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)

Participants hang from ropes as they learn how to use safety gears at an experience centre for construction safety training in Beijing, September 5, 2014. The centre which opened in June 2014 was established to educate workers about construction safety. According to the centre, about 1,000 construction workers undergo 3-hour classes which comprises of 33 modules every month. (Photo by Kim Kyung-Hoon/Reuters)

Flashmob: Water Battle on All-Russian Exhibition Center in Moscow, Russia, on August 5, 2012. (Photo by Lilja Dal)

“On Friday, after something of a show trial, three young women in a Russian punk band were found guilty and sentenced to two years in prison for an anti-Vladimir Putin protest in a Moscow cathedral earlier this year”. – Daniel Schwartz via CBC News

Photo: A woman wears on her chest the text “free p*ssy riot” as a demonstration by supporters of the jailed feminist punk band p*ssy Riot takes place outside the Russian Embassy on August 17, 2012 in London, England. The three women who staged an anti-Kremlin protest in a church in February, were found guilty today of hooliganism motivated by religious hatred, and could face a three-year jail sentence. Supporters are gathering in several cities around the world today as a mark of solidarity. (Photo by Dan Kitwood)

A golden pheasant is seen at Hangzhou Safari Park in Hangzhou, Zhejiang Province, China, November 13, 2016. According to local media, the pheasant gains popularity as its golden feathers resemble the hairstyle of U.S. President-elect Donald Trump. (Photo by Reuters/Stringer)

Participants of the 79th edition of the annual Christmas swimming “Coupe de Noel” jump into the Lake Geneva, in Geneva, Switzerland, Sunday, December 17, 2017. More than 2000 men and women swam the 120 meters at the traditional Christmas swimming in Geneva where the water temperature was 6 degrees. (Photo by Martial Trezzini/EPA/EFE/Rex Features/Shutterstock)

A person waits for donations at the exit from the Fred Meyer parking lot on South 19th street in Tacoma, Friday, February 8, 2019. (Photo by Peter Haley/The News Tribune via AP Photo)

People wear clothing to protect them from the heat while riding along a street in Hanoi, Vietnam, 24 April 2019. North and central Vietnam was recently affected by extreme hot weather, with the highest temperatures reaching over 40 degrees Celcius, according to the National Centre for Hydro-meteorological Forecasting. (Photo by Luong Thai Linh/EPA/EFE)