Medic James E. Callahan of Pittsfield, Mass., gives mouth-to-mouth resuscitation to a dying soldier in war zone D, about 50 miles northeast of Saigon, June 17, 1967. Thirty-one men of the 1st Infantry Division were reported killed in the guerrilla ambush, with more than 100 wounded. (Photo by Henri Huet/AP Photo)

Children of the Roma community play as they cool off in a fountain in the main square of Pristina, Kosovo on June 14, 2017. (Photo by Armend Nimani/AFP Photo)

Public Space series, 2015. This series by Morteza Niknahad and Behnam Zakeri tends toward cinema, taking an almost cartoonish view of modern life in Iran. This work was inspired by the social life of dolphins. (Photo by Morteza Niknahad and Behnam Zakeri/The Guardian)

A cyclist drives past a flowering rapeseed field not far from the small Bavarian village of Schoengeising, near Munich, during a nice, warm sunny weather day on May 17, 2017. (Photo by Christof Stache/AFP Photo)

Men carrying a shrine jump over a bon fire, which means a wish for good luck during a traditional Chinese lunar new year celebration in Jieyang, Guangdong province, China, February 2, 2017. (Photo by Reuters/China Daily)

In this February 19, 2017 photo, a couple dances during the “If you don't give me....then you lend me” Carnival street party on Ipanema beach, in Rio de Janeiro, Brazil. The typical view of Carnival in Brazil is anything goes, with no headdress too big, no outfit too small, no song too ribald, but this year some organizers of the world's best known party are drawing the line at lyrics that are sexist, homophobic or racist. (Photo by Silvia Izquierdo/AP Photo)

Sеx worker Geraldine, wearing cat make-up, excitedly holds up a dress she is thinking of buying from a street vendor, so that her partner, sitting nearby to keep her company, can see it, as she waits for clients outside the Revolution subway station, in Mexico City, Saturday, March 13, 2021. According to Geraldine, 30, the pandemic has cut clients and increased risks to the sеx workers but has also brought out more assistance for them too, both from dedicated organizations such as the activist group Brigada Callejera or “The Street Brigade” and from individuals who have donated food or clothing. (Photo by Rebecca Blackwell/AP Photo)

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)