art – David Richeson: Division by Zero

Constructing a Large 251-Point String Art Cardioid

I recently designed and made a string art cardioid sculpture, which is now hanging in our mathematics department’s window. It is made from laser-cut plywood and yarn. I wrote a “how-to” guide that includes templates for the laser-cut pieces. You can find the PDF document here. Enjoy!

Make a “Magic Eye” image using Excel

I’ve been on a weird kick lately making images using Excel. [Here’s one post. I hope to post more soon.] If you add a background color to each cell in a spreadsheet and resize the cell widths to make each one square, then you can zoom out so that each cell acts like a pixel…

Making the Mandelbrot Set with Excel

The Mandelbrot set is one of the most stunning geometric objects in all of mathematics. In this blog post, I will show how to generate the Mandelbrot set below using Excel. It is also an example of how you can use AI (I used ChatGPT) to help with a task like this. (Here is the…

Folding a Cardioid

It is well known that we can make a cardioid by drawing straight lines inside a circle. Simply choose one point on the circle’s boundary to be the base point. Then, connect points on the circle to the points twice as far away from the base point (measured along the circumference). If there are n…

Drawing a Celtic Knot

I decided to put together some activities for a gathering of math and computer science majors—puzzles, math crafts, etc. One of them was to draw a Celtic knot. I decided to write up a handout with the instructions. I thought I’d post it here. Enjoy! Here’s a printable pdf of the handout and the diamond-shaped…

A Geometry Theorem Looking for a Geometric Proof

[Update: Dan Lawson has proved the theorem without trigonometry. Thanks, Dan!] I spent a good chunk of last week reading about David Johnson Leisk (1906–1975), who is better known by his nom-de-plum Crockett Johnson. Johnson is most well known as the author of Harold and the Purple Crayon, a children’s book from 1955, and its sequels. Johnson was also the…

Mathematical art by Kevin Van Aelst

I just stumbled upon the website of the artist Kevin Van Aelst. His photographs are scenes constructed from food and drink that take the form of mathematical and scientific images. Here are some of the mathematical pictures on his artwork page: A Cantor set made out of fried eggs Logarithmic spiral made out of crumbs…