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)

Sheriffs' deputies look at wreckage from the crash of Virgin Galactic's SpaceShipTwo near Cantil, California November 2, 2014. A suborbital passenger spaceship being developed by Richard Branson's Virgin Galactic company crashed during a test flight on Friday at the Mojave Air and Space Port in California, killing one crew member and seriously injuring the other, officials said. (Photo by David McNew/Reuters)

This handout picture taken and released by the Borneo Orangutan Survival Foundation (BOSF) on October 26, 2015 shows baby orangutans, which had previously suffered from respiratory problems, playing at a nursery in the rehabilitation centre operated by the BOSF on the outskirts of Palangkaraya in Central Kalimantan. Endangered orangutans are falling victim to a devastating haze crisis that has left them sick, malnourished and severely traumatised as fires rage through Indonesia's forests, reducing their habitat to a charred wasteland. (Photo by AFP Photo/Borneo Orangutan Survival Foundation/Indrayana)

A Great White Pelicans eats fish in the Mishmar HaSharon reservoir, Israel, Wednesday, November 4, 2015. Thousands of Pelicans stop in the reservoir for food provided by the Israeli nature reserves authority as they make their way to Africa. (Photo by Ariel Schalit/AP Photo)

“YagYang”. The Apatani are tribal people living in north east of India in the region of Arunachal Pradesh. Tattooing and stuffing of large nose plugs is the particularity of these women. YagYang 75 years old, her husband passed away few months ago and she feels very alone, during my visit I was very fond of this woman and I wanted to spend some more time with her, so I asked her which was her favorite dish. The next day i returned with the fresh fish, as she mentioned, and when she saw me she was very happy and welcomed me with a big smile. Photo location: India. (Photo and caption by Passarini Mattia/National Geographic Photo Contest)

Meet the real beach babes: the herd of pigs that live a life of luxury paddling in the crystal clear waters of the Bahamas, on August 28, 2013. (Photo by Caters News)

The new EVR system which allows the recording of television programmes which can then be watched at the owner's discretion. The new Teleplayer has been produced in partnership with Rank Bush Murphy Ltd and EVR and has enormous potential. 21st September 1970. (Photo by Central Press/Getty Images)

Revellers attend the 25th edition of the Sziget Festival on August 9, 2017 in Budapest, Hungary. The Sziget Festival, one of the largest music and cultural festivals in Europe, celebrates its 25th anniversary in 2017, taking place from August 9-16 on the Hajogyari Sziget in Budapest. (Photo by Laszlo Mudra/Rockstar Photographers)