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)

Masked up revellers hit the town in Sheffield, United Kingdom on October 10, 2020 before the Prime Minister introduces a three-tier lockdown system that will see hospitality venues shut in virus hotspots. (Photo by London News Pictures/The Sun)

“Jet Man” Richard Browning demonstrating Gravity, a human jet suit system, at the opening of the Army's Personnel Conference held at Farnborough International Conference Centre, Farnborough, Hampshire on Tuesday, November 2, 2021. (Photo by Steve Parsons/PA Images via Getty Images)

Nicaraguan army members carry a participant playing the role of a victim during a national multi-hazard drill organized by the National System for Prevention, Mitigation and Attention to Disasters (SINAPRED), in the 30 de Mayo neighborhood in Managua, Nicaragua, September 26, 2016. (Photo by Oswaldo Rivas/Reuters)

A member of security personnel stands on duty on an empty train platform inside a station on the Subway Line Number 1 on the eve of the Chinese Lunar New Year, in Beijing, China, February 7, 2016. According to local media, traffic in Beijing has seen a rare relief from its usual heavy pressure after 15 million people have left the city, heading for family reunions in their hometowns on the eve of the Chinese Lunar New Year of Monkey. (Photo by Jason Lee/Reuters)

A life-size replica of a Diplodocus dinosaur watches people coming out of the subway in the city center of Bochum, Germany, Monday, August 12, 2019. The exhibition, featuring models of 33 dinosaurs all around the city center, is in Bochum due to the discovery of an 316 million years old dinosaur track found in a stone pit in the city six years ago. (Photo by Martin Meissner/AP Photo)

A woman wearing a face mask as a precaution against the COVID-19 while using smartphone in a subway train in Hong Kong, Thursday, February 27, 2020. As the worst-hit areas of Asia continued to struggle with a viral epidemic, with hundreds more cases reported Thursday in South Korea and China, worries about infection and containment spread across the globe. (Photo by Kin Cheung/AP Photo)

A man carrying a woman wades through a flooded road following heavy rainfall in Zhengzhou, Henan province, July 21, 2021. At least 25 people have died in China's flood-stricken central province of Henan, a dozen of them in a subway line in its capital that was drenched by what weather officials called the heaviest rains for 1,000 years. (Photo by China Daily via Reuters)