Master science communicator Brian Greene shares the spotlight with Muppet scientist Dr. Bunsen Honeydew ahead of the 2008 World Science Festival in New York City. Scott Gries/Getty Images hide caption

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Andrew Ng and Daphne Koller, Stanford University computer science professors who started Coursera, pose for a photo at the Coursera office in Mountain View, Calif., on Aug. 2, 2012. Jeff Chiu/AP hide caption

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The University of Tennessee became one of 10 state university systems teaming up with Coursera, a for-profit tech company. Flickr Creative Commons hide caption

itoggle caption Flickr Creative Commons