Dancers at the Windmill Theatre in London, England practice a routine wearing gas masks and hard-hats with their costumes, 1940. (Photo by Hulton Archive/Getty Images)

A coil-shaped Helix Nebula showing a fine web of filamentary “bicycle-spoke” features embedded in the colorful red and blue ring of gas. At 650 light-years away, the Helix is one of the nearest planetary nebulae to Earth. A planetary nebula is the glowing gas around a dying, Sun-like star. (Photo by Reuters/NASA)

A masked man in military fatigues brings a blindfolded Irma Krat, arrested and held by pro-Russian protestors before her meeting with journalists near of occupied police station in Slaviansk, Ukraine, 21 April 2014. Pro-Russian activists are demanding broader autonomy from Kiev and closer ties to Russia. Pro-Russian activists continued occupying government, police and other administrative buildings in eastern Ukrainian cities, in defiance of an ultimatum by the Ukrainian government to lay down their weapons. Russia, the United States, the European Union and Ukraine on 17 April had agreed on steps to de-escalate the crisis in Ukraine during talks in Geneva, Switzerland. (Photo by Roman Pilipey/EPA)

Seized plastic handguns which were created using 3D printing technology are displayed at Kanagawa police station in Yokohama, south of Tokyo, in this photo taken by Kyodo May 8, 2014. Yoshimoto Imura became the first man to be arrested in Japan for illegal possession of two guns he created himself using 3D printing technology, Japanese media said on Thursday. The 27-year-old, a college employee in the city of Kawasaki, was arrested after police found video online posted by Imura claiming to have produced his own guns. Gun possession is strictly regulated in Japan. Police raided Imura's home and found five guns, two of which could fire real bullets, Japanese media said. (Photo by Reuters/Kyodo)

A woman walks past as South Korean soldiers participate in an anti-chemical and anti-terror exercise as part of the 2023 Ulchi Freedom Shield (UFS) at subway station on August 22, 2023 in Seoul, South Korea. The 11-day exercise, which features drills including the handling of chemical and biological attacks, is a regular joint exercise between U.S. and South Korean troops. (Photo by Chung Sung-Jun/Getty Images)

Jorge, an immigrant from Mexico, exits a subway station dressed as the Sesame Street character Elmo in Times Square, New York July 30, 2014. Elmo and Cookie Monster have long delighted young viewers on TV's “Sesame Street”, but the recent antics of New York street performers dressed as the beloved characters have drawn the ire of city officials and now the show's producers. Sesame Workshop, which owns the rights to Big Bird, Ernie and the assorted puppet monsters on the 45-year-old program, said on July 29, 2014 it was drafting plans to stop performers who dress up as the characters from appearing in Times Square, where they pose for photos with tourists and then demand tips. (Photo by Eduardo Munoz/Reuters)

A member of staff stands in front of a CRH high-speed train at Shanghai Hongqiao Railway Station during its test run on May 11, 2011 in Shanghai, China. After 3 years construction, from April in 2008, with total investment estimated at 220.9 billion yuan (around 32.5 billion U.S. dollars), the Beijing-Shanghai high-speed railway begins a one-month trial operation. It is expected to start operation in June this year, with the travel time between the two cities reducing to five hours from the previous 10. (Photo by ChinaFotoPress/Getty Images)

A protester is taken away by law enforcement officers during a rally held by opposition supporters on the parliamentary election day in Almaty, Kazakhstan on January 10, 2021. Dozens of activists were detained in at least three major cities, including the capital, Nur-Sultan, and Almaty, with reports of independent observers being denied access or detained at some polling stations. (Photo by Petr Trotsenko/Radio Free Europe/Radio Liberty)