Today we’re going to build the ticking heart of every computer - the Central Processing Unit or CPU. The CPU’s job is to execute the programs we know and love - you know like GTA V, Slack... and Power Point. To make our CPU we’ll bring in our ALU and RAM we made in the previous two episodes and then with the help of Carrie Anne’s wonderful dictation (slowly) step through some clock cycles. WARNING: this is probably the most complicated episode in this series, we watched this a few times over ourselves, but don't worry at about .03Hz we think you can keep up.

In which John Green teaches you about the Holy Roman Empire by teaching you about Charles V. Charles Hapsburg was the holy Roman Emperor, but he was also the King of Spain. And the King of Germany. And the King of Italy and the Lord of the Netherlands and Count Palatine of Burgundy. In short, Charles was runnin' thangs in much of the world during his reign. Charles ruled a lot of countries, and he was also known for encouraging intellectual discourse and he even spoke out against slavery, in a limited. So why did he consider himself a failure, and why did he break up the Empire when he abdicated in 1556? Mainly because the Holy Roman Empire didn't work very well. It was huge, and it didn't have any means of directly raising taxes. Plus, it was a pretty crazy time in Europe anyway, and Charles found himself in charge of the Catholic-Church-Endorsed Empire in the time of Martin Luther and the Protestant Reformation. John will teach you a bit about how Charles put the Empire together, and how it fell apart, and even talk a bit about the Diet of Worms.

Today we're going to start our two-part unit on data visualization. Up to this point we've discussed raw data - which are just numbers - but usually it's much more useful to represent this information with charts and graphs. There are two types of data we encounter, categorical and quantitative data, and they likewise require different types of visualizations. Today we'll focus on bar charts, pie charts, pictographs, and histograms and show you what they can and cannot tell us about their underlying data as well as some of the ways they can be misused to misinform.

Engineering, like life, could really use a lot more cheese. This week we are looking at a cheese factory in Toronto and what it can teach us about process control systems. We’ll explore feedforward and feedback systems, and see how integrating them both with the final check of cascade control creates a system made to handle uncertainty the world throws its way.

Get ready for Russian modernism. Mike is teaching you about the playwrighting of Catherine the Great, Anton Chekhov's plays, the Moscow Art Theatre, and the acting theories of Stanislavski. It's all very real, and very modern. From a Realism and Modernism perspective.

Today we're going to talk about Chi-Square Tests - which allow us to measure differences in strictly categorical data like hair color, dog breed, or academic degree. We'll cover the three main Chi-Square tests: goodness of fit test, test of independence, and test of homogeneity. And explain how we can use each of these tests to make comparisons.

This week we're headed to China to learn about the ancient origins of theater there. We'll look at the early days of wizard theater (not a typo), the development of classical Chinese theater, and the evolution of Beijing Opera.

Hank introduces us to ourselves by taking us on a journey through the fascinatingly diverse phyla known as chordata. And the next time someone asks you who you are, you can give them the facts: you're a mammalian amniotic tetrapodal sarcopterygian osteichthyen gnathostomal vertebrate cranial chordate.

In which John Green teaches you about the fall of the Roman Empire, which happened considerably later than you may have been told. While the Western Roman Empire fell to barbarians in 476 CE, the Byzantines in Constantinople continued the Eastern Empire nicely, calling themselves Romans for a further 1000 years. Find out what Justinian and the rest of the Byzantine emperors were up to over there, and how the Roman Empire dragged out its famous Decline well into medieval times. In addition to all this, you'll learn about ancient sports riots and hipster barbarians, too.

Radio, Cinema, and Television have been staples in news coverage, entertainment, and education for almost 100 years. But... where did they all come from? Who started what and when and why? In this episode, Hank Green talks to us about their birth and a dead elephant.

Hank takes us on a trip around the body - we follow the circulatory and respiratory systems as they deliver oxygen and remove carbon dioxide from cells, and help make it possible for our bodies to function.

We’re beginning our engineering journey with a tour through the major branches. Today Shini explains the facets of civil engineering, including structural and construction engineering, city planning, transportation, and sanitation.

