You're the realm's greatest mathematician, but ever since you criticized the Emperor's tax laws, you've been locked in the dungeon. Luckily for you, one of the Emperor's governors has been convicted of paying his taxes with a counterfeit coin, which has made its way into the treasury. Can you earn your freedom by finding the fake? Jennifer Lu shows how. [Directed by Artrake Studio, narrated by Addison Anderson].

You’re the realm’s greatest mathematician, but ever since you criticized the Emperor’s tax laws, you’ve been locked in the dungeon. Luckily for you, one of the Emperor’s governors has been convicted of paying his taxes with a counterfeit coin, which has made its way into the treasury. Can you earn your freedom by finding the fake? Jennifer Lu shows how. Lesson by Jennifer Lu, animation by Artrake Studio.

Humans know the surprising prick of a needle, the searing pain of a stubbed toe, and the throbbing of a toothache. We can identify many types of pain and have multiple ways of treating it — but what about other species? How do the animals all around us experience pain? Robyn J. Crook examines pain in both vertebrate and invertebrate animals. [Directed by Anton Bogaty, narrated by Julianna Zarzycki].

1, 2, 3, 4, 5, 6, 7, 8, 9... and 0. With just these ten symbols, we can write any rational number imaginable. But why these particular symbols? Why ten of them? And why do we arrange them the way we do? Alessandra King gives a brief history of numerical systems. Lesson by Alessandra King, animation by Zedem Media.

Imagine a neuroscientist who has only ever seen black and white things, but she is an expert in color vision and knows everything about its physics and biology. If, one day, she sees color, does she learn anything new? Is there anything about perceiving color that wasn't captured in her knowledge? Eleanor Nelsen explains what this thought experiment can teach us about experience. [Directed by Maxime Dupuy, narrated by Addison Anderson, music by Martin Pinon].

What's your sign? In Western astrology, it's a constellation determined by when your birthday falls in the calendar. But according to the Chinese zodiac (生肖), it's your shuxiang, meaning the animal assigned to your birth year. And of the many myths explaining these animal signs and their arrangement, the most enduring one is that of The Great Race. Megan Campisi and Pen-Pen Chen recount this classic myth. [Directed by Marta Prokopová, narrated by Pen-Pen Chen, music by WORKPLAYWORK and Cem Misirlioglu].

What’s your sign? In Western astrology, it’s a constellation determined by when your birthday falls in the calendar. But according to the Chinese zodiac (生肖), it’s your shuxiang, meaning the animal assigned to your birth year. Of the many myths explaining these animal signs and their arrangement, the most enduring one is that of The Great Race. Megan Campisi and Pen-Pen Chen recounts this classic myth. Lesson by Megan Campisi and Pen-Pen Chen, animation by Marta Prokopová.

In 1995, scientists pointed the Hubble Telescope at an area of the sky near the Big Dipper. The location was apparently empty, and the whole endeavor was risky – what, if anything, was going to show up? But what came back was nothing short of spectacular: an image of over 1,500 galaxies glimmering in a tiny sliver of the universe. Alex Hofeldt helps us understand the scale of this image. Lesson by Alex Hofeldt, animation by Bliink. Hubble Deep Field Image Credit: R. Williams (STScI), the Hubble Deep Field Team, and NASA.

Approximately seven million people around the world die from heart attacks every year. And cardiovascular disease, which causes heart attacks and other problems like strokes, is the world's leading killer. So what causes a heart attack? Krishna Sudhir examines the leading causes and treatments of this deadly disease. [Directed by Chadwick Whitehead, narrated by Addison Anderson, music by Dreikelvin Media & Sound].

You and your team have crash-landed on an ancient planet. Can you appease the three alien overlords who rule it and get your team safely home? Created by logician Raymond Smullyan, and popularized by his colleague George Boolos, this riddle has been called the hardest logic puzzle ever. Alex Gendler shows how to solve it. [Directed by Artrake Studio, narrated by Addison Anderson].

Mastering any physical skill takes practice. Practice is the repetition of an action with the goal of improvement, and it helps us perform with more ease, speed, and confidence. But what does practice actually do to make us better at things? Annie Bosler and Don Greene explain how practice affects the inner workings of our brains. [Directed by Martina Meštrović, narrated by Addison Anderson, music by Wonder Boy Audio].

In 1884, the British steamer “Rumney” crashed into the French ship “Frigorifique.” Seeing their ship filling with water, the French crew climbed aboard the “Rumney.” But as they sailed towards port, a silent form emerged from the fog – the abandoned “Frigorifique,” seemingly back for revenge. So what happened? Peter B. Campbell investigates the fascinating phenomenon of ghost ships. Lesson by Peter B. Campbell, animation by Zedem Media.

