A reveller of the Salgueiro samba school performs during the second night of Rio's Carnival at the Sambadrome in Rio de Janeiro, Brazil, on February 13, 2018. (Photo by Mauro Pimentel/AFP Photo)

A reveller from Salgueiro performs during the second night of the Carnival parade at the Sambadrome in Rio de Janeiro, Brazil on February 13, 2018. (Photo by Sergio Moraes/Reuters)

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)

In this Thursday, January 28, 2016 photo, a “child angel” doll sits on a chair in Bangkok, Thailand. The dolls, which are said to bring good luck to their owners, became a media sensation this week after a leaked memo from a Thai budget airline gave pointers on how they could be treated like passengers if they have a paid-for seat. Thai people are superstitious, and the doll phenomenon has been analyzed as a modern version of a traditional totem containing real body parts, but as a fad it seems have more in common with Furby dolls. (Photo by Sakchai Lalit/AP Photo)

A Free Syrian Army fighter walks past a flag of al-Furqan brigade as a rifle hangs from a branch in the orchards of Kafar Zita in Hama countryside January 22, 2015. (Photo by Mohamad Bayoush/Reuters)

A clothing shop displays its merchandise in the rebel-controlled city of Idlib, Syria November 7, 2015. (Photo by Ammar Abdullah/Reuters)

A participant, riding a horse and dressed as a knight, presents flowers to women during an event marking Valentine's Day in central Moscow, Russia, February 14, 2016. (Photo by Maxim Zmeyev/Reuters)