London

Swedish environmental campaigner Greta Thunberg addresses politicians, media, and guests with the Houses of Parliament on April 23rd, 2019, in London, England.

Police officers remove protesters from a blockade on Waterloo Bridge during the second day of a coordinated protest by the Extinction Rebellion group on April 16th, 2019, in London, England.

A green sign demarcates London's Ultra Low Emissions Zone as the charge comes into effect on April 8th, 2019, in London, England.

A sculpture made from over 2,500 plastic bottles is seen outside the Department for Environment, Farming and Rural Affairs on February 25th, 2019, in London, England.

A series of drone sightings at London's Gatwick Airport caused over a hundred flights to be canceled or delayed as authorities struggled to respond to the potential danger.

Defending world champion Magnus Carlsen, a Norwegian, plays opponent American Fabiano Caruana in the final game of the World Chess Championship on November 28th, 2018, in London, England.

On November 7th, 2018, a police officer lets a member of the public out of a crime scene near "Billy Fury Way," where a teenager was stabbed the previous evening in London, England.

Pro-Brexit demonstrators gather outside Downing Street calling for a hard-line withdrawal from the European Union during the weekly cabinet meeting at Downing Street on October 16th, 2018, in London, England.

Police officers look on as Greenpeace activists hang from ropes after unfurling a banner outside the German embassy in a protest against coal on October 8th, 2018, in London, England.

According to researchers, air pollution kills thousands in the city every year.

It's going to cost the city around $2 billion to increase the capacity of the four "Deep Tube" lines by 10 trains an hour.

A man bangs a drum as anti-Brexit demonstrators gather outside the Houses of Parliament on June 11th, 2018, in London, England.

Major Peter Norton GC grips a program in his prosthetic hand as he waits to greet Prince Charles, Prince of Wales (not seen) at the door as he attends the bi-annual service of the Victoria Cross and George Cross Association.

In this photo illustration of the litecoin, ripple and ethereum cryptocurrency "altcoins" sit arranged for a photograph beside a smartphone displaying the current price chart for ethereum on April 25th, 2018, in London, England.

Circus artists perform on Westminster Bridge to mark the 250th anniversary of the modern-day circus ahead of a reception in the Houses of Parliament on March 6th, 2018, in London, England.

Thousands of protesters march during the March4Women event on March 4th, 2018, in London, England.

A supermoon rises behind St. Paul's Cathedral and skyscrapers on January 31st, 2018, in London, United Kingdom.

Pro-European Union, anti-Brexit demonstrators hold Union and E.U. flags outside the Houses of Parliament in London on December 21st, 2017.

Over the past few decades, some ex-convicts have turned to academia, aiming to put their experience "inside" to good use.

People light candles as they observe a vigil outside Notting hill Methodist Church following the blaze at Grenfell Tower.

Blaming multiculturalism for tragedies like London and Manchester overlooks Europe's colonial history of terrorism.

A traffic model incorporating subway and street traffic suggests faster trains aren't always good for congestion.

Jobs, the real estate market, and social mobility are all major factors in modern gentrification, but food can play a significant role as well.

We canvassed the world of the social and behavioral sciences, looking for rising stars whose careers promise to make a lasting mark. We'll be profiling the top 30 throughout the month of April.