A young arab boy, armed with a rifle and a knife, in the Aden Protectorate near Yemen. (Photo by Richards/Fox Photos/Getty Images). February 1938

A young exhibitor arrives with her kitten on a lead at the National Cat Club show at Crystal Palace, London. (Photo by Fox Photos/Getty Images). 2nd December 1931

Waura Indians wrestle during this year's “quarup”, a ritual held over several days to honour in death a person of great importance to them, in Xingu National Park, Mato Grosso State, Brazil August 25, 2013. (Photo by Ueslei Marcelino/Reuters)

Astronaut Chris Hadfield Explains How to Wash your Hands in Space.

Look at the image for long enough and you can make the train change direction simply by thinking about it. Freaky.

Russian soldiers write home while serving on the Eastern Front during World War I, circa 1915. (Photo by Hulton Archive/Getty Images)

Actor Rarmian Newton who plays the character Hiccup rides Toothless during a scene run through of the “How to Train Your Dragon Arena Spectacular” at Hisense Arena on March 7, 2012 in Melbourne, Australia. (Photo by Robert Cianflone/Getty Images)

British Liberal politician Cyril Smith relaxes on the beach at Margate, prior to the morning session of the annual Party Conference. (Photo by Keystone/Getty Images). 1979