UmmaGawd (Tommy Tibajia), a pilot in the Drone Racing League, flies his quadcopter in an abandoned power plant in New York. The Drone Racing League hide caption

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After knee surgery, David Larson, 66, of Huntington Beach, Calif., experienced pain in a calf muscle. His answer to an automated email from the doctor led to the diagnosis and treatment of a potentially dangerous blood clot. Heidi de Marco/Kaiser Health News hide caption

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Comedian and actress Grace Helbig is a star on YouTube. "Having an audience that listens to and resonates with your creative ideas is invaluable," she says. Paul A. Hebert/Invision/AP hide caption

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The Yik Yak app allows users to post anonymous messages, and to read anonymous messages posted in their current location. Ariel Zambelich/NPR hide caption

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The Cedid atlas was "the first Muslim-published world atlas based on European geographic knowledge and cartographic methods," the Library of Congress writes. The National Library of Norway just discovered a previously unknown copy in their collection, after a reference librarian posted a scan of it to Reddit. Nikolaj Blegvad/The National Library of Norway hide caption

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Wikipedia, the crowd-sourced encyclopedia, turns 15. Emily Bogle/NPR hide caption

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President Obama gives his State of the Union address in Washington on Tuesday. Susan Walsh/AP hide caption

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