Alexandre Oliva

Alexandre Oliva at

humorous objection: even in interstellar space there are molecules of gas here and there; there's no abrupt boundary of the atmosphere, it's rather a progression from higher to lower density of gases.  plus, I pose that, whatever direction you choose as up, if you proceed on it long enough, you're quite likely to hit a body of hot "air", be it in the baloon or making up a distant star :-)