Danielle Collins of the US reacts to a point in the first set while playing Caroline Wozniacki of Denmark during Round Two Women's Singles tennis match of the 2019 US Open at the USTA Billie Jean King National Tennis Center in New York on August 29, 2019. (Photo by Robert Deutsch/USA TODAY Sports)

Young children at a Bristol, Great Britain health centre unsure of the benefits of sun-lamps and the special glasses that must be worn, July 1948. The health centre was part of the newly introduced free National Health Service. (Photo by Popperfoto/Getty Images)

A member of the Tinstix of Dynamite aerobatics team flies in front of a wall of fire during the Australian International Airshow in Melbourne on March 5, 2017. The annual event sees 180,000 visitors over the 3-day public event held at the Avalon Airfield some 80kms south-west of Melbourne. (Photo by Mal Fairclough/AFP Photo)

Ali Asair, who has left his family behind and traveled hundreds of kilometers in search for a pasture for his animals, attends to his camel in a pastoralists' settlement in the Bandarbeyla district in Somalia's semi-autonomous region of Puntland, Somalia, 24 March 2017. According to media reports, the United Nations says only 31 percent of 864 million US dollars appeal for a drought-hit Somalia is funded. The UN said the world is facing the largest humanitarian crisis since 1945, adding that more than 20 million people are facing the threat of famine in Somalia, Yemen, South Sudan and Nigeria and 1.4 million children could die from starvation this year. (Photo by Dai Kurokawa/EPA)

Warriors from the Suri tribe in Ethiopia still stage the savage “Donga” battles – even after many fighters have been died from their injuries. Donga stick fights take place after the harvests, the Surmas count days owing to knots on a long stem of grass or jags on the trunk of a tree dedicated to that specific use. Here: A tribeswoman sporting a huge lip plate and wearing a skinned animal carcass on her head. (Photo by Eric Lafforgue/Exclusivepix Media)

A leaflet denouncing South Korean President Park Geun-hye lies on the ground after it was torn at a protest calling Park to step down, in Seoul, South Korea, November 19, 2016. (Photo by Kim Hong-Ji/Reuters)

Anti-government demonstrators perform in front of burning barricades as they attend a protest against a constitutional amendment, known as PEC 55, that limit public spending, in front of Brazil's National Congress in Brasilia, Brazil, November 29, 2016. (Photo by Adriano Machado/Reuters)

A Pakistani devotee dances to celebrate the three-day annual festival to pay tribute to the famous saint Al-Sheikh Ali Bin Usman Al-Hajveri known as Data Ganjbaksh at outside his shrine in Lahore, Pakistan, Sunday, November 20, 2016. Thousands of people traveled from all over Pakistan to attend the celebrations. (Photo by K.M. Chaudary/AP Photo)