Polar bear cubs playing in Kaktovik, Alaska (© Martin Smart/Alamy)

A mountain hare hunkers down in a snowstorm in the Cairngorms, Scotland (© Lyle McCalmont/Getty Images)

'Field of Light at Sensorio,' by Bruce Munro, Paso Robles, California (© George Rose/Getty Images)

Dolwyddelan Castle, Snowdonia National Park, Conwy, Wales (© Sebastian Wasek/Sime/eStock Photo)

拉斯拉哈斯的穴居鹦鹉，阿根廷 (© Cagan Hakki Sekercioglu/Getty Images)

Burrowing parrots in Las Lajas, Argentina (© Cagan Hakki Sekercioglu/Getty Images)

Trakai Island Castle Museum in Trakai, Lithuania (© Andrius Aleksandravicius/Alamy)

Jupiter and its moons Io, Europa, Ganymede, and Callisto (© Branko Šimunek/Alamy)

Tianmen Mountain near Zhangjiajie, China (© Bogdan Dyiakonovych/Shutterstock)

Muir Woods National Monument near San Francisco, California (© Mia2you/Shutterstock)

City lights from the snowy peak of Grouse Mountain at twilight, Vancouver, BC, Canada (© Pierre Leclerc Photography/Getty Images)

Trakai Island Castle Museum in Trakai, Lithuania (© Andrius Aleksandravicius/Alamy)

Der Eibsee am Fuß der Zugspitze, Bayern, Deutschland (© Marc Hohenleitner/Huber/eStock Photo)

Windmills in the province of Toledo, Spain (© Jon Arnold/Danita Delimont)

Male muskoxen near Prudhoe Bay in Alaska (© Oliver Smart/Alamy)

Beach in the evening light at Whisky Bay, Wilsons Promontory National Park, Victoria, Australia (© Michael Breitung/Huber/eStock Photo)

Sunset in Val Gardena in the Dolomites of South Tyrol, Italy (© Marco Capellari/Getty Images)

A Brandt's cormorant hunts for a meal in a school of Pacific mackerel beneath an oil rig off the coast of Los Angeles, California (© Alex Mustard/Minden Pictures)

Gypsum sand dunes, White Sands National Park, New Mexico (© Grant Kaye/Cavan Images)

Backcountry adventurer Alex Peterson speed riding on the south side of Mount Hood, Oregon (© Richard Hallman/DEEPOL by plainpicture)

Eurasian red squirrel in the Cairngorms, Highlands of Scotland (© Images from BarbAnna/Getty Images)

Northern lights near Whitehorse in Yukon, Canada (© Design Pics/Danita Delimont)

Zebras and wildebeests in the Serengeti National Park, Tanzania (© Raffi Maghdessian/Cavan Images)

Sunlit ridges against volcanic scree on Eyjafjallajökull, a volcano in Iceland (© Erlend Haarberg/Minden Pictures)

Red lanterns hanging on branches (© bingdian/iStock/Getty Images Plus)

Tree frog in Cadiz, Spain (© Andres M. Dominguez/Minden Pictures)

View of New York City from the International Space Station (© NASA Photo/Alamy)

Aerial view of the glaciers and mountains of Kluane National Park and Reserve, near Haines Junction, Yukon, Canada (© Robert Postma/plainpicture)

Semuc Champey, a nature park in Guatemala (© Joel Sharpe/Getty Images)

Aerial view of car crossing over the frozen surface of Lake Baikal, Russia (© Amazing Aerial Agency/Offset)

A reddish egret hunts in Fort De Soto Park, Florida (© Brian Lasenby/Getty Images)