system
Given the following post, respond as if you're commenting on Reddit:
human
A helium balloon floats because it has a lower density than air, right? So if I created a vacuum inside a balloon, and managed to keep its shape, would it also float? 

I realize the "keep its shape" is the hard (impossible?) part. I've read that helium has 1/7th the density of air, so what if I managed to reduce the amount of air in the balloon to 1/7th the normal fill while maintaining the same size?

I guess the question is: Imagine a box of incredible strength that would float away if filled with helium. If I pulled out all of the air, would it also float?
gpt
yes it would. The most difficult part is the "keeping its shape". To get something to float, it needs to have a total density < air density. So if you had a 1m^3 box that was filled with vaccum, the box itself would have to weigh <1.1 kg. You'd have roughly 10,000 kg ~~of force~~ pressing in each side, which would crush that box.  The nice thing about helium is that its lighter, but still puts that pressure. So the box would have maybe 10,000 kg/m^2 pushing in and 11,000 kg/m^2 pushing out (hence, balloons inflate..).