A member of the German wireless police picks up signals on the radio equipment he carries on his back, while his colleague takes notes. (Photo by General Photographic Agency/Getty Images). Circa 1925

A Mark IV tank, part of the parade at the Lord Mayor's Show in London. (Photo by Topical Press Agency/Getty Images). November 1917

A workman takes a siesta on a girder during the building of Radio City, the city of New York spread out below. (Photo by General Photographic Agency/Getty Images). Circa 1933

Krastsvetmet, located beside the beautiful Yensei river in the metropolis of Krasnoyarsk, Russia, is a refinery of all types of precious metals on an industrial scale.

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

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

Mark Trotter and Luke Thompson of New Zealand compete in the Senior Prearranged Sparring on the final day of the 2011 ITF Taekwon-Do World Championships at TSB Bank Arena on March 13, 2011 in Wellington, New Zealand.