Devotees ride on the roof of a train as they return to the city after attending the final prayers on the first phase of Bishwa Ijtema in Dhaka January 11, 2015. Hundreds of thousands of pilgrims congregated in the Bangladeshi capital Dhaka as the first phase of this year's Bishwa Ijtema, one of the biggest Islamic gatherings in the world after the Haj in Saudi Arabia, came to an end. (Photo by Reuters/Stringer)

A panda bear sits on a logs in a zoo on January 15, 2015 in Hangzhou, China. (Photo by Feature China/Barcroft Media)

“Thunderstruck”. Summer stom. A super cell formed off the coast of New Zealand, intensified and swept across Christchurch and North Canterbury, February 23, 2014. Photo location: Christchurch, New Zealand. (Photo and caption by David Hardy/National Geographic Photo Contest)

A girl sticks out her tongue during snowfalls on a street in Hefei, Anhui province February 13, 2014. (Photo by Reuters/Stringer)

Daniel Ricciardo performs alongside Michael Kneightley in an RAAF F/A-18 Hornet at RAAF Base in East Sale, Victoria, Australia on March 12th, 2014. (Photo by Andy Green/Red Bull Content Pool)

Libyan leader Muammar Gaddafi attends the inauguration ceremony of Jacob Zuma on May 9, 2009 in Pretoria, South Africa. Jacob Gedleyihlekisa Zuma is South Africa's fourth President since the end of apartheid. (Photo by Foto24/Gallo Images/Getty Images)

Pinky Ghelani and Suzzy Wokabi watch a TV broadcast of Britain's Prince Harry and Meghan Markle's royal wedding at the Windsor golf and country club in Nairobi, Kenya May 19, 2018. (Photo by Thomas Mukoya/Reuters)

Two robotic legged squad support system (LS3) machines by the Defense Advanced Research Project Agency follow a technician during a demonstration at Joint Base Myer-Henderson Hall, Virginia, on September 10, 2012. (U.S. Marine Corps photo by Sgt. Mallory S. VanderSchans via The Atlantic)