A Russian trenchmortar crew run to take up a new firing position in the Stalingrad area during the Great Patriotic War. (Photo by Keystone/Getty Images). October 1942

Pod of dolphins surf effortlessly through the waves in the wild traveling at speeds up to 20 mph. (Photo by Greg Huglin)

A mahout (elephant driver) walks a baby elephant across the city streets at night September 27, 2008 in Bangkok, Thailand. (Photo Paula Bronstein/Getty Images)

A refugee sits in front of a Greek riot police cordon during a protest at the Greek-Macedonian border, near the Greek village of Idomeni, March 1, 2016. (Photo by Alexandros Avramidis/Reuters)

Londoners enjoy a “Silent Night” as Big Ben falls silent, London, UK on August 21, 2017. ose Allerston from Clapham, London said “After a stressful day in the office, I couldn't think of anything better than going home and climbing into bed – but when I saw this bed opposite Big Ben I just couldn't resist getting in for a snuggle”. (Photo by Imagewise Ltd/Rex Features/Shutterstock)

People fancy dressed as “Catrina” take part in the “Catrinas Parade” along Reforma Avenue, in Mexico City on October 22, 2017. Mexicans get ready to celebrate the Day of the Dead highlighting the character of La Catrina which was created by cartoonist Jose Guadalupe Posada, famous for his drawings of typical local, folkloric scenes, socio- political criticism and for his illustrations of “skeletons” or skulls, including La Catrina. (Photo by Ronaldo Schemidt/AFP Photo)

Visitors look up at mock-ups of dinosaur skeletons inside the Museum of Natural History in Pyongyang on September 28, 2016. (Photo by Ed Jones/AFP Photo)