Wedges of an orange generate enough current and electrical juice – 3.5 volts – to power an LED. The fruit’s citric acid helps electrons flow from galvanized nails to copper wire in this 14-hour exposure. This image was published in September’s Visions of Earth, a trio of photos that appear in each issue of National Geographic. (Photo by Caleb Charland/National Geographic)

White whales and their trainers present a show for visitors at Harbin Pole Aquarium on January 7, 2014 in Harbin, China. Aquarium is one of the tourist highlights of Harbin, attract domestic and foreign tourists visit each year. (Photo by Lintao Zhang/Getty Images)

These photographs appear to show a spectacular underwater world making it ideal for scuba divers – in central Europe. Twelve metres of water covers trees, footpaths, benches and bridges that are usually accessible throughout the year. Visitors to the Green Lake in Tragoess, Austria, that is normally only one metre deep, can leisurely stroll around the picturesque lagoon. Photo: A diver crossing a bridge in the flood water. (Photo by Solnet/The Grosby Group)

An American inventor has built a unique upside-down racecar – and successfully taken it on a 24-hour spin around the LeMons track. Jeff Bloch – also known as SpeedyCop – built his upside down 1999 Chevrolet Camaro by combining it with a decrepit 1990 Ford Festiva. To enter the latest LeMons race the car had to cost less than $500, which Bloch achieved by picking a Festiva model with a worn-out 1.3-litre engine and more than 300,000 kilometres on the clock.

A “scissors” dancer grabs her shoe with her mouth while performing in a national scissors dance competition in the outskirts of Lima December 1, 2013. The Danza de las tijeras, or scissors dance, is a traditional dance from the Peruvian southern region of the Andes, in which two or more performers take turns dancing while accompanied with music from a harp and a violin. Dancers would display various skills and moves, which include cutting the air with the use of a scissors. (Photo by Enrique Castro-Mendivil/Reuters)

Danny McWilliams, 56, is seen at his 36-foot-long replica of Walt Disney movie version of the Nautilus submarine from Jules Verne's “20,000 Leagues Under the Sea” at his rural home in Ellijay, Georgia, USA, 04 December 2013. (Photo by Erik S. Lesser/EPA)

The Great Dismal Swamp is a marshy area in the Coastal Plain Region of southeastern Virginia and northeastern North Carolina, between Norfolk, Virginia, and Elizabeth City, North Carolina. It is located in parts of southern Virginia cities Chesapeake and Suffolk and northern North Carolina counties Gates, Pasquotank and Camden. It is a southern swamp, one of many along the Atlantic Ocean's coast, including the Everglades and Big Cypress Swamp in Florida, the Okefenokee Swamp in Georgia, the Congaree and Four Holes swamps of South Carolina, and some of the Carolina bays in the Carolinas and Georgia. Along the eastern edge runs the Dismal Swamp Canal, completed in 1805.

“Hiding In The Shadows”. This Baby Sandhill taking refuge under Moms wings while sitting on her second egg. I witnessed this baby being born earlier that day,and the next morning saw the other one hatch,what a sight to see. Photo location: Deland, Florida. (Photo and caption by Scott Helfrich/National Geographic Photo Contest)