Xixi Wang

In 2025, our YouTube audience spent nearly 16 million hours watching TED-Ed Animations (that’s equal to over 1,800 years!). Our most-viewed videos of 2025 include an exploration of dragon legends from around the world, tips on how to best build new skills, an explanation of why it’s a really bad idea to mess with a crow, a handful to help you understand your body, and more!

Behold our top 10 most popular videos of 2025:

1. Do you really need to take 10,000 steps a day?

For years, Jean Béliveau walked from country to country, with the goal of circumnavigating the globe on foot. While few people have the time or desire to walk such extreme lengths, research shows that adding even a modest amount of walking to your daily routine can dramatically improve your health. So, what exactly happens to your body when you increase your step count? Shannon Odell investigates.

2. What happens to your brain without any social contact?

Everyone needs time to themselves, and peaceful solitude has stress-relieving benefits. But when being alone is forced upon you, the effects can be surprisingly extensive. And though different people experience distinct effects, symptoms tend to become more severe and persistent the longer one’s isolated. So, how exactly does isolation affect your body and brain? Terry Kupers investigates.

3. Why do so many cultures have dragon legends?

From the Chinese Loong to the Filipino Bakunawa, the Scottish Beithir and the Greek Hydra, dragons have inflamed imaginations for millennia. Their ubiquity across world mythology has led many scholars to ponder their possible origins. Could it be that tales of dragons were crafted to make sense of violent weather events? Timothy J. Burbery shares what geomythology has uncovered about dragons.

4. If you had the chance to be immortal, would you take it?

While cleaning out your uncle’s attic you find a chest with a sparkling potion. The attached tag declares drinking this liquid will make you immortal. Your body will be frozen at its current age, and these effects would be final and irreversible. The instructions are clear — the only question is, do you drink the potion? Sarah Stroud and Michael Vazquez explore this philosophical debate.

5. Can you “see” images in your mind? Some people can’t

When reading “Alice’s Adventures in Wonderland,” most readers visualize the queen’s croquet game play out in their heads. A few might see the scene in vivid detail. However, a small fraction of readers have a drastically different experience: within their heads, they “see” absolutely nothing. Why do some people have an inability to visualize images? Adam Zeman explores the science of aphantasia.

6. What actually causes high cholesterol?

In 1968, the American Heart Association made an announcement that would influence people’s diets for decades: they recommended that people avoid eating more than three eggs a week. Their reasoning was that the cholesterol packed into egg yolks could increase cardiovascular disease risk. So, what exactly is cholesterol? And is it actually bad for you? Hei Man Chan digs into this complex molecule.

7. The best way to become good at something might surprise you

There’s a common idea that it takes 10,000 hours of practice to become great at something. From an early age, we are encouraged to choose our path, focus specifically, and start racking up those hours. But, what if these head starts aren’t helping us the way we think they do? What if there’s a better way to excel? David Epstein shares how a different approach could set us up for greater success.

8. What’s the best way to lift people out of poverty?

In 2018, a nonprofit gave every adult in the Ahenyo village $500. Most families had lived in extreme poverty for generations, and this sum was roughly equivalent to their annual salaries. The money came with no strings attached to how it could be spent. Would this lift villagers out of poverty or be another failed philanthropic endeavor? Explore aid programs and how they address people’s needs.

9. How smart are crows?

In one of Aesop’s fables, a crow is searching for water. It spies a pitcher— but the water inside is beyond its reach. So, the crow begins dropping in pebbles. One-by-one, they displace the water, and the crow quenches its thirst. This is just one of many fascinating displays of intelligence from corvids. Katharina Brecht digs into what makes this bold, brainy family of songbirds so smart.

10. Why don’t we get our drinking water from the ocean?

Xixi Wang

TED-Ed is excited to announce that our award-winning animations are now be available in German, Hindi, Japanese, Mandarin, Spanish, Arabic, French, Hebrew, Swahili, Portuguese, and Thai via new YouTube channels!

TED-Ed’s mission is to spark curiosity and spread lessons worth sharing to students, educators and life-long learners around the world. In an effort to make our animated shorts more widely accessible, TED-Ed has partnered with talented voice actors and translators around the world to publish professionally dubbed animated shorts on a weekly basis.

Subscribe to our new YouTube channels today:

German: TED-Ed Deutsch

Hindi: TED-Ed हिन्दी

Japanese: TED-Ed 日本

Mandarin: TED-Ed 中文

Spanish: TED-Ed Español

Arabic: TED-Ed اللغةالعربية

French: TED-Ed Français

Hebrew: TED-Ed בעברית

Swahili: TED-Ed Kiswahili

Portuguese: TED-Ed Português

Thai: TED-Ed ภาษาไทย

If you know a curious language-learner or speaker of one of these languages, share this blog post with them to spread the word!

