Two robotic legged squad support system (LS3) machines by the Defense Advanced Research Project Agency follow a technician during a demonstration at Joint Base Myer-Henderson Hall, Virginia, on September 10, 2012. (U.S. Marine Corps photo by Sgt. Mallory S. VanderSchans via The Atlantic)

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)

People gather at the site of a train derailment near Beni Suef, Egypt, Thursday, February 11, 2016 that injured dozens of people were injured as it was traveling north toward Cairo. Railroad accidents due to negligence are common in Egypt. Egyptians have long complained that the government has failed to deal with the country's chronic transport problems. (Photo by Samer Abdallah/AP Photo)

Josef Stalin's head is left in a Budapest street after a statue to the communist dictator was torn from its plinth during the Hungarian Revolution in 1956. (Photo by Robert Hofbauer/Radio Free Europe/Radio Liberty)

A boy looks inside the skull of a Tyrannosaurus Rex replica at the Egidio Feruglio Museum in Trelew, Argentina, in this May 18, 2014 file photograph. Scientists on July 28, 2015 unveiled a comprehensive analysis of the teeth of the group of carnivorous dinosaurs called theropods, which include the Tyrannosaurus Rex, detailing a unique serrated structure that let them chomp efficiently through the flesh and bones of large prey. (Photo by Maxi Jonas/Reuters)

This picture taken on February 1, 2015 shows participants competing in a tofu (beancurd) wrestling competition in Fogang county, south China's Guangdong province. Participants, mostly women, fight it out in an inflatable pool which is filled with nearly two tons of fresh milk and tofu, in a promotion to attract tourists for the upcoming Chinese Lunar New Year holiday. The upcoming Chinese lunar new year of the sheep, which will fall on February 19 this year, marks the biggest festival of the year in China as hundreds of millions of people journey across the country to celebrate the season with their families. (Photo by AFP Photo/Stringer)

The sculpture “It Takes Two to Tango” by Scottish sculptor David Mach is seen in front of the headquarters of the CMA-CGM shipping company office tower in the port of Marseille, France, March 15, 2016. (Photo by Jean-Paul Pelissier/Reuters)

Patrick Fellows #21, Allan McShane #26, Carson Edwardson #8 and Shaun Bily #23 of the Erie Otters sit on the bench during the first period of an OHL game against the Niagara IceDogs at the Meridian Centre on October 6, 2016 in St Catharines, Ontario, Canada. (Photo by Vaughn Ridley/Getty Images)