Equilibrium is a state of balance of opposing actions that is central in virtually everything that happens, from basic physics to dance and the arts, economics and social ideologies.

Philosophers have discussed the concept for millenniums, and scientists developed sophisticated schemes for characterizing equilibrium systems because they are the simplest. But equilibrium systems are boring because a system in equilibrium does not change.

All natural systems are slightly out of equilibrium, fueled by some kind of impetus. Many are close enough that equilibrium principles can be applied as approximations, but the real workings require approaches that are more advanced.

Dynamic equilibrium refers to a steady-state system in which there is ongoing change, but in opposing directions such that the system as a whole remains in balance.

There are many examples: A lake or a bathtub is in a steady state when water flows in at the same rate as water flows out; the oxygen content of the atmosphere remains constant as long as respiration and photosynthesis remain balanced.

Homeostasis reflects a complex dynamic equilibrium that is kept in a fixed state over some time period through moderated changes.

Energy and material input is transformed to metabolism, motion and output of heat and waste.

A heating/cooling thermostat is a simple physical analog of homeostasis. The control algorithm is simple: Too cold, turn on heater. Too hot, turn on cooler.

This complex system includes not only the room, but also outside the room and all of the possible factors that can influence the temperature of the room. Yet, it has simple controls.

Nature’s systems are not so simple. They are always near equilibrium, sometimes straying further than other times but never sustaining it.

In systems of all sizes, individual events typically occur on a shorter time scale than the reaction time of the system. Bigger events cause greater perturbations and larger long-term effects. Regardless of the size of the system and its apparent order, there is always some scale at which it is chaotic and at which predictions about future states of the system are indeterminate.

From the shore, we see water in turbulent rapids. A bug in the water would see chaos, while an observer in an airplane would see a thin line and an astronaut may not be able to see the river at all.

On the small end of the scale, an atom would not “discern” a distinction between the water in the rapids and the still water in a lake.

Time is a factor as well. Water moves downstream despite the turbulent eddies, and on our time scale, the river’s path is fixed, but over geologic time the river will change its course dramatically.

On a planetary scale, we are the atoms and bugs in the rapids of a metaphorical stream and have only a limited ability to see changes in the global systems that are barely perceptible even with instruments in our human time frame.

Being very small and extremely short-lived creatures, we are unable to forecast changes in very large systems with a huge number of variables and high degree of nonlinearity, whether they be the planetary ecology, global climate, global economy, global politics or even the traffic during tomorrow’s commute.

We do the best we can with those limitations and keep getting better. The big Q is whether we are getting better fast enough.

Richard Brill is a retired professor of science at Honolulu Community College. His column runs on the first and third Fridays of the month. Email questions and comments to brill@hawaii.edu.