A resident looks at a parade marking the 496th anniversary of Panama City, Panama August 15, 2015. Modern-day Panama City includes the historical ruins of the original Panama Viejo settlement founded on August 15, 1519 by Spaniard Pedro Arias Davila, according to local media. (Photo by Carlos Jasso/Reuters)

A medium performs the religious dance "Narsingh Avatar" during the traditional Kartik dance festival at Patan Durbar Square in Lalitpur, Nepal November 24, 2015. Observed for eight days, the festival is the longest dance festival in Nepal, and features a mix of drama, music and dialogues introduced by King Siddhinarsingh Malla in 1637 AD. (Photo by Navesh Chitrakar/Reuters)

Mexican collector Pablo Perez, holds up a Star Wars R2-D2 toy while he displays a toy collection of Star Wars characters and items at his home in Monterrey, Mexico December 12, 2015. Perez has collected more than 3,000 toys and items from the Star Wars movie series over 10 years, local media reported. (Photo by Daniel Becerril/Reuters)

A competitor gestures as he crawls beneath barbed wire during the Tough Guy event in Perton, central England February 1, 2015. The annual event to raise cash for charity challenges thousands of international competitors in a cross country run followed by an assault course consisting of obstacles including water, fire and tunnels. (Photo by Phil Noble/Reuters)

A participant takes part in the Bristol Park and Slide project, an interactive temporary installation by artist Luke Jerram set up in Park Street in the centre of Bristol, southwest England on May 4, 2014. Over 95,000 people applied for just 360 tickets to slide on inflatable lilos down a lubricated water slide in a town centre street. (Photo by Leon Neal/AFP Photo)

People stand around a leopard with its head stuck in a vessel in Rajsamand district of Rajasthan state, India, Wednesday, September 30, 2015. The leopard's head got stuck when it attempted to drink water from the pot, according to news reports. Forest officials tranquilized the animal and sawed off the vessel later in the day. (Photo by Kabir Jethi/AP Photo)

A woman walks in front of an art installation made of artificial fruits and vegetables during the “Moscow Autumn” festival in central Moscow, September 14, 2015. (Photo by Maxim Zmeyev/Reuters)

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)