In this March 22, 1975 file photo, a refugee clutches a baby as a government helicopter gunship carries them away near Tuy Hoa, Vietnam, 235 miles northeast of Saigon. They were among thousands fleeing from Communist advances. AP Photographer Nick Ut will be retiring from the AP in March 2017 after 51 years of taking photographs from the front lines of the Vietnam War to the red carpets of Hollywood. (Photo by Nick Ut/AP Photo)

Unwanted phones recreated as interactive birds, part of “Escape III” by Anthony Goh and Neil Mendoza seen on display at the Barbican's Digital Revolution exhibition on July 2, 2014 in London, England. The exhibition brings together artists, designers, film makers, musicians and architects who push the boundaries of creativity that digitial technology can offer, and runs from July 3 until September 14, 2014. (Photo by Matthew Lloyd/Getty Images for Barbican Art Gallery)

Yaks head towards the Everest base camp in Solukhumbu District April 28, 2014. (Photo by Navesh Chitrakar/Reuters)

People take pictures of the sunset in Berlin October 27, 2014. (Photo by Hannibal Hanschke/Reuters)

A Santa Claus puppet holding a Christmas tree is pictured against the sun in Berlin November 23, 2014. (Photo by Hannibal Hanschke/Reuters)

Hungarian wrestlers fight during the Hungarian wrestling Championship in Budapest November 29, 2014. (Photo by Laszlo Balogh/Reuters)

Steam emerges from a cooling tower of the nuclear power plant Leibstadt near Leibstadt, Switzerland, November 18, 2014. (Photo by Arnd Wiegmann/Reuters)