Where did the elements come from? Or so it turns out, that this question is related to something you may have heard about fairly recently. Named the Higgs boson that have been discovered last July, at an experiment called LHC, at the Swiss French border. So we need to ask the questions about how the atomic nuclei had been formed and it has happened when the universe was like three minutes old. And how the Higgs boson came to be and atoms were born That had to do with the time of the universe when it was only a trillionth of a second old. So we are going back to, even much closer, to the beginning of the very big bang itself by studying the origin of the chemical elements and atoms. So that will be the subject today. So, the second lecture is Birth of elements, and Higgs boson. So the first half is about the birth of element. So this is a picture of cranky old TV, and many of you may have not even seen a TV like this in your life. But whatever the object may be, if you just, you know, slice it up into smaller pieces, eventually you arrive at atoms. Everything around us is made of atoms, and you know that. And atoms are made of electrons and nuclei. So it's sort of like a solar system where all the planets revolve around the sun. Electrons in atoms revolve around the nucleus. So that's the structure of atoms as you already know. And atomic nuclei can be further divided up into smaller pieces. Namely, neutrons, which don't have electric charges and proton, which has the positive electric charge. And if you look even closer, it turns out the neutrons and protons are not elementary objects either, they are made out of even smaller pieces called quarks. Both neutron and proton have three quarks inside and we'll briefly talk about that later, but you don't have to worry about it too much at this moment. And the, the point about the chemical elements when we talk about the origin, is that you know what chemical element you are talking about once you know the number of protons inside the atomic nucleus. So you glue neutrons protons together to build up their atomic nuclei And the number of protons is the key to determine the nature of that atomic element. So that leads us to the familiar table which I am sure you have seen hung on a wall in your science classrooms. That's the periodic table of chemical elements. And [COUGH] the thing about this table of elements is that there are so many elements out there, more than 100 of them, and our, you know, all of the surroundings are made up of about 90 of those, and you need all of these things to explain all of the, the, the, objects we see around us today. but it turns out at the very beginning of the universe, at the big bang They were only hydrogen and helium. Hydrogen is here, whose nucleus is composed of just one proton and nothing else. And helium, which is made of two protons and two neutrons. And they are the only chemical elements that existed right after the big bang. But we, our body, has a lot of other elements in it. We need carbon, nitrogen, oxygen. For example, even all the way up to iron. We actually need all of these elements to make up our body. So, that's the natural question here. How were all these elements born, when the big bang itself produced only hydrogen And helium. So that's the question to you. So how were the bigger elements formed out of the smaller elements?
