Why do you think it is people get into water tanks to measure body weight, mass, etc.?
Because their scale is broke?
Ummm gravity isn’t material.
Do you think it’s bottled and sold over the counter?
Yes, your claim about metmom’s post was indeed absurd, and obviously you’re hellbent on keeping it that way too.
Displacement measures volume, not weight. A concept that is or should be taught around seventh grade. This really isn't something that can be argued. It's amusing though, to see so many freepers unable to grasp this.
As for gravity, all forces are regarded as mediated by particles. Gravity's particle is called the graviton. The exact nature of gravity has not been pinned down, but denying that it is a physical force is ludicrous.