A boy plays on the glass at Thailand's first skywalk in Bangkok, Thailand on November 18, 2018. (Photo by Soe Zeya Tun/Reuters)

A woman poses with a grenade launcher at a weapons exhibition during festivities marking Marines Day in St.Petersburg, Russia, Saturday, November 24, 2018. (Photo by Dmitri Lovetsky/AP Photo)

Boxers Deontay Wilder, left, and Tyson Fury exchange words as they face each other at a news conference in Los Angeles, Wednesday, November 28, 2018. The pair are slated to fight Saturday night for Wilder's WBC heavyweight title. (Photo by Andrew Couldridge/Action Images via Reuters)

N.C. Dezendorf, wife of the general manager of the Electro-Motive division of General Motors, christens the new lightweight “Aerotrain” at the company's locomotive works in La Grange, Ill. on August 22, 1955. (Photo by Edward Kitch/AP Photo)

Indian Air Force officers stretch before taking part in full dress rehearsal for India's Republic Day parade in Kolkata, January 23, 2018. (Photo by Rupak De Chowdhuri/Reuters)

Leslie Cliff and his wife Violet, English figure skating pair. Olympic games of Garmisch-Partenkirchen (Germany), 1936. (Photo by Roger Viollet Collection/Getty Images)

A military police officer aims his gun to a demonstrator during a protest in Brasilia, Brazil, Tuesday, April 7, 2015. The officer had picked up a bottle that was thrown towards them but did not fire his gun and backed away. Thousands of workers have staged rallies in 12 cities across Brazil to protest against a proposed law that would allow companies to outsource their labor force. (Photo by Eraldo Peres/AP Photo)

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)