TIL radiosondes are launched by balloon twice each day around the world, at the exact same time, to track the jet stream. When they come down, if you find one, you can keep it.

https://www.weather.gov/upperair/
#til #todayilearned
https://www.reddit.com/r/todayilearned/comments/1gqvj7s/til_radiosondes_are_launched_by_balloon_twice/