An Anti-Balaka fighter, member of a militia opposed to the Seleka rebel group, puts a knife to his throat showing what he would do to any Seleka, on the outskirts of the Boy-Rabe neighborhood in Bangui on December 14, 2013. France raised alarm on December 13 over worsening violence in the Central African Republic, as UN chief Ban Ki-moon urged warring Christians and Muslims to stop the bloodshed that has left more than 600 dead in the past week. (Photo by Ivan Lieman/AFP Photo)

Images are projected onto the Empire State Building as part of an endangered species projection to raise awareness, in New York August 1, 2015. (Photo by Eduardo Munoz/Reuters)

A Syria Democratic Forces (SDF) fighter comforts a civilian who was evacuated with others by the SDF from an Islamic State-controlled neighbourhood of Manbij, in Aleppo Governorate, Syria, August 12, 2016. The SDF has said Islamic State was using civilians as human shields. (Photo by Rodi Said/Reuters)

A woman waits at a polio immunisation health centre, in Maiduguri, Borno State, Nigeria, August 29, 2016. Nigeria's military has liberated large swathes of land from Boko Haram but a ride with an army convoy, all guns firing for fear of ambush, shows how far the northeast is from normality after a brutal Islamist insurgency that has displaced millions. (Photo by Afolabi Sotunde/Reuters)

Iranian-Kurdish female fighters hold their weapons during a battle with Islamic State militants in Bashiqa, near Mosul, Iraq on November 3, 2016. (Photo by Ahmed Jadallah/Reuters)

Layers of breathtaking colour streak the rolling hills of this vast desert, making the landscape appear as though it has been tie-dyed. The natural phenomenon, nicknamed the “Painted Desert”, was formed when the area was once a river floodplain. Each colour corresponds to a different underground geological feature – rocks which have seemingly dyed the layers of earth above. Formed from volcanic activity, the hills at the John Day Fossil Beds National Monument in East Central Oregon, USA, are almost bursting with colour. Pictured: The colourful hills at the John Day Fossil Beds National Monument in East Central Oregon, USA. (Photo by Mark Brodkin/Solent News/SIPA Press)

A workman sweeping the highest sidewalk in the world, the 81st story of the Empire State Building, the world's tallest building, to the top of which the greatest dirigible “Los Angeles” will attempt to moor, New York, New York, early 1930s. This photo was made 1,248 feet above street level. (Photo by Adam Glickman/Underwood Archives/Getty Images)

“A meteor streaked across the sky above Russia's Ural Mountains on Friday morning, causing sharp explosions and injuring more than 500 people (20 had been hospitalized in serious condition), many of them hurt by broken glass. “There was panic. People had no idea what was happening. Everyone was going around to people's houses to check if they were OK”, said Sergey Hametov, a resident of Chelyabinsk, about 1500 kilometres (930 miles) east of Moscow, the biggest city in the affected region”. (Photo by Alexey Bulaew/RIA Nowosti)