An artist's impression of a growing supermassive black hole located in the early Universe is seen in this NASA handout illustration released on June 15, 2011. Using the deepest X-ray image ever taken, astronomers found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA's Chandra X-Ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies. (Photo by Reuters/NASA/Chandra X-Ray Observatory/A.Hobart)

A young man, who says he is part of a local criminal gang, poses for a picture holding a gun in the neighbourhood of Korogcho in Nairobi, Kenya, March 19, 2015. Around 2 million people live in the shantytowns packed in around Kenya's capital. Crime is high amid chronic unemployment levels, while basic services and sanitation are scarce. Residents try to make the best of things, eking out a living and picking up work where they can. (Photo by Siegfried Modola/Reuters)

A woman rides a women-only bus as she returns from her college in Kathmandu January 6, 2015. Nepal's capital Kathmandu has introduced women-only buses in an attempt to reduce sexual harassment and groping on public transport, a senior government official said on Monday. The initiative will start with four 16-seater buses which will ply a popular east-west route across the city during peak morning and evening hours. (Photo by Navesh Chitrakar/Reuters)

This greedy piglet was isolated from the rest of its litter by the farmer who named it Hitler after it tried to grab all the food at feeding time. (Photo by R J Lewis/Getty Images). 1942

Nguyen Manh Quan (top), 26, a civil servant, carries a girl using his throat area as he performs during a showcase of the traditional Thien Mon Dao kung fu at Du Xa Thuong village, southeast of Hanoi, Vietnam May 10, 2015. Thien Mon Dao, a traditional Vietnamese martial art, was formed by 18th century villagers in Du Xa Thuong village, who believed the art form could help improve health as well as fight against foreign invaders. There are currently about 3,000 practitioners including farmers, industry workers and state servants. These practitioners say they are able to bend metal against their bodies and carry heavy objects using their throats, eyes or tongues, as well as run across the surface of a river, according to Thien Mon Dao kung fu master Nguyen Khac Phan. (Photo by Reuters/Kham)

Britain's Prime Minister Boris Johnson gestures during a visit to Darnford Farm in Banchory near Aberdeen in Scotland on September 6, 2019. Prime Minister Boris Johnson heads to Scotland on Friday in campaign mode despite failing to call an early election after MPs this week thwarted his hardline Brexit strategy. (Photo by Andrew Milligan/Pool via AFP Photo)

Indian School children's in a traditational attire of a characters of Indian epic Ramayan, on the eve of children's day celebration at cubbon park, in Bangalore, India, 13 November 2016. Children's day (also known as Bal Divas), in India is celebrated every year on 14th of November to increase the awareness of people towards the rights, care, and education of children. Many schools hold activities and allow students to have fun and attend their classes in coloured dresses. (Photo by Jagadeesh N.V./EPA)

A girl looks at other children practicing on a boxing ring during an exercise session at a boxing school, in the Mare favela of Rio de Janeiro, Brazil, June 2, 2016. For many young residents the Luta Pela Paz (Fight For Peace) academy offers a glimpse of an alternative: a chance to build discipline and self-esteem through boxing and martial arts. (Photo by Nacho Doce/Reuters)