Are you afraid of black cats? Would you open an umbrella indoors? How do you feel about the number 13? Whether or not you believe in them, you’re probably familiar with a few of these superstitions. But where did they come from? Stuart Vyse shares the weird and specific origins of some of our favorite superstitions. Lesson by Stuart Vyse, directed by TED-Ed, animation by Jérémie Balais and Jeff Le Bars.

In mythological ancient Greece, Icarus flew above Crete on wings made from wax and feathers, defying the laws of man and nature. To witnesses on the ground, he looked like a god, and he felt like one too. But, in his society, the line that separated god from man was absolute, and the punishment for mortals who attempted to cross it was severe. Amy Adkins explains the myth of Icarus and Daedalus. [Directed by TED-Ed, narrated by Addison Anderson].

If you can't imagine life without chocolate, you're lucky you weren't born before the 16th century. Until then, chocolate only existed as a bitter, foamy drink in Mesoamerica. So how did we get from a bitter beverage to the chocolate bars of today? Deanna Pucciarelli traces the fascinating and often cruel history of chocolate. [Directed by TED-Ed, narrated by Addison Anderson].

If you can’t imagine life without chocolate, you’re lucky you weren’t born before the 16th century. Until then, chocolate only existed as a bitter, foamy drink in Mesoamerica. So how did we get from a bitter beverage to the chocolate bars of today? Deanna Pucciarelli traces the fascinating and often cruel history of chocolate. Lesson by Deanna Pucciarelli, animation by TED-Ed.

Without water, a human can only survive for about 100 hours. But there's a creature so resilient that it can go without it for decades. This 1-millimeter animal can survive both the hottest and coldest environments on earth, and can even withstand high levels of radiation. Thomas Boothby introduces us to the tardigrade, one of the toughest creatures on Earth. [Directed by Boniato Studio, narrated by Addison Anderson, music by Erwann Chandon].

The bacteria in our guts can break down food the body can't digest, produce important nutrients, regulate the immune system, and protect against harmful germs. And while we can't control all the factors that go into maintaining a healthy gut microbiome, we can manipulate the balance of our microbes by paying attention to what we eat. Shilpa Ravella shares the best foods for a healthy gut. [Directed by Andrew Foerster, narrated by Julianna Zarzycki].

Your research team has found a prehistoric virus preserved in the permafrost and isolated it for study. After a late night working, you're just closing up the lab when a sudden earthquake hits and breaks all the sample vials. Will you be able to destroy the virus before the vents open and unleash a deadly airborne plague? Lisa Winer shows how. [Directed by Artrake Studio, narrated by Addison Anderson].

Your research team has found a prehistoric virus preserved in the permafrost and isolated it for study. After a late night working, you’re just closing up the lab when a sudden earthquake hits and breaks all the sample vials. Will you be able to destroy the virus before the vents open and unleash a deadly airborne plague? Lisa Winer shows how. Lesson by Lisa Winer, animation by Artrake Studio.

For the microscopic lab worm C. elegans, life equates to just a few short weeks on Earth. The bowhead whale, on the other hand, can live over two hundred years. Why are these lifespans so different? And what does it really mean to 'age' anyway? Joao Pedro de Magalhaes explains why the pace of aging varies greatly across animals. [Directed by Sharon Colman, narrated by Addison Anderson, music by Peter Gosling].

For the microscopic lab worm C. elegans, life equates to just a few short weeks on Earth. The bowhead whale, on the other hand, can live over two hundred years. Why are these lifespans so different? And what does it really mean to ‘age' anyway? Joao Pedro de Magalhaes explains why the pace of aging varies greatly across animals. Lesson by Joao Pedro de Magalhaes, animation by Sharon Colman.

Focus groups have been widely used by organizations and individuals to find out how their products and ideas will be received by an audience. From the usage of household products to a politician's popularity, almost everything can be explored with this technique. But how are focus groups put together? And how did they come about in the first place? Hector Lanz explains how focus groups work. [Directed by Dmitry Yagodin, narrated by Addison Anderson].

The average person experiences dozens of individual itches each day. We've all experienced the annoyance of an inconvenient itch — but have you ever pondered why we itch in the first place? Is there actually an evolutionary purpose to the itch, or is it simply there to annoy us? Emma Bryce digs deep into the skin to find out. [Directed by Sashko Danylenko, narrated by Addison Anderson].

