In a makeshift production studio at the University of Pittsburgh, adjunct professor Larry Foulke is speaking passionately into a camera, preparing his online course, "A Look at Nuclear Science and Technology," for the masses.

So animated is his delivery in front of a video crew recording his lecture, it's as if he is speaking face-to-face to his class. But chances are nil that he will meet most of his students, and even if he did, there would not be enough time to greet them all.

That's because nearly 12,000 people in the United States and abroad already have signed up via the Internet for a course that does not start until June, both because of the topic and the professor, a well-known nuclear industry retiree who is interim director of Pitt's nuclear engineering program and past president of the American Nuclear Society.

"I suspect I will be reaching people all over the world," said Foulke, 75, who worked for four decades as a nuclear engineer at Westinghouse Energy Systems and Bettis Atomic Power Laboratory before coming to Pitt in 2006. "It will be kind of exciting."

Welcome to the world of MOOCs — Massive Open Online Courses — a phenomenon that is spreading rapidly, prompting even some of the nation's leading universities to gamble that giving away free instruction by some of their top faculty will pay dividends down the road.

With enrollments that can push 100,000 or more, these virtual courses generally are noncredit, though many involved in the movement see a future in awarding certificates for a fee.

Some even see potential for giving full academic credit, among them San Jose State University in California, which last month announced an experiment with online education venture Udacity Inc., to develop courses in algebra, college algebra and elementary statistics at $150 per course.

Another venture, Academic Partnerships, announced days later that universities it works with — including Arizona State University and the University of Cincinnati — will convert the initial course in certain online programs into a MOOC and award credit, an initiative dubbed MOOC2Degree.

Some universities like Pitt are developing MOOCs using shared platforms such as Coursera, a California company started by two Stanford University professors in 2011 that boasts a roster of 33 leading colleges and universities in the U.S. and abroad.

Signing up for a Coursera class is as simple as typing your name, email address and a password into the firm's website. More than 2.6 million users — or Courserians, as the website calls them — already had done as of early this month.

Anyone with a computer connection and an interest in a topic — from English literature to health informatics — can enrich themselves at their own pace from professors based at such schools as Princeton University, Ohio State University, the Massachusetts Institute of Technology, the Hong Kong University of Science and Technology and other campuses worldwide now scrambling to roll out these courses.

Students can finish as much or as little of the coursework as they like.

For schools, the upside is open to debate.

Many point to potential for stirring interest in a subject, facilitating remedial instruction, or increasing the chances that students completing a MOOC may choose to enroll in paid instruction. Others see the classes and data from them about how students learn as potential catalysts for teaching innovation.

And in academia, where the company you keep matters, having your school's MOOC listed beside one from an Ivy League school surely does not hurt.

Even so, schools are left with a nagging question: How long can instruction given away for free last?

"There has to be a sustainable financial model," said Barbara Bichelmeyer, director of the Office of Online Education at Indiana University and a professor at IU's Bloomington, Ind., campus. "We have to make sure that what we deliver is of the quality people would expect from and respect about Indiana University."

Last month, her school waded into the waters with its second MOOC.

Penn State University wants to understand how best to engage students and just where MOOCs would fit in with the university's strategy, said Craig Weidemann, Penn State vice president for outreach to whom Penn State's online World Campus reports.

But he said Penn State officials hope to announce up to five MOOCs as early as next month.