Yes, since Cycles (and Blender in general) uses single-precision floating point for coordinates in space, you only get something like 33,000,000 â€śplacesâ€ť in the whole universe (on each axis) where a vertex can be located. So if you try to model the Earth to scale, then try to model a teapot sitting on the surface of that enormous sphere, then you run into a problem because you can only put a vertex about every half meter in space.

So relative scale is a problem when you want to have enormous things and tiny things together, and in general it all works much better if you avoid extreme excursions from the default Blender scale. If you keep things within a km or two of the origin at the default scale then the math should all work without going pear-shaped.