Vietnamese female traffic police officers march during a rehearsal for a military parade as part of the 40th anniversary of the fall of Saigon in southern Ho Chi Minh City (formerly Saigon City), Vietnam, on April 26, 2015. Vietnam marks the 40th anniversary of the fall of Saigon on April 30, the event that ended a war that lasted over 30 years, killing up to four million Vietnamese, the Vietnamese government said, and more than 58,000 U.S troops, the U.S. Department of Defense has said. (Photo by Reuters/Kham)

A weeping South Vietnamese mother and her three children are shown on the deck of this amphibious command ship being plucked out of Saigon by U.S. Marine helicopters in Vietnam, April 29, 1975. (Photo by AP Photo)

A man sledges on Primrose Hill with his daughter and their dog on February 5, 2012 in London, England. The United Kingdom is experiencing heavy snowfall with many areas affected. (Photo by Peter Macdiarmid/Getty Images)

Actor Robert De Niro presents the Guy Movie Hall of Fame award onstage during Spike TV's 5th annual 2011 “Guys Choice” Awards at Sony Pictures Studios on June 4, 2011 in Culver City, California. (Photo by Kevin Winter/Getty Images)

A concept illustration of the world's first forest in the sky, the Bosco Verticale green twin towers currently under construction in Milan, Italy. Towering over the city skyline the world's first forest in the sky will be a sight to behold. With tree equal to one hectare of forest spanning 27 floors these 365 and 260 foot emerald twin towers will be home to an astonishing 730 trees, 5,000 shrubs and 11,000 ground cover plants. (Photo by Boeri Studio)

The galactic centre of the Milky Way glows brightly in the clear night sky above the lighthouse at Portland Bill on the Dorset Jurassic Coast, United Kingdom on April 13, 2021. (Photo by Graham Hunt/Alamy Live News)

A meteorite of the swarm of meteorites Perseida flies above the Ujudvar TV Tower as seen from Ujudvar, Hungary, late Friday, August 13, 2021. Perseidas, one of the brightest meteorite swarms, consist of a multitude of stellar particles which due to their high speed glow up and burn by entering Earth's atmosphere. (Photo by Gyorgy Varga/MTI via AP Photo)