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)

Wearing traditional Belarus costumes girls jump over a bonfire as they celebrate the Ivan Kupala night, an ancient heathen holiday, held in the countryside near the town of Turov, some 260 km southwest of the capital Minsk, on July 6, 2014. People celebrate Kupala Night with bonfires that last throughout the night with some leaping over the flames as it is believed that the act of jumping over the bonfire cleanses people of illness and bad luck. (Photo by Viktor Drachev/AFP Photo)

This tiny hedgehog is in a prickly position as hes unable to grow spikes, leaving him needing round-the-clock care. The woodland critter was found with no spikes and has been taken in by a family hoping to nurse him back to health so he can be released into the wild. Named Mr Prickleless, the hedgehog was rescued by Dina Nixon and her daughter Jennifer, 25, after being taken into a rescue centre in December last year. It is not known what happened to his spikes, but Dina has vowed that if they ever do return he will be returned to the wild. But for now the hedgehog has taken shelter in a rabbit hutch in her garden. (Photo by Caters News Agency)

A pigeon rests on a wild iguana in a tree inside Seminario Park in Guayaquil, Ecuador, Thursday, April 3, 2014. Pigeons coexist with the wild iguanas at this park in the middle of the city surrounded by savannah. (Photo by Dolores Ochoa/AP Photo)

“Weapons Instructor”, 2012. It’s a well known fact that the IDF trains some of the best soldiers in the world, but at the source of every good soldier lies an exceptional instructor – and that’s where Cpl. Daniella Stepanoe steps in. She travels from base to base training everyone from paratroopers to elite special forces units in the use of their weapons. (Photo by Israel Defense Forces)

Elephant polo players in action during the King's Cup Elephant Polo event 2016 final between teams King Power (blue) and The Elephant Story, in Bangkok, Thailand, March 13, 2016. Team King Power won the annual charity event, which is now in its 14th edition. This year's edition involved 18 elephants brought from tourist trekking camps in Pattaya as well as some unemployed in Surin, and a total of 10 teams encompassing over 40 players, in this event directed at raising funds to improve the lives of elephants and elephant conservation. (Photo by Diego Azubel/EPA)

Competitors in the Big Air challenge at the Proryv-2016 festival of extreme sports in Moscow, Russia on March 27, 2016. (Photo by Xinhua/Rex Features/Shutterstock)

A roadside ice-cream vendor waits for customers at a market in New Delhi, India, April 7, 2016. The Indian economy is characterized by the existence of a vast majority of informal or unorganized labor employment. (Photo by Altaf Qadri/AP Photo)