“What created this unusual hole in Mars? The hole was discovered by chance on images of the dusty slopes of Mars' Pavonis Mons volcano taken by the HiRISE instrument aboard the robotic Mars Reconnaissance Orbiter currently circling Mars”. (Photo by NASA/JPL/University of Arizona)

“The 1926 general strike in the United Kingdom was a general strike that lasted nine days, from 4 May 1926 to 13 May 1926. It was called by the general council of the Trades Union Congress (TUC) in an unsuccessful attempt to force the British government to act to prevent wage reduction and worsening conditions for coal miners”. – Wikipedia

Photo: Oxford University Student Volunteers during the General Strike in an aggressive pose. (Photo by Fox Photos/Getty Images)

A pornographer posing as a fashion photographer sets up a photoshoot with an unsuspecting model, in the hope of getting some illicit footage. He suggests she try wearing something a little more suggestive. (Photo by Pryor/Three Lions/Getty Images). Circa 1955

Two holidaymakers amuse themselves with a porter's trolley whilst waiting for their train at Euston Station, London, 5th August 1939. (Photo by A. J. O'Brien/Fox Photos/Getty Images)

Tsar Alexander II (1818–1881) known as “The Liberator” lying in state. He was mortally wounded by an assassination attack in St Petersburg. (Photo by Hulton Archive/Getty Images). March 1881

Aerial acrobat Schindler, notorious for his foolhardy stunts, practising one of his tricks listing out of the vertical, from a Klemp plane piloted by Richard Perlia. (Photo by General Photographic Agency/Getty Images). Circa 1927

“Nicholas II (Russian: Николай II, Николай Александрович Романов, tr. Nikolay II, Nikolay Alexandrovich Romanov) (18 May [O.S. 6 May] 1868 – 17 July 1918) was the last Emperor of Russia, Grand Prince of Finland, and titular King of Poland. His official title was Nicholas II, Emperor and Autocrat of All the Russias and he is known as Saint Nicholas the Passion-Bearer by the Russian Orthodox Church. Nicholas II, his wife, his son, his four daughters, the family's medical doctor, the Tsar's valet, the Empress' lady-in-waiting and the family's cook were murdered in the same room by the Bolsheviks on the night of 16/17 July 1918”. – Wikipedia

Photo: Tsar Nicholas II (1868–1918) with his wife. (Photo by W. & D. Downey/Getty Images). Circa 1900

President Barack Obama watches as Joey Hudy (L), 14, from Phoenix, Arizona pumps the Extreme Marshmallow Cannon he invented, while touring student science fair projects on exhibit in the State Dining Room at the White House February 7, 2012 in Washington, DC. Obama hosted the second White House Science Fair celebrating the student winners of science, technology, engineering and math (STEM) competitions from across the country. (Photo by Molly Riley-Pool/Getty Images)