A polar bear fast asleep at London Zoo. (Photo by Fox Photos/Getty Images). 1961

One of the two wooden rafts of the Kon-Tiki II expedition is prepared at the port of Callao prior to the departure to Pascua island in Chile, in Callao, Peru, October 30, 2015. Fourteen men from various parts of the world set out on rafts to commemorate the Norwegian navigator Thor Heyerdahl expedition 68 years ago. The original raft crossed the Pacific Ocean from South America to the Polynesian Islands. This rafts are a replica of ships used 6,000 years ago, but will be equipped with solar panel. (Photo by Mariana Bazo/Reuters)

A painting of a Trabant car bursting through a wall in post unification Berlin, August 1993. (Photo by Steve Eason/Hulton Archive/Getty Images)

A nurse consoles herself with a box of chocolates as she reads a paper-back thriller. (Photo by Hulton Archive/Getty Images). Circa 1955

Two dummy tanks being pushed along a road by German soldiers. (Photo by Hulton Archive/Getty Images). Circa 1925

King George V inspects the day's kill after a tiger hunt in India during his royal visit to celebrate his accession to the throne. (Photo by Hulton Archive/Getty Images). 1911

In this March 7, 1991 file photo, a U.S. Marine patrol walks across the charred oil landscape near a burning well during perimeter security patrol near Kuwait City. Twenty five years after the first U.S. Marines swept across the border into Kuwait in the 1991 Gulf War, American forces find themselves battling the extremist Islamic State group, born out of al-Qaida, in the splintered territories of Iraq and Syria. The Arab allies that joined the 1991 coalition are fighting their own conflicts both at home and abroad, as Iran vies for greater regional power following a nuclear deal with world powers. (Photo by John Gaps III/AP Photo)