In which John presents Mesopotamia, and the early civilizations that arose around the Fertile Crescent. Topics covered include the birth of territorial kingdoms, empires, Neo-Assyrian torture tactics, sacred marriages, ancient labor practices, the world's first law code, and the great failed romance of John's undergrad years.

Today we’ll explore more about two of the three main types of materials that we use as engineers: metals and ceramics. We’ll discuss properties of metals, alloys, ceramics, clay, cement, and glass-ceramic materials. We’ll also look at the applications of our materials with microelectromechanical systems and accelerometers.

It's all about the SUPER TINY in this episode of Crash Course: History of Science. In it, Hank Green talks about germ theory, John Snow (the other one), pasteurization, and why following our senses isn't always the worst idea.

Just how small are nanomaterials? And what can we do with stuff that small? Today we’ll discuss some special properties of nanomaterials, how some can change at different sizes, and the difference between engineered nanomaterials and ones that occur naturally. We’ll also talk about some of the future research that’s needed on the use of nanomaterials.

Scientists in the nineteenth century discovered a lot about life and matter. But exactly what kind of stuff is the human brain? That one was—and is—tricky.

The brain sciences—with experiments and therapies tied to biological theories of the body—emerged in the nineteenth century and came into their own in the early twentieth.

Hank describes mitosis and cytokinesis - the series of processes our cells go through to divide into two identical copies.

In which John Green teaches about filthy, filthy lucre. Money. And Debt. So, what is money? And what is it for? And why do we use money? And why does it all disappear so quickly after payday? John will look into 75% of these questions, and if he doesn't come up with answers, we'll get into some interesting ideas along the way, at least. This week we'll investigate whether money displaces barter, then leads to war, slavery, and what we think of as civilized social orders. We'll also see what old Adam Smith thinks of big money, no whammies, this week on Crash Course.

In which John Green teaches you about the Mughal Empire, which ruled large swaths of the Indian Sub-Continent from 1526 to (technically) 1857. While John teaches you about this long-lived Muslim empire, he'll also look at the idea of historical reputation and how we view people from history. Namely, he'll look at the reputations of Mughal emperors Akbar I and Aurangzeb. Traditionally, Akbar I is considered the emperor that made the Mughal Empire great, and Aurangzeb gets the blame for running the whole thing into the ground and setting it up for decline. Is that really how it was, though? It turns out, it's complicated.

Today we’re going to talk about how computers understand speech and speak themselves. As computers play an increasing role in our daily lives there has been an growing demand for voice user interfaces, but speech is also terribly complicated. Vocabularies are diverse, sentence structures can often dictate the meaning of certain words, and computers also have to deal with accents, mispronunciations, and many common linguistic faux pas. The field of Natural Language Processing, or NLP, attempts to solve these problems, with a number of techniques we’ll discuss today. And even though our virtual assistants like Siri, Alexa, Google Home, Bixby, and Cortana have come a long way from the first speech processing and synthesis models, there is still much room for improvement.

Hank guides us through the process of natural selection, the key mechanism of evolution.

Hank begins a series of videos on organ systems with a look at the nervous system and all of the things that it is responsible for in the body.

Today we're going to talk big picture about what Neural Networks are and how they work. Neural Networks, which are computer models that act like neurons in the human brain, are really popular right now - they're being used in everything from self-driving cars and Snapchat filters to even creating original art! As data gets bigger and bigger neural networks will likely play an increasingly important role in helping us make sense of all that data.

There’s a question to consider that’s pretty daunting: what is life?
And to try to answer that question, three tools stand out as being especially useful: A book, some experiments, and the microscope! In this episode, Hank talks to us about all kinds of gross things! It's fun!

This week on Crash Course: History of the Scientific Revolution—astronomical anomalies accrued. Meanwhile, in Denmark—an eccentric rich dude constructed not one but two science castles! And his humble German assistant synthesized a lot of new, old, and bold astronomical ideas into a single sun-centered, eccentricity-positive system…

One of the problems with the whole idea of a single Scientific Revolution is that some disciplines decided not to join any revolution. And others just took a long time to get there.

The standard story of the Scientific Revolution culminates with the long life of one man: Sir Isaac Newton—a humble servant of the Royal Mint, two-time parliamentarian, and a scientific titan whose name, along with Einstein’s, is synonymous with physics today.

Hank describes the desperate need many organisms have for nutrients (specifically nitrogen and phosphorus) and how they go about getting them via the nitrogen and phosphorus cycles.

In which John Green teaches you about nonviolence and peace movements in the 20th century. What is nonviolence? What is a peace movement? Well. traditionally, humans often resort to violence when they come into conflict. In the 20th century, it became much more common for people to enact change by means of nonviolence, and there was a common thread of connection between many of the most notable advocates of peaceful change. Crash Course will take you from Gandhi to Gregg to Bayard Rustin to Martin Luther King, Jr, to the Cold War to Arab Spring along a path of nonviolent resistance and peaceful change. It's pretty great.

Today is the day we finally talk about the normal distribution! The normal distribution is incredibly important in statistics because distributions of means are normally distributed even if populations aren't. We'll get into why this is so - due to the Central Limit Theorem - but it's useful because it allows us to make comparisons between different groups even if we don't know the underlying distribution of the population being studied.

Ancient Sanskrit theater is one of the oldest theater traditions, and thanks to Bharata Muni and his treatise on theater, the Natyashastra, we can tell you quite a bit about it, all the way down to eyebrow and nostril poses. This week you'll learn about the drama of ancient India, and its connection to the Mahabharata and the Ramayana.