Festival goers arrive for the Glastonbury festival at Worthy Farm, in Somerset, England, Thursday, June 23, 2016. (Photo by Guy Bell/Rex Features/Shutterstock)

Workers clean empty cooking oil containers at a roadside recycling workshop in Kolkata, India, July 13, 2016. (Photo by Rupak De Chowdhuri/Reuters)

A tourist poses on the glass-bottom bridge at Zhangjiajie Grand Canyon on August 20, 2016 in Zhangjiajie, Hunan Province of China. The Zhangjiajie Grand Canyon's glass-bottomed bridge welcame its trial operation on Saturday and about 8,000 tourists crowded to view the grand glass bridge. (Photo by VCG/VCG via Getty Images)

Female of pygmy hippopotamus called Malaya from Netherlands in zoo in Dvur Kralove nad Labem, Czech Republic, February 22, 2016. (Photo by David Tanecek/CTK via ZUMA Press)

A refugee sits in front of a Greek riot police cordon during a protest at the Greek-Macedonian border, near the Greek village of Idomeni, March 1, 2016. (Photo by Alexandros Avramidis/Reuters)

An empty cell block is pictured within Joint Task Force Guantanamo's Camp VI at the U.S. Naval Base in Guantanamo Bay, Cuba March 22, 2016. (Photo by Lucas Jackson/Reuters)

Li Guoqiang talks on his phone outside his house at Guangfuli neighbourhood, in Shanghai, China, April 1, 2016. Li, 38, is a deliveryman who rents a place at Guangfuli. In a corner of Shanghai, surrounded by a cement wall, lies one of the world's most valuable fields of debris and garbage. On paper, the Guangfuli neighbourhood is a real estate investor's dream: a plot in the middle of one of the world's most expensive and fast-rising property markets. But the reality is more like a developer's nightmare, thanks to hundreds of people living there who have refused to budge from their ramshackle homes for nearly 16 years as the local authority sought to clear the land for new construction. (Photo by Aly Song/Reuters)

A wide-angle view shows the ascent of the shuttle Challenger on January 28, 1986. In the seconds after ignition, the rocket engines' hot blast began the process of destruction. (Photo by NASA)