A boy runs with a burning barrel soaked in tar at the annual Ottery St Mary tar barrel festival on November 5, 2015 in Ottery St. Mary, England. The tradition, which is over 400 years old, sees competitors (who must have been born in the town to take part) running with burning barrels on their backs through the village, until the heat becomes too unbearable or the barrel breaks down, starting with junior barrels carried by children and continuing all evening with ever larger and larger barrels. The event, which has been threatened with closure on previous years due to increasing public liability insurance costs, raises thousands of pounds for charity and attracts spectators from around the world. (Photo by Matt Cardy/Getty Images)

The coendou porcupine couple 'Joppi' (L) and 'Fletcher' nibble at a vegetables in their enclosure at the zoo in Frankfurt am Main, Germany, 03 December 2015. Coendou porcupines are nocturnal rodents related to porcupines and guinea pigs and native to the rain forests of Central and South America as well as Trinidad. (Photo by Arne Dedert/EPA)

Women kiss each other as people celebrate outside the Stonewall Inn in the Greenwich Village neighborhood of New York June 26, 2015. The Supreme Court ruled on Friday that the U.S. Constitution provides same-s*x couples the right to marry, handing a historic triumph to the American gay rights movement. (Photo by Eduardo Munoz/Reuters)

Mrs. Marie Graskamp of Milwaukee shows the different positions one might assume when entering the bomb shelter in Milwaukee September 3, 1958. This circular entrance is about three feet in diameter. This is the entrance (according to the builders) that would connect to the cellar of a home assuming the shelter was in the ground for added protection. If a bombing should occur, all members of family would proceed to the cellar and then through the circular port into the shelter. (Photo by AP Photo)

Youths parade wearing World War Two uniforms during the Independence Day celebrations in Gdansk November 11, 2014. (Photo by Lukasz Glowala/Reuters/Agencja Gazeta)

A policeman looks at a car crushed underneath a collapsed bridge in Belo Horizonte, Brazil, Thursday, July 3, 2014. The overpass under construction collapsed Thursday in the Brazilian World Cup host city. The incident took place on a main avenue, the expansion of which was part of the World Cup infrastructure plan but, like most urban mobility projects related to the Cup, was not finished on time for the event. (Photo by Victor R. Caivano/AP Photo)

Julian Rodriguez, of Everson, Wash., holds his two-gram packet of recreational marijuana outside Top Shelf Cannabis, Tuesday, July 8, 2014, in Bellingham, Wash., on the first day of legal sales in the state. (Photo by Ted S. Warren/AP Photo)

Merit Prize Winner: “A Well Earned Rest in the Sahara”. This photo of Moussa Macher, our Tuareg guide, was taken at the summit of Tin-Merzouga, the largest dune (or erg) in the Tadrat region of the Sahara desert in southern Algeria. Moussa rested while waiting for us to finish our 45-minute struggle to the top. It only took ten minutes of rolling, running, and jumping to get back down. The Tadrat is part of the Tassili N'Ajjer National Park World Heritage area, famous for its red sand and engravings and rock paintings of cattle, elephants, giraffes, and rhinos that lived there when the climate was milder. Photo location: Summit of Tin-Merzouga, Tadrat, Tassili N'Ajjer National Park, Algeria. (Photo and caption by Evan Cole/National Geographic Photo Contest)