A Python’s Dance with Chaos: Simulating a Double Pendulum

J. Alcocer Tagua
3 min readSep 7, 2023

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The Chaos Representation

Chaos Theory isn’t just about pendulums and butterflies. It’s about understanding the inherent unpredictability in many systems around us. It’s a reminder that life, much like the double pendulum, is full of surprises.

And while we can’t always predict the outcome, we can appreciate the beauty in the *chaos*.

The Dance of the Double Pendulum: Where Determinism Meets Chaos

Let’s make it clear, it is chaotic but deterministic — Given the same initial conditions, you will always get the same trajectory.

The double pendulum app is not just a simulation; it’s a celebration of the delicate balance between determinism and chaos.

It’s a testament to the fact that in a world governed by laws and patterns, unpredictability is not just possible but inevitable. And that, in itself, is a beautiful chaos.

The Exponential Nature of Chaos: Predictable Unpredictability

At the heart of many chaotic systems is a simple principle: small changes can lead to exponentially larger effects. This is where the concept of a geometric series comes into play.

Just as a geometric progression can grow exponentially based on a constant multiplier, chaotic systems can exhibit exponential sensitivity to initial conditions.

Imagine a small error in the initial conditions of a system. As time progresses, this error doesn’t just add up linearly; it multiplies, much like the terms in a geometric series.

Take the weather, for instance. It’s a system governed by physical laws, making it deterministic in nature. In theory, if we knew the exact initial conditions of the atmosphere — the temperature, pressure, humidity, and a myriad of other factors — we could predict the weather with pinpoint accuracy.

Predictability in Theory

The catch? The atmosphere is so sensitive that even the tiniest change, like the flap of a butterfly’s wing, can lead to vastly different outcomes.

For complex systems like the weather, even the most advanced instruments can’t capture the initial conditions with perfect accuracy. And in a system where a minute change can lead to a tornado or a sunny day, that tiny margin of error makes all the difference.

This sensitivity to initial conditions is the essence of chaos.

Deterministic Yet Chaotic

Herein lies the beauty of Chaos Theory: systems can be both deterministic and chaotic. It’s not a contradiction.

Given the same initial conditions, a system will always produce the same outcome. The challenge is that, in practice, we can never know these conditions with absolute precision.

It’s like trying to measure the coastline of Britain; the closer you look, the longer it seems.

From Theory to App: The Double Pendulum’s Dance

This dance of determinism and chaos is beautifully illustrated in the Python Double Pendulum App I created.

Set the pendulum in motion with the exact same conditions, and it will dance the same dance every time.

But change the starting point by even a hair’s breadth, and you’re in for a surprise.

Double Pendulum Simulation with Python

The best thing?

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