A worker pauses for a sandwich, resting on a girder during the construction of a skycraper. (Photo by Hulton Archive/Getty Images). Circa 1930

A chimpanzee feeding a leopard cub at Southam Park Zoo, Warwickshire. (Photo by Ian Tyas/Keystone Features/Getty Images). 1971

A demonstrator attends a protest against fare hikes for city buses in Rio de Janeiro January 16, 2015. Amid a marked economic downturn and high inflation, bus fares went up in Sao Paulo, Brazil's largest city, from 3 to 3.50 reais, and in Rio, the former capital, from 3.0 to 3.40 reais. (Photo by Mauro Pimentel/Reuters)

Classic antique cars are seen at an auto dealer in West Branch, Iowa, March 6, 2015. Iowa, the American heartland. Endless farm fields and quiet towns. 56,273 square miles that are soon to become the focus of the nation as the long process of electing the next U.S. president begins. (Photo by Jim Young/Reuters)

This undated photo provided by the Ford Motor Co. shows the 1948 Lincoln Continental Cabriolet V12. Thirteen years after the last Continental rolled off a Michigan assembly line, Ford Motor Co. is debuting the new Continental in concept form at the New York Auto Show on Monday, March 30, 2015.The production version goes on sale next year. (Photo by AP Photo/Ford Motor Co.)

A view of an entrance to the concrete case surrounding the pressure vessel of the reactor is seen inside the decommissioned Unit Six of the Greifswald nuclear power station outside Lubmin August 5, 2014. Unit Six was a part of East Germany's largest nuclear power plant that was nearly completed in 1990, when the country's re-unification halted construction. (Photo by Thomas Peter/Reuters)

An airplane passes the moon as it makes its approach to Philadelphia International Airport, Sunday, September 7, 2014, in Philadelphia. (Photo by Matt Rourke/AP Photo)