Xixi Wang

In 2022, our YouTube audience spent nearly 24 million hours watching TED-Ed Animations (that’s equal to over 2,700 years!). Our most-viewed videos of 2022 include an eye-opening glimpse into the diverse world of animal pupils, a bring-your-son-to-work day gone terribly, tragically wrong, the surprising electrical powers of sausage, one to help you understand why you procrastinate (even though you know you shouldn’t), and more.

Behold our top 10 most popular videos of 2022:

1. Why is it so hard to escape poverty?

Imagine that you’ve been unemployed for months. Government benefit programs have helped you cover your expenses, but you’re barely getting by. Finally, you receive a paycheck— but there’s a catch. Your new job pays enough to disqualify you from benefit programs, but not enough to cover your costs. So how do we design benefit programs that don’t penalize you for working? Ann-Helén Bay investigates.

2. Why do cats have vertical pupils?

Peering into the eyes of different animals, you’ll see some extraordinarily shaped pupils. House cats, for one, are twilight hunters with vertically elongated pupils. Many grazing animals, like goats, have rectangular pupils. Other animals have crescent- or heart-shaped pupils. So, what’s going on? Why are there so many different pupil shapes? Emma Bryce digs into the science of animal vision.

3. Why you procrastinate even when it feels bad

The report you’ve been putting off is due tomorrow. It’s time to buckle down, open your computer … and check your phone. Maybe watch your favorite YouTube channel? Or maybe you should just start in the morning? This is the cycle of procrastination. So, why do we procrastinate when we know it’s bad for us? Explore how your body triggers a procrastination response, and how you can break the cycle.

4. How does heart transplant surgery work?

Your heart beats more than 100,000 times a day. In just a minute, it pumps over five liters of blood throughout your body. But unlike skin and bones, the heart has a limited ability to repair itself. So if this organ is severely damaged, there’s often only one medical solution: replacing it. Roni Shanoada explores how this complex and intricate procedure works.

5. Why are cockroaches so hard to kill?

In ancient Egypt, there was a spell that declared, “Be far from me, O vile cockroach.” Thousands of years later, we’re still trying to oust these insects. But from poison traps to brandished slippers, cockroaches seem to weather just about everything we throw at them. So, what makes cockroaches so hard to kill? Ameya Gondhalekar digs into the genetic wonders of this troublingly tenacious creature.

6. Why is the Mona Lisa so famous?

More than 500 years after its creation, Leonardo da Vinci’s “Mona Lisa” is arguably the world’s most famous painting. Many scholars consider it an outstanding work of Renaissance art— but history is full of great paintings. So, how did this particular portrait skyrocket to unprecedented fame? Noah Charney explores the factors that helped create a worldwide sensation.

7. The tragic myth of the Sun God’s son

Every morning, Helios unleashed his golden chariot, and set out across the sky. As the Sun God transformed dawn into day, he thought of his son, Phaethon, below. To prove to Phaethon that he was truly his father, Helios decided to grant him anything he wanted. Unfortunately, what Phaethon wanted was to drive Helios’ chariot for a day. Iseult Gillespie shares the tragic myth of the charioteer.

8. The myth of Hades and Persephone

One day, Persephone was frolicking in a meadow with the nymph, Cyane. As they admired a flower, they noticed it tremble in the ground. Suddenly, the earth split, and a terrifying figure arose. It was Hades, god of the underworld. He wrenched Persephone from Cyane, dragged her into his inky chariot, and blasted back through the earth. Iseult Gillespie shares the myth of the goddess of spring.

9. Why a sausage does what your gloves cannot

In 2010, South Korea experienced a particularly cold winter. People couldn’t activate their smartphones while wearing gloves, so they began wielding snack sausages— causing one company to see a 40% rise in sausage sales. So, what could sausages do that gloves couldn’t? In other words, how do touchscreens actually work? Charles Wallace and Sajan Saini dig into the science of touchscreens.

10. What is the rarest color in nature?

Plants, animals, or minerals found in nature bear almost every color imaginable. There are two factors that influence what hues you see in the wild: physics and evolution. So, which colors are you least likely to see in the natural world? Victoria Hwang explores one of nature’s rarest spectacles.

On behalf of everyone here at TED-Ed, thanks for learning with us this year!

To get brand new TED-Ed Animations delivered to your inbox for free in 2023, sign up for the TED-Ed weekly newsletter here >>

Check out our most popular Animations for 2021, 2020, 2019, and 2018.

Elise Haadsma

This year, TED-Ed is celebrating a big milestone: our tenth birthday!

When we published our first batch of videos on March 12, 2012, we didn’t know what TED-Ed’s future might hold. Now, we’re looking back on a decade of curiosity, asking and exploring answers to life’s big questions, and meeting one of the most inquisitive and supportive communities on the internet – that’s you! 1,400 videos and 3 billion views later, you’ve spent a whopping 166 million hours— almost 20,000 years— learning on our YouTube channel alone.

