Visitors explore Robert Irwin's Scrim Veil--Black Rectangle--Natural Light during its 2013 reprise at the Whitney Museum of American Art. ©Robert Irwin/Photography ©2013 Philipp Scholz Rittermann/Courtesy of the Whitney Museum hide caption

itoggle caption ©Robert Irwin/Photography ©2013 Philipp Scholz Rittermann/Courtesy of the Whitney Museum

Physicists searching for a "Theory Of Everything" are like kayakers paddling against the current, in search of the water's source. iStockphoto.com hide caption

itoggle caption iStockphoto.com

A gay-rights activist chants slogans during a demonstration in front of the Russian Consulate in New York on July 31. Gays in the United States and elsewhere are outraged by Russia's intensifying campaign against gay-rights activism. Mary Altaffer/AP hide caption

itoggle caption Mary Altaffer/AP