Nazi dictator Adolf Hitler greets supporters at a May Day gathering in the Olympic Stadium, Berlin. (Photo by Keystone). 1st May 1938

Afghan air force 2nd Lt. Niloofar Rhmani walks the flight line at Shindand Air Base, Afghanistan, prior to her graduation from undergraduate pilot training, on May 13, 2013. Rhmani made history on May 14, when she became the first female to successfully complete undergraduate pilot training and earn the status of pilot in more than 30 years. She will continue her service as she joins the Kabul Air Wing as a Cessna 208 pilot. (Photo by Senior Airman Scott Saldukas/USAF)

A visitor stands in front of a portrait taken by artist Bruce Gilden at the “Masters of Photography” exhibition at the Photokina trade fair in Cologne on September 20, 2016. The fair for the photographic and imaging sector, that is running from September 20 to 25, 2016, presents products from image capture, image processing and storage to image output. Photokina also includes a program of events with congresses, workshops, symposiums and photography exhibitions. (Photo by Patrik Stollarz/AFP Photo)

Crowds look on as the super moon rises behind the Fremantle War Memorial at Monument Hill on November 14, 2016 in Fremantle, Australia. A super moon occurs when a full moon passes closes to earth than usual, with the November 14th moon expected to be closer than it has been in over 70 years. (Photo by Paul Kane/Getty Images)

Humanoid robots compete in a group match of the 20th RoboCup in Leipzig, Germany, June 30, 2016. About 3,500 participants from 45 countries and regions compete in the robot world championship until 04 July. (Photo by Sebastian Willnow/EPA)

A girl walks an Akita-inu dog dressed in a military uniform in Vladivostok, Russia on April 9, 2019. (Photo by Yuri Smityuk/TASS)

Life reconstruction of the new oviraptorosaurian dinosaur species Anzu wyliei in its 66 million-year-old environment in western North America as seen in an undated handout illustration by Mark A. Klinger, Carnegie Museum of Natural History. Some 18,000 species, great and small, were discovered in 2014, adding to the 2 million already known, scientists said on May 21, 2015 as they released a “Top 10” list that highlights the diversity of life. Anzu wyliei, one of the top 10, dubbed “the chicken from hell”, is extinct. The feathered dinosaur whose partial skeletons were unearthed in the Dakotas was a contemporary of T. rex and Triceratops. (Photo by Mark A. Klingler/Reuters/Carnegie Museum of Natural History)

Andrea Petkovic of Germany in action against Sara Errani of Italy during day one of the Mutua Madrid Open tennis tournament at the Caja Magica on May 3, 2014 in Madrid, Spain. (Photo by Julian Finney/Getty Images)