A man lights up his cigarette with the flames of a bus burned by anti-government demonstrators during a protest against the constitutional amendment PEC 55, which limits public spending, in front of Brazil's National Congress in Brasilia, Brazil December 13, 2016. (Photo by Adriano Machado/Reuters)

A supporter of “Si” vote cries after the nation voted “NO” in a referendum on a peace deal between the government and Revolutionary Armed Forces of Colombia (FARC) rebels, at Bolivar Square in Bogota, Colombia, October 2, 2016. (Photo by John Vizcaino/Reuters)

In this handout provided by the National Aeronautics and Space Administration (NASA), SpaceX's Falcon 9 is moved to the launch pad prior to the rocket's Thales Alenia Space launch attempt on April 26, 2015 in Cape Canaveral, Florida. (Photo by NASA via Getty Images)

An Iranian soldier guards two German tourists near the Iranian-Turkish border during World War II. Since the British occupation of Iran, all Axis nationals are being expelled from the country. (Photo by Three Lions/Getty Images). Circa 1941

Train attendants take part in a parade training as they visit the national flag guard during a patriotic education event ahead of the 90th anniversary of the founding of the Chinese People's Liberation Army (PLA) in Beijing, China July 25, 2017. (Photo by Reuters/China Stringer Network)

Festival goers participate in a dance class on embracing kinetic intimacy in the dance shala a the Oregon Eclipse Festival, August 20, 2017, at Big Summit Prairie ranch in Oregon' s Ochoco National Forest near the city of Mitchell ahead of the total solar eclipse on August 21, 2017. (Photo by Robyn Beck/AFP Photo)

Female winner Ane Guro Moen at Hardangervidda Marathon on September 2, 2017 in Eidfjord, Norway. Hardangervidda Marathon goes through parts of the National Park of Hardangervidda, passing through glaciers and waterfalls. (Photo by Kai-Otto Melau/Getty Images)

South Vietnamese forces escort suspected Viet Cong officer Nguyen Van Lem (also known as Bay Lop) on a Saigon street February 1, 1968, early in the Tet Offensive. Moments later, Lem was executed by Gen. Nguyen Ngoc Loan, chief of the national police. (Photo by Eddie Adams/AP Photo)