Amundsen-Scott South Pole Station experiences months of darkness. The sun dips below the horizon on March 21, after which follows several weeks of twilight before complete darkness results. Photo taken on June 25, 2009. (National Science Foundation/Jeremy Johnson)

Participants try to cover themselves from color powder sprayed by volunteers as they run through a “color station” during a five-kilometer color run event held in Beijing, China Saturday, June 21, 2014. (Photo by Andy Wong/AP Photo)

A man removes ice from an ice-covered car with a hammer in Postojna, Slovenia, on February 5, 2014. Cars stand entombed in a crystal-like casing near the deserted railway station in Postojna. Trees and electricity pylons lie felled in the snow by the sheer weight of ice enveloping them. (Photo by Srdjan Zivulovic/Reuters)

New York City policemen tangled with demonstrators at a subway station on the opening day of the New York World's Fair, April 22, 1964. Youths attempted to stall the train, which was headed from the city to the fairgrounds, as a form of protest on behalf of civil rights for blacks. (Photo by Charles Gorry/AP Photo)

Seehund “Bruno” looks out of his transport box before making his way to the water on the beach of the island of Juist, Germany on August 14, 2013. Four young seals were released after six weeks of recovery at a rescue station in Norden-Norddeich. (Photo by Carmen Jaspersen/AFP Photo/DPA)

In this photo taken on Thursday, July 23, 2015 migrants enter a train to Serbia at the railway station in the southern Macedonian town of Gevgelija. The country has become a major transit route for thousands of Middle Eastern and African refugees and migrants who cross over from Greece and then continue into Serbia. (Photo by Boris Grdanoski/AP Photo)

A Russian Soyuz MS space capsule stands on the ground shortly after its landing with International Space Station (ISS) crew members Kate Rubins of the U.S., Anatoly Ivanishin of Russia and Takuya Onishi of Japan, as a rescue helicopter lands nearby, outside the town of Dzhezkazgan (Zhezkazgan), Kazakhstan, October 30, 2016. (Photo by Dmitri Lovetsky/Reuters)

A model train travels past a scaled model of New York's Grand Central Station built entirely with plant parts during a media preview of the 25th annual Holiday Train Show at the New York Botanical Garden in the Bronx borough of New York City, U.S., November 14, 2016. (Photo by Mike Segar/Reuters)