There are two sides to every story

Every action has two equal and opposing reactions

Expressed simply:

A + B = C

Adjustment:

C = B - A      AND/OR     C = A - B

When realised, this can be used to explain gravity and universe expansion.

We start with one expression and we get two expressions to explain the first. We get expansion. The two expressions oppose each other but attract the same result. We get recovery. When we get expansion and recovery at the same time we get gravity.

Attraction + Opposition = Expansion and Recovery (Gravity)