Coursera founders Andrew Ng and Daphne Koller are computer science professors at Stanford University. Jeff Chiu/AP hide caption

President Obama speaks during a campaign event at University of Colorado Boulder Sept. 2. He and his Republican challenger, Mitt Romney, will have their first debate at the University of Denver on Wednesday. Pablo Martinez Monsivais/AP hide caption

Vice President Richard Nixon listens as Sen. John F. Kennedy talks during their televised presidential race debate. This photo was made from a television screen in New York, Oct. 21, 1960. AP hide caption

Plankton make up 98 percent of the biomass of ocean life and provide half of the oxygen on the planet. Scientists are working to figure out how climate change may be affecting these important microorganisms. M. Ormestad/Tara Oceans hide caption

Las Cafeteras, from Los Angeles, have made their own version of the classic son jarocho song "La Bamba." Courtesy of the artist hide caption