All mammals share certain characteristics, like warm blood and backbones. But despite their similarities, these creatures also have many biological differences — and one of the most remarkable differences is how they give birth. Kate Slabosky details the placental, marsupial, and monotreme methods of giving birth. [Directed by Compote Collective, narrated by Julianna Zarzycki, music by Big Banda Soundscapers].

Genitals are the fastest-evolving organs in the animal kingdom. But why is this so? And what's the point of having decorative private parts? Menno Schilthuizen explains how the evolutionary biology of nature's nether regions uncovers a hidden world of seduction, conflict, and rivalry. [Directed by Mette Ilene Holmriis, narrated by Adrian Dannatt, music by Wonder Boy Audio].

Sloths spend most of their time eating, resting, or sleeping; in fact, they descend from their treetops canopies just once a week, for a bathroom break. How are these creatures so low energy? Kenny Coogan describes the physical and behavioral adaptations that allow sloths to be so slow. [Directed by Anton Bogaty, narrated by Addison Anderson].

It's a good day to be a pirate. Amaro and his four mateys – Bart, Charlotte, Daniel, and Eliza have struck gold – a chest with 100 coins. But now, they must divvy up the booty according to the pirate code — and pirate code is notoriously complicated. Can you help come up with the distribution that Amaro should propose to make sure he lives to tell the tale? Alex Gendler shows how. [Directed by Artrake Studio, narrated by Addison Anderson].

It’s a good day to be a pirate. Amaro and his four mateys – Bart, Charlotte, Daniel, and Eliza have struck gold – a chest with 100 coins. But now, they must divvy up the booty according to the pirate code — and pirate code is notoriously complicated. Can you help come up with the distribution that Amaro should propose to make sure he lives to tell the tale? Alex Gendler shows how. Lesson by Alex Gendler, animation by Artrake Studio.

There’s a concept that’s crucial to chemistry and physics. It helps explain why physical processes go one way and not the other: why ice melts, why cream spreads in coffee, why air leaks out of a punctured tire. It’s entropy, and it’s notoriously difficult to wrap our heads around. Jeff Phillips gives a crash course on entropy. Lesson by Jeff Phillips, animation by Provincia Studio.

Have you ever wondered what happens to a painkiller, like ibuprofen, after you swallow it? Medicine that slides down your throat can help treat a headache, a sore back, or a throbbing sprained ankle. But how does it get where it needs to go in the first place? Céline Valéry explains how your body processes medicine. [Directed by Daniel Gray, narrated by Julianna Zarzycki, music by Samuel Baker].

Tea is the second most consumed beverage in the world after water –– and from sugary Turkish Rize tea to salty Tibetan butter tea, there are almost as many ways of preparing the beverage as there are cultures on the globe. Where did this beverage originate, and how did it become so popular? Shunan Teng details tea's long history. [Directed by Steff Lee, narrated by Pen-Pen Chen, music by Gav Cantrell].

Tea is the second most consumed beverage in the world after water –– and from sugary Turkish Rize tea to salty Tibetan butter tea, there are almost as many ways of preparing the beverage as there are cultures on the globe. Where did this beverage originate, and how did it become so popular? Shunan Teng details tea’s long history. Lesson by Shunan Teng, animation by Steff Lee.

What do fans of atmospheric post-punk music have in common with ancient barbarians? Not much ... so why are both known as "goths"? Is it a weird coincidence – or is there a deeper connection stretching across the centuries? Dan Adams investigates. [Directed by Globizco, narrated Addison Anderson, music by Manuel Borda].

When radium was first discovered, its luminous green color inspired people to add it into beauty products and jewelry. It wasn't until much later that we realized that radium's harmful effects outweighed its visual benefits. Unfortunately, radium isn't the only pigment that historically seemed harmless or useful but turned out to be deadly. J. V. Maranto details history's deadliest colors. [Directed by Juan M. Urbina, narrated by Susan Zimmerman, music by Camilo Vega].

Deep inside Yale's Beinecke Rare Book and Manuscript Library lies a 240 page tome. Recently carbon dated to around 1420, its pages feature looping handwriting and hand drawn images seemingly stolen from a dream. It is called the Voynich manuscript, and it's one of history's biggest unsolved mysteries. The reason why? No one can figure out what it says. Stephen Bax investigates this cryptic work. [Directed by TED-Ed, narrated by Pen-Pen Chen, music by Wonder Boy Audio].

Deep inside Yale's Beinecke Rare Book and Manuscript Library lies a 240 page tome. Recently carbon dated to around 1420, its pages feature looping handwriting and hand drawn images seemingly stolen from a dream. It is called the Voynich manuscript, and it’s one of history’s biggest unsolved mysteries. The reason why? No one can figure out what it says. Stephen Bax investigates this cryptic work. Lesson by Stephen Bax, animation by TED-Ed.

