Medieval jousters Luke Binks (L) and Andrew McKinnon pose for a photograph in Sydney, Australia, August 16, 2017 during a photo call for the World Jousting Championships to take place in Sydney on September 23 and 24. (Photo by Dan Himbrechts/Reuters/AAP)

An enterprising Chinese man pulls a bicycle cart packed high with bags of recyclable plastic containers in Shanghai July 25, 2002. The man sells each kilogram (2.2 pounds) of plastic for 0.08 yuan ($.01) to a nearby depot. (Photo by Claro Cortes IV/Reuters)

An American soldier walks ahead of an MKIV (Mark IV) British-made tank, circa 1918. (Photo by Hulton Archive/Getty Images)