>>if we could put it in a light enough structure And there's the problem. Containing a gas with pressure equivalent to the outside air requires just a membran

>>if we could put it in a light enough structure And there's the problem. Containing a gas with pressure equivalent to the outside air requires just a membrane. Storing a vacuum requires a container that can resist external pressure of ~ 14 psi. It scales very badly. This also creates an insane amount of stored energy in the stress on the shell. Here's a couple of videos of vacuum crushing steel tanker railroad cars [0] [1]. Of course that size doesn't even begin to scale up to the level of vacuum that would be required to buoyancy in the earth's atmosphere. [0] https://www.youtube.com/watch?v=VS6IckF1CM0 https://www.youtube.com/watch?v=VS6IckF1CM0 [1] https://www.youtube.com/watch?v=yBq5uapC-e0 https://www.youtube.com/watch?v=yBq5uapC-e0 I'd think the only way to do it might be to have many small hollow spheres contained in a net or something, but the trick would be for each one to be light enough to be positively buoyant...