Don’t worry if you come up blank. You’re supposed to. The question is a gambit used by Anant Agarwal, the computer scientist named this year to head edX, a $60 million MIT-Harvard effort to stream a college education over the Web, free, to anyone who wants one. His point: it’s rare to see major technological advances in how people learn. Agarwal believes that education is about to change dramatically. The reason is the power of the Web and its associated data-crunching technologies. Thanks to these changes, it’s now possible to stream video classes with sophisticated interactive elements, and researchers can scoop up student data that could help them make teaching more effective. The technology is powerful, fairly cheap, and global in its reach…

Khan’s simple videos aren’t without their critics, who wonder whether his tutorials really teach math so well. “We agree 100 percent we aren’t going to solve education’s problems,” Khan responds. But he says the point to keep in mind is that technology-wise, “we’re in the top of the first inning.” He’ll be pouring about $10 million a year into making his videos better—already there are embedded exercises and analytics that let teachers track 50 or 100 students at once. Pretty soon, Khan told me, his free stuff “will be as good or better than anything anyone is charging money for.” Digital instruction faces limits. Online, you will never smell a burning resistor or get your hands wet in a biology lab. Yet the economics of distributing instruction over the Web are so favorable that they seem to threaten anyone building a campus or hiring teachers. At edX, Agarwal says, the same three-person team of a professor plus assistants that used to teach analog circuit design to 400 students at MIT now handles 10,000 online and could take a hundred times more…