Fireworks explode over Elizabeth Tower housing the Big Ben clock in London. (Photo by Kirsty Wigglesworth/Associated Press)

This handout picture taken on December 13, 2016 and released on December 14, 2016 by the Tiergarten Schoenbrunn zoo in Vienna, Austria, shows a baby sloth eating some salad as it hangs on it's mother's belly in their enclosure. The baby was born already on November 18, 2016, but according to the zoo it could be picured for the first time only now as it usually hides in it's mother's soft coat. (Photo by Daniel Zupanc/AFP Photo)

Rick Sorenson, owner of the Rio Ramaza Marina, wades in the Sacramento River after securing an old paddlewheel boat on his property as the river makes its way up the levee on Garden Highway in Sacramento, Calif., Monday, January 9, 2017. (Photo by Hector Amezcua/The Sacramento Bee via AP Photo)

Pope Francis attends a circus performance during his weekly general audience at Paul VI hall on December 22, 2016 at the Vatican. (Photo by Alberto Pizzoli/AFP Photo)

A baby Black-crowned Night Heron squawks in its incubator while being cared for at City Wildlife rescue and rehabilitation center in Washington, DC on May 31, 2017. The heron is one of several that have been brought to CW by the staff at The National Zoo over the past few years. (Photo Linda Davidson/The Washington Post)

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)

A woman, wearing a traditional Sevillana dress, performs as she asks for alms in downtown Malaga, Spain, April 28, 2016. (Photo by Jon Nazca/Reuters)

A colorful sky at sunset over the snowy mountains in Immenstadt, Bavaria, Germany, 20 November 2014. Cloudy weather is forecast in the region on 21 November. (Photo by Karl-Josef Hildenbrand/EPA)