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)

Image of the Clouds taken in August 2014 by astronauts on board the International Space Station (ISS). A year from space photographs of hurricanes, typhoons and meteorite craters show an astronauts-eye view of our planet from hundreds of miles above the earth. The illuminating images were taken by astronauts onboard the International Space Station (ISS) over the course of 2014. (Photo by NASA/SPL/Barcroft Media)

A long exposure image of embers flying off burnt out trees following the wind driven wildfire ranging in the mountain area near Rancho Cucamonga late 30 April 2014. Earlier in the day more than 1,500 homes were evacuated as the Etiwanda fire charred around 1,000 acres in San Barnardino National Forest. (Photo by Stuart Palley/EPA)

Vegetarian 19-year-old model Courtney Stodden gets ready to serve veggie hot dogs wearing a lettuce bikini during a People for the Ethical Treatment of Animals (PETA) free veggie dog handout on Capitol Hill in Washington, DC, July 16, 2014. (Photo by Jim Watson/AFP Photo)

An infrared portrait from NASA's Spitzer Space Telescope which shows generations of stars is seen in this undated NASA handout image released February 14, 2013. In this wispy star-forming region, called W5, the oldest stars can be seen as blue dots in the centers of the two hollow cavities (other blue dots are background and foreground stars not associated with the region). Red shows heated dust that pervades the region's cavities, while green highlights dense clouds. (Photo by NASA/Reuters/JPL-Caltech/Harvard-Smithsonian/Handout)

A giant sinkhole in Guatemala City, on May 31, 2010. More than 94,000 were evacuated as the storm buried homes under mud, swept away a highway bridge near Guatemala City and opened up several sinkholes in the capital. (Photo by Casa Presidencial/Reuters via The Atlantic)

In collaboration with the Pennsylvania Department of Transportation, Allegheny College art students repurpose used street signs as art materials to create the PennDOT Road Sign Sculpture Garden in Meadville, Pennsylvania, USA on August 19, 2017. (Photo by Brian Cahn/ZUMA Wire/Rex Features/Shutterstock)

A member of the wingsuit flyers duo, known as the Soul Flyers, is seen in mid-air as he catches up and flies into the open door of Pilatus Porter plane, piloted by Philippe Bouvier, after B.A.S.E. jumping off the Jungfrau mountain, 4158 meters, in Lauterbrunnen, Switzerland, October 13, 2017. French athletes Fred Fugen and Vince Reffet had 2.45 minutes and a free fall distance of 3200 meters to complete their project “Door In The Sky”, coordinated by Yves Rossy know as the “Jetman”. (Photo by Thibault Gachet/Reuters)