[ODE] Can't get any lower than this . . . or can you?

[Nolan J. Darilek]

I did a few simple gravity tests today, and they didn't work as
expected, so I thought I'd ask for clarification on the gravity
system. I placed an object at the origin, assigned it a low mass, and
configured my world for earth-standard gravity . . . but my object
started falling. I'm assuming that it's doing so n the absence of a
ground to balance out the forces. Is this assumption correct, or am I
doing something wrong? Will the object continue falling until its Z
coordinate rolls over? Or am I just using signed values where I should
be using unsigned, thus placing my object high above the surface
instead of immediately atop it?