View full lesson here: http://ed.ted.com/lessons/what-creates-a-total-solar-eclipse-andy-cohen How can the shadow of the tiny moon eclipse the sight of the gargantuan sun? By sheer coincidence, the disc of the sun is 400x larger than the disc of the moon, but it's 390x farther from Earth -- which means that when they align just right, the moon blocks all but the sun's glowing corona. Andy Cohen details this extraordinary celestial phenomenon (and when it will next occur). Lesson by Andy Cohen