Originally Posted By: Orac
2.) What is the nature of the interaction between matter and gravity?

You might need to be more specific in what you are asking here. There could, for example, be a Q/A sequence that went something like this:

Q. What is the nature of the interaction between matter and gravity?
A. Mass distorts spacetime which results in what we interpret as gravity.

Q. How does mass achieve this?
A. Simply by being there.

Q. Why does this work?
A. “Why” questions take us outside science, and into philosophy.

There never was nothing.