Forward engine room of the USS Drum, a Gato-class submarine at Battleship Memorial Park, Mobile, Alabama (© Warren Weinstein/Getty Images)

A nesting colony of king penguins in South Georgia, Antarctica (© Ralph Lee Hopkins/National Geographic/Offset)

Looking inland from Ponce de León Inlet toward the lighthouse, Florida (© Jason Sponseller/Shutterstock)

Rainbow at Victoria Falls in Zambia (© Dietmar Temps/Shutterstock)

Pronghorn buck (© Donald M. Jones/Minden Pictures)

Green tree frog and water lily, Lake Kissimmee, Florida (© Joanne Williams/Danita Delimont)

Cherry blossoms and Himeji Castle in Himeji, Japan (© Tororo/Getty Images)

The 2017 April full moon, or pink moon, rises over St. Michael's Mount, Cornwall, England (© Simon Maycock/Alamy Live News)

Aerial view of Santorini, Greece (© Amazing Aerial Agency/Offset)

A pod of narwhals near Baffin Island, Nunavut, Canada (© Eric Baccega/Minden Pictures)

Kermode bear cub siblings huddling in Canada's Great Bear Rainforest, British Columbia (© Ian McAllister/Offset)

European rabbit kit greeting its parent, France (© Remy Courseaux/Minden Pictures)

Floating temples of Wat Chaloem Phra Kiat Phrachomklao Rachanusorn in Lampang province, Thailand (© pa_YON/Getty Images)

Pantropical spotted dolphins off the coast of Ixtapa, Mexico (© Christian Vizl/Tandem Stills + Motion)

Artist Laura Buckley with her mixed-media sculpture 'Fata Morgana,' Saatchi Gallery, London (© Stephen Chung/Alamy)

Sipapu Bridge in Natural Bridges National Monument, Utah (© Fyletto/Getty Images)

Ruffed grouse in Algonquin Provincial Park, Ontario, Canada (© Jim Cumming/Getty Images)

Vernal Fall in Yosemite National Park, California (© elvistudio/Shutterstock)

Milky Way over Neist Point Lighthouse, Isle of Skye, Scotland (© Shaiith/Getty Images)

Keukenhof in Lisse, Netherlands (© Jim Zuckerman/Getty Images)

The Grand Prismatic Spring in Yellowstone National Park, Wyoming (© Martin Rügner/DEEPOL by plainpicture)

Te Matua Ngahere, a giant kauri tree growing in the Waipoua Forest, North Island, New Zealand (© Kim Westerskov/Getty Images)

Male king eider ducks swimming in Troms og Finnmark, Norway (© Pal Hermansen/Minden Pictures)

The Large Magellanic Cloud, photographed by the Hubble Space Telescope (© ESA/Hubble/NASA)

Southern rockhopper penguins on the Falkland Islands (© Heike Odermatt/Minden Pictures)

Sunset at Ruby Beach in Olympic National Park, Washington state (© Adam Mowery/Tandem Stills + Motion)

South American tapir calf trots through the grass (© Nick Fox/Shutterstock)

Salisbury Cathedral with flock of grazing sheep, England (© Slawek Staszczuk Photo/Alamy)

A tractor kicks up dust while tilling fields on the Palouse near Pullman, Washington (© Ben Herndon/Tandem Stills + Motion)

Hoary redpoll nest in Lapland, Finland (© Maximilian Buzun/Alamy)