Okay, in seriousness.
This is how it works.
(and I'm sorry if I stole any ideas, because I didn't read most of the theories as my thinker box hurts)
You know how there seems to be a bottomless hole when the ground gets uprooted? like in Under Watch, you just fall?
From the Silver Sacks, in Limbo, you see the beam shooting up at the sky. The beam is actually coming from that bottomless pit, going up through the sacks, and out into the sky.
Which makes sense, the beam is shooting up at the sky creating a shield all around the world in the sky.
The Shield is there to keep the Angels out and away.
So, in order
Heaven
Earth (Limbo)
And the bottomless pit which is Hell.
That's why the silver sacks is shooting up at the sky, Limbo seems like it's floating, and you seem to fall forever.
The reason the ground is uprooting most of the time isn't because they want to kill Dante, they want to make him fall into Hell, and trap him there where he can't escape.
As for physics on how it works? Crap I don't know, Bob the builder maybe.