Spacewalker Mark Vande Hei took his own photograph during the first spacewalk of 2018, on January 23, 2018. These sky-high pictures are better known as “space-selfies”. (Photo by Mark Vande Hei/NASA)

Rohingya refugee sisters Nur Kaida (R) and Ruhana hug each other at their shelter at the Palongkhali refugee camp near Cox's Bazar, Bangladesh December 21, 2017. (Photo by Marko Djurica/Reuters)

Prince Philip, the Duke of Edinburgh meets members of the cast of “Chicago” during a visit to the Adelphi Theatre in this March 4, 1999 file photo in London, England. (Photo by Anwar Hussein/Getty Images)

Cropped shot of a woman flirtatiously touching leg of man in a suit with her foot under the table. (Photo by LightField Studios/Skyfish Digital Media/Getty Images)

Private Harold L. Langhofer edges into the ball-turret, March 9, 1943. Curled in this position, he can turn the turret so that it fires in any direction. The turret can also be swung around so that the hatch opens into the plane, and the gunner can crawl into it while the Flying Fortress is in motion. (Photo by AP Photo)

A Southwest Airlines jet takes off from Reagan National Airport with a thunderhead to the east on June 20, 2017 in Alexandria, VA. (Photo by Jonathan Newton/The Washington Post)

Bikini Contest in Daytona Beach, Florida, USA. (Photo by Evan Hurd/Sygma/Sygma via Getty Images)

Racegoers in fashionable hats attend Ladies Day at Cheltenham Festival on March 15, 2017 in Cheltenham, England. (Photo by David Davies/PA Wire)