Our understanding of how the earth works has just undergone its biggest change since we realized that the earth orbited the sun. We now know that what we see at the surface is caused by vigorous motions deep inside the earth—motions that are slow compared with our lifetimes, but are very fast compared with the life of the earth itself. Far from living on a dead lump of rock in space, we are living on jelly, but didn’t realize it! These programs trace the story of how and why our views changed—from a fumbling suspicion that continents had moved around, through a detailed reconstruction of how the pieces fit together, to the present, where we can measure the motions directly and see them going on. It is a story in which chasing a clue to one puzzle has often produced unexpected results and paradoxes. 5-part series, 60 minutes each.