To celebrate the occasion, we’re sharing ten of our most-viewed videos— one published in each year that we’ve been around.

2012: Questions no one knows the answer to

Published in our channel’s first week, this video—written and narrated by TED Curator Chris Anderson—explores Chris’s boyhood obsession with quirky questions that seem to have no answers. At 12 minutes, it’s a bit longer than the traditional TED-Ed format, but Chris’s contemplative narration will keep you captivated throughout. (Also: Peep the original TED-Ed intro. Super cool. Also super long. We ended up shortening it in 2013 and again in 2017.)

2013: The loathsome, lethal mosquito

The world’s most-hated bug stars in our top-viewed video from 2013. Because, let’s face it: everyone hates mosquitoes. Besides the annoying buzzing and biting, mosquito-borne diseases like malaria kill over a million people each year. So shouldn’t we just get rid of them? Rose Eveleth shares why scientists aren’t sure over a colorful (and itch-inducing) animation.

2014: The Infinite Hotel Paradox

Over 20 million viewers have grappled with the concept of infinity since we first published this brain-bending video in 2014. The Infinite Hotel, a thought experiment created by German mathematician David Hilbert, is a hotel with an infinite number of rooms. But what if it’s completely booked and one person wants to check in? What about 40? Or an infinitely full bus of people? Jeff Dekofsky navigates this heady hotel using Hilbert’s paradox.

2015: Can you solve the prisoner hat riddle?

2015 was (for TED-Ed at least) the year of the riddle. We published our first (Can you solve the bridge riddle?) in September, and were blown away by its reception. Of the 60+ riddles we’ve shared since, the Prisoner Hat Riddle (published a month later in October 2015) still takes the gold for most-viewed. Can you solve it? If you’re stumped, don’t worry: Alex Gendler will show you how.

2016: What would happen if you didn’t drink water?

Hydration was clearly on people’s minds in 2016. And why not? Water is pretty important—it’s essentially everywhere in our world, and the average human is composed of between 55 and 60% of it. Mia Nacamulli details the role water plays in our bodies, and how much we actually need to drink to stay healthy in this ode to hydration.

2017: Why don’t perpetual motion machines ever work?

Perpetual motion machines — devices that can do work indefinitely without any external energy source — have captured many inventors’ imaginations (and clearly many viewers’ 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 in this beautifully animated piece from 2017.

2018: Which is stronger: Glue or tape?

You might not expect a video about adhesives to have made our top 10, but over 12 million people tuned in to watch glue and tape spar it out in this 2018 battle of the bonds. Elizabeth Cox explains what gives glue and tape their stickiness, and whether one is stronger than the other in this video that will have you stuck to your screen. (PS. Did you notice the TED-Ed intro change again? We started incorporating quotes into our intros in August 2017 and never looked back.)

2019: How Thor got his hammer

Our animated retellings of myths are always crowd favorites, and none resonated more in 2019 than this tribute to the Norse god of thunder. In this clever and comical video, Scott A. Mellor traces the legend of Thor’s hammer, and how Loki the mischief-maker’s cunning and deceit played into its creation.

2020: How does alcohol make you drunk?

While we’re a little concerned that our most viewed video in 2020 was about alcohol, the pursuit of information is something we can always get behind. Judy Grisel explores alcohol’s journey through the body, how exactly it causes drunkenness, and why it has dramatically different effects on different people in this pandemic blockbuster.

2021: What causes dandruff and how do you get rid of it?

2021′s top performer is a real head-scratcher. On top of our heads, there is a type of yeast that lives and dines on all of our scalps. Feasting constantly, it’s in paradise. And in about half of the human population, its activity causes dandruff. So, why do some people have more dandruff than others? And how can it be treated? Thomas L. Dawson explores this problem in our top-viewed video from last year.

Thanks so much for sticking with us this past decade— for the obvious things like watching, liking, and subscribing, and for the not-so-obvious things like giving us video ideas, making us laugh in the comment sections, and more. We can’t wait to see what the next decade brings.

And, while we’re feeling emotional, we thought it would be nice to round this out with a quote from that first video on the list, “Questions no one knows the answer to.” We think it sums up the past, present and future of TED-Ed quite well:

“The quest for knowledge and understanding never gets dull. It doesn’t. It’s actually the opposite. The more you know, the more amazing the world seems. And it’s the crazy possibilities, the unanswered questions that pull us forward. So stay curious.”

Elise Haadsma

In 2021, our YouTube audience spent over 36 million hours watching TED-Ed Animations (that’s equal to over 4,100 years!). Our most-viewed videos of 2021 include a self-healing, cannibalistic salamander, a pair of star-crossed lovers, a handful to help you understand your body, an epic journey to the end of the world, and more.

