How to 'gravitize' an object/camera to another sphere...

This is my first post and I hear you guys are legends with support.

I've recently downloaded Unity and spent a couple of days reading/watching tutorials but would love it if someone could help me with a specific scene I need to create for a game I'd like to make.

Imagine a solid world (a sphere with terrain etc) Now put that world inside a second (invisible) tracking sphere (bubble). I want to be able to travel around this invisible sphere in a hover-pod-like vehicle which has a 'glass' floor. So I need the vehicle to 'stick' to the outside of the invisible tracking sphere as if by gravity so I can drive around and explore the world from above. I'll need to create a view through the floor of the vehicle that allows me to observe the world as I drive around the invisible tracking sphere. Ideally, I need to be able to manoeuvre/slide around the sphere in any direction (unlike a car which only has forward and reverse axis',) including sideways and diagonally, fluidly and accurately, as if I was in a hovercraft on a slightly slippery surface. I'm assuming I attach a camera to a controller then link it to the outer sphere somehow?

My main concern is getting the vehicle/camera to stick to the tracking sphere as if by gravity and for the solid inner world sphere to remain stationary as I orbit around it in my pod.

Gravity... I tried dropping an apple on my head... but the worm didn't appreciate it.

Any takers? Please take pity. ;-)