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

(L-R) Zoe Kravitz, Jason Momoa, and Lisa Bonet attend the world premiere of “Conan The Barbarian” held at Regal Cinemas L.A. Live on August 11, 2011 in Los Angeles, California. (Photo by Jason Merritt/Getty Images)

Models showcase Valentine's Day underwear celebrating the results of a recent survey revealing that men find the lingerie, boxer shorts and vests, the biggest turn on ahead of February 14 Valentine celebrations, at Waterloo on February 2, 2006 in London, England. (Photo by Gareth Cattermole/Getty Images)

Margaret Morris dancers exercising on the sands at Saint-Idesbald. (Photo by Fox Photos/Getty Images). August 1929

A Siberian tiger cub is seen at the Hengdaohezi Breeding Center for Felidae on October 26, 2007 in Harbin of Heilongjiang Province, China. Established in 1986, the breeding center is one of the world's largest captive breeding base for Siberian tigers. Distributed throughout northeastern China, far eastern Russia and North Korea, over 400 Siberian tigers exist in the wild, approximately 20 in China. (Photo by China Photos/Getty Images)

A young boy adjusts his friend's Adolf Hitler mask during a game on a street in King's Cross, London. (Photo by William Vanderson/Getty Images). 1938

“A fter the former Soviet Union conducted its first nuclear test in August 1949, the US reevaluated its postwar defense policies. With the US monopoly on atomic weapons broken, military and political leaders chose to diversify the American stockpile by developing thermonuclear and tactical nuclear weapons. One of the more interesting concepts to come out of this period was atomic artillery, which was successfully tested at the Nevada Proving Grounds (now the Nevada Test Site) in May 1953”. – Alan Carr. Photo: Atomic Annie at work during the Upshot-Knothole test series, 1953. (Photo by Los Alamos National Laboratory/US Army)