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 meteorite burns up in the atmosphere as seen in this photo taken near of Salgotarjan, 109 kms northeast of Budapest, Hungary, late 21 April 2015. The Moon and Venus can be seen on the left. (Photo by Peter Komka/EPA)

A dog with a cherry blossom-shaped pin, is seen in the cherry blossom festival in Seoul, South Korea, Sunday, April 9, 2017. (Photo by Lee Jin-man/AP Photo)

People dressed as ancient Roman reflect on a helmet during a parade to mark the anniversary of the foundation of Rome in 753 BC, on April 23, 2017 in Rome, Italy. (Photo by Alberto Pizzoli/AFP Photo)

Laborers lay down upon a field to cut off the tulips that remained uncut by the tractor in Den Helder, Netherlands April 22, 2017. (Photo by Cris Toala Olivares/Reuters)

Racegoers attend day one of The Randox Health Grand National Festival at Aintree Racecourse on April 12, 2018 in Liverpool, England. (Photo by News Group Newspapers Ltd)

Brazilian singer Anitta performs during the show of the Agua de Coco collection at Sao Paulo Fashion Week in Sao Paulo, Brazil, Saturday, April 21, 2018. (Photo by Andre Penner/AP Photo)

Festivalgoers during the 2018 Coachella Valley Music And Arts Festival at the Empire Polo Field on April 20, 2018 in Indio, California. (Photo by Frazer Harrison/Getty Images for Coachella)