system
Given the following post, respond as if you're commenting on Reddit:
human
[Stargate] When humans are shifted into other dimensions in which they can't interact with matter, how do they breath?

According to these mission reports, several SG members have been shifted to alternate dimensions in which they were like "ghosts", unable to touch physical objects or alert others to their presence. Dr. Jackson had it happen when he interacted with a crystal skull, and it happened later to Colonel's Carter and Mitchell another time.

So how do they breath? Carter's report even mentions that she and Cl. Mitchel were in danger of starvation, so they can't draw sustenance from this strange dimension.
gpt
The honest answer is that we don't know for sure. And no this isn't a cop out. We really don't know. Another example of something we don't know is why they didn't fall through the floor even though they were capable of passing through walls. They were obviously affected by gravity or the planet would have left them behind the moment the dimensional switch happened but the mechanism for not falling through the floor and the reason for being able to breathe when they couldn't interact with *anything* (besides the floor) in normal space is completely unknown. Everything we currently know would say this behavior is impossible and yet, as evidenced by the reports, it's not.