From a Cal-Tech entrance exam ...
Picture a gas filled balloon suspended in midair inside a constant velocity moving train boxcar. When the train slows down, will the ballon move forward or backward?
Picture a gas filled balloon suspended in midair inside a constant velocity moving train boxcar. When the train slows down, will the ballon move forward or backward?
What the heck are you talking about? The original statement you objected to talked about the weights of gases relative to rock and water, not other gases.
Incidentally, I would expect that the mass of the rubber in the balloon and the string would tend to make the balloon move forward due to its inertia.