A woman in costume checks her phone at the Star Wars Celebration convention in Anaheim, California, April 16, 2015. The Star Wars Celebration runs through April 19 at the Anaheim Convention Center. (Photo by David McNew/Reuters)

In this Wednesday, July 13, 2016, handout image provided by Solar Impulse, the Solar Impulse 2 flying over the pyramids, Egypt Cairo. The experimental solar-powered airplane has arrived in Egypt as part of its global voyage. (Photo by Jean Revillard, Rezo via the AP Photo)

A Republican farmer defending a farm on the outskirts of Irun against Nationalist forces during the Spanish Civil War, 6th September 1936. A comrade lies dead by his side. (Photo by Keystone/Hulton Archive/Getty Images)

Residents of the Korean port of Inchon surrender to American troops. (Photo by Bert Hardy/Getty Images). 1950

Military enthusiasts take part in a re-enactment of the World War II battle of Stalingrad at the “Stalin Line” memorial, near the village of Goroshki, Belarus, February 27, 2016. (Photo by Vasily Fedosenko/Reuters)

A man yells for help minutes after a Serb shell hit a crowded pedestrian walkway in Sarajevo, May 1993. Radovan Karadzic, a 70-year-old former psychiatrist, still in robust health, is the most senior political figure to be convicted by the International Criminal Tribunal for the Former Yugoslavia. He was found guilty of 10 out of 11 charges. He was acquitted of a second count of genocide in Bosnian towns. (Photo by Reuters)

A military enthusiast dressed as World War Two Red Army officer sits in a cafe as he marks the 75th anniversary of the Nazi Germany invasion, in Brest, Belarus June 21, 2016. (Photo by Vasily Fedosenko/Reuters)

An interactive art installation created by artist Michael Verdon called the “Temple of Essence” dedicated to "victims of the war on drugs" is burned on the U.S. National Mall in front of the Washington Monument in Washington November 22, 2015. People were encouraged to write personal messages on the temple walls and leave mementos behind inside the interactive art piece, which was the centerpiece of a 48-hour vigil called "Catharsis on the Mall: A Vigil for Healing the Drug War". (Photo by Jim Bourg/Reuters)