A man wearing a costume dives into a partly frozen lake in Shenyang, in China's northeastern Liaoning province on February 19, 2019. (Photo by AFP Photo/China Stringer Network)

A worker cleans the statue of Yuri Gagarin, the first person who flew to space, ahead of Cosmonautics Day celebrated on April 12, in Moscow, Russia, Wednesday April 10, 2019. Cosmonautics Day marks when Soviet cosmonaut Yuri Gagarin became the first man to fly in space, in 1961, orbiting the earth once before making a safe landing. (Photo by Maxim Marmur/AP Photo)

Sloth “Paula” hangs from a branch in her enclosure at the zoo in Halle an der Saale, eastern Germany, on June 14, 2019. The two-toed sloth celebrated her 50th birthday and is, according to the zoo, the oldest sloth of the world. (Photo by Hendrik Schmidt/dpa/AFP Photo)

Spectators in fancy dress during Day 7 of The Championships – Wimbledon 2019 at the All England Lawn Tennis and Croquet Club on July 8, 2019 in London, England. (Photo by Carl Recine/Reuters)

A demonstrator is detained by riot police during a protest, in La Paz, Bolivia on November 21, 2019. Bolivia's interim President Jeanine Anez asked Congress Wednesday to approve a law that would allow for new elections, after deadly unrest following the resignation of Evo Morales and the disputed October 20 ballot. (Photo by Marco Bello/Reuters)

Gunfire was brought to the steps of President Truman's Washington home, Blair House, as two assassins tried to kill the chief executive, November 1, 1950. One of the gunmen, Oscar Collazzo of New York, lay wounded at the bottom of Blair House's front steps after the president's police guard had finished their work, at the cost of one guards' life, Dec. 9, 1950. The second gunman was killed. (Photo by Harvey Georges/AP Photo)

The Invasion. A quiet street in Macau. Modernization around is quickly changing the city, as documented by Paul Tsui. (Photo by Paul Tsui/National Geographic Travel Photographer of the Year Contest)

Long row of shiny new Flying Fortresses, part of huge reserves being built up in Britain for D-Day, stands by to be flown to combat units as replacements, May 25, 1944. (Photo by AP Photo)