What makes a watch the most valuable in the world? It’s supercomplicated – literally. In 1925 banker Henry Graves Jr. (considered the greatest watch collector of the 20th century) commissioned Patek Philippe to create a unique gold pocket watch. When Graves finally received it – eight years later – it was the most complex timepiece ever created by human hands... (Photo by Suzanne Plunkett/Reuters)

British theoretical physicist Stephen Hawking, Cambridge University Professor and Fellow, circa 1985. Stephen Hawking, the brightest star in the firmament of science, whose insights shaped modern cosmology and inspired global audiences in the millions, has died aged 76. (Photo by Gemma Levine/Getty Images)

A female rebel in Kabul, Afghanistan, circa 1979. Photo taken at a parade in Kabul in honor of the pro-Communist Saur Revolution. She was from the women’s battalion of the people’s militia (one of the anti-imperial groups that participated in the coup d’etat). (Photo by Viktor Khabarov)

A new monorail service in Houston, Texas, ready for its inaugural service. (Photo by Evans/Three Lions/Getty Images). Circa 1950

A policeman stands by a burning car, set alight during a communist march in the East End of London. (Photo by Topical Press Agency/Getty Images). Circa 1936

Shepherds from the north wear their traditional heavy woollen mantles as they stand ready to shear sheep with sycthe-like shears. (Photo by Three Lions/Getty Images). Circa 1952

Looking towards the Times Building on Times Square, the Paramount Building is on the right, and Seventh Avenue on the left crossing Broadway. (Photo by General Photographic Agency/Getty Images). Circa 1930

A cameraman films “Diana And Callisto” (circa 1556-59) oil painting by Venetian artist Titian as it goes on display for the first time at the National Gallery on March 1, 2012 in London, England.(Photo by Dan Kitwood/Getty Images)