The Silk Road and Ancient Trade: In which John Green teaches you about the so-called Silk Road, a network of trade routes where goods such as ivory, silver, iron, wine, and yes, silk were exchanged across the ancient world, from China to the West. Along with all these consumer goods, things like disease and ideas made the trip as well. As is his custom, John ties the Silk Road to modern life, and the ways that we get our stuff today.

Hank introduces us to the "simplest" of the animals, complexity-wise: beginning with sponges (whose very inclusion in the list as "animals" has been called into question because they are so simple) and finishing with the most complex molluscs, octopuses and squid. We differentiate them by the number of tissue layers they have, and by the complexity of those layers.

Hank introduces us to the framework of our bodies, our skeleton, which apart from being the support and protection for all our fleshy parts, is involved in many other vital processes that help our bodies to function properly.

What if you were on a high floor of a skyscraper and the building started swaying? Today we’ll explore statics and dynamics, and what they mean for the structures we design. We look at the idea of static equilibrium, forces, and torques, and how free body diagrams can help us make sense of it all.

Today we’re breaking down the five different social class in the United States: the upper class, the upper middle class, the average middle class, the working class, and the lower class. We’ll also go over what poverty looks like in the United States.

What makes you… you? How did you get to be that way? Today we’re talking about social development, starting with the role of nature and nurture in influencing a person’s development. We’ll discuss socialization, the importance of care & human interaction, as well as theories of development from a range of theorists.

How do the groups that you're part of affect you? How do you, in turn, affect those groups? Today we are talking about how people in society come together with a look at social groups. We’ll look at what social groups are, the different kinds of groups that exist, group dynamics, leadership, conformity, networks and more!

How do sociologists study and understand social interaction? Today we’ll explain the language sociologists use to discuss how we interact with the social world. What are statuses and roles? How are they different? How do you acquire them? We’ll talk about why these things matter by exploring the socially constructed nature of reality. We’ll also discuss the theory of dramaturgical analysis and how we can understand social interaction as in terms of theatrical performance.

Today we’re exploring social mobility in some more depth. We’ll look at intergenerational and intragenerational mobility and the difference between absolute and relative mobility. We’ll go over the long run upward social mobility trends in the United States, as well as recent declines in absolute social mobility. We’ll also explore how opportunities for social mobility differ by class, race, and gender.

How do different societies establish a social hierarchy? Today we’re starting our unit on social stratification, starting with four basic principles of a sociological understanding of stratification. We’ll explain open and closed systems of stratification and explore examples of different kinds of stratification systems, including caste systems and class systems.

Social class in America is... hard to talk about. As Sociology, the difficulty lies in pinning down what we mean by "Social Class." In this episode of Crash Course Sociology, Nicole chats to us about how Sociologists figure this out so we can all have a clearer idea of what we're talking about.

Last week we introduced the idea of socialization and today we’re talking a little more about how it works, including an introduction to five main types of socialization. We’ll explore anticipatory socialization from your family, the “hidden curriculum” in schools, peer groups, the role of media in socialization, and we’ll discuss total institutions and how they can act as a form of re-socialization.

Today we’re talking about how we actually DO sociology. Nicole explains the research method: form a question and a hypothesis, collect data, and analyze that data to contribute to our theories about society.

What puts the “science” in social science? Today we’ll explore positivist sociology and how sociologists use empirical evidence to explore questions about the social world. We’ll also introduce two alternatives: interpretative sociology and critical sociology.

Today, we’re going to talk about how HUGE programs with millions of lines of code like Microsoft Office are built. Programs like these are way too complicated for a single person, but instead require teams of programmers using the tools and best practices that form the discipline of Software Engineering. We'll talk about how large programs are typically broken up into into function units that are nested into objects known as Object Oriented Programming, as well as how programmers write and debug their code efficiently, document and share their code with others, and also how code repositories are used to allow programmers to make changes while mitigating risk.

In which John Green explores how Spain went from being a middling European power to one of the most powerful empires on Earth, thanks to their plunder of the New World in the 16th and 17th centuries. Learn how Spain managed to destroy the two biggest pre-Columbian civilizations, mine a mountain made of silver, mishandle their economy, and lose it all by the mid-1700s. Come along for the roller coaster ride with Charles I (he was also Charles V), Philip II, Atahualpa, Moctezuma, Hernán Cortés, and Francisco Pizarro as Spain rises and falls, and takes two empires and China down with them.

This week on Crash Course Theater, Mike and Yorick take us to beautiful Spain, and look at its Golden Age. Spain was having kind of a moment in the 16th and 17th centuries. They had this big empire, the culture was really flowering, and Humanism was popping up all over, but they also had the inquisition. Into this world came prolific writers like Felix Lope de Vega and Pedro Calderon de la Barca. And they wrote a ton of plays.

Hank explains speciation - the evolutionary process by which new biological species arise - in terms of finches, ligers, mules, and dogs.

One way of thinking about family life says that there are stages that families move through: courtship, marriage, child-rearing, and family life in your later years. We’ll also discuss changing patterns of marriage and childbearing in the US, highlighting some of the varied family types that exist.

As we near the end of the series, we're going look at how statistics impacts our lives. Today, we're going to discuss how statistics is often used and misused in the courtroom. We're going to focus on three stories in which three huge statistical errors were made: the handwriting analysis of French officer Alfred Dreyfus in 1894, the murder charges of mother Sally Clark in 1998, and the expulsion of student Jonathan Dorfman from UC San Diego in 2011.