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.