You are no doubt familiar with π Day, the celebration of this mathematical constant on March 14th. But what about other constant holidays? Mike Vitevitch, a cognitive scientist at the University of Kansas and friend of mine, recommends we start celebrating April 6th as Feigenbaum Constant Day.

Unlike π, which nearly everyone is aware of, the Feigenbaum constant is far less known. This constant—named after the mathematician Mitchell Feigenbaum—refers to a certain property of chaotic systems, the kinds of systems that Jeff Goldblum goes on about in Jurassic Park. Of course, chaos is a bit more complicated than Goldblum notes, and one of the features of many chaotic systems is that these systems exhibit certain types of behaviors as they transition to chaos. Specifically, if you take a chaotic system and tune its parameters, on the way to chaos you get period doubling—a doubling of the number of points in the system's period, or the places that the system oscillates between—before the chaos (you can see this in the above picture with the logistic map as *r *is increased). And the ratio between the values where the period doubles ends up approaching the Feigenbaum constant, approximately 4.669.

So, should we celebrate Feigenbaum Constant Day on April 6th or 7th? Due to rounding, it's probably the 7th, but feel free to celebrate both this coming Sunday and Monday as Feigenbaum Constant Day.

Top image:public domain