Clearing skies await a tripod-toting photographer looking for a spot to capture the early-morning light at Portland Head Light, Thursday, January 17, 2013, in Cape Elizabeth, Maine. (Photo by Robert F. Bukaty/AP Photo)

A visitor holds up her toy bunny to the aquarium glass in front of Aurora the Russian polar bear at the Sao Paulo Aquarium in Sao Paulo, Brazil, Thursday, April 16, 2015. (Photo by Andre Penner/AP Photo)

It’s enough to make your head spin. The photographer Katherine Young set out to shoot spiral staircases in London, England to great effect, including this shot she calls the Downward Spiral Part III. (Photo by Katherine Young/Rex Features/Shutterstock)

A man performs a split as he practices Kung Fu at Beihai Park in Beijing, China August 20, 2017. (Photo by Reuters/China Stringer Network)

As an American in 1990s Cuba, Tria Giovan risked being branded a traitor. But the photographer continued to visit and, from the dance hall to the hair salon, she captured the resilient spirit of the Cuban people. The 120 images in Tria Giovan’s “The Cuba Archive” are from the period in the 90s when, as an American, travel to Cuba could have seen her branded a traitor, as the country was subject to a US trade embargo. Her trip required lots of planning – and patience. (Photo by Tria Giovan/The Guardian)

These stunning pictures show a normally vicious tiger calmly swimming in a pool of algae, on Jule 9, 2014. The powerful cat takes a refreshing break by taking a dip in the bright green algae. But it looks like this big cat is scared of getting his head wet as he strains to keep it above the water. After splashing around for a bit the tiger gets out and tries to air-dry with specks of the vegetation dripping off his fur. The striking pictures were taken at Copenhagen zoo by snapper Soren Lundgren Neilson. (Photo by Soren Nielsen/Caters News)

Apollo 9 Command/Service Modules (CSM) nicknamed “Gumdrop” and Lunar Module (LM), nicknamed “Spider” are shown docked together as Command Module pilot David R. Scott stands in the open hatch. Astronaut Russell L. Schweickart, Lunar Module pilot, took this photograph of Scott during his EVA as he stood on the porch outside the Lunar Module. Apollo 9 was an Earth orbital mission designed to test docking procedures between the CSM and LM as well as test fly the Lunar Module in the relative safe confines of Earth orbit. (Photo by NASA)

The Northern Lights glow green in a spectacular light show above a field of trees frozen solid with snow. (Photo by Jaak Sarv/Solent News & Photo Agency)