Witness the physics and chemistry lesson of Life.

He, an irresistible force, meets she, an immovable object.

They alternately tug and push at each other like magnets on a taut string.

Attracting, repelling, fighting, forgiving.

Locked in an endless battle older than time, stronger than gravity.

Elements that must act in concert, always bound, eternally paired.

On occasions, he's resistible, but only to her.

On even rarer occasions, she's movable but not in his direction.

One of them has to change for this to work.