A split image shows Allen Ginsberg in 1953 and 1967. Allen Ginsberg LLC/Corbis | The National Portrait Gallery hide caption

itoggle caption Allen Ginsberg LLC/Corbis | The National Portrait Gallery

Carnegie Lake, Australia, 1999 Carnegie Lake in Western Australia fills with water only during periods of significant rainfall. In dry years, it is reduced to a muddy marsh. Flooded areas appear dark blue or black, vegetation appears in shades of dark and light green, and sands, soils and minerals appear in a variety of colors. NASA hide caption

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Part four delves into the world of people who live in 24-hour Internet cafes because they can't afford rent. Courtesy of Shiho Fukada/Panos Pictures hide caption

itoggle caption Courtesy of Shiho Fukada/Panos Pictures

President Obama delivers his State of the Union address last year. On Tuesday night, he will be back at the Capitol for another address to a joint session of Congress. Getty Images hide caption

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A boy hitches a ride on a suitcase as he waits to board a train at Beijing West Railway Station during Chunyun travel peak on Feb. 8, 2007. China Photos/Getty Images hide caption

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Rudi Kistler and Maurus Oehmann, Mannheim 2012 Courtesy of Francois Brunelle hide caption

itoggle caption Courtesy of Francois Brunelle