Cybernetics

The science of steering.

2026-11-01

What cybernetics is

Cybernetics is the study of steering. Anything that holds a course does the same four things over and over. It senses where it is, compares that to where it wants to be, acts on the difference and senses again. A thermostat does it with a room. A cook does it by tasting a sauce and adding salt. A driver does it every time they nudge the wheel back into the lane.

flowchart LR
  G([the goal]) --> C{compare}
  S[sense] --> C
  C -->|the difference| A[act]
  A --> W[the world]
  D([a push from outside]) -.-> W
  W --> S

The word comes from the Greek kybernetes, the steersman of a ship. Norbert Wiener named the field in 1948 with his book Cybernetics: Or Control and Communication in the Animal and the Machine (opens elsewhere). His point was that machines and living things steer the same way, by feedback, so one set of ideas describes both.

Feedback is what keeps a thing on course when the world pushes on it. Take a room kept at 20 degrees. After hour 4 the outside drops from 8 degrees to 0. A heater left at one setting slides toward 13, the lower line. A thermostat senses the drop, turns the heat up and brings the room back toward 20, the upper line.

xychart
  title "A room after a cold snap, degrees by the hour"
  x-axis [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
  y-axis 10 --> 22
  line [20, 20, 20, 20, 20, 18, 16.5, 15.4, 14.5, 13.9, 13.4, 13.1, 12.8]
  line [20, 20, 20, 20, 20, 18, 18.7, 19.1, 19.3, 19.5, 19.6, 19.7, 19.8]

What a cybernetician does

A cybernetician designs and tunes those loops. The work is choosing what to sense, what counts as on course and what to do about a difference, so a system corrects itself instead of drifting until somebody notices.

Where it shows up in my work

Some of what I build is a loop like this.

In Device Asset Sync, each computer checks its own record in the inventory and corrects what differs, so the inventory would stop drifting.
In the Receipt OCR Pipeline, each receipt's own arithmetic checks the reading, and a reading that fails is flagged for a person to check.
The Conversational Robot keeps listening while it talks, and stops when someone talks over it.
jev-mario (opens elsewhere) tries each move from a snapshot, measures where Mario ends up and lets Jev choose before playing on.
pianito (opens elsewhere) listens to each string, compares it to the target pitch and guides the tuner toward it.