Massive open online courses, or MOOCs, are classes that anyone can take anywhere in the world -- for free. They've grown increasingly popular, but does that popularity threaten traditional higher education? 

As part of PBS NewsHour's Rethinking College series, Hari Sreenivasan takes a look at how MOOCs are changing higher education. 

MOOCs initially generated huge expectations. Many hoped they would make higher education more affordable and accessible to students around the globe. But the format has met with some criticism from professors, who say computers cannot equal the quality of in-person teaching. 

MOOCs see large enrollment numbers, but are plagued by low completion rates. 

But some teachers, like professor Brian White at UMass Boston, are embracing what online learning can bring to the brick-and-mortar classroom. White uses MOOCs in the classroom through a technique called blended learning. Students listen to lectures online at home, and then use valuable class time to delve deeper into the material with the professor. White explains.

To extent that I can be replaced with a videotape, fine, replace that part with a videotape. Leave me to do what I do best, which is work with students. 

Anant Agarwal is president of EdX, Harvard and MIT's $60 million online-learning venture and one of the largest MOOC distributors in the country. 

Last September, WGBH's On Campus spoke with Agarwal and took a look at the challenges MOOCs provide for traditional higher ed, especially for smaller colleges. 

You can listen to that story here: 

This story is part of a week-long series airing on PBS and WGBH. 

For more information about the series visit the PBS NewHour's Rethinking College page.