Smog began to cloud the skies of London on this day in 1952. While that wasn't necessarily unusual, this was different: The Great Smog of London lingered over the city for five days, casting a fog so thick that you couldn't see the sun, much less 15 feet in front of you. The consequences for the hustling, bustling city were disastrous.
It began with a weather pattern. A pocket of air got stuck floating over the Thames River Valley during a particularly frigid December, creating a thick mist that draped over the whole city. When people began to burn coal to keep their homes toasty, the smoke started to mix into the fog. That, plus emissions from smokestacks, cars, and a shiny new fleet of diesel buses, ended up turning the bright-white mist into a growing, yellow-brown cloud of smog swallowing up the whole city.
Millions of residents lost the ability to move freely around the city, and not just because they couldn't see; the smog also irritated skin and made breathing much more difficult. Over 4,000 people died as a result, prompting massive reforms in air pollution regulations that have led to mostly smog-free skies.
You can read more about the Great Smog of London at History.com.
