If a ring/belt would be constructed
How would that ring behave - would it remain still, or crash against one side of the Earth?
Would it rotate with the Earth (maybe slightly slower, like the athmosphere)?
Could Earth slip out of that ring?
It would crash into the earth because the Earth's gravitational field is not uniform and, even if said ring were to be perfectly positioned, ignoring the effects of wind, strikes from cosmic debris (not a lot that low in the atmosphere), change in mass of the ring (e.g. corrosion), change in shape of the ring (due to e.g. gravitational forces, heat deformation from sunlight), etc., the Earth's gravitational field distribution changes over time and the ring would eventually fall out of its perfect position and crash into the surface.
The angular momentum of the ring would stay constant. So if the ring were built on the earth and then lifted up to 100 feet and fastened together, it would would initially rotate at the same rate at the Earth's surface. The prevailing winds would probably disturb its orbit and I suspect it would eventually crash into the Earth. I think it would take extra (carefully applied) force to avoid that fate.
