An Indonesian woman watches an eruption from the Mount Sinabung volcano from Tiga Pancur village, in Karo in North Sumatra on November 3, 2017. Sinabung roared back to life in 2010 for the first time in 400 years. After another period of inactivity it erupted once more in 2013, and has remained highly active since. (Photo by Ivan Damanik/AFP Photo)

A US Marine leads two Viet Cong suspects in restraints during the Tet Offensive on February 20, 1967. (Photo by Bettmann Archive/Getty Images)

Rebel fighters fire towards positions of regime forces in Ramussa on the southwestern edges of Syria's northern city of Aleppo on August 6, 2016. Syrian rebels said they have broken a three-week government siege of second city Aleppo, turning the tables on Russian-backed regime forces who are now on the defensive. (Photo by Fadi Al-Halabi/AFP Photo)

Zhao Deli waves as he pilots his self-made “flying scooter” in Dongguan, Guangdong Province, China, 12 August 2018 (issued 16 August 2018). Inspired by a cartoon he watched as a child, Zhao Deli sold off his apartment in pursuit of his dream of building a flying scooter. (Photo by Aleksandar Plavevski/EPA/EFE)

In this Friday, February 1, 2019, photo, Filipino-Chinese display piggy banks at the start of celebrations leading to next week's Lunar New Year in Chinatown, Manila, Philippines. This year is the Year of the Earth Pig on the Lunar calendar and is supposed to represent abundance, diligence and generosity. (Photo by Bullit Marquez/AP Photo)

An airplane is silhouetted at sunrise, seen from the suburb of Saint-Cloud, near Paris, France, 08 December 2016. Paris is undergoing a third day pollution spike, prompting the city to limit vehicle circulation. (Photo by Ian Langsdon/EPA)

Street fighting in Berlin between Government troops and Spartacists, during the Spartacist uprising which followed Germany's defeat in World War I. (Photo by Keystone/Getty Images). 1919

A British policewoman chasing after a group of naked street boys by the Serpentine in Hyde Park, London. (Photo by Reg Speller/Getty Images). 1926