The elusive equilibrium

The notion of balance is relevant in more than a few ways in our lives. But it is not always easy — or even possible — to establish it.

People have been using balance scales for a long time. The earliest evidence, discovered in Pakistan and Egypt, goes back at least 4000 years. Such devices were (and are) based on the idea that one can determine an unknown weight by balancing the scales with a known weight, producing equilibrium, derived from the Latin for equal and balance (libra).

Equilibrium everywhere

There is something peculiar about the state of equilibrium. We encounter it in the natural sciences: in mechanics, for example, an object that is not in motion is said to be in a state of equilibrium, because the forces that act upon it counteract each other (e.g. the gravitational force on a vehicle parked on a steep hill pulling it down is balanced by the friction of the tyres on the road). In chemistry, equilibrium exists when the reaction in one direction proceeds at the same rate as the reverse reaction, for example in a closed bottle of fizzy water, where the amount of CO2 exiting the liquid equals the amount that is reabsorbed.

We see balance in man-made objects in engineering (bicycles!) and in the aesthetics of architecture and…