Center of Mass

A heavy wooden domino tile lay flat near the base of the bookcase. Dense hardwood with clean, square edges. I knelt down, gripped the perimeter with both hands, and tilted the piece upright onto its narrow end. The block hovered on the fine edge of balance. One millimeter of drift would bring it down. I steadied my posture, centered the mass directly over the wood grain, and slowly pulled my hands away. It held dead vertical. Zero sway. I gave the top edge a measured tap with my knuckle and watched it pitch forward. It struck the floorboards with a sharp, resonant clack. Solid equilibrium. Base secure for the night.