A DC-10 air tanker delivers flame retardant to the Blue Cut fire in Wrightwood, Calif., Wednesday, August 17, 2016. A wildfire with a ferocity never seen before by veteran California firefighters raced up and down canyon hillsides, instantly engulfing homes and forcing thousands of people to flee, some running for their lives just ahead of the flames. (Photo by Alex Gallardo/AP Photo)

Robot inventor Wu Yulu sits on a rickshaw driven by a robot which he invented in his village in rural Beijing's Tongzhou district, China, 17 November 2016. The 54-year-old Chinese farmer living in rural Beijing's Tongzhou district invented 63 robots in the past 30 years. Wu, who only received primary school education, plans to give up the agricultural work for his robot products. He regularly participates in exhibitions, transfers patent rights and teaches at the university to earn money. (Photo by Wu Hong/EPA)

Cave Diver, Anhumas Abyss, Bonito, Brazil: The Anhumas Abyss is an underground cavern with a crystal-clear lake below, more than 260 feet (79 m) deep. A visitor must enter through a narrow opening at the top of the chamber and rappel into the cave. Snorkeling and scuba diving in the lake reveal amazing scenery. Distinctive, conical limestone stalagmites and stalactites occupy the lake and the surrounding area, some reaching 65 feet (20 m) high. (Photo by Marcio Cabral/Nature’s Best Photography Awards 2017)

A performer poses during celebrations after Rahul Gandhi, newly elected president of India's main opposition Congress party, took charge as the president during a ceremony outside the party's headquarters in New Delhi, India, December 16, 2017. (Photo by Altaf Hussain/Reuters)

A young girl plays on the glass bottom platform of the Oriental Pear TV Tower as she travels with her family on the second day of the Chinese Lunar New Year holiday, also known as Spring Festival, in Shanghai, China on February 18, 2018. Some 287 million tourists travelled in China during the first four days of the week-long Chinese Lunar New Year holiday, up 11.1 percent from the same period last year, new data showed Sunday. (Photo by Imaginechina/Rex Features/Shutterstock)

Soldier boys at Fort Dix, N.J., learn something about guns during their working hours, as they show their girlfriends at a camp dance, December 13, 1940. In front row, playing with the coin amusement gun, from left: Pvt. Tom D'Amato of West Orange; Rose Sinkewicz, behind gun site, of Trenton; Julia Ivans of Trenton, and Pvt. Vernon Landers of Kearney. Back row: Pvts. William Sargent and William Corlies of Philadelphia. (Photo by AP Photo)

An Indian Hindu devotee pours milk on a snake as an offering during the annual Nag Panchami festival, dedicated to the worship of snakes outside the Nagvasuki temple, in Allahabad, on July 28, 2017. Officially the snake charmers' profession is banned in India, but many in the country offered prayers and milk blessings to cobras and other deadly serpents on July 28 in an annual tribute. The 800,000 charmers and their young apprentices come to the fore for the Nag Panchami festival which dates back several centuries. (Photo by Sanjay Kanojia/AFP Photo)

Dancers from Tokyo wearing traditional costumes perform during a celebration event, a day before Japan's Emperor Naruhito and Empress Masako's royal parade in front of the Imperial Palace in Tokyo, Japan November 9, 2019. (Photo by Issei Kato/Reuters)