Sailing stone at Racetrack Playa in Death Valley National Park, California (© Patrick Walsh/Getty Images)

Hollow Tree on Maits Rest Rainforest Walk, Great Otway National Park, Victoria (© Jamie Lamb - elusive-images.co.uk/Getty Images)

Isola Bella, Lake Maggiore, Piedmont, Italy (© Massimo Ripani/eStock Photo)

White-tailed doe and fawn in Wisconsin (© Karel Bock/Shutterstock)

Oyster farm offshore from Notojima Island, Ishikawa Prefecture, Japan (© divedog/Shutterstock)

Former lifeguard station on the island of Rügen, Mecklenburg-Western Pomerania, Germany (© DR pics/Shutterstock)

Young humpback whale giving its mother a hug off the coast of Tonga (© Biosphoto/Alamy)

Young humpback whale giving its mother a hug off the coast of the Tongan archipelago (© Biosphoto/Alamy)

Lassen Peak in Lassen Volcanic National Park, California, USA (© Engel Ching/Shutterstock)

Lion cubs hiding in tall grass in the Kalahari Desert of Botswana (© Jami Tarris/Getty Images)

Bioluminescent sea fireflies along the shore of Okayama, Japan (© tdub_video/Getty Images)

Fossil skeleton of Tyrannosaurus rex (© Corbin17/Alamy)

Window arch at Loch Ard Gorge at dawn, Port Campbell National Park, Victoria (© David Noton/Minden Pictures)

The whirlpool in Myllykoski scenic area at winter in Oulanka National Park, Kuusamo, Finland (© Lassi Rautiainen/Minden Pictures)

Caves and coastal features at low tide on the Bay of Fundy, near St. Martins, New Brunswick, Canada (© Jamie Roach/Shutterstock)

An adult burrowing owl emerges from its burrow at sunset in Davis, California, USA (© Neil Losin/Tandem Stills + Motion)

Borobudur in Central Java, Indonesia (© Oleh Slobodeniuk/Getty Images)

Enlighten Canberra Festival 2012 at Questacon - National Science and Technology Centre, ACT (© Photoholgic/shutterstock)

A group of curious Emperor penguins in Antarctica (© Mint Images Limited/Alamy)

The Highlands of Iceland (© Kevin Krautgartner/Offset by Shutterstock)

Multicoloured lobster buoys, Acadia National Park, Maine, USA (© Cheri Alguire/Shutterstock)

Panorama of the Schrecksee, a lake in Bavaria, Germany (© wingmar/E+/Getty Images)

Stars reflecting in Totensee, a mountain lake at Grimsel Pass, Kanton Bern, Switzerland (© magodevita/Getty Images)

Stars reflecting in Totensee, a mountain lake at Grimsel Pass, Kanton Bern, Switzerland (© magodevita/Getty Images)

Mt Wellington observation deck with views of Hobart city, Tasmania (© Tommy Atthi/Getty Images)

Mt Wellington observation deck with views of Hobart city, Tasmania (© Tommy Atthi/Getty Images)

Château d'If in Marseille, France (© Boris Stroujko/Shutterstock)

Bicycle sculptures at the Col d'Aubisque, Hautes Pyrenees, France (© Fco. Javier Sobrino/age fotostock)

Hay bales in a field in Jutland, Denmark (© Nick Brundle Photography/Getty Images)

Oyster mushrooms in Belgium (© Philippe Clement/Minden Pictures)

Wildflowers in the southern region of Flinders Ranges National Park, South Australia (© Southern Lightscapes-Australia/Getty Images)