American robin perched on a branch in Canada (© marcophotos/Getty Images)

Blue icebergs near Cuverville Island, Antarctica (© Mike Hill/Getty Images)

Dall sheep rams at Polychrome Pass, Denali National Park, Alaska (© Patrick J. Endres/Getty Images)

Autumn leaves coated with frost (© sagarmanis/Getty Images)

Mother cheetah and her cub in the Masai Mara National Reserve, Kenya (© gudkovandrey/Adobe Stock)

The Salzach River in Salzburg, Austria (© MacEaton/Alamy)

An 1840 design for the Analytical Engine by Charles Babbage (© Science & Society Picture Library/Getty Images)

US Navy sailors on the WWII museum ship USS Bowfin in Honolulu, Hawaii (© US Navy Photo/Alamy)

Petrified Forest National Park, Arizona, USA (© Ian Shive/Tandem Stills + Motion)

Glowworms in Blue Mountains National Park, Australia (© Leelakajonkij/Getty Images)

Arctic fox in Dovrefjell-Sunndalsfjella National Park, Norway (© Andy Trowbridge/Minden Pictures)

The shadow of Mount Everest over the western Himalayas in Nepal (© Kent Karvey/KH Films, Inc./Tandem Stills + Motion)

Wicker fields in Cañamares, Spain (© David Santiago Garcia/Alamy)

Old Town and El Panecillo Hill in Quito, Ecuador (© Karol Kozlowski/plainpicture)

The chapel and hermitage of Santa Justa in Cantabria, Spain (© Luis Miguel Martin/Getty Images)

The English National Ballet's 2016 production of 'The Nutcracker' at the London Coliseum in London, England (© Robbie Jack/Corbis via Getty Images)

Iron Hill, Town of Brome Lake, Quebec, Canada (© plainpicture/Design Pics/David Chapman)

The December full moon seen through holiday lights (© Jesus Merida/Getty Images)

Aurora borealis above the Brooks Range in Alaska (© Noppawat Tom Charoensinphon/Getty Images)

Performers from the Ministry of Fun Santa School in London, England (© Matt Dunham/AP Photo)

Sunlight in the forest of Western Siberia, near the city of Raduzhny, Russia (© Leonid Ikan/Shutterstock)

Winter scene illuminated on the Palais de l'Isle in Annecy, Haute Savoie, France (© blickwinkel/Alamy)

Two young male polar bears, Churchill, Manitoba, Canada (© Cheryl Ramalho/Getty Images)

Christmas tree at Weissensee, a small lake near Ehrwald in Tyrol, Austria (© nagelestock/Alamy)

Trees on the northern slope of Mount Khomyak in the Carpathian Mountains, Ukraine (© panaramka/Getty Images)

Royal Pavilion Ice Rink in Brighton, England (© Chris Gorman/Getty Images)

Snow buntings flock during a snowstorm in New York (© Marie Read/Minden Pictures)

Kjell Henriksen Observatory in Svalbard, Norway (© Vincent Fournier/Gallery Stock)

Mountain goats in the Yukon, Canada (© Mark Newman/Getty Images)

Westerheversand Lighthouse in Westerhever, Germany (© Sandra Bartocha/Minden Pictures)

Bonfire to celebrate New Year's Eve in 2014 in Reykjavik, Iceland (© Ragnar Th Sigurdsson/Alamy)