Facebook CEO Mark Zuckerberg (L) watches a demonstration of the new Facebook video chat during a news conference at Facebook headquarters July 6, 2011 in Palo Alto, California. Zuckerberg announced new features that are coming to Facebook including video chat and a group chat feature. (Photo by Justin Sullivan/Getty Images)

Brave slackliners have been pictured walking the ropes above Rio de Janeiro, Brazil on August 15, 2016, with the half a mile drop showing the city in all its glory. The stunning shots show the daredevils tread across an eighty-two-foot-long high line on Pedra da Gvea mountain with an amazing sunrise illuminating the city landscape behind. (Photo by Rafael Moura/Caters News Agency)

A workman takes a siesta on a girder during the building of Radio City, the city of New York spread out below. (Photo by General Photographic Agency/Getty Images). Circa 1933

Priest Sergei Ryzhov conducts a ceremony as a man takes a dip in the freezing waters of Lake Buzim during Orthodox Epiphany celebrations near the village of Sukhobuzimskoye north of Krasnoyarsk, Russia on January 19, 2018. (Photo by Ilya Naymushin/Reuters)

Battersea Power Station. The chimney rims are thinner on top than you might expect. (Photo by Bradley L. Garrett)

A worker pauses for a sandwich, resting on a girder during the construction of a skycraper. (Photo by Hulton Archive/Getty Images). Circa 1930

Vietnamese military personnel in traditional dress take part in a parade celebrating the 40th anniversary of the end of the Vietnam War which is also remembered as the fall of Saigon, in Ho Chi Minh City, Vietnam, Thursday, April 30, 2015. (Photo by Dita Alangkara/AP Photo)

Blood drips down from the face of a Shi'ite Muslim boy after practicing a self-flagellation ritual during a religious procession of the Ashura mourning period on December 6, 2011 in New Delhi, India. (Photo by Daniel Berehulak/Getty Images)