A woman takes part in a four-minute flash mob pillow fight at the Old Town Square in Prague, Czech Republic, December 22, 2016. (Photo by David W. Cerny/Reuters)

A woman carrying an inflatable doll crosses Withy Grove in Manchester, UK on September 11, 2016. Revellers out in Manchester City Centre. (Photo by Joel Goodman/London News Pictures)

A man dressed as Hindu Lord Shiva performs during a religious procession ahead of the Hindu festival of Maha Shivaratri, in Jammu February 23, 2017. (Photo by Mukesh Gupta/Reuters)

A man flies a kite made of 110 Tukkal or paper lanterns for the Hindu festival of “Makar Sankranti”, which marks the start of spring, in Ahmedabad January 13, 2011. (Photo by Amit Dave/Reuters)

This undated photo provided by NOAA in May 2018 shows aurora australis near the South Pole Atmospheric Research Observatory in Antarctica. When a hole in the ozone formed over Antarctica, countries around the world in 1987 agreed to phase out several types of ozone-depleting chemicals called chlorofluorocarbons (CFCs). Production was banned, emissions fell and the hole shriveled. But according to a study released on Wednesday, May 16, 2018, scientists say since 2013, there’s more of a banned CFC going into the atmosphere. (Photo by Patrick Cullis/NOAA via AP Photo)

Pfc. Sebastian Rodriguez, machine gunner, Weapons Platoon, Lima Company, 3rd Battalion, 3rd Marine Regiment, Marine Rotational Force – Darwin, fires an M240 machine gun during a night squad-attack exercise, here, May 22, 2013. (Photo by Sgt. Sarah Fiocco/U.S. Marines)

Remi Bizouard races at the Night of the Jumps freestyle motocross acrobatics at O2 arena on March 16, 2012 in Berlin, Germany. (Photo by Carsten Koall/Getty Images)

Members of the U.S. Army 173rd Airborne Brigade stand at attention as a Ukrainian folk dance group performs at the opening ceremony of the “Rapid Trident” NATO military exercises on September 15, 2014 near Yavorov, Ukraine. The two-week exercises include participating units from a variety of NATO and NATO-associate countries as well as Ukrainian troops. Meanwhile fighting between pro-Russian separatists and Ukrainian armed foces has flared again in eastern Ukraine in a battle for the control of Donetsk airport despite the tenuous ceasefire. (Photo by Sean Gallup/Getty Images)