Mount Holyoke College

Math 125: Explorations in Fractals and Chaos

This course is an introduction to the mathematical ideas of fractals and chaos. Like the other Explorations courses in mathematics, this course emphasizes mathematics as an art and as a way of seeing and understanding the world around us. It is intended for the average student, not for those majoring in mathematics or other hard sciences, and it does not presuppose special talent or prior strong interest in mathematics. Instead, it intends to awaken that interest by demonstrating the remarkable pervasiveness of mathematics in nature, its discipline-transcending power as a tool, and its artistic qualities.

Prerequisites: Three or four years of high-school mathematics.

This course is different from currently-published textbooks in that it covers both the mathematical aspects of fractals and chaos as well as real-world applications. (Developed by AD 1994-97)

Here are four famous images associated with the subject of fractals and chaos. One of the main goals of the course is to understand these images.


picture The Koch curve is one of the simplest fractals. It is actually the limit of an infinite process (Start with a line segment, remove the middle third, replace it by the top two sides of a triangle, remove the middle thirds of each of those four line segments, replace them by the top two sides of a triangle, etc.) It is self-similar in the sense that any piece of it looks like the whole. It has infinite length. Its fractal dimension is 1.26..., which says that it is between a curve (dimension 1) and a surface (dimension 2).

picture The Feigenbaum diagram shows the long-term behavior of iterating the simple function x2+c for various values of c. (This is the same function whose graph is a parabola!) The Feigenbaum diagram is a fractal. It and the Feigenbaum number 4.66... occur in many situations in the natural sciences. (Image from Devaney)

picture The Mandelbrot set has been called one of the most complicated images in mathematics, yet it also is generated using the function x2+c. Despite its complexity, though, it also has a fair amount of regularity, as can been seen upon close examination. There are many unanswered questions about the Mandelbrot set that are the subject of current mathematical research. (Image from Devaney)

picture The Lorenz attractor is an image of chaos. It is the trace of a point travelling in three-space around two lobes, seemingly changing sides at random. It occurs in a simple model for the weather and offers an explaination (the butterfly effect ) as to why the weather is so hard to predict. It is one of the simplest strange attractors. (Image from Stewart)