Singer Rihanna prepares for a photoshoot with photographer Annie Leibovitz in Havana, Cuba, May 28, 2015. (Photo by Reuters/Stringer)

The Jet Propulsion Lab team's RoboSimian robot turns on a valve at a simulated disaster-response course during day one of the Defense Advanced Research Projects Agency (DARPA) Robotics Challenge finals in Pomona, California, June 5, 2015. (Photo by David McNew/Reuters)

A female bodybuilder apples oil to another performer backstage before an amateur competition in the Israeli city of Dimona, in this April 3, 2014 file photo. (Photo by Finbarr O'Reilly/Reuters)

A man wearing a water-filled helmet in which a goldfish swims performs an act titled “Aquaman” during the Night Festival 2016 in Singapore, 20 August 2016. The ninth edition of the festival will run from 19 to 27 August and features installations and performances by a range of international and local artists. (Photo by Wallace Woon/EPA)

The Northern Lights glow green in a spectacular light show above a field of trees frozen solid with snow. (Photo by Jaak Sarv/Solent News & Photo Agency)

Iraqis who have fled fighting between security forces and al-Qaida inspired militants in their hometown of Tal Afar arrive in a car at Germawa camp for displaced Iraqis, in a hot dusty plain in the largely-autonomous Kurdish area of Dahuk, 260 miles (430 kilometers) northwest of Baghdad Tuesday, June 17, 2014. (Photo by AP Photo)

Members of the Communist New Fourth Army on parade. Note how the modern equipment contrasts with the shoeless soldiers in the foreground. (Photo by Hulton Archive/Getty Images). 6th July 1946

People fight for the ball as they take part in a mud football match during a festival for celebrating harvest in a village in Jinhua, Zhejiang Province, China September 24, 2017. (Photo by Reuters/China Stringer Network)