---
tag: 9WKCZGG906
kind: concept
name: Strange attractor
msc: [37D45, 37C70, 34C28]
specializes: [7FWX24X5MW]
sources:
  - url: https://en.wikipedia.org/wiki/Attractor
    locator: Strange attractor
---

## Summary

A strange attractor is an [[attractor|7FWX24X5MW]] with a fractal structure, unlike a point, a closed curve or a smooth surface.
The term was introduced by Ruelle and Takens in their 1971 work on turbulence.
Strange attractors usually carry chaotic dynamics: nearby orbits on the attractor separate exponentially fast, which is the [[butterfly effect|G0ZT1SDQGS]].
The [[Lorenz system|WYRC41CQN9]] and the Hénon map are the classical examples.

## Explanations

### L1 human

A strange attractor is the shape that the long-time motion of a chaotic system traces out.
Orbits are pulled onto it, yet on it they never settle into a rest point or a repeating loop.
The set is built by stretching and folding again and again, which gives it layers inside layers, like a puff pastry.
Its dimension, measured as for fractals, is often not a whole number: the Lorenz attractor is a little thicker than a surface but much thinner than a solid.