WATCH: What Is Big History?

DAVID CHRISTIAN: Earth is the place that we humans call home. It's a very beautiful place with staggering variety: gorgeous landscapes from mountains to rivers to oceans; a staggering variety of different species from redwoods to swallows to beavers to spiders; and, of course, seven billion other humans like you and me-- perhaps the weirdest species of all. And then look above us. Look at the sun. It's the battery of life here on Earth. But our sun, it's just one of perhaps a hundred billion stars in our galaxy, the Milky Way. And the Milky Way is perhaps just one of a hundred billion, maybe 200 billion galaxies in the Universe. So, how did things get to be the way they are? How was the Universe created? Why does it work the way it does? Why are stars so big? Why are you and I so small? Why do we find ourselves in this particular part of the Universe, on this tiny planet buzzing with life? Why are humans so powerful? What does it mean to be "human"? These are wonderful questions and they've been asked by people in all societies. And they have also been asked by a lot of people with great expertise: geologists ask them; biologists ask them; astronomers, physicists, historians, anthropologists. What we want to do in this course is to take the expert answers and try to blend them into a single, coherent story that will explain how everything came to be the way it is, how we fit in, and where, perhaps, everything is going. Take a look at this timeline. It shows my own journey through time. And what I've done is I've placed on it events that seem important in my own life. We can think of them if you like as thresholds, crucial turning points in my life. For example, at the age of three months I traveled to Nigeria. I went to Canada, where I met my wife. I went to university. I trained as a Russian historian and I got my first job in Australia. All those things were important. But now, I carry three passports because I've traveled so much. And the trouble is, I'm not really sure, in a sense, what country I belong to or, in a sense, who I am. I was never really content, therefore, to understand just the history of one country, or even to teach the history of one country Take Russia, in my case. What I wanted to know about was the history of humanity as a whole. Now, if you think about it, that question forced me back. If you want to know about humanity, you have to ask about how humans evolved from primates. You could push that back, ask how primates evolved. Back and back and back until, eventually, you're talking about the origins of life on Earth. And once you're doing that, why not ask about the origins of the Earth and the whole Universe? Now, these questions are huge but they seemed really important to me because asking them gave me a sense of understanding what I am and what it is that I'm part of. Eventually, I realized that all human societies have asked these same questions, I think for the same reason as I asked them, but their answers were incredibly diverse. Some say that the Universe has always existed. Some say it was created very recently. Some say it was made by the gods, some say it arose out of a sort of cosmic mush. And then what the stories do is they go on to tell about the origins of the stars, of the sun and moon, of the mountains and seas, and rivers, of plants and animals, and, of course, of you and me. Big history is a modern version of all these stories. It uses the best information that we have available in our society, but of course it's not perfect. New information keeps appearing, and as a result, we have to keep adjusting the story and improving it. And there are many areas to which we don't have perfect answers-- we're really not sure. So, the story keeps changing in small ways and that, frankly, is one of the things that makes it so exciting. Now, you see my personal timeline. You can think of it as a sort of personal origin story and you can all write timelines of your own. To some of you, I guess it may seem pretty long, but if you want to look for a long timeline, think about the history of the Universe. That timeline is 13.7 billion years. Now, let's just take time out to get your mind around that figure. If you were to count numbers, each number a second, and you counted up to a million, how long would it take you? Well, the answer is it would take you about eleven and a half days. If you were to count to a billion, it would take you a thousand times as long, which is about 32 years. And if you were to count to 13.7 billion, it would take you over 400 years. Now, that's a huge story, but that's the story we're going to tell in this course. It's a fantastic story. It's got lots of twists and turns, lots of unanswered questions, lots of fascinating ideas and stories in it. One of the things we're going to really focus on is the idea of increasing complexity. Over 13.7 billion years, what we see is that gradually there appear in the Universe at "threshold" moments as we'll call them, new things, more complex things with entirely new qualities. And we'll focus on eight of these threshold moments, and they culminate in today's world. The last threshold is the creation of today's world, and that is one of the most complex things we know. So, by the end of this course, you'll have surveyed the whole history of the Universe and you'll know how you fit into it. So, let's get started.