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)

Locals watch from the beach as waves hit an Indonesian tanker that ran aground near Narathiwat in southern Thailand December 19, 2014. The tanker loaded with palm oil, previously hijacked by its crew members and then seized by Thai authorities, was anchored some 400 meters from the beach but strong wind and waves broke it free, according to local media. (Photo by Surapan Boonthanom/Reuters)

A man takes a picture of sea spray as storms hit Cape Town, South Africa, June 7, 2017. (Photo by Mike Hutchings/Reuters)

A zoo performer smiles as he puts his head between the jaws of a crocodile during a performance for tourists at the Sriracha Tiger Zoo, in Chonburi province, east of Bangkok,Thailand, June 7, 2016. (Photo by Chaiwat Subprasom/Reuters)

Rescue workers try to help a driver out of his car, after the vehicle was stuck over an alley in Wenzhou, Zhejiang province, August 4, 2014. The car rolled off the edge of a road after the driver was late to brake, according to local media. (Photo by Reuters/Stringer)

“Himalayan Dog”. This dog just appeared out of nowhere and followed us for an entire week during our trekking trip in the Himalayan outback. He always used to sleep in front of our tent and guarded us in the nights. When I decided to get up at 4 a.m. to climb the next 5000 m peak for sunrise he accompanied me as well. On the top he was sitting for the entire 30 minutes on this place looking straight into the countryside. Photo location: Ladakh, India. (Photo and caption by Sebastian Wahlhuetter/National Geographic Photo Contest)

“Lofoten Glow”. I was desperately searching a good sunrise spot this particular morning. Normally Storvatnet Lake is completely covered in snow, so you can only imagine my surprise when I saw these crazy ice formations almost being shot out of the frozen lake. I put my crampons on and took a big risk walking out. I could hear the ice cracking underneath my feet, and when you’re all alone in a fjord/canyon like this – the cracks are echoed and sound really frightening. Was it worth it? I sure think so! Photo location: Storvatnet, Lofoten Islands in Northern Norway. (Photo and caption by Stian Klo/National Geographic Photo Contest)

“Are you here for the Winery Tour?” This is a Western Grey Kangaroo caught lounging in the wineries of the Adelaide Hills in South Australia. This past Autumn has been a spectacular time for wildlife viewing and I got lucky to spot this guy while mountain biking in the hills. Such a funny stance it just begs the question... Have you been drinking? ...and or... Are you here for the Winery Tour? Such a spontaneous moment I figured it would be perfect for an entry. I hope you like it! Cheers. Photo location: Adelaide Hills, South Australia, Australia. (Photo and caption by Greg Snell/National Geographic Photo Contest)