Dancers at the Windmill Theatre in London, England practice a routine wearing gas masks and hard-hats with their costumes, 1940. (Photo by Hulton Archive/Getty Images)

A man walks past an advertisement sign promoting a bank in Seoul in this September 3, 2009 file photo. South Korea is expected to release GDP dara this week. (Photo by Lee Jae-Won/Reuters)

A girl with Russian national flags painted on her cheeks takes part in celebrations marking the first anniversary of Russia's annexation of Crimea, in central Simferopol March 16, 2015. Russia marks one year anniversary of annexation of Ukraine's Crimea peninsula this week. (Photo by Maxim Shemetov/Reuters)

A woman holds her umbrella while walking against strong winds as Typhoon Chan-hom approaches Taiwan, in Taipei, July 10, 2015. (Photo by Pichi Chuang/Reuters)

Cars are parked near Place de la Concorde on March 12, 2014 in Paris, France. Inset: World War I, German airplanes at Place de la Concorde in Paris, wrecked by celebrating crowds on the day of the restoration of Alsace-Lorraine, November 18, 1918. (Photo by Peter Macdiarmid/Getty Images)

A hot air-balloon flies during the International Lorraine Mondial Air Balloons Festival, in Chambley-Bussieres, eastern France, Friday, July 26, 2013. (Photo by Mathieu Cugnot/AP Photo)

Marc Berthod of Switzerland during the Audi FIS Alpine Ski World Cup Men's Super Combined on February 12, 2012 in Sochi, Russia. (Photo by Vianney Thibaut/Agence Zoom/Getty Images)

In this artist's impression supplied by the ESO (European Southern Observatory) on April 25, 2007, the planetary system around the red dwarf, Gliese 581, is pictured showing what astronomers believe is the most earth like planet found outside our solar system to date. Using the ESO 3.6-m telescope in Chile, astronomers have uncovered the planet which could have water running on its surface. The planet orbits the faint star Gliese 581, which is 20.5 light-years away in the constellation Libra. (Photo by ESO via Getty Images)