Soldier boys at Fort Dix, N.J., learn something about guns during their working hours, as they show their girlfriends at a camp dance, December 13, 1940. In front row, playing with the coin amusement gun, from left: Pvt. Tom D'Amato of West Orange; Rose Sinkewicz, behind gun site, of Trenton; Julia Ivans of Trenton, and Pvt. Vernon Landers of Kearney. Back row: Pvts. William Sargent and William Corlies of Philadelphia. (Photo by AP Photo)

British theoretical physicist Stephen Hawking, Cambridge University Professor and Fellow, circa 1985. Stephen Hawking, the brightest star in the firmament of science, whose insights shaped modern cosmology and inspired global audiences in the millions, has died aged 76. (Photo by Gemma Levine/Getty Images)

South Vietnamese forces escort suspected Viet Cong officer Nguyen Van Lem (also known as Bay Lop) on a Saigon street February 1, 1968, early in the Tet Offensive. Moments later, Lem was executed by Gen. Nguyen Ngoc Loan, chief of the national police. (Photo by Eddie Adams/AP Photo)

Kenyan riot police officers raise batons over a man during a demonstration of Kenya's opposition supporters in Nairobi, on May 16, 2016. Opposition protestors led by former Prime Minister Raila Odinga gathered outside the Indepedent Electoral and Boundaries Comission building to demand the dismissal of IEBC commissioners, after alleged bias towards the ruling Jubillee Alliance Party. (Photo by Carl De Souza/AFP Photo)

Young girls attend a training session in MGFSO Olympic reserve school in Moscow on May 30, 2016. (Photo by Kirill Kudryavtsev/AFP Photo)

“Chewbacca Mom” Candace Payne attends the 2016 CMT Music awards at the Bridgestone Arena on June 8, 2016 in Nashville, Tennessee. (Photo by Kevin Mazur/WireImage)

In this Wednesday, June 8, 2016 photo, Joe Giles, an actor portraying a zombie in “The Walking Dead”, poses with social media reporter Danielle Datu during a walker boot camp at Universal Studios Hollywood in Los Angeles. (Photo by Jae C. Hong/AP Photo)

Skulls are seen at the witch doctor kiosk during the day of offerings to the “Pachamama” (Mother Earth) in El Alto, Bolivia, August 1, 2016. Pachamama is a goddess revered by the indigenous people of the Andes. She is also known as the earth/time mother. In Inca mythology, Pachamama is a fertility goddess who presides over planting and harvesting, embodies the mountains, and causes earthquakes. (Photo by David Mercado/Reuters)