Behold our top 10 most popular videos of 2021:

1. What causes dandruff, and how do you get rid of it?

On top of our heads, there is a type of yeast that lives and dines on all of our scalps. Feasting constantly, it’s in paradise. And in about half of the human population, its activity causes dandruff. So, why do some people have more dandruff than others? And how can it be treated? Thomas L. Dawson explores this head-scratching problem.

2. Why do we have hair in such random places?

We have lots in common with our closest primate relatives. But comparatively, humans seem a bit… underdressed. Instead of thick fur covering our bodies, many of us mainly have hair on top of our heads— and a few other places. So, how did we get so naked? And why do we have hair where we do? Nina G. Jablonski explores the evolution of human hair.

3. Savitri and Satyavan: The legend of the princess who outwitted Death

Princess Savitri was benevolent, brilliant, and bright. Her grace was known throughout the land, and many princes and merchants flocked to her family’s palace to seek her hand in marriage. But upon witnessing her blinding splendor in person, the men lost their nerve. Unimpressed with these suitors, she determined to find a husband herself. Iseult Gillespie tells the tale of Savitri and Satyavan.

4. How long should your naps be?

Your eyes get heavy and gradually close… But wait! It’s only lunch time and you still have so much to do. Would taking a nap help? Or would it derail your day? Well, that depends on a few things— especially what stages of sleep the nap includes. Sara C. Mednick details the cognitive benefits of napping, and explores the optimal length and time of day for a quick snooze.

5. Axolotls: The salamanders that snack on each other (but don’t die)

Axolotls are one of science’s most studied animals. Why, you ask? These extraordinary salamanders are masters of regeneration: they can flawlessly regenerate body parts ranging from amputated limbs and crushed spines to parts of their eyes and brains. So, how do they do it? And what other secrets are they keeping? Luis Zambrano explores the baffling biology of the axolotl.

6. What happens to your brain during a migraine?

A throbbing, pounding headache. Bright zigzagging lines across your field of vision. Sensitivity to light, lingering fatigue, disrupted sleep. While an incapacitating headache is one of the most common symptoms, a migraine can include any of these experiences. So what exactly is a migraine? And what causes it? Marianne Schwarz explores what we know— and don’t know— about this complex disorder.

7. Why don’t we cover the desert in solar panels?

Stretching over roughly nine million square kilometers and with sands reaching temperatures of up to 80° Celsius, the Sahara Desert receives about 22 million terawatt hours of energy from the Sun every year. That’s well over 100 times more energy than humanity consumes annually. So, could covering the desert with solar panels solve our energy problems? Dan Kwartler digs into the possibility.

8. The epic of Gilgamesh, the king who tried to conquer death

In 1849, in the ancient city of Nineveh in Iraq, archaeologists sifted through dusty remains, hoping to find records to prove that Bible stories were true. What they found instead was a 4,000-year-old story inscribed on crumbling clay tablets— a story that was so riveting, the first person to translate it started stripping from excitement. Soraya Field Fiorio tells the epic tale of Gilgamesh.

9. The Norse myth that inspired “The Lord of the Rings”

The dwarves were master craftspeople. One dwarf, Andvari, forged marvelous creations. He often took the form of a fish and, one day, he swam to the land of the water nymphs, who guarded mounds of gold. When the nymphs laughed at his appearance, Andvari grew infuriated and seized their gold. With it, he crafted himself a special ring. Iseult Gillespie shares the Norse myth of the cursed ring.

10. You could have a secret twin (but not the way you think)

While searching for a kidney donor, Karen Keegan stumbled upon a mystery. After undergoing genetic testing, it turned out that some of her cells had a completely different set of genes from the others. And this second set of genes belonged to her twin sister— who had never been born. How did this happen? Kayla Mandel Sheets explores the condition known as chimerism.

On behalf of everyone here at TED-Ed, thanks for learning with us this year!

To get brand new TED-Ed Animations delivered to your inbox for free in 2022, sign up for the TED-Ed weekly newsletter here >>

Check out our most popular Animations for 2020, 2019, and 2018.

Alexandra Panzer

In 2020, our YouTube audience spent nearly 32 million hours watching TED-Ed Animations (that’s equal to over 3,600 years!). Our most-viewed videos of 2020 include a couple of lovestruck tricksters, a self-cloning candy-pooping bug, a mysterious mathematician, a handful to help understand pandemics, and more.

Behold our top 10 most popular videos of 2020:

1. When is a pandemic over?

Consider the following scenario: a highly infectious, sometimes deadly respiratory virus infects humans for the first time. It spreads rapidly worldwide, and the WHO declares a pandemic. The death toll starts to rise and everyone is asking the same question: when will the pandemic end? Alex Rosenthal details the three main strategies governments can use to contain and end a pandemic.

