TED-Ed

What makes a tree grow tall? And do trees ever stop growing? Explore how photosynthesis and gravity can affect and limit the height of trees. --Reaching heights of over 100 meters, Californian sequoias tower over Earth’s other 60,000 tree species. But even these behemoths seem to have their limits: no sequoia on record has been able to grow taller than 130 meters. So what exactly is stopping these...

Dive into the Taino myth of the sea, and watch as Deminan and his brothers accidentally create a new world from a giant gourd. --Before the world of humans began, there was the world of the gods. Four brothers wandered this celestial realm. One day, the brothers snuck into a spirit’s house and spotted a giant gourd hanging in the corner. But as they tried to look inside the gourd, they dropped it....

Dig into the science of how new volcanoes form, and what causes their unpredictable eruptions. --In February of 1942, Mexican farmer Dionisio Pulido thought he heard thunder coming from his cornfield. However, the sound wasn’t coming from the sky. The source was a large, smoking crack emitting gas and ejecting rocks, and would come to be known as the volcano Paricutin. Where do new volcanoes like...

Discover how evolution and natural selection influence why the human body has vestigial organs— body parts that no longer serve their original purpose. --You know that little pink thing nestled in the corner of your eye? It’s actually the remnant of a third eyelid. In humans, it’s vestigial, meaning it no longer serves its original purpose. There are several other vestigial structures in the human...

View full lesson: http://ed.ted.com/lessons/tycho-brahe-the-scandalous-astronomer-dan-wenkelIf you think scientists lead boring, monotonous lives, you must not know about Tycho Brahe. The 16th century astronomer who accurately predicted planetary motion led quite a dramatic life -- complete with a kidnapping, a sword duel and even a clairvoyant dwarf. Dan Wenkel dives into the history behind this...

Discover the tale of the lovestruck boy sent into Hell to steal 3 hairs from the Devil to appease his true love's father, the king.--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....

View full lesson: http://ed.ted.com/lessons/the-chemical-reaction-that-feeds-the-world-daniel-d-dulekHow do we grow crops quickly enough to feed the Earth's billions? It's called the Haber process, which turns the nitrogen in the air into ammonia, easily converted in soil to the nitrate plants need to survive. Though it has increased food supply worldwide, the Haber process has also taken an unfor...

Dig into the Egyptian myth of Osiris, trapped by his brother, the warrior god Set, in a coffin and tossed into the Nile to die. --Long jealous of his older brother Osiris, the god who ruled all of Egypt, the warrior god Set plotted to overthrow him. Hosting an extravagant party as a ruse, Set announced a game— whoever could fit perfectly in a wooden chest could have it as a gift. But the chest was...

Dig into the mysterious Linear B symbols, found on ancient tablets on the island of Crete, which took scholars nearly 50 years to decode.--In the early 1900s, archaeologist Sir Arthur Evans uncovered nearly 3,000 tablets inscribed with strange symbols. He thought the script, dubbed Linear B, represented the Minoan language, while others came up with their own theories. Was it the lost language of...

A shooting star crashes onto Earth and unleashes a hideous, rampaging blob. Can you stop it from destroying the planet?--A shooting star crashes onto Earth and a hideous blob emerges. It creeps and leaps, it glides and slides. It’s also unstoppable: no matter what you throw at it, it just re-grows and continues its rampage. The only way to save the planet is to cut the entire blob into precise acu...

Trace the rise and fall of the ancient Celts, a group of hundreds of independent warrior tribes defeated by the Roman Empire. --One summer evening in 335 BCE, Alexander the Great was resting by the Danube River when a band of strangers approached his camp. Alexander had never seen anything like these tall, fierce-looking warriors with huge golden neck rings and colorful cloaks. They were Keltoi or...

View full lesson: http://ed.ted.com/lessons/the-operating-system-of-life-george-zaidan-and-charles-mortonHumans, octopi and pine trees alike are all made up of cells, tiny but sophisticated systems that keep life going. Cells are almost like tiny factories run by robots, with the nucleus, DNA, proteins, lipids, and vitamins and minerals all playing critical roles. George Zaidan and Charles Morton...

View full lesson: http://ed.ted.com/lessons/why-is-yawning-contagious-claudia-aguirre*Yaaawwwwwn* Did just reading the word make you feel like yawning yourself? Known as contagious yawning, the reasons behind this phenomenon have been attributed to both the physiological and psychological. It's been observed in children as young as four and even in dogs! Claudia Aguirre visits the many intriguing...

