Democracy thrives on civil debate, Michael Sandel says -- but we're shamefully out of practice. He leads a fun refresher, with TEDsters sparring over a recent Supreme Court case (PGA Tour Inc. v. Martin) whose outcome reveals the...

Learn about the origin of Christmas trees which started in ancient European times and now is a primary tradition in cultures around the world that celebrate Christmas.

Lesson 12 (Conservation of Momentum) of Dianna's Intro Physics Class on Physics Girl. Never taken physics before? Want to learn the basics of physics? Need an AP Physics 1 review before the exam? This course is for you! Exercises in this...

Join young host Kristin as she introduces you to each letter of the alphabet and things that go from A to Z! Light-hearted, kid-friendly illustrations depict everything from an awesome airplane to a revved-up racecar, all while you're...