Two men using an electric power saw to fell a tree circa 1940's. (Photo by Keystone View/FPG/Getty Images)

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

A Viet Cong suspect holds his hands up after a Vietnamese Ranger from the 21st Vietnam Infantry Division routed him from his hiding place. (Photo by Keystone/Getty Images). 7th November 1967

1974: American boxer Muhammad Ali, formerly Cassius Clay, strikes an aggressive pose at a press conference on November 29, 1974. (Photo by Harry Dempster/Express/Getty Images); American actor Will Smith at the Royal Premiere of the film Ali in London on December 11, 2001. Smith starred as Muhammad Ali in the film. (Photo by Dave Hogan/Getty Images)

A couple walks across the Francis Scott Key Bridge as the setting sun lights up the clouds in Washington, Friday, October 30, 2020. (Photo by J. David Ake/AP Photo)

In this timed-exposure night photo taken early on February 12, 2017, Mount Sinabung volcano spews reddish smoke and ash, as seen from the Karo district in North Sumatra province. Activity levels have increased in the past week, with Sinabung shooting hot ash clouds into the sky dozens of times, according to the local volcano monitoring agency. (Photo by AFP Photo/Stringer)

High-flying photographer Jeffrey Milstein, renowned for his aerial photos of US cities, snaps landmarks through the open door of a helicopter. This month he hired a chopper in London and amazingly he had just an hour to cover all the buildings he wanted to capture including Buckingham Palace, the London Eye, the glass roof of the British Museum and the Gherkin and Walkie Talkie towers in the City. Here: Jeffrey Milstein captured these stunning images through the door of a helicopter hovering over central London. (Photo by Jeffrey Milstein/Rex Features/Shutterstock)

A girl dives under a wave at Bondi Beach as temperatures reached 29 degrees celsius on December 17, 2020 in Sydney, Australia. The Bureau of Meteorology predicted the arrival of thunderstorms and showers later today with a southerly change bringing possible severe storms around the Sydney region. (Photo by Mark Evans/Getty Images)