Oct. 16, 2009 at 6:27 PM ET
A balloon soars through Colorado skies during Thursday's drama.
Anyone familiar with the physics of lighter-than-air lift would probably have suspected that 6-year-old Falcon Heene was not inside the balloon-lofted contraption that riveted the TV-watching population for several hours on Thursday. It's better to be safe than sorry, though - even if the false alarm is followed by a nationwide round of second-guessing.
Lift is related to the weight of a gas in a given volume: If the weight of a balloon and its contents is less than the weight of the volume of air displaced by the balloon, then the balloon will rise until it reaches an equilibrium level. And if the difference is great enough, you can hang some extra weight from the balloon and still let it fly.
A series of amateur "armchair balloonists" have taken advantage of that fact to go airborne. Here are three of the most notable fliers:
With all these precedents, it wouldn't be impossible for a 6-year-old to slip into a helium-buoyed amateur craft, or for the adventure to end in tragedy. But the type of balloon that was used in Thursday's flight - apparently a plastic-film "flying saucer" - would not be the craft of choice. Experts were doubtful whether the balloon could have held enough helium to do the trick.
"Judging from the size of the balloon, it would have been very borderline if it was large enough to carry the weight of an individual or even a child," Paul Petrehn of the Balloon Federation of America told Discovery News.
Back in 2004, the Discovery Channel's "MythBusters" team determined that it would take about 3,500 party-size helium balloons to loft a typical 4-year-old girl into the air. Of course, the lift capability of a given setup depends on the weight of the apparatus being lofted (including the weight of the balloons' rubber or plastic), so one strong balloon would be more efficient than a multitude of balloons.
I think few people would suggest that the authorities shouldn't have pursued the case as vigorously as they did, or that anyone should have made light (heh, heh) of the drama as it unfolded. But if you didn't at least consider the possibility that the contraption had no one in it, perhaps you've been watching too many cartoons.
For the raw data on how much helium it takes to lift how many pounds, check out the tables on this Web page. And if you're looking for a helium-balloon experiment more fitting for 6-year-olds ... kids, try this at home.
Postcard from Austin: I missed out on most of Thursday's balloon saga because I was en route to the Science Writers 2009 meeting in Austin, Texas. To keep posted on the meeting in real time, do a Twitter search for #sciwri09. And stay tuned for updates from Austin here in the log next week.Join the Cosmic Log team by signing up as my Facebook friend or following b0yle on Twitter. And reserve your copy of my book, "The Case for Pluto," which is coming out this month.