A student from the General Yermolov Cadet School performs with models of swords during celebrations of Maslenitsa, or Pancake Week, a pagan holiday marking the end of winter, in southern city of Stavropol, Russia, March 6, 2019. (Photo by Eduard Korniyenko/Reuters)

In this Tuesday, March 12, 2019 photo, a visitor takes part in an immersive experience showing visitors how dogs see from inside the head of a dog at the California Science Center in Los Angeles. A new exhibit at a Los Angeles museum examines the relationship between dogs and humans and explores why the two species seem to think so much alike and get along so well. “Dogs! A Science Tail” opens Saturday, March 16, 2019, at the California Science Center. (Photo by Richard Vogel/AP Photo)

Children watch and react as a T-Rex moves and growls in an inter-active display at Field Station Dinosaurs in Secaucus, N.J on May 25, 2012. There will be 31 types of life-sized dinosaurs displayed at the Jurassic expedition that opens Saturday, May 26. (Photo by Mel Evans/Associated Press)

An employee of the National Park Service takes a selfie with President Barack Obama, left, in the background meeting with the crowd after a tour of Everglades National Park on Earth Day, Wednesday, April 22, 2015, in Florida. Obama used the visit to warn of the damage that climate change is already inflicting on the nation's environmental treasures. (Photo by Lynne Sladky/AP Photo)

A boy and a serviceman pose for a picture during Marines Day celebration in the Black Sea port of Sevastopol, Crimea, November 27, 2016. (Photo by Pavel Rebrov/Reuters)

U.S. players push head coach Adam Krikorian into the pool after they defeated the Netherlands in their women's water polo gold medal match during the Aquatics World Championships in Kazan, Russia, August 7, 2015. (Photo by Michael Dalder/Reuters)

Supporters of the presidential candidate Muhammadu Buhari and his All Progressive Congress hits another supporter with a motorbike during celebrations in Kano, Nigeria March 31, 2015. (Photo by Goran Tomasevic/Reuters)

A coil-shaped Helix Nebula showing a fine web of filamentary “bicycle-spoke” features embedded in the colorful red and blue ring of gas. At 650 light-years away, the Helix is one of the nearest planetary nebulae to Earth. A planetary nebula is the glowing gas around a dying, Sun-like star. (Photo by Reuters/NASA)