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Home/Math Visualization/Julia Set Explorer

Julia Set Explorer

Pick c by clicking the embedded mini-Mandelbrot or animate c along a circle; Fatou dust vs connected sets.

Parameters c = Re + Im·i

-0.7
0.27015
180

Gallery

Measured values

Re(c)-0.70000
Im(c)0.27015
|c|0.7503
c inside M?—
max iter180

About this model

For a fixed complex parameter c, the Julia set of z ↦ z² + c is the boundary between orbits that escape to infinity and those that remain bounded (the filled Julia set / Fatou components). This explorer lets you pick c by clicking an embedded mini-Mandelbrot or animate c along a circle, switching between connected Julia sets (c inside the Mandelbrot set) and Cantor-like Fatou dust (c outside). Coloring follows escape time of the iteration z_{n+1} = z_n² + c from each pixel as initial z. The page focuses on the quadratic family only — no higher-degree maps or Newton basins — with finite iterations approximating true dynamics. Move or animate c to watch connectivity change.

Who it's for: Complex dynamics, fractal geometry, and undergrad courses linking Mandelbrot and Julia sets.

Key terms

  • Julia set
  • Filled Julia set
  • Fatou dust
  • Mandelbrot set
  • Complex quadratic map
  • Escape time

How it works

Julia set for a fixed parameter c: pixels are colored by how fast the orbit zₙ₊₁ = zₙ² + c escapes for that z₀. Picking c inside the Mandelbrot set gives a connected fractal; picking c outside gives a Cantor dust of disconnected points. Click on the small Mandelbrot map to pick c, or hit ▶ to walk c around the circle of radius 0.7885 — the Julia set morphs in real time.

Key equations

J(c) = ∂{ z₀ ∈ ℂ : supₙ|zₙ| < ∞ }, zₙ₊₁ = zₙ² + c
connected ⇔ c ∈ M (Fatou–Julia)

Frequently asked questions

When is the Julia set connected?
For z² + c, the filled Julia set is connected precisely when c lies in the Mandelbrot set (the critical orbit of 0 stays bounded). Outside, the Julia set breaks into a Cantor dust of points.
How is this different from the Mandelbrot set?
Mandelbrot varies c and always starts at z₀ = 0. A Julia image fixes one c and colors many starting z. The Mandelbrot set is the parameter map of which Julia sets are connected.
Why animate c on a circle?
A circular path in the c-plane periodically crosses the Mandelbrot boundary, so you see the Julia set morph between connected bulbs and dusty disconnected forms without manually hunting parameters.