In the German town of Aix-la-Chapelle, people begin jumping, twirling, twitching, and hallucinating, all of it seemingly out of their control to stop, and some “dance” until they drop. The so-called “dancing plague” will spread to other cities and later be blamed on mass hysteria or bacterial infections.

Pilot Kenneth Arnold sees what he says are nine shiny objects flying in a 5-mile formation in the clear afternoon sky above Washington State. He later calculates their speed at 1,200 miles-per-hour, describing them as “saucer-shaped” to journalists reporting on the first major UFO sighting of modern times.

After 11 hours and 5 minutes played over three days, American John Isner defeats Frenchman Nicolas Mahut in a first-round singles match at Wimbledon. The contest sets records for longest match in professional tennis history for both time and number of games (183).