2. The tale of the doctor who defied Death

A husband and wife were in despair. The woman had just given birth to their 13th child, and the growing family was quickly running out of food and money. Wandering into the woods, the father encountered a skeletal figure with sunken eyes and a gaunt face: this was Death himself, come to offer his services as Godfather. Iseult Gillespie tells the tale of Death and the doctor.

3. How does alcohol make you drunk?

Ethanol: this molecule, made of little more than a few carbon atoms, is responsible for drunkenness. Often simply referred to as alcohol, ethanol is the active ingredient in alcoholic beverages. So how exactly does it cause drunkenness, and why does it have dramatically different effects on different people? Judy Grisel explores alcohol’s journey through the body.

4. The bug that poops candy

Aphids can reproduce incredibly fast: they can make 20 new generations within a single season. And that means lots of poop. Some aphid populations can produce hundreds of kilograms of poop per acre— making them some of the most prolific poopers on the planet. We know this poop as the sweet, syrupy liquid called honeydew. George Zaidan explores the wonderfully weird life of an aphid.

5. What really happened during the Salem Witch Trials

You’ve been accused of a crime you did not commit. It’s impossible to prove your innocence. If you insist that you’re innocent anyway, you’ll likely be found guilty and executed. But if you confess, apologize, and implicate others, you’ll go free. This was the choice facing those accused of witchcraft in Salem, Massachusetts in the 17th century. How did this happen? Brian A. Pavlac investigates.

6. The tale of the boy who tricked the Devil

In a small town, a proud mother showed off her newborn son. Upon noticing his lucky birthmark, townsfolk predicted he would marry a princess. But soon, these rumors reached the wicked king. Enraged, the king stole the child away, and sent him hurtling down the river. But the infant’s luck proved greater than the king’s plan. Iseult Gillespie tells the tale of the boy’s journey to meet the Devil.

7. How fast can a vaccine be made?

When a new pathogen emerges, our bodies and healthcare systems are left vulnerable. And when this pathogen causes the outbreak of a pandemic, there’s an urgent need for a vaccine to create widespread immunity with minimal loss of life. So how quickly can we develop vaccines when we need them most? Dan Kwartler describes the three phases of vaccine development.

8. What’s that ringing in your ears?

Tinnitus has been bothering humanity since Ancient Babylon, plaguing everyone from Leonardo da Vinci to Charles Darwin. Today, roughly one in seven people worldwide experiences this auditory sensation. So what exactly is tinnitus, and where does this persistent sound come from? Marc Fagelson travels into the auditory system to explore the loss of silence.

9. The greatest mathematician that never lived

When Nicolas Bourbaki applied to the American Mathematical Society in the 1950s, he was already one of the most influential mathematicians of his time. He’d published articles in international journals and his textbooks were required reading. Yet his application was firmly rejected for one simple reason: Nicolas Bourbaki did not exist. How is that possible? Pratik Aghor digs into the mystery.

10. Can you solve the Ragnarok riddle?

Ragnarok: The fabled end of the world, when giants, monsters, and Norse gods battle for the future. The gods were winning until the great serpent Jörmungandr emerged. It swallowed Valhalla and contorted itself across the land. Odin has just enough power to strike with one final bolt of lightning, and you have the fabled hammer, Mjölnir. Can you two destroy the serpent? Dan Finkel shows how.

On behalf of everyone here at TED-Ed, thanks for learning with us this year!

To get brand new TED-Ed Animations delivered to your inbox for free in 2021, sign up for the TED-Ed weekly newsletter here >>

Elise Haadsma

In 2019, our YouTube audience spent over 23 million hours watching TED-Ed Animations (that’s equal to over 2,600 years!). Our most-viewed videos of 2019 include a couple of monumental myths, a radical and rebellious nun, an infamous personality test, and more.

Behold our top 10 most popular videos of 2019:

1. The history of the world according to cats

In ancient times, wildcats were fierce carnivorous hunters. And unlike dogs, who have undergone centuries of selective breeding, modern cats are genetically very similar to ancient cats. How did these solitary, fierce predators become our sofa sidekicks? Eva-Maria Geigl traces the domestication of the modern house cat. Watch this TED-Ed Animation below.

2. History’s “worst” nun

Juana Ramírez de Asbaje sat before a panel of prestigious theologians, jurists, and mathematicians. They had been invited to test Juana’s knowledge with the most difficult questions they could muster. But she successfully answered every challenge, from complicated equations to philosophical queries. Who was this impressive woman? Theresa Yugar details the life of the Mexican poet and scholar. Watch this TED-Ed Animation below.

