The Orbiting Carbon Observatory-2 will monitor carbon dioxide emissions. jhoward/NASA/JPL hide caption

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Katherine Streeter for NPR

Over the past century and a half, visitors have traveled through Yosemite on foot, by carriage, by tram and by car. Now some regions will be once again be accessible only by foot, to protect delicate regions of the park. Courtesy Yosemite National Park Research Library/KQED hide caption

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Martha looks just as good today as she did in 1914. Elizabeth O'Brien/Smithsonian Institution hide caption

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Portugal's Cristiano Ronaldo takes a water break during the 2014 World Cup soccer match between Portugal and the U.S. in Manaus, Brazil, on June 22. Siphiwe Sibeko/Reuters/Landov hide caption

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Michael Yezzi raises 1,000 pigs a year in Shushan, N.Y. He's worried about how to keep his farm safe from a disease that has no proven cure. Abbie Fentress Swanson for NPR hide caption

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