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)

Fans dressed as Darth Vader and Chewbacca take a boat trip to the Skelligs on May 4, 2018 in Portmagee, Ireland. The first ever Star Wars festival is taking place against the backdrop of the famous Skellig Michael island which was used extensively in Episode VII and Episode VIII of the popular science fiction saga. The small fishing village of Portmagee, which is closest to the location, has seen a boom in tourism following the latest films. The vilage will host a Star Wars drive-in and a Star Wars themed Irish dancing competition over the weekend. (Photo by Charles McQuillan/Getty Images)

Using digital editing, designer Anton Repponen places Manhattan buildings in desolate landscapes, “inviting viewers to see them as if for the first time”. Here: 8 Spruce Street/New York By Gehry. Photo by Anton Repponen/The Guardian)

Dancers from the Philadelphia Ballet perform for Pope Francis (R) as he attends the Festival of Families rally in Philadelphia, Pennsylvania September 26, 2015. (Photo by Brian Snyder/Reuters)

A traffic police officer directs vehicles at a street junction during sunset in Pyongyang, North Korea, Thursday, August 25, 2016. (Photo by Dita Alangkara/AP Photo)

Judy, a black collie whose owner was killed by a train when trying to retrieve her after she slipped her lead. (Photo by Evening Standard/Getty Images). 17th December 1976

Merit Prize Winner: “A Well Earned Rest in the Sahara”. This photo of Moussa Macher, our Tuareg guide, was taken at the summit of Tin-Merzouga, the largest dune (or erg) in the Tadrat region of the Sahara desert in southern Algeria. Moussa rested while waiting for us to finish our 45-minute struggle to the top. It only took ten minutes of rolling, running, and jumping to get back down. The Tadrat is part of the Tassili N'Ajjer National Park World Heritage area, famous for its red sand and engravings and rock paintings of cattle, elephants, giraffes, and rhinos that lived there when the climate was milder. Photo location: Summit of Tin-Merzouga, Tadrat, Tassili N'Ajjer National Park, Algeria. (Photo and caption by Evan Cole/National Geographic Photo Contest)

Clown/comedian/filmmaker Pierre Etaix attends The Academy Of Motion Picture Arts And Sciences' Presents “Pierre Etaix: The Laughter Returns” at AMPAS Samuel Goldwyn Theater on November 16, 2011 in Beverly Hills, California. (Photo by Valerie Macon/Getty Images)