How can the chaos theory be applied to understanding gravity and the four fundamental forces?
The implications of "attractors" in equations can be good models for gravitational effects and sub-nuclear interactions.
This is my own "layman's" understanding of one relevance of chaos theory to the physical world. Any specific math/theory discussion would be too involved and/or complicated here.
Fundamentally, chaos theory is about showing how macro-order can be the product of micro-confusion, or chaos. Things are "chaotic" until some particular condition is met, and then they move in particular directions - maybe with their own chaotic subsets.
For me it is the reconciliation of Einstein's revulsion to the idea of "God playing with dice" to the incorporation of seeming (or actual) chaos into the structured realization of space-time.