The big question for this segment is what is big history? [MUSIC] This is a course in big history. So what is big history? Well, courses in big history tell the history of everything, literally everything in our universe, from the moment almost 14 billion years ago when our universe first appeared in the Big Bang. So this course tells the story of the universe, of stars, of planets, and of living organisms, and of us humans as well. So it links many, many different disciplines. Its approach is historical, that's why we call it big history, and that means it tells a story. The big history story tells how, in the 13.8 billion years since the universe appeared in the Big Bang, more and more complex things have appeared. Now, the early universe was fairly simple. But then slowly, less simple things appeared, from stars to planets to living organisms, bacteria at first, and then eventually to humans and to modern human societies. The global society we live in today, connected electronically through the Web, and mechanically by ships, cars, and planes, is in fact one of the most complex phenomena we know of in the entire universe. Big history is a new field for teaching and research. It's a new discipline, if you like. It's been made possible by the rapid evolution of scholarship in many different fields, and in particular, of dating systems in the last 50 years. 50 years ago, I couldn't have told you with any precision when the universe appeared or when life appeared on Earth. But since the 1950s, scientists in many different fields have developed a whole range of new techniques for dating events in the distant past without relying on writing. Many of them are based on radioactive breakdown. Now you're going to learn more about them later in the course. And these dating systems provide the timelines and the chronology that we're gonna use in this course. Big history courses are all about connecting knowledge, connecting different disciplines so that you can see the synergies between them. So this course will bring together knowledge you may have encountered in many different disciplines, from physics, to chemistry, to astronomy, to geology, to biology, and human history. And what it'll do is show you that there are many, many powerful connections between the disciplines, connections you may not have seen before. One way of thinking about big history is to think about it as a sort of origin story, a modern, science-based origin story. And that means that in a sense, big history's not really that new because we know that all human societies have told origin stories. Origin stories are stories that try to embrace almost everything. They're stories about the whole of space and the whole of time. And we know that there are origin stories embedded within all the great religious traditions. These stories really matter, and they matter because they offer sort of cosmological maps, maps of the whole of space and time. And those maps, what they do is they help us place ourselves in space and time, so they tell us what, who, and when we are. And that means they're full of meaning. After all, mapping is very close to meaning. But there's also a sense in which this origin story is different from most earlier origin stories. One reason for saying that is that it's the first global origin story. Most origin stories have their roots in particular cultural or religious traditions. This one should work as well in Beijing as in Boston, or anywhere else in the world. But this story's also scientific, that is to say, it's based on a vast amount of information, much more then any earlier origin story. And that information, and the ideas we use to hold it together, come from many, many different cultures. Well by now you may be wondering, is it really possible to tell a coherent, rigorous story that crosses all these disciplines? After all, it's not something that's normally done. Is it really possible? Well, the answer is yes, and that's the story we're gonna tell in this course. Okay, I've said we can tell a storyline, a good story that covers 13.8 billion years and the whole history of the universe. Why am I so confident? Well, we've seen one of two reasons already. First, we now have a great timeline, a chronology. We can give dates to this story, so this story has shape, and it's based on the new dating techniques developed in the last 50 years. Second, we have a great storyline. That storyline is the appearance of more and more complex things in the universe, despite the Second Law of Thermodynamics. Now let me explain that. One of the fundamental laws of physics is the Second Law of Thermodynamics, and that seems to be telling us that the general tendency of the universe is to get simpler. So how is it possible to get more complex things? Well as we'll see, energy plays a crucial role in that story. So, how does the idea of energy help us explain this puzzle that more and more complex things seem to have appeared despite the Second Law of Thermodynamics? Well, as long as the universe is not perfectly disorganized, there will always be slight differences, slight gradients, and that means that energy will flow. And it's these flows of energy, free energy it's called technically, that allow the construction of more complex things where the conditions are just right. So energy is our first crucial concept. The second is the idea of emergence. This is a sort of philosophical idea, but it's also a scientific idea. And what it's telling us is that sometimes, where the conditions are just right, bits and pieces, components, can assemble themselves to form something new, something with entirely new qualities. This is emergence. So to give an example, there was a time when there was no life in the universe. Then there was a time where there was. Life seems to have entirely new qualities. So when these new things appear, it always seems magical. That is emergence. The third crucial idea is Goldilocks conditions. You'll remember the story of Goldilocks. The porridge was either too hot or too cold until finally, she found a bowl of porridge that was just right. So, Goldilocks conditions are conditions that are just right for the emergence of more complex things. So for example, we can ask about our early Earth, what were the Goldilocks conditions that allowed life to appear early on the Earth? And the fourth crucial concept is that of thresholds of increasing complexity, and we'll talk about eight of these thresholds. These thresholds are moments in the story when something new emerges, something new is created, when some vital component of our story fell into place. These eight thresholds will provide a sort of skeleton that will hold our story upright. These four ideas, energy, emergence, Goldilocks conditions, and thresholds, all belong together. They all frame our story. Energy is what allows the creation of more complex things in a simple universe. Goldilocks conditions are the perfect conditions that allow something new to appear. When that thing appears, say life, we call it emergence, something new has emerged. And the thresholds, the eight major thresholds, describe the moments at which something new appears. Now we're gonna focus on eight major thresholds, but you need to be aware that there have been lots of thresholds like this. So you'll also see in this course lots of minor thresholds of increasing complexity. I hope that by now you've got some sense of what big history is. Big history surveys the whole history of the universe. It's a very new discipline. It's been made possible only by rapid advances in scientific scholarship in recent years. And it's an incredibly exciting story that it tells. So, we do hope you'll have fun doing this course. [MUSIC]
