As a child, I assumed the helium balloons I set free from their earthly binds found their way to the Moon, where they'd join all the other relinquished balloons inside their lunar base constructed of old string and the rubbery corpses of their deflated comrades. How was I to know they actually all end up in East Kurrajong?
A story in the Daily Mail reports the rather astonishing tale of one balloon's 10,545-mile (16,970km) trip from the suburb of Alvaston in Derby, England to a tree in East Kurrajong, NSW. The balloon was discovered by a girl, identified in the article only as "Millie", who was nice enough to post it back via regular mail (with the apparent help of an adult), rather than trying her luck with the follies of global trade winds.
The balloon's owner, a six-year old by the name of Joshua Blackaby, released it along with 299 others last December as part of a school project on "geography and weather". The balloons were tagged with names and addresses, so if they did happen to land somewhere populated, they could be sent back to their origin.
A specific travel time isn't mentioned in the Daily Mail, but the letter from Millie arrived sometime in February, so we can assume it took a month or so for the balloon to make its journey, but it could easily have been shorter.
I don't suppose anyone's up for calculating the airspeed of an unladen helium balloon?