I think that the simplest assumption is that such devices work by exerting a downward force on the planet below them. The nature of that force is unknown, but it doesn’t matter, because whatever sort of force it is, the calculations would be the same.
(note that all instances of “force” in this post are lower-case)
What if you made a gravity shield? No gravitons get through. Or in some fashion they are just not affected by gravity (cuz space magic).
Just saying because if a kilometer long Star Destroyer was hovering overhead and “pushing back” I imagine that pushing would be noticeable. (probably getting too far afield for FQ)
Yeah, I was wondering about the falling chunk of metal without any anti-gravity space magic.
Then the answer is space magic. I can use physics to describe something using some other force to counteract gravity. I can’t use physics to describe something “shielding” against gravity, or “just not affected by gravity”.
Long ago I read a web article calctlating the pressure under a giant mothership. I can’t find it again, but here is something related in a book.
At least prior to the sequels, this wasn’t possible using Star Wars’ concept of force fields, which provided complete protection against kinetic strikes. Any decent sized inhabited world would also be heavily shielded against that sort of attack.