Emperor penguin chicks on Snow Hill Island, Antarctica (© Paul Souders/Corbis)(Bing United States)

Christmas tree at Rockefeller Center, New York City, New York (© age fotostock/SuperStock)(Bing United States)

Light microscopy of Volvox colonies (© Corbis Motion)(Bing United States)

A billabong in Wooleen Station, Western Australia (© Davide Scagliola/Aurora Photos)(Bing United States)

Marines and sailors aboard the USS Pearl Harbor dock landing ship during the 2011 ceremony commemorating the 70th anniversary of the attack on Pearl Harbor (© Super Nova Images/Alamy)(Bing United States)

Lechwe running in the Okavango Delta floodplain in Botswana (© Sergey Gorshkov/Minden Pictures)(Bing United States)

Charles Babbage (Father of the Computer) difference engine, Science Museum, London, United Kingdom (© Steven Vidler/Corbis)(Bing United States)

Botany Bay Road, Edisto Island, South Carolina (© Michael Woloszynowicz/500px)(Bing United States)

Edinburgh Castle, Scotland (© Raul Belinchon/Gallery Stock)(Bing United States)

Poinsettia plants under cultivation in a greenhouse (© SGM/Stock Connection/Aurora Photos)(Bing United States)

Middle spotted woodpecker and blue tit (© Naturfoto-Online/Alamy)(Bing United States)

Snow on the Great Wall, Beijing, China (© Panorama Stock)(Bing United States)

Mural in Cape Town, South Africa, illustrating anti-apartheid activist and former president of South Africa Nelson Mandela (© Frederic Soltan/Corbis)(Bing United States)

Reindeer in the countryside near Karasjok, Finnmark, Norway (© GS/Gallery Stock)(Bing United States)

Kenai Peninsula, Alaska (© GeoStills/Alamy)(Bing United States)

Common redpoll in Greater Sudbury, Ontario, Canada (© Don Johnston/Corbis)(Bing United States)

Dry stone walls and stone barn at Littondale, Yorkshire Dales, North Yorkshire, England (© David Speight/Alamy)(Bing United States)

Avenue des Champs-Élysées, Paris, France (© tpgimages/Panorama Stock)(Bing United States)

Eurasian red squirrel, Scotland (© Jules Cox/Minden Pictures)(Bing United States)

Cladonia floerkeana lichen in Eifel, Germany (© Jean Claessens/Corbis)(Bing United States)

Light display on a California wind farm (© Roger Ressmeyer/Corbis/Aurora Photos)(Bing United States)

Achim Goyo (Garden of Morning Calm), Sang-myun, Gyeonggi Province, South Korea (© Panorama Stock)(Bing United States)

Wawel Castle, Kraków, Poland (© Danuta Hyniewska/age fotostock)(Bing United States)

River Avon in winter, Worcestershire, England (© nagelestock.com/Alamy)(Bing United States)

Interior of Radio City Music Hall in New York City (© Littleny/Alamy)(Bing United States)

A rare amur leopard peers over a snowy embankment (© John Conrad/Corbis)(Bing United States)

Wool, Boudhanath, Kathmandu, Nepal (© Tolo Balaguer/age fotostock)(Bing United States)

Bow Bridge in Central Park, New York City (© Chuck and Sarah Fishbein/Getty Images)(Bing United States)