In ancient Rome, Vestal Virgins were tasked with keeping vigil over the flame of Vesta, the virgin goddess of the hearth. The flame represented two things: the continuation of Rome as a power in the world and the continuing virginity of Vesta's priestesses. But what was life really like for these Vestal Virgins? Peta Greenfield goes back in time to find out. [Directed by Kozmonot Animation Studio, narrated by Susan Zimmerman, music by Wonder Boy Audio].

Perpetual motion machines — devices that can do work indefinitely without any external energy source — have captured many inventors' imaginations because they could totally transform our relationship with energy. There's just one problem: they don't work. Why not? Netta Schramm describes the pitfalls of perpetual motion machines. [Directed by TED-Ed, narrated by Addison Anderson].

Perpetual motion machines — devices that can do work indefinitely without any external energy source — have captured many inventors’ imaginations because they could totally transform our relationship with energy. There’s just one problem: they don’t work. Why not? Netta Schramm describes the pitfalls of perpetual motion machines. Lesson by Netta Schramm, animation by TED-Ed.

Marie Skłodowska Curie's revolutionary research laid the groundwork for our understanding of physics and chemistry, blazing trails in oncology, technology, medicine, and nuclear physics, to name a few. But what did she actually do? Shohini Ghose expounds on some of Marie Skłodowska Curie's most revolutionary discoveries. [Directed by Anna Nowakowska, narrated by Julianna Zarzycki, music by Matthias Runge].

Today, there are thousands of cults around the world. Broadly speaking, a cult is a group or movement with a shared commitment to a usually extreme ideology that's typically embodied in a charismatic leader. But what exactly differentiates cults from other groups – and why do people join them? Janja Lalich describes how cults recruit and manipulate their members. [Directed by Globizco, narrated by Addison Anderson, music by Manuel Borda].

Imagine you were asked to invent something new. It could be whatever you want, made from anything you choose, in any shape or size. That kind of creative freedom sounds so liberating, doesn't it? Or ... does it? if you're like most people you'd probably be paralyzed by this task. Why? Brandon Rodriguez explains how creative constraints actually help drive discovery and innovation. [Directed by Bálint Farkas Gelley, narrated by Addison Anderson].

What is the best life we can live? How can we cope with whatever the universe throws at us and keep thriving nonetheless? The ancient Greco-Roman philosophy of Stoicism explains that while we may not always have control over the events affecting us, we can have control over how we approach things. Massimo Pigliucci describes the philosophy of Stoicism. Lesson by Massimo Pigliucci, animation by Compote Collective

When they’re used well, graphs can help us intuitively grasp complex data. But as visual software has enabled more usage of graphs throughout all media, it has also made them easier to use in a careless or dishonest way — and as it turns out, there are plenty of ways graphs can mislead and outright manipulate. Lea Gaslowitz shares some things to look out for. Lesson by Lea Gaslowit, animation by Mark Phillips.

The human brain is visibly split into a left and right side. This structure has inspired one of the most pervasive ideas about the brain: that the left side controls logic and the right side controls creativity. And yet, this is a myth, unsupported by scientific evidence. So how did this idea come about, and what does it get wrong? Elizabeth Waters looks into this long held misconception. [Directed by Daniel Gray, narrated by Addison Anderson].

Each year in the United States, players of sports and recreational activities receive between 2.5 and 4 million concussions. How dangerous are all those concussions? The answer is complicated and lies in how the brain responds when something strikes it. Clifford Robbins explains the science behind concussions. Lesson by Clifford Robbins, directed by Boniato Studio.

Water is refreshing, hydrating, and invaluable to your survival. But clean water remains a precious and often scarce commodity – there are nearly 800 million people who still don’t have regular access to it. Why is that? And how can you tell whether the water you have access to — whether from a tap or otherwise — is drinkable? Mia Nacamulli examines water contamination and treatment. Lesson by Mia Nacamulli, directed by Rooftop Animation.

When most people think of fishing, we imagine relaxing in a boat and patiently reeling in the day's catch. But modern industrial fishing -- the kind that stocks our grocery shelves -- looks more like warfare. Ayana Elizabeth Johnson and Jennifer Jacquet explain overfishing and its effects on ecosystems, food security, jobs, economies, and coastal cultures. [Directed by Anton Bogaty, narrated by Pen-Pen Chen].

