Soldier boys at Fort Dix, N.J., learn something about guns during their working hours, as they show their girlfriends at a camp dance, December 13, 1940. In front row, playing with the coin amusement gun, from left: Pvt. Tom D'Amato of West Orange; Rose Sinkewicz, behind gun site, of Trenton; Julia Ivans of Trenton, and Pvt. Vernon Landers of Kearney. Back row: Pvts. William Sargent and William Corlies of Philadelphia. (Photo by AP Photo)

Members of the SubCielo company perform during the fifth annual Puerto Rico Circo Fest in San Juan, Puerto Rico, Saturday, March 10, 2018. The festival is held simultaneously in several spots on the streets of the Old San Juan city on March 10–11. (Photo by Ricardo Arduengo/AFP Photo)

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)

Dancers from Tokyo wearing traditional costumes perform during a celebration event, a day before Japan's Emperor Naruhito and Empress Masako's royal parade in front of the Imperial Palace in Tokyo, Japan November 9, 2019. (Photo by Issei Kato/Reuters)

A woman cleans her boat after a snowfall in Srinagar, December 13, 2019. (Photo by Danish Ismail/Reuters)

A relative of a victim of the Ukraine International Airlines PS 752 plane that crashed after taking off from Tehran's Imam Khomeini airport reacts at Boryspil International Airport, outside Kiev, Ukraine on January 8, 2020. (Photo by Serhii Nuzhnenko/Reuters)

Regrowth of plants is seen in bushland that was destroyed by bushfires, in Kulnura, New South Wales, 15 January 2020. (Photo by Joel Carrett/EPA/EFE/Rex Features/Shutterstock)

Blaze, 8, from Swindon, is covered from head to toe as he plays in the mud at Weston-super-Mare beach on August 4, 2019, as the tide recedes and the huge expanse of mud flats cover the beach where holidaymakers enjoy splashing around. (Photo by Ben Birchall/PA Images via Getty Images)