Why does a plastic bottle that is sealed at a high altitude change it’s shape when taken to lower altitude

If the cabin air pressure is lower, there is less air for unit volume 

I was answering this as he did that but that is pretty much what i would've said

This type of galaxy is an approximately ellipsoidal shape and a smooth, nearly featureless image. they are the largest single star systems, in the universe and are built by the collisions of many smaller galaxies.

A125feet i th answe