Today we’re going to talk about how to keep information secret, and this isn’t a new goal. From as early as Julius Caesar’s Caesar cipher to Mary, Queen of Scots, encrypted messages to kill Queen Elizabeth in 1587, theres has long been a need to encrypt and decrypt private correspondence. This proved especially critical during World War II as Allan Turing and his team at Bletchley Park attempted to decrypt messages from Nazi Enigma machines, and this need has only grown as more and more information sensitive tasks are completed on our computers. So today, we’re going to walk you through some common encryption techniques such as the Advanced Encryption Standard (AES), Diffie-Hellman Key Exchange, and RSA which are employed to keep your information safe, private, and secure.

What is culture? How do we define it and how does it change? We’ll explore different categories of culture, like low culture, high culture, and sub-cultures. We'll also revisit our founding theories to consider both a structural functionalist and a conflict theory perspective on what cultures mean for society.

Cybersecurity is a set of techniques to protect the secrecy, integrity, and availability of computer systems and data against threats. In today’s episode, we’re going to unpack these three goals and talk through some strategies we use like passwords, biometrics, and access privileges to keep our information as secure, but also as accessible as possible. From massive Denial of Service, or DDos attacks, to malware and brute force password cracking there are a lot of ways for hackers to gain access to your data, so we’ll also discuss some strategies like creating strong passwords, and using 2-factor authentication, to keep your information safe.

Hank imagines himself breaking into the Hot Pockets factory to steal their secret recipes and instruction manuals in order to help us understand how the processes known as DNA transcription and translation allow our cells to build proteins.

Hank introduces us to that wondrous molecule deoxyribonucleic acid - also known as DNA - and explains how it replicates itself in our cells.

Watch. Dime. Develop. Powder. Pantry. Dirt. That's right, it's time for a dip into the random, because we're talking about the Dada theater that grew out of Symbolism, and the Surrealist theater that followed Dada. You'll learn about Maurice Maeterlinck, Paul Fort, Lugne Poe, Andre Breton, and Alfred Jarry and his infamous play, Ubu Roi. Along the way, you'll pick up lots of interesting facts. For instance, Jarry's favorite cocktail was made up of absinthe, vinegar, and ink. We don't want to boss you around, but do not ever drink anything like that.

Today, Mike Rugnetta takes you from our beginnings in ancient Greek theater, and moves on to the development of Roman theater. Which, it turns out, is A LOT like Greek theater. Because the Romans were real Grecophiles, they modeled their plays on the Greeks.

John Green teaches you about the so-called Dark Ages, which it turns out weren't as uniformly dark as you may have been led to believe. While Europe was indeed having some issues, many other parts of the world were thriving and relatively enlightened. John covers European Feudalism, the cultural blossoming of the Islamic world, and the scientific and artistic advances in China, all during these "Dark Ages." Along the way, John will raise questions about the validity of Europe's status as a continent, reveal the best and worst years of his life, and frankly state that science and religion were once able to coexist.

Propaganda! Misinformation! Disinformation! Today we’re talking about the dark – or, shall we say, darkER – side of media. Understanding these media bogeymen is essential to being a more media literate citizen.

As the Roman Empire fell, so did the theater. If there's anyone who hates theater and actors more than Romans, it's early Christians. As Christianity ascended in the west, theater declined. But, fear not. This isn't the end of the series. Theater would be back, and in the best subversive theater-y fashion, it would return via the Catholic mass!

In which John Green teaches you about the post-World War II breakup of most of the European empires. As you'll remember from previous installments of Crash Course, Europeans spent several centuries sailing around the world creating empires, despite the fact that most of the places they conquered were perfectly happy to carry on alone. After World War II, most of these empires collapsed. This is the story of those collapses. In most places, the end of empire was not orderly, and violence often ensued. While India was a (sort of) shining example of non-violent change, in places like The Congo, Egypt, Rwanda, Vietnam, Cambodia, and Laos, things didn't go smoothly at all. John brings you all this, plus pictures of Sea Monkeys. Sadly, they don't look anything like those awesome commercials in the comic books.

Today we're going to talk about degrees of freedom - which are the number of independent pieces of information that make up our models. More degrees of freedom typically mean more concrete results. But something that is statistically significant isn't always practically significant. And to measure that, we'll introduce another new concept - effect size.

In which John Green teaches you about the end of World History, and the end of the world as we know it, kind of. For the last hundred years or so, it seemed that one important ingredient for running an economically successful country was a western-style democratic government. All evidence pointed to the idea that capitalist representative democracies made for the best economic outcomes. It turns out that isn't the only way to succeed. In the last 40 years or so, authoritarian capitalism as it's practiced in places like China and Singapore has been working really, really well. John is going to look at these systems and talk about why they work, and he's even going to make a few predictions about the future. Also, thanks for watching this series. It has been amazingly fun to create, and we appreciate all of you.

What is social deviance? Who defines what is deviant and how to people come to behave that way? Today we’re going to explore biological and psychological approaches to explaining deviance, including what each perspective can bring to the table, and their inherent limitations. From there, we’ll explain the sociological perspective and the social foundations of deviance.

Hank takes us through the bowels of the human digestive system and explains why it's all about surface area.

In which John Green teaches you about disease, and the effects that disease has had in human history. Disease has been with man since the beginning, and it has shaped the way humans operate in a lot of ways. John will teach you about the Black Death, the Great Dying, and the modern medical revolution that has changed the world.

In which John Green teaches you a little bit about drought, which is a natural weather phenomenon, and famine, which is almost always the result of human activity. Throughout human history, when food shortages strike humanity, there was food around. There was just a failure to connect those people with the food that would keep them alive. There are a lot of reasons that food distribution breaks down, and John is going to teach you about them in the context of the late-19th century famines that struck British India.

Today we’re talking about mass transfer. It doesn’t just apply to objects and fluids as a whole, but also to the individual molecules and components that make them up. We’ll see that transfers of mass need their own driving force, discuss diffusion, and use Fick’s Law to help us model mass transfer.

We’re continuing our exploration of conflict theories with W.E.B. Dubois, who is one of the founders of sociological thought more broadly and the founder of race-conflict theory. We’ll discuss shifting ideas about race, Dubois’ idea of ‘double-consciousness’, and the modern day field of racial identity. We’ll explore the idea racial formation and discuss Dubois’ survey of African Americans in Philadelphia to look at how economic, political, and social structures affect how we perceive different races – and vice versa. We’ll also discuss the activist side of Dubois’ life as co-founder of the NAACP and editor of the Crisis, and how modern day sociologists study racial politics and racial resistance.

It's Earth Science time!!!! In this field, natural philosophers were asking questions like, what’s up with fossils? Are they the remains of extinct organisms? Or are they so-called “sports of nature”—rocks that just happen to look like living things but don’t /mean/ anything? And most importantly, how old is… everything?