Boeing B-29 (#10) from the 24th Bomb Squadron, 6th Bomb Group after an emergency landing at Iwo Jima on April 24,1945. (Photo by U.S. Air Force)

Soviet cosmonaut and the first man to travel in space, Yury Alekseyvich Gagarin (1934–1968) arriving in London for a Russian trade fair. (Photo by Douglas Miller/Getty Images)

Caroline Wozniacki of Denmark serves in her match against Kaia Kanepi of Estonia during day four of the Toray Pan Pacific Open at Ariake Colosseum on September 28, 2011 in Tokyo, Japan. (Photo by Koji Watanabe/Getty Images)

A pilot inflates a hot air balloon while taking part in the 38th International Balloon Festival of Chateau-d'oex, Switzerland, 23 January 2016. The festival takes place from 23 to 31 January. (Photo by Vincent Vannay/EPA)

The sun rises beside St Mary's Lighthouse in Whitley Bay, Tyne and Wear, as the unseasonably cool weather continues on Thursday, April 28, 2016. (Photo by Owen Humphreys/PA Wire)

A coach wipes away tears and comforts a girl who was feeling tired during gymnastics lessons at the Shanghai Yangpu Youth Amateur Athletic School in Shanghai, China, May 4, 2016. (Photo by Aly Song/Reuters)

A horse grazes on railway tracks near the old train station on the the Northeast railroad (Ferrovia do Nordeste) in the city of Missao Velha, Ceara state, northeastern Brazil, October 25, 2016. (Photo by Ueslei Marcelino/Reuters)

NEPAL: A devotee is smeared with a vermillion powder while celebrating the “Sindoor Jatra” vermillion powder festival at Thimi, in Bhaktapur, Nepal, April 14, 2016. (Photo by Navesh Chitrakar/Reuters)