That line is beyond our ability to comprehend. That is we are in an apparent physical universe, we are part of that physical universe and all the tools to examine it are also part of that physical universe.

We will never objectively measure anything beyond the physical universe because by definition anything we measure will be considered part of the physical universe. A bunch of little fishies happily swimming in our watery world, forever ignorant of the airy world above.

As far as how Soul relates to mind-body, well that would depend on one's tradition/belief.

By the way, the reality we live in is fuzzy. Very fuzzy. Probabilistic. And gravity can't be quantized so we have one theory for the macro (Relativity) and another for the micro (QM).