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)

A health worker administers a dose of the Sinovac COVID-19 vaccine to a worker in a local entertainment venue area where a new cluster of COVID-19 infections were found in Bangkok, Thailand, Wednesday, April 7, 2021. Officials in Thailand’s capital have ordered a two-week closure of all entertainment venues in three districts to try to limit the spread of the coronavirus from nightspots there. (Photo by Sakchai Lalit/AP Photo)

Revelers celebrate during fireworks marking the start of the New Year on Copacabana beach on January 1, 2017 in Rio de Janeiro, Brazil. (Photo by Mario Tama/Getty Images)

A DC-10 air tanker delivers flame retardant to the Blue Cut fire in Wrightwood, Calif., Wednesday, August 17, 2016. A wildfire with a ferocity never seen before by veteran California firefighters raced up and down canyon hillsides, instantly engulfing homes and forcing thousands of people to flee, some running for their lives just ahead of the flames. (Photo by Alex Gallardo/AP Photo)

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 fellow officer comes to the aid of injured patrolman C.V. Satt, who was pelted with rocks and beer bottles during a clash between police and relief demonstrators in Denver September 23, 1935. (Photo by Henry G. Eisenhand/AP Photo)

Professional dancer Sandy Lewis, from Louisiana, performs with his dance partner Marti Gasol, as they train in the street due to restrictions to do it indoor, in Barcelona on Wednesday, November 11, 2020 as Spain continue with new measures against the COVID-19. (Photo by Emilio Morenatti/AP Photo)

People take part in a gay pride parade in Warsaw, Poland, on Saturday, June 8, 2019. The Equality Parade is the largest gay pride parade in central and Eastern Europe. It brought thousands of people to the streets of Warsaw at a time when the LGBT rights movement in Poland is targeted by hate speeches and a government campaign depicting it as a threat to families and society. (Photo by Czarek Sokolowski/AP Photo)