How to use gauss law in a space of uniform charge density?

Question

Lets say there is a uniform charge density throughout the entire space. At any point $P$, if I consider shells entered at $P$, the field at that point will be zero because according to Gauss Law, field inside a shell is zero.

But If I consider shells which are not centered at $P$, then the field is non zero. Why are the answers different?

Answer 1

There no unique solution to the problem you pose. The field inside a "uniform" charge distribution depends on what is going on far far away on the distant surface.