Aerial view of tourists in life vests and rubber rafts in the Grand Canyon of western Henan, Sanmenxia, China on August 5, 2017. (Photo by Imaginechina/Rex Features/Shutterstock)

A suspected Vietcong is kicked by a Vietnamese soldier holding a rifle as another soldier attempts to tie his hands on October 22, 1965. The prisoner was one of 15 captured October 21 near Xom Chua when government troops raided in the plain of reeds area. Troops killed 43 suspected Vietcong and seized some arms. (Photo by Richard Merron/AP Photo)

A golden pheasant and squirrels are seen in Lushan County of Pingdingshan City, central China's Henan Province, November 14, 2017. (Photo by Liu Xianguo/Xinhua/Barcroft Images)

British fashion model Twiggy plays around on the bumper cars at the Bertram Mills Circus in London, England on January 10, 1967. (Photo by AP Photo)

An Indian student warms up during the 44th Samartha Summer Sports Coaching Camp organized by Shree Samarth Vyayam Mandir in Mumbai, India, 25 April 2018. Mallakhamba arose in the western state of Maharashtra centuries ago. It was originally practiced by wrestlers and soldiers as a strength training exercise. (Photo by Divyakant Solanki/EPA/EFE)

Aerial view of a boat working in the green water of Taihu Lake covered by blue-green algae, Wuxi city, Jiangsu province, China on May 23, 2018. (Photo by Imaginechina/Rex Features/Shutterstock)

Border between Sweden and Norway at Moldusen. An approximately 20-meter wide clearing in the forest separates the two Scandinavian nations, consequently cutting Finnskogen in two. Grue Finnskog 2016. (Photo by Terje Abusdal/The Washington Post)

Birds sit on the back of a zebra in the Nairobi National Park, near Nairobi, Kenya, November 21, 2018. (Photo by Baz Ratner/Reuters)