In which John Green teaches you about the Little Ice Age. The Little Ice Age was a period of global cooling that occurred from the 13th to the 19th centuries. This cooling was likely caused by a number of factors, including unusual solar activity and volcanic eruptions. The Little Ice Age greatly impacted human social orders, especially during the 17th century. When the climate changed, and weather became unpredictable, the world changed profoundly. Poor harvests led to hunger, which led to even less productivity, which even resulted in violent upheaval in a lot of places. All this from a little change in the temperature? Definitely.

In which John Green wraps up revolutions month with what is arguably the most revolutionary of modern revolutions, the Industrial Revolution. While very few leaders were beheaded in the course of this one, it changed the lives of more people more dramatically than any of the political revolutions we've discussed. So, why did the Industrial Revolution happen around 1750 in the United Kingdom? Coal. Easily accessible coal, it turns out. All this, plus you'll finally learn the difference between James Watt and Thomas Newcomen, and will never again be caught telling people that your blender has a 900 Newcomen motor.

Today we’re going to step back from hardware and software, and take a closer look at how the backdrop of the cold war and space race and the rise of consumerism and globalization brought us from huge, expensive codebreaking machines in the 1940s to affordable handhelds and personal computers in the 1970s. This is an era that saw huge government funded projects - like the race to the moon. And afterward, a shift towards the individual consumer, commoditization of components, and the rise of the Japanese electronics industry.

Over the last four episodes, we’ve examined some of the stories that make up the idea of a “revolution” in knowledge-making in Europe. But we can’t understand this idea fully, without unpacking another one—the so called Age of Exploration. This encompasses a lot of events that happened from 1400 through the 1600s and were driven in part by new ideas about knowledge-making.

In which John Green teaches you about the changes wrought by contact between the Old World and the New. John does this by exploring the totally awesome history book "The Columbian Exchange" by Alfred Cosby, Jr. After Columbus "discovered" the Americas, European conquerors, traders, and settlers brought all manner of changes to the formerly isolated continents. Disease and invasive plant and animal species remade the New World, usually in negative ways. While native people, plants, and animals were being displaced in the Americas, the rest of the world was benefitting from American imports, especially foods like maize, tomatoes, potatoes, pineapple, blueberries, sweet potatoes, and manioc. Was the Columbian Exchange a net positive? It's debatable. So debate.

In which John Green teaches you about the beginning of the so-called Age of Discovery. You've probably heard of Christopher Columbus, who "discovered" America in 1492, but what about Vasco da Gama? How about Zheng He? Columbus gets a bad rap from many modern historians, but it turns out he was pretty important as far as the history of the world goes. That said, he wasn't the only pioneer plying the seas in the 1400s. In Portugal, Vasco da Gama was busy integrating Europe into the Indian Ocean Trade by sailing around Africa. Chinese admiral Zheng He was also traveling far and wide in the largest wooden ships ever built. Columbus, whether portrayed as hero or villain, is usually credited as the great sailor of the 15th century, but he definitely wasn't the only contender. What better way to settle this question than with a knock-down, drag-out, no holds barred, old-fashioned battle royal? We were going to make it a cage match, but welding is EXPENSIVE.

This week we're continuing our discussion of William Shakespeare and looking at his comedies and romances. As well as something called problem plays. Some of his plays, they had problems. We'll also put on pants, escape to forest, and talk about Shakepeare's heroines, lots of whom had quite a bit more agency in these plays than the women in the tragedies had.

In which John Green teaches you about China's Revolutions. While the rest of the world was off having a couple of World Wars, China was busily uprooting the dynastic system that had ruled there for millennia. Most revolutions have some degree of tumult associated with them, but China's 20th century revolutions were REALLY disruptive. In 1911 and 1912, Chinese nationalists brought 3000 years of dynastic rule to an end. China plunged into chaos as warlords staked out regions of the country for themselves. The nationalists and communists joined forces briefly to bring the nation back together under the Chinese Republic, and then they quickly split and started fighting the Chinese Civil War. The fight between nationalists and communists went on for decades, and was interrupted by an alliance to fight the invading Japanese during World War II. After the World War II ended, the Chinese Civil War was back on. Mao and the communists were ultimately victorious, and Chiang Kai-Shek ended up in Taiwan. And then it got weird. Mao spent years repeatedly trying to purify the Communist Party and build up the new People's Republic of China with Rectifications, Anti Campaigns, Five Year Plans. the Great Leap Forward, and the Cultural Revolution. These had mixed results, to say the least. John will cover all this and more in this week's Crash Course World History.