3. The surprising reason our muscles get tired

You’re lifting weights. The first time feels easy, but each lift takes more and more effort until you can’t continue. Inside your arms, the muscles responsible for the lifting have become unable to contract. What’s going on? Christian Moro explains how exactly our muscles operate, and what causes them to become fatigued. Watch this TED-Ed Animation below.

4. How to spot a pyramid scheme

In 2004, a nutrition company offered a life-changing opportunity to earn a full-time income for part-time work. There were only two steps to get started: purchase a $500 kit and recruit two more members. By 2013, the company was making $200 million. There was just one problem — the vast majority of members earned less than they paid in. Stacie Bosley explains what a pyramid scheme is and how to spot one. Watch this TED-Ed Animation below.

5. A brief history of cannibalism

15th century Europeans believed they had hit upon a miracle cure: a remedy for epilepsy, hemorrhage, bruising, nausea and virtually any other medical ailment. It was a brown powder known as “mumia,” and was made by grinding up mummified human flesh. But just how common is human cannibalism, and how do cultures partake in it? Bill Schutt explores the complex history of cannibalism. Watch this TED-Ed Animation below.

6. Ancient Rome’s most notorious doctor

In the 16th century, an anatomist named Andreas Vesalius made a shocking discovery: the most famous human anatomy texts in the world were wrong. While Vesalius knew he was right, announcing the errors would mean challenging Galen of Pergamon. Who was this towering figure? And why was he still revered and feared 1,300 years later? Ramon Glazov profiles the most renowned physician in medical history. Watch this TED-Ed Animation below.

7. The myth of Pandora’s box

Pandora was the first mortal woman, breathed into being by Hephaestus, god of fire. The gods gave her gifts of language, craftsmanship and emotion. From Zeus she received two gifts: the trait of curiosity and a heavy box screwed tightly shut — never to be opened. But what treasure could never be seen by human eyes, and why was it in her care? Iseult Gillespie explores the mystery of Pandora’s box. Watch this TED-Ed Animation below.

8. How Thor got his hammer

Loki the mischief-maker, writhes in Thor’s iron grip. The previous night, he’d snuck up on Thor’s wife and shorn off her beautiful hair. To fix what he’d done, Loki rushes to the dwarves and tricks them into making gifts for the gods. Wanting to best their smith rivals, the dwarves make a set of golden treasures, including a hammer called Mjolnir. Scott A. Mellor traces the legend of Thor’s hammer. Watch this TED-Ed Animation below.

9. How does the Rorschach inkblot test work?

For nearly a century, ten inkblots have been used as an almost mystical personality test. Long kept confidential for psychologists and their patients, the mysterious images were said to draw out the workings of a person’s mind. But what can inkblots really tell us, and how does this test work? Damion Searls details how the Rorschach Test can help us understand the patterns of our perceptions. Watch this TED-Ed Animation below.

10. Einstein’s twin paradox explained

On their 20th birthday, identical twin astronauts volunteer for an experiment. Terra will remain on Earth, while Stella will board a spaceship. Stella’s ship will travel to visit a star that is 10 light-years away, then return to Earth. As they prepare to part ways, the twins wonder what will happen when they’re reunited. Who will be older? Amber Stuver investigates the “Twin Paradox.” Watch this TED-Ed Animation below.

On behalf of everyone here at TED-Ed, thanks for learning with us this year!

To get brand new TED-Ed Animations delivered to your inbox for free in 2020, sign up for the TED-Ed weekly newsletter here >>

In honor of our lesson on Anna Komnene —a Byzantine princess, scholar, physician and historian — we asked animator Els Decaluwe a few questions about the process of working on this piece.

What are the challenges of designing a character that you have no photographs of, only other artist’s interpretations?

Before I start designing, I always try to look up some background information about the character. In Anna’s case, I got the feeling that she was really ahead of her time. I really wanted to give my design the same aura without trying to copy other artists’ designs. It’s not about how she looks but about what she represents and who she was! For the hair I looked up several historical references and also got lots of help from educator Leonora Neville. I saw lovely complicated up-dos with jewels and decorations between braids. But I felt Anna was kind of a free spirit so she maybe would have worn her hair in a looser style. Not wearing too much jewelry, as it would get in the way of her writing. As for the clothes, I thought Anna should be ”a badass in a dress.”

What techniques do you use in your process?

I’m a real big fan of classical 2D animation, and if I could, I would still make everything on paper. Because of time constraints, though, I traditionally only do the pre-production. Afterwards I digitally try to copy the feel of my traditionally-drawn images. Textures are my best friends and I spend a lot of time preparing traditional textures, to use in the digital coloring process. For the animation itself, I use a frame by frame animation technique. This means that I redraw every frame, so I make approximately 12 drawings per second of film. This is a time-consuming process that gives extra movement and charm to the animation, and to me it is totally worth it!

Which part of this animation are you most happy about?

The scene transitions were really important to me. Though it is a historical realistic subject, I wanted to add some magic to them. That’s why I chose to use transformations in my animations. Anna turning into the year 1083 and than baby Anna coming out of the 0 was my greatest challenge. Animating transformations is like performing a magic trick: when they work well, it really puts a smile on peoples’ faces! I also love the scene where Anna was reading at night. As I am also a children’s book illustrator, I like putting in the extra time to really design a picture book-like illustration with lots of details and textures.

Spending so much time working on the depiction of one character, do you develop any sort of relationship to that character? Do you have any good anecdotes about getting to know Anna Komnene as a character in order to design her and bring her to life?

It was lovely learning more about this heroine. What really struck me was the information I found about people questioning the fact that The Alexiad, her account of her father’s reign, could have been written by a woman. I realised how important it was for me to represent her correctly. That’s also why I chose to mirror Anna and her father in the first and last scene. I wanted to show how many women also have an important role in history. And you can make a difference without using a sword! While animating Anna and Alexios, I used a mirror and acted out their movements and facial expressions. I had a ruler which I used as a sword and hopped around in the office. My co-workers even caught me making funny/crazy facial expressions while animating! That’s why I think there’s also a bit of me in the animation of Anna.

Our process at TED-Ed involves several steps to make sure the content we present is factually accurate. First, the authors of lessons are educators and subject matter experts. Second, we have a team of fact-checkers who review our content and flag anything that needs review. Unfortunately, there are times when we still make mistakes! That was the case with a lesson we recently published (“How do computers find websites so quickly”).

Our community was extremely helpful and proactive in identifying an error, and after further research and verification, we took the video down. We see mistakes as great learning moments, and the author of the lesson, Chand John, was kind enough to explain what went wrong. (Read his letter below.) The main content of this lesson — explaining how hash tables work and why they’re important — is something we see as valuable in and out of the classroom, and Chand is an excellent educator and communicator. So we’ll be working with him to create a new version that will come at the content from a different direction. Every video we produce takes several months to make, because our script-writing and animation-creating processes both require a lot of time and attention; please stay tuned for a new, corrected version of this video later in the year!

Below, read Chand John’s letter:

When you use the Internet, many different processes and entities are involved: domain name servers, routing protocols, and much more. In an attempt to create a lesson about hash tables in the context of Internet communication, I chose to base the lesson on a very widely available hash table, called the Linux routing cache. Here are a couple of nice descriptions of the routing cache:

http://linux-ip.net/html/routing-cache.html
https://www.cs.unh.edu/cnrg/people/gherrin/linux-net.html#tth_sEc8.2.3

There was a key mistake in how this was introduced in the lesson, however: the Linux routing cache, which contains IP addresses and related information, existed on many devices, but in conducting research for this piece, I misunderstood the context in which the routing cache is typically used.

We introduced the routing cache (which we called a “routing table” in the video, since it was one of multiple routing-related tables available on many computers) in the context of typical Web browsing. However, what the video describes is more like what a router itself can do during typical Internet use, if it happens to use this type of hash table, and *not* what your own computer typically does when you access the Internet (unless, perhaps, you configured it to act like a router itself).

In short, while the routing cache described in the video has *existed* on a very wide array of devices, it is not necessarily *used* on most of those devices for the purpose suggested in the original video.

While we tried *not* to make this lesson describe all aspects of Internet communication (our goal was to focus on one particular aspect of it involving a widely available hash table), the earlier parts of the video make it sound like this hash table is something your devices do every time you use the Internet, which is inaccurate. My big concern after realizing my mistake is that viewers not misunderstand how typical Internet communication works.

We instructors make mistakes sometimes, and sometimes we like to turn these into valuable lessons of their own: in subjects like computer science, where really tiny details can make a huge difference in whether something works or not, or whether a statement is correct or not, the important thing is to be open to feedback, to understand that we will make mistakes, to learn from those mistakes, and to share that knowledge. This is why computer programmers often review each other’s work, why many publications have editors, and why academic research papers go through detailed peer review.

When challenging yourself by learning and doing new things, you will make mistakes, experience failure, and feel discouraged at times. It is how you handle these moments that most influences whether you will continue to progress in your learning. So, those times of failure are your best opportunities to prove to yourself that you can keep going, and to see those moments not as barriers that stop your progress, but rather as stepping stones from which you can propel both yourself and others to new heights. It helps to know that you’re not alone: even the world’s most famous, successful people make mistakes. Chances are, they have made more mistakes than most people, because many of them took on difficult challenges that others avoided.

There’s a big difference between *striving* to be correct 100% of the time, and *expecting* oneself to be right all the time. Mistakes can have consequences, but if you’re willing to learn from them, chances are you will continue to progress in your learning. The biggest barrier I’ve seen to people’s progress is not being wrong at times; it’s the expectation that the point of learning is to be right all the time, and then avoiding new challenges due to an exaggerated fear of failure. And it’s important to support each other when we do encounter new challenges: that’s why we educators and TED-Ed do what we do, to support and encourage our viewers to take on new educational challenges in a fun and inspiring way.

Our top priority is to ensure that educators and students receive accurate information, and I do apologize to all viewers who may have been misinformed about the mechanics of typical Internet communication. I thank everyone who has contributed to the discussion on this video, as well as the amazing team — animators, narrator, editors, and the whole TED-Ed team — who have worked so hard on putting this together. It is a real privilege to continue to work with them on creating these beautifully illustrated lessons for the benefit of viewers worldwide.

— Chand

TED-Ed Originals are short, award-winning animated videos about ideas. Three times a week, you can watch a brand new TED-Ed Original designed to spark your curiosity. Ready to catch up on the latest riddles? In a binge-watching mood? Start with this list of the top 10 most popular TED-Ed Originals released in 2016:

1. Can you solve the temple riddle?

Your expedition finally stands at the heart of the ancient temple. But as you study the inscriptions in the darkness, two wisps of green smoke burst forth. The walls begin to shake. The giant sandglass begins flowing with less than an hour before it empties, and a rumbling tells you that you don’t want to be around when that happens. Can you use math to escape the temple? Dennis E. Shasha shows how. Watch this TED-Ed Original below.

2. Can you solve the locker riddle?

Your rich, eccentric uncle just passed away, and you and your 99 nasty relatives have been invited to the reading of his will. He wanted to leave all of his money to you, but he knew that if he did, your relatives would pester you forever. Can you solve the riddle he left for you and get the inheritance? Lisa Winer shows how. Watch this TED-Ed Original below.

3. Can you solve the frog riddle?

You’re stranded in a rainforest, and you’ve eaten a poisonous mushroom. To save your life, you need an antidote excreted by a certain species of frog. Unfortunately, only the female frog produces the antidote. The male and female look identical, but the male frog has a distinctive croak. Derek Abbott shows how to use conditional probability to make sure you lick the right frog and get out alive. Watch this TED-Ed Original below.

4. Can you solve the passcode riddle?

In a dystopian world, your resistance group is humanity’s last hope. Unfortunately, you’ve all been captured by the tyrannical rulers and brought to the ancient coliseum for their deadly entertainment. Will you be able to solve the passcode riddle and get everyone out safely? Ganesh Pai shows how. Watch this TED-Ed Original below.

5. What would happen if you didn’t drink water?

Water is essentially everywhere in our world, and the average human is composed of between 55 and 60% water. So what role does water play in our bodies, and how much do we actually need to drink to stay healthy? Mia Nacamulli details the health benefits of hydration. Watch this TED-Ed Original below.

6. Can you solve the prisoner boxes riddle?

Your favorite band is great at playing music…but not so great at being organized. They keep misplacing their instruments on tour, and it’s driving their manager mad. Can you solve the brain-numbing riddle their manager assigns them and make sure the band stays on their label? Yossi Elran shows how. Watch this TED-Ed Original below.

7. Why do cats act so weird?

They’re cute, they’re lovable, and judging by the 26 billion views on over 2 million YouTube videos of them, one thing is certain: cats are very entertaining. But their strange feline behaviors, both amusing and baffling, leave many of us asking: Why do cats do that? Tony Buffington explains the science behind some of your cat’s strangest behaviors. Watch this TED-Ed Original below.

8. The psychology of narcissism

Narcissism isn’t just a personality type that shows up in advice columns; it’s actually a set of traits classified and studied by psychologists. But what causes it? And can narcissists improve on their negative traits? W. Keith Campbell describes the psychology behind the elevated and sometimes detrimental self-involvement of narcissists. Watch this TED-Ed Original below.

9. Can you solve the control room riddle?

As your country’s top spy, you must infiltrate the headquarters of the evil syndicate, find the secret control panel, and deactivate their death ray. But your reconnaissance team is spotty, and you have only limited information about the control panel’s whereabouts. Can you solve the control room riddle and deactivate their weapon in time? Dennis Shasha shows you how. Watch this TED-Ed Original below.

10. How did Hitler rise to power?

Decades after the fall of the Third Reich, it feels impossible to understand how Adolf Hitler, the tyrant who orchestrated one of the largest genocides in human history, could ever have risen to power in a democratic country. So how did it happen, and could it happen again? Alex Gendler and Anthony Hazard dive into the history and circumstances that allowed Hitler to become Führer of Germany. Watch this TED-Ed Original below.

On behalf of everyone here at TED-Ed, thanks for learning with us this year!

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