The world, we are told, is in the midst of a revolution. The new tools of social media have reinvented social activism. With Facebook and Twitter and the like, the traditional relationship between political authority and popular will has been upended, making it easier for the powerless to collaborate, coördinate, and give voice to their concerns.

Fifty years after one of the most extraordinary episodes of social upheaval in American history, we seem to have forgotten what activism is.G

The platforms of social media are built around weak ties. Twitter is a way of following (or being followed by) people you may never have met. Facebook is a tool for efficiently managing your acquaintances, for keeping up with the people you would not otherwise be able to stay in touch with.

For the last 15 years, to help schools with their nutrition curriculum, the University of North Carolina has offered a series of instruction modules free of charge. Initially delivered by CD-ROM and now online, the program, Nutrition in Medicine, is an interactive multimedia series of courses covering topics like the molecular mechanism of cancer nutrition, pediatric obesity, dietary supplements and nutrition in the elderly.

More recently, Ms. Adams and her colleagues have begun working on online nutrition education programs geared toward practicing physicians.

Electronic readers and textbooks, while an interesting concept and potentially lucrative for publishers, so far aren't meeting student needs

A host of research over the past decade has shown that even the option to click hyperlinks to related material can create confusion and weaken understanding.

The iPad measured at 6.2% lower reading speed than the printed book, whereas the Kindle measured at 10.7% slower than print