## Letters to the Editor: Lessons Learned by an Unpaid TV Math Consultant

**July 6, 2006**

*To the Editor:*

For those of you who are interested in the TV show NUMB3RS as a way of promoting mathematics, I'd like to add a few comments to Martin Golubitsky's recent article ("Partners in Crime: Math and Prime-Time TV," *SIAM News*, April 2006; http://www.siam.org/news/news.php?id=926).

In January 2005, when the show debuted, I was a member of a math department committee at Northeastern trying to find ways to increase the number of math majors. My wife (also a mathematician) watched the first episode and suggested that a mathematical commentary on the show might be a good idea. After viewing the next episode, I agreed. The university set me up with a site, http://www.atsweb.neu.edu/math/cp/blog/. This was the beginning of a stimulating and enjoyable collaboration with the show.

After watching and taping each episode, my wife and I pick out the most interesting mathematical topics referred to, and then I write essays explaining them, in terms a general viewer with an interest in math---and at least a high school background---can understand. To date, I've posted more than a hundred of these essays, on subjects ranging from exponential functions and gas diffusion to RSA coding, from cellular automata and the Mandelbrot set to quantum entanglement and Bell's theorem, from vector fields to Poisson distributions.

One of the most interesting blogs, from my perspective, concerned keyless car entry systems. The NUMB3RS episode involved the death of a woman who was found with no identification save her car door remote. Charlie, the show's mathematician, briefly described the difficulty of designing these devices: They all work on the same frequency, but each must open a unique car; for security reasons, they can't repeat any digital code they send out. As Charlie said: "It's a totally math-based technology."

In my initial blog on the subject, I described how modular pseudo-random-number generators work (with some simplified examples), with a casual mention that "the controller companies don't make these algorithms public, for obvious reasons." Oooops. Several days later I received an e-mail message from Phil Koopman, one of the co-inventors of the Lear system (used by GM and others), describing some of the engineering problems involved in its creation (e.g., lack of computing power of the tiny processors), how they were solved (feedback loop shift registers), and the URL for his patent. I was excited to hear from him, and immediately posted his letter on the blog! Lesson 1: There's almost always someone who knows a whole heck of a lot more about something than you do. Lesson 2: If your coding algorithm is good enough, making its workings public won't compromise its security.

Another episode centered on face-recognition techniques. Image processing was something that I had studied and used, but I had to read several research papers to get up to speed. It was a real challenge to translate "eigenfaces" and "3D reconstruction" into relatively non-technical terms, so I was much cheered when several experts wrote to say that I got it about right. On the other hand, I had been mightily panned a few weeks earlier for my statement that GPS satellites were geosynchronous (as Charlie had declared on the show): They're not. Oooops. Lesson 3: Win a few, lose a few.

In the past year, the site has had about 45,000 distinct hits, and I've received about a hundred e-mail messages. The curious thing is that most of the notes have come from hobbyists, engineers, kids, and their parents; as far as I can tell, no academics have written to me. I don't know if this is because of the nature of the show's audience, or simply that so few academic mathematicians know about the blog.

After I had been writing the blog for a few months, the producers of the show somehow found out about it and invited me to be a mathematical consultant: unpaid (the story of my life!), but with advance access to the scripts. Since that time I have read, studied, and critiqued all of the episodes. My charge is limited to the mathematics, but I also make comments on how Charlie is portrayed as a person. In one episode, for in-stance, Charlie spends a lot of time puzzling over how firefighters at an arson scene could measure satisfactory water pressure, yet receive only a dribble of water when they turn on their hoses. I pointed out that anyone with Charlie's background would understand Pascal's principle (which the script had not mentioned) and the independence of volume and pressure for water. The writers fixed this problem. They also eliminated a silly pop-reference to Gödel's theorem after I complained. I find mathematicians to be pretty aware of grammar, and I was able to get the writers to tighten up Charlie's language. On the other hand, they did leave in completely spurious references to Euler's Seven Bridges of Königsberg problem, and a silly application of Steiner points in locating a fugitive. Win a few, lose a few.

NUMB3RS is not a perfect show, but its heart is in the right place. It's also very concerned with the life of the mind, as opposed to the mindless violence and car chases that are central to a lot of TV crime fare. The show will never be a vehicle for math teaching---that's my intention with the blog---but it can be a very valuable math awareness and appreciation tool. We should support it as much as we can.

Finally, I welcome your help. As I learned in Lesson 1, there's always someone who knows more. So, if you see an episode with applied math in your area of expertise ("wheelhouse," as they say in baseball), drop me a line. I'd be glad to arrange a "guest blog," or at least acknowledge your comments. Or just chat about math and the show.---*Mark Bridger, Department of Mathematics, Northeastern University; *bridger@neu.edu.