Battle-weary American troops withdraw from Yong San in Korea. (Photo by Keystone/Getty Images). 1950

A man photographs the main engines of the space shuttle orbiter Discovery on display at the Udvar-Hazy Smithsonian National Air and Space Annex Museum in Chantilly, Virginia August 28, 2015. Shuttle Discovery had 27 years of service and flew 39 times before being retired in 2011. (Photo by Gary Cameron/Reuters)

The Eiffel Tower is illuminated during the traditional Bastille Day fireworks display in Paris, July 14, 2013. (Photo by Fred Dufour/AFP Photo)

A prototype battery-powered plane, called Greased Lightning or GL-10 is pictured flying at NASA's Langley Research Center in this undated handout photo obtained by Reuters May 1, 2015. The plane, which has 10 engines and can take off like a helicopter and fly efficiently like an aircraft, is currently in the design and testing phase. (Photo by Reuters/NASA)

A candle burns during a vigil in Aotea Square to remember victims of the Paris attacks on November 14, 2015 in Auckland, New Zealand. According to reports, over 150 people were killed in a series of bombings and shootings across Paris, including at a soccer game at the Stade de France and a concert at the Bataclan theater. (Photo by Hannah Peters/Getty Images)

Street artist JR poses in front the Louvre Pyramid in Paris, Tuesday, May 24, 2016. For his latest bold project, street artist JR is creating an eye-tricking installation at the Louvre Museum that makes it seem as if the huge glass pyramid at the heart of the courtyard has disappeared. (Photo by Francois Mori/AP Photo)

This aerial picture taken on June 29, 2024 shows fishing boats moored at a beach in Danang, central Vietnam. (Photo by Dale De La Rey/AFP Photo)

Britain's Chris Froome, wearing the overall leader's yellow jersey, is followed by Spain's Alberto Losada, Italy's Vincenzo Nibali and Spain's Alejandro Valverde as they speed downhill during the seventeenth stage of the Tour de France cycling race over 161 kilometers (100 miles) with start in Digne-les-Bains and finish in Pra Loup, France, Wednesday, July 22, 2015. (Photo by Christophe Ena/AP Photo)