Left; Steve Jurvetson: Time Life Pictures / Getty Images Salman Khan, left, of Kahn Academy, and Andrew Carnegie

Meet Salman Khan, your child’s new teacher. If you haven’t heard of Khan, rest assured that your son or daughter is in good hands. He has four degrees from the Massachusetts Institute of Technology (MIT) and Harvard. He got a perfect score on the math portion of his SAT. And he’s very experienced, having taught more than 85 million lessons to students all over the world.

Khan is the former hedge fund manager who set out to tutor his young cousin in math with a homemade video he posted online. From that modest beginning has grown the Khan Academy, a free online library of more than 2,700 videos offering instruction in everything from algebra to computer science to art history. Running the nonprofit academy is now Khan’s full-time job, and he plans to expand the enterprise further, adding more subject areas, more faculty members (until now, all the videos have been narrated by Khan himself) and translating the tutorials into the world’s most widely used languages.

Much attention has been paid to the use of Khan Academy videos in classrooms. Hundreds of schools across the U.S. have integrated his lessons into their curricula, often using them to “flip” the classroom: students watch the videos at home in the evening, then work on problem sets — what would once have been homework — in class, where there are teachers to help and peers to interact with. The approach is promising, and it may well change the way American students are taught.

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The real revolution represented by Khan Academy, however, has gone mostly unremarked upon. The new availability of sophisticated knowledge, produced by a trusted source and presented in an accessible fashion, promises to usher in a new golden age of the autodidact: the self-taught man or woman. Not just the Khan Academy, but also the nation’s top colleges and universities are giving away learning online. Khan’s alma mater, MIT, has made more than 2,000 of its courses available gratis on the Internet. Harvard, Yale, Berkeley, Johns Hopkins and Carnegie Mellon are among the other elite institutions offering such free education. When Stanford announced last August that it would be opening to the online public a course on artificial intelligence, more than 70,000 people signed up within a matter of days. The course’s two professors say they were inspired to disseminate their lessons by the example of Salman Khan. Khan Academy’s own videos now go well beyond basic algebra to teach college-level calculus, biology and chemistry.

This bonanza of educational opportunity recalls an earlier era in American history, and another man determined to make learning available to all: the steel magnate and philanthropist Andrew Carnegie. Between 1886 and 1919, he helped open 1,679 public libraries in communities all over the United States. Carnegie, a poor weaver’s son from Scotland who never went to college, gratefully recalled the generosity of a wealthy gentleman who opened his personal library to local working boys, and he resolved use his own riches to make books available to everyone. The list of Americans who educated themselves at the nation’s public libraries is a storied one: the writer Jack London, the poet Kahlil Gibran, the memoirist Frank McCourt and the playwright August Wilson are among those who made libraries their schools.

Today, of course, knowledge no longer needs to be bound into the paper and cloth of a book but can float free on the wireless waves of the Internet. There’s a lot of junk bobbing in those waves as well — information that is outdated, inaccurate, or flat-out false — so the emergence of online educational materials that are both free of charge and carefully vetted is a momentous development. This phenomenon is all the more significant given the increasing scrutiny directed at for-profit online universities, which have been criticized for burdening students with debt even as they dispense education of questionable usefulness. Websites offering high-quality instruction for free are the Carnegie libraries of the 21st century: portals of opportunity for curious and motivated learners, no matter what their material circumstances.

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So valuable is the knowledge now being made available, in fact, that one might wonder if the elite universities posting their courses online are putting themselves out of business. Who needs to attend MIT when you can watch its professors lecture from the comfort of home? Actually, the reality is precisely the opposite. As more and more people gain access to sophisticated knowledge, employers and other institutions face an ever-greater need to distinguish among them. This is where competitive universities, with their elaborate admissions processes, come in. We’re entering an era in which elite education is cheap, but elite credentials are increasingly — for most, prohibitively — expensive. Perhaps experiments like the Khan Academy won’t only flip middle- and high-school classrooms, but the entire experience of higher education. Harvard, Yale and Princeton will become glorified offices of admissions, bestowing nothing more than their coveted imprimatur, while impecunious but ambitious learners will avail themselves of an Ivy League education without the degree.

It’s still the case, of course, that workers with a college degree earn more on average than those who don’t. And perhaps universities’ online beneficence deserves a dose of skepticism: each downloaded class is an hours-long advertisement for the school, after all, and providing open-source courseware is a smart public-relations move when the cost of tuition continues to rise faster than the rate of inflation. But the fact remains that the kind of education once reserved for a monied and connected elite is now available to all comers, with consequences we can only begin to imagine. Especially in our unpredictable economy, which is opening new opportunities even as it is foreclosing conventional ones, we may well see the rise of a self-taught elite — leaders and creators who didn’t have the time or money for a traditional college education, but who nonetheless taught themselves what they needed to know.

Somewhere, Andrew Carnegie is smiling.