Salman Khan sent a video to his young cousin online, to help her with her math homework. A simple explanation, quickly sketched out. Then another and another, up on YouTube.
The next thing you know, a lot of other kids were paying attention. Using those math videos. Millions of kids. Including Bill Gates’s kids.
Now, Salman Khan is an education rock star, with videos up on math and chemistry and the Napoleonic Wars. Teachers are keying in. Classrooms. And it’s all free.