A newly-married couple takes a nap before their mass wedding ceremony at the CheongShim Peace World Center in Gapyeong, South Korea, Sunday, February 17, 2013. Some 3,500 South Korean and foreign couples exchanged or reaffirmed marriage vows in the Unification Church's mass wedding arranged by Hak Ja Han Moon, a wife of the late Rev. Sun Myung Moon, the controversial founder of the Unification Church. (Photo by Lee Jin-man/AP Photo)

Max Gold, 20, of NYC, cruises on his skateboard as thousands gather on the National Mall for the March for Science on Saturday, April 22, 2017, in Washington, DC. Activists and scientists descend on the nation's capital to rally for environmental causes and government policies rooted in scientific research as part of the Earth Day and March for Science rallies. (Photo by Jahi Chikwendiu/The Washington Post)

Tsar Alexander II (1818–1881) known as “The Liberator” lying in state. He was mortally wounded by an assassination attack in St Petersburg. (Photo by Hulton Archive/Getty Images). March 1881

Models smoke during a break at Sevilla de Boda (Seville Wedding) fashion show in the Andalusian capital of Seville November 27, 2015. (Photo by Marcelo del Pozo/Reuters)

Private Harold L. Langhofer edges into the ball-turret, March 9, 1943. Curled in this position, he can turn the turret so that it fires in any direction. The turret can also be swung around so that the hatch opens into the plane, and the gunner can crawl into it while the Flying Fortress is in motion. (Photo by AP Photo)

Beach Policeman, Potomac River, 1922. (Photo by National Photo Company/Colorized by Patty Allison)

In this photo provided by Rolex, jury members inspect a 1933 Duesenberg SJ Brunn Riviera Convertible Sedan owned by John D. Groendyke at the Rolex Monterey Motorsports Reunion during Monterey’s Classic Car Week, Sunday, August 17, 2014, in Carmel, Calif. (Photo by Tom O’Neal/AP Photo/Rolex)

A two-horse team street cleaner, with sprayer, squeegee, and roller at rear. New York, between ca. 1910 and ca. 1915. (Photo by NYC Municipal Archives)