On August 13, 1961, construction workers began tearing up streets and erecting barriers in Berlin. This night marked the beginning of one of history’s most infamous dividing lines: the Berlin Wall. Construction continued for a decade as the wall cut through neighborhoods, separated families, and divided not just Germany, but the world. Konrad H. Jarausch details the history of the Berlin Wall. Lesson by Konrad H. Jarausch, directed by Remus & Kiki.

Eighty-five percent of the matter in our universe is dark matter. We don’t know what dark matter is made of, and we’ve yet to directly observe it, but scientists theorize that we may actually be able to create it in the Large Hadron Collider, the most powerful particle collider in the world. So how would that work? CERN scientist Rolf Landua explains how to discover a new particle. Lesson by Rolf Landua, directed by Lazy Chief.

For most jobs, it's understood that you can be fired – whether for crime, incompetence, or just poor performance. But what if your job happens to be the most powerful position in the country – or the world? That's where impeachment comes in. But how does it work? Alex Gendler details the process of impeachment. [Directed by Mark Phillips, narrated by Addison Anderson].

The universe is bustling with matter and energy. Even in the vast, apparent emptiness of intergalactic space, there’s one hydrogen atom per cubic meter. But is there such thing as a total absence of everything? Is it possible to make a completely empty space? Rolf Landua and Anais Rassat explain the science behind vacuums. Lesson by Rolf Landua and Anais Rassat, directed by Karrot Animation.

They say the pen is mightier than the sword, and authorities have often agreed. From outlawed religious tracts and revolutionary manifestos to censored and burned books, we know the potential power of words to overturn the social order. But as strange as it may seem, some numbers have also been considered dangerous enough to ban. Alessandra King details the history behind illegal numbers. Lesson by Alessandra King, directed by Juan M. Urbina Studios.

We’ve harnessed electricity, sequenced the human genome, and eradicated smallpox. But after billions of dollars in research, we haven’t found a solution for a disease that affects more than 14 million people and their families at any given time. Why is it so difficult to cure cancer? Kyuson Yun explains the challenges. Lesson by Kyuson Yun, directed by Artrake Studio.

Over the course of history, we’ve discovered hundreds of thousands of asteroids. But how do astronomers discover these bits of rock and metal? How many have they found? And how do they tell asteroids apart? Carrie Nugent shares the story of the very first asteroid ever discovered and explains how asteroid hunters search for these celestial bodies. Lesson by Carrie Nugent, directed by TED-Ed.

Imagine setting sail from Hawaii in a canoe. Your target is a small island thousands of kilometers away in the middle of the Pacific Ocean — a body of water that covers more than 160 million square kilometers. For thousands of years, Polynesian navigators managed voyages like this without the help of modern navigational aids. How did they do it? Alan Tamayose and Shantell De Silva explain.

The city has just opened its one-of-a-kind Faberge Egg Museum, with a single egg displayed on each floor of a 100-story building -- and the world’s most notorious jewel thief already has her eyes on the prize. Can you help the thief formulate a plan that will drop the most expensive egg she can get safely into her waiting truck? Yossi Elran shows how.

How good are you with money? What about reading people's emotions? How healthy are you, compared to other people you know? Knowing how our skills stack up against others is useful in many ways. But psychological research suggests that we're not very good at evaluating ourselves accurately. In fact, we frequently overestimate our own abilities. David Dunning describes the Dunning-Kruger effect. [Directed by Wednesday Studio, narrated by Addison Anderson, music by Tom Drew].

How good are you with money? What about reading people’s emotions? How healthy are you, compared to other people you know? Knowing how our skills stack up against others is useful in many ways. But psychological research suggests that we’re not very good at evaluating ourselves accurately. In fact, we frequently overestimate our own abilities. David Dunning describes the Dunning-Kruger effect.

Before the creation of humanity, the Greek gods won a great battle against a race of giants called the Titans. Most Titans were destroyed or driven to the eternal hell of Tartarus. But the Titan Prometheus, whose name means foresight, persuaded his brother Epimetheus to fight with him on the side of the Gods. Iseult Gillespie shares the myth of Prometheus.

Is it possible that overfishing, super germs, and global warming are all caused by the same thing? In 1968, a man named Garrett Hardin sat down to write an essay about overpopulation. Within it, he discovered a pattern of human behavior that explains some of history’s biggest problems. Nicholas Amendolare describes the tragedy of the commons.

The starving orphan seeking a second helping of gruel. The spinster wasting away in her tattered wedding dress. The stone-hearted miser plagued by the ghost of Christmas past. More than a century after his death, these remain recognizable figures from the work of Charles Dickens. But what are the features of Dickens’ writing that make it so special? Iseult Gillespie investigates. Lesson by Iseult Gillespie, directed by Compote Collective.