(Based on a TV documentary, just saw...) The guy who invented the idea of an amplifying tube, tried various gases, but that didn't render the tube to amplify the flow of electrons(?) very effectively.
The fellows who attempted to improve his idea, finally ended up trying a vacuum inside the tube. The rest is history. Perhaps the idea behind yogic flying (and "celestial hearing"*, which is also based on aakaasha) is somewhat similar: when one realizes that ones physical body is 99,999... percent empty space, that greatly amplifies the thought of lightness? ROFLOL? * YS III ~ 42
