Videos of her anatomy course, Integrative Biology 131, have been viewed nearly 1.5 million times on YouTube, where they have been available since 2005 to anyone with an Internet connection. Some of the world’s foremost scholars are up there for viewing, tuition free. From Yale, you can tune into an economics class by a professor with his own home-price index, Robert Shiller, or a course by the Milton scholar John Rogers. The undisputed rock star academic is Walter H. G. Lewin of the Massachusetts Institute of Technology, who flies across the room to demonstrate that a pendulum swings no faster or slower when there is an added mass (Professor Lewin) hanging at the end.