A smokejumper leaps from an airplane during a training flight above Winthrop, Washington, U.S., June 30, 2016. On a 100-degree day in early June, eight experienced firefighters did sit-ups in a semicircle training to parachute into a wildfire. Better known as “rookie candidates”, they were determined to make it through the five-week program at North Cascades Smokejumper Base in Winthrop, Washington, where the first experimental jumps occurred in 1939. (Photo by David Ryder/Reuters)

The Wadi al-Salam cemetery, Arabic for “Peace Valley”, is seen in Najaf, south of Baghdad, Iraq August 3, 2016. The world's largest cemetery, in Iraq's Shi'ite holy city of Najaf, is expanding at double its usual rate as Shi'ite militias bury their dead from the war against Islamic State. The Wadi al-Salam cemetery, Arabic for “Peace Valley” has a special place in the hearts of Shi'ite Muslims as it surrounds the Mausoleum of their first imam, Ali Bin Abi Talib, a cousin and son-in-law of Prophet Mohammad. (Photo by Alaa Al-Marjani/Reuters)

People enjoy carnival while shouting slogans of female empowerment and anti harrassment in Sao Paulo, Brazil on January 28, 2018. The carnival is marked by a lot of fun, but also has space to talk about more serious things – without losing the good mood. Parading for the first time in São Paulo, the Vaca Profana block proposed a reflection on sieges and machismo. (Photo by Cris Faga/Rex Features/Shutterstock)

Su Daocheng rides his home-made mechanical horse vehicle on a street in Shiyan, Hubei province January 18, 2015. Su spent 2 months making this 1.5 metre high and 2 metre long horse, which weighed 250 kilograms with 4 legs and 2 supportive wheels, local media reported. (Photo by Reuters/Stringer)

Andrea Petkovic of Germany in action against Sara Errani of Italy during day one of the Mutua Madrid Open tennis tournament at the Caja Magica on May 3, 2014 in Madrid, Spain. (Photo by Julian Finney/Getty Images)

Mario Huettenhofer, chief of the German company 3D Fab, presents his own face as 3d print during the international fairs FabCon 3.D and Rapid.Tech in Erfurt, Germany, Thursday, May 15, 2014. 130 exhibitors from all over the world present the entire world of 3D printing. The trade fairs are accompanied by specialist programs featuring 80 scientists, practitioners and trend analysts from ten countries, who will explain the latest findings, trends and applications for additive processes in industry and for 3D printing in the private sector to newcomers, experts and consumers alike. (Photo by Jens Meyer/AP Photo)

A photo taken on August 29, 2014, shows Mount Tavurvur erupting in eastern Papua New Guinea, spewing rocks and ash into the air, forcing the evacuation of local communities and international flights to be re-routed. Mount Tavurvur, which destroyed the town of Rabaul when it erupted simultaneously with nearby Mount Vulcan in 1994, rumbled to life early in the morning on the tip of the remote island of New Britain. (Photo by Oliver Bluett/AFP Photo)

Athletes from Australia's Olympic team going to the 2016 Olympics in Rio present their uniforms alongside Brazilian Samba dancer Sashya Jay at an official unveiling ceremony at Sydney's Bondi Beach, March 30, 2016. (Photo by Jason Reed/Reuters)