Sen. Bernie Sanders drew a large crowd when he launched his campaign last month in Burlington, Vt., and the crowds have continued. Andy Duback/AP hide caption

Chris Tremblay, a member of the Passive Acoustics group at NOAA's Northeast Fisheries Science Center, deploys an underwater recording device along the Eastern Seaboard to listen for the mating sounds of Atlantic cod. Courtesy of Chris Tremblay hide caption

Street hawkers have taken over so many sidewalks in Harare's city center that some vendors are turning their cars into makeshift shops. Tsvangirayi Mukwazhi/AP hide caption

Aziz Ansari is a writer, stand-up comedian and actor well-known for playing Tom Haverford in NBC's Parks and Recreation. Ruvan Wijesooriy/Courtesy of Penguin Press hide caption

The long "oral arms" of the adult moon jelly, Aurelia aurita, extend from near its mouth, in the center of the bell. Magnus Manske/Wikimedia Commons hide caption

A surprising number of Social Security numbers have been stolen, and that number keeps rising. Justin Sullivan/Getty Images hide caption

Fauzia Din came to the United States as a refugee from Afghanistan in 2000, and later petitioned for an immigrant visa for her husband. The Supreme Court concluded a consular officer was justified in citing unspecified "terrorist activities" in denying that visa. Mandel Ngan/AFP/Getty Images hide caption

The sun sets over the Sacramento-San Joaquin River Delta near Rio Vista, Calif., in 2013. The delta is the largest West Coast estuary and a source of conflict over the state's water. Robert Galbraith /Reuters/Landov hide caption