Alex Plunkett, left, and Sean Hart, both of Arlington, Va., join hundreds participating in the annual International Pillow Fight Day on April 5. Massive pillow fights broke out on the Mall in Washington and in cities around the world. (Photo by Marvin Joseph/The Washington Post)

A Perseid meteor streaks across the sky above Inspiration Point early on August 12, 2016 in Bryce Canyon National Park, Utah. The annual display, known as the Perseid shower because the meteors appear to radiate from the constellation Perseus in the northeastern sky, is a result of Earth's orbit passing through debris from the comet Swift-Tuttle. (Photo by Ethan Miller/Getty Images)

A Vietnamese cosplayer poses as police officer character from the game during the League of Legends (LOL) Mid-Season Invitational 2019 play-in group stage, in GG Stadium, Ho Chi Minh, Vietnam May 5, 2019. (Photo by Reuters/Kham)

This image made available by the Johns Hopkins University Applied Physics Laboratory on Wednesday, May 31, 2017 depicts NASA's Solar Probe Plus spacecraft approaching the sun. On Wednesday, NASA announced it will launch the probe in summer 2018 to explore the solar atmosphere. It will be subjected to brutal heat and radiation like no other man-made structure before. (Photo by Johns Hopkins University Applied Physics Laboratory via AP Photo)

“Aurora over a glacier lagoon”. A vivid green overheaded aurrora pictured in Iceland's Vatnajokull National Park reflected almost symetrically in Jokulsrlon Glacier lagoon. A complete lack of wind and currrent combin in this sheltred lagoon scene to crete an arresting mirror effect giving the image a sensation of utter stillness. Despite theis there is motion on a suprising scale, as the loops and arcs of the aurora are shaped by the shifting forces of the Earth's magnetic field. James Woodend of Great Britain won the grand prize with the image, beating out more than 2,500 other entries. The Astronomy Photographer of the Year 2014 contest is judged by the Royal Observatory Greenwich and BBC Sky at Night magazine. (Photo by James Woodend/The Astronomy Photographer of the Year 2014 Contest)

An image produced by the Hubble telescope of the perfectly “edge-on” galaxy, or NGC 4013, March 1, 2001. This new Hubble picture reveals, with great detail, huge clouds of dust and gas extending along, as well as far above, the galaxy's main disk. NGC 4013 is a spiral galaxy, similar to the Milky Way, lying some 55 million light-years from Earth in the direction of the constellation Ursa Major. Viewed face-on, it would look like a nearly circular pinwheel, but NGC 4013 happens to be seen edge-on from our vantage point. Even at 55 million light-years, the galaxy is larger than Hubble's field of view, and the image shows only a little more than half of the object, albeit with unprecedented detail. (Photo Courtesy of NASA/Newsmakers)

“Show us our butts! Mucawana tribe – Angola. In Soba village, the Muhacaona (Mucawana) tribe, perhaps the best place i have visited. They use cow dung and fat to make this so nice haircut, and love the beads. They asked me to make pictures of their backs... and butts to see on the camera screen if everything was perfect!”. (Photo and comments by Eric Lafforgue)

Carlos Melendez prepares to feed his pet squirrel “Colita” in downtown San Salvador January 29, 2015. (Photo by Jose Cabezas/Reuters)