From the medicine wheel to the building blocks of DNA, the number four has represented structure and stability. But four is also a troublemaker: a portal to realms like the fourth dimension. Our series, The Greatest Numbers of All Time explores how the number four helps us understand the world — both by making the rules, and by breaking them.

More in the series:

Listen to The Curse of 13

Listen to 12 is Sublime

Listen to 27 Club Lore

Listen to The 33,000 Horsepower Gamechanger

Guests in this episode:

Joyce Perreault is an Ojibway Anishinaabe children's book author and elementary school teacher at Donald Ahmo School in Crane River, MB.

Brian Katz is a composer, instrumentalist, improviser, and guitar instructor at University of Toronto and York University.

Lauren Fink is a professor of cognitive neuroscience at McMaster University.

Alex Fisher is a professor of musicology and area coordinator for early music at the University of British Columbia.

Tyrone Ghaswala is an assistant professor teaching stream with the Centre for Education and Computing (CEMC) and an adjunct professor in the Pure Mathematics department at the University of Waterloo.

Wenran Jiang is the founding director of the China Institute at the University of Alberta.

Stephan Reuter is an associate professor for plasma physics and spectroscopy at the Engineering Physics Department of Polytechnique Montréal

Sarah Hart is professor emerita of mathematics at Birkbeck College and author of "Once Upon a Prime: The Wondrous Connections between Mathematics and Literature."