View full lesson: http://ed.ted.com/lessons/why-do-honeybees-love-hexagons-zack-patterson-and-andy-petersonHoneybees are some of nature's finest mathematicians. Not only can they calculate angles and comprehend the roundness of the earth, these smart insects build and live in one of the most mathematically efficient architectural designs around: the beehive. Zack Patterson and Andy Peterson delve...

View full lesson: http://ed.ted.com/lessons/ian-goldin-navigating-our-global-futureAs globalization and technological advances bring us hurtling towards a new integrated future, Ian Goldin warns that not all people may benefit equally. But, he says, if we can recognize this danger, we might yet realize the possibility of improved life for everyone. Ian Goldin is director of the 21st Century School...

Investigate the science behind how doctors use radioactive drugs and PET scans to detect and diagnose diseases like Alzheimer’s and cancer.--Is there a way to detect diseases like cancer and Alzheimer’s before they advance too far? Doctors are using injected radioactive drugs that circulate through the body and act as a beacon for PET scanners. These diagnostic tools can detect the spread of disea...

View full lesson: http://ed.ted.com/lessons/marcus-du-sautoy-symmetry-reality-s-riddleThe world turns on symmetry -- from the spin of subatomic particles to the dizzying beauty of an arabesque. But there's more to it than meets the eye. Here, Oxford mathematician Marcus du Sautoy offers a glimpse of the invisible numbers that marry all symmetrical objects. Oxford's newest science ambassador Marcus...

View full lesson: http://ed.ted.com/lessons/james-balog-time-lapse-proof-of-extreme-ice-lossPhotographer James Balog shares new image sequences from the Extreme Ice Survey, a network of time-lapse cameras recording glaciers receding at an alarming rate, some of the most vivid evidence yet of climate change. Talk by James Balog. Learn more about your ad choices. Visit megaphone.fm/adchoices

View full lesson: http://ed.ted.com/lessons/the-colossal-consequences-of-supervolcanoes-alex-gendlerIn 1816, Europe and North America were plagued by heavy rains, odd-colored snow, famines, strange fogs and very cold weather well into June. Though many people believed it to be the apocalypse, this "year without a summer" was actually the result of a supervolcano eruption that happened one year ear...

Dive into the Norse myth of how Loki tricked a stranger into building the great wall of Asgard to keep the realm safe from giants. --Asgard, a realm of wonders, was where the Norse Gods made their home. There Odin’s great hall of Valhalla towered above the mountains and Bifrost, the rainbow bridge, anchored itself. Though their domain was magnificent, it stood undefended from the giants and trolls...

Explore the science of why mixing drugs and drug interactions with other substances can lead to dangerous health complications.--Which of the following is risky behavior: a person taking cholesterol medicine with grapefruit juice? Or a person taking Acetaminophen before going out for drinks? Or a person on blood thinners who takes an aspirin? Turns out, all of them are risky. Each has inadvertentl...

View full lesson: http://ed.ted.com/lessons/madeleine-albright-on-being-a-woman-and-a-diplomatIn a frank and funny Q&A with Pat Mitchell from the Paley Center, former U.S. Secretary of State Madeleine Albright talks bluntly about politics and diplomacy, making the case that women's issues deserve a place at the center of foreign policy. Far from being a "soft" issue, she says, women's issues are o...

What is killing the Tasmanian devil? A virulent cancer is infecting them by the thousands -- and unlike most cancers, it's contagious. Researcher Elizabeth Murchison tells us how she's fighting to save the Taz, and what she's learning about all cancers from this unusual strain. Contains disturbing images of facial cancer. Talk by Elizabeth Murchison. Learn more about your ad choices. Visit megapho...

English novelist Jane Austen’s beloved works, like “Pride and Prejudice,” explored the dependence of women on marriage in British high society.--Whether she’s describing bickering families, quiet declarations of love, or juicy gossip, Jane Austen’s writing often feels as though it was written just for you. Her dry wit and cheeky playfulness informs her heroines, whose conversational tone welcomes...

View full lesson: http://ed.ted.com/lessons/the-fight-for-the-right-to-vote-in-the-united-states-nicki-beaman-griffinIn the United States today, if you are over eighteen, a citizen, and the resident of a state, you can vote (with some exceptions). So, how have voting rights changed since the first election in 1789? Nicki Beaman Griffin outlines the history of the long